Ethanol exposure as inducer of stable voluntary ethanol drinking in the male rat.

The effects of restricted 'Saturday night drinking' on voluntary ethanol intake was tested in male rats. During a treatment period of 57 weeks the animals (group B) could choose between ethanol and water for 24 h each week. After this period of choice they received ethanol (2.0 g/kg) i.v. Total weekly exposure was around 6-7 g/kg. Of two control groups, one was given i.p. injections of saline once a week (group A) and the other, in addition to saline injections, a continuous choice between ethanol (10%) and water as drinking fluid (group C). Weekly ethanol exposure was approximately 14 g/kg in group C. During a testing period of 46 weeks group A and C had continuous access to a choice between ethanol and water. After week 5 of the testing period concentrations of ethanol varied in 3-week intervals. For each tested concentration (5, 15, 20 and 25%) intake was calculated as g/kg per day based on the total period. For the reference concentration (10%) corresponding intake was calculated on 2 weeks prior to and 2 weeks after the tested concentration. In group B there was always a very strong correlation (r = 0.86-0.99) between intake of the different tested concentration and the corresponding reference concentration. This indicates that a strong individual preference for a defined daily dose of ethanol had developed in these rats. The corresponding relation was less developed in group C especially when higher concentrations of ethanol were tested. At the end of the testing period voluntary ethanol intake was slightly higher in group B and C when compared to group A. Analyses of blood ethanol levels at defined times during the testing period indicated an interrupted ethanol intake with occasionally substantial blood levels. Thus intermittent ethanol exposure can induce a voluntary ethanol drinking pattern in male rats which might be used as an animal model of alcoholism.