Proteomic and transcriptional profiling of rat amygdala following social play

Social play is a frequently studied behavior and it is the most characteristic form of social interaction observed in adolescent rats. Social play is necessary for adolescents to develop proper cognitive, emotional, and social competency. Deficits in social play have been observed in several neurodegenerative disorders such as autism, schizophrenia, and attention deficit hyperactivity disorder. However, the information available on neural substrates and the mechanism involved in social play is still limited. This study characterized social play by proteomic and transcriptional profiling studies. Social play was performed on male Sprague Dawley rats on postnatal day 38 and protein and gene expression in the amygdala was determined following behavioral testing. The proteomic analysis led to the identification of 170 differentially expressed proteins (p≤0.05) with 67 upregulated and 103 downregulated proteins. The transcriptomic analysis led to the identification of 188 genes (adjusted p≤0.05) with 55 upregulated and 133 downregulated genes. Based on both protein and gene expression data, DAVID analysis revealed that social play altered neurotransmitter signaling including GABAergic and glutamatergic signaling and G-protein coupled receptor (GPCR) signaling. These data suggest that the synaptic levels of GABA and glutamate increased during play. Ingenuity Pathway Analysis (IPA) confirmed these alterations. IPA also revealed that differentially expressed genes/proteins in our data had significant over representation of additional neurotransmitter signaling systems, including the opioid, serotonin, and dopamine systems, suggesting that play alters the systems involved in the regulation of reward. In addition, corticotropin-releasing hormone signaling was altered indicating that an increased level of stress occurs during play. Our data suggest that increased inhibitory GPCR signaling in these neurotransmitter pathways occurs following social play as a physiological response to regulate the induced level of reward and stress and to maintain the excitatory-inhibitory balance in the neurotransmitter systems.社交玩耍行为是一项被广泛研究的行为模式，亦是青春期大鼠最具特征性的社交互动形式。青春期个体通过社交玩耍行为，得以发展出完备的认知、情感与社交能力。多项神经退行性疾病（neurodegenerative disorders）中均已观察到社交玩耍行为的缺损，具体包括孤独症（autism）、精神分裂症（schizophrenia）及注意缺陷多动障碍（attention deficit hyperactivity disorder）。然而，目前关于社交玩耍行为的神经底物（neural substrates）及潜在作用机制的相关研究信息仍较为有限。本研究通过蛋白质组学（proteomic）与转录组谱分析（transcriptional profiling）对社交玩耍行为进行了表征。实验选取出生后第38天的雄性斯普拉格-道利大鼠（Sprague Dawley rats）进行社交玩耍行为测试，于行为学检测完成后，对其杏仁核（amygdala）内的蛋白质与基因表达水平进行了测定。蛋白质组学分析共鉴定得到170种差异表达蛋白（differentially expressed proteins, p≤0.05），其中67种蛋白表达上调，103种蛋白表达下调。转录组学分析则鉴定得到188个差异表达基因（adjusted p≤0.05），其中55个基因表达上调，133个基因表达下调。结合蛋白质与基因表达数据，DAVID分析（DAVID analysis）显示，社交玩耍行为可改变多种神经递质信号通路，包括γ-氨基丁酸能（GABAergic）、谷氨酸能（glutamatergic）信号通路以及G蛋白偶联受体（G-protein coupled receptor, GPCR）信号通路。上述结果提示，社交玩耍过程中杏仁核内γ-氨基丁酸与谷氨酸的突触水平有所升高。Ingenuity通路分析（Ingenuity Pathway Analysis, IPA）验证了上述通路改变。此外，IPA分析还发现，本研究中差异表达的基因与蛋白显著富集于其他神经递质信号系统，包括阿片样物质（opioid）、5-羟色胺（serotonin）及多巴胺（dopamine）系统，提示社交玩耍行为可改变参与奖赏调控的相关系统。同时，促肾上腺皮质激素释放激素（corticotropin-releasing hormone）信号通路亦发生改变，表明社交玩耍过程中应激水平有所升高。本研究数据表明，社交玩耍行为后，上述神经递质通路中的抑制性GPCR信号通路会被激活，这一生理反应可对诱发的奖赏与应激水平进行调控，并维持神经递质系统内的兴奋-抑制平衡。