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Science. 2003 Jan 10;299(5604):245-7.

Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice.

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Department of Integrative and Molecular Neuroscience, Division of Neuroscience and Psychological Medicine, Faculty of Medicine, Imperial College London, Charing Cross Campus, St. Dunstans Road, London W6 8RF, UK.


In the mammalian retina, a small subset of retinal ganglion cells (RGCs) are intrinsically photosensitive, express the opsin-like protein melanopsin, and project to brain nuclei involved in non-image-forming visual functions such as pupillary light reflex and circadian photoentrainment. We report that in mice with the melanopsin gene ablated, RGCs retrograde-labeled from the suprachiasmatic nuclei were no longer intrinsically photosensitive, although their number, morphology, and projections were unchanged. These animals showed a pupillary light reflex indistinguishable from that of the wild type at low irradiances, but at high irradiances the reflex was incomplete, a pattern that suggests that the melanopsin-associated system and the classical rod/cone system are complementary in function.

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