中文摘要：

目的观察不同强度高频重复经颅磁刺激（rTMS）对脑梗死大鼠缺血半暗带超微结构及脑源性神经营养因子（BDNF）表达的影响。方法将42只SD大鼠分为正常组、模型组、假刺激组及rTMS组，其中rTMS组按不同刺激强度又细分为80％运动阈值（MT）组、100％MT组及120％MT组。将模型组、假刺激组、rTMS组制成右侧大脑中动脉栓塞模型，rTMS组各亚组大鼠于制模24h后分别给予不同强度20HzrTMS刺激，假刺激组大鼠给予假性磁刺激，模型组于制模后未给予其他特殊处理。于实验进行14d后采用透射电镜、免疫组化及免疫印迹（WB）技术观察各组大鼠缺血半暗带超微结构及BDNF表达。结果通过电镜观察发现，rTMS组各亚组大鼠缺血半暗带区超微结构损伤明显轻于模型组及假刺激组；通过WB技术检测发现，100％MT组和正常组BDNF光密度值均较假刺激组明显增高（P〈0．05），正常组和rTMS组各亚组BDNF光密度值虽然也高于模型组，但组间差异无统计学意义（P〉0．05）；通过免疫组化技术检测发现，各组大鼠BDNF阳性光密度值组间差异均无统计学意义（P〉0．05）。结论20Hz、特定强度（尤其是100％MT）rTMS能促进脑梗死大鼠缺血半暗带超微结构修复及BDNF表达，这可能是磁刺激治疗缺血性脑卒中的重要机制之一。

英文摘要：

Objective To investigate the effects of high-frequency repetitive transcranial magnetic stimulation （rTMS） at different intensities on the ultrastructure of an ischemic brain penumbra and the expression of brainderived neurotrophic factor （BDNF） using rats with permanent middle cerebral artery occlusion （ MCAO）. Methods Forty-two rats were randomly divided into a blank control group, an MCAO model control group, a sham stimulation control group and an rTMS group. The rTMS group was divided further into 3 subgroups： an 80% of motor threshold （MT） subgroup, a 100% of MT subgroup and a 120% of MT subgroup. The cerebral infarction model was established by right MCAO. rTMS treatment was given 24 hours after the MCAO model was successfully established. The rTMS group and sham stimulation control group were given 20 Hz rTMS with the planned intensities. The MCAO model control group was not given any stimulation. After 14 days of treatment, transmission electron microscopy, immunohistoehemical and Western blotting （WB） methods were used to investigate the ultrastructure of the isehemic penumbra and the expression of BDNF. Results Damage reflected in the ultrastructure in the 3 rTMS subgroups was less than in the model control group and the sham stimulation control group. Expression of BDNF protein increased significantly in 100% of the MT group and blank control group rats as compared with that in the sham stimulation control group, while the blank control group and the 3 rTMS subgroups had no statistically significant difference in comparison with the MCAO model control group. The expression of BDNF protein had no statistically significant difference between any of the groups. Conclusion 20 Hz rTMS might, especially at 100% of the MT, promote the recovery of the uhrastructure of neural tissues in the ischemic penumbra after acute cerebral infarction and enhance the expression of BDNF in the ipsilesional hemisphere. This may be one of the important mechanisms of rTMS＇s effectiveness in the treatme