How rod, cone, and melanopsin photoreceptors come together to enlighten the mammalian circadian clock

Lucas, Robert J and Lall, Gurprit S. and Allen, Annette E and Brown, Timothy M (2012) How rod, cone, and melanopsin photoreceptors come together to enlighten the mammalian circadian clock. Progress in brain research, 199 (1). pp. 1-18. ISSN 0079-6123. (doi:https://doi.org/10.1016/B978-0-444-59427-3.00001-0) (Access to this publication is currently restricted. You may be able to access a copy if URLs are provided)

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Abstract

In mammals, a small number of retinal ganglion cells express melanopsin, an opsin photopigment, allowing them to be directly photoreceptive. A major function of these so-called intrinsically photosensitive retinal ganglion cells (ipRGCs) is to synchronize (entrain) endogenous circadian clocks to the external light:dark cycle. Thanks to their intrinsic light response, ipRGCs can support photoentrainment even when the other retinal photoreceptors (rods and cones) are absent or inactive. However, in the intact retina the ipRGC light response is a composite of extrinsic (rod/cone) and intrinsic (melanopsin) influences. As a result all three photoreceptor classes contribute to the retinal pathways providing light information to the clock. Here, we consider what each photoreceptor type contributes to the clock light response. We review electrophysiological and behavioral data pertinent to this question, primarily from laboratory rodents, drawing them together to provide a conceptual model in which each photoreceptor class plays a distinct role in encoding the light environment. We finally use this model to highlight some of the important outstanding questions in this field.

Item Type: Article
Uncontrolled keywords: circadian; photoentrainment; melanopsin; ipRGCs; photoreceptor; rods; cones; suprachiasmatic nuclei; retinohypothalamic tract
Subjects: R Medicine
Divisions: Faculties > Sciences > Medway School of Pharmacy
Depositing User: Gurprit Lall
Date Deposited: 17 Nov 2014 15:49 UTC
Last Modified: 08 May 2018 08:47 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/44733 (The current URI for this page, for reference purposes)
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