DIHYDREXIDINE, A FULL D-1 DOPAMINE-RECEPTOR AGONIST, INDUCES ROTATIONAL ASYMMETRY IN HEMIPARKINSONIAN MONKEYS

Dihydrexidine (trans-10,11-dihydroxy-5,6,6a,7,8,12b hexanhyydrobenso-[ a]phenanthridine) is a full dopamine D-1 agonist. In rhesus macaque mo nkeys rendered hemiparkinsonian by unilateral intracarotid infusions o f 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), dihydrexidine ( 0.15-0.9 mg/kg) elicited dose-dependent contralateral rotation. The ef fects of dihydrexidine were blocked by pretreatment with the D-1 antag onist SCH 23390 (0.03 mg/kg), but not by the D-2 antagonist raclopride (0.025 mg/kg). These results suggest a functional role for D-1 recept ors in stimulating motor behavior in a primate model of Parkinson's di sease.