Melanopsin

This is a photopigment that is responsible for the light sensitivity of the retinal ganglion cells. Its sensitivity can be described by the action spectrum for melatonin suppression, with a maximum at around 464 nm – in other words at the blue end of the spectrum. Through the absorption of light, melanopsin transmits the nerve signals that lead to the suppression of melatonin. Opsin is the general term for a light-sensitive pigment (photopigment) in the eye. The pigment undergoes a change when it absorbs photons (quantums of light), releasing a chemical signal chain at the end of which is a conversion to electrical signals in the nervous system. The pigment in the rods for light/dark vision is rhodopsin; the pigments in the cones are iodopsin, porphyrosin and cyanopsin.