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Investigating levodopa-induced dyskinesias in the parkinsonian primate. Research into the cause of dyskinesias arising from levodopa treatment has been vexingly limited, partly due to the lack of an inexpensive and widely available animal model. Rodents do not develop levodopa-induced dyskinesias in a clinically recognizable form. However, nonhuman primates with 1-methyl -4-phenyl -1,2,3,6- tetrahydropyridine (MPTP)-induced parkinsonism readily develop levodopa-induced dyskinesias that are virtually indistinguishable from those seen in patients with Parkinson's disease. We have developed and validated a five-point Global Primate Dyskinesia Rating Scale to accurately measure these dyskinesias. Monkeys with MPTP-induced parkinsonism were then investigated to evaluate the relationship between dyskinesias, parkinsonism and severity of the nigrostriatal lesion. All parkinsonian animals were responsive to levodopa, and developed dyskinesias within 2-3 days of levodopa administration. Monkeys treated with only a single injection of MPTP also developed dyskinesias, even though they were not parkinsonian. It would appear that there is a different threshold of striatal dopamine depletion for parkinsonism and dyskinesias in the monkey. Finally, three hypotheses, put forward to explain the genesis of dyskinesias, are reviewed, and various experimental approaches suggested for each. Ann Neurol 2000 Apr;47(4 Suppl 1):S79-89 Langston JW, Quik M, Petzinger G, Jakowec M, Di Monte DA The Parkinson's Institute, Sunnyvale, CA 94089-1605, USA. PMID: 10762135 janet paterson 53 now / 44 dx cd / 43 onset cd / 41 dx pd / 37 onset pd tel: 613 256 8340 url: "http://www.geocities.com/janet313/" email: [log in to unmask] smail: POBox 171 Almonte Ontario K0A 1A0 Canada