Brain region morphological and volumetric quantitative assessment using the 17.6T MRI in rats chronically exposed to methylphenidate

Methylphenidate (MPH) is presently the primary pharmacotherapy for the treatment of Attention Deficit Hyperactivity Disorder (ADHD). It has not been determined though what impact long-term treatment with this psychostimulant would have on behavior, neurochemistry or neuroanatomy. Previous studies have shown that the striatum is a major target of MPH treatment, consistent with human MRI studies. Also previous results have shown that long term-exposure to MP in adolescent rats has produced changes in dopamine D2 receptor levels and significantly enhanced cocaine self-administration in adulthood (Thanos et al. 2004). Different animal studies imply that the effects of MPH may depend on the neural responder system whereas structural and functional parameters are improved by MPH in animals with psychomotor impairments, they remain unaltered or get worse in healthy controls. Here we measured the effects of chronic treatment (8 months) with oral MP (1 or 2 mg/kg) or water, which was initiated in adolescent rats (4 weeks old). Following this treatment, rats in adulthood (9 month old) were perfused intracardially and their brains removed and imaged with a 17.6 T MRI for neuroanatomical volume assessment.