2012年发表的国际卒中试验3(The third international stroke trial,IST3)表明,脑卒中为全球范围内60岁以上人群的第二大死亡原因,其中以缺血性脑卒中最为常见,首次发病的脑卒中患者中近1/3会遗留下各种功能障碍,包括运动功能障碍、认知障碍、吞咽障碍等,严重影响患者的日常生活活动能力和生存质量,同时也给家庭和社会带来了沉重的精神负担和经济负担。缺血性脑卒中是指由于血氧供应不足而促发后续一系列级联反应,最终引起部分脑组织的坏死和凋亡,其病理生理过程十分复杂。
近年来，可直接调控大脑皮质兴奋性的无创性脑部刺激（non—invasive brain stimulation，NIBS）技术越来越多地应用于脑卒中后康复干预。NIBS主要包括重复性经颅磁刺激（repetitive transcranial magnetic stimulation，rTMS）、经颅直流电刺激（transcranial direct current stimulation，tDCS）及成对关联刺激（paired associative stimulation，PAS）等。
Paired associative stimulation (PAS),combining transcranial magnetic stimulation (TMS) with electrical peripheral nerve stimulation (PNS) in pairs with an optimal interstimulus interval (ISI)in between,has been shown to influence the excitability of the motor cortex (MC)in humans.However,the underlying mechanisms remain unclear.This study was designed to explore an optimal protocol of PAS,which can modulate the excitability of MC in rats,and to investigate the underlying mechanisms. The resting motor thresholds (RMTs) of TMS-elicited motor evoked potentials (MEPs) recorded from the gastrocnemius muscle and the latency of P1 component of somatosensory evoked potentials (SEPs) induced by electrical tibial nerve stimulation were determined in male Sprague-Dawley rats (n=10).Sixty rats were then randomly divided into 3 groups:a PAS group (further divided into 10 subgroups at various ISIs calculated by using the latency of P1,n=5,respectively),a TMS (only)group (n=5)and a PNS (only)group (n=5).Ninety repetitions of PAS,TMS and PNS were administered to the rats in the 3 groups,respectively,at the frequency of 0.05 Hz and the intensity of TMS at 120% RMT and that of PNS at 6 mA.RMTs and motor evoked potentials'amplitude (MEPamp)were recorded before and immediately after the interventions.It was found that the MEPamp significantly decreased after PAS at ISI of 5 ms (P<0.05),while the MEPamp significantly increased after PAS at ISI of 15ms,as compared with those before the intervention (P<0.05).However,the RMT did not change significantly after PAS at ISI of 5 ms or 15 ms (P>0.05).PAS at other ISis as well as the sole use of TMS and PNS induced no remarkable changes in MEPamp and RMT.In conclusion,PAS can influence motor cortex excitability in rats.Neither TMS alone nor PNS alone shows significant effect.
Xiang-yu ZHANGYan-fang SUITie-cheng GUOSai-hua WANGYan HUYin-shan LU
