Neuron
Volume 66, Issue 3, 13 May 2010, Pages 417-428
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Article
Distinct Contributions of Rod, Cone, and Melanopsin Photoreceptors to Encoding Irradiance

https://doi.org/10.1016/j.neuron.2010.04.037Get rights and content
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Summary

Photoreceptive, melanopsin-expressing retinal ganglion cells (mRGCs) encode ambient light (irradiance) for the circadian clock, the pupillomotor system, and other influential behavioral/physiological responses. mRGCs are activated both by their intrinsic phototransduction cascade and by the rods and cones. However, the individual contribution of each photoreceptor class to irradiance responses remains unclear. We address this deficit using mice expressing human red cone opsin, in which rod-, cone-, and melanopsin-dependent responses can be identified by their distinct spectral sensitivity. Our data reveal an unexpectedly important role for rods. These photoreceptors define circadian responses at very dim “scotopic” light levels but also at irradiances at which pattern vision relies heavily on cones. By contrast, cone input to irradiance responses dissipates following light adaptation to the extent that these receptors make a very limited contribution to circadian and pupillary light responses under these conditions. Our data provide new insight into retinal circuitry upstream of mRGCs and optimal stimuli for eliciting irradiance responses.

Highlights

► Red cone knockin (Opn1mwR) mice reveal rod, cone, and melanopsin phases to NIF vision ► Rods drive circadian responses to very low irradiances (scotopic threshold) ► Circadian responses to light in the photopic range can be rod driven ► Light adaptation limits the influence of cones on NIF vision

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Cited by (0)

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Present address: Medway School of Pharmacy, University of Kent, Chatham ME4 4TB, UK

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Present address: Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK

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Present address: Warwick Systems Biology Centre, University of Warwick, Coventry CV4 7AL, UK; and Warwick HRI, University of Warwick, Wellesbourne, Warwick CV35 9EF, UK