脑干GABA能神经元对眼压调控作用的研究

Glaucoma is the leading cause of irreversible blindness in the world. Elevated and huge fluctuation of intraocular pressure (IOP), are regarded as the most important risk factors for glaucomatous visual field loss. Although numerous studies have shown that the autonomic brain is involving in intraocular pressure regulation, the possible mechanism is still a mystery. Our team have revealed that the brainstem, a key node of central autonomic nervous system, is involving in the regulation of intraocular pressure, and brainstem GABAergic receptors expressed increasingly. Gamma-Aminobutyric acid(GABA) is a chief inhibitory neurotransmitter in the mammalian central nervous system, which could modulate all stages of mechanoreception.Evidences indicated abnormal GABA pathway exsited in POAG patients, and a significant IOP increasing was found when GABAA receptor antagonist was used. Therefore, we propose the hypothesis: The GABAergic neurons in the brainstem play an important role in IOP regulation, and its dysfunction may lead into elevated intraocular pressure and glaucoma. In order to verify the hypothesis, we will employ multimodal funtional magnetic resonance technology to investigate the IOP and GABA concentration in primary open angle glaucoma patients. We further obseve the brainstem GABAergic neurons morphologic changes, and explore its possible role in IOP regulation and possible mechanism through animal experiment.This project is contribute to understanding the pathogenesis of glaucoma and may provide some evidence of new target to glaucoam therapy.

青光眼是世界上第一位不可逆性致盲性眼病。眼压的升高和异常波动，是青光眼视功能丧失的最重要危险因素。大量研究显示，脑自主神经网络参与眼压调控，可是具体机制仍不清楚。我们前期研究通过功能磁共振技术及动物实验证实脑干作为脑自主神经网络的重要节点与眼压相关，自发性青光眼小鼠脑干GABA受体表达改变。GABA作为重要的抑制性神经递质，可以影响压力感受器电活动强度，从而调节神经元的敏感性和信息传递。研究显示POAG患者GABA通路代谢异常，而给予GABAA受体拮抗剂后眼压升高。因此我们提出假说：脑干GABA能神经元通过调节压力感受器参与眼压调控，其功能紊乱导致眼压改变。本项目拟通过磁共振探索POAG患者眼压与脑干GABA含量的关系，并观察高眼压动物模型脑干GABA能神经元形态学变化，利用电刺激和药物干预探索脑干GABA能神经元在眼压调控中的作用机制，为青光眼的中枢发病及临床治疗新靶点提供依据。

青光眼是世界上第一位不可逆性致盲性眼病。眼压的升高和异常波动，是青光眼视功能丧失的最重要危险因素。大量研究显示，脑自主神经网络参与眼压调控，可是具体机制仍不清楚。研究显示GABA作为重要的抑制性神经递质，可以影响压力感受器电活动强度，从而调节神经元的敏感性和信息传递。我们前期研究通过功能磁共振技术及动物实验证实脑干和桥脑作为脑自主神经网络的重要节点与眼压相关，因此我们提出假说：脑干和端脑的GABA能神经元通过调节压力感受器参与眼压调控，其功能紊乱导致眼压改变。为了证实假说，本项目组1.收集了22名POAG患者及24名正常人的静息态脑功能磁共振成像数据，对蓝斑区及其相关脑功能区域进行数据分析，发现POAG病人蓝斑区的低频振幅(ALFF)值较对照组显著增高，蓝斑区与额叶、岛叶的功能连接(FC)较对照组显著下降，蓝斑区与海马旁回的FC较对照组则明显升高。2.通过对比观察巩膜上静脉结扎联合烧灼法青光眼模型大鼠（12只）和相同数量相同月龄正常对照大鼠、自发性青光眼模型DBA/2J小鼠（10只）和相同数量级相同月龄的C57小鼠的区别，发现青光眼模型鼠蓝斑核内TH和DβH含量较对照组显著减少，且DBA/2J小鼠蓝斑核内细胞凋亡较对照组显著增多。3.通过巩膜上静脉结扎联合烧灼法构建慢性高眼压动物模型（每组8只），其中一组通过脑立体定位仪于下丘脑弓状核注射兴奋性氨基算鹅膏蕈氨酸后，眼压升高不明显，且眼压水平显著低于慢性高眼压组。4. 对DBA/2J与正常C57小鼠的脑片进行了免疫组织化学染色，从免疫组织化学染色中可以发现与免疫荧光相同的趋势，即 DBA/2J转基因小鼠中活化的GABA-A与GABA-B受体比正常的C57 小鼠比，表达明显增高。5.在慢性高眼压模型大鼠行弓状核内注射GABA-A受体的拮抗剂(gabazine)及GABA-B受体的拮抗剂(CGP55845)，打药组的眼压较对照组明显降低（P<0.05），视网膜神经节细胞数量较对照组增加（P<0.05），下丘脑弓状核GABA表达量降低（P<0.05）。这些结果提示脑干及桥脑中的GABA能神经元参与眼压的调控。