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Master

Affiliation (Master)

  • Faculty of Veterinary Medicine　Veterinary Medicine　Basic Veterinary Sciences

Affiliation (Master)

  • Faculty of Veterinary Medicine　Veterinary Medicine　Basic Veterinary Sciences

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Profile and Settings

Profile and Settings

  • Name (Japanese)

    Otsuguro

  • Name (Kana)

    Ken-ichi

  • Name

    200901054957273972

Alternate Names

Achievement

Research Interests

  • アデノシン   プリン受容体   アストロサイト   イノシン   アドレナリン受容体   薬理学   Cell biology   Pharmacology   

Research Areas

  • Life sciences / Veterinary medicine

Research Experience

  • 2024/08 - Today Hokkaido University Research and Education Center for Brain Science
  • 2018/04 - Today Hokkaido University
  • 2009/06 - 2018/03 Hokkaido University Graduate School of Veterinary Medicine
  • 2007/04 - 2009/05 Hokkaido University Graduate School of Veterinary Medicine
  • 2006/06 - 2007/03 Queen's University of Belfast (UK)
  • 2002/06 - 2007/03 Hokkaido University Graduate School of Veterinary Medicine
  • 1999/04 - 2002/05 三共㈱ 研究員
  • 1998/04 - 1999/03 Hokkaido University
  • 1997/04 - 1998/03 Hokkaido University

Education

  • 1998/03 -   Hokkaido University  Graduate School of Veterinary Medicine
  • 1994/03 -   Hokkaido University  School of Veterinary Medicine  Veterinary Medicine

Published Papers

  • Kohei Morimoto, Shu Watanuki, Ryota Eguchi, Taisuke Kitano, Ken-ichi Otsuguro
    Frontiers in Neuroscience 17 2023/10/18 [Refereed]
     
    The relationship between neuroinflammation and mental disorders has been recognized and investigated for over 30 years. Diseases of systemic or peripheral inflammation, such as sepsis, peritonitis, and infection, are associated with increased risk of mental disorders with neuroinflammation. To elucidate the pathogenesis, systemic administration of lipopolysaccharide (LPS) in mice is often used. LPS-injected mice exhibit behavioral abnormalities with glial activation. However, these studies are unlikely to recapitulate the clinical pathophysiology of human patients, as most studies focus on the acute inflammatory response with systemic symptoms occurring within 24 h of LPS injection. In this study, we focus on the effects of LPS on behavioral abnormalities following recovery from systemic symptoms and investigate the mechanisms of pathogenesis. Several behavioral tests were performed in LPS-injected mice, and to assess neuroinflammation, the time course of the morphological change and expression of inflammatory factors in neurons, astrocytes, and microglia were investigated. At 7 days post-LPS injection, mice exhibited short-term memory impairment accompanied by the suppression of neuronal activity and increases in morphologically immature spines. Glial cells were transiently activated in the hippocampus concomitant with upregulation of the microglial phagocytosis marker CD68 3 days after injection. Here we show that transient glial cell activation in the acute response phase affects neuronal activity and behavior following recovery from systemic symptoms. These findings provide novel insights for studies using the LPS-induced inflammation model and that will contribute to the development of treatments for mental disorders of this etiology.
  • Soichiro Yamaguchi, Maho Kamino, Maho Hamamura, Ken-Ichi Otsuguro
    PloS one 18 (6) e0287249  2023 [Refereed]
     
    Transmembrane channel-like protein 1 (TMC1) is a transmembrane protein forming mechano-electrical transduction (MET) channel, which transduces mechanical stimuli into electrical signals at the top of stereocilia of hair cells in the inner ear. As an unexpected phenomenon, we found that the cytosolic N-terminal (Nt) region of heterologously-expressed mouse TMC1 (mTMC1) was localized in nuclei of a small population of the transfected HEK293 cells. This raised the possibility that the Nt region of heterologously-expressed mTMC1 was cleaved and transported into the nucleus. To confirm the cleavage, we performed western blot analyses. The results revealed that at least a fragment of the Nt region was produced from heterologously-expressed mTMC1. Site-directed mutagenesis experiments identified amino acid residues which were required to produce the fragment. The accumulation of the heterologously-expressed Nt fragment into the nuclei depended on nuclear localization signals within the Nt region. Furthermore, a structural comparison showed a similarity between the Nt region of mTMC1 and basic region leucine zipper (bZIP) transcription factors. However, transcriptome analyses using a next-generation sequencer showed that the heterologously-expression of the Nt fragment of mTMC1 hardly altered expression levels of genes. Although it is still unknown what is the precise mechanism and the physiological significance of this cleavage, these results showed that the cytosolic Nt region of heterologously-expressed mTMC1 could be cleaved in HEK293 cells. Therefore, it should be taken into account that the cleavage of Nt region might influence the functional analysis of TMC1 by the heterologous-expression system using HEK293 cells.
  • Kohei Morimoto, Mai Ouchi, Taisuke Kitano, Ryota Eguchi, Ken-Ichi Otsuguro
    European journal of pharmacology 928 175110  2022/06/20 [Refereed][Not invited]
     
    Dopamine levels in the central nervous system change under pathological conditions such as Parkinson's disease, Huntington's disease, and addiction. Under those pathological conditions, astrocytes become reactive astrocytes characterized by morphological changes and the release of inflammatory cytokines involved in pathogenesis. However, it remains unclear whether dopamine regulates astrocytic morphology and functions. Elucidating these issues will help us to understand the pathogenesis of neurodegenerative diseases caused by abnormal dopamine signaling. In this study, we investigated the effects of dopamine on IL-6 expression and process formation in rat primary cultured astrocytes and acute hippocampal slices. Dopamine increased IL-6 expression in a concentration-dependent manner, and this was accompanied by CREB phosphorylation. The effects of a low dopamine concentration (1 μM) were inhibited by a D1-like receptor antagonist, whereas the effects of a high dopamine concentration (100 μM) were inhibited by a β-antagonist and enhanced by a D2-like receptor antagonist. Furthermore, dopamine (100 μM) promoted process formation, which was inhibited by a β-antagonist and enhanced by both an α-antagonist and a D2-like receptor antagonist. In acute hippocampal slices, both a D1-like receptor agonist and β-agonist changed astrocytic morphology. Together, these results indicate that dopamine promotes IL-6 expression and process formation via D1-like receptors and β-adrenoceptors. Furthermore, bidirectional regulation exists; namely, the effects of D1-like receptors and β-adrenoceptors were negatively regulated by D2-like receptors and α2-adrenoceptors.
  • Yukari Itakura, Koshiro Tabata, Kohei Morimoto, Naoto Ito, Herman M Chambaro, Ryota Eguchi, Ken-Ichi Otsuguro, William W Hall, Yasuko Orba, Hirofumi Sawa, Michihito Sasaki
    iScience 25 (4) 104122 - 104122 2022/04/15 [Refereed]
     
    The amino acid residue at position 333 of the rabies virus (RABV) glycoprotein (G333) is a major determinant of RABV pathogenicity. Virulent RABV strains possess Arg333, whereas the attenuated strain HEP-Flury (HEP) possesses Glu333. To investigate the potential attenuation mechanism dependent on a single amino acid at G333, comparative analysis was performed between HEP and HEP333R mutant with Arg333. We examined their respective tropism for astrocytes and the subsequent immune responses in astrocytes. Virus replication and subsequent interferon (IFN) responses in astrocytes infected with HEP were increased compared with HEP333R both in vitro and in vivo. Furthermore, involvement of IFN in the avirulency of HEP was demonstrated in IFN-receptor knockout mice. These results indicate that Glu333 contributes to RABV attenuation by determining the ability of the virus to infect astrocytes and stimulate subsequent IFN responses.
  • Daigo Imoto, Izumi Yamamoto, Hirokazu Matsunaga, Toya Yonekura, Ming-Liang Lee, Kan X. Kato, Takeshi Yamasaki, Shucheng Xu, Taiga Ishimoto, Satoshi Yamagata, Ken-ichi Otsuguro, Motohiro Horiuchi, Norifumi Iijima, Kazuhiro Kimura, Chitoku Toda
    Molecular Metabolism 54 101366 - 101366 2212-8778 2021/10 [Refereed][Not invited]
     
    OBJECTIVE: The regulation of food intake is a major research area in the study of obesity, which plays a key role in the development of metabolic syndrome. Gene targeting studies have clarified the roles of hypothalamic neurons in feeding behavior, but the deletion of a gene has a long-term effect on neurophysiology. Our understanding of short-term changes such as appetite under physiological conditions is therefore still limited. METHODS: Targeted recombination in active populations (TRAP) is a newly developed method for labeling active neurons by using tamoxifen-inducible Cre recombination controlled by the promoter of activity-regulated cytoskeleton-associated protein (Arc/Arg3.1), a member of immediate early genes. Transgenic mice for TRAP were fasted overnight, re-fed with normal diet, and injected with 4-hydroxytamoxifen 1 h after the refeeding to label the active neurons. The role of labeled neurons was examined by expressing excitatory or inhibitory designer receptors exclusively activated by designer drugs (DREADDs). The labeled neurons were extracted and RNA sequencing was performed to identify genes that are specifically expressed in these neurons. RESULTS: Fasting-refeeding activated and labeled neurons in the compact part of the dorsomedial hypothalamus (DMH) that project to the paraventricular hypothalamic nucleus. Chemogenetic activation of the labeled DMH neurons decreased food intake and developed place preference, an indicator of positive valence. Chemogenetic activation or inhibition of these neurons had no influence on the whole-body glucose metabolism. The labeled DMH neurons expressed prodynorphin (pdyn), gastrin-releasing peptide (GRP), cholecystokinin (CCK), and thyrotropin-releasing hormone receptor (Trhr) genes. CONCLUSIONS: We identified a novel cell type of DMH neurons that can inhibit food intake and promote feeding-induced positive valence. Our study provides insight into the role of DMH and its molecular mechanism in the regulation of appetite and emotion.
  • Takeshi Nii, Ryota Eguchi, Ken-Ichi Otsuguro
    Neuroscience research 171 67 - 73 2021/10 [Refereed][Not invited]
     
    Hydrogen sulfide (H2S) is a well-known inhibitor of the mitochondrial electron transport chain (ETC). H2S also increases intracellular Ca2+ levels in astrocytes, which are glial cells and that supply lactate as an energy substrate to neurons. Here, we examined the relationship between H2S-induced metabolic changes and Ca2+ responses in spinal cord astrocytes. Na2S (150 μM), an H2S donor, increased the intracellular Ca2+ concentration, which was inhibited by an ETC inhibitor and an uncoupler of mitochondrial oxidative phosphorylation. Na2S also increased the accumulation of extracellular lactate. Na2S alone did not change intracellular ATP content, but decreased it when glycolysis was inhibited. The Na2S-induced Ca2+ increase and accumulation of extracellular lactate were inhibited by emetine, an inhibitor of translocon complex, which mediates Ca2+ leak from the endoplasmic reticulum (ER). Furthermore, an inhibitor of the Ca2+-sensitive NADH shuttle decreased Na2S-mediated accumulation of lactate. We conclude that inhibition of the mitochondrial ETC by H2S induces Ca2+ release from mitochondria and the ER in spinal cord astrocytes, which increases lactate production. H2S may promote glycolysis by activating the Ca2+-sensitive NADH shuttle and facilitating the supply of lactate from astrocytes to neurons.
  • Kohei Morimoto, Ryota Eguchi, Taisuke Kitano, Ken-ichi Otsuguro
    Cytokine 142 155497 - 155497 1043-4666 2021/06 [Refereed][Not invited]
  • Taisuke Kitano, Ryota Eguchi, Yuko Okamatsu-Ogura, Soichiro Yamaguchi, Ken-Ichi Otsuguro
    Journal of Pharmacological Sciences 145 (3) 228 - 240 1347-8613 2021/03 [Refereed][Not invited]
     
    Astrocytes are glial cells with numerous fine processes which are important for the functions of the central nervous system. The activation of β-adrenoceptors induces process formation of astrocytes via cyclic AMP (cAMP) signaling. However, the role of α-adrenoceptors in the astrocyte morphology has not been elucidated. Here, we examined it by using cultured astrocytes from neonatal rat spinal cords and cortices. Exposure of these cells to noradrenaline and the β-adrenoceptor agonist isoproterenol increased intracellular cAMP levels and induced the formation of processes. Noradrenaline-induced process formation was enhanced with the α1-adrenoceptor antagonist prazosin and α2-adrenoceptor antagonist atipamezole. Atipamezole also enhanced noradrenaline-induced cAMP elevation. Isoproterenol-induced process formation was not inhibited by the α1-adrenoceptor agonist phenylephrine but was inhibited by the α2-adrenoceptor agonist dexmedetomidine. Dexmedetomidine also inhibited process formation induced by the adenylate cyclase activator forskolin and the membrane-permeable cAMP analog dibutyryl-cAMP. Moreover, dexmedetomidine inhibited cAMP-independent process formation induced by adenosine or the Rho-associated kinase inhibitor Y27632. In the presence of propranolol, noradrenaline inhibited Y27632-induced process formation, which was abolished by prazosin or atipamezole. These results demonstrate that α-adrenoceptors inhibit both cAMP-dependent and -independent astrocytic process formation.
  • Masaki Mogi, Tomoyuki Furuyashiki, Kazuhiro Takuma, Ken-Ichi Otsuguro, Satoshi Tanaka, Masabumi Minami
    Nihon yakurigaku zasshi. Folia pharmacologica Japonica 156 (6) 324 - 329 2021 
    With the spread of new coronavirus infections (COVID-19), universities/colleges have transformed their educational format from conventional group education to distance learning. In order to share information on the new educational format among the members of the society, the Physiological Society of Japan and the Japanese Pharmacological Society (JPS) jointly conducted the "Emergency Joint Survey on Responses of Universities to COVID-19 and Its Impact on Physiology and Pharmacology Education". The JPS surveyed pharmacology departments/divisions at schools of pharmacy, medicine, dentistry, and veterinary medicine in 202 universities (response rate 89%) from August to September 2020. 85% of the universities changed the lecture method, and 70% changed the practical training. 30%, 30%, and 40% of the lectures were live, on-demand, and mixed (combination of live and on-demand) lectures, respectively. 25% of the practical training was live or a combination of live and on-demand lectures, and 45% was on-demand delivery. There are many problems to do online methods such as stable network environment, lack of the reality for students and difficulty of the check of their understanding. On the other hand, there are unexpected benefits in online methods such as anytime learning, an increase in questions from students and repeatable learning. More than 60% considered employing the newly introduced educational styles even after the pandemic. Students' mental health problems and disruption of daily rhythms, quality assurance of online education, and copyright issues were also concerned. Pharmacology education faces a significant turning point in introducing and improving distance learning with or post the COVID-19 pandemic.
  • Nii T, Eguchi R, Yamaguchi S, Otsuguro K
    EUROPEAN JOURNAL OF PHARMACOLOGY 891 173684 - 173684 0014-2999 2021/01 [Refereed][Not invited]
     
