经颅磁刺激对脑梗死大鼠学习记忆与健侧海马锥体细胞树突和突触结构的影响

Effects of transcranial magnetic stimulation on learning and memory,morphology and ultrastructure of contralateral hippocampal CA3 pyramidal neurons in rats with cerebral infarction

目的研究经颅磁刺激(TMS)对脑梗死后大鼠学习记忆功能,以及海马锥体细胞树突和突触结构的影响。方法将48只雄性SD大鼠随机分为正常组、模型组和TMS组,每组16只。采用线栓法对模型组和TMS组大鼠制作一侧大脑中动脉闭塞的脑梗死模型,并在制模后第2天,对TMS组给予每天2次、每次30个脉冲的TMS治疗,疗程4周;观察各组大鼠治疗后在Y-迷宫中的学习记忆成绩和梗死对侧海马锥体细胞树突和突触结构变化。结果(1)TMS组大鼠学习尝试次数[(18.4±4.8)次]少于模型组[(26.4±5.4)次;P<0.01],记忆再现次数[(6.1±1.3)次]多于模型组[(3.7±1.2)次;P<0.01];(2)TMS组海马CA3区锥体细胞树突顶树突总长度[(196±35)μm]长于模型组(175±33)μm;P<0.01]。(3)TMS组的突触后致密物质厚度[(68±11)nm]宽于模型组[(62±10)nm],穿孔性突触百分比(27.5%)高于模型组(10.0%),突触间隙[(16.7±1.8)nm]窄于模型组[(21.3±2.3)nm],均P<0.01和P<0.05。结论TMS能促进脑梗死大鼠学习记忆功能的恢复,其机制可能与海马锥体细胞树突和突触结构的改变有关。

Objective To study the effects of transcranial magnetic stimulation （TMS） on learning and memory, and morphology and ultrastructure of contralateral hippocampal CA3 pyramidal neurons in rats with cerebral infarction. Methods Forty-eight male SD rats were randomly divided into normal group, model group and TMS group. The rat models of focal cerebral infarction were established with unilateral middle cerebral artery （MCA） suture occlusion method in model group and TMS group. The rats in TMS group were given 4 week TMS treatment from the next day after infarction （2 times per day, 30 pulses per time）. The ability of learning and memory was measured with Y-maze and the morphology and ultrastructure of contralateral hippocampal CA3 pyramidal neurons were detected after 4 weeks. Results In comparison with model group, the ability of learning （ 18. 4 ±4. 8 vs. 26.4 ±5.4） and memory （6. 1 ± 1.3 vs. 3, 7 ± 1.2） of rats in TMS group increased significantly （ P 〈 0. 01 ）. The total length of apical dendrite of contralateral hippocampal CA3 pyramidal neurons in TMS group was significantly longer than that in model group [ （ 196 ± 35） μmvs. （175 ±33） μm;P〈0.01]. The post-synaptic density[ （68 ±11） nmvs. （62±10） nm;P〈 0. 01 ] and the percentage of perforated synapses （ 27. 5% vs. 10. 0% ; P 〈 0. 05 ） were significantly increased, while the synapse cleft width [（16.7±1.8 ） nm vs. （21.3 ±2.3） nm; P〈0.01] was narrower in TMS group than that in model group. Conclusion It is postulated that the improved ability of the learning and memory in rats following TMS treatment are likely to be related to the morphological and ultrastructural changes in contralateral hippocampal CA3 pyramidal neurons and the increased synaptic plasticity.