Serotonin receptor subtypes involved in modulation of electrical acupuncture

We examined the effects of intravenous injection of several serotonin (5-HT ) antagonists on the inhibitory action of electro-acupuncture (EAP) against the nociceptive responses in the trigeminal nucleus caudalis in rabbits. T he inhibitory effect of EAP was suppressed by pindolol, methysergide and IC S 205-930, whereas NAN-190 and ketanserin amplified the EAP effect. These r esults suggest that 5-HT1, except 5-HT1A; 5-HT2, except 5-HT2A; and 5-HT3 r eceptors are positively involved in EAP-induced analgesia, whereas the acti vation of 5-HT1A and 5-HT2A receptors suppressively act on EAP-induced anal gesia.