title: CSF 5-HIAA and nighttime activity in free-ranging primates.
abstract: Men with low CNS serotonin turnover, as measured by cerebrospinal fluid 5-hydroxyindoleacetic acid (CSF 5-HIAA) concentrations, exhibit aberrant circadian activity patterns characterized by disrupted sleep rhythms and daytime hyperactivity. To assess whether similar patterns are found in nonhuman primates we examined the relationships between CSF 5-HIAA and nighttime activity in free-ranging monkeys. CSF samples were obtained from 16 adult male rhesus macaques living on a 475 acre, heavily forested sea island. Each subject was captured, fitted with a radio-telemetry motion-detector collar, and then released back into its group. A receiver placed near the sleeping trees of the study subjects recorded activity between 2100 hrs and 0600 hrs. Trained observers recorded behavioral data during the day. The animals followed a typical diurnal activity pattern, as they were active 74% of the sampled time during the day and 37% of the sampled time during the night. CSF 5-HIAA concentrations were inversely correlated with total duration of nighttime activity as well as mean duration of all active events. Nighttime activity was inversely correlated with daytime activity. CSF 3-methoxy-hydroxyphenylglycol (MHPG) concentrations were positively correlated with total nighttime activity, and inversely correlated with daytime sleep frequency. We conclude that male rhesus with low CSF 5-HIAA concentrations have higher total nighttime activity, longer mean periods of nighttime activity, and sleep more during the day than do males with high CSF 5-HIAA concentrations. This suggests that low serotonergic neurotransmission is associated with aberrant diurnal activity, as evidenced by a disruption of nighttime sleep patterns and a compensatory higher rate of inactivity during the day.
authors.affiliation: Division of Research and Development, LABS of Virginia, Inc., Yemassee, SC 29945, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Mehlman
authors.forename: G C
authors.initials: GC
authors.lastname: Westergaard
authors.forename: B J
authors.initials: BJ
authors.lastname: Hoos
authors.forename: F R
authors.initials: FR
authors.lastname: Sallee
authors.forename: S
authors.initials: S
authors.lastname: Marsh
authors.forename: S J
authors.initials: SJ
authors.lastname: Suomi
authors.forename: M
authors.initials: M
authors.lastname: Linnoila
authors.forename: J D
authors.initials: JD
authors.lastname: Higley
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D006719:Homovanillic Acid / Q000134:cerebrospinal fluid; D006897:Hydroxyindoleacetic Acid / Q000134:cerebrospinal fluid*; D008027:Light; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000134:cerebrospinal fluid; D009043:Motor Activity; D012890:Sleep
chemical_list: D008734:Methoxyhydroxyphenylglycol; D006897:Hydroxyindoleacetic Acid; D006719:Homovanillic Acid