中脑导水管周围灰质内SP能神经元经孤束核调控咳嗽的机制研究

Substance P (SP) in the nucleus of the solitary tract (NTS) is closely related to central regulation of cough. Recent studies have documented that neurons in the periaqueductal gray (PAG) are activated in cough patients, but the roles of SP-ergic neurons in PAG and PAG-NTS projection in the cough regulation remain unclear. Our previous studies demonstrated that during the cough challenge of mice, the neuronal activity in NTS and PAG was enhanced, and the expression of SP expressions was upregulated. PAG could project to NTS, and the PAG-NTS pathway was involved in the cough regulation. Based on the previous studies, we plan to explore whether SP-ergic neurons in PAG can regulate cough via NTS. First, we will confirm the enhancement in neuronal activity during cough challenge. Subsequently, neurons in the PAG and NTS will be either excited or inhibited using a chemogenetics approach to observe cough reflex sensitivity (CRS). The role of the PAG-NTS projection in the regulation of CRS will be tested using retrograde tracing and chemogenetics. Finally, by employing a stereotaxic technique, the SP levels will be modulated to prove that the SP-ergic neurons in PAG can regulate CRS. The proposed research can provide a new target of central regulation of cough.

孤束核（NTS）内的P物质（SP）与咳嗽的中枢调控密切相关，近期研究发现咳嗽患者中脑导水管周围灰质（PAG）活动增强，但PAG内SP能神经元以及PAG-NTS投射在咳嗽调控中的作用尚不清楚。我们前期研究发现激发小鼠咳嗽时，PAG和NTS内神经元活动性明显增高，并且PAG内SP表达明显增多；PAG可发出纤维支配NTS，PAG-NTS投射通路参与咳嗽的调控。本课题在前期研究基础上，拟进一步探究PAG内SP能神经元能否通过NTS调控咳嗽。首先证实咳嗽时PAG和NTS的神经元活动增强，再通过化学遗传学技术激活/抑制PAG或NTS神经元活动，观察对咳嗽敏感性的影响；随后采用逆行神经示踪和化学遗传技术，验证PAG至NTS投射通路对咳嗽敏感性的调控作用；最后采用脑立体定位微量注射技术，干预PAG内SP的含量，证实PAG内SP能神经元对咳嗽敏感性的影响。通过本研究，有望发现咳嗽中枢调节的新靶点。

慢性咳嗽是各种呼吸道疾病的常见症状。然而，调节咳嗽过程的神经机制尚不清楚。前期研究发现激发小鼠咳嗽时，中脑导水管周围灰质(PAG)和孤束核(NTS)内神经元活动性明显增高，并且PAG内SP表达明显增多；PAG可发出纤维支配NTS，PAG-NTS投射通路参与咳嗽的调控。本课题进一步探究了PAG内SP能神经元能否通过NTS调控咳嗽。首先证实咳嗽时PAG和NTS的神经元活动增强，再通过化学遗传学技术激活/抑制PAG或NTS神经元活动，观察对咳嗽敏感性的影响；随后采用逆行神经示踪和化学遗传技术，验证PAG至NTS投射通路对咳嗽敏感性的调控作用；最后采用脑立体定位微量注射技术，干预PAG内SP的含量，证实PAG内SP能神经元对咳嗽敏感性的影响。通过本研究，我们发现外侧/腹侧导水管周围灰质(l/vlPAG)神经元被咳嗽激活，l/vlPAG神经元激活后咳嗽行为减少。此外，我们发现l/vlPAG神经元与孤束神经元形成抑制性突触。这些抑制投射在咳嗽过敏小鼠中较弱。重要的是，l/vlPAG gaba能神经元投射到NTS的激活减少了咳嗽行为。另外，我们发现l/vlPAG谷氨酸神经元的激活投射到延髓腹外侧区(RVM)而不是NTS促进了咳嗽行为。综上，我们的研究揭示了l/vlPAG-NTS是介导咳嗽高敏和慢性咳嗽的关键环路之一。