Rod and cone photoreceptors

H hstract. Until recently, all ocular photoreception was attributed to the rods and cones of the retina. However, studies on mice lacking rod and cone photoreceptors (rdjrdcl), has shown that these mice can still use their eyes to detect light to regulate their circadian rhythms, suppress pineal melatonin, modify locomotor activity and modulate pupil size. In addition, action spectra for some of these responses have characterized a novel opsin/vitamin A-based photopigment with a 480nm. Electrophysiological... 

EAAT5 (see below) is also expressed in terminals of rod photoreceptor terminals, rod photoreceptors express two glutamate transporters with distinct properties. Similarly, cone photoreceptors express two glutamate transporters. Differential usage of these transporters by rod and cone photoreceptors may influence the kinetics of glutamate transmission by these neurons (Rauen et al., 2004). 

Keywords Calcium, rod and cone photoreceptors, rod outer segments (ROS), retina, guanylate... 

Ma, J. Znoika, et. al. (2001) A visual pigment expressed in both rod and cone photoreceptors Neuron vol. 32, pp 451-461... 

Rodriguez de Turco EB, Gordon WC, Bazan NG. Rapid and selective uptake, metabohsm and cellular distribution of docosahexaenoic acid among rod and cone photoreceptor cells in the frog retina. J Neurosci 1991 lll(l) 3667-3678. 

In mammals, (1IZ)-Retinal, generated from retinol in the retina, is the photo-reactive chromophore, which forms a Schiff-base to a lysine residue of opsin, a G-protein-coupled receptor (GPCR) protein, to give rhodopsin. This visual purple is concentrated in the outer parts of the rod and cone photoreceptors. Upon light absorption, the chromophore converts photons into a chemical signal by isomerisation to (all )-retinal, which causes a conformational change of... 

F. Osakada, H. Ikeda, M. Mandai, T. Wataya, K. Watanabe, N. Yoshimura, A. Akaike, Y. Sasai, and M. Takahashi, Toward the generation of rod and cone photoreceptors from mouse, monkey and human embryonic stem cells, Nat. Biotechnol, 26 (2) 215-224, Feb. 2008. 

The retinal pigment epithelium cells (RPE) of the retina form an epithelial cell layer that takes up retinol from choroid capillaries and stores it as retinyl esters, to be used as substrate for the generation of 11-ds-retinal. In the layer of rod and cone photoreceptor cells adjacent to the RPE, 11-ds-retinal combines covalently with the protein opsin to generate the visual pigment rhodopsin in rods and, similarly, iodopsin in cones. Each rod outer segment is densely packed with some 10 molecules of rhodopsin per cell. The small quantity of vitamin A stored in the retina would be inadequate to maintain vision were it not for the visual cycle, a process in which 11-ds-retinal is regenerated after... 

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