Oral levodopa dose‐response study in MPTP‐induced hemiparkinsonian monkeys: Assessment with a new rating scale for monkey parkinsonism

Quantitative measures for the severity of MPTP‐induced parkinsonism and response to antiparkinsonian interventions in monkeys have been lacking. We carried out an oral levodopa dose‐response study in two rhesus monkeys whose left hemiparkinsonism was induced by intracarotid administration of MPTP. A newly developed clinical rating scale of monkey parkinsonism showed a consistent dose‐response relationship for levodopa over the dosage range of 50–3, 500 mg/day. Antiparkinsonian effects appeared at 200 mg/day and were optimal at 1,000–2,000 mg/day. Levodopa also reversed rotational behavior, improved movement times for both the impaired and opposite upper limb, and produced dyskinesias at high dosages. Thus, MPTP‐induced hemiparkinsonism in monkeys closely resembles the human disease condition, is associated with sensitive response measures, and should prove valuable for assessing novel antiparkinsonian therapies.