Serotonin and dopamine disturbances in patients with unipolar depression and Parkinsonism.

Probenecid was administered to 7 unipolar depressed patients, 7 parkinsonians and 7 extrapyramidal patients with senile dementia matched for age and sex. Before and after the administration of probenecid, the levels of 5 hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) were determined in the cerebrospinal fluid (CSF) of all patients in order to study the central turnover rate of serotonin and dopamine. Unipolar depressed patients showed a significantly lower increase in CSF 5HIAA levels after probenecid than parkinsonians. Patients with Parkinsonism had a reduced increment of CSF HVA levels following probenecid administration when compared to unipolar depressed and extrapyramidal patients with senile dementia.