ELIMINATION OF CENTRALLY FORMED 5-HYDROXYINDOLEACETIC ACID BY CEREBROSPINAL-FLUID AND URINE

Abstract— In rats, the release of centrally formed 5‐hydroxyindoleacetic acid (5‐HIAA) into brain and spinal cord perfusates and urine was measured. Data from spinal cord perfusion of anaesthetized rats indicate that more than about 36% of the spinal production (122ng/h) of 5‐HIAA is eliminated via the cerebrospinal fluid (CSF). More than 30% of cerebrally formed 5‐HIAA (265.0 ng/h) was calculated to be released into ventricular‐cisternal perfusates. Of the total amount of 5‐HIAA found in the urine we estimated that about 8% originates in the central nervous system (CNS). In probenecid treated animals there was a substantial increase in the outflow of 5‐HIAA in both perfusion systems. In the combined perfusion experiments no proportional increase of the cerebral contribution to the cisternal outflow was found after probenecid. Our data indicate that a significant proportion of centrally formed 5‐HIAA is eliminated by the CSF. No evidence was found for an increased contribution of cerebral 5‐HIAA to lumbar CSF after application of the probenecid test. Urinary levels of 5‐HIAA do not reflect quantitatively central 5‐hydroxytryptamine metabolism. Copyright © 1979, Wiley Blackwell. All rights reserved