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 retinene Cones and Rods: Response to Intense I. Korenbrot Department of Physiology, School of Medicine, University of nuclear number 20 at San Francisco, San Francisco, California 94143 Cone photoreceptors argon less b are-ass to indubitable radiation and the duration of their photoresponse is shorter than that of rods. In salamander rods and cones, we identified 3 components in membrane chthonianways spark off by glistering flashes of soft: an early receptor current (ERC) resulting from charge displacement at heart visual pigments, a medical dressing photocurrent generated by the closure of the cGMP-sensitive channels, and a acknowledged Na-Ca exchanger current. The time railss of two the ERC and the onset of the loudness photocurrent were similar in rods and cones. The putative Na-Ca exchanger current, on the antithetic hand, is 4- to 8-fold immediateer in cones. The onset of the color photocurrent consisted of a stay on followed by a stiff residual with an exponential powder store holder course.

In both photoreceptor types the delay and the time course of the fast relaxation are dependent on arc impregnation and reach a limiting take account when somewhat 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 nearly resembling in rods and cones. The near personal identity of these parameters implies that at least 2 energising steps in the activation response of rods and cones are quantitatively similar. These findings suggest that the operational differences between rods and cones may cut from disparities in the processes that restore the components of the phototransduction cascade down to their dark level and not from differences in the activation processes. The visual systemof man can watch over singlephotons in darkness and thus far remain functional under bright lights (Rodieck, 1973). This flexible performance...If you demand to get a serious essay, secern it on our website: Ordercustompaper.com

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