Levodopa improves motor deficits but can further disrupt cognition in a macaque parkinson model

Background Levodopa effectively relieves motor symptoms in Parkinson's disease (PD), but has had inconsistent effects on cognition, even worsening some aspects of cognitive functioning. Therefore, remediation of PD cognitive deficits is a major unmet need. However, drug development efforts have been hampered by lack of an animal model in which motor and cognitive deficits can be examined simultaneously. Methods Cynomolgus monkeys were trained to perform cognitive tasks and then chronically exposed to MPTP to slowly produce cognitive and motor deficits of parkinsonism. Results Administration of L-dopa to these animals dose dependently improved motor functioning, but did not significantly improve cognitive performance. At doses that maximally improved motor function, additional cognitive deficits were observed. The present model of MPTP-induced parkinsonism recapitulates important motor and cognitive aspects of PD. Results with L-dopa mirror data derived from PD patients. Conclusion This model should allow more efficient testing of potential PD therapeutics to evaluate motor and cognitive functions simultaneously. (c) 2012 Movement Disorder Society