Seasonal variation in CSF5-HIAA concentrations in male rhesus macaques

Seasonal changes in cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5 -HIAA) concentrations were assessed on multiple occasions in 103 free-rangi ng male rhesus macaques (macaca mulatta). At the time of sampling subjects ranged between the ages of 2 and 6 years. CSF samples were collected betwee n the hours of 0900 and 1600 through the Fall, Winter, and Spring from 1990 through 1994. Data were analyzed in a general linear mixed model with rand om intercepts. Results indicated that CSF 5-HIAA concentrations decreased w ith age. CSF 5-HIAA concentrations were significantly increased in the Fall (October and November), which is the height of the breeding season, with n o evidence of differences between Winter and Spring. There was also some ev idence that the seasonal variation in CSF 5-HIAA concentrations was blunted in younger, more immature subjects. [Neuropsychopharmacology 22:240-250, 2 000] Published by Elsevier Science Inc.