Acupuncture suppresses morphine self-administration through the GABA receptors

The neurobiological substrate for morphine self-administration in animals is believed to involve the dopamine system of the nucleus accumbens. Our previous study has shown that acupuncture at the acupoint Shenmen (HT7) reduced dopamine release in the nucleus accumbens and behavioral hyperactivity induced by systemic administration of morphine. Here we investigated the effect of acupuncture on morphine self-administration and potential roles of GABA receptors in the mechanisms behind acupuncture. Male Sprague-Dawley rats were trained to self-administer morphine (0.1 mg/kg per infusion) during daily 1-h session under fixed-ratio 1 schedule. Following the stable responding on morphine self-administration, acupuncture was applied to HT7 points bilaterally (1 min) prior to the testing session. Another groups of rats were given the GABA(B) receptor antagonist SCH 50911 (3.0 mg/kg, i.p.), the GABA(A) receptor antagonist bicuculline (1.0 mg/kg, i.p.) or saline 30 min prior to the acupuncture treatment. We have found that acupuncture at the acupoint HT7, but not at the control point Yangxi (LI5), significantly decreased morphine self-administration. Moreover, either SCH 50911 or bicuculline blocked the inhibitory effects of acupuncture on morphine self-administration. Taken together, the current results suggest that acupuncture at specific HT7 points regulates the reinforcing effects of morphine via regulation of GABA receptors.