Age-dependent effects of isolation housing on the self-administration of ethanol in laboratory rats

Studies of the influence of housing conditions on ethanol self-administration have been inconsistent, with findings that isolation housing increases, decreases or produces no effects on ethanol intake. One possible explanation for these discrepant findings is that the effects of housing are dependent on the age at which the manipulation is performed. In the present experiment rats were housed from weaning or from age 65 days in either an isolated or grouped condition. After 12 weeks, they were tested for the voluntary oral self-administration of ethanol. Although all rats consumed comparable quantities of ethanol when lower concentrations were available, the rats isolated from weaning consumed significantly greater amounts of more concentrated ethanol than their group-housed counterparts. In contrast, there was no difference in ethanol consumption between isolated and grouped rats when they were differentially housed at maturity. These data suggest that an important determinant of ethanol intake in rats is related to environmental factors and that the influence of these factors is age-dependent.