ASSESSMENT OF DIURNAL-VARIATION OF CEREBROSPINAL-FLUID TRYPTOPHAN AND5-HYDROXYINDOLEACETIC ACID IN HEALTHY-HUMAN FEMALES

The role of serotonin (5-HT) in the pathogenesis and treatment of majo r neuropsychiatric disorders, including mood and anxiety disorders, co ntinues to be the subject of extensive research. Previous studies exam ining central 5-HT functioning measured cerebrospinal fluid (CSF) leve ls of 5-hydroxyindoleacetic acid (5-HIAA) by using single or multiple lumbar punctures. A number of investigators have demonstrated the feas iblity of continuous CSF sampling via an indwelling lumbar catheter to study CSF neurochemistry in healthy subjects and patients with neurop sychiatric illness. Four healthy female volunteers, aged 21-34 years, underwent continuous CSF sampling. CSF was collected at a constant rat e of 1 mi every 10 minutes over a 30-hour period, with levels of trypt ophan (TRP) and 5-HIAA measured every hour. Plasma was also obtained h ourly for TRP determination. The results of this study indicate that C SF 5-HIAA, CSF TRP, and plasma TRP levels showed variation over time, but failed to show diurnal fluctuation. Intraindividual coefficients o f variation determined for CSF 5-HIAA, CSF TRP, and plasma TRP ranged from 9.2 to 14.9%, 8.8 to 14.6%, and 14.7 to 19.0%, respectively. Cont inuous CSF sampling is safe and feasible in humans, and may prove usef ul for studies of central 5-HT neurotransmission in neuropsychiatric i llness.