Orexin能神经系统对巨细胞网状核在REM睡眠期间介导的肌张力调控的作用研究

The rapid eye movement (REM) sleep behavior disorder (RBD) occurs exceed 60% of patients with deficit of orexin nervous system. RBD is a sleep deficiency characterized by the absence of normal muscle atonia in REM sleep, which plays an important role in the stabilization and maintenance of this period of sleep. Intriguingly, our recent and ongoing studies have revealed that in wake state, orexinergic nervous system promotes the regulation of muscle tone through the direct innervation and excitation of several related central motor structures. Orexinergic neurons indeed active in REM sleep and in several brain regions that have been investigated, the orexin release increases in REM sleep. However, whether the same mechanism as in wake state operates in REM sleep state for orexinergic nervous system to regulate the muscle tone still remains enigmatic. Therefore, the gigantocellular reticular nucleus (Gi), which is directly involved in the negative regulation of muscle tone in REM sleep, is planned to put into investigation to solve this subject. In this project, we will use several multi-disciplinary techniques including the molecular biological, morphological, electrophysiological, pharmacological, and behavioral methods to observe the action of orexinergic nervous system on the activity of the Gi neurons and investigate the special underlying regulation mechanism in REM sleep. Subsequently, the influence on the Gi-related muscle tone, especially the Gi-mediated muscle atonia in REM sleep, induced by the effect of orexinergic nervous system on the Gi will be determined. The physiological significances and the possible connections with the related sleep deficiencies of the influence will be discussed. The outcomes from this project will provide some new understandings about the underlying nervous mechanisms in the stablization and maintenance of the sleep state and possibly some new directions for the appropriate intervention of related sleep deficiencies.

高达60%的orexin缺陷病人存在快速眼动睡眠（REM）行为障碍（RBD），表现为REM期间正常肌张力缺失功能的不全，对其稳定和维持产生影响。我们先前的研究揭示，orexin能神经系统通过直接兴奋相关中枢运动结构，在觉醒期间的肌张力调控中发挥重要促进作用，而orexin能神经元在REM中也有放电活动，此时orexin含量也确实在一些已测量过的脑区升高；但是否有同样的机制对REM期间的肌张力调控发挥作用尚不清楚。本项目选择与肌张力负向调控直接相关的巨细胞网状核（Gi）为研究对象，系统研究orexin能神经系统对Gi神经元的兴奋性作用和REM期间特异性的调节机制；在此基础上，分析orexin在Gi的肌张力调控功能，特别是Gi在REM中介导的肌张力缺失中的影响，并探讨这些影响的生理意义及可能与相关睡眠障碍之间的关系，以期深入理解睡眠状态稳定与维持的神经机制，也为干预相关睡眠障碍提供新的思路。

高达60%的orexin缺陷病人存在快速眼动（REM）睡眠行为障碍（RBD），表现为REM睡眠期间正常“肌张力缺失（atonia）”功能的不全，对其稳定和维持产生影响。虽然先前的研究已经揭示，orexin神经元在REM睡眠中也有放电活动，但对于其是否与REM睡眠期间的肌张力调控功能相关以及其中可能的神经机制，尚很不清楚。因此，本项目通过联合运用离体/在体电生理学、组织化学、神经环路追踪、神经药理学、光遗传学、行为学等技术手段，首先观察了orexin神经系统在REM睡眠期间的特定活动模式，继而分析了orexin通过作用于背侧蓝斑底核（SubCD）-巨细胞网状核（Gi）这一脑干中的REM睡眠期肌张力控制网络的神经机制，对REM睡眠中肌张力缺失功能的影响。我们的结果首先表明，orexin神经系统作为一个整体，在REM睡眠期间仅有中等程度的活动，但是特异投射到SubCD的orexin神经元亚群则表现出REM睡眠相关的强烈激活，揭示了orexin系统参与REM睡眠中肌张力控制功能的基础。进一步的研究揭示，orexin可以作用于SubCD-Gi网络中的神经元，影响其活动。对于SubCD神经元，orexin除直接兴奋其中的2/3表达orexin受体的神经元外，还通过增强SubCD神经元之间的电突触联系效率，将其兴奋效应高效、广泛地扩布到整个SubCD神经元网络，并在此过程中增强SubCD神经元网络的同步化放电活动程度、增强其传出效率，从而发挥稳定REM睡眠期脑电活动和肌张力下调功能的新机制。对于Gi神经元，orexin也可通过直接的突触后orexin 1型和2型受体，及其耦联的非选择性阳离子通道（NSCC）的激活，发挥兴奋效应，参与REM睡眠期的肌张力下调功能。进一步考察orexin神经系统对SubCD-Gi网络同时的兴奋性效应导致肌张力下调的生理意义，首先发现在REM睡眠期间SubCD与Gi存在传出信息的交互，表现为两个脑区局部场电位振荡活动的耦联，进而影响了整个网络的神经元放电传出，提示共同协调参与REM睡眠期的肌张力控制功能，orexin对这一过程统一的调控机制值得深入研究。以上四方面的研究以脑干中SubCD-Gi神经网络为对象，深入探讨了orexin系统支配及影响REM睡眠中肌张力控制功能的新机制，对于了解相关疾病（如，RBD）的病理机制及干预靶点有参考意义。