Differential behavioral and neurochemical effects of cocaine after early exposure to methylphenidate in an animal model of attention deficit hyperactivity disorder.

We used a putative animal model of attention deficit hyperactivity disorder (ADHD), the SHR rat, to examine the effects of repeated exposure to methylphenidate (MPH; Ritalin) during the pubertal period on cocaine-induced conditioned place preference and dopamine (DA) levels in the nucleus accumbens (NAc) in adulthood. Our results indicate that early exposure to methylphenidate diminishes sensitivity to the incentive properties of cocaine in adulthood, but it does so without altering the response of the mesolimbic dopamine system.