The acute effects of multiple doses of methamphetamine on locomotor activity and anxiety-like behavior in adolescent and adult mice.

Methamphetamine (MA) is a highly addictive psychomotor stimulant drug. Research has shown that the acute effects of MA can be modulated by age, although previous findings from our lab do not find age differences in the effects of MA. Relatively little research has examined the effects of adolescent MA exposure; thus, it is important to understand how MA affects adolescent behavior and brain function compared to adults. In order to better understand the age differences in the effects of acute MA exposure, this research examined the effects of MA exposure on locomotor and anxiety-like behavior and plasma corticosterone levels in adolescent and adult C57BL/6 J mice. Mice were exposed to saline, 2 mg/kg MA, or 4 mg/kg MA and behavior was measured in the open field test. Immediately following behavioral testing, serum was collected, and plasma corticosterone levels were measured. MA-exposed mice showed increased locomotor activity and anxiety-like behavior compared to saline controls, regardless of age and dose of MA. However, adolescent mice showed the greatest locomotor response to the high dose of MA (4 mg/kg), whereas the adult mice showed the greatest locomotor response to the low dose of MA (2 mg/kg). There were no differences in stereotyped behavior between the adolescent and adult mice exposed to the low dose of MA (2 mg/kg) and the high dose of MA (4 mg/kg). There was no effect of MA exposure on plasma corticosterone levels. These data suggest age modulates the locomotor response to MA and further research is warranted to determine the developmental neurobiological mechanism underlying the dose-response age differences in the response to acute MA exposure.