脑震荡大鼠认知行为障碍及多巴胺能神经元的变化

目的　探讨脑震荡大鼠认知障碍的特征及多巴胺能神经元的变化。方法　用金属单摆打击装置复制大鼠单纯性脑震荡模型。随机分为伤后1，2，4，8，16，24d六个损伤组和对照组（各12只）；应用Morris水迷宫评价大鼠的学习记忆功能；用免疫组织化学方法研究中脑黑质致密区（SNC）和腹侧被盖区（VTA）多巴胺能神经元的变化。结果　8d组脑震荡后1～3d大鼠隐匿平台逃避潜伏期显著延长（P〈0，05），16d组和24d组水迷宫实验与对照组比较，差异无统计学意义。SNC和VTA的神经元酪氨酸羟化酶在伤后各组均不同程度增强，4d组反应最强，24d组有所减弱；24d组的SNC与对照组比较差异无统计学意义，但VTA与对照组比较，差异仍有统计学意义（P〈0，05）。结论 （1）脑震荡后大鼠出现近期空间学习记忆功能障碍；（2）脑震荡后多巴胺能神经元酪氨酸羟化酶表达增高。

Cognitive behavioral deficits and changes of dopaminergic neuron after brain concussion in rats

Objective To study the features of cognitive behavioral deficits and the change of do- paminergic neuron after brain concussion in rats.Methods An animal model of concussive brain inju- ry in rats was duplicated with a metallic pendulum-striker concussive device.Rats subjected to brain con- cussion were divided into 6 groups(n=12 in each group:the 1,2,4,8,16,and 24 day groups post- concussive injury).There were 12 normal rats in the control group.Learning and memory ability were e- valuated by Morris water maze (MWM) method.The changes of dopaminergic neurons in substantia nigra pars compact (SNC) and ventral tegmental area (VTA) in midbrain were studied using immunohisto- chemistry method.Results The escape latencies were longer statistically in the treated groups than in the control group on days 1-3 post-concussion.Within the period of days 4-21,MWM test was not signifi- cantly different from the controls.Tyrosine hydroxylase (TH)-immunoreaction (TH-IR) increased signifi- cantly in the SNC and VTA on 1 day post-concussion.The most significant change occured in the 4-day group.The expression of TH-IR in SNC had a descending tendency in the 8-day and 16-day groups com- pared to the 4-day group,and recovered in the 24-day group,but TH-IR in VTA still increased signifi- cantly compared to the control group.Conclusions The spatial learning and memory deficits of the rats are found in early period of post-brain concussion.The expression of TH-IR of dopaminergic neurons in- creases following brain concussion.We speculate that the increase in TH in earlier period may be caused by neuronal transient overexcitation following post brain concussion,and the increase in TH remained a period of time,which may reflect a compensatory response of dopaminergic neurons to up-regulate their synthesizing capacity in order to increase the efficiency of dopamine