This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (7) Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Jasser, S. A. Articles by Brainard, G. C. Search for Related Content PubMed PubMed Citation Articles by Jasser, S. A. Articles by Brainard, G. C. Social Bookmarking                         What's this?

Dim Light Adaptation Attenuates Acute Melatonin Suppression in Humans

John P. Hanifin

Mark D. Rollag

George C. Brainard

Department of Neurology, Thomas Jefferson University, Philadelphia, PA

Abstract Studies in rodents with retinal degeneration indicated that neither the rod nor the cone photoreceptors obligatorily participate in circadian responses to light, including melatonin suppression and photoperiodic response. Yet there is a residual phase-shifting response in melanopsin knockout mice, which suggests an alternate or redundant means for light input to the SCN of the hypothalamus. The findings of Aggelopoulos and Meissl suggest a complex, dynamic interrelationship between the classic visual photoreceptors and SCN cell sensitivity to light stimuli, relative to various adaptive lighting conditions. These studies raised the possibility that the phototransductive physiology of the retinohypothalamic tract in humans might be modulated by the visual rod and cone photoreceptors. The aim of the following two-part study was to test the hypothesis that dim light adaptation will dampen the subsequent suppression of melatonin by monochromatic light in healthy human subjects. Each experiment included 5 female and 3 male human subjects between the ages of 18 and 30 years, with normal color vision. Dim white light and darkness adaptation exposures occurred between midnight and 0200 h, and a full-field 460-nm light exposure subsequently occurred between 0200 and 0330-h for each adaptation condition, at 2 different intensities. Plasma samples were drawn following the 2-h adaptation, as well as after the 460-nm monochromatic light exposure, and melatonin was measured by radioimmunoassay. Comparison of melatonin suppression responses to monochromatic light in both studies revealed a loss of significant suppression after dim white light adaptation compared with dark adaptation (p < 0.04 and p < 0.01). These findings indicate that the activity of the novel circadian photoreceptive system in humans is subject to subthreshold modulation of its sensitivity to subsequent monochromatic light exposure, varying with the conditions of light adaptation prior to exposure.

Key Words: adaptation • circadian rhythm • melanopsin • melatonin • pineal • photoreception • suprachiasmatic nucleus

Journal of Biological Rhythms, Vol. 21, No. 5, 394-404 (2006)
DOI: 10.1177/0748730406292391


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				D. G.M. Beersma, M. Comas, R. A. Hut, M. C.M. Gordijn, M. Rueger, and S. Daan The Progression of Circadian Phase during Light Exposure in Animals and Humans J Biol Rhythms, April 1, 2009; 24(2): 153 - 160. [Abstract] [PDF]

				G. C. Brainard, D. Sliney, J. P. Hanifin, G. Glickman, B. Byrne, J. M. Greeson, S. Jasser, E. Gerner, and M. D. Rollag Sensitivity of the Human Circadian System to Short-Wavelength (420-nm) Light J Biol Rhythms, October 1, 2008; 23(5): 379 - 386. [Abstract] [PDF]

				M. Rufiange, C. Beaulieu, P. Lachapelle, and M. Dumont Circadian Light Sensitivity and Rate of Retinal Dark Adaptation in Indoor and Outdoor Workers J Biol Rhythms, October 1, 2007; 22(5): 454 - 457. [PDF]