Details

Autor(en) / Beteiligte

• Sexton, Timothy
• Buhr, Ethan
• Van Gelder, Russell N.

Titel

Melanopsin and Mechanisms of Non-visual Ocular Photoreception

Ist Teil von

• The Journal of biological chemistry, 2012-01, Vol.287 (3), p.1649-1656

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2012

Quelle

MEDLINE

Beschreibungen/Notizen

• In addition to rods and cones, the mammalian eye contains a third class of photoreceptor, the intrinsically photosensitive retinal ganglion cell (ipRGC). ipRGCs are heterogeneous irradiance-encoding neurons that primarily project to non-visual areas of the brain. Characteristics of ipRGC light responses differ significantly from those of rod and cone responses, including depolarization to light, slow on- and off-latencies, and relatively low light sensitivity. All ipRGCs use melanopsin (Opn4) as their photopigment. Melanopsin resembles invertebrate rhabdomeric photopigments more than vertebrate ciliary pigments and uses a Gq signaling pathway, in contrast to the Gt pathway used by rods and cones. ipRGCs can recycle chromophore in the absence of the retinal pigment epithelium and are highly resistant to vitamin A depletion. This suggests that melanopsin employs a bistable sequential photon absorption mechanism typical of rhabdomeric opsins.