Serotonergic Mechanisms in Parkinson's Disease

Parachlorophenylalanine, a potent and specific depletor of brain serotonin, was administered to six patients with idiopathic parkinsonism. Although cerebrospinal fluid levels of 5-hydroxyindoleacetic acid, the principal metabolite of serotonin, were substantially reduced, no consistent change in cardinal parkinsonian signs was observed. These findings suggest that the alterations in central serotonin metabolism attending Parkinson's disease may reflect a secondary derangement which has no effect on the severity of the extrapyramidal signs characteristic of this disorder.