Long-term Effects of Neonatal Seizures and Exercise on Learning, Memory and CaMKⅡ Expression in Hippocampus

新生期惊厥活动可造成严重的神经后遗症,如成年期大脑对惊厥的易感和易损性提高,严重者产生认知功能损害.对发育期惊厥性脑损伤远期预后的研究,尤其是分子机制及其干预的研究具有重要的临床意义.探讨了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钙/钙调素依赖性蛋白激酶Ⅱ(CaMKⅡ)表达的远期影响及运动训练的干预作用.生后6天(P6)的SD大鼠随机分成单次长程惊厥组(SS)、反复惊厥组(RS)和对照组,每组12只.3组大鼠分别于P27～P31、P58～P61、P80～P82采用Morris水迷宫检测学习、记忆功能.P51～P56对SS组和RS组进行踏转轮训练.最后脑组织切片观察CaMKⅡmRNA在海马的表达.结果显示,第一次Morris水迷宫测试RS组第1天～第4天潜伏期明显高于对照组,具有显著性差异(P＜0.05),第二次水迷宫RS组第1天～第2天的逃避潜伏期较对照组仍显著延长,具有显著性差异(P＜0.05),第三次测试各组之间差异无统计学意义.搜寻策略显示,在第一次Morris测试时RS组第3天～第4天边缘式搜寻比例明显高于对照组,具有显著性差异(P＜0.01),同时RS组第3天～第4天趋向式搜寻比例明显低于对照组,具有显著性差异(P＜0.01),而第二次和第三次水迷宫测试3组间趋向式和直线式搜寻策略无明显差异.在记忆实验中,原平台象限游泳距离与总距离的比值,RS组第三次较对照组显著降低,有统计学意义(P＜0.05);另外RS组1～3天趋向式搜寻比例均明显低于对照组,有显著性差异(P＜0.05).CaMKⅡ原位杂交显示,各组CaMKⅡmRNA在海马均有明显表达,但是在齿状回和门区RS组表达明显低于对照组,具有统计学意义(P＜0.01).研究表明,新生期反复长程惊厥能够对学习和记忆功能产生远期的损害,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.早期运动训练能够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.Despite the clinical and experimental concerns about the deleterious effects of neonatal seizures on brain development, the underlying mechanism of seizure-induced brain damage is still not clear. Moreover, early therapeutic intervention studies are also less available. For this reason, the study was performed to explore the long-term effects of neonatal seizures and physical exercise on learning, memory and the expression of calcium/calmodulin- dependent protein kinase 11 (CaMK II). Twelve neonatal rats for each group were assigned: the single- seizure group (SS), the recurrent-seizure group (RS) and the control group. The volatile agent flurothyl was used to induce 30 min seizure attack. At postnatal day 6(P6), the single seizures induced only once and recurrent seizures induced once per day for consecutive 6 days. Control rats were placed into the container for an equal amount of time to their counterpart without exposure to flurothyl. Morris water-maze test were performed at P27 similar to P31, P58 similar to P61 and P80 similar to P82, meanwhile at P51 similar to P56, the RS and SS groups were submitted to forced running exercise. In situ hybridization method was used to detect the expression of CaMK 11 mRNA in hippocampus. The results are as follows: (1) Escape latency. In the first two Morris water-maze tests, there was a decreasing trend of escape latency in three groups, and the escape latency of RS group was much longer than that of control group. After physical exercise,in the last Morris water-maze tests, the diference of escape latency in three groups is not significant. (2) Searching strategy. In the first Morris water-maze test, there was a decreasing trend of marginal strategy and an increasing trend of taxis strategy in three groups, but the frequency of marginal strategy was higher and the frequency of taxis strategy was lower in RS group than that in SS and control group in the third and fourth day (P <0.01). However, there were no significant differences among three groups in the second and third Morris water-maze test. (3) Memory test. In the three memory tests, as for the distance ratioin between the origin platform quadrant to total distance, the RS group was the worst. The frequency 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). (4) In situ hybridization detection showed that the expression of CaMK 11 mRNA in dentate gyrus and hilus was much lower in RS group than that in SS and control groups (P < 0.01). It was concluded that recurrent but not single prolonged seizures could cause long-term effects on learning and memory, which may be associated with the down-regulated expression of CaMK II mRNA in hippocampus. Physical exercise improved the learning capacity of RS group but with no effect on memory capacity of RS group.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000254046500014&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)3197-1043