Serotonin and 5-hydroxyindoleacetic acid in CSF. Difference in Parkinson's disease and dementia of the Alzheimer's type.

Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels were measured in the sixth, 13th, and 20th milliliters of CSF in patients with dementia of the Alzheimer's type (DAT) and Parkinson's disease (PD), and in an aliquot of CSF in controls. In patients with PD there was a positive correlation between 5-HT and 5-HIAA levels in the 20th milliliter of CSF, while in patients with DAT there was a negative correlation of these levels in this CSF fraction. In patients with the senile form of DAT the 5-HIAA levels in the 20th milliliter of CSF were higher than in patients with PD. These results indicate differential involvement of the serotoninergic system in DAT and PD, and may lead to the development of a chemical marker for DAT.