Baseline breakpoints for self-administered cocaine under the PR schedule in adult SHR receiving vehicle during adolescence and adulthood (VEH/VEH), methylphenidate during adolescence and vehicle during adulthood (MPH/VEH), methylphenidate during adolescence and adulthood, with adult treatment occurring 1-hr before self-administration sessions (MPH/MPH 1-hr Pre), or methylphenidate during adolescence and adulthood, with adult treatment occurring 1-hr after self-administration sessions (MPH/MPH 1-hr Post). Values are the mean ± S.E.M. last FR completed. * p ≤ 0.04 compared to the VEH/VEH control.