Orexin对苍白球神经元兴奋性的调控及其在帕金森病运动障碍发生过程中作用的研究

Orexin is a hypothalamic neuropeptide which facilitates locomotor activity. Much evidence indicates that orexin levels decrease significantly in both Parkinson’s disease patients and animal models. However, little is known about the relationship between the decrease of orexin and the parkinsonian motor deficits. It is well known that the globus pallidus is a key structure in the indirect pathway of the basal ganglia circuit. Recent studies have indicated that the electrical activities of two different types of pallidal neurons are closely related to motor control and Parkinson’s disease. Morphological studies have shown that the globus pallidus receives orexinergic innervation arising from the hypothalamus. Furthermore, orexin receptors are expressed in the globus pallidus. However, up to present, the modulation of orexin on the excitability of the globus pallidus neurons and the possible involvement of pallidal orexin in parkinsonian motor deficits are unknown. Therefore, in the present study, we propose to examine the modulation of orexin on the globus pallidus under both normal and parkinsonian states by in vivo and in vitro electrophysiological recordings, photogenetics, transgenic animals, immunofluorescence technique and behavioral tests. Firstly, we will study the electrophysiological effects and mechanisms of orexin on different types of pallidal neurons. Secondly, we will compare the electrophysiological effects of orexin and the expression of orexin and orexin receptors between normal and parkinsonian animals. Finally, we will study whether orexin could alleviate parkinsonian motor deficits through its modulation on the excitability of globus pallidus neurons. The present study will provide a theoretical and experimental evidence for occurrence, prevention and cure of parkinsonian motor deficits.

Orexin是下丘脑神经肽，可易化大鼠自发活动。有报道，帕金森病患者及动物模型脑内Orexin水平明显降低，但与运动障碍是否相关尚不清楚。苍白球是基底神经节间接环路的重要核团。新近研究揭示，苍白球不同类型神经元的电活动在机体运动调控及帕金森病中发挥重要作用。苍白球接受下丘脑的Orexin能纤维支配，并表达Orexin受体。然而，Orexin对苍白球神经元兴奋性的调控及其在帕金森病运动障碍发生中的作用至今不明。为此，本研究拟采用在体及离体电生理记录、光遗传学、转基因动物、免疫荧光组织化学和行为学等手段，从多角度深入探讨Orexin对苍白球不同类型神经元的电生理效应及其机制；帕金森病状态下，苍白球Orexin的电生理效应及Orexin和受体的表达是否发生改变；Orexin可否通过调控苍白球神经元兴奋性从而改善帕金森病运动障碍症状。本研究将为帕金森病运动障碍的发生及防治提供新的理论和实验依据。

Orexin是下丘脑神经肽，可易化大鼠自发活动。有报道，帕金森病患者及动物模型脑内orexin水平明显降低，但与运动障碍是否相关尚不清楚。苍白球和黑质是基底神经节间接环路的重要核团，其神经元的电活动在机体运动调控及帕金森病中发挥重要作用。苍白球和黑质接受下丘脑的orexin能纤维支配，并表达orexin受体。然而，orexin对苍白球和黑质多巴胺能神经元兴奋性的调控及其在帕金森病运动障碍发生中的作用至今不明。为此，本研究采用多种实验技术，从多角度深入探讨orexin对苍白球和黑质神经元的电生理效应及其机制，以及orexin可否通过调控神经元兴奋性从而改善帕金森病运动障碍症状。研究结果显示，苍白球给予外源性orexin-A或orexin-B可通过激活OX1型受体和OX2型受体，显著增加神经元兴奋性。机制探讨揭示PLC和PKC等信号通路以及L型钙离子通道和钠钙交换体参与orexins对苍白球神经元兴奋性的调控。OX受体的表达存在年龄相关性。行为学研究揭示，苍白球给予orexins可增加正常大鼠运动行为，且苍白球给予orexins可明显改善帕金森病模型小鼠的运动障碍症状。进一步研究表明，orexin-A可通过激活OX1受体降低MPTP帕金森病模型小鼠黑质多巴胺能神经元损伤，改善其运动障碍症状和空间学习和记忆能力。黑质多巴胺能神经元BDNF蛋白表达的增加参与orexin-A对多巴胺能神经元的保护作用。细胞水平的研究表明，orexin-A通过PKC和PI3K通路的活化增加SH-SY5Y多巴胺能细胞BDNF表达，从而对MPP+诱导的细胞损伤发挥保护作用。而orexins对黑质多巴胺能神经元自发放电的兴奋效应可能是其改善帕金森病模型动物运动障碍的另一机制。本研究为脑内orexin递质系统作为帕金森病治疗的新靶点提供了有力的理论和实验依据，具有重要的科学意义和社会效益。