慢性复合应激对大鼠学习和记忆的影响

本文观察慢性复合应激对海马长时程增强(LTP)和一氧化氮合酶1(NOS1)表达变化的影响,并探讨了其在学习与记忆中的作用。将Wistar大鼠随机分为对照组和慢性复合应激组,每组各10只。应激组动物采用4种应激原无规律、交替性地进行长达6周的慢性复合应激试验。实验过程中测定动物血清皮质酮(CORT)水平,采用Morris水迷宫和Y迷宫测试大鼠学习和记忆成绩,记录海马齿状回LTP群体峰电位(PS)幅值的变化,同时观察海马CA1及齿状回区NOS1阳性神经元数目的变化。结果显示:(1)与对照组比较,慢性复合应激组动物在应激第4周和第6周时,血清皮质酮浓度的比值显著增高(P<0.05,P<0.01);(2)高频刺激(HFS)后各时间点的PS幅值增高更为明显(P<0.01);(3)Morris水迷宫和Y迷宫实验后慢性复合应激组动物的学习和记忆成绩优于对照组(P<0.05,P<0.01);(4)慢性复合应激组和对照组大鼠海马齿状回NOS1阳性神经元个数分别为8.80±3.91和5.44±1.14,两者间有统计学差异(P<0.05)。以上结果提示,慢性复合应激对大鼠的学习和记忆有一定的影响,可能与齿状回群体峰电位幅值增强和NOS1表达增强有关。

THE EFFECT OF CHRONIC MULTIPLE STRESS ON LEARNING AND MEMORY OF RATS

We investigated the effect of chronic multiple stress on learning, memory, long term potentiation (LTP) and the expression of NOS1 in the hippocampus of rats. The rats were randomly divided into the control group (n=10) and the chronic multiple-stressed group (n=10). The stressed group was subjected to four kinds of stressors irregularly and alternately for 6 weeks. Serum corticosterone (CORT) levels were examined during the process. The rats’performance of spatial learning and memory was tested using Morris Water Maze (MWM) and Y-maze. The change of the amplitude of LTP-population spike (PS) was recorded in hippocampal dentate gyrus (DG) of rats. Meanwhile, the NOS1-positive neurons in the hippocampal CA1 and DG were counted. The results showed that: (1) the concentration of the serum CORT was significantly higher on week 4 and 6 of the stressed period as compared with the control group (P<0.01); (2) after the delivery of high frequency stimulation (HFS), the amplitude of PS were increased significantly in the chronic multiple-stressed group (P<0.05, P<0.01); (3) the score of learning and memory in MWM and Y-maze test in the chronic multiple-stressed group was higher than that of the control group (P<0.05, P<0.01); (4) The numbers of NOS1-positive neurons were 8.80±3.91 and 5.44±1.14 in the hippocampal DG of the chronic multiple-stressed group and control group, respectively (P<0.05). These results collectively indicate that chronic multiple stress makes big effect on the process of learning and memory in rats, probably involving the increase of hippocampal LTP-PS and the expression of NOS1.