Methylphenidate and brain dopamine neurotoxicity

To further evaluate the dopamine (DA) neurotoxic potential of the widely prescribed psychostimulant, methylphenidate, mice were treated with various doses (range: 10-120 mg/kg) and treatment schedules of methylphenidate (every 2 h x 4 or twice daily x 4). Higher doses of methylphenidate produced intense stereotypy, as well as short- (5-day), but not long- (2-week), term depletions of striatal DA axonal markers. By contrast, amphetamine caused not only intense stereotypy, but also profound, long-lasting, dose-related DA deficits. These findings indicate that results of studies of amphetamine neurotoxicity using short (5-day) post-drug survival periods are potentially misleading. Further, the present findings confirm and extend previous results indicating that methylphenidate, unlike amphetamine, lacks DA neurotoxic potential, and strongly suggest that DA efflux, although perhaps necessary, is not sufficient for the expression of amphetamine-induced DA neurotoxicity.