Activation Kinetics Of Retinal Cones

The Journal of Neuroscience, June 1990, fO(6): 1967-1973 Activation Kinetics Flashes of Light Shaul Hestrin and Juan of Retinal Cones and Rods: reception to Intense I. Korenbrot Department of Physiology, School of Medicine, University of atomic number 20 at San Francisco, San Francisco, California 94143 Cone photoreceptors are less sore to visible radiation and the duration of their photo reception is shorter than that of rods. In salamander rods and cones, we set 3 components in membrane currents activated by sparkle flashes of light: an early receptor current (ERC) resulting from charge break within visual pigments, a fertilisation photocurrent generated by the blockage of the cGMP-sensitive channels, and a putative Na-Ca exchanger current. The epoch courses of both the ERC and the flack of the saturation photocurrent were similar in rods and cones. The putative Na-Ca exchanger current, on the different hand, is 4- to 8-fold immedia teer in cones. The onset of the saturation photocurrent consisted of a placate on followed by a fast relaxation with an exponential cartridge holder course.

In both photoreceptor types the delay and the beat course of the fast relaxation are dependent on light impregnation and reach a limiting determine when about 1% of the photopigment is bleached. The limiting value of the delay, about 8 msec, and of the relaxation time constant, about 2 msec, are virtually identical in rods and cones. The near identity of these parameters implies that at least(prenominal) 2 energising steps in the activation response of rods and cones are quantitatively similar. T! hese findings suggest that the useful differences between rods and cones whitethorn arise from disparities in the processes that restore the components of the phototransduction cascade to their dark take aim and not from differences in the activation processes. The visual systemof man whoremaster detect singlephotons in darkness and yet remain functional under bright lights (Rodieck, 1973). This flexible performance...If you want to get a full essay, secern it on our website: OrderCustomPaper.com

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