Xenbase Image ID: 122280

Figure 4. . Responses of Xenopus rods to saturating flashes. (A) Responses of tadpole (black) and froglet (gray) rods to saturating flashes producing ∼6 × 103 photoisomerizations were recorded. Responses of froglet rods recovered faster from saturation than tadpole rods. Responses were normalized relative to their respective saturating currents. (B) Time to 50% recovery from saturation as a function of the number of photoisomerizations (R*) elicited by a saturating flash was measured. The recovery time of tadpole rods (black circles, n = 9) increased with flash intensity. Two linear segments were used to fit the data. The dominant time constant value of 2.5 s was estimated from the slope of the shallow segment. In response to flashes producing the same number of photoisomerizations, froglet rods (triangles, n = 8) recovered approximately twice as fast as tadpole rods. Recovery time of froglet rods increased with intensity at the same rate as that of tadpole rods but more intense flashes (15×) were required to produce similar recovery times. Displacement of the tadpole data by 2.7 ln units brought the two curves to a close match (gray circles). However, only a 0.5 ln units shift along the abscissa can be accounted for by the 1.6-fold increase in amplification in the tadpole rods. Therefore, the remaining ∼10-fold difference must result from a stronger shutoff mechanism present in froglet rods. Image published in: Solessio E et al. (2004) Copyright © 2004, The Rockefeller University Press. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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