Effects of Acute and Repeated Administration of Methamphetamine on Aggression-Related Behavior During Adolescence in Male and Female Rats, and Subsequent Outcomes in Early Adulthood

Background: Although methamphetamine (MA) use during adolescence has be- come associated with increased aggressive, violent, and criminal behavior in humans, there is a relative lack of empirical research substantiating any direct link between acute and re- peated exposure to the drug, and heightened aggression. There is also little known about ex- posure during adolescence and subsequent effects on aggression in adulthood. Objective: The study aimed to determine effects of a single dose and repeated administration of MA on aggression-related behavior in adolescent rats, and subsequent effects in early adulthood. Method: Male and female adolescent rats were administered saline (via intraperitoneal injection) or a single dose of MA (2mg/kg) on postnatal day (PND) 35 followed by the same dose twice a day from PND36 to PND45. By means of the resident/intruder test, aggression-related behavior was assessed in all rats following their single exposure, after completion of the final repeated exposure, and again in early adulthood (PND90) after 45 drug-free days. Results: Both a single and repeated exposures to MA generally decreased aggression-related behavior in the adolescent animals. However, when tested again in early adulthood, increased aggression followed their ado- lescent experiences. Conclusion: While the effects of MA during adolescence could have arisen from decreased aggression, in- creased anxiety or decreased play fighting, its subsequent effects during early adulthood suggested changes in the developing adolescent brain that resulted in higher aggression.