Factors influencing elevated ethanol consumption in adolescent relative to adult rats

Background: Many teenagers report frequent alcohol use during the adolescent period. Animal models may be an important tool for exploring factors that contribute to alcohol consumption during this critical period. Methods: Using a 24-hour, free-access, two-bottle-choice procedure between water and a sweetened solution with or without ethanol in nondeprived rats, the present series of experiments examined the contribution of a variety of contextual and experimental variables (i.e., isolate-housing versus pair-housing, type of sipper tube, caloric value of solution, prior experimental perturbations) on alcohol consumption in both adolescent and adult Sprague-Dawley rats. Results: Ethanol consumption was particularly magnified among adolescent rats using ball bearing-containing ball-point (BP) sipper tubes, with this exacerbated intake not due to caloric content of the ethanol solution. Isolation housing for 12 days did not alter ethanol consumption of adolescents relative to their socially housed counterparts while suppressing consumption of isolated adults. An examination of differences in the relative magnitude of adolescent ethanol consumption across experiments in this series revealed that ethanol intake among adolescents was elevated not only by the inclusion of BP sipper tubes but also by staggering the timing of isolate housing relative to the presentation of the novel ethanol solution. Conclusions: The results of this experimental series demonstrate that adolescent animals consume significantly more ethanol than adult animals under a variety of home cage, continuous-access circumstances, with the relatively greater intake of adolescents further magnified by a number of test conditions. Subtle experimental details often thought to be innocuous can have a substantial impact on overall amount of voluntary ethanol consumption observed in both adolescent and adult animals.