Dopamine D1 and D2 receptor interactions in the MPTP-treated marmoset.

In a modified MPTP model of Parkinson's disease in the marmoset, both L-DOPA and the dopamine D2 agonist quinpirole were found to exhibit anti-bradykinetic activity. Both the dopamine D1 agonist SKF38393 and the D1 antagonist SCH23390 reduced the anti-bradykinetic action of L-DOPA and quinpirole. These results are discussed with respect to partial agonist activity of SKF38393 and the possibility that other dopamine receptors may be required for anti-Parkinsonian drug activity.