Interactions Between Calcium and cGMP in Dialyzed Detached Retinal Rod Outer Segments. In: Hargrave PA, Hofmann KP, Kaupp UB, editors. Signal Transduction in Photoreceptor Cells. Berlin: Springer Berlin Heidelberg; 1992. pp. 217-35. [DOI: 10.1007/978-3-642-76482-0_16]

Ca2+ dependence of dark- and light-adapted flash responses in rod photoreceptors

Light adaptation is thought to be orchestrated by a Ca2+ feedback signal that desensitizes the response by speeding recovery. To evaluate the role of Ca2+ in adaptation, we compared the effect of lowered Ca2+ on response properties in darkness and during adaptation. Internal Ca2+ was reduced from its normal resting dark level (535 nM) by either background illumination or exposure to Ringer's solution containing low Ca2+ and/or cyclic GMP-gated channel blockers in darkness. Ca2+ reductions in light decreased the activation gain of the transduction process and speeded recovery kinetics, while equivalent Ca2+ reductions in darkness caused similar gain reduction without accelerating recovery. This indicates that adaptational changes in the response are not due purely to feedback effects on recovery.