INVOLVEMENT OF MU-OPIOID RECEPTORS OF PERIAQUEDUCTAL GRAY (PAG) IN ACUPUNCTURE INHIBITION OF NOXIOUS BLOOD-PRESSURE RESPONSE IN RABBITS

Strong electric shock stimulation of the rabbit front paw elicited a p ressor blood pressure response regarded as noxious response. Ligands o f mu opioid receptors were microinjected into the PAG to observe their effects on acupunture inhibition of the pressor response. (1) ohmefen tanyl (OMF), a mu agonist, significantly attenuated the pressor respon se. Mu antagonist TCTAP greatly enhanced the pressor response. (2) Ele ctroacupuncture (EA) significantly inhibited the pressor response, the inhibition being readily reversed by TCTAP. The response after TCTAP was significantly greater than that of the control before EA. The resu lts suggest that noxious stimulation is able to activate the mu opioid receptor of the PAG to modulate the noxious response and EA is able t o enhance the activation.