Cerebrospinal fluid 5-hydroxyindoleacetic acid as an index of central serotonergic processes.

Faulty transmission in the central serotonin and catecholamine systems may be involved in some psychiatric and neurological conditions. Central monoamine metabolism can be studied by measuring amine metabolites in the lumbar cerebrospinal fluid (CSF), but results to date have been inconsistent. Since most studies have analyzed lumbar CSF, one reason for the inconsistencies may be that lumbar fluid does not reflect brain amine metabolism. We measured 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) in serial CSF samples obtained in connection with pneumoencephalographic (PEG) examinations: through seven samples of equal volume, a gradual increase was found for both metabolites in 14 neurological patients, and the first and last fractions were statistically significantly correlated. In addition, a small series of cisternal CSF samples from psychiatric (depressed and alcoholic) and neurological patients were analyzed for 5HIAA. Frequency distribution in cisternal CSF was similar to that of lumbar values, although the levels were about twice as high, close to those found in the last PEG fractions. There were no significant differences between patient groups either in cisternal or lumbar CSF 5HIAA. These findings suggest that while there is an ascending gradient, lumbar CSF samples do reflect amine metabolite concentrations of the more central fluid. No disease-specific differences in cisternal CSF were found which were absent in the lumbar fluid.