Injection of a low dose of haloperidol, that has no obvious behavioral effects in normal mice, produces akinesia, catalepsy, and somatosensory neglect in MPTP-treated mice. These neuroleptic-induced sensorimotor impairments are exhibited soon after MPTP treatments and coincide with a decrease in both striatal DA and DOPAC levels. DA and DOPAC content gradually return to near-control levels over a 3-5 month period. Interestingly, while the haloperidol-induced somatosensory deficits declined in parallel with the rise in DA and DOPAC levels, the motor deficits persisted for up to 5 months after MPTP administration. These data suggest subtle differences in the neurochemical mediation of these behaviors and that the persistence of neuronal impairments may not necessarily be revealed by near-normal transmitter levels.