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J Biol Rhythms. 2015 Aug;30(4):351-4. doi: 10.1177/0748730415585413. Epub 2015 May 27.

Melatonin Suppression by Light in Humans Is More Sensitive Than Previously Reported.

Author information

1
Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA Graduate Program in Macromolecular Science & Engineering, University of Michigan, Ann Arbor, Michigan, USA.
2
Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA.
3
Department of Mathematics, University of Michigan, Ann Arbor, Michigan, USA.
4
Department of Biosciences, University of Helsinki, Helsinki, Finland Department of Neuroscience and Biomedical Engineering (NBE), Aalto University School of Science and Technology, Espoo, Finland.
5
Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA Department of Molecular, Cellular & Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA kwoon@umich.edu.

Abstract

The retina drives various non-image-forming photoresponses, including circadian photoentrainment and pupil constriction. Previous investigators showed that in humans, photic suppression of the clock-controlled hormone melatonin is most sensitive to 460-nm blue light, with a threshold of ~12 log photons cm(-2) s(-1). This threshold is surprising because non-image-forming vision is mediated by intrinsically photosensitive retinal ganglion cells, which receive rod-driven synaptic input and can respond to light levels as low as ~7 log photons cm(-2) s(-1). Using a protocol that enhances data precision, we have found the threshold for human melatonin suppression to be ~10 log photons cm(-2) s(-1) at 460 nm. This finding has far-reaching implications since there is mounting evidence that nocturnal activation of the circadian system can be harmful.

KEYWORDS:

circadian photoentrainment; human; ipRGC; light; melatonin; pineal; retinal ganglion cell; threshold

PMID:
26017927
PMCID:
PMC4499476
DOI:
10.1177/0748730415585413
[Indexed for MEDLINE]
Free PMC Article

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