Dopamine hyperpolarizes and reduces the light responses of rod ON-centre bipolar cells in the retina of the dogfish, Scyliorhinus canicula.
Intracellular recordings were obtained from horizontal cells and bipolar cells of the dark-adapted, virtually all-rod retina of the dogfish. Eyecups were superfused with Ringer's solution containing micromolar concentrations of dopamine (DA). It was found that 10 microM DA hyperpolarized rod ON-centre bipolar cells and reduced their responses to light flashes. Detectable effects could be obtained with DA concentrations as low as 1 microM. A decrease in the light responses of bipolar cells due to the effects of DA was concomitant with a decrease in the amplitude of the b-wave of the electroretinogram. DA had no effect on the membrane potential or the light response of rod horizontal cells. These results demonstrate a selective action on rod ON-centre bipolar cells and suggest the existence of a dopaminergic pathway which affects the sensitivity of the rod visual system at the retinal level.
D000818:Animals; D004284:Dogfish / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D004594:Electrophysiology; D004596:Electroretinography; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects / Q000528:radiation effects; D010786:Photoreceptor Cells / Q000166:cytology / Q000528:radiation effects*; D012754:Sharks / Q000502:physiