重复经颅磁刺激对截瘫后脊髓兴奋性作用的实验研究

Effect of Repetitive Transcranial Magnetic Stimulation on Spinal Segmental Excitability of Spinal Cord Injury Rats

目的观察重复经颅磁刺激对脊髓损伤大鼠脊髓兴奋性的影响并探讨其机制。方法利用重物撞击法制备成年SD大鼠T10脊髓损伤模型,造模8周后脊髓损伤磁刺激组给予0.5Hz阈上强度经颅定位磁刺激,每天500个脉冲,共4周。另设脊髓损伤组及正常对照组。各组大鼠不同时点行后肢F波检测,观察F与M波幅比值;免疫组化法观察5-羟色胺(5-HT)在脊髓损伤区头尾端的变化情况。结果脊髓损伤后8周F波幅增高,M波幅恒定,与正常对照组比较,F/M波幅比值明显升高(P<0.01);磁刺激后,F/M波幅比值降低,与脊髓损伤组比较有非常显著性差异(P<0.01);脊髓损伤8周时,损伤头、尾端5-HT密度明显降低(P<0.01);磁刺激后,损伤头、尾端表达均明显升高(P<0.01)。结论重复经颅磁刺激可以降低慢性下胸段脊髓不全损伤大鼠脊髓兴奋性,其机制可能与通过残存5-HT能下行传导束增加递质分泌,改善脊髓上位中枢对脊髓损伤尾端的控制有关。

Objective To investigate the effect of repetitive transcranial magnetic stimulation （rTMS） on the spinal segmental excitability after spinal cord injury in adult rats. Methods T10 spinal cord injury models were made with weight-drop method. 8 weeks later, rTMS were applied to the experimental group at 0.5 Hz suprathreshold stimulation, 500 pulses daily for 4 weeks. Spinal cord injury rats without stimulation and normal rats were used as controls. At different time points, electronic evoked F-wave were measured. The ratio of F-wave amplitude to M-wave amplitude （F/M） were compared among these groups. Immunohistochemistry was used to detect the expression of 5-hydroxytryptamine （5-HT） in the rostral and caudal lesion segments. Results The ratio of F/M increased significantly （P〈0.01） 8 weeks after spinal cord injury compared with baseline ratio and regressed significantly （P〈0.01） after 4 weeks of rTMS. Expression of 5-HT in grey matter around lesion was decreased after spinal cord injury and increased significantly （P〈0.01） both in the rostral and caudal lesion segments in rTMS treatment group. Conclusion The increased spinal segmental excitability after spinal cord injury can be regressed by rTMS, which may be resulted in increased expression of 5-HT.