[Effects of four adrenergic drugs on electroacupuncture analgesia]

The role of central nor-epinephrine (NE) in electroacupuncture (EA) analgesia is a controversial question., it is probably due to the complication of adrenergic receptors. The present results show: (1) Clonidine 30 micrograms/2ml/kg ip had no significant effect on the pain threshold, but decreased the analgesic effect of EA. Clonidine 1.5 and 3 micrograms were injected into the lateral cerebral ventricles. After 45 minutes, the analgesic effect of EA was lowered as compared with the saline controls respectively. (2) Yohimbine had no significant effect on the basal pain threshold, but (icv Yoh 50 micrograms) elevated the analgesic effect of EA. (3) 2-adrenoceptor agonist methoxamine decreased the analgesic effect of EA. (4) Another 2-adrenoceptor antagonist prazosin (icv 16 micrograms) enhanced the analgesic effect of EA. These results suggest that an activation of alpha 1- or alpha 2-adrenoceptors would decrease the analgesic effect of EA.