The dopamine D2 agonist LY 141865, but not the D1 agonist SKF 38393, reverses parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the common marmoset.

Marmosets treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (1-4 mg/kg i.p. daily for up to 8 days) develop profound parkinsonian akinesia. Administration of the D1 agonist SKF 38393 (1-20 mg/kg i.p.) 4-6 weeks later had no effect on the motor activity of animals pretreated with MPTP. In contrast, the administration of the D2 agonist LY 141865 (0.1 or 0.5 mg/kg i.p.) caused a marked increase in motor activity lasting for up to 2 h. We conclude that stimulation of D2 dopamine receptors is essential for motor activation of parkinsonian marmosets and that D1 stimulation alone is not sufficient to overcome the akinesia induced by MPTP treatment.