糖尿病小鼠认知功能障碍的NMDAR机制研究

Experimental study on the action mechanism of NMDAR in diabetic mice with cognitive dysfunction

目的观察2型糖尿病db/db小鼠海马N-甲基-D-天冬氨酸受体(NMDAR)的变化规律,探讨其在糖尿病认知功能障碍形成中的作用机制。方法选用雄性C57BL/Ks J-db/db小鼠8只为糖尿病组,另选取同窝同周龄C57BL/Ks J-db/m小鼠10只为正常对照组,喂养6周后检测小鼠的血糖、体重,并通过Morris水迷宫测试小鼠的学习记忆能力,神经电生理技术检测小鼠海马突触传递LTP的变化,实时荧光定量PCR检测其海马CA1区NMDAR2B mRNA的表达水平。结果糖尿病组小鼠血糖及体重较正常对照组明显增高(P<0.05);Morris水迷宫实验中,与正常对照组相比,糖尿病组小鼠的逃避潜伏期延长和穿越平台次数明显减少,差异有统计学意义(P<0.05);电生理学实验中,高频刺激后,2组小鼠均可观察到PS幅值增大,糖尿病组的平均PS增幅明显低于正常对照组,差异有统计学意义(P<0.05);实时荧光定量PCR实验中,正常对照组与糖尿病组的NMDAR2B mRNA的表达水平分别为(1.86±0.14)、(1.02±0.12),且糖尿病组NMDAR2B mRNA的表达水平明显低于正常对照组,差异有统计学意义(P<0.05)。结论 db/db糖尿病小鼠表现出明显的学习记忆障碍和LTP下降,NMDAR的低表达可能为糖尿病认知能力下降的机制之一。

Objective To observe the changes of the expression levels of N-methyl-D-aspartate receptor（ NMDAR）mRNA in hippocampus of db/db mice,and to explore its action mechanism in pathogenesis of cognitive dysfunction in diabetic mice. Methods Eight male C57 BL/Ks J-db/db mice were selected as diabetes group,and the other 10 C57 BL/Ks J-db/m mice were selected as control group. After 6-week feeding,the levels of blood glucose and body weight were measured,moreover,the learning and memory ability of mice in both groups were detected by Morris water maze test,and the changes of long-term potentiation（ LTP） in hippocampus were observed by using neuro-electrophysiological technique,meanwhile,the expression levels of NMDAR2 B mRNA in hippocampus CA1 area were detected by Real-Time PCR. Results The levels of blood glucose and body weight in diabetes group were significantly higher than those in control group（ P〈 0. 05）. The results by Morris water maze test showed that the escaping latent time（ s） was prolonged,and the average number of times of crossing platform exploration was obviously decreased in diabetes group,as compared with that in control group（ P 〈0. 05）. The electrophysiological experiment showed that the increased amplitude of PS was observed in both groups after high frequency stimulation,moreover,the average PS amplitude in diabetes group was significantly lower than that in control group（ 136. 17 ±12. 73 % vs 251. 67 ± 43. 78 % ,P〈 0. 05）. Real-Time PCR showed that the expression levels of NMDAR2 B mRNA were（ 1. 86 ± 0. 14） and（ 1. 02 ± 0. 12）,respectively in control group and in diabetes group,which in diabetes group were significantly lower than those in control group（ P〈 0. 05）. Conclusion The db/db mice may develop a significant decrease in learning and memory ability,and the low expression of NMDAR may be one of mechanisms of diabetic cognitive deficits.