遺伝子改変マウスを用いDREADDsや光遺伝学的手法を駆使し、睡眠研究を行っています。視床下部に存在する神経ペプチドや神経伝達物質を標的としており、それぞれの神経系がどのように睡眠覚醒サイクルを調節しているのかについて研究を行っています。
Medical undergraduate students who will become medical doctors should have enough knowledge and understandings of medication since they will administer medical drugs to cure or examine the patients in hospital. Our current pharmacological practice is intended for the students to learn pharmacokinetics of drugs by focusing on administration, metabolism and excretion of aspirin. In this practice, the volunteers are recruited from students who take aspirin with or without another agent that changes the urine to acidic or basic pH. They collect the urine during 3.5 hours after taking aspirin and analyze the metabolites of aspirin in the urine. Through this practice, the students understand how aspirin is metabolized and excreted to urine and also how the urine pH affects the excretion of the metabolites in urine. The students, who will need to administer medicine to patients as physicians, are expected to acquire basic aspects of pharmacokinetics and clinical trials through this practice.
Neurons containing melanin-concentrating hormone (MCH) localized in the posterior lateral hypothalamus and have a crucial role in rapid eye movement sleep (REMs) regulation. As MCH neurons also contain a variety of other neurotransmitters such as glutamate. However, the specific neurotransmitter responsible for REMs regulation is not known. We hypothesized that glutamate, the primary fast-acting neurotransmitter in MCH neurons, is necessary for REMs regulation. To test this hypothesis, we generated mice deleted vesicular glutamate transporter (Vglut2; necessary for synaptic release of glutamate) specifically from MCH neurons by crossing MCH-Cre mice (expressing Cre recombinase only in MCH neurons) with Vglut2flox/flox mice (expressing LoxP-modified alleles in Vglut2). We then studied the amounts, architecture and diurnal variation of sleep-wake states in baseline conditions. Next, we activated the MCH neurons lacking glutamate release using chemogenetic methods and tested whether these MCH neurons still promoted REMs. Our results indicate that glutamate in MCH neurons contributes to normal diurnal variability of REMs by regulating the levels of REMs during the dark period, but MCH neurons can promote REMs even in the absence of glutamate.
Orexin and melanin-concentrating hormone (MCH) neurons innervate each other and have opposite effects for rapid eye movement sleep (REMs) regulation. Narcolepsy patients appear abnormal REMs behaviors such as rapid transitions into REMs. The causal role of orexin neurons in narcolepsy is well established, but that of MCH neurons remains unclear. We hypothesized that in the absence of orexins, the effects of MCH on REMs can be unbalanced, potentially contributing to aspects of abnormal REMs observed in narcolepsy. To test this hypothesis, we generated MCH-Cre::OX-KO mice and characterized sleep-wake behaviors and cataplexy with chemogenetic activation and pharmacological inhibition of MCH signaling.
In mice lacking orexins, activation of the MCH neurons also increased abnormal intrusions of REMs manifest as cataplexy and short latency transitions into REMs (SLREM). Conversely, a MCH receptor 1 antagonist, SNAP 94847, almost completely eliminated SLREM and cataplexy in OX-KO mice. These findings affirm that MCH neurons promote REMs under normal circumstances, and their activity in mice lacking orexins likely triggers abnormal intrusions of REMs into non-REMs and wake, resulting in the SLREM and cataplexy characteristic of narcolepsy.