Age and Sex Differences in the Acquisition and Maintenance of Intravenous Amphetamine Self-Administration in Rats

Drug abuse peaks during adolescence, and exposure to drugs during adolescence predicts drug abuse in adulthood. Nevertheless, adolescence is not widely studied in animal models of drug intake. Moreover, few studies have investigated sex differences in drug-reinforced behavior during adolescence. We studied age-and sex-differences in acquisition and maintenance of amphetamine self-administration in Sprague-Dawley rats. Adolescent males took more amphetamine than adult males, supporting the hypothesis that adolescents are more sensitive to amphetamine. A high rate of " inappropriate " active lever presses among periadolescent males suggests impulsive behavior. In the maintenance phase of testing, young adult males failed to work as hard as adult males. In contrast, young adult females worked harder than adult females. Comparing sex groups, young adult females worked harder than age-matched males to obtain amphetamine. These results will ultimately help to form effective treatment and prevention programs for drug dependent individuals of all ages and both sexes.