The analgesic effects of automatically controlled rotating acupuncture in rats: mediation by endogenous opioid system

The technique of rotating acupuncture needles has long been used to enhance the effects of acupuncture in Oriental medicine. However, it is difficult to standardize and quantify this stimulation condition. Thus we developed an automatically controlled rotating acupuncture (ACRA) system. The present study was conducted to evaluate the analgesic effects of ACRA using 4 different stimulation conditions (i.e., angle and frequency of rotation: 90 degrees + 1 Hz, 90 degrees + 1/4 Hz, 360 degrees + 1 Hz, and 360 degrees + 1/4 Hz) in Sprague-Dawley rats. Tail-flick latency to a noxious radiant heat stimulus in lightly anesthetized rats was measured before and after 15 min of ACRA stimulation at the Zusanli (ST36) acupoint. ACRA stimulations under all of the conditions above produced more potent analgesic effects than plain acupuncture (PA, acupuncture needle insertion only), but only the 90 degrees + 1/4 Hz ACRA condition showed a statistically significant effect versus PA (P < 0.01). Further, the analgesic effect of 90 degrees + 1/4 Hz ACRA was reversed by pretreatment with naloxone (2 mg/kg, i.p.). These results indicate that the 90 degrees + 1/4 Hz ACRA stimulation has the most potent analgesic effect in rats and that this is mediated by the endogenous opioid system.