海马齿状回galanin及其受体促进海马神经发生、改善抑郁状态的机制研究

Depression is a high prevalence mental disorder which severely threats human health. Stress and genetic vulnerability are the main reasons leading to the onset of depression. In CNS, hippocampal neurons are most sensitive to stress, and stress induced hippocampal neurogenesis failure is an important feature of depression. Containing 29/30 amino acid neuropeptide galanin (Galanin,Gal) is widely distributed in the peripheral and central nervous system and plays a variety of biological effects through three G protein-coupled receptors (GalR1-3) .Recent studies have shown that in the adult mammalian hippocampus dentate gyrus granular layer, GalR mRNA expression is detected. This zone is well known as related with neurogenesis which infers Gal may be involved in neurogenesis in hippocampus. It's been found in our former studies that positive galanin neurons are mainly distributed in dentate gyrus and microinjection of galanin in this zone could induce increased BrdU staining which represented neurogenesis. However, it is still unknown whether depressive symptoms can be improved through Gal induced hippocampal neurogenesis. In this project, Gal expression pattern in every developmental stage in dentate gyrus will be examined in order to find out how it affects neurogenesis. At the meantime, through primary cultured hippocampal neural stem cells, we will eliminate signal transduction pathways concerning Gal induced neurogenesis. Taking the advantage of chronic unpredicted stress model, we intend to observe Gal receptor expression change and neuronal cell proliferation in dentate gyrus,and clarify the underlying mechanism of Gal's fuctions in hippocampal neural regeneration in depressive state.This project will provide new sights and direction in clinical antidepressant treatment.

抑郁症是一种常见精神障碍，严重威胁人类健康。应激与遗传易损性是导致抑郁症发病的主要原因，海马对应激最敏感，应激导致海马神经发生下降是抑郁症的特征。甘丙肽(Gal)为含有29/30个氨基酸的神经肽，通过三种G蛋白偶联受体发挥多种生物学效应。研究发现GalR mRNA在神经发生相关的齿状回颗粒下区表达，表明Gal可能参与神经发生。本研究组前期发现Gal阳性神经元主要分布于海马齿状回,且将Gal海马局部注射发现BrdU阳性神经元增加,但Gal能否通过影响海马神经发生改善抑郁症状尚不得而知。为此，本项目拟观察Gal是否表达于神经元发生至成熟的各阶段及其对神经发生的影响；原代培养海马神经干细胞，探讨Gal影响神经发生的信号转导通路；建立慢性不可预见性应激模型，观察抑郁状态下齿状回Gal及其受体的表达变化及神经发生情况，进而明确Gal在海马神经发生中的作用机制，为临床抗抑郁治疗提供新的靶点和方向。

海马是记忆、行为、情感、应激反应的高级中枢，研究甘丙肽及其受体在焦虑抑郁小鼠海马的表达，进一步明确其是否通过影响海马的神经发生而参与对焦虑抑郁的调控。.本项目首先通过原位杂交技术明确甘丙肽及受体在成年雌性小鼠海马的表达，并通过构建成年雌性小鼠CUMS模型，明确焦虑抑郁样小鼠海马神经增殖（Brdu+及Ki67+）、c-Fos的表达及甘丙肽及受体在海马小鼠海马中的表达及作用；再进一步明确甘丙肽及受体是否通过调节海马的神经化生来参与调节焦虑抑郁水平，为抑郁症的治疗提供新策略。.我们的结果显示甘丙肽及GalR1、GalR2在雌性成年C57BL/6J小鼠海马腹Hilus区有表达，GalR3未见阳性信号。在CUMS组成年雌性小鼠海马齿状回的神经增殖（Brdu+）减少，c-FOS蛋白明显增加。在CUMS组小鼠中海马甘丙肽及其受体-1mRNA水平增高明显，而甘丙肽受体-2及受体-3 mRNA表达无明显变，可知甘丙肽及其受体-1与成年雌性C57BL/6J小鼠的焦虑抑郁样行为有关。将CUMS小鼠随机分三组，分别给与生理盐水、（20mg/kg）氟西汀、（0.5mg/kg）galnon处理7天，结果显示，发现氟西汀组小鼠的抑郁水平下降，焦虑水平降低不显著，生理盐水组焦虑抑郁水平改变不显著，galnon组小鼠的焦虑水平增加，抑郁增加不显著。在原代培养神经球中，分别给与0nM、10nM、100nM、1uM的甘丙肽受体-1激动剂M617，明确甘丙肽受体-1对神经增殖（Brdu+/H+）的作用，结果发现不同浓度的M617对干细胞的增殖影响无统计学差异。.结论：甘丙肽、GalR1及GalR2主要分布在小鼠海马的腹侧Hillus区；在雌性C57BL/6J小鼠中，海马甘丙肽及GalR1的增加可能与焦虑抑郁样行为有关，且甘丙肽非特异性激动剂galnon主要参与焦虑水平的调解；.抑郁样小鼠海马新生神经干细胞增殖减少、c-FOS蛋白增加；GalR1可能不直接参与调节神经干细胞的增殖。