Hemiparkinsonism in a monkey after unilateral internal carotid artery infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is associated with regional ipsilateral changes in striatal dopamine D-2 receptor density.

Infusion of 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into the right internal carotid artery of a cynomologus monkey (Macaca fascicularis) induced an almost complete loss of the dopaminergic innervation of the right caudate-putamen and hemiparkinsonism. Digital subtraction autoradiography revealed that at 8 weeks postinjection, a major increase in [3H]spiroperidol binding to D-2 sites in the lateral regions of the right caudate nucleus and putamen occurred, without a significant change in the medial caudate nucleus and putamen. The 92-96% decrease in specific [3H]mazindol binding observed in the right striatum extended into the medial caudate nucleus and putamen and confirmed the extensive loss of dopamine inputs to this structure. The region of the increase in D-2 receptor density is innervated by somatosensory, motor and parietal cortex. This indicates that the increase in D-2 receptor density in this region of the striatum may play a particularly important role in the L-dihydroxyphenylanine-induced motoric recovery observed in such animals.