急性情绪应激对大鼠行为和脑神经颗粒素磷酸化水平的影响

The Effects of Acute Emotional Stressor on Behavior and Phosphorylation Levels of Neurogranin in Rats

为探讨急性情绪应激对大鼠旷场行为的影响,以及脑神经颗粒素(Neuroganin,NG)变化与应激性行为效应之间的相互关系。以急性不确定性空瓶刺激,建立情绪应激动物模型。将40只雄性SD大鼠随机分为情绪应激组1(ES1,接受情绪应激和旷场测试)、情绪应激组2(ES2,只接受情绪应激)、正常对照组1(C1,无情绪应激,但接受旷场测试)和正常对照组(C2,无情绪应激,也无旷场测试)(n=10)。以旷场行为和高架十字迷宫任务来评定大鼠应激后的行为变化,Western印迹杂交法(Westernblotting)测定海马和前脑皮层中的NG含量和磷酸化水平。结果表明:(1)应激后ES1组的水平活动增加,与C1组比较,差异有显著性,p<0.01;(2)ES1组海马和前脑皮层的NG磷酸化水平高于C1和C2组,差异有显著性,均为p<0.05;ES2组的前脑皮层NG的磷酸化水平高于C1组,差异有显著性,为p<0.05;(3)海马的NG磷酸化水平与水平活动之间的相关达显著水平。提示急性情绪应激能导致动物明显的行为改变如焦虑,这种行为改变可能与脑内NG磷酸化水平的变化有关。水平活动可能是反映急性情绪应激的较敏感行为指标,海马NG磷酸化水平可能是预测急性情绪应激所致焦虑或抑郁行为的较敏感生物学指标。

Neurogranin （NG） is a brain-specific, postsynaptically located protein kinase C （PKC） substrate found by Watson and his colleagues in 1990. It is mainly distributed in the frontal cortex, hippocampus and amygdala of rodents that are considered as essential components of neural circuitry mediating stress responses. Numerous animal studies have demon- strated that NG is involved in several pathways of protein signal transduction in brain, long-term potentiation and long-term depression. NG-knockout animals exhibited deficits in learning and memory. These results implied that NG may be a me- diator between stress and behavior. However, until recently, the cellular role of NG has not been clearly established. To understand more molecular events underlying central mechanisms of stress-induced behavioral changes, the purpose of the present study was to investigate the effects of acute emotional stress on behavior and protein levels of neurogranin in brain, and the correlation between protein levels of neurogranin and stress-induced behavioral changes. Forty rats were randomly divided into emotional stressed group 1 （ emotional stress followed by behavioral test, ES1 ）, emotional stressed group 2 （only emotional stress, ES2）, handled-control 1 （only behavioral test, C1 ） and handled-control 2 （home cage, C2）, with ten in each. Randomly giving empty water bottles at set times was used as an emotional stressor. Behavioral changes in rats after stress were observed by open-field test and elevated plus maze task, and protein levels and phosphorylation of neurogranin of hippocampus and forebrain were determined by Western blotting. The results showed that locomotor activity in open-field test in ES1 was increased more than that in CI group （p 〈0.05）. Protein levels and phosphorylation of Neurogranin of hippocampus and forebrain in ES1 were significantly higher than that in C1 （p 〈 0.05, p 〈 0.05 ） and C2 （p 〈 0.05, p 〈 0.05 ）. Phosphorylation of Neurogranin level of forebrain in ES2 was significantly higher than that in C1 （p 〈0.05 ）. The correlation was significant at 0.05 levels between locomotor activity and phosphorylation of neurogranin in the hippocampus. These results suggested that neurogranin is one of the stress-related substances in brain. Acute emotional stress can induce anxiety. Locomotor activity may be a sensitive behavioral index, and phosphorylation of neurogranin in the hippocampus may be an effective biological predictor for anxiety and/or depression induced by acute emotional stress. In summary, acute emotional stress induces behavioral changes and phosphorylation levels of neurogranin in frontal cortex of rats. Underlying mechanisms explaining the behavioral changes in stress effects are discussed, including the role of neurogranin in the hippocampus and frontal cortex.