Abstract
Effects of electroacupuncture on the EMG activity of the tail muscle (M. extensor caudae medialis, ECM) elicited by noxious heat stimulation of the tail were investigated in lightly anesthetized rats. When electroacupuncture stimulation (EAS) was applied to the Zusanli point, which is one of the meridian points, at 50 Hz for 30 min, the EMG activity rapidly decreased to about 45% of the control during the first 5 min of EAS; this value continued during EAS for 30 min. After cessation of EAS, the decreased EMG activities recovered to the control level after 40-50 min. The EMG activities were statistically significant as compared with the control during EAS for 30 min and until 30 min after its cessation (P<0.05, t-test two-tailed) . EAS at various frequencies resulted in the decrease of the EMG activity with the increase of the pulse frequency. However, the EMG activity was almost equal to the frequency over 25 Hz. These results suggest the following: (1) the EMG activity of ECM muscle is a quantitative and electrophysiological indicator in the estimation of electroacupuncture effect; (2) frequencies over 25 Hz are more effective on electroacupuncture effect.
