Microdialysis study of striatal dopamine in MPTP-hemilesioned rats challenged with apomorphine and amphetamine.

Motor impairments of Parkinson's disease (PD) appear only after the loss of more than 70% of the DAergic neurons of the substantia nigra pars compacta (SNc). An earlier phase of this disease can be modeled in rats that received a unilateral infusion of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP) into the SNc. Though these animals do not present gross motor impairments, they rotate towards the lesioned side when challenged with DAergic drugs, like amphetamine and apomorphine.

6-hydroxydopamine lesions in the rat neostriatum impair sequential learning in a serial reaction time task.

Sequential behavior has been intensively investigated in humans using so-called serial reaction time tasks(SRTT), in which visual stimuli are either presented in a random or sequential order. Typically, when the stimulus presentation follows a previously learned sequential order,reaction times are decreased compared to random stimulus presentation and become partly automated. A vast amount of SRTT findings indicates that sequential learning and performance seem to be mediated amongst others by the basal ganglia-especially the striatum-and the neurotransmitter dopamine therein.