代谢型谷氨酸受体介导产前应激易感性引起的子代大鼠抑郁样行为的机制研究

Exposure to prenatal stress could significantly increase the incidence of depression in the offspring, however, the underlying molecular mechanism is not well understood. The exploration of the biological mechanism why some individuals are more susceptible to the effects of stress than others is expected to further clarify the pathogenic mechanism of depression induced by prenatal stress. Our previous work showed that prenatal stress caused neuron injury and apoptosis, which were involved in the depressive-like behavior of offspring, through the alteration of glutamate receptors levels and the downstream ERK2/CREB/Bcl-2 signaling pathway. Based on these works, we aim to investigate the susceptibility effect of prenatal stress on mGluRs expression and function in the hippocampus and prefrontal cortex, analyze the interaction between mGluRs and NMDARs, explore moderating effect of GR on mGluRs. We also decrease mGluRs by RNA interference in primary cultured hippocampal neurons in vitro to observe their impact on NMDA current. The exploration underlying the mechanism of mGluRs in depressive-like behavior of susceptible rats to prenatal stress may have important implications for pathogenesis of depression in prenatally stressed offspring, but also provide the theoretical and experimental evidence in the discovery of antidepressant drug target for clinical stress susceptibility individuals.

产前应激可显著增加子代抑郁的发生，但其发病机制尚不清楚，个体对相同应激源可表现出敏感性或适应性反应，对其生物学机制的研究有望进一步阐明产前应激易感性引起抑郁的致病机制。前期研究发现大鼠暴露于产前应激后，其体内谷氨酸水平及其受体的改变影响其下游信号通路ERK2/CREB/Bcl-2，导致神经细胞的损伤、凋亡，最终导致大鼠抑郁样行为。本项目拟探讨产前应激易感性对子代海马和前额叶皮层中mGluRs表达及功能的影响，分析mGluRs与 NMDARs蛋白功能的相互作用，考察GR对mGluRs的调节作用，并且体外RNA干扰原代培养海马神经元中mGluRs，观察神经元NMDA电流的改变，从而阐明mGluRs在产前应激易感性致子代抑郁的分子机制。这些研究对探讨产前应激易感性引起子代抑郁的发病机制具有重要意义，也为临床针对应激易感性人群抗抑郁治疗的药物靶点提供理论及实验依据。

目的：抑郁症是由遗传和环境因素相互作用造成的，其中遗传因素约占30%-40%。基因-环境相互作用相关研究表明，基因可以控制个体对环境暴露的敏感性。临床研究表明，心理社会环境性应激，如：亲人突然离世、日常生活压力、地震等自然灾害均可诱发易感性人群表现出抑郁症状。本课题建立产前应激动物模型，模拟女性孕期日常生活不良生活应激事件所导致的子代抑郁症，探讨mGluR5在应激易感性引起大鼠抑郁样行为的中的作用机制。.方法：本实验采用SD大鼠，通过产前束缚应激刺激建立动物应激模型。利用糖水偏好实验筛选出应激易感性或顺应性大鼠。以应激易感性大鼠为研究重点，进一步通过行为学实验、分子生物学实验、病毒转染等实验方法探讨mGluR5介导不同应激易感性引起大鼠抑郁样行为的作用机制。利用药理学实验进一步探讨GR对mGluR5的调节作用以及mGluR5拮抗剂的抗抑郁作用。.结果：糖水偏好实验表明，37.56%的大鼠对产前应激表现出易感性，与对照组相比，产前应激易感性大鼠在开场实验、强迫游泳、悬尾实验抑郁样行为指标有显著的变化，显示显著的统计学差异。在分子水平上与对照组相比，产前应激可显著增加谷氨酸浓度，上调mGluR5mRNA和蛋白水平，显示显著的统计学差异。与生理盐水处理组相比，氯胺酮干预组大鼠抑郁样行为得到营救。氯胺酮干预相比生理盐水处理可使mGluR5mRNA、蛋白水平下调，显示显著的统计学差异。氯胺酮可恢复产前应激引起NR1和PSD-95蛋白的下调。GR可显著下调mGluR5的表达，上调NR1蛋白的表达。产前应激上调的mGluR5蛋白水平可被mGluR5拮抗剂MPEP或激动剂CHPG阻断。氯胺酮能促进MPEP和CHPG对mGluR5蛋白下调的作用。MPEP促进氯胺酮上调NR1水平，而CHPG可抑制此作用。mGluR5过表达大鼠表现出明显的抑郁样行为，且这种变化可被氯胺酮阻断，同时，NR1和PSD-95表达也显著增高了。此外，将产前应激易感组大鼠中mGluR5敲低后，结果显示，这些大鼠的抑郁样行为缓解，同时mGluR5、NR1和PSD-95蛋白的表达与对照组持平，无显著性的统计学差异。.结论：氯胺酮可能通过降低mGluR5的mRNA和蛋白水平，上调NR1蛋白水平，进而上调PSD-95的表达，发挥抗抑郁作用。