慢性复合应激性学习记忆增强大鼠海马神经细胞增殖和突触后酪氨酸激酶表达的变化

PROLIFERATION AND EXPRESSION OF HIPPOCAMPAL CELLS AND CHANGE OF POSTSYNAPTIC DENSITY Fyn IN THE HIPPOCAMPUS OF THE RAT WHOSE LEARNING AND MEMORY WAS ENHANCED BY CHRONIC MULTIPLE STRESS

目的探讨慢性复合应激性学习记忆增强大鼠海马结构各亚区神经细胞数量变化,以及突触后致密物酪氨酸激酶(Fyn)在海马内表达的变化及其意义。方法39只大鼠随机分为复合应激组、单一应激对照组和正常对照组。复合应激组动物进行6周的垂直旋转、睡眠剥夺、捆绑(6 h/d)和夜间光照等慢性复合性应激实验;单一应激对照组进行6周的单一捆绑对照,6 h/d。实验结束后,所有动物分别进行3 d的Morris水迷宫测试,记录其学习和记忆成绩:并运用尼氏染色方法观察海马各区神经细胞数量的变化;同时采用免疫组织化学、RT-PCR方法检测Fyn在海马CA3区的表达变化以及海马Fyn mRNA水平的变化。结果单一应激对照组动物学习记忆成绩受损(P<0.05);复合应激组的学习与记忆成绩优于对照组(P<0.05);与对照组相比,复合应激组和单一应激组动物海马各区神经细胞数量明显增多(P<0.05);Fyn在复合应激组海马CA3区辐射层阳性表达比对照组明显增强(P<0.05),但单一应激对照组的则减弱(P<0.05);同时复合应激组动物的Fyn mRNA水平明显上调(P<0.05),而单一应激对照组的则明显下调(P<0.05)。大鼠的学习记忆成绩与Fyn的表达呈正相关。结论6周慢性复合性应激使大鼠的学习与记忆能力加强;海马各区神经元数量增多;Fyn在海马中的表达和Fyn mRNA转录水平均增加。提示Fyn参与了慢性复合性应激增强大鼠学习记忆能力的过程。

Objective To investigate the changes and the significance of the number of nerve cells and the expression of the postsynaptic density tyrosine kinase （Fyn） in the hippocampus of the rat whose spatial learning and memory function was enhanced by chronic multiple stress. Methods Thirty-nine adult rats were randomly divided into three groups： multiple stressed, single stressed and control group. Rats in the multiple stressed group were irregularly and alternatively exposed to the situation of vertical revolve, sleep expropriate, restraint （6h/d）, and night illumination for 6 weeks, to preparate chronic multiple stressed model. Rats in the single stressed group were exposed to restraint only for 6 weeks, 6hid. After that, the performance of spatial learning and memory of all rats was measured using Morris water maze. Nerve cells in different subfields of the hippocampus were observed using Cresyl violet method and counted regardless of size or shape. The expression of Fyn protein and the level of Fyn mRNA in the hippocampus of rats were detected by immunohistochemical method and RT-PCR technique respectively. Results Compared with control group, the performance of spatial learning and memory of rats was increased in multiple stressed group and decreased in single stressed group （ P 〈 0.05）. The numbers of nerve cells in DG, CA1 and CA3 of the hippocampus in beth multiple stressed and single stressed group were more than that in control group （ P 〈 0.05）. The immunoreactivities of Fyn in the stratum radiatum of CA3 region were increased in rats of multiple stressed group and decreased in rats of single stressed group（ P 〈 0.05）. The level of Fyn mRNA was also up-regulated in the hippocampus of multiple stressed rats and down-regulated in the single stressed rats （ P 〈 0.05 ）. The performance of spatial learning and memory of rats was positively correlated with Fyn expression. Conclusion Chronic multiple stress can enhance spatial learning and memory function of rats, and increase the number of nerve cells in the hippocampus. The expression of Fyn protein and the level of Fyn mRNA are also increased in the rat hippocampus respectively. These results suggest that Fyn may participate in the process of the enhanced learning and memory by chronic multiple stress.