外侧下丘脑orexin神经元-丘脑室旁核通路对睡眠/觉醒周期的调控及机制研究

The brain exhibits two fundamentally functional states: sleep and arousal. According to our and other literature, it is suggested that the orexin system plays a key role in the sleep-wakefulness transition and the maintenance of the arousal state. However, the related neural circuitry underlying the arousal-promoting effect of orexin remains to be elucidated. On the basis of the previously finding that orexin neurons densely innervate paraventricular thalamic nucleus (PVT), one of the midline thalamic nucleus in the ascending activating system, this project will comprehensively use morphological, electrophysiological, light/pharmacogenetics, calcium imaging and EEG/EMG monitoring techniques, and systematically dissect the anatomic and functional connectivity between the orexin system and PVT at the molecular-cellular-circuitry levels. Then, we will clarify the role of orexin-PVT pathway in the regulation of the sleep/wake cycles, map the functional activity pattern of orexin fibers in PVT and explore its effect on thalamocortical network oscillations, with the aim to reveal novel neural mechanisms underlying the arousal-promoting effect of the orexin system.

睡眠/觉醒是脑的两个基本功能状态。本室和文献证实，觉醒肽Orexin系统在睡眠/觉醒的转换及觉醒状态的维持起关键作用，但其促觉醒效应的神经环路机制有待阐明。在前期报道orexin密集支配到上行激活系统中丘脑中线核团-丘脑室旁核（PVT）的基础上，本项目拟综合应用形态学、电生理学、光/药物遗传学、钙成像及脑/肌电监测等技术，在分子-细胞-环路水平上，系统解析orexin神经元-PVT解剖和功能联系；阐明orexin神经元-PVT通路在正常睡眠/觉醒中的调控作用；分析PVT内orexin纤维的活动模式及其对丘脑-皮层网络振荡的影响，旨在揭示orexin发挥促觉醒效应新的神经环路机制。

觉醒(wakefulness)是感觉、运动、认知和意识的基础。觉醒不良与嗜睡、木僵和昏迷状态密切相关。觉醒由一系列分布于脑干、下丘脑和皮层下脑区的神经元核团调控，如蓝斑(locus coeruleus, LC)去甲肾上腺素能神经元、外侧下丘脑(lateral hypothalamus, LH)觉醒肽(orexin)神经元和基底前脑(basal forebrain, BF)胆碱能神经元等。丘脑是觉醒系统背侧通路的主要组成部分，控制和处理觉醒信息传递至大脑皮层。丘脑室旁核(paraventricular thalamus, PVT)位于中线丘脑的背侧部，是非特异性投射丘脑的一部分。PVT参与调控觉醒状态依赖的行为，如成瘾与奖赏、摄食、应激和情绪等。但是，PVT在觉醒调控中的作用及其相关神经环路尚未得到鉴定。.在本研究中，我们发现PVT接受大量来自外侧下丘脑orexin神经元的输入，激活orexin-PVT通路诱发快速的觉醒转换。通过cfos染色、光纤记录和多通道实验，发现PVT神经元活动与觉醒状态密切相关。PVT活动在觉醒期高于NREM睡眠期和REM睡眠期，并且在由觉醒向睡眠转换时降低，而由睡眠向觉醒转换时增强。采用化学遗传学方法抑制PVT谷氨酸能神经元，发现觉醒时间明显下降，而NREM睡眠和REM睡眠时间增多。小鼠进入稳定的睡眠后，采用光遗传学方法激活PVT谷氨酸能神经元，可诱发快速的睡眠向觉醒的转换。总之，本研究证明PVT是重要的丘脑觉醒调控核团。.