Effects of naloxone on ethanol dependence in rats.

Adult male Long-Evans rats were maintained on an ethanol-containing liquid diet. During development of ethanol dependence, the rats were given daily i.p. injections of either naloxone (2 mg/kg) or saline daily. At the beginning of ethanol withdrawal, the rats were injected with either naloxone (10 mg/kg) or saline i.p. Rats injected with naloxone during the development of ethanol dependence consumed significantly more of the ethanol diet and therefore more ethanol than rats injected with saline. Rats treated with naloxone throughout both the development of ethanol dependence and during ethanol-withdrawal showed delayed or reduced withdrawal symptomatology compared to rats injected with only saline, naloxone only during the development of dependence and naloxone only during ethanol withdrawal. These results indicate that naloxone can alter the effects of chronic ethanol exposure and further suggest that ethanol may exert some of its actions via the brain opioid system.