    Hydrogen sulfide (H2S) has a variety of physiological functions. H2S reportedly increases intracellular Ca2+ concentration ([Ca2+]i) in astrocytes. However, the precise mechanism and functional role of this increase are not known. Here, we examined the effects of H2S on [Ca2+]i in astrocytes from the rat spinal cord and whether H2S affects ATP-induced Ca2+ signaling, which is known to be involved in synaptic function. Na2S (150 μM), an H2S donor, produced a nontoxic increase in [Ca2+]i. The [Ca2+]i increase by Na2S was inhibited by Ca2+ depletion in the endoplasmic reticulum (ER) but not by removal of extracellular Ca2+, indicating that H2S releases Ca2+ from the ER. On the other hand, Na2S inhibited ATP-induced [Ca2+]i increase when Na2S clearly increased [Ca2+]i in the astrocytes, which was not suppressed by a reducing agent. In addition, Na2S had no effect on intracellular cyclic AMP (cAMP) level. These results indicate that oxidative post-translational modification of proteins and cAMP are not involved in the inhibitory effect of H2S on ATP-induced Ca2+ signaling. We conclude that H2S indirectly inhibits ATP-induced Ca2+ signaling by decreasing Ca2+ content in the ER in astrocytes. In this way, H2S may influence intercellular communication between astrocytes and neurons, thereby contributing to neuronal signaling in the nervous system.
  • Ryota Eguchi, Taisuke Kitano, Ken-ichi Otsuguro
    Purinergic Signalling 16 (4) 519 - 527 1573-9538 2020/12 [Refereed][Not invited]
  • Yamaguchi S, Hamamura M, Otsuguro K
    Int J Mol Sci 21 (18) 2020/09/04 [Refereed][Not invited]
     
    Mechanical stimuli caused by sound waves are detected by hair cells in the cochlea through the opening of mechanoelectrical transduction (MET) channels. Transmembrane channel-like protein 1 (TMC1) has been revealed to be the pore-forming component of the MET channel. The two splice variants for mouse Tmc1 (mTmc1ex1 and mTmc1ex2) were reported to be expressed in the cochlea of infant mice, though only the sequence of mTmc1ex2 had been deposited in GenBank. However, due to the presence of an upstream open reading frame (uORF) and the absence of a typical Kozak sequence in mTmc1ex2, we questioned whether mTMC1 was translated from mTmc1ex2. Therefore, in this study, we evaluated which splice variant was protein-coding mRNA. Firstly, the results of RT-PCR and cDNA cloning of mTmc1 using mRNA isolated from the cochlea of five-week-old mice suggested that more Tmc1ex1 were expressed than mTmc1ex2. Secondly, mTMC1 was translated from mTmc1ex1 but not from mTmc1ex2 in a heterologous expression system. Finally, analyses using site-directed mutagenesis revealed that the uORF and the weak Kozak sequence in mTmc1ex2 prevented the translation of mTMC1 from mTmc1ex2. These results suggest that mTmc1ex1 plays a main role in the expression of mTMC1 in the mouse cochlea, and therefore, mTmc1ex1 should be the mRNA for mTMC1 hereafter.
  • Morimoto K, Kitano T, Eguchi R, Otsuguro K
    Biochem Biophys Res Commun 528 78 - 84 2020/05/22 [Refereed][Not invited]
     
    Noradrenaline (NA) suppresses TNF-α production via β-adrenoceptors (ARs) in brain astrocytes. However, the downstream pathways from β-ARs, and the involvement of α-ARs, remains unknown. In this study, we investigated the AR-mediated regulation of TNF-α mRNA levels in cultured astrocytes from rat spinal cord. NA, the α1-agonist phenylephrine, and the β-agonist isoproterenol decreased the TNF-α mRNA level, while the α2-agonist dexmedetomidine increased it. The isoproterenol-induced TNF-α mRNA decrease was accompanied by a decrease in ERK phosphorylation. An adenylyl cyclase activator and an ERK inhibitor mimicked these effects. These results indicate that the transcriptional regulation of TNF-α by β-ARs is mediated via cAMP pathways followed by the ERK pathway inhibition. The dexmedetomidine-induced TNF-α mRNA increase was accompanied by phosphorylation of JNK and ERK, which was blocked by a JNK inhibitor. Furthermore, the LPS-induced increase in the TNF-α mRNA level was accompanied by NF-κB nuclear translocation, and both these effects were blocked by phenylephrine. An NF-κB inhibitor suppressed the LPS-induced increase in the TNF-α mRNA level. These results suggest that α1-ARs suppress the LPS-induced increase in the TNF-α mRNA level via inhibition of NF-κB nuclear translocation. Taken together, our study reveals that both α- and β-ARs are involved in the transcriptional regulation of TNF-α in astrocytes.
  • Yamaguchi S, Tanimoto A, Iwasa S, Otsuguro K
    Int J Mol Sci 20 (8) E2012  2019/04 [Refereed][Not invited]
     
    Transient receptor potential melastatin member 4 (TRPM4) and 5 (TRPM5) channels are Ca2+-activated nonselective cation channels. Intracellular Ca2+ is the most important regulator for them to open, though PI(4,5)P2, a membrane phosphoinositide, has been reported to regulate their Ca2+-sensitivities. We previously reported that negatively-charged amino acid residues near and in the TRP domain are necessary for the normal Ca2+ sensitivity of TRPM4. More recently, a cryo-electron microscopy structure of Ca2+-bound (but closed) TRPM4 was reported, proposing a Ca2+-binding site within an intracellular cavity formed by S2 and S3. Here, we examined the functional effects of mutations of the amino acid residues related to the proposed Ca2+-binding site on TRPM4 and also TRPM5 using mutagenesis and patch clamp techniques. The mutations of the amino acid residues of TRPM4 and TRPM5 reduced their Ca2+-sensitivities in a similar way. On the other hand, intracellular applications of PI(4,5)P2 recovered Ca2+-sensitivity of desensitized TRPM4, but its effect on TRPM5 was negligible. From these results, the Ca2+-binding sites of TRPM4 and TRPM5 were shown to be formed by the same amino acid residues by functional analyses, but the impact of PI(4,5)P2 on the regulation of TRPM5 seemed to be smaller than that on the regulation of TRPM4.
  • Kitano T, Kobayashi T, Yamaguchi S, Otsuguro K
    J Vet Pharmacol Ther 42 (2) 243 - 247 0140-7783 2019/03 [Refereed][Not invited]
  • Eguchi R, Yamaguchi S, Otsuguro K
    Journal of pharmacological sciences 139 (2) 98 - 104 1347-8613 2019/02 [Refereed][Not invited]
  • Ayako Ujike, Tomoki Kuraishi, Soichiro Yamaguchi, Ryota Eguchi, Taisuke Kitano, Jumpei Kamise, Shigeo Ito, Ken-ichi Otsuguro
    European Journal of Pharmacology 821 88 - 96 1879-0712 2018/02/15 [Refereed][Not invited]
     
    H2S has excitatory and inhibitory effects on Ca2+ signals via transient receptor potential ankyrin 1 (TRPA1) and ATP-sensitive K+ channels, respectively. H2S converts intracellularly to polysulfides, which are more potent agonists for TRPA1 than H2S. Under inflammatory conditions, changes in the expression and activity of these H2S target channels and/or the conversion of H2S to polysulfides may modulate H2S effects. Effects of proinflammatory cytokines on H2S-induced Ca2+ signals and polysulfide production in RIN14B cells were examined using fluorescence imaging with fura-2 and SSP4, respectively. Na2S, a H2S donor, induced 1) the inhibition of spontaneous Ca2+ signals, 2) inhibition followed by [Ca2+]i increase, and 3) rapid [Ca2+]i increase without inhibition in 50% (23/46), 22% (10/46), and 17% (8/46) of cells tested, respectively. IL-1β augmented H2S-induced [Ca2+]i increases, which were inhibited by TRPA1 and voltage-dependent L-type Ca2+ channel blockers. However, IL-1β treatment did not affect [Ca2+]i increases evoked by a TRPA1 agonist or high concentration of KCl. Na2S increased intracellular polysulfide levels, which were enhanced by IL-1β treatment. A NOS inhibitor suppressed the increased polysulfide production and [Ca2+]i increase in IL-1β-treated cells. These results suggest that IL-1β augments H2S-induced [Ca2+]i increases via the conversion of H2S to polysulfides through NO synthesis, but not via changes in the activity and expression of target channels. Polysulfides may play an important role in the effects of H2S during inflammation.
  • Masahiro Yamasaki, Nao Watanabe, Natsuki Idaka, Tohru Yamamori, Ken-ichi Otsuguro, Naohiro Uchida, Aiko Iguchi, Hiroshi Ohta, Mitsuyoshi Takiguchi
    EXPERIMENTAL PARASITOLOGY 183 92 - 98 0014-4894 2017/12 [Refereed][Not invited]
     
    The mechanism of the development of diminazene aceturate (DA) resistance in Babesia gibsoni is still unknown even though DA-resistant B. gibsoni isolate was previously developed in vitro. To clarify the mechanisms of DA-resistance in B. gibsoni, we initially examined the intracellular DA content in the DA resistant isolate using high-performance liquid chromatography, and compared it with that in the wild type. As a result, the intracellular DA content in the DA-resistant isolate was significantly lower than that in the wild-type, suggesting that the decreased DA content may contribute to DA-resistance. Additionally, the glucose consumption of the DA-resistant isolate was significantly higher than that of the wild-type, indicating that a large amount of glucose is utilized to maintain DA-resistance. It is possible that a large amount of energy is utilized to maintain the mechanisms of DA-resistance. It was reported that as the structure of DA is similar with that of adenosine, DA may be taken up by the P2 transporter, which contributes to the uptake of adenosine, in Trypanosoma brucei brucei, and that the uptake of adenosine is decreased in DA-resistant T brucei brucei. In the present study, the adenosine incorporation in the DA-resistant B. gibsoni isolate was higher than in the wild-type. Moreover, the adenosine incorporation in the wild-type was not inhibited by the presence of DA. These results suggest that adenosine transport in B. gibsoni is not affected by DA and may not mediate DA-resistance. To clarify the mechanism of the development of DA resistance in B. gibsoni, we should investigate the cause of the decreased DA content in the DA-resistant isolate in the future. (C) 2017 Elsevier Inc. All rights reserved.
  • Soichiro Yamaguchi, Ken-ichi Otsuguro
    NEUROSCIENCE LETTERS 653 139 - 145 0304-3940 2017/07 [Refereed][Not invited]
     
    Mas-related G-protein coupled receptor B4 (MrgprB4) has been reported to be expressed in the dorsal root ganglion (DRG) neurons which detect stroking of hairy skin of mice. However, the mechanisms by which the MrgprB4 positive (+) neurons respond to adequate stimulus remain unsolved as it was also reported that electrophysiological analysis of cultured MrgprB4+ neurons did not reveal responses to mechanical stimuli. Contrary to the observation, however, in this study we show that the MrgprB4+ neurons functionally express a mechanically activated channel using DRG neurons dissociated from genetically-modified mice whose MrgprB4+ neurons express a red fluorescent protein. Hypotonicity-induced cell swelling increased intracellular Ca2+ concentrations ([Ca2+](i)) of MrgprB4+ neurons. The [Ca2+](i) increases were prevented by extracellular Ca2+ removal and by applications of nonselective Piezo channel blockers. Patch clamp analysis revealed that the MrgprB4+ neurons exhibited rapidly-adapting mechanically-activated currents. The MrgprB4+ neurons were stained with anti-Piezo2 antibody. These results raise the possibility that the MrgprB4+ neurons directly detect the stroking-like stimuli of hairy skin. (C) 2017 Elsevier B.V. All rights reserved.
  • Dugar Delgermurun, Soichiro Yamaguchi, Osamu Ichii, Yasuhiro Kon, Shigeo Ito, Ken-ichi Otsuguro
    COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-TOXICOLOGY & PHARMACOLOGY 187 43 - 49 1532-0456 2016/09 [Refereed][Not invited]
     
