Fig. 2.

Effects of age and environment on acute cocaine-induced locomotion. Mean ± SEM ambulatory counts on day 1 for naive or habituated adolescent (P32) and adult (P90) rats after i.v. cocaine (0, 0.4 or 1 mg/kg) injections. Since there was no effect of nicotine pretreatment, groups were collapsed across this variable. Cocaine induced a dose-dependent locomotor activation in adolescent and adult rats. Novel environment (filled symbols) enhanced the behavioral response to all doses of cocaine compared to those habituated (open symbols) and reveals an effect of age. Adolescent rats show an increased response to cocaine as compared to adults in the novel environment. +p < 0.05, ++p < 0.01, +++p < 0.001 vs. 0 dose; ^*** p < 0.0001 vs. age; n = 11–26/group