运动训练对血管性认知障碍大鼠记忆能力及海马突触可塑性的影响

关键词：血管性认知障碍  运动训练  记忆能力  海马  突触可塑性

Keywords:vascular cognitive impairment  exercise  memory capacity  hippocampus  synaptic plasticity

摘要：

      摘要 目的：观察运动训练对血管性认知障碍（vascular cognitive impairment， VCI）大鼠记忆能力的影响，并探讨可能的作用机制。 方法：采用双侧颈总动脉永久性结扎法构建VCI大鼠模型，按照随机数字表法随机分为假手术组（Sham， n=8）、运动训练组（VCI+Ex， n=8）和对照组（VCI， n=8）。运动训练组于术后48h开始在小动物跑步机上进行中强度有氧运动训练，第1周运动强度逐日增加（5m/min—11m/min），第2—4周采用恒定速度11m/min进行，每天30min，每周5天。假手术组大鼠和对照组大鼠分别在相同的时间点置于小动物跑步机内，但不开机，每天30min，每周5天，共4周。其余时间各组大鼠放回饲养笼内，自由进食、饮水与活动。在完成上述实验后，分别应用新事物识别实验（novel object recognition， NOR）和Y迷宫实验评定各组大鼠的记忆能力；然后通过过量麻醉法处死大鼠，断头取脑，分离提取海马组织；分别采用免疫荧光染色法观察海马区N-甲基-d-天冬氨酸受体（N-methyl-D-aspartic acid receptor， NMDAR）、α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体（α-amino-3-hydroxy-5-methyl-4-isoxazole-propionate receptor， AMPAR）的分布情况，采用免疫印迹法及检测海马组织PlexinA4、neuropilin-2的表达水平。 结果：在Y迷宫实验中，VCI+Ex组大鼠探索新异臂的次数多于VCI组，以及探索新异臂的时间长于VCI组，结果有显著性差异（P<0.05， P<0.001）；在NOR实验中，VCI+Ex组大鼠的新事物认知指数显著高于VCI组大鼠，差异有显著性差异（P<0.001）。免疫荧光结果显示，相比VCI组，VCI+Ex组海马区NMDAR、PlexinA4和neuropilin-2表达水平显著升高（P<0.01， P<0.05， P<0.05），同时AMPAR表达及NMDAR/AMPAR比率有升高趋势。免疫印迹结果显示，VCI+Ex大鼠海马区PlexinA4表达量高于VCI组，结果有显著差异（P<0.05）。 结论：运动训练可以改善VCI大鼠的记忆能力，其可能的机制为促进海马区NMDAR、PlexinA4和neuropilin-2表达，进而增强海马突触可塑性。

Abstract:

      Abstract Objective: To observe the effects of exercise training on the memory ability of rats with vascular cognitive impairment (VCI) and to explore the possible mechanisms of action. Method: Rat models of VCI were constructed by permanently ligating bilateral common carotid arteries, and were randomly divided into sham-operated groups (Sham, n=8), exercise-training groups (VCI+Ex, n=8), and control groups (VCI, n=8) according to the randomized numerical table method. The exercise training group started moderate-intensity aerobic exercise training on a small animal treadmill at 48 hours postoperatively, and the intensity of the exercise was increased day by day (5m/min—11m/min) in the first week, and was performed at a constant speed of 11m/min for 30 min per day, 5 days per week in the second to fourth weeks. Rats in the sham-operated group and the control group were placed in the small animal treadmill at the same time points, but not turned on, for 30 min per day, 5 days per week for 4 weeks. For the rest of the time, rats in each group were put back into the rearing cages and were free to eat, drink and move around. After completing the above experiments, the memory ability of rats in each group was evaluated by Novel Object Recognition (NOR) and Y-maze experiments; then the rats were euthanized by overdose anesthesia, and the hippocampal tissues were isolated and extracted from the brain. The distribution of N-methyl-d-aspartate receptor (NMDAR) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in the hippocampal region was observed by immunofluorescence staining, and the expression levels of PlexinA4 and neuropilin-2 in the hippocampal region were detected by Western Blot. Result: In the Y-maze experiment, rats in the VCI+Ex group explored the novel arm more frequently than the VCI group, as well as explored for a longer period of time than the VCI group, with significant differences (P<0.05, P<0.001); in the NOR experiment, the cognitive index of novelty of rats in the VCI+Ex group was significantly higher than that of rats in the VCI group, and the difference was significant (P<0.001). Immunofluorescence results showed that compared with the VCI group, the expression levels of NMDAR, PlexinA4, and neuropilin-2 in the hippocampal region of the VCI+Ex group were significantly higher (P<0.01, P<0.05, P<0.05, respectively), while there was a tendency for the expression of AMPAR and the ratio of NMDAR/AMPAR to be elevated. Western Blot results showed that PlexinA4 expression in the hippocampus of VCI+Ex rats was higher than that of the VCI group, and the results were significantly different (P<0.05). Conclusion: Exercise training can improve the memory ability of VCI rats, and the possible mechanism is to promote the expression of NMDAR, PlexinA4 and neuropilin-2 in the hippocampus, which in turn enhances the synaptic plasticity in the hippocampus.