Figure 5.
Acceleration of the photocurrent by 8-Br-cGMP resembles light adaptation effects. A, Left, Superimposed flash responses (4.95 × 1013 photons × cm-2) in a control photoreceptor stimulated under dark-adapted conditions and subsequently during exposure to sustained background illumination (4.2 × 1013 photons · cm-2 · s-1). Right, The same two traces were normalized with respect to their peak amplitude (Norm. Ampl.), revealing a pronounced acceleration in response kinetics after light adaptation. B, A similar comparison is made between the dark-adapted responses in one control cell and one dialyzed with 20 μm 8-Br-cGMP. Again, the treatment caused not only a reduction in photocurrent amplitude but also a more rapid time course. C, Flash response speed, measured as the FWHM of the light-evoked current, in control conditions and during perfusion with increasing concentrations of 8-Br-cGMP, in separate groups of cells. Error bars denote SD.