    Epithelioid cells in the chicken thoracic aorta are chemoreceptor cells that release 5-HT in response to hypoxia. It is likely that these cells play a role in chemoreception similar to that of glomus cells in the carotid bodies of mammals. Recently, H2S was reported to be a key mediator of carotid glomus cell responses to hypoxia. The aim of the present study was to reveal the mechanism of action of H2S on 5-HT outflow from chemoreceptor cells in the chicken thoracic aorta. The 5-HT outflow induced by NaHS, an H2S donor, and Na2S3, a polysulfide, was measured by using a HPLC equipped with an electrochemical detector. NaHS (0.3-3 mM) caused a concentration-dependent increase in 5-HT outflow, which was significantly inhibited by the removal of extracellular Ca2+. outflow induced by NaHS (0.3 mM) was also significantly inhibited by voltage-dependent L- and N-type Ca2+ channel blockers and a selective TRPA1 channel blocker. Cinnamaldehyde, a TRPA1 agonist, mimicked the secretory response to H2S. 5-HT outflow induced by Na2S3 (10 M) was also inhibited by the TRPA1 channel blocker. Furthermore, the expression of TRPA1 was localized to 5-HT-containing chemoreceptor cells in the aortic wall. These findings suggest that the activation of TRPA1 and voltage-dependent Ca2+ channels is involved in H2S-evoked 5-HT release from chemoreceptor cells in the chicken aorta. (C) 2016 Elsevier Inc. All rights reserved.
  • Dugar Delgermurun, Shigeo Ito, Toshio Ohta, Soichiro Yamaguchi, Ken-ichi Otsuguro
    JOURNAL OF VETERINARY MEDICAL SCIENCE 78 (1) 71 - 76 0916-7250 2016/01 [Refereed][Not invited]
     
    Chemoreceptor cells aggregating in clusters in the chicken thoracic aorta contain 5-hydroxytryptamine (5-HT) and have voltage dependent ion channels and nicotinic acetylcholine receptors, which are characteristics typically associated with neurons. The aim of the present study was to investigate the effects of 5-HT uptake inhibitors, fluvoxamine, fluoxetine and clomipramine (CLM), and amphetamine derivatives, p-chloroamphetamine (PCA) and methamphetamine (MET), on endogenous 5-HT outflow from the isolated chick thoracic aorta in vitro. 5-HT was measured by using a HPLC system with electrochemical detection. The amphetamine derivatives and 5-HT uptake inhibitors caused concentration-dependent increases in endogenous 5-HT outflow. PCA was about ten times more effective in eliciting 5-HT outflow than MET. The 5-HT uptake inhibitors examined had similar potency for 5-HT outflow. PCA and CLM increased 5-HT outflow in a temperature-dependent manner. The outflow of 5-HT induced by PCA or 5-HT uptake inhibitors was independent of extracellular Ca2+ concentration. The 5-HT outflow induced by CLM, but not that by PCA, was dependent on the extracellular NaCl concentration. These results suggest that the 5-HT uptake system of 5-HT-containing chemoreceptor cells in the chicken thoracic aorta has characteristics similar to those of 5-HT-containing neurons in the mammalian central nervous system (CNS).
  • Ken-ichi Otsuguro, Yuki Tomonari, Saori Otsuka, Soichiro Yamaguchi, Yasuhiro Kon, Shigeo Ito
    NEUROPHARMACOLOGY 97 160 - 170 0028-3908 2015/10 [Refereed][Not invited]
     
    Adenosine kinase (AK) inhibitor is a potential candidate for controlling pain, but some AK inhibitors have problems of adverse effects such as motor impairment. ABT-702, a non-nucleoside AK inhibitor, shows analgesic effect in animal models of pain. Here, we investigated the effects of ABT-702 on synaptic transmission via nociceptive and motor reflex pathways in the isolated spinal cord of neonatal rats. The release of adenosine from the spinal cord was measured by HPLC. ABT-702 inhibited slow ventral root potentials (sVRPs) in the nociceptive pathway more potently than monosynaptic reflex potentials (MSRs) in the motor reflex pathway. The inhibitory effects of ABT-702 were mimicked by exogenously applied adenosine, blocked by 8CPT (8-cyclopentyl-1,3-dipropylxanthine), an adenosine A(1) receptor antagonist, and augmented by EHNA (erythro-9-(2-hydroxy-3-nonyl) adenine), an adenosine deaminase (ADA) inhibitor. Equilibrative nucleoside transporter (ENT) inhibitors reversed the effects of ABT-702, but not those of adenosine. ABT-702 released adenosine from the spinal cord, an effect that was also reversed by ENT inhibitors. The ABT-702-facilitated release of adenosine by way of ENTs inhibits nociceptive pathways more potently than motor reflex pathways in the spinal cord via activation of A1 receptors. This feature is expected to lead to good analgesic effects, but, caution may be required for the use of AK inhibitors in the case of ADA dysfunction or a combination with ENT inhibitors. (C) 2015 Elsevier Ltd. All rights reserved.
  • Ayako Ujike, Ken-ichi Otsuguro, Ryo Miyamoto, Soichiro Yamaguchi, Shigeo Ito
    EUROPEAN JOURNAL OF PHARMACOLOGY 764 463 - 470 0014-2999 2015/10 [Refereed][Not invited]
     
    Hydrogen sulfide (H2S) reportedly acts as a gasotransmitter because it mediates various cellular responses through several ion channels including ATP-sensitive K+ (K-ATP) channels and transient receptor potential (TRP) A1 channels. H2S can activate both K-ATP, and TRPA1 channels at a similar concentration range. In a single cell expressing both channels, however, it remains unknown what happens when both channels are simultaneously activated by H2S. In this study, we examined the effects of H2S on RIN14B cells that express both K-ATP and TRPA1 channels. RIN14B cells showed several intracellular Ca2+ concentration ([Ca2+](i)) responses to NaHS (300 mu M), an H2S donor, i.e., inhibition of spontaneous Ca2+ oscillations (37%), inhibition followed by [Ca2+](i) increase (24%), and a rapid increase in [Ca2+](i) (25%). K-ATP channel blockers, glibenclamide or tolbutamide, abolished any inhibitory effects of NaHS and enhanced NaHS-mediated [Ca2+](i) increases, which were inhibited by extracellular Ca2+ removal, HC030031 (a TRPA1 antagonist), and disulfide bond-reducing agents. NaHS induced 5-hydroxytryptamine (5-HT) release from RIN14B cells, which was also inhibited by TRPA1 antagonists. These results indicate that H2S has both inhibitory and excitatory effects by opening K-ATP and TRPA1 channels, respectively, in RIN14B cells, suggesting potential bidirectional modulation of secretory functions. (C) 2015 Elsevier B.V. All rights reserved.
  • Takeshi Kobayashi, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito
    EUROPEAN JOURNAL OF PHARMACOLOGY 761 321 - 329 0014-2999 2015/08 [Refereed][Not invited]
     
    Alpha-2A adrenergic receptor (AR) subtype plays an important role in the analgesic effect of alpha(2)-AR agonists. Here, we examined the effects of alpha(2)-AR agonists, dexmedetomidine and xylazine, on spinal synaptic transmission in newborn C57BL/6J and alpha(2A)-AR mutant mice. Spinal reflex potentials, the monosynaptic reflex potential (MSR) and the slow ventral root potential (sVRP), were measured in isolated spinal cords. The compound action potential was measured in isolated lumbar nerve. Dexmedetomidine and xylazine suppressed both the MSR and sVRP in a concentration-dependent manner. In alpha(2A)-AR mutant mice, sVRP suppression by dexmedetomidine was greatly weakened, while that by xylazine (30-100 mu M) showed only slight attenuation. A high concentration (300 mu M) of xylazine completely suppressed the sVRP, even in alpha(2A)-AR mutant mice spinal cords, and also suppressed the compound action potential. MSR suppression by these alpha(2)-AR agonists had no difference between wild-type and alpha(2A)-AR mutant mice. These results suggest that sVRP suppression by dexmerletomidine and xylazine is mainly mediated by alpha(2A)-AR. In addition, a high concentration of xylazine inhibits conduction of the action potential, which is not mediated by alpha(2A)-AR. alpha(2)-AR is not responsible for the dexmedetomidineand xylazine-mediated inhibition of the MSR. (C) 2015 Elsevier B.V. All rights reserved.
  • Ryo Miyamoto, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito
    NEUROSCIENCE RESEARCH 97 52 - 59 0168-0102 2015/08 [Refereed][Not invited]
     
    Cystathionine beta-synthase (CBS), expressed in astrocytes, generates a gaseous neuromodulator, hydrogen sulfide (H2S) in the central nervous system (CNS). However, little is known about the regulatory mechanisms of astrocytic CBS expression and activity. This study evaluated the influence of neurons on astrocytic CBS expression by employing multiple culture systems. Substantial CBS expression was observed in the intact neonatal rat spinal cord, while CBS content was markedly reduced in an astrocyte-enriched culture prepared from the neonatal spinal cord. Immunofluorescence analysis confirmed the localization of spinal cord CBS in astrocytes, but not in neurons. Although CBS expression was weak in the embryonic rat spinal cord, enzyme levels were time-dependently increased in a neuron/astrocyte mixed culture originating from embryonic spinal cord. The reduced CBS expression in isolated neonatal astrocytes was restored by co-culture with embryonic neurons. Together with the observed CBS expression levels, H2S production was relatively low in astrocytes cultured alone, but was considerably higher in astrocytes cultured with neurons. These results indicate that neurons are essential for maintaining the expression and H2S-producing activity of astrocytic CBS in the rat spinal cord. (C) 2015 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
  • Ryota Eguchi, Sanae Akao, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito
    JOURNAL OF PHARMACOLOGICAL SCIENCES 128 (1) 47 - 53 1347-8613 2015/05 [Refereed][Not invited]
     
    Extracellular adenosine is a neuromodulator in the central nervous system. Astrocytes mainly participate in adenosine production, and extracellular adenosine accumulates under physiological and pathophysiological conditions. Inhibition of intracellular adenosine metabolism and reduction of the external Ca2+ concentration ([Ca2+](e)) participate in adenosine accumulation, but the precise mechanisms remain unclear. This study investigated the mechanisms underlying extracellular adenosine accumulation in cultured rat spinal astrocytes. The combination of adenosine kinase and deaminase (ADK/ADA) inhibition and a reduced [Ca2+](e) increased the extracellular adenosine level. ADK/ADA inhibitors increased the level of extracellular adenosine but not of adenine nucleotides, which was suppressed by inhibition of equilibrative nucleoside transporter (ENT) 2. Unlike ADK/ADA inhibition, a reduced [Ca2+](e) increased the extracellular level not only of adenosine but also of ATP. This adenosine increase was enhanced by ENT2 inhibition, and suppressed by sodium polyoxotungstate (ecto-nucleoside triphosphate diphosphohydrolase inhibitor). Gap junction inhibitors suppressed the increases in adenosine and adenine nucleotide levels by reduction of [Ca2+](e). These results indicate that extracellular adenosine accumulation by ADK/ADA inhibition is due to the adenosine release via ENT2, while that by reduction of [Ca2+] e is due to breakdown of ATP released via gap junction hemichannels, after which ENT2 incorporates adenosine into the cells. (C) 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of Japanese Pharmacological Society.
  • Soichiro Yamaguchi, Akira Tanimoto, Ken-ichi Otsuguro, Hiroshi Hibino, Shigeo Ito
    JOURNAL OF BIOLOGICAL CHEMISTRY 289 (51) 35265 - 35282 0021-9258 2014/12 [Refereed][Not invited]
     
    Transient receptor potential (TRP) channel melastatin subfamily member 4 (TRPM4) is a broadly expressed nonselective monovalent cation channel. TRPM4 is activated by membrane depolarization and intracellular Ca2+, which is essential for the activation. The Ca2+ sensitivity is known to be regulated by calmodulin and membrane phosphoinositides, such as phosphatidylinositol 4,5-bisphosphate (PI(4,5)P-2). Although these regulators must play important roles in controlling TRPM4 activity, mutation analyses of the calmodulin-binding sites have suggested that Ca2+ binds to TRPM4 directly. However, the intrinsic binding sites in TRPM4 remain to be elucidated. Here, by using patch clamp and molecular biological techniques, we show that there are at least two functionally different divalent cation-binding sites, and the negatively charged amino acids near and in the TRP domain in the C-terminal tail of TRPM4 (Asp-1049 and Glu-1062 of rat TRPM4) are required for maintaining the normal Ca2+ sensitivity of one of the binding sites. Applications of Co2+, Mn2+, or Ni2+ to the cytosolic side potentiated TRPM4 currents, increased the Ca2+ sensitivity, but were unable to evoke TRPM4 currents without Ca2+. Mutations of the acidic amino acids near and in the TRP domain, which are conserved in TRPM2, TRPM5, and TRPM8, deteriorated the Ca2+ sensitivity in the presence of Co2+ or PI(4,5)P-2 but hardly affected the sensitivity to Co2+ and PI(4,5)P-2. These results suggest a novel role of the TRP domain in TRPM4 as a site responsible for maintaining the normal Ca2+ sensitivity. These findings provide more insights into the molecular mechanisms of the regulation of TRPM4 by Ca2+.
  • Ryo Miyamoto, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito
    JOURNAL OF NEUROCHEMISTRY 130 (1) 29 - 40 0022-3042 2014/07 [Refereed][Not invited]
     
