美金刚改善血管性痴呆大鼠认知功能及相关作用机制的研究

目的 研究美金刚对血管性痴呆(VD)大鼠认知功能及海马N-甲基D-天(门)冬氨酸-2B亚基受体(NMDAR-2B)水平、突触后致密物质95(PSD-95)表达和钙/钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)活性的影响.方法 采用结扎双侧颈总动脉方法制备VD大鼠模型,将144只Wistar大鼠随机分为假手术组、VD模型组(VD组)和美金刚治疗组(美金刚组).于术后4、8、12、16周用Morris水迷宫检测各组大鼠的学习记忆水平,用RT-PCR法检测大鼠海马NMDAR-2B水平,用免疫组织化学法检测PSD-95的表达,用32P掺入法检测大鼠海马CaMK Ⅱ的活性.结果 与假手术组比较,VD模型组大鼠术后各时间点的学习记忆能力均显著下降(均P<0.01);海马NMDAR-2B的水平和PSD-95的表达在术后4周时明显增高(P<0.05或0.01),术后8～16周显著降低(均P<0.01);海马总CaMKⅡ活性术后4周时明显增高(P<0.01),术后8周下降(P>0.05),术后12、16周明显降低(均P<0.01).美金刚组术后4周时上述各项检测结果与假手术组差异无统计学意义,术后8、12周时学习记忆水平、NMDAR-2B水平和PSD-95的表达明显高于VD模型组(P<0.01或0.05);而总CaMKⅡ活性与VD模型组差异无统计学意义.结论 VD发生发展过程中,NMDAR-2B水平、PSD-95的表达和总CaMK Ⅱ活性先过度激活后明显降低,美金刚能拮抗或上调海马NMDAR-2B表达并改善VD大鼠的认知功能,但对CaMKⅡ活性的影响有限.

Relationship between Hippocampal NMDA Receptor together with Associated Synaptic Proteins and Development of Vascular Dementia in Rats

Objective To investigate the influence of Memantine on changes of N-methyl-D-aspartic acid receptor 2B (NMDAR-2B) level, the expression of postsynaptic density 95 ( PSD-95) and calcium/calmodulin-dependent protein kinase Ⅱ (CaMK Ⅱ)activities in the hippocampus of vascular dementia(VD)rats and their recognition. Methods The VD rat model was established by permanent,bilateral occlusion of the common carotid arteries. One hundred and forty-four Wistar rats were randomly divided into sham-operated group, VD model group and Memantine-treated group. The water maze test was performed to detect the ability of learning and memory of the rats,the changes of NMDAR-2B level were measured by RT-PCR,the changes in the expression of PSD-95 were detected by immunohistochemical staining,and the changes in the CaMK Ⅱ activities were determined by incorporation of ~(32)P into histone. Results Compared with the sham-operated group, the ability of learning and memory of VD rats was decreased significantly(P<0. 01); the level of NMDAR-2B and the expression of PSD-95 increased significantly at the 4th week after operation(F<0. 05 or 0. 01)and decreased at the 8th to 16th week after operation (P<0. 01). Total CaMK Ⅱ activity was increased significantly at the 4th week after operation(P<0. 01) ,then dropped at the 8th week after operation(P>0. 05) ,and decreased significantly at the 12th,16th week after operation(P<0. 01). As for Memantine-treated group,at the 4th week after operation,there was no statistically significant difference in the parameters mentioned above in contrast with the sham-operated group. At the 8th,and 12th week after operation,the ability of learning and memory,the level of NMDAR-2B and the expression of PSD-95 were significantly increased as compared with VD rats(P<0. 01 or 0. 05) ,but total CaMK Ⅱ activity was similar to that of VD rats. Conclusion With the development of VD,NMDAR-2B level,the expression of PSD-95 and CaMK Ⅱ activities were firstly over-activated,and then decreased greatly. Memantine can improve VD rats' recognition by modulating the expression of NMDAR-2B,but its effect on CaMK Ⅱ activity was limited.