Characterisation of dyskinesias induced by L-dopa in MPTP-treated squirrel monkeys.

Intermittent treatment with L-dopa over a 2-year period induced abnormal involuntary movements in MPTP-treated squirrel monkeys. Dyskinesias included a choreic and dystonic component. Dose-response curves for chorea and dystonia revealed that the same dose of L-dopa (30 mg/kg) induced the highest score for both dyskinesias: however, the severity was much greater for chorea. Choreic movements were always most prevalent at the time of peak effect, whereas dystonia was apparent at the time of peak effect and at "end-of-dose", and was occasionally observed spontaneously. Our findings indicate that squirrel monkeys treated with MPTP develop L-dopa-induced dyskinesias which closely resemble those observed in Parkinson's disease. This species provides a valuable animal model to develop improved therapeutic agents.