    Hydrogen sulfide (H2S) is a gaseous neuromodulator produced from L-cysteine. H2S is generated by three distinct enzymatic pathways mediated by cystathionine -lyase (CSE), cystathionine -synthase (CBS), and mercaptopyruvate sulfurtransferase (MPST) coupled with cysteine aminotransferase (CAT). This study investigated the relative contributions of these three pathways to H2S production in PC12 cells (rat pheochromocytoma-derived cells) and the rat dorsal root ganglion. CBS, CAT, and MPST, but not CSE, were expressed in the cells and tissues, and appreciable amounts of H2S were produced from L-cysteine in the presence of -ketoglutarate, together with dithiothreitol. The production of H2S was inhibited by a CAT inhibitor (aminooxyacetic acid), competitive CAT substrates (L-aspartate and oxaloacetate), and RNA interference (RNAi) against MPST. Immunocytochemistry revealed a mitochondrial localization of MPST in PC12 cells and dorsal root ganglion neurons, and the amount of H2S produced by CAT/MPST at pH 8.0, a physiological mitochondrial matrix pH, was comparable to that produced by CSE and CBS in the liver and the brain, respectively. Furthermore, H2S production was markedly increased by alkalization. These results indicate that CAT and MPST are primarily responsible for H2S production in peripheral neurons, and that the regulation of mitochondrial metabolism may influence neuronal H2S generation. In the peripheral nervous system, hydrogen sulfide (H2S) has been implicated in neurogenic pain or hyperalgesia. This study provides evidence that H2S is synthesized in peripheral neurons through two mitochondrial enzymes, cysteine aminotransferase (CAT) and mercaptopyruvate sulfurtransferase (MPST). We propose that mitochondrial metabolism plays key roles in the physiology and pathophysiology of the peripheral nervous system via regulation of neuronal H2S production.
  • Takeyuki Iwasaki, Ken-ichi Otsuguro, Takeshi Kobayashi, Toshio Ohta, Shigeo Ito
    EUROPEAN JOURNAL OF PHARMACOLOGY 702 (1-3) 149 - 157 0014-2999 2013/02 [Refereed][Not invited]
     
    Serotonin (5-HT) released from descending fibers plays important roles in spinal functions such as locomotion and nociception. 5-HT2A and 5-HT3 receptors are suggested to contribute to spinal antinociception, although their activation also contributes to neuronal excitation. In the neonatal spinal cord, DL-p-chloroamphetamine (pCA), a 5-HT releaser, inhibited both A fiber-evoked monosynaptic reflex potential (MSR) and C fiber-evoked slow ventral root potential (sVRP). The pCA-mediated inhibition was reversed by ketanserin (a 5-HT2A receptor antagonist) and tropisetron (a 5-HT3 receptor antagonist). Bath-applied 5-HT also inhibited MSR and sVRP; in this case, the actions of 5-HT were antagonized by ketanserin, but not by tropisetron. The pCA-evoked inhibition of sVRP was reduced by bicuculline (a GABA(A) receptor antagonist) and strychnine (a glycine receptor antagonist). Furthermore, ketanserin inhibited the pCA-evoked release of gamma-aminobutyric acid (GABA) and glycine, while tropisetron inhibited the pCA-evoked release of 5-HT. These results suggest that 5-HT released by pCA activates 5-HT2A receptors, which in turn stimulates the release of GABA/glycine and thereby blocks the spinal nociceptive pathway. 5-HT3 receptors may be involved in the facilitation of 5-HT release via a positive feedback process. (C) 2013 Elsevier B.V. All rights reserved.
  • K. Kawamoto, K. Otsuguro, M. Ishizuka, S. Ito
    BRITISH JOURNAL OF PHARMACOLOGY 166 (2) 788 - 800 0007-1188 2012/05 [Refereed][Not invited]
     
    BACKGROUND AND PURPOSE Dopamine released from the endings of descending dopaminergic nerve fibres in the spinal cord may be involved in modulating functions such as locomotion and nociception. Here, we examined the effects of dopamine on spinal synaptic transmissions in rats. EXPERIMENTAL APPROACH Spinal reflex potentials, monosynaptic reflex potential (MSR) and slow ventral root potential (sVRP), were measured in the isolated spinal cord of the neonatal rat. Dopamine release was measured by HPLC. KEY RESULTS Dopamine at lower concentrations (< 1 mu M) depressed sVRP, which is a C fibre-evoked polysynaptic response and believed to reflect nociceptive transmission. At higher concentrations (> 1 mu M), in addition to a potent sVRP depression, dopamine depolarized baseline potential and slightly depressed MSR. Depression of sVRP by dopamine was partially reversed by dopamine D-1-like but not by D-2-like receptor antagonists. SKF83959 and SKF81297, D-1-like receptor agonists, and methamphetamine, an endogenous dopamine releaser, also caused the inhibition of sVRP. Methamphetamine also depressed MSR, which was inhibited by ketanserin, a 5-HT2A/2C receptor antagonist. Methamphetamine induced the release of dopamine and 5-HT from spinal cords, indicating that the release of endogenous dopamine and 5-HT depresses sVRP and MSR respectively. CONCLUSION AND IMPLICATIONS These results suggested that dopamine at lower concentrations preferentially inhibited sVRP, which is mediated via dopamine D-1-like and other unidentified receptors. The dopamine-evoked depression is involved in modulating the spinal functions by the descending dopaminergic pathways.
  • K. Otsuguro, M. Wada, S. Ito
    BRITISH JOURNAL OF PHARMACOLOGY 164 (1) 132 - 144 0007-1188 2011/09 [Refereed][Not invited]
     
    BACKGROUND AND PURPOSE Hypoxic effects on neuronal functions vary significantly with experimental conditions, but the mechanism for this is unclear. Adenosine has been reported to play a key role in depression of neuronal activities in the CNS during acute hypoxia. Hence, we examined the effect of acute hypoxia on different spinal reflex potentials and the contribution of adenosine to them. EXPERIMENTAL APPROACH Spinal reflex potentials, monosynaptic reflex potential (MSR), slow ventral root potential (sVRP) and dorsal root potential (DRP), were measured in the isolated spinal cord of the neonatal rat. Adenosine release was measured by using enzymatic biosensors. KEY RESULTS In the spinal cord preparation isolated from postnatal day 5-8 rats at 27 degrees C, acute hypoxia induced adenosine release and depressed three reflex potentials. However, in postnatal day 0-3 rats at 27 degrees C, the hypoxic-induced adenosine release and depression of MSR were negligible, while the depression of sVRP and DRP were perceptible responses. In postnatal day 0-3 rats at 33 degrees C, hypoxia evoked adenosine release and depression of MSR. An adenosine A(1) receptor selective antagonist and a high [Ca2+](o), which suppressed adenosine release, abolished the hypoxic-induced depression of MSR but not those of sVRP and DRP. CONCLUSIONS AND IMPLICATIONS Hypoxic-induced depression of MSR depends on adenosine release, which is highly susceptible to age, temperature and [Ca2+](o). However, a large part of the depressions of DRP and sVRP are mediated via adenosine-independent mechanisms. This differential contribution of adenosine to depression is suggested to be an important factor for the variable effects of hypoxia on neuronal functions.
  • Ryo Miyamoto, Ken-ichi Otsuguro, Shigeo Ito
    NEUROSCIENCE LETTERS 499 (2) 137 - 142 0304-3940 2011/07 [Refereed][Not invited]
     
    Hydrogen sulfide (H(2)S) is considered as a gasotransmitter. Although several reports have shown that H(2)S stimulates sensory neurons, the primary targets of H(2)S remain controversial. We investigated the effects of H(2)S on cultured sensory neurons isolated from rat dorsal root ganglion (DRG) using Ca(2+) imaging and whole-cell voltage-clamp techniques. Brief (2 min) application of NaHS (1 mM), a donor of H(2)S, evoked marked increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in a subset of DRG neurons. These neurons also responded to both capsaicin and mustard oil (MO), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) agonists, respectively. The NaHS-evoked [Ca(2+)](i) increases were inhibited by a removal of external Ca(2+) and antagonists for TRPA1, but not for TRPV1 or voltage-dependent Ca(2+) channels. At -80 mV, NaHS evoked inward currents in MO-sensitive neurons, which were also inhibited by a TRPA1 antagonist. Even at lower concentration (<= 1 mu M), the 10-min application of NaHS increased [Ca(2+)](i) in a time- and concentration-dependent manner. These results suggest that H(2)S stimulates sensory neurons via activation of TRPA1. Endogenous H(2)S may be involved in physiological processes through TRPA1. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
  • T. Takahashi, K. Otsuguro, T. Ohta, S. Ito
    BRITISH JOURNAL OF PHARMACOLOGY 161 (8) 1806 - 1816 0007-1188 2010/12 [Refereed][Not invited]
     
    BACKGROUND AND PURPOSE Adenosine and inosine accumulate extracellularly during hypoxia/ischaemia in the brain and may act as neuroprotectants. In spinal cord, there is pharmacological evidence for increases in extracellular adenosine during hypoxia, but no direct measurements of purine release. Furthermore, the efflux pathways and origin of extracellular purines are not defined. To characterize hypoxia-evoked purine accumulation, we examined the effect of acute hypoxia on the extracellular levels of adenosine and inosine in isolated spinal cords from rats. EXPERIMENTAL APPROACH Extracellular adenosine and inosine concentrations were assayed in an in vitro preparation of the isolated spinal cord of the neonatal rat by HPLC. KEY RESULTS The extracellular level of inosine was about 10-fold higher than that of adenosine. Acute hypoxia (10 min) caused a temperature-dependent increase in these two purines, which were inhibited by an increase in external Ca2+, but not by several inhibitors of efflux pathways or metabolic enzymes of adenine nucleotides. Inhibitors of adenosine deaminase or the equilibrative nucleoside transporter (ENT) abolished the hypoxia-evoked increase in inosine but not adenosine. The inhibition of glial metabolism abolished the increase of both purines evoked by hypoxia but not by oxygen-glucose deprivation, hypercapnia or an adenosine kinase inhibitor. CONCLUSIONS AND IMPLICATIONS Our data suggest that hypoxia releases adenosine itself from intracellular sources. Inosine formed intracellularly may be released through ENTs. During hypoxia, astrocytes appear to play a key role in purine release from neonatal rat spinal cord.
  • Y. Kajihara, M. Murakami, T. Imagawa, K. Otsuguro, S. Ito, T. Ohta
    NEUROSCIENCE 166 (1) 292 - 304 0306-4522 2010/03 [Refereed][Not invited]
     
    In inflamed tissues, extracellular pH decreases and acidosis is an important source of pain. Histamine is released from mast cells under inflammatory conditions and evokes the pain sensation in vivo, but the cellular mechanism of histamine-induced pain has not been well understood. In the present study, we examined the effects of histamine on [Ca(2+)](i) and membrane potential responses to acid in isolated mouse dorsal root ganglion (DRG) neurons. In capsaicin-sensitive DRG neurons from wild-type mice, acid (>pH 5.0) evoked [Ca(2+)](i) increases, but not in DRG neurons from transient receptor potential V1 (TRPV1) (-/-) mice. Regardless of isolectin GS-IB4 (IB4)-staining, histamine potentiated [Ca(2+)](i) responses to acid (>= pH 6.0) that were mediated by TRPV1 activation. Histamine increased membrane depolarization induced by acid and evoked spike discharges. RT-PCR indicated the expression of all four histamine receptors (H1R, H2R, H3R, H4R) in mouse DRG. The potentiating effect of histamine was mimicked by an H1R agonist, but not H2R-H4R agonists and was inhibited only by an H1R antagonist. Histamine failed to potentiate the [Ca(2+)](i) response to acid in the presence of inhibitors for phospholipase C (PLC) and protein kinase C (PKC). A lipoxygenase inhibitor and protein kinase A inhibitor did not affect the potentiating effects of histamine. Carrageenan and complete Freund's adjuvant produced inflammatory hyperalgesia, but these inflammatory conditions did not change the potentiating effects of histamine in DRG neurons. The present results suggest that histamine sensitizes acid-induced responses through TRPV1 activation via H1R coupled with PLC/PKC pathways, the action of which may be involved in the generation of inflammatory pain. (C) 2010 IBRO. Published by Elsevier Ltd. All rights reserved.
  • Taketoshi Ogawa, Masami Hashimoto, Yoichi Niitsu, Joseph A. Jakubowski, Yoshiro Tani, Ken-ichi Otsuguro, Fumitoshi Asai, Atsuhiro Sugidachi
    EUROPEAN JOURNAL OF PHARMACOLOGY 612 (1-3) 29 - 34 0014-2999 2009/06 [Refereed][Not invited]
     
    Prasugrel is an orally available thienopyridyl prodrug with more potent in vivo antiplatelet effects compared to clopidogrel. In the present study, we examined the effects of prasugrel in rat models of cerebral and peripheral arterial occlusive diseases. Cerebral arterial thrombosis was induced by photochemical irradiation of the middle cerebral artery. Prasugrel (3 and 10 mg/kg) dose-relatedly and significantly reduced thrombus-mediated cerebral infarction 24 h after the irradiation. The effect of prasugrel was further examined in ail embolic infarction model. Four h after an oral administration of prasugrel, non-occlusive thrombus formation in the right common carotid artery was initiated. In this model, prasugrel (0.3-3 mg/kg) reduced incidence, total area, and total number of cerebral infarcts in a dose-related manner 24 h after the vascular injury. Clopidogrel (10 or 30 mg/kg) was less potent than prasugrel at the doses tested oil these thrombotic and embolic infarctions. Finally, the effect of prasugrel on lauric acid-induced peripheral arterial occlusive diseases was evaluated. After injection of lauric acid into the femoral artery, the lesions were scored for the following 10 days as they gradually progressed from the toe throughout the leg. Prasugrel (0.03-3 mg/kg/day) administered from the day before the lauric acid injection for 11 successive days inhibited the progression of the disease in a close-related manner. Clopidogrel (3-30 mg/kg/day) showed similar effect but its effect was less potent than prasugrel. These results suggest that prasugrel could be a useful drug for preventing thromboembolic diseases including cerebral infarction and peripheral arterial occlusive diseases. (C) 2009 Elsevier B.V. All rights reserved.
  • K. Otsuguro, M. Ban, T. Ohta, S. Ito
    BRITISH JOURNAL OF PHARMACOLOGY 156 (7) 1167 - 1177 0007-1188 2009/04 [Refereed][Not invited]
     
    The purine compounds, adenosine 5'-triphosphate (ATP) and adenosine, are known to accumulate in the extracellular space and to elicit various cellular responses during hypoxia/ischemia, whereas the roles of purines during hypercapnia are poorly understood. In this study, we examined the effects of various drugs affecting purine turnover on the responses to hypercapnia in the spinal cord. Electrically evoked reflex potentials were measured in an in vitro preparation of the isolated spinal cord of the neonatal rat by extracellular recording. Extracellular adenosine concentrations were assayed by high performance liquid chromatography (HPLC) methods. Hypercapnia (20% CO(2)) depressed the reflex potentials, which were partially reversed by an adenosine A(1) receptor antagonist, 8-cyclopentyl theophylline, but not by a P2 receptor antagonist, pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid. Exogenous adenosine and ATP also depressed the reflex potentials via adenosine A(1) receptors. The hypercapnia-evoked depression was not reversed by inhibitors of gap junction hemichannels, anion channels, P2X(7) receptors or equilibrative nucleoside transporters, all of which might be involved in purine efflux pathways. The adenosine accumulation evoked by hypercapnia was not inhibited by tetrodotoxin, ethylene glycol-bis(beta-amino ethyl ether) tetraacetic acid (EGTA) or an ecto-ATPase inhibitor, ARL 67156. Homocysteine thiolactone, used to trap intracellular adenosine, significantly reduced extracellular adenosine accumulation during hypercapnia. These results suggest that hypercapnia released adenosine itself from intracellular sources, using pathways different from the conventional exocytotic mechanism, and that this adenosine depressed spinal synaptic transmission via adenosine A(1) receptors.
  • Tetsuya Ishida, Ryo Takei, Shree Hari Gautam, Ken-ichi Otsuguro, Toshio Ohta, Shigeo Ito, Yoshiaki Habara, Toshiyuki Saito
    NEUROSCIENCE LETTERS 441 (3) 277 - 281 0304-3940 2008/08 [Refereed][Not invited]
     
    Bipolar vomeronasal sensory neurons (VSNs) in the vomeronasal organ (VNO) are believed to detect pheromones in most mammals. The vomeronasal sensory epithelium (VSE) is composed of VSNs and supporting cells. There are morphological differences in VNOs between species. Many electrophysiological experiments have been performed on rodent VSEs but few on other mammals. We therefore investigated voltage-gated channel properties of cells in the porcine VSE using slice whole-cell voltage-clamp techniques. In immunohistochemical study of the porcine VSE, most PGP9.5-immunoreactive cells were found between the middle and basal region, and negative cells were distributed in the apical to middle region. Depolarizing pulses to epithelial cells from -90 mV produced transient inward Na+ channel currents and sustained outward K+ channel currents with various amplitudes. The distribution of cells having high and low Na+ current densities was mostly consistent with the histological distribution of VSNs and supporting cells, respectively. The half-inactivation voltage of voltage-gated Na+ channels in supporting cells was 26 mV more negative than that in VSNs. Voltage-gated K+ channel currents in both cell types were suppressed by tetraethylammonium to the same extent. VSNs possessed TTX-sensitive voltage-gated Na+ channels and Ni2+-sensitive T-type Ca2+ channels. These results suggest that the histological distribution of porcine vomeronasal epithelial cells is more similar to the dog and goat than to rodents, and that the electrophysiological characteristics of porcine vomeronasal epithelial cells are similar to those of rodents. it is also suggested that porcine VSNs detecting pheromones generate action potentials through these channels. (c) 2008 Elsevier Ireland Ltd. All rights reserved.
  • Ken-ichi Otsuguro, Jisen Tang, Yufang Tang, Rui Xiao, Marc Freichel, Volodymyr Tsvilovskyy, Shigeo Ito, Veit Flockerzi, Michael X. Zhu, Alexander V. Zholos
    JOURNAL OF BIOLOGICAL CHEMISTRY 283 (15) 10026 - 10036 0021-9258 2008/04 [Refereed][Not invited]
     
    Full-length transient receptor potential (TRP) cation channel TRPC4 alpha and shorter TRPC4 beta lacking 84 amino acids in the cytosolic C terminus are expressed in smooth muscle and endothelial cells where they regulate membrane potential and Ca(2+) influx. In common with other "classical" TRPCs, TRPC4 is activated by G(q)/phospholipase C-coupled receptors, but the underlying mechanism remains elusive. Little is also known about any isoform-specific channel regulation. Here we show that TRPC4 alpha but not TRPC4 beta was strongly inhibited by intracellularly applied phosphatidylinositol 4,5-bisphosphate (PIP(2)). In contrast, several other phosphoinositides (PI), including PI(3,4)P(2), PI(3,5)P(2), and PI(3,4,5)P(3), had no effect or even potentiated TRPC4 alpha indicating that PIP(2) inhibits TRPC4 alpha in a highly selective manner. We show that PIP2 binds to the C terminus of TRPC4 & but not that of TRPC4 beta in vitro. Its inhibitory action was dependent on the association of TRPC4 alpha with actin cytoskeleton as it was prevented by cytochalasin D treatment or by the deletion of the C-terminal PDZ-binding motif (Thr-Thr-Arg-Leu) that links TRPC4 to F-actin through the sodium-hydrogen exchanger regulatory factor and ezrin. PIP(2) breakdown appears to be a required step in TRPC4 alpha channel activation as PIP(2) depletion alone was insufficient for channel opening, which additionally required Ca(2+) and pertussis toxin-sensitive G(i/o) proteins. Thus, TRPC4 channels integrate a variety of G-protein-dependent stimuli, including a PIP(2)/cytoskeleton dependence reminiscent of the TRPC4-like muscarinic agonist activated cation channels in ileal myocytes.
  • Yoichi Niitsu, Atsuhiro Sugidachi, Taketoshi Ogawa, Joseph A. Jakubowski, Masami Hashimoto, Takashi Isobe, Ken-ichi Otsuguro, Fumitoshi Asai
    EUROPEAN JOURNAL OF PHARMACOLOGY 579 (1-3) 276 - 282 0014-2999 2008/01 [Refereed][Not invited]
     
    (A)ntiplatelet and antithrombotic activity of multiple oral dosing of prasugrel were evaluated in several animal species. Prasugrel's active metabolite concentration-relatedly inhibited in vitro ADP-induced aggregation of rat, rabbit, dog, monkey and human platelets. Oral administration of prasugrel to dogs (0.03-0.3 mg/kg/day) and monkeys (0.1 and 0.3 mg/kg/day) once a day for 14 days resulted in potent, dose-related and cumulative inhibition of ADP-induced platelet aggregation. The inhibitory effects reached a plateau on days 3 to :5 and thereafter were maintained during dosing. Inhibition decreased gradually after cessation of dosing with near full recovery by 7 days after last dose. Antiplatelet and antithrombotic activity of prasugrel and clopidogrel were further examined in rats. Multiple oral dosing of prasugrel (0.3-3 mg/kg/day) to rats resulted in more potent inhibition of platelet aggregation compared to clopidogrel (3-30 mg/kg/day) and ticlopidine (30-300 mg/kg/day). Separate experiments confirmed that platelet inhibition was associated with inhibition of [H-3]-2-methylthio-ADP binding to rat platelets. In a rat model of electrically-induced arterial thrombosis, prasugrel (0.1-1 mg/kg/day, p.o.) significantly prolonged the time to arterial occlusion and increased the duration of arterial patency. The inhibition of platelet aggregation of prasugrel was about 10 and 300 times more potent than clopidogrel and ticlopidine, respectively. Overall these results show that in several species multiple oral administration of prasugrel results in more potent inhibition of platelet aggregation and thrombus formation than clopidogrel and ticlopidine, and that these effects are mediated by inhibition of platelet ADP receptors. (c) 2007 Elsevier B.V. All rights reserved.
  • M. Murakami, T. Ohta, K. -I. Otsuguro, S. Ito
    NEUROSCIENCE 145 (2) 642 - 653 0306-4522 2007/03 [Refereed][Not invited]
     
    We characterized bradykinin (BK)-induced changes in the intracellular Ca2+ concentration ([Ca2+](i)) and membrane potential in cultured rat myehteric neurons using ratiometric Ca2+ imaging with fura-2 and the whole-cell patchclamp technique, respectively. BK evoked a dose-dependent increase of [Ca2+](i) that was abolished by HOE 140, a 82 receptor antagonist but not by [Lys-des-Arg(9)]-BK, a 81 receptor antagonist. [Lys-des-Arg(9)]-HOE140, a B1 receptor agonist, failed to cause a [Ca2+](i) response. Double staining with antibodies against the 82 receptor together with PGP9.5 or S100 indicated that 82 receptors were expressed in neurons and glial cells. The BK-evoked [Ca2+](i) increase was suppressed by indomethacin, a non-selective cyclooxygenase (COX) inhibitor, and potentiated by prostaglandin E-2 (PGE(2)). The release of PGE2 from cultured myenteric plexus cells was increased by BK. BK induced a large increase in [Ca2+](i) in neurons when myenteric plexus cells were cultured at the high density but not at the low density, and caused a small increase in [Ca2+](i) in neurons when proliferation of enteric glial cells was suppressed. BK evoked a slow and sustained depolarization in myenteric neurons, which was sensitive to indomethacin.These results indicated that BK caused a [Ca2+](i) increase and depolarization in rat myenteric neurons through the activation of 132 receptors, which was partly associated with PGE(2) released from glial cells in response to BK. It is suggested that a neuron-glial interaction plays an important role in the effect of BK in the rat myenteric plexus. (c) 2007 IBRO. Published by Elsevier Ltd. All rights reserved.
  • S. H. Gautam, K. -I. Otsuguro, S. Ito, T. Saito, Y. Habara
    NEUROSCIENCE 144 (2) 702 - 713 0306-4522 2007/01 [Refereed][Not invited]
     
    Propagation of odor-induced Ca2+ transients from the cilia/knob to the soma in mammalian olfactory receptor neurons (ORNs) is thought to be mediated exclusively by high-voltage-activated Ca2+ channels. However, using confocal Ca2+ imaging and immunocytochemistry we identified functional T-type Ca2+ channels in rat ORNs. Here we show that T-type Ca2+ channels in ORNs also mediate propagation of odor-induced Ca2+ transients from the knob to the soma. In the presence of the selective inhibitor of T-type Ca2+ channels mibefradil (10-15 mu M) or Ni2+ (100 mu M), odor- and forskolin/3-isobutyl-1-methyl-xanthine (IBMX)-induced Ca2+ transients in the soma and dendrite were either strongly inhibited or abolished. The percentage of inhibition of the Ca2+ transients in the knob, however, was 40-50% less than that in the soma. Ca2+ transients induced by 30 mM K+ were partially inhibited by mibefradil, but without a significant difference in the extent of inhibition between the knob and soma. Furthermore, an increase of as little as 2.5 mM in the extracellular K+ concentration (7.5 mM K+) was found to induce Ca2+ transients in ORNs, and such responses were completely inhibited by mibefradil or Ni2+. Total replacement of extracellular Na+ with N-methyl-D-glutamate inhibited none of the odor-, forskolin/IBMX- or 7.5 mM K+-induced Ca2+ transients. Positive immunoreactivity to the Ca(v)3.1, Ca(v)3.2 and Ca(v)3.3 subunits of the T-type Ca2+ channel was observed throughout the soma, dendrite and knob. These data suggest that involvement of T-type Ca2+ channels in the propagation of odor-induced Ca2+ transients in ORNs may contribute to signal transduction and odor sensitivity. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.
  • Shree Hari Gautam, Ken-ichi Otsuguro, Shigeo Ito, Toshiyuki Saito, Yoshiaki Habara
    NEUROSCIENCE RESEARCH 57 (1) 129 - 139 0168-0102 2007/01 [Refereed][Not invited]
     
    T-type Ca2+ channels are low-voltage-activated Ca2+ channels that control Ca2+ entry in excitable cells during small depolarization above resting potentials. Using Ca2+ imaging with a laser scanning confocal microscope we investigated the involvement of T-type Ca2+ channels in IBMX/forskolin- and sparingly elevated extracellular K+-induced Ca2+ transients in freshly isolated porcine olfactory receptor neurons (ORNs). In the presence of mibefradil (10 mu M) or Ni2+ (100 mu M), the selective T-type Ca2+ channel inhibitors, IBMX/forskolin-induced Ca2+ transients in the soma were either strongly (> 60%) inhibited or abolished completely. However, the Ca2+ transients in the knob were only partially (< 60%) inhibited. Ca2+ transients induced by 30 mM K+ were also partially (similar to 60%) inhibited at both the knob and soma. Furthermore, ORNs responded to as little as a 2.5 mM increase in the extracellular K+ concentration (7.5 mM K+), and such responses were completely inhibited by mibefradil or Ni2+. These results reveal functional expression of T-type Ca2+ channels in porcine ORNs, and suggest a role for these channels in the spread Ca2+ transients from the knob to the soma during activation of the cAMP cascade following odorant binding to G-protein-coupled receptors on the cilia/knob of ORNs. (c) 2006 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
  • Toshio Ohta, Yuki Ikemi, Matsuka Murakami, Toshiaki Imagawa, Ken-ichi Otsuguro, Shigeo Ito
    JOURNAL OF PHYSIOLOGY-LONDON 576 (3) 809 - 822 0022-3751 2006/11 [Refereed][Not invited]
     
