Mu opiate receptor antagonist blocks electroacupuncture inhibition on noxious blood pressure response in rabbits

A pressor blood pressure response was elicited by strong electric shock stimulation of the front paw in rabbits anesthetized with chloralose and urethane, immobilized by gallamine triethiodide and maintained by artificial ventilation. The pressor response showed a gradual decline in 3-4 successive trials. Naloxone or TCTAP, a specific mu receptor antagonist, administered intraventricularly (icv) at that time could facilitate the pressor response (n = 8, P < 0.02; n = 7, P < 0.01), suggesting the involvement of mu receptors in the declination of the pressor response. Electroacupuncture could inhibit the pressor response (n = 7, P < 0.01), and the inhibition was readily blocked by TCTAP (n = 7, P < 0.01). No obvious changes were observed in the normal saline control group. The results suggest that acupuncture is able to inhibit the pressor response via the activation of the opioid peptidergic system, of which the mu receptor is an important component.