Ethanol pre-exposure during adolescence or adulthood increases ethanol intake but ethanol-induced conditioned place preference is enhanced only when pre-exposure occurs in adolescence.

Behavioral sensitization has been suggested to contribute to uncontrolled alcohol consumption. The aim of this study was to investigate the effects of repeated ethanol administration in adolescent and adult mice on subsequent ethanol consumption and conditioned place preference (CPP). Mice were administered ethanol for 15 consecutive days. This ethanol regimen induced behavioral sensitization to a lesser degree in adolescents than in adults. Following ethanol treatment, mice were subjected to CPP procedure, or given a free choice between water and ethanol solutions. While ethanol-pretreated adult mice did not display a robust ethanol-induced CPP, ethanol induced a significant CPP in mice pretreated with ethanol during adolescence. Ethanol pretreated mice, regardless of age, showed higher ethanol intake to saline-treated mice. The present findings suggest that ethanol-induced neuroadaptations underlying behavioral sensitization may activate mechanisms responsible for enhanced ethanol intake, and also reveals that ethanol pre-exposure during adolescence increases ethanol reward as measured by CPP.