cGMP-gated conductance in retinal bipolar cells is suppressed by the photoreceptor transmitter.
Transmitter release from photoreceptors is decreased by light, resulting in a conductance increase in depolarizing bipolar cells. Addition of exogenous cGMP through a patch pipette to depolarizing bipolar cells from slices of dark-adapted tiger salamander retina resulted in an enhancement of the light response. This enhancement was blocked by GTP-gamma-S and dipyridamole, an inhibitor of phosphodiesterase. GTP-gamma-S and dipyridamole also blocked responses to exogenously applied 2-amino-4-phosphonobutyrate (APB), the glutamate agonist selective for this receptor. These data support the hypothesis that the postsynaptic receptor is linked via a G protein to a phosphodiesterase. The binding of glutamate or APB to the receptor suppresses a cGMP-activated current by increasing the rate of cyclic nucleotide hydrolysis.
Vollum Institute, Oregon Health Sciences University, Portland 97201.
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D000470:Alkaloids / Q000494:pharmacology; D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism / Q000502:physiology*; D003623:Dark Adaptation; D004176:Dipyridamole / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D008027:Light; D018377:Neurotransmitter Agents / Q000378:metabolism / Q000502:physiology*; D010703:Phorbol Esters / Q000494:pharmacology; D010786:Photoreceptor Cells / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D019311:Staurosporine
D000470:Alkaloids; D000613:Aminobutyrates; D018377:Neurotransmitter Agents; D010703:Phorbol Esters; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004176:Dipyridamole; D006152:Cyclic GMP; D019311:Staurosporine; C012729:2-amino-4-phosphonobutyric acid