orexin在不同睡眠觉醒状态下对颏舌肌的作用及机制研究

Obstructive sleep apnea (OSA) is a high risk factor which results in cognition damage, traffic and work incidents, myocardial infarction, stroke and sudden death. Its pathogenesis is not clear. But evidencs highlighted that its pathogenesis was linked to suppression of genioglossus muscle (GG) activity in sleep. Orexin is a neuropeptide secrected by hypothalamus. Orexin receptor distributes in hypoglossal nucleus (HN) which controls GG activity. Our previous work observed that both exogenous and endogenous orexin increased GG activities by HN in anesthetized rats. On the base of these results, we want to investigate the effect of endogenous orexin on GG in sleep/wake states. We hypothesized that suppression of orexin neurons in sleep could induce GG activity to decrease and this could be a new pathogenesis of OSA. To verify the hypothesis, freely moving animals will be used as objects. We will observe effect of endogenous orexin on GG by use of electrophysiological techniques. And orexin receptor and signal transduction pathway will also be observed at the organ and cell levels by use of recording nerve rootlet and patch clamp. The objective of this study is to detect new pathogenesis of OSA and provide new target for its prevention and cure.

阻塞性睡眠呼吸暂停（OSA）是导致认知损伤、交通和工伤事故、心梗、甚至中风和猝死的高危因素。其确切机制尚未阐明，多认为与睡眠期颏舌肌活动的减弱有关。orexin是下丘脑分泌的一种神经肽，支配颏舌肌活动的舌下运动神经核（HN）分布有orexin受体。我们的前期工作发现在大鼠麻醉状态下外源性和内源性orexin 均能通过HN增强颏舌肌活动。在此基础上，本项目将探讨orexin对大鼠不同睡眠觉醒状态下颏舌肌的作用。我们推测睡眠时orexin神经元活动抑制可诱导颏舌肌活动减弱，这可能是OSA的一个新机制。为证实这一假说，我们以清醒自由运动动物为研究对象，采用电生理学技术，观察内源性orexin改变时对颏舌肌功能的影响；另外在器官、细胞水平分别采用神经根放电记录和膜片钳等技术，研究 orexin调控颏舌肌活动的受体及信号传导通路，以期探寻OSA发病的新机制，为其防治提供新靶点。

阻塞性睡眠呼吸暂停（Obstructive sleep apnea, OSA）是导致认知损伤、交通和工伤事故、心梗、甚至中风和猝死的高危因素。其确切机制尚未阐明，多认为与睡眠期颏舌肌活动的减弱有关。orexin 是下丘脑分泌的一种神经肽，支配颏舌肌活动的舌下运动神经核（hypoglossal nucleus, HN）分布有orexin 受体。我们发现外源性和内源性orexin均能通过作用于SD大鼠HN来增强颏舌肌的肌电活动。在自由运动大鼠上观察到内源性orexin释放减少时在清醒期、慢波睡眠期和快眼动睡眠期颏舌肌的肌电活动均出现不同程度的减弱，尤其是慢波睡眠期间；另外在器官、细胞水平采用全细胞膜片钳技术，发现orexin A增加了离体新生SD大鼠舌下运动神经元(hypoglossal motoneurons,HMNs)放电频率，并降低其膜电位。两种orexin受体（orexin receptor, OXR）拮抗剂阻断了orexin A引起的HMNs的放电频率增加和膜的去极化。在体实验中，也发现在成年大鼠HN微量注射两种亚型的orexin受体拮抗剂后颏舌肌的肌电活动明显减弱，尤其是呼吸相关的颏舌肌活动。这些结果提示两种亚型的orexin受体均参与了orexin 对颏舌肌活动的调控。离体分离培养新生大鼠HMNs，并进行活细胞钙测定，发现orexin A可以增加舌下运动神经元内的Ca2+浓度。以上研究结果说明睡眠时脑内某种机制对orexin 神经元活动的抑制可诱导颏舌肌活动减弱，这可能是OSA发病的一个新机制，希望为其防治提供新靶点。