Drug-induced dyskinesia in primates rendered hemiparkinsonian by intracarotid administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

The right common carotid artery was surgically exposed under general anaesthesia in 6 cynomolgus monkeys and MPTP (0.5–2.2 mg/kg) directly infused. This produced a hemiparkinsonian syndrome in the contralateral limbs which responded to treatment with both levodopa and apomorphine. these drugs also precipitated dose-dependent contralateral rotation which reached a peak 2 weeks after MPTP infusion. A massive depletion of large, presumably dopaminergic cells was found from the ipsilateral substantia nigra pars compacta. Three animals receiving chronic therapy with apomorphine developed choreoathetoid movements of the limbs and the face contralateral to the infusion 2 weeks after the commencement of treatment. The severity of the dyskinesia gradually increased and after 4 weeks peak-dose hemiballistic movements were seen. Levodopa and the selective D-2 and D-1 dopamine agonists LY-171555 and SKF 38393 also reversed parkinsonian features and produced contralateral rotation and peak-dose dyskinesia. This unilateral model of parkinsonism in the primate will be of value in the elucidation of the mechanisms by which chronic levodopa or dopamine agonist therapy enhance involuntary movements in parkinsonism.