Melanopsin Is Required for Non-Image-Forming Photic Responses in Blind Mice

Mice lacking both outer-retinal photoreceptors and melanopsin exhibited a complete loss of photoentrainment and other light-mediated responses.

• Mice that are blind due to the absence of rod and cone photoreceptors still show some responses to light.
• Photosensitive retinal ganglion cells, which contain the photopigment melanopsin, may mediate these responses.
• Mice without melanopsin also retain some nonvisual photoreception, suggesting alternative pathways for light detection.
• The absence of both outer-retinal photoreceptors and melanopsin leads to loss of key light-mediated functions, such as circadian rhythm regulation and pupil constriction.
• These findings highlight the roles of both nonvisual and classical visual photoreceptors in light responses in mammals.

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