Review

Article, Biology -Melanopsin, the circadian photoreceptor Mammals have intrinsically photosensitive retinal ganglion cells (ipRGCs) that are capable of forming non-images that results to formation of visual functions, for instance, the pupillary light reflex (PLR) and the circadian photoentrainment. The photosensitivy performs efficiently under Melonopsin, which resembles an Opsin that is protein in nature and produced by the ipRGCS.
However, it is uncertain whether Melonopsin works like a photo pigment or rather as a photoisomerase. Investigations conducted illustrate that Melonopsin functions as a photoisomerase most probably in the mouse retinal pigment epithelium (RPE). The paper aims at investigating whether Vitamin A -based chromophore is essential in photo reception by the ipRGS. In addition, the paper seeks to investigate the function of melanopsin in signaling the photo-pigments. In responding to these uncertainty, the paper studies a knock-out mouse line which lacks the RPE65 (rpe65–/–), which is a substantial protein that regenerates the 11–cis–retinal in the RPE.
In essence, the paper succinctly covers the topic by ascertaining that there are other photo receptors within the mammalian retina other than the known rods and cones. The main concept behind this paper is to have a clear understanding of the diversity of the ipRGCs and their different functions in regulating behavior.
The findings illustrate that Rpe65–/– ipRGCs were 20–40–fold and are not photosensitive whether at single cell or behavioral (PLR) levels. The photosensitivity detected is expressed by exogenous 9–cis–retinal, an 11–cis–retinal analog.
In addition, there was no detection of Melanopsin in the retinal pigment epithelium or any results both in the rod and cone sensitivities. This is a factor that led to ablation of Melanopsin in both the ERG and single cell recordings.
It was, therefore, concluded that Vitamin A- based chromophore is required for ipGGC photosensitivy and Melanopsin and it is probably the photopigment present in ipRGCs.
Work Cited
Yingbin Fu Et al. (July 12, 2005). Intrinsically photosensitive retinal ganglion cells, detect light with a vitamin A-based photopigment, melanopsin.
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