Acupuncture Suppresses Morphine Craving in Progressive Ratio Through the GABA System

Abstract

Previous studies revealed that acupuncture suppressed both morphine self-administration and morphine-seeking behavior after abstinence. Based on these results, this study examined whether acupuncture attenuated morphine-craving under a progressive ratio (PR) schedule and investigated the possible neuronal mechanism. Male Sprague-Dawley rats were trained to self-administer morphine (0.5 mg/kg) at a fixed ratio for 9 days, and rats who achieved stable infusion were switched to a PR schedule. When animals had taken no more morphine for 1 hour, the number of infusions was defined as the break point (BP). After PR training, animals that had established a stable BP received acupuncture the next day. Acupuncture was applied for 1 minute immediately before the test session. Bicuculline (1.0 mg/kg) and SCH 50911 (2.0 mg/kg) were given 30 minutes prior to acupuncture. The c-Fos levels in the ventral tegmental area (VTA) and the nucleus accumbens (NAc) were examined. Acupuncture at SI5 reduced the BP significantly. Moreover, the effects of acupuncture were blocked by either bicuculline or SCH 50911. Immunofluorescence revealed that acupuncture at SI5 decreased c-Fos expressions in the VTA and the NAc. This study demonstrates that acupuncture at SI5 is effective for the treatment of morphine-craving and that this effect is mediated via the GABA pathway.

Keywords: GABA; SI5; acupuncture; morphine; progressive ratio; self-administration.