热应激对小鼠海马神经元的保护作用

本文观察了热应激预处理对脑缺血/再灌注昆明小鼠海马神经元的保护作用。实验采用昆明小鼠以双侧颈总动脉夹闭7min后再通制作脑缺血/再灌注模型,在缺血/再灌注前予以热应激预处理。根据不同的处理方法将动物随机分为四组:(1)正常对照组,(2)热应激预处理后缺血再灌注组(HS/IR),(3)缺血再灌注组(IR),(4)单纯热应激组(HS),后3组又分别分为1d、4d和14d三个亚组。水迷宫检测小鼠学习记忆的行为改变,免疫组织化学染色结合图像分析技术检测缺血/再灌注对海马CA1区神经元微管相关蛋白-2(MAP-2)的影响,Nissl染色计数CA1区神经元的数目。结果表明:与正常组、HS和HS/IR组比较,IR组小鼠水迷宫检测逃避潜伏期增加(P<0.01),其搜索策略以边缘式和限制式为主,而其它三组搜索策略则以趋向式和直线式为主。Nissl染色显示IR组和HS/IR组海马锥体细胞减少,且IR组细胞丢失比HS/IR组更多(P<0.05);MAP-2免疫组化染色显示4d时海马CA1区辐射层的树突发生紊乱和断裂,MAP-2有明显减少(P<0.05),14d时IR组MAP-2阳性表达主要聚集于胞浆中。以上实验结果提示,热应激预处理可以通过对海马神经元的保护作用改善动物脑缺血/再灌注引起的学习记忆能力的下降。

PROTECTIVE ROLES OF HEAT STRESS ON THE NEURONS IN HIPPOCAMPAL CA1 REGION OF MICE

The present study was to explore the effects of heat stress on the neurons in hippocampal CA1 region of mice after ischemia/ reperfusion. The mice were pretreated with heat stress followed by ischemia/reperfusion by clipping bilateral cervical common arteries for 7 min. According to different treatments, animals were divided randomly into 4 groups: (1) normal control group, (2) heat stress pretreatment followed by ischemia/reperfusion group (HS/IR),(3) ischemia/reperfusion group (IR), (4) heat stress group (HS). Animals in later three groups were subdivided into 3 subgroups (1d, 4 d and 14 d), respectively. The Morris water maze was used to test the ability of learning and memory, and Nissl staining was used to count the average number of survived neurons in hippocampal CA1 region. Immunohistochemistry combined with image analysis system to detect the changes of microtubule associated protein 2 (MAP-2) expression. The results showed that mice in IR group exhibited increased escape latency when compared with that of normal, HS and HS/IR groups (P<0.01), and the mice in IR group adopted an inefficient search strategy, major in circling and restricted searching manners. Nissl staining results showed a significant reduction in the number of pyramidal neurons in hippocampal CA1 regions in HS/IR and IR groups, with much decrease in IR group (P<0.01). Compared to group normal, the expression of MAP-2 in hippocampal CA1 region obviously decreased in IR group (P<0.05). The present results indicate that heat stress pretreatment can improve the spatial learning and memory function through protection to hippocampal neurons.