外侧缰核钙通透AMPA受体介导的兴奋性传递在调节帕金森病相关抑郁中的分子机制

The lateral habenular nucleus (LHb) is an epithalamic region with a crucial role in the regulation of monoaminergic systems in the brain. The balance between excitatory and inhibitory transmission in the LHb plays an important role in the regulation of depression and antidepressant treatments. Parkinson’s disease (PD)-related depression is a mostly encountered non-motor feature of PD, and is a significant risk factor for the development of PD; however, the pathogenesis of PD-related depression is poorly understood. On the basis of our previous studies, the aim of the present study is to investigate: (1) the effects of LHb calcium-permeable AMPA receptors (CP-AMPARs) in the regulation of depressive-like behaviors measured by sucrose preference and forced swim test in rats with unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta, and the changes in the firing activity of LHb neurons by in vivo electrophysiological recordings; (2) the proportion of glutamate/GABA release from the presynaptic terminals in the LHb after light stimulation of ChR2-YFP fibers that project from the entopeduncular nucleus or ventral tegmental area to the LHb, and the effects of LHb CP-AMPARs in the release of monoamines of the medial prefrontal cortex (mPFC) in rats with PD-related depression measured by microdialysis and reverse-phase high performance liquid chromatography with electrochemical detection; (3) the expression of CP-AMPAR GluR1, 3 and 4 subunits and the phosphorylated subunits in the synaptic and extrasynaptic sites of the LHb in rats with PD-related depression by real time PCR and Western-blot analyses, and the changes in the expression of these subunits after the intra-LHb injection of calcium/calmodulin-dependent kinase type II inhibitor; (4) the effects of LHb CP-AMPARs in the changes in the neuronal activity of the project neurons in limbic brain regions, including the mPFC, ventral hippocampus and basolateral amygdaloid nucleus, by double-labeling immunofluorescence histochemistry of co-expression of c-Fos and the neurons in rats with PD-related depression. These studies will illustrate that the action and mechanism of LHb CP-AMPAR-mediated excitatory transmission in the regulation of PD-related depression. In addition, these studies also help to bring understanding about the neurobiology of other psychiatric illnesses, cognitive impairments and drug addiction.

外侧缰核（LHb）是调节脑内单胺能递质系统活动的关键核团，LHb内兴奋与抑制之间的平衡在抑郁发生中具有重要作用。帕金森病（PD）相关抑郁是PD常见的非运动系统表现，也是PD进展的危险因素，其发生机制不清。在前期研究的基础上，本项目以PD相关抑郁模型大鼠为对象，研究：（1）LHb内钙通透AMPA受体（CP-AMPAR）在调节大鼠抑郁样行为中的作用，及对LHb神经元电活动的影响；（2）光刺激投射到LHb的轴突，观察LHb内突触前末梢释放谷氨酸/GABA的比例，及CP-AMPAR对前额叶皮质单胺类递质释放的影响；（3）在mRNA和蛋白水平，LHb内CP-AMPAR亚单位GluR1,3,4和磷酸化亚单位在突触内外的表达，及CaMKII对亚单位的调节作用；（4）CP-AMPAR对抑郁相关脑区传出神经元活动的影响。上述研究将阐明LHb内CP-AMPAR介导的兴奋性传递在调节PD相关抑郁中的作用和机制。

外侧缰核（LHb）内钙通透（CP-AMPARs）和钙不通透AMPA受体（CI-AMPARs）介导的兴奋性传递在帕金森病（PD）相关抑郁中的作用尚不清楚。本研究结果显示：（1）黑质致密部（SNc）损毁诱发大鼠产生抑郁样行为。（2）在假手术组和损毁组大鼠，LHb内阻断CP-AMPARs产生抗抑郁样效应，这些效应与LHb神经元的抑制和内侧前额叶皮质（mPFC）内多巴胺（DA）和5-羟色胺（5-HT）释放增加有关。SNc损毁上调LHb内βCaMKII和p-GluR1-S831的表达。LHb内CP-AMPARs通过GABA能吻内侧被盖核（RMTg）影响腹侧背盖区后端（pVTA）DA神经元和中缝中核（MRN）5-HT神经元的活动。（3）在2组大鼠，LHb内激活AMPARs产生抗抑郁样效应，这些效应与VTA前端（aVTA）DA神经元和中缝背核（DRN）5-HT神经元的兴奋，以及mPFC内DA和5-HT释放增加有关；损毁RMTg不能改变这些神经元对AMPAR刺激引起的反应；LHb内阻断AMPARs则产生相反的效应。SNc损毁下调p-GluR2-S880在LHb的表达。（4）在2组大鼠，LHb内阻断GABA转运体1（GAT-1）产生抗抑郁样效应、降低LHb神经元的电活动和增加LHb细胞外液中GABA水平。在损毁组大鼠，LHb内阻断GAT-3也产生类似的效应，然而，它的阻断不影响假手术组大鼠。LHb内阻断星形胶质细胞谷氨酸转运体1（GLT-1）诱发抑郁样反应、增加LHb神经元的电活动和LHb细胞外液中谷氨酸水平。SNc损毁下调GAT-1、GAT-3和GLT-1在LHb的表达。上述结果提示：（1）SNc损毁导致LHb内βCaMKII，以及含有GluR1亚单位的CP-AMPARs和含有GluR2亚单位的CI-AMPARs表达上调；（2）LHb中CP-AMPARs和CI-AMPARs通过不同的神经通路调节抑郁样行为，即CP-AMPAR-RMTg-pVTA/MRN-mPFC通路和CI-AMPAR- aVTA/DRN-mPFC通路；（3）LHb中GAT-1、GAT-3和GLT-1涉及抑郁样行为的调节，并且SNc损毁导致LHb中GAT-1、GAT-3和GLT-1的表达下调。这些发现表明黒质-纹状体通路损毁增强了LHb中AMPAR介导的兴奋性传递过程，它在PD相关抑郁中具有重要作用。