The time course and magnitude of spontaneous recovery of parkinsonism produced by intracarotid administration of 1‐Methyl‐4‐Phenyl‐1,2,3,6‐tetrahydropyridine to monkeys

We studied rhesus monkeys with hemiparkinsonism or bilateral parkinsonism produced by unilateral or bilateral intracarotid administration of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine. Using a standardized clinical rating scale, 4 hemiparkinsonian monkeys showed a 13 to 56% (mean, 36%) spontaneous improvement during an obsevation period of up to 25 weeks. Generally, recovery leveled off after 14 weeks. Four bilaterally parkinsonian monkeys showed a 5 to 42%(mean, 22percnt;) improvement over a period of up to 30 weeks. Our findings emphasize that spontaneous recovery is a potentially confounding characteristic of this monkey model when used for assessing novel antiparkinsonian therapies.