This study examined plasma melatonin levels and the suppressant effect of light on melatonin production in the squirrel monkey. Monkeys were maintained on a 12: 12 light‐dark cycle (LD 12: 12) with lights on from 07:00 to 19:00. Plasma levels of melatonin were determined by gas chromatography negative chemical ionization mass spectrometry. Melatonin levels at 00:00 (99.5 ± 18.9 pg/ml) were significantly higher than at 02:00 (57.21 ± 7.7 pg/ml; Student's t = 2.859; P≤ 0.021). Baseline values at 02:00 were compared with levels at the same time of day after exposure to 2 hours of 200 lux of light (30.6 ± 13.1 pg/ml), which caused an average suppression of 54.8% in melatonin levels. One animal did not show light suppression. Results indicated that the squirrel monkey suppressant response to light, as well as baseline values of melatonin, varied between animals.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of pineal research|
|State||Published - Aug 1990|
- circadian rhythms
ASJC Scopus subject areas