CSF 5-HIAA and nighttime activity in free-ranging primates.
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.
Mehlman
P T
PT
Division of Research and Development, LABS of Virginia, Inc., Yemassee, SC 29945, USA.
Westergaard
G C
GC
Hoos
B J
BJ
Sallee
F R
FR
Marsh
S
S
Suomi
S J
SJ
Linnoila
M
M
Higley
J D
JD
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
D008734:Methoxyhydroxyphenylglycol; D006897:Hydroxyindoleacetic Acid; D006719:Homovanillic Acid