Mechanisms regulating variability of the single photon responses of mammalian rod photoreceptors.
Variability in the single photon responses of rod photoreceptors limits the accuracy with which the number and timing of photon absorptions are encoded. We investigated how much single photon responses of mammalian rods fluctuate and what mechanisms control these fluctuations. Mammalian rods, like those of toads, generated responses to single photons with trial-to-trial fluctuations 3-4 times smaller than other familiar signals produced by single molecules. We used the properties of the measured fluctuations to constrain models for how the single photon responses are regulated. Neither feedback control of rhodopsin's activity nor saturation within the transduction cascade were consistent with experiment. The measured responses, however, could be explained by multistep shutoff of rhodopsin or a combination of multistep shutoff and saturation.
Department of Physiology and Biophysics, University of Washington, 98195, Seattle, WA, USA
Greg D
GD
Field
Fred
F
Rieke
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D005246:Feedback / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D007473:Ion Channels / Q000378:metabolism; D008252:Macaca fascicularis; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008959:Models, Neurological; D010215:Papio; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010775:Photic Stimulation; D017785:Photons; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism*; D015293:Transducin / Q000378:metabolism; D014785:Vision, Ocular / Q000187:drug effects / Q000502:physiology*
D002614:Chelating Agents; D007473:Ion Channels; D004533:Egtazic Acid; D012243:Rhodopsin; D010727:Phosphoric Diester Hydrolases; D015293:Transducin; D006152:Cyclic GMP; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium