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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.

Original publication




Journal article



Publication Date





245 - 247


Adaptation, Ocular, Animals, Carbachol, Circadian Rhythm, Darkness, Light, Light Signal Transduction, Mice, Mice, Inbred C57BL, Mice, Knockout, Olivary Nucleus, Phenotype, Photoreceptor Cells, Vertebrate, Pupil, Reflex, Pupillary, Retinal Degeneration, Retinal Ganglion Cells, Rod Opsins, Suprachiasmatic Nucleus