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Phase‐shifting effects of light on the circadian rhythms of 5‐methoxytryptophol and melatonin in the chick pineal gland
Author(s) -
Zawilska Jolanta B.,
VivienRoels Berthe,
Skene Debra J.,
Pévet Paul,
Nowak Jerzy Z.
Publication year - 2000
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1034/j.1600-079x.2000.290101.x
Subject(s) - melatonin , circadian rhythm , endocrinology , medicine , pineal gland , rhythm , darkness , biology , botany
In the chick pineal gland, 5‐methoxytryptophol and melatonin concentrations fluctuate in a rhythmic manner. These rhythms are circadian in nature persisting in constant darkness and have opposite phases. Acute exposure of chicks to white light (30 lux for 5, 10, 20, and 30 min) at night increased the amount of pineal 5‐methoxytryptophol and decreased pineal melatonin content. A 6 hr pulse of light (100 lux) applied early in the subjective night (CT12–CT18) caused a delay in the phase of the circadian rhythms of 5‐methoxytryptophol and melatonin by 3.7 and 4.5 h, respectively, compared to untreated controls. When the 6 hr light pulse was given during the late subjective night (C18–CT24) it advanced the phase of the 5‐methoxytryptophol and melatonin rhythms by 8.1 and 11.9 h, respectively. In the chick pineal the phase‐advancing effects of light on the circadian rhythms of 5‐methoxytryptophol and melatonin were more pronounced than the phase‐delaying effects. Our results provide the first evidence that light is capable of phase shifting the 5‐methoxytryptophol rhythm in a manner similar to its action on the melatonin rhythm.