Melanopsin Retinal Ganglion Cells
A subset of retinal ganglion cells characterized by their expression of melanopsin and their ability to respond directly to light. Melanopsin is an opsin protein structurally and phylogenetically related to rod and cone opsins. It binds retinaldehyde as a chromophore and activates a G-protein signaling cascade upon photon absorption. As a result, melanopsin retinal ganglion cells are depolarized by light even when physically, pharmacologically, or genetically isolated from rod and cone influences. This allows them to function as an independent origin of visual information. mRGCs are known to encode environmental brightness for such visual reflexes as circadian photoentrainment and regulating pupil size. They likely also make as yet ill-defined contributions to other visual processes including perceptual vision.
Discovery and Functions
Until around the...
KeywordsRetinal Ganglion Cell Amacrine Cell Perceptual Vision Pupil Light Cone Opsin