Effects of terguride, a partial D2 agonist, on MPTP-lesioned parkinsonian cynomolgus monkeys.

Behavioral effects of terguride, a partial dopamine D2 agonist, on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned parkinsonian cynomolgus monkeys were compared with those of the dopamine agonist apomorphine and the dopamine antagonist haloperidol. Terguride alone ameliorated the parkinsonism without inducing any sign of excitability, irritability, or aggressiveness (hyperactivity). Apomorphine alone also ameliorated the parkinsonism but induced marked hyperactivity. Haloperidol alone caused worsening of the parkinsonism, inducing transient eyelid closure. In combination with apomorphine, terguride suppressed the hyperactivity induced by apomorphine without reducing its antiparkinsonian effects. Pretreatment with haloperidol suppressed both the antiparkinsonian effects and the hyperactivity induced by apomorphine. Terguride thus exhibits both antiparkinsonian and antihyperactivity effects in a monkey model of Parkinson's disease, suggesting that terguride might be beneficial for treating motor dysfunction and dopaminergic psychosis in advanced Parkinson's disease.