    5-Hydroxytryptamine (5-HT) is one of the major chemical mediators released in injured and inflamed tissue and is capable of inducing hyperalgesia in vivo. However, the cellular mechanisms of 5-HT-induced hyperalgesia remain unclear. Transient receptor potential V1 (TRPV1) plays a pivotal role in nociceptive receptors. In the present study, we determined whether 5-HT changes TRPV1 functions in cultured dorsal root ganglion (DRG) neurons isolated from neonatal rats, using Ca2+ imaging and whole-cell patch-clamp techniques. In more than 70% of DRG neurons, 5-HT potentiated the increases of [Ca2+](i) induced by capsaicin, protons and noxious heat. Capsaicin-induced current and depolarizing responses, and proton-induced currents were also augmented by 5-HT. RT-PCR analysis revealed the expression of 5-HT2A and 5-HT7 receptors in rat DRG neurons. Agonists for 5-HT2A and 5-HT7 receptors mimicked the potentiating effect of 5-HT, and their antagonists decreased it. In DRG ipsilateral to the complete Freund's adjuvant-injected inflammation side, expression levels of 5-HT2A and 5-HT7 mRNAs increased, and the potentiating effect of 5-HT was more prominent than in the contralateral control side. These results suggest that the PKC- and PKA-mediated signalling pathways are involved in the potentiating effect of 5-HT on TRPV1 functions through the activation of 5-HT2A and 5-HT7 receptors, respectively. Under inflammatory conditions, the increases of the biosynthesis of these 5-HT receptors may lead to further potentiation of TRPV1 functions, resulting in the generation of inflammatory hyperalgesia in vivo.
  • Ken-ichi Otsuguro, Yoshihiko Yamaji, Masaaki Ban, Toshio Ohta, Shigeo Ito
    JOURNAL OF PHYSIOLOGY-LONDON 574 (3) 835 - 847 0022-3751 2006/08 [Refereed][Not invited]
     
    Adenosine is one of the most important neuromodulators in the CNS, both under physiological and pathological conditions. In the isolated spinal cord of the neonatal rat in vitro, acute hypercapnic acidosis (20% CO2, pH 6.7) reversibly depressed electrically evoked spinal reflex potentials. This depression was partially reversed by 8-cyclopentlyl-1,3-dimethylxanthine (CPT), a selective A(1) adenosine receptor antagonist. Isohydric hypercapnia (20% CO2, pH 7.3), but not isocapnic acidosis (5% CO2, pH 6.7), depressed the reflex potentials, which were also reversed by CPT. An ecto-5'-nucleotidase inhibitor did not affect the hypercapnic acidosis-evoked depression. An inhibitor of adenosine kinase, but not deaminase, mimicked the inhibitory effect of hypercapnic acidosis on the spinal reflex potentials. Accumulation of extracellular adenosine and inhibition of adenosine kinase activity were caused by hypercapnic acidosis and isohydric hypercapnia, but not isohydric acidosis. These results indicate that the activation of adenosine A(1) receptors is involved in the hypercapnia-evoked depression of reflex potentials in the isolated spinal cord of the neonatal rat. The inhibition of adenosine kinase activity is suggested to cause the accumulation of extracellular adenosine during hypercapnia.
  • Shree Hari Gautam, Ken-ichi Otsuguro, Shigeo Ito, Toshiyuki Saito, Yoshiaki Habara
    NEUROSCIENCE RESEARCH 55 (4) 410 - 420 0168-0102 2006/08 [Refereed][Not invited]
     
    We investigated the relation between the intensity of odorant stimulation and the mode of spatiotemporal Ca2+ dynamics in Fluo-4-loaded rat olfactory receptor neurons (ORNs) using a confocal laser scanning microscope. We found that relatively smaller Ca2+ transients remained confined to the knob while larger ones spread to the soma with latency. Prolonged odor exposure ensured the spread of Ca2+ transients from the knob to the soma. Upon exposing ORNs to progressively increasing concentrations of odor, the Ca2+ transients that were confined to the knob at lower concentrations extended to the soma at higher concentrations. Stimulation with progressively increasing concentrations of forskolin plus IBMX yielded identical results. Partial inhibition of adenylyl cyclase by MDL12330A changed the odor response extending to the soma to a response confined to the knob. Blocking of L-type Ca2+ channels by nifedipine reduced the magnitude of the response extending to the soma but had no effect on the response confined to the knob. It is thus suggested that Ca2+ transients confined to the knob represent weak stimulation, and, speculatively, such responses either constitute inhibitory responses or indicate weak excitatory responses that fail to outstand the spontaneous electrical noise of ORNs. (c) 2006 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
  • K Otsuguro, T Ohta, S Ito
    NEUROSCIENCE 138 (1) 281 - 291 0306-4522 2006 [Refereed][Not invited]
     
    Zinc ions (Zn2+) are known to modulate the functions of a variety of channels, receptors and transporters. We examined the effects of Zn2+ on the reflex potentials evoked by electrical stimulation and responses to depolarizing agents in the isolated spinal cord of the neonatal rat in vitro. Zn2+ at low concentrations (0.5-2 mu M) inhibited, but at high concentrations (5 and 10 mu M) augmented, a slow depolarizing component (slow ventral root potential). Zn2+ had no effect on fast components (monosynaptic reflex potential; fast polysynaptic reflex potential). Unlike Zn2+, strychnine (5 mu M), a glycine receptor antagonist, and (S),9(R)-(-)-bicuculline methobromide (10 mu M), a GABA, receptor antagonist, potentiated both fast polysynaptic reflex potential and slow ventral root potential. Zn2+ (5 mu M) did not affect depolarizing responses to glutamate and N-methyl-D-aspartate. Zn2+ enhanced the substance P-evoked depolarization in the absence of tetrodotoxin (0.3 mu M) but not in its presence. The dorsal root potential was inhibited by (S),9(R)-(-)-bicuculline methobromide (10 mu M) but not by Zn2+ (5 gNl). The Zn2+- potentiated slow ventral root potential was inhibited by the N-methyl-D-aspartate receptor antagonists, ketamine (10 mu M) and DL-2-amino-5-phosphaonovaleric acid (50 mu M) but not by P2X receptor antagonists, pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (30 mu M) and 2',3'-O-(2,4,6-trinitrophenyl)ATP (10 mu M). Ketamine (10 mu M) and DL-2-amino-5-phosphaonovaleric acid (50 mu M) almost abolished spontaneous activities increased by Zn2+. It is concluded that Zn2+ potentiated slow ventral root potential induced by primary afferent stimulation, which was mediated by the activation of N-methyl-D-aspartate receptors but not by activation of P2X receptors or blockade of glycinergic and GABAergic inhibition. Zn2+ does not seem to directly affect N-methyl-D-aspartate receptors. The release of glutamate from interneurons may play an important role in Zn2+-induced potentiation of slow ventral root potential in the spinal cord of the neonatal rat. (c) 2005 Published by Elsevier Ltd on behalf of IBRO.
  • T Ohta, R Komatsu, T Imagawa, K Otsuguro, S Ito
    BIOCHEMICAL PHARMACOLOGY 71 (1-2) 173 - 187 0006-2952 2005/12 [Refereed][Not invited]
     
    In the present study, we cloned a porcine orthologue of transient receptor potential V1 (pTRPV1) and heterologously expressed it in human embryonic kidney (HEK) 293 cells to characterize its pharmacological properties. At the amino acid level, pTRPV1 was highly homologous (83-90%) to other orthologues of TRPV1. The expression of receptors was examined with current and [Ca2+] responses to capsaicin using whole-cell patch-clamp and fura-2 ratio imaging techniques, respectively, and by immunostaining with an anti-TRPV1 antibody. The receptors were characterized by changes in [Ca2+], in response to various vanilloid agonists, low pH and heat and by the effects of TRPV1 antagonists on them. The various TRPV1 agonists activated pTRPV1 in a dose-dependent manner in the order of potency of resiniferatoxin (RTX) > olvanil > capsaicin > phorbol 12-phenylacetate 13-acetate 20-homovanillate (PPAHV), phorbol 12,13-dinonanoate 20-homovanillate (PDNHV). Isovelleral and scutigeral had no effect. Endogenous vanilloids (anandamide > 15 (s)-HPETE >> NADA), low pH and noxious heat (> 42 degrees C) activated pTRPV1. Comparison of amino acid sequences with various mammalian TRPV1 homologues suggested some novel putative vanilloid recognition sites. TRPV1 antagonists, iodoRTX, ruthenium red and capsazepine suppressed capsaicin-induced responses. Similar to human TRPV1, but not rodent TRPV1, capsazepine was effective in blocking pH- and heat-induced responses. Similar pharmacological profiles were observed in cultured porcine dorsal root ganglion neurons. We discuss putative amino acid residues related to pharmacological differences among mammalian TRPV1 homologues. (c) 2005 Elsevier Inc. All rights reserved.
  • T Ohta, A Kubota, M Murakami, K Otsuguro, S Ito
    AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY 289 (5) G935 - G948 0193-1857 2005/11 [Refereed][Not invited]
     
    We characterized ATP-induced changes in intracellular Ca2+ concentration ([Ca2+](i)) and membrane current in cultured rat myenteric neurons using ratiometric Ca2+ imaging with fura-2 and the whole cell patch-clamp technique, respectively. Neuronal cells were functionally identified by [Ca2+](i) responses to high K+ and nicotine, which occurred only in cells positive for neuron-specific protein gene product 9.5 immunoreactivity. ATP evoked a dose-dependent increase of [Ca2+](i) that was greatly decreased by the removal of extracellular Ca2+ concentration ([ Ca2+](o)). The amplitude of the [Ca2+](i) response to ATP was reduced by half in the presence of voltage-dependent Ca2+ channel blockers. In [Ca2+](o)-free solution, ATP produced a small transient rise in [Ca2+](i) similar to that induced by P2Y agonists. At -60 mV, ATP evoked a slowly inactivating inward current that was suppressed by the removal of extracellular Na+ concentration. The current-voltage relation for ATP showed an inward rectification with the reversal potential of about 0 mV. The apparent rank order of potency for the purinoceptor agonist-induced increases of [Ca2+](i) was ATP >= adenosine 5'-O-3-triphosphate >= CTP >= 2-methylthio-ATP > benzoylbenzoyl-ATP. A similar potency order was obtained with current responses to these agonists. P2 antagonists inhibited inward currents induced by ATP. Ca2+ and Mg2+ suppressed the ATP-induced current, and Zn2+, Cu2+, and protons potentiated it. RT-PCR and immunocytochemical studies showed the expression of P2X(2) receptors in cultured rat myenteric neurons. These results suggest that ATP mainly activates ionotropic P2X(2) receptors, resulting in a [Ca2+](i) increase dependent on [Ca2+](o) in rat myenteric neurons. A small part of the ATP-induced [Ca2+](i) increase may be also mediated via a P2Y receptor-related mechanism.
  • K Otsuguro, S Yasutake, T Ohta, S Ito
    DEVELOPMENTAL BRAIN RESEARCH 158 (1-2) 50 - 58 0165-3806 2005/08 [Refereed][Not invited]
     
    The inhibitory effects of morphine and alpha(2)-adrenoceptor agonists on slow ventral root potentials (slow VRP) following ipsilateral dorsal root stimulation in neonatal rat spinal cord were compared with the analgesic effects of these drugs on formalin and capsaicin tests in neonatal rats. Morphine, (D-Phe(2), D-Pen(5))-enkephalin (DPDPE), dexmedetomidine, clonidine and xylazine showed concentration-related inhibition of slow VRP. The order of potency was dexmedetomidine > morphine = DPDPE > clorridine > xylazine. The inhibitory effects of opioid agonists and alpha(2)-adrenoceptor agonists were abolished by naloxone, an opioid antagonist, and atipamezole, an alpha(2)-adrenoceptor antagonist, respectively. There was no cross antagonism. Morphine, dexmedetomidine and xylazine dose-dependently inhibited body movement induced by formalin or capsaicin. The order of potency was dexmedetomidine > morphine > xylazine. Although morphine and dexmedetomidine inhibited formalin- and capsaicin-induced body movement in the same dose range, xylazine inhibited formalin-induced body movement at lower concentrations than capsaicin-induced one. The inhibitory potency for slow VRP by these drugs seems to be correlated with that for capsaicin-induced body movement but not that for formalin-induced one. Dexmcdetomidine and morphine in combination inhibited slow VRP and body movement induced by capsaicin in an additive manner. It is suggested that the antinociceptive effects of dexmedetomidine and morphine but not xylazine on the capsaicin test are mainly due to spinal effects and that there is no synergistic interaction between dexmedetomidine and morphine in the neonatal rat. (c) 2005 Elsevier B.V. All rights reserved.
  • K Otsuguro, SH Gautam, S Ito, Y Habara, T Saito
    JOURNAL OF PHARMACOLOGICAL SCIENCES 97 (4) 510 - 518 1347-8613 2005/04 [Refereed][Not invited]
     
