海马GABAA受体α6亚单位在慢性不可预见性应激导致雄性大鼠抑郁中的作用

The changes of GABAergic inhibitory system has been reported in depression and anti-depression treatment. However, the effects of chronic stress on the expression and functions of GABAA receptors are still not clear. The roles of GABAA receptors in depression induced by chronic stress are still unknown. In preliminary experiment, we found the protein level of Gabra6 was decreased in hippocampus from chronic unpredictable stress (CUS) induced depression model of rats. RNAi induced down regulation of Gabra6 in hippocampus can induce depressive-like behaviors in normal rats. Gabra6 take important parts in modulation of the GABAergic inhibitory synapse transmission in hippocampus CA1 pyramidal neurons. These findings inferred the down regulation of Gabra6 in hippocampus could be the major pathophysiologic process in CUS induced depression. In order to test the hypothesis of “CUS → Gabra6 down regulation → changes of GABAergic inhibitory synaptic transmission → depression”, we plan to use the western-blot, RT-PCR, immunofluorescence, behavioral test and path-clamp technique to explore the effects of CUS on the expression of Gabra6 subunits within hippocampus and Gabra6-regulated GABAergic inhibitory synaptic transmission, and to identify the roles of Gabra6 subunits and Gabra6-regulated GABAergic inhibitory synaptic transmission in the process of CUS induced depression by modulating their expression or activation. The proposed project will help us to answer whether the protein level of hippocampus Gabra6 subunits and its modulation of GABAergic inhibitory synaptic transmissions are involved in CUS induced depression. This research will provide new evidence for the mechanism of depression.

抑郁症发生及抗抑郁治疗过程中存在GABA能抑制系统改变，慢性应激对GABAA受体表达和功能的影响及其在抑郁症发生中的作用尚不清楚。申请者发现慢性不可预见性应激（CUS）导致大鼠抑郁，海马Gabra6蛋白水平降低；RNAi技术下调海马Gabra6表达导致正常大鼠抑郁；GABAA受体α6亚单位（Gabra6）参与调节CA1区锥体细胞中的GABA能抑制性突触传递。本项目提出“CUS→Gabra6表达下调→GABA能抑制性突触传递改变→抑郁”假说，拟采用免疫印迹、RT-PCR、免疫荧光、行为学及膜片钳等方法，研究CUS对海马Gabra6表达分布及其参与的GABA能抑制性突触传递的影响，通过改变Gabra6表达或功能，探讨其参与调节的GABA能抑制性突触传递在CUS导致抑郁中的作用。本项目从Gabra6表达改变影响抑制性突触传递的角度阐释CUS导致抑郁的机制，为探讨抑郁症的发病机制提供新的证据。

抑郁症发生及抗抑郁治疗过程中存在GABA能抑制系统改变，慢性应激对GABAA受体表达和功能的影响及其在抑郁症发生中的作用尚不清楚。本项目研究发现慢性不可预见性应激导致大鼠抑郁，并进一步优化模型条件，证实适当降低初始应激年龄有助于抑郁动物模型的建立。在此基础上发现慢性应激下调大鼠海马GABAA受体α6亚单位（Gabra6）mRNA和蛋白水平，海马Gabra6蛋白主要分布于中间神经元，提示慢性应激主要下调中间神经元中的Gabra6蛋白表达。Gabra6选择性拮抗剂使海马CA1区锥体神经元中的mIPSC频率增高，提示Gabra6参与调节锥体神经元中的GABA能抑制性突触传递。慢性应激使海马CA1区锥体神经元中的mIPSC频率增高，提示慢性应激通过下调海马Gabra6表达使锥体神经元中的GABA能抑制性突触传递增强。RNAi技术下调海马Gabra6蛋白表达使正常大鼠蔗糖偏爱水平降低，新环境进食抑制实验中的进食潜伏期延长，提示下调海马Gabra6蛋白表达导致正常大鼠抑郁；下调海马Gabra6蛋白表达使海马CA1区锥体神经元中的mIPSC频率增高，提示Gabra6表达下调及其参与调节的GABA能抑制性突触传递增强在抑郁的发生中发挥重要作用。抗抑郁药物氯米帕明（Clom）使抑郁大鼠蔗糖偏爱水平升高，新环境进食抑制实验中的进食潜伏期缩短，提示Clom能够缓解大鼠抑郁症状；Clom上调抑郁大鼠海马Gabra6蛋白表达，并使海马CA1区锥体神经元中的mIPSC频率降低，提示Clom通过上调Gabra6使GABA能抑制性突触传递下降，从而缓解抑郁症状，进一步证实Gabra6表达及其参与调节的GABA能抑制性突触传递改变在抑郁中发挥重要作用。本项目证实“慢性应激→Gabra6表达下调→GABA能抑制性突触传递增强→抑郁”假说，从Gabra6表达改变影响抑制性突触传递的角度阐释慢性应激导致抑郁的机制，为探讨抑郁症的发病机制提供新的证据。