慢性应激抑郁大鼠学习记忆及海马非对称性超微结构的改变

目的：探讨慢性不可预见性应激抑郁模型大鼠大脑海马非对称性超微结构与学习记忆能力的改变。方法：SD雄性大鼠20只，随机分为正常对照组与抑郁模型组，每组10只。采用慢性轻度不可预见性应激21d及单笼饲养方法建立抑郁模型，应激前以及应激21d末对两组大鼠进行旷场实验、液体消耗实验及体重测量，对大鼠进行避暗穿梭实验，测试其学习记忆能力，之后活杀动物，取出大鼠左右海马，制作常规电镜标本，观察海马超微结构的改变。结果：在穿梭变实验中抑郁大鼠学习记忆潜伏期减少，进入暗箱错误积分增多。抑郁大鼠左右侧海马超微结构中左侧海马较正常对照组神经细胞及胶质细胞变化明显，表现为内质网扩张，溶酶体增多。而右侧海马远不及左侧损伤严重。结论：慢性不可预见性应激抑郁大鼠学习记忆能力显著下降，其可能与海马组织在应激过程受到的累积损伤有关，且抑郁大鼠海马损伤呈非对称表现。

Changes of Asymmetric Ultrastructure and Learning Memory of Chronic Mild Stress Depressed Rats

Objective:To investigate the changes of asymmetric ultrastructure and learning memory of chronic mild unpredictable stress depressed rats.Methods:25 Adult,male twenty-five Sprague-Dawley(SD)rats were assigned randomly to two groups including normal control group(n=10)and stressed group(n=10)matched for weight.The depression model was established by chronic unpredictable mild stress and single house for 21 days.The rat's body weight,open-field test,absolute and relative volume of sucrose intake,all were recorded before CMUS and 21d after CMUS.After the step-through test,the rats were sacrificed and hippocampus were taken out.Ultrastructural changes of the prepared samples were observed under a transmission electron microscope.Results:The chronic mild stress depressed rats has a significant decrease in memory retention and a significant increase in the errorless scores of the entries into the dark compartment.The evident changes of the ultrastructre have taken place in the nerve cell and perineuronal oligodendrocyte of the left side of hippocampus of the chronic mild stress depressed rats.Distinct dilatation of endoplasmic reticulum,occurrence of numerous secondary lysosomes were found there.However,the trauma of the hippocampus of the right side is less serious than the left side.Conclusions:The chronic mild stress depressed rats has a significant decrease in the ability of learning memory and it may be concerned with the trauma of the hippocampus.The traumas present the asymmetry of the hippocampus.