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Author (up) Gooley, J.J.; Rajaratnam, S.M.W.; Brainard, G.C.; Kronauer, R.E.; Czeisler, C.A.; Lockley, S.W.
Title Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light Type Journal Article
Year 2010 Publication Science Translational Medicine Abbreviated Journal Sci Transl Med
Volume 2 Issue 31 Pages 31ra33
Keywords Adolescent; Adult; Circadian Rhythm/physiology/*radiation effects; Dose-Response Relationship, Radiation; Humans; Light; Melatonin/secretion; Photoperiod; Phototherapy; Retina/physiology/radiation effects; Retinal Cone Photoreceptor Cells/physiology/radiation effects; Retinal Ganglion Cells/physiology/radiation effects; Rod Opsins/physiology; Young Adult; blue light; light at night; melatonin; melanopsin; light therapy
Abstract In humans, modulation of circadian rhythms by light is thought to be mediated primarily by melanopsin-containing retinal ganglion cells, not rods or cones. Melanopsin cells are intrinsically blue light-sensitive but also receive input from visual photoreceptors. We therefore tested in humans whether cone photoreceptors contribute to the regulation of circadian and neuroendocrine light responses. Dose-response curves for melatonin suppression and circadian phase resetting were constructed in subjects exposed to blue (460 nm) or green (555 nm) light near the onset of nocturnal melatonin secretion. At the beginning of the intervention, 555-nm light was equally effective as 460-nm light at suppressing melatonin, suggesting a significant contribution from the three-cone visual system (lambda(max) = 555 nm). During the light exposure, however, the spectral sensitivity to 555-nm light decayed exponentially relative to 460-nm light. For phase-resetting responses, the effects of exposure to low-irradiance 555-nm light were too large relative to 460-nm light to be explained solely by the activation of melanopsin. Our findings suggest that cone photoreceptors contribute substantially to nonvisual responses at the beginning of a light exposure and at low irradiances, whereas melanopsin appears to be the primary circadian photopigment in response to long-duration light exposure and at high irradiances. These results suggest that light therapy for sleep disorders and other indications might be optimized by stimulating both photoreceptor systems.
Address Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1946-6234 ISBN Medium
Area Expedition Conference
Notes PMID:20463367 Approved no
Call Number IDA @ john @ Serial 294
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