Aged monkeys as a partial model for Parkinson's disease

► We examine aged African Green monkeys for signs of Parkinson's disease. ► We utilize a sensitive behavioral measure for correlating dopamine function with signs of parkinsonism. ► Aged monkeys had signs similar to MPTP-exposed adult monkeys. ► Treatment with dopamine agonists does not restore normal function in aged monkeys as it often fails to do in older patients with Parkinson's disease. ► We show a greater loss of dopamine in putamen than in caudate, a pattern that is more similar to human Parkinson's disease than the pattern seen after MPTP exposure.