运动训练对大鼠新生期惊厥所致认知损害和海马CaMKⅡ表达的影响

Long-term effects of neonatal seizures and physical exercise on learning,memory and CaMKⅡexpression in hippocampus of rats

目的探讨新生期大鼠单次长程或反复惊厥对学习、记忆能力和海马突触后致密物质CaMKⅡ表达的影响及运动训练的干预作用。方法生后6d的SD大鼠36只随机分成单次长程惊厥组(SS组)、反复惊厥组(RS组)和对照组,每组12只。3组大鼠分别于生后27～31d、58～61d、80～82d进行3次Morris水迷宫实验。期间于生后51～56d对SS组和RS组进行踏转轮训练。最后制作脑组织切片观察CaMKⅡ在海马中的表达。结果①搜寻策略:第1次Morris水迷宫实验各组1～5d边缘式搜寻比例均呈逐渐减少趋势,但RS组第3天～第4天边缘式搜寻比例仍明显高于对照组,差异具有统计学意义(P<0.01),同时趋向式搜寻比例则均呈逐渐增加趋势,但RS组第3天～第4天趋向式搜寻比例仍明显低于对照组,差异具有统计学意义(P<0.01);而第2次和第3次水迷宫实验3组间趋向式和直线式搜寻策略差异无统计学意义。②记忆实验:RS组1～3d趋向式搜寻比例均明显低于对照组,差异具有统计学意义(P<0.05)。③CaMKⅡ原位杂交:各组CaMKⅡmRNA在海马均有明显表达,但是在齿状回RS组表达明显低于对照组,差异具有统计学意义(P<0.01)。结论新生期反复长程惊厥能对学习和记忆功能产生远期损害,可能与海马记忆分子CaMKⅡ表达下调有关;而单次长程惊厥对学习记忆无明显影响。早期运动训练能明显改善反复惊厥所致的学习能力损害,但对记忆能力效果仍较差。

Objective To observe the long-term effects of neonatal seizures and physical exercise on learning, memory and the expression of calcium/calmodulindependent protein kinase II （CaMKll）. Methods Thirtysix neonatal Sprague-Dawley rats aged 6 days were randomized into 3 groups ： the singleseizure group （SS） , the recurrent-seizutte group （RS） and the control group. The rats in the RS and SS groups were put under forced running exercise program daily for one week once they reached the age of 51 days. Morris water-maze test were performed with the rats when they reach the age of 27-31 , 58 to 61 days and 80 to 82 days. In situ hybridization method was used to detect the expression of CaMKII mRNA in hippocampus. Results .Searching strategy： In the first Morris watermaze test, there was a decreasing tendency of marginal strategy and an increasing trend of taxis strategy in three groups, but the frequency of use of marginal strategy was higher and t of taxis strategy was lower in RS group thau that in SS and control groups in the third and fourth day（ P 〈0.01 ）. However, there were no significant differences among the three groups in the second and third Morris water-maze test. The escape latency of RS group was much longer than that of SS and control groups. There was no significant difference between the SS group and control group. Memory test： the frequency of use of taxis strategy was much lower in RS group than that in SS and control groups in the first to third day（ P 〈0.01 ）. （3）In situ hybridization detection showed that the expression of CaMKI1 mRNA in dentate gyrus was much lower in RS group than that in SS and control groups（P 〈0.01 ）. Conclusion Recurrent but not single pl＇olonged seizures might cause long-term effects on learning and memory, which might be associated with the down-regulated expression of CaMKII mRNA in hippoeampus. Physical exercise may improve the learning ca- pacity but not the memory capacity of the rats with recurrent-seizure RS group.