Objectives: To compare the effects of electroacupuncture (EA) with different time intervals on corticospinal excitability of the primary motor cortex (M1) and the upper limb motor function in healthy subjects and observe the after-effect rule of acupuncture.
Methods: Self-comparison before and after intervention design was adopted. Fifteen healthy subjects were included and all of them received three stages of trial observation, namely EA0 group (received one session of EA), EA6h group (received two sessions of EA within 1 day, with an interval of 6 h) and EA48h group (received two sessions of EA within 3 days, with an interval of 48 h). The washout period among stages was 1 week. In each group, the needles were inserted perpendicularly at Hegu (LI 4) on the left side, 23 mm in depth and at a non-acupoint, 0.5 cm nearby to the left side of Hegu (LI 4), separately. Han's acupoint nerve stimulator (HANS-200A) was attached to these two needles, with continuous wave and the frequency of 2 Hz. The stimulation intensity was exerted higher than the exercise threshold (local muscle twitching was visible, and pain was tolerable by healthy subjects, 1-2 mA ). The needles were retained for 30 min. Using the single pulse mode of transcranial magnetic stimulation (TMS) technique, before the first session of EA (T0) and at the moment (T1), in 2 h (T2) and 24 h (T3) after the end of the last session of EA, on the left first dorsal interosseous muscle, the amplitude, latency (LAT), resting motor threshold (rMT) of motor evoked potentials (MEPs) and the completion time of grooved pegboard test (GPT) were detected. Besides, in the EA6h group, TMS was adopted to detect the excitability of M1 (amplitude, LAT and rMT of MEPs) before the last session of EA (T0*).
Results: The amplitude of MEPs at T1 and T2 in the EA0 group, at T0* in the EA6h group and at T1, T2 and T3 in the EA48h group was higher when compared with the value at T0 in each group separately (P<0.001). At T1, the amplitude of MEPs in the EA0 group and the EA48h group was higher than that in the EA6h group (P<0.001, P<0.01); at T2, it was higher in the EA0 group when compared with that in the EA6h group (P<0.01); at T3, the amplitude in the EA0 group and the EA6h group was lower than that of the EA48h group (P<0.001). The LAT at T1 was shorter than that at T0 in the three groups (P<0.05), and the changes were not obvious at the rest time points compared with that at T0 (P > 0.05). The GPT completion time of healthy subjects in the EA0 group and the EA48h group at T1, T2 and T3 was reduced in comparison with that at T0 (P<0.001). The completion time at T3 was shorter than that at T0 in the EA6h group (P<0.05); at T2, it was reduced in the EA48h group when compared with that of the EA6h group (P<0.05). There were no significant differences in rMT among the three groups and within each group (P>0.05).
Conclusions: Under physiological conditions, EA has obvious after-effect on corticospinal excitability and upper limb motor function. The short-term interval protocol (6 h) blocks the after-effect of EA to a certain extent, while the long-term interval protocol (48 h) prolongs the after-effect of EA.
目的: 比较不同间隔时间电针对健康受试者初级运动皮层（M1）皮质脊髓兴奋性及上肢运动功能的影响，观察针刺后效应规律。方法: 采用同体自身前后对照设计，纳入15名健康受试者，所有健康受试者共接受3个阶段的试验观察，分别为EA0组（单独接受电针1次）、EA6h组（1 d内接受2次电针刺激，2次干预间隔6 h）和EA48h组（3 d内接受2次电针刺激，2次干预间隔48 h），各阶段之间洗脱期为1周。各组均直刺左侧合谷23 mm，并且在合谷穴向左旁开0.5 cm处再直刺1针，连接HANS-200A韩氏电针仪，予连续波，频率2 Hz，给予运动阈值以上的刺激强度（肉眼可见局部肌肉明显跳动，且健康受试者耐受为度，1~2 mA），留针30 min。运用经颅磁刺激（TMS）技术的单脉冲模式，检测首次电针前（T0）和末次电针结束后即刻（T1）、2 h（T2）、24 h（T3）健康受试者左侧第一背侧骨间肌的运动诱发电位（MEPs）波幅、潜伏期（LAT）、静息运动阈值（rMT）以及凹槽钉板试验（GPT）完成时间。EA6h组在末次电针前（T0*）运用TMS检测M1的兴奋性（MEPs波幅、LAT和rMT）。结果: EA0组T1、T2时点，EA6h组T0*时点以及EA48h组T1、T2、T3时点MEPs波幅均较T0时升高（P<0.001）。MEPs波幅在T1时点，EA0组、EA48h组较EA6h组升高（P<0.001，P<0.01）；在T2时点，EA0组较EA6h组升高（P<0.01）；在T3时点，EA0组、EA6h组较EA48h组降低（P<0.001）。3组T1时点LAT较T0时缩短（P<0.05），其余时点较T0时差异无统计学意义（P>0.05）。EA0组、EA48h组健康受试者T1、T2、T3时点GPT完成时间较T0时缩短（P<0.001），EA6h组T3时点较T0时缩短（P<0.05）；在T2时点，EA48h组较EA6h组缩短（P<0.05）。3组rMT组间、组内比较差异均无统计学意义（P>0.05）。结论: 生理状态下，电针对皮质脊髓兴奋性及上肢运动功能具有明显的后效应；短时间间隔（6 h）电针一定程度阻断了电针后效应，长时间间隔（48 h）电针可以延长电针后效应。.
Keywords: after-effect; corticospinal excitability; intervals of electroacupuncture; metaplasticity; transcranial magnetic stimulation.