title: Melatonin Suppression by Light in Humans Is More Sensitive Than Previously Reported.
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.
authors.affiliation: 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.
authors.forename: Garen V
authors.initials: GV
authors.lastname: Vartanian
authors.affiliation: Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Benjamin Y
authors.initials: BY
authors.lastname: Li
authors.affiliation: Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Chervenak
authors.affiliation: Department of Mathematics, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Olivia J
authors.initials: OJ
authors.lastname: Walch
authors.affiliation: Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Weston
authors.initials: W
authors.lastname: Pack
authors.affiliation: Department of Biosciences, University of Helsinki, Helsinki, Finland Department of Neuroscience and Biomedical Engineering (NBE), Aalto University School of Science and Technology, Espoo, Finland.
authors.forename: Petri
authors.initials: P
authors.lastname: Ala-Laurila
authors.affiliation: 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.
authors.forename: Kwoon Y
authors.initials: KY
authors.lastname: Wong
mesh_terms: D002940:Circadian Rhythm / Q000502:physiology*; D006801:Humans; D008027:Light / Q000009:adverse effects*; D008550:Melatonin / Q000378:metabolism*; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology; D012160:Retina / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology; D017299:Rod Opsins / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology
chemical_list: D017299:Rod Opsins; D008550:Melatonin
keywords: circadian photoentrainment; human; ipRGC; light; melatonin; pineal; retinal ganglion cell; threshold