Exchange of 5‐hydroxyindoleacetic acid between the spinal cord and lumbar cerebrospinal fluid.

Abstract

After inhibition of 5-hydroxyindoleacetic acid (5-HIAA) transport by repeated administration of probenecid in cats, this acid accumulated linearly in the lumbosacral cord, lumbar (CSF) and cisternal fluid during 5 h of experiment. A simple mathematical analysis of these results showed that the rates of 5-HIAA accumulation in the lumbar CSF and cisternal CSF were faster than in the cord; about 22% of 5-HIAA formed in the cord diffused into lumbar CSF and by measuring 5-HIAA in the lumbar CSF the concentration and turnover of 5-HIAA and turnover of serotonin in the lumbosacral cord could be calculated and the changes of 5-HIAA in the cisternal CSF predicted. It may be possible to calculate the level and turnover of endogeneous substances in the CNS on the basis of their measurement in the CSF.