Diminished food-related motivation in adult rats treated with methamphetamine during adolescence

Drug use among adolescents continues to be an area of concern because of the possibility of long-lasting physical and mental changes. The aim of this study was to determine whether methamphetamine exposure during adolescence results in long-lasting neurobehavioral alterations in adulthood. Sprague-Dawley rats were injected with methamphetamine (4 mg/kg/day) during postnatal days 28-37. Once rats reached postnatal days 150, they were placed in standard operant chambers, where they were trained to respond to a lever for sucrose pellets, the experimental reinforcement. Methamphetamine exposure during adolescence did not result in a noteworthy impairment in the development of the correct lever touch response in the autoshaped learning test with 4 seconds delayed reinforcement. These rats were also tested for the motivation to obtain sucrose pellets under a progressive ratio schedule of the reinforcement on postnatal days 170. Decreased lever-pressing response was noted in male rats exposed to methamphetamine during adolescence, but not in female rats. These results indicate that methamphetamine exposure during adolescence results in a decrease in the motivation for a natural reinforcer later in adulthood, particularly in male rats. From our data, we suggest that male brains are less capable of facilitating recovery than female brains after methamphetamine-induced perturbation of brain function during the adolescent period.