Concentrations of serotonin and its related substances in the cerebrospinal fluid of parkinsonian patients and their relations to the severity of symptoms.

We evaluated the concentrations of free and total serotonin (5-hydroxytryptamine, 5-HT) and its related substances in the cerebrospinal fluid from patients with Parkinson's disease (PD). The concentrations of total 5-HT, 5-hydroxytryptophan, kynurenine and 3-hydroxykynurenine decreased significantly in PD patients compared with controls. The concentration of total 5-HT had significant negative correlations with Hoehn and Yahr's stages, the severity of rigidity, akinesia and gait freezing; the correlation with gait freezing was most conspicuous.