    Forskolin-induced Ca2+ signals were examined in isolated rat olfactory receptor neurons (ORNs) using a Ca2+ indicator, fura-2. In the soma of the ORNs, forskolin caused an increase in the intracellular Ca(2+)concentration ([Ca2+](i)) that was enhanced by a phosphodiesterase(PDE)1 inhibitor, 8-methoxymethyl-3-isobutyl-1-methyl-xanthine, but not a PDE4 inhibitor, rolipram. Forskolin-induced Ca2+ signals were abolished with the removal of extracellular Ca2+ and un-affected by treatment with thapsigargin or caffeine plus ryanodine. Niflumic acid, a Ca2+-activated Cl- channel inhibitor, or nifedipine, an L-type Ca2+ channel inhibitor, slowed the initial rate of the increase in [Ca2+]i in response to forskolin. Nifedipine did not affect the increase in [Ca2+](i) that was slowed by niflumic acid. In Ca2+ measurements with a confocal microscope and a calcium indicator, Fluo-4, the onset of the response to forskolin in the knob region occurred simultaneously or earlier, but not later, than that in the soma. It is suggested that the forskolin-induced Ca2+ signals are due to Ca2+ influx, but not the release of Ca2+ from Ca2+ stores, and that the initial rapid increase in [Ca2+](i) is associated with the activation of the voltage-dependent Ca2+ channels in rat ORNs.
  • Y Suzuki, K Kondo, Y Matsumoto, BQ Zhao, K Otsuguro, T Maeda, Y Tsukamoto, T Urano, K Umemura
    LIFE SCIENCES 73 (10) 1289 - 1298 0024-3205 2003/07 [Refereed][Not invited]
     
    We have previously demonstrated that natto-extracts containing nattokinase (NK) inactivates plasminogen activator inhibitor type 1 and then potentiates fibrinolytic activity. In the present study, we investigated the effects of dietary supplementation with natto-extracts on neointima formation and on thrombolysis at the site of endothelial injury. Endothelial damage in the rat femoral artery was induced by intravenous injection of rose bengal followed by focal irradiation by transluminal green light. Dietary natto-extracts supplementation containing NK of 50 or 100 CU/body was started 3 weeks before endothelial injury and then continued for another 3 weeks. Intimal thickening in animals given supplementation was significantly (P < 0.01) suppressed compared with controls and the intima/media ratio in animals with 50 and 100 CU/body NK and control group was 0.09 +/- 0.03, 0.09 +/- 0.06 and 0.16 +/- 0.12, respectively. Although femoral arteries were reopened both in control animals and those treated with NK within 8 hours after endothelial injury, mural thrombi were histologically observed at the site of endothelial injury. In the control group, the center of vessel lumen was reopened and mural thrombi were attached on the surface of vessel walls. In contrast, in NK-treated groups, thrombi near the vessel wall showed lysis and most of them detached from the surface of vessel walls. In conclusion, dietary natto-extracts supplementation suppressed intimal thickening produced by endothelial injury in rat femoral artery. These effects may partially be attributable to NK, which showed enhanced thrombolysis near the vessel wall. (C) 2003 Elsevier Science Inc. All rights reserved.
  • T Ogawa, A Sugidachi, K Otsuguro, T Isobe, F Asai
    BIOCHEMICAL PHARMACOLOGY 63 (10) 1911 - 1918 0006-2952 2002/05 [Refereed][Not invited]
     
    Platelet-agonist interaction results in aggregatory and secretory responses. While the activation of glycoprotein (GP) IIb/IIIa plays an essential role in platelet aggregation, its role in granule secretion is not clear. The present study was performed to examine the effect of 3-[[[[1-[4-(aminoiminomethyl) phenyl] -2-oxo-3S-pyrrolidinyl] amino] carbonyl] amino] -propanoate monohydrochloride salt (SC-57101A), a GPIIb/IIIa antagonist, on platelet alpha-granule secretion responses to collagen, ADP, and thrombin receptor activating peptide (TRAP). Both SC-57101A and prostaglandin E-1 (PGE(1)) inhibited collagen-, ADP-, and TRAP-induced platelet aggregation in a concentration-dependent manner. SC-57101A inhibited the collagen- and ADP-induced release of platelet-derived growth factor (PDGF) and beta-thromboglobulin (beta-TG) from platelets, but not TRAP-induced secretion of these granule contents. On the other hand, PGE(1) inhibited the release of PDGF and beta-TG from platelets activated with all the agonists used. ADP and TRAP elicited P-selectin expression in the absence of platelet aggregation, while collagen produced no such reaction. SC-57101A only moderately inhibited P-selectin expression induced by ADP and had no inhibitory effect on that induced by TRAP. The inhibition of ADP-induced secretion of alpha-granule contents by SC-57101A was abolished when platelets were pretreated with aspirin. These results suggest that GPIIb/IIIa activation plays a minor role, if any, in a granule secretion in human platelets. (C) 2002 Elsevier Science Inc. All rights reserved.
  • A Sugidachi, F Asai, K Yoneda, R Iwamura, T Ogawa, K Otsuguro, H Koike
    BRITISH JOURNAL OF PHARMACOLOGY 132 (1) 47 - 54 0007-1188 2001/01 [Refereed][Not invited]
     
    1 CS-747 is a novel thienopyridine-type platelet ADP inhibitor which lacks in vitro activity. This study examined pharmacological profiles of R-99224, a hepatic metabolite of CS-747. 2 R-99224 produced a concentration-dependent inhibition of in vitro platelet aggregation in washed human platelets (0.03-1 mug ml(-1)), which was relatively specific to ADP compared to collagen and thrombin. 3 R-99224 (0.1-3 mug ml(-1)) also elicited a similar inhibition of ADP-induced aggregation in rat platelets. The inhibition by R-99224 (10 mug ml(-1)) persisted even after platelets were washed three times. Intravenous injection of R-99224 (0.1-3 mg kg(-1)) to rats resulted in a dose-dependent inhibition of ex vivo ADP-induced platelet aggregation. 4 R-99224 (0.1-100 muM) decreased binding of [H-3]-2-methylthio-ADP ([H-3]-2-MeS-ADP), a stable ligand for platelet ADP receptors, to washed human platelets. The inhibition by R-99224 reached a plateau at a concentration of 3 muM (1.4 mug ml(-1)), but complete inhibition was not achieved even at the highest concentration used (100 muM). 5 R-99224 (10 muM) in combination with ARL-66096 (0.3 muM), an ATP analogue-type Gi-linked P2T receptor antagonist, produced no additional inhibition of [H-3]-2-MeS-ADP binding. In contrast, [H-3]-2-MeS-ADP binding was completely abolished by R-99224 (10 muM) in combination with A3P5PS (300 muM), a selective P2Y(1) antagonist, suggesting that R-99224 selectively binds to the G(i)-linked P2T receptor. 6 R-99224 (0.01-3 mug ml(-1)) inhibited ADP-induced [I-125]-fibrinogen binding to human platelets in a concentration-dependent manner. R-99224 (0.1-1 mug ml(-1)) also inhibited the ADP-induced decrease in cyclic AMP levels in PGE(1)-stimulated platelets, whereas the agent did not affect ADP (10 muM)-induced Ca2+ mobilization. 7 These findings suggest that R-99224 is a selective and irreversible antagonist of Gi-linked P2T receptors and that R-99224 is a responsible molecule for in vivo actions of CS-747.
  • K Otsuguro, T Ohta, S Ito, Y Nakazato
    JAPANESE JOURNAL OF PHARMACOLOGY 78 (2) 209 - 215 0021-5198 1998/10 [Refereed][Not invited]
     
    Effects of purinoceptor antagonists on the relaxant responses to adenine nucleotides were examined to characterize the subtypes of Pt-receptor in rat gastric circular muscle. In tissues contracted by acetylcholine, a Pt-receptor antagonist, suramin (100 mu M), inhibited the relaxant responses to ATP, adenosine 5'-O-(2-thiodiphosphate) (ADP beta S) and alpha,beta-methylene ATP but not that to adenosine, while a Pi-receptor antagonist, 8-phenyltheophylline (3 mu M) did vice versa. The inhibitory effect of suramin was more potent for the relaxant responses to cr,il-methylene ATP than those to ATP or ADP beta S. Pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) (3-30 mu M) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonate (DIDS) (30 and 100 mu M) inhibited the relaxation caused by a,alpha,beta-methylene ATP but not by ATP, ADP beta S or adenosine. These results suggest that ATP and ADP beta S cause relaxation via the classical P-2Y receptors resistant to PPADS and DIDS. In addition, alpha,beta-methylene ATP causes relaxation via the distinct P-2 receptors sensitive to PPADS and DIDS in rat gastric circular muscle.
  • K Otsuguro, S Ito, T Ohta, Y Nakazato
    EUROPEAN JOURNAL OF PHARMACOLOGY 317 (1) 97 - 105 0014-2999 1996/12 [Refereed][Not invited]
     
    The effects of UTP were examined to characterize the receptor subtypes for UTP in the circular smooth muscle of the rat proximal stomach. The rank order of potency for contraction was 2-methylthio ATP much greater than ATP greater than or equal to UDP = UTP greater than or equal to adenosine 5'-O-(3-thiotriphosphate)(ATP-gamma-S) much greater than UMP > CTP = alpha,beta-methylene ATP > adenosine = uridine. In tissues contracted by acetylcholine, ATP, 2-methylthio ATP, alpha,beta-methylene ATP and adenosine each caused relaxation. alpha,beta-Methylene ATP had the most potent effect and UTP caused only a small relaxation. Suramin inhibited ATP- and UTP-induced contractions. The contractile responses to ATP decreased in tissues desensitized with UTP, ATP-gamma-S and 2-methylthio ATP, but not with alpha,beta-methylene ATP. However, UTP-induced contraction was not inhibited by desensitization with ATP, alpha,beta-methylene ATP, ATP-gamma-S and 2-methylthio ATP. These results suggest that UTP causes contraction via receptors different from common P-2 purinoceptors. These receptors are blocked by suramin in the rat proximal stomach.
  • K Otsuguro, T Ohta, S Ito, Y Nakazato
    PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY 431 (3) 402 - 407 0031-6768 1996/01 [Refereed][Not invited]
     
    The effects of extracellular adenosine 5'-triphosphate (ATP) on currents were examined using the: whole-cell voltage-clamp technique in guinea-pig isolated adrenal chromaffin cells. ATP (500 mu M) reversibly suppresssd Ca2+ currents ill the presence of 5 mM Ca2+ in the extracellular solution. The inhibitory effect of ATP on Ca2+ currents tended to increase with increases in the peak amplitude of ATP-evoked current when the intracellular solution contained 0.1 or 1 mM ethylenebis(oxonitrilo)tetraacetate(EGTA). Using the intracellular solution containing 10 mM EGTA, on the other hand, the inhibitory efftect did not change regardless of the amplitude of current responses to ATP. In the presence of 10 mM Ba2+, ATP (100 mu M) reduced Ba2+ currents in a mariner similar to Ca2+ currents. This reduction was decreased by dialysis of cells with the internal solution containing guanosine 5'-O-(2-thiodiphosphate) (GDP [beta-S]; 1 mM) or guanosine 5'-O-(3-thiotriphosphate) (GTP [gamma-S]. 100 mu M). A depolarizing prepulse to + 100 mV partly relieved ATP-induced reduction of Ba2+ currents. ADP, AMP and adenosine also reduced Ba2+ currents and the effect of adenosine was the most potent. Adenosine (0.5 and 1 mM) significantly inhibited adrenaline secretion induced by nicotine (50 mu M). Ca2+ entry through ATP-activated non-selective cation channels results in the inactivation of voltage-dependent Ca2+ channels. In addition, ATP seems to modulate Ca2+ channels via the pathway related to G-protein. Adenine nucleotides and adenosine may play a role in controlling secretory activity in guinea-pig adrenal chromaffin cells.
  • T Asano, T Ohta, K Otsuguro, S Ito, Y Nakazato
    JOURNAL OF VETERINARY MEDICAL SCIENCE 57 (6) 1067 - 1071 0916-7250 1995/12 [Refereed][Not invited]
     
    Muscarinic receptor subtypes mediating catecholamine secretion and increase in the intracellular concentration of Ca2+ ([Ca2+](i)) were examined using muscarinic agonists and antagonists in dispersed adrenal chromaffin cells of the guinea pig. All muscarinic agonists (1-1,000 mu M) tested caused increases in adrenaline secretion in a dose-dependent manner. Muscarine and methacholine were more effective than bethanechol, oxotremorine and pilocarpine. Muscarine and oxotremorine caused a small increase in adrenaline secretion even in the absence of extracellular Ca2+. Both 4-DAMP (0.1 mu M) and pirenzepine (0.1 mu M), but not methoctramine (0.1 mu M), shifted the dose-response curve for muscarine-induced adrenaline secretion to the right. These muscarinic agonists also caused increase in [Ca2+](i) in the presence of extracellular Ca2+. Muscarine-induced [Ca2+](i) rises were reduced, but not abolished, by removal of extracellular Ca2+. These results suggest that catecholamine secretion induced by muscarinic agonists is mediated through M(1), or M(1) and M(3) muscarinic receptor subtypes in adrenal chromaffin cells of the guinea pig.
  • Asano, T, Otsuguro, K, Ohta, T, Sugawara, T, Ito, S, Nakazato, Y
    Comparative Biochemistry and Physiology C-Pharmacology Toxicology & Endocrinology 112 (2) 101 - 108 1367-8280 1995/10 [Refereed][Not invited]
  • K OTSUGURO, T ASANO, T OHTA, S ITO, Y NAKAZATO
    NEUROSCIENCE LETTERS 187 (3) 145 - 148 0304-3940 1995/03 [Refereed][Not invited]
     
    Adenosine 5'-triphosphate (ATP) evoked an inward current in whole-cell voltage-clamped adrenal chromaffin cells of the guinea pig. The reversal potential (E(rev)) of ATP-evoked current was about 0 mV in normal external solution and was shifted towards negative potentials by substituting Tris(+) or sucrose, but not Ca2+, for the extracellular Na+. This current was mediated by the activation of nonselective cation channels and had some different properties from nicotinic current. It is suggested that these channels may function as a part of the ATP-induced Ca2+ influx pathway in guinea pig chromaffin cells.

MISC

Books etc

  • 薬理学・毒性学実験 第4版
    日本比較薬理学・毒性学会 (Contributor)
    文栄堂出版 2023/03 (ISBN: 9784830032868)
  • 獣医薬理学（第二版）
    日本比較薬理学, 毒性学会 (Joint editor)
    近代出版 2021/03
  • 獣医臨床薬理学
    日本比較薬理学, 毒性学会 (Joint editor)
    近代出版 2017/12
  • 薬理学・毒性学実験 第3版
    日本比較薬理学, 毒性学会 (Contributor)
    文栄堂出版 2008/04

Presentations

  • Investigation of analgesic effect of carbon dioxide in isolated spinal cord preparation - Alternative to in vivo pain tests- Section "Alternatives to animal use"  [Invited]
    Ken-ichi OTSUGURO
    The 2nd Joint Meeting of Veterinary Science in East Asia  2019/04
  • 北海道大学の動物実験教育の取り組み  [Invited]
    乙黒 兼一
    第161回日本獣医学会学術集会 第14回獣医学教育改革シンポジウム  2018/09
  • Effects of adenosine on spinal neuronal activities: its contribution to hypercapnia-evoked depression  [Invited]
    Ken-ichi OTSUGURO
    The 14th Seoul National University – Hokkaido University Joint Symposium  2011/11
  • 脊髄反射電位に対するアデノシンの作用と低酸素惹起シナプス伝達抑制への関与 シンポジウム「虚血病態の病態と治療」  [Invited]
    乙黒 兼一
    第38回 薬物活性シンポジウム  2010/11
  • 二酸化炭素の薬理作用  [Invited]
    乙黒 兼一
    第146回 日本獣医学会学術集会 日本実験動物医学会教育シンポジウム  2008/09

Association Memberships

  • THE JAPANESE SOCIETY FOR NEUROCHEMISTRY   日本獣医学会   日本薬理学会   

Research Projects

  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2024/04 -2028/03 
    Author : 乙黒 兼一
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2021/04 -2024/03 
    Author : 乙黒 兼一
     
    本年度は、炎症性ストレスモデルとしてマウスにLPS（リポポリサッカライド）を投与した。マウスの活動量や飲水量に影響を与えない条件下で、強制水泳試験における不動時間の増加や、新規物体探索試験における探索時間の減少が示されたことから、うつ様行動の発現と短期記憶の障害が示唆された。エバンスブルー投与により血液脳関門の透過性を評価したが、透過性の増加は認められず、本実験条件では血液脳関門の破綻などは起きていないと考えられた。 LPS投与後、アストロサイトとミクログリアの活性化の指標となるGFPA及びIba-1の発現増加が海馬において認められた。アストロサイトは突起数の増加などSholl分析で形態が複雑化していることが示されたが、反応性アストロサイトの指標となるマーカー分子に変化は見られなかった。また、ニューロンマーカーNeuNでの染色では海馬ニューロンの密度に変化はなかった。ゴルジ染色により海馬ニューロンのスパインを評価したところ、スパインの密度に変化は見られなかったが、未熟/成熟スパインの割合が増加していたことから、海馬でのシナプス伝達が変化していることが示唆された。 脳の機能的変化とプリン動態との関連性を検討するために、脳内におけるプリン代謝関連分子のmRNA発現を調べた。複数のプリン代謝酵素の発現がLPS投与モデルにおいて増加、あるいは減少していることが確認され、脳内プリン動態の変化が脳機能に影響を与えている可能性がある。
  • ベクター媒介性感染症におけるベクター唾液の役割の解明
    文部科学省 科学研究費助成事業：基盤研究Ｂ
    Date (from‐to) : 2015 -2018 
    Author : 加藤 大智, 乙黒 兼一, 佐藤 晃一
  • 細胞外アデノシンデアミナーゼの分泌機構の解明
    内藤記念科学振興財団：奨励金・研究助成
    Date (from‐to) : 2018 
    Author : 乙黒 兼一
  • グリア伝達物質による脊髄アストロサイト機能の調節機構と病態下における役割の解明
    北海道大学：科研費種目ステップアップ支援事業
    Date (from‐to) : 2017 
    Author : 乙黒 兼一
  • シスタチオニンβ合成酵素の発現調節を介した新規中枢疾患治療ターゲットの探索
    秋山記念生命科学振興財団：研究奨励（一般）
    Date (from‐to) : 2017 
    Author : 乙黒 兼一
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014 -2016 
    Author : Otsuguro Ken-ichi, YAMAGUCHI Soichiro
     
    Production and release mechanisms of adenosine and hydrogen sulfide (H2S), which are known to be neuroprotective agents, were examined in the cultured spinal astrocytes. Under the low Ca2+ conditions, ATP released by astrocytes was extracellularly degraded to adenosine, resulting in the increase in extracellular adenosine level. The astrocytic CBS (H2S synthase) expression was suggested to be controlled/maintained by the neurons. Adenosine and H2S affect cellular functions via the activation of receptors and ion channels. Under the ischemic conditions, it is suggested that the change in adenosine and H2S production and releases by the low Ca2+ and/or neuronal death is involved in disease onset and progression.
  • 中枢神経組織における硫化水素産生機構とアストロサイトの役割の解明
    寿原記念財団：研究助成金
    Date (from‐to) : 2015 
    Author : 乙黒 兼一
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011/04 -2014/03 
    Author : ITO Shigeo, OTSUGURO Ken-ichi
     
    alpha-Adrenoceptor agonists, dexmedetomidine and xylazine inhibited spinal motor and nociceptive reflex potentials. In the alpha2A receptor-functional deficient D79N mice, the inhibitory effect on nociceptive but not motor reflex potentials by these agonists was attenuated. alpha2A-Receptors are suggested to be involved in the alpha2-agonist-evoked analgesia but not the inhibition of motor reflex. Adenosine and hydrogen sulfide (H2S) influence spinal neuronal activity. In the spinal astrocytes, the adenosine metabolic inhibitors released adenosine, while Ca2+-removal released ATP, which was degraded to adenosine. In the neurons, H2S is produced by the synthase CST/MPST.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2012 
    Author : ITO Shigeo, OTSUGURO Kenichi
     
    The effects of algesic and analgesic agents on the sensory neurons and spinal nociceptive pathways were examined to reveal the species differences in pain transmission. In the rat sensory neurons, the algesic agents, capsaicin and mustard oil, activated TRP channels. The electrophysiological features of spinal nociceptive reflex potentials and the effects of morphine in mice were similar to those in rats. Some differences in the effects of biogenic amines between rats and mice were observed, suggesting that there are species differences in pain control mechanisms by descending inhibitory neuronal pathways in the spinal cord.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2012 
    Author : OTSUGURO Kenichi, ITO Shigeo
     
    The effects of an hydrogen sulfide (H2S) donor, NaHS, on the sensory neurons and model cells (RIN14B) for enterochromaffin cells were examined. H2S increased intracellular Ca2+ levels via the activation of TRPA1, resulting in neuronal excitation and secretory responses. The neuronal model PC12 cells expressed AST (aspartate aminotransferase)/MPST (mercaptopyruvate sulfurtransferase) and generated H2S. In the intestine, it is suggested that neuronal cells not only respond to intraluminal H2S but also synthetizes H2S to regulate gastrointestinal functions.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(C))
    Date (from‐to) : 2008 -2010 
    Author : Ken-ichi OTSUGURO
     
    It is well-known that hypoxia and acidosis significantly influence neuronal functions under ischemic conditions. In this study, an electrical activity of spinal neuronal pathways and extracellular purine concentration were measured. Hypoxia and acidosis released not only adenosine but also inosine from the spinal cord, and adenosine suppressed the neuronal activities via adenosine A1 receptors. In addition, the influence of hypoxia largely depended on age, temperature and neuronal pathways. It is suggested that adenosine plays an important role in this phenomenon.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2007 -2009 
    Author : Shigeo ITO, Ken-ichi OTSUGURO
     
    We found that vanilloid receptor (TRPV1) channels, being key proteins for pain generation, were activated by mustard oil or methylsalicylate in addition to a vanilloid compound such as capsaicin and that the opening of the channels was controlled by extracellular Na^+ ions. It was demonstrated that histamine and 5-hydroxy- tryptamine, which were released at inflammation sites, augmented pain due to TRPV1 channel activation through respective receptors for these amines, and that adenosine release was associated with the analgesic action in response to hypercapnia.
  • 文部科学省：科学研究費補助金(萌芽研究)
    Date (from‐to) : 2007 -2008 
    Author : 伊藤 茂男, 梅村 孝司, 乙黒 兼一, 生駒 俊之
     
    1) 徐放担体の開発 : 以下の3点を調べた。(1) ヒドロキシアパタイト(HAP直径5μm)含有金属 : ポリ乳酸処理インスリン含有亜鉛(Zn)-HAP投与による血中インスリン濃度の増加は投与後2日で投与前のレベルに回復したが、投与したHAP中にインスリンは残留していた。鉄(Fe)-HAPとマグネシウム(Mg)-HAPを用いて、インスリンの徐放性を調べたが、Zn-HAPと同様、一過性の血糖低下作用と血中インスリン濃度増加作用しか示さなかった。(2)HAP粒子の大きさ : 直径2.5μmの脚と25μmのHAPをラットに皮下投与し、その消失速度を調べた。HAPの粒子径が小さくなると皮下投与部位からの消失速度が速まった(2.5μm ; 10日、5μm ; 14日、25μm ; 20日)。糖尿病ウサギにこれらインスリン含有HAPを投与して、血糖値と血中インスリン濃度変化を調べた結果、血糖低下反応とインスリン増加反応は投与後2日目で回復した。2.5μmの方が、インスリン増加は僅かに持続した。(3)薬物の併用 : インスリン-HAPをアルギン酸、カルボキシメチルセルロース(CMC)、デキサメサゾン(Dex)とともに投与したが、インスリン増加と血糖低下作用は一過性であった。2)製剤の毒性評価 : HAPのみ、CMC+HAP、アルギン酸+HAP、Dex+HAP、Fe-HAP、Mg-HAPを...
  • アシドーシスによる脊髄の機能変化
    上原記念生命科学財団：研究奨励金
    Date (from‐to) : 2008 
    Author : 乙黒 兼一
  • 病態動物モデルを用いた血管変性機序の解明
    文部科学省：大学教育の国際化推進プログラム（海外先進研究実践支援）
    Date (from‐to) : 2006/04 -2007/03 
    Author : 乙黒 兼一
  • 文部科学省：科学研究費補助金(若手研究(B))
    Date (from‐to) : 2005 -2006 
    Author : 乙黒 兼一
     
    本研究の目的である摘出脊髄標本を用い、亜鉛の脊髄神経に与える影響を明らかにするため、新生ラットから摘出した脊髄半裁標本を用いて脊髄反射電位に対する亜鉛の効果を検討し、以下の結果を得た。1.脊髄後根を電気刺激すると、対応する前根からMSR(monosynaptic reflex potential)、fPSR(fast polysynaptic reflex potential)及びsVRP(slow ventral root potential)が、また隣接する後根からDRP(dorsal root potential)記録された。2.亜鉛は、MSR、fPSRには影響を与えず、sVRPに対しては低濃度(0.5-2μM)では抑制、高濃度(5及び10μM)では増強作用を示した。また高濃度亜鉛によってベース前根電位のわずかな脱分極が観察され、激しい自発活性の増加が生じる標本もあった。3.グリシン受容体拮抗薬ストリキニーネとGABA_A受容体拮抗薬ビククリンは、亜鉛と異なりsVRPとともにfPSRも増強した。4.GABA_A受容体拮抗薬ビククリンは、DRPを抑制したが、亜鉛はDRPに影響を与えなかった。5.亜鉛による増強効果は、NMDA受容体拮抗薬ケタミン及びAP-5によって抑制されたが、ATP受容体拮抗薬PPADS及びTNP-ATPは亜鉛の効果に影響を与えなかった。以上の結果から、...
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2002 -2004 
    Author : Shigeo ITO, 太田 利男, 乙黒 兼一
     
    1)Serotonin (5-HT) potentiated Ca^<2+> response to capsaicin in cultured rat dorsal root ganglion (DRG) cells expressing 5-HT_<2A> and 5-HT_7 receptors. The increased response was inhibited by the blocker of protein kinase C or protein kinaseA. 2)In isolated neonatal rat spinal cord, electrical stimulation of the L3 ventral root elicited a fast monosynaptic reflex potential (MSR) followed by very slow potential change (sVRP) in the ipsilateral L3 ventral root. The sVRP was inhibited by α2 adrenoceptor agonists, dexmedetomidine (DEX), xylazine (XY) and clonidine (CLO) or opiate receptor agon...
  • ラット嗅細胞の匂い応答におけるイオンチャネルと細胞内情報伝達系の関与に関する研究
    秋山記念生命科学振興財団：研究助成（奨励）
    Date (from‐to) : 2003 
    Author : 乙黒 兼一
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 1998 -1998 
    Author : 乙黒 兼一

Social Contribution

  • モンゴル獣医・畜産分野人材育成能力強化プロジェクト
    Date (from-to) : 2018
    Role : Lecturer
    Sponser, Organizer, Publisher  : 国際協力機構・モンゴル生命科学大学 獣医学部
  • スーパーサイエンスハイスクール
    Date (from-to) : 2012-2016
    Role : Lecturer
    Sponser, Organizer, Publisher  : 北海道釧路湖陵高等学校
    Event, Program, Title : KCS基礎

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