Different neurotransmitter metabolite concentrations in CSF samples from inpatient and outpatient normal volunteers

Cerebrospinal fluid concentrations of the neurotransmitter metabolites 5-hydroxyindoleacetic acid (5HIAA), homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were compared in two groups of healthy volunteer subjects. One group (outpatient) was composed of 27 subjects who were transported to the outpatient clinic on the day of the lumbar puncture (LP). The other group (inpatient) was composed of 10 subjects who were admitted to the NIMH Research Ward on the evening prior to the LP. After statistical adjustment for age, height, sex and season in which LP was performed the inpatient group had significantly higher concentrations of both 5HIAA and HVA (P less than 0.005 and P less than 0.05, respectively) than the outpatient group. The difference in DOPAC concentration approached significance (P = 0.056), but there was no difference in MHPG concentration between the groups. This result indicates the need for strict control of environment in studies of CSF monoamines and their metabolites.