延髓-迷走神经-肠脑环路在束缚-浸水应激致胃肠机能紊乱中的作用

Other stress usually lead to the activation of the hypothalamic-pituitary-adrenal (HPA) axis and sympathico-adrenal system. However, our preliminary studies showed that the hyperactivity of neurons in the parasympathetic nervous system was one of the primary central mechanisms of the gastric dysfunctions induced by the restraint water-immersion stress (RWIS). The enteric nervous system (ENS) directly regulates the gastrointestinal motility and secretion. Therefore, we postulate that the “the medullary dorsal vagal complex (DVC)-vagus nerve-enteric nervous system” circuit is involved in RWIS-induced gastrointestinal dysfunctions. During RWIS, whether the astrocytes are activated in the “DVC-efferent vagal nerve-enteric motor neurons” descending pathway? What types of motor neuron is activated in the wall of gastrointestinal tract? Is there a space-time pattern of neurons and astrocytes activation and a mutual regulation in DVC? what role does the DVC play in regulating the enteric motor neurons? Meanwhile, in the "gastrointestinal tract sensory neurons-vagal afferent nerve-DVC " ascending pathway, are sensory neurons in the gastrointestinal wall activated? Whether the sensory neurons in ENS and vagal afferent nerves regulate the activation of the medullary dorsal complex? In this study，we aim to address these questions by immunohistochemistry staining, western blotting and electrophysiological techniques and to provide an important experimental basis for the clinical new strages on the prevention and treatment of gastrointestinal dysfunction.

与其它应激致“下丘脑－腺垂体－肾上腺皮质轴”和“交感神经-肾上腺髓质系统”激活不同,我们前期发现副交感神经系统活动加强是束缚-浸水应激（RWIS）导致胃粘膜损伤和胃肠运动亢进的重要原因。胃肠运动和分泌等功能直接受控于肠神经系统（肠脑）。我们猜测“延髓迷走复合体-迷走神经-肠神经系统环路”参与了RWIS致胃肠功能紊乱。大鼠RWIS状态下，“延髓迷走复合体-迷走传出神经-胃肠壁运动神经元”下行通路中星形胶质细胞是否被激活？激活的胃肠壁运动神经元类型是什么？延髓迷走复合体对胃肠壁运动神经元如何调控？“胃肠壁感觉神经元-迷走传入神经-延髓迷走复合体”上行通路中，胃肠壁感觉神经元是否被激活？胃肠壁感觉神经元、迷走传入神经是否调节延髓迷走复合体的激活?本课题拟采用免疫组化、western boltting结合电生理等技术探讨这些问题，为临床上从外周、中枢方面探究防治应激性胃肠功能紊乱提供实验依据。

本项目基于脑干-胃肠神经系统轴内星形胶质细胞与神经元的相互作用，力图探究应激性胃肠功能紊乱中，胃肠道神经系统和脑干中枢神经系统的结构和功能的改变及分子机制。课题的研究为临床上从外周和中枢两方面探究防治应激性胃肠功能紊乱的新对策提供重要实验依据。.主要论点与论据：.1、束缚-浸水应激激活诱导脑-肠轴中神经元-星神经胶质细胞网络，参与应激性胃粘膜损伤：1）束缚-浸水应激明显增加室旁核、中缝大核、中脑导水管和脑干孤束核、迷走神经背核和胃肠肌间神经丛GFAP表达增加。2）抑制星形胶质细胞可降低神经元的活性，减轻胃粘膜损伤降低。.2、“肠-脑干”轴上行感觉通路，在束缚-浸水应激中被激活，参与了胃粘膜损伤过程：1）胃肠道中内脏感觉神经递质5-HT表达，在RWIS中明显增多。2）辣椒素特异性切断迷走传入神经，抑制了RWIS诱导脑干中神经元和星形胶质细胞的活性。 3）脑干孤束核内兴奋性Glu类神经元兴奋性升高，而抑制性GABA类神经元活性明显降低，核内注射谷氨酸受体抑制剂CNQX，明显减轻胃粘膜损伤。.3、“脑-肠”轴下行运动通路，在束缚-浸水应激中被激活，参与了胃粘膜损伤过程：1）迷走神经背核及胃肠道肌间神经丛GFAP、Fos和ChAT表达量增加，而NOS表达量明显减少。2）阿托品明显降低胃肠肌间神经丛中的GFAP和Fos表达，减轻胃粘膜的损伤。.4、下丘脑室旁核-脑干迷走神经复合体神经回路中促肾上腺皮质激素释放激素（CRF）和催产素能神经元被激活参与了胃粘膜损伤过程：1）束缚-浸水应激明显增加室旁核内CRF 和OXT及迷走复合体内CRFR 和OXTR受体的表达。2）侧脑室注射CRF明显降低肠道中的升骨架蛋白Claudin-1、闭合蛋白Occludin和胃壁中的MUC5AC的表达显著降低，而注射OXT，明显增加Claudin 1、Occludin以及胃黏蛋白5AC的表达