Neuronal recordings in Parkinson's disease Patients with dyskinesias induced by apomorphine

Dopaminergic agents reverse parkinsonism but commonly induce dyskinesia in patients with Parkinson's disease (PD) on long-term levodopa therapy. The aim of this study was to determine the neurophysiologic correlates of the amelioration of parkinsonism and the involuntary movements produced by the dopamine agonist apomorphine. Seventeen PD patients were given apomorphine (2-6 mg) before surgery. Neural activity was recorded for individual neurons and for populations of neurons before and after apomorphine. Both internal (GPI) and external (GPe) segments of the globus pallidus were sampled in patients undergoing pallidal surgery. The subthalamic nucleus (STN) was sampled in STN surgery patients. Results suggest that dopaminergic agents act by decreasing GPi and STN activity, and increasing GPe activity, and that drug-induced dyskinesias results from a large reduction in GPi firing.