PERIODIC NALTREXONE AND PROPENSITY TO TAKE ALCOHOLIC BEVERAGE

For over 2 months, 45 rats were maintained on a daily regimen involvin g 2 hr a day of access to both water and a palatable alcoholic beverag e. At first, they took little ethanol. As days progressed, they eventu ally took over 2 g/kg of ethanol during the 2 hr. Previous research in dicates that, without intervention, they would maintain this level of intake indefinitely. All rats were taken off the daily regimen for 30 days and then returned to it, i.e., rats received 30 days of ''abstine nce.'' For 35 days following abstinence, one-third of the subjects rec eived placebos daily, one-third received naltrexone (NTX), 10 mg/kg, d aily, and the one-third received NTX on days 1-5, 11-15, 21-25, and 31 -35 and placebos on the other days. Abstinence reduced all rats' intak es of alcohol compared with pre-abstinence levels. Rats that received only placebos quickly returned to taking alcohol at pre-abstinence lev els. Rats that received NTX daily increased their intakes up to the le vel normally expected for receiving NTX and no abstinence. Because rat s receiving daily NTX always drank a fraction of the alcohol consumed by those receiving placebos, NTX's effects did not diminish. As rats s ampled alcoholic beverage, however, the effects of abstinence did dimi nish. The rats of periodic NTX drank as rats getting NTX when they wer e given NTX and as rats getting placebos when they were given placebos . Furthermore, the rats of periodic NTX showed no carry-over effects f rom periods of NTX to no NTX. Abstinence and NTX together, apparently, reduce propensity to take alcoholic beverage more than either alone.