Effect of acupuncture at ST36 on motor cortical excitation and inhibition

Abstract

Background: Acupuncture at Zusanli (ST36) is often used to facilitate motor recovery after stroke. However, the effect of acupuncture at ST36 on motor cortical excitation and inhibition remains unclear. This study aimed to explore the effect of acupuncture at ST36 on motor cortical excitation and inhibition.

Methods: Twenty healthy volunteers were recruited to receive acupuncture treatment. We selected the acupoint ST36 and its respective sham point as the experimental acupoint. Transcranial magnetic stimulation (TMS) was used to measure motor-evoked potentials (MEP) at 7 time points-before acupuncture (Pre), acupuncture (T0), 4 and 8 min after acupuncture (T4; T8), needle removal (T12), 4 and 8 min after needle removal (T16; T20). Simultaneously, paired TMS (pTMS) was employed to measure short- and long-interval intracortical inhibition (SICI [short latency intracortical inhibition]; LICI [long latency intracortical inhibition]), respectively, at three time points-before acupuncture (Pre), acupuncture (T0), needle removal (T12). After removing the acupuncture needle, all subjects were asked to quantify their Deqi sensation using a Gas table.

Results: The average Deqi sensation score of all subjects during acupuncture at ST36 was higher than that observed at the sham point. With acupuncture at ST36, the MEP amplitude was higher at three time points (T0, T4, T8) than at Pre, although the MEP amplitude tended toward Pre after needle removal. The MEP amplitude was also higher at the same time points (T0, T4, T8) than at the sham point. Furthermore, the Deqi sensation score was correlated with MEP amplitude. With acupuncture at ST36, SICI and LICI at T0 were higher than those at Pre, and SICI and LICI at T0 were higher than those at the sham point.

Conclusion: Acupuncture at ST36 increased motor cortical excitation and had an effect on the remaining needle phase. Deqi sensation was correlated with MEP amplitude. Acupuncture at ST36 also decreased motor cortical inhibition.

Keywords: Deqi; ST36; long-interval intracortical inhibition; motor-evoked potential; short-interval intracortical inhibition; transcranial magnetic stimulation.

Figure 1

The location of Zusanli (ST36) and experimental procedure. The location of Zusanli (ST36) and experimental procedure. (a) Zusanli (ST36) located in the tibialis anterior muscle, four finger breadths of subject below the kneecap, and one finger breadth of subject lateral from the anterior crest of the tibia, and the sham point next to the ST36 about 3 cm as a control. (b) Experimental procedure, we evaluated MEP amplitudes at 7 time points, namely, before acupuncture (Pre), acupuncture (T0), 4 min after acupuncture (T4), 8 min after acupuncture (T8), needle removal (T12), 4 min after needle removal (T16), and 8 min after needle removal (T20). T0, T4, and T8 were the retaining needle phase, T12, T16, and T20 were the needle removal phase

Figure 2

MEP amplitude during acupuncture ST36 and sham point. MEP amplitude during acupuncture right ST36 and sham point in seven time points. (a) Acupuncture right ST36 and sham point. (b) Acupuncture left ST36 and sham point. Compared the rest MEP amplitude (Pre) with the other time points: *p < .05, **p < .01, there were significant differences in T0, T4, and T8. Compared the MEP amplitudes of ST36 with sham point at the same time point: #p < .05, ##p < .01, there were significant differences in T0, T4, and T8

Figure 3

Correlation between Deqi sensation and cortical excitation. The abscissa indicates the VAS index (Deqi sensation). VAS index and cortical excitation, the coordinate indicates the value of MEP amplitudes. Solid lines represent the significant correction between VAS index and MEP amplitudes when acupuncture at ST36 and sham point

Figure 4

Motor cortical inhibition when acupuncture left ST36 and sham point in three time points. Motor cortical inhibition during acupuncture left ST36 and sham point in three times (Pre, T0, T12). SICI and LICI were measured using conditioned stimulus MEP over test stimulus MEP. (a) SICI (%TS alone), the CS intensity is respectively 70% AMT. (b) SICI (%TS alone), the CS intensity is respectively 80% AMT. (c) LICI (%TS alone), the ISI is 50 ms. (d) LICI (%TS alone), the ISI is 100 ms. Compared the same position in different time point: *p < .05, there were significant (p < .05) differences in T0 compare with Pre. #p < .05, there were significant (p < .05) differences in acupuncture at ST36 compare with the sham point in T0