钙蛋白酶活性对颅脑创伤大鼠海马神经细胞凋亡和学习记忆的影响

Effects of Calpain Activity on Cognitive Function and Neuronal Apoptosis in Hippocampus of Rats after Traumatic Brain Injury

目的:探讨钙蛋白酶活性对重型闭合性颅脑创伤大鼠海马神经细胞凋亡和学习记忆功能的影响。方法:采用重型闭合性颅脑创伤模型。将120只SD大鼠随机分为创伤组、治疗组、假手术组及对照组,前3组各36只分为伤后6、12、24、48、72h5个时相组,每亚组6只,进行钙蛋白酶活性测定及凋亡检测,余6只进行Morris水迷宫测试;对照组12只,其中6只进行钙蛋白酶活性测定及凋亡检测,另6只进行Morris水迷宫测试。治疗组各亚组在致伤前1d经侧脑室注射MDL28170(10μL),创伤组、假手术组及对照组给予生理盐水(10μL)。结果:创伤组大鼠海马在伤后6h钙蛋白酶活性升高,于24h达到高峰,治疗组各时相点海马区钙蛋白酶活性均较创伤组明显下调(P<0.01);创伤组大鼠伤后6h海马CA2区即出现少量凋亡阳性细胞,伤后24h明显增多,于伤后72h达高峰;治疗组凋亡细胞密度高峰较创伤组明显下调(P<0.01);定位航行能力测试结果表明治疗组搜索安全岛潜伏期较治疗组明显缩短(P<0.01);空间探索能力测试结果表明治疗组于第四象限的航行时间较创伤组明显延长(P<0.05)。结论:脑创伤后钙蛋白酶活性增加可能参与了神经细胞凋亡与学习记忆功能障碍的过程。

Objective：To approach the effects of calpain activity on hippocampal neuronal apoptosis and cognitive function in rats after traumatic brain injury （TBI）.Methods：The rat model of severe closed traumatic brain injury was used.One hundred and twenty SD rats were divided randomly into TBI group,treated group,sham operation group and control group.The first 3 groups of 36 rats were further divided into five-phase groups,such as 6,12,24,48,72 h after injury （each subgroup n= 6）.The calpain activity and neuronal apoptosis were observed in each subgroup.The cognitive function was tested in another 6 rats.There were 12 rats in control group.The calpain activity and neuronal apoptosis were observed in 6 rats of them and cognitive function was tested in another 6 rats.MDL28170 （10 μL） was injected into lateral ventricle of rats in treated group and isotonic Na chloride （10 μL） was injected in rats of TBI group,sham operation group and control group 1 d before TBI.Results：The calpain activity of the hippocampus was elevated in rats of TBI group at 6 h and peaked at 24 h.The calpain activity of the hippocampus was significantly lower at each time point in treated group than that of TBI group （P〈0.01）.A small amount of apoptosis-positive cells appeared in the CA2 area of hippocampus in TBI group at 6 h,significantly increased at 24 h and reached a peak at 72 h.The peak of apoptotic cell density was significantly reduced in treated group than that in TBI group （P〈0.01）.The results of place navigation proficiency test showed that the latency to search traffic island was significantly shorter in treated group than that of TBI group（P〈0.01）.The results of space exploration capability test results showed that the sailing time in the fourth quadrant was significantly longer in treated group than that in TBI group（P〈0.01）.Conclusion：The increased activity of calpain may result in neuronal apoptosis and cognitive dysfunction in rats after TBI.