觉醒肽orexin对脑桥尾侧网状核运动功能的影响和机制研究

In general, the correct execution of motor function must occur in the proper wakefulness state. Although the sleep/wakefulness state is a complex nervous process and controlled by many nervous systems, intriguingly, as a key structure underlying the occurrence and retention of the wakefulness state, central orexinergic nervous system may have a very substantial relationship with the motor control, since its deficiency in humans, dogs, and rodents results in cataplexy, a motor deficit characterized by sudden loss of muscle tone and collapse. Our recent study has revealed that central orexinergic system participates in the central vestibular-mediated motor control through a direct action on the lateral vestibular nucleus (LVN), a subnucleus of the central vestibular nuclear complex. The central vestibular-mediated motor control takes an active part in the regulation of balance and posture in a feedback fashion. In order to fulfill the motor function, however, the feedforward motor control mediated by reticulospinal descending system must coordinate with the vestibular-mediated feedback motor control to orchestrate an integrated regulation of balance and posture. Whether there is a direct modulation of central orexinergic system on the reticulospinal descending system-mediated motor control remains unknown. Therefore, the nervous circuitry of the caudal pontine reticular nucleus (PnC), a part of the reticulospinal descending system, is planed to put into investigation to solve this subject. In this project, we will use several multi-disciplinary techniques including the molecular biological methods, morphological methods, electrophysiological methods, pharmacological methods, and behavioral tests to observe the action of central orexinergic system on the activity of the PnC circuitry and investigate the detailed underlying mechanism. Subsequently, the influence on the PnC-related motor behaviors induced by the effect of central orexinergic system on the PnC circuitry's activity will be determined. The physiological significances and the possible connections with the related motor deficit of the influence elicited by central orexinergic on PnC-related motor functions will be discussed. The outcomes from this project will provide some new understandings about the underlying nervous mechanisms in the regulation of the motor control by the wakefulness state and possibly some new directions for the appropriate intervention of related motor deficits.

良好的运动功能状态依赖于良好的机体觉醒状态。中枢orexin能神经系统是机体觉醒状态发生和维持的关键性结构，它的缺陷将导致猝倒症这一重大运动障碍，表明其与运动控制密切相关。我们最近的一部分研究揭示，中枢orexin能神经系统通过直接作用于前庭外侧核而参与姿势调节过程中中枢前庭系统介导的反馈性运动控制。然而，网状脊髓下行系统介导的前馈性运动控制对姿势调节也是不可或缺的。本项目拟选择网状脊髓下行系统中脑桥尾侧网状核环路为研究对象，采用分子生物学、形态学、神经电生理、神经药理学和行为学等技术，研究中枢orexin能神经系统对脑桥尾侧网状核环路活动的作用和机制；在此基础上，分析中枢orexin能神经系统在脑桥尾侧网状核运动功能中的影响，并探讨这些影响的生理意义以及可能与相关运动障碍的病理机制之间的关系，以期进一步深入理解觉醒状态对运动控制功能的神经调控机制，也为干预相关运动障碍提供新的思路。

良好的运动功能状态依赖于良好的机体觉醒状态。中枢orexin 能神经系统是机体觉醒状态发生和维持的关键性结构，它的缺陷将导致猝倒症这一重大运动障碍，表明其与运动控制密切相关。运动是在神经系统中多种运动相关神经元精密协同下完成的一项基本生理功能。其中，脑桥尾侧网状核（caudal pontine reticular nucleus, PnC）作为重要的“桥梁”运动结构，其中的网状脊髓神经元广泛整合来自皮层、中脑、脑干和小脑的不同运动信息并直接调控脊髓运动神经环路活动，发挥重要运动控制功能。因此，采用分子生物学、形态学、神经电生理和神经药理学相结合的手段，我们首先观察了orexin对PnC网状脊髓神经元的电生理效应及机制。结果表明orexin通过激活突触后膜上orexin 1型和2型受体，开放下游耦联的非选择性阳离子通道，引起PnC网状脊髓神经元直接的兴奋性反应。同时，orexin还选择性抑制了传递到PnC网状脊髓神经元的兴奋性突触传入，而不影响抑制性突触传入，其机制为通过激活突触后膜上orexin 1型和2型受体，动员胞内的内源性大麻素合成系统，使得内源性大麻素合成释放并特异性作用于兴奋性突触前末梢上的大麻素1型受体（CB1R），发挥抑制递质释放的功能。行为学水平的运动控制功能研究进一步表明，orexin对PnC网状脊髓神经元的突触后及突触前调控效应参与了对PnC介导的惊跳运动（startle）的调节，表现为通过其突触前效应滤过传入的噪声信息而提高startle反应的阈值，但该运动行为一旦发生，就通过突触后效应增强startle反应的强度，从而使得机体对有效信息引发的PnC运动控制功能更为高效准确的执行。利用orexin基因敲除小鼠、orexin-cre小鼠、及ArchT/EGFP- floxed-STOP小鼠等动物模型，我们拟进一步证明orexin对PnC网状脊髓神经元及其介导运动控制功能的作用及机制在整体水平的生理意义，以及可能与相关运动障碍病理机制的关系，该部分扩展研究正在进行中。此外，我们还扩展研究了另一觉醒系统——中枢去甲肾上腺素能神经系统对PnC的作用，证明PnC活动接受广泛的觉醒相关信息调控，且这些调控作用通过不同的机制统一协同了机体觉醒状态与运动控制功能。