Abstract
In vertebrate rod outer segments phototransduction is suggested to be modulated by intracellular Ca. We aimed at verifying this hypothesis by recording saturated photosignals in the rat retina after single and double flashes of light and determining the time t c to the beginning of the signal recovery. The time course of Ca i after a flash was calculated from a change of the spatial Ca 2+ concentration profile recorded in the space between the rods. After single flashes t c increased linearly with the logarithm of flash intensity, confirming the assumption that t c is determined by deactivation of a single species X* in the phototransduction cascade. The photoresponse was shortened up to 45% if the test flash was preceded by a conditioning preflash. The shortening depended on the reduction of Ca i induced by the preflash. The data suggest that the phototransduction gain determining the amount of activated X* is regulated by a Ca i-dependent mechanism in a short time period (<800 ms) after the test flash. Lowering of Ca i by a preflash reduced the gain up to 20% compared to its value in a dark-adapted rod. The relation between phototransduction gain and Ca i revealed a K 1/2 value close to the dark level of Ca i.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
