melanopsincontaining

Melanopsin-containing refers to cells that express melanopsin, a light-sensitive photopigment encoded by the OPN4 gene. In mammals, the best known melanopsin-containing cells are the intrinsically photosensitive retinal ganglion cells (ipRGCs) of the retina. These cells can respond to light independently of rods and cones, providing non-image-forming visual information.

Melanopsin signals through a G protein-coupled pathway (Gq/11), activating phospholipase C and increasing intracellular calcium, with peak sensitivity around 480 nm (blue light). ipRGCs project to brain regions such as the suprachiasmatic nucleus (SCN), which coordinates circadian rhythms, and the olivary pretectal nucleus (OPN) for pupil constriction; other projections reach areas involved in alertness, mood, and sleep regulation.

Subtypes M1–M6 differ in morphology and projection patterns; M1 cells predominantly influence circadian entrainment via the SCN, while other subtypes contribute to pupil responses and potentially residual image-forming pathways. In humans, melanopsin-containing cells contribute to pupil light reflex and circadian photoentrainment; changes with age or disease can affect sleep and circadian rhythms.

They are widely used as markers of ipRGCs in research and as a model for studying light–brain interactions. Overall, melanopsin-containing describes cells or tissues that express melanopsin and participate in non-image-forming responses to ambient light.