title: Calcium and calcium-dependent chloride currents generate action potentials in solitary cone photoreceptors.
abstract: Vertebrate rod and cone photoreceptors hyperpolarize when illuminated. However, synaptic input from horizontal cells can depolarize cones and even elicit action potentials. Using the whole-cell tight-seal recording technique, we determined that, in solitary cones isolated from a lizard retina, action potentials can be generated by depolarizing current steps under conditions where only two ionic currents are activated. A dihydropyridine-sensitive, inward Ca2+ current that activates at potentials positive to -40 mV can regeneratively depolarize the cell. Subsequently, a SITS-sensitive, Ca2(+)-dependent outward Cl- current repolarizes the cell. We suggest that these ionic currents may help explain lateral inhibition in the retina.
authors: Department of Physiology School of Medicine, University of California, San Francisco 94143.
authors: A V
authors: AV
authors: Maricq
authors: J I
authors: JI
authors: Korenbrot
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D018118:Chloride Channels; D002712:Chlorides / Q000502:physiology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008116:Lizards; D008565:Membrane Proteins / Q000502:physiology*; D010786:Photoreceptor Cells / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D002118:Calcium