The D-1 dopamine receptor partial agonist, CY 208-243, exhibits antiparkinsonian activity in the MPTP-treated marmoset.

Administration of L-DOPA plus carbidopa, or the D-2 agonist (+)-PHNO, to MPTP-treated common marmosets caused motor hyperactivity and a reversal of the parkinsonian syndrome. In contrast, administration of the putative D-1 agonist SKF 38393 was without effect on movement or motor disability. The subsequent administration of another putative selective D-1 partial agonist CY 208-243 produced a dose-related improvement in motor activity and reversal of parkinsonian motor deficits in MPTP-treated animals. The effect of CY 208-243 was inhibited by pretreatment with the D-1 antagonist SCH 23390 and, to a lesser extent, by the D-2 antagonist sulpiride. In another group of normal drug naive marmosets, the administration of CY 208-243 produced only a small increase in motor activity. Following treatment with MPTP and without other drug administration, administration of CY 208-243 produced a marked reversal of motor deficits and locomotor hyperactivity. Thus, CY 208-243, suggested to be a partial D-1 agonist exhibits antiparkinsonian activity in MPTP-treated marmosets which does not require prior or concurrent exposure to D-2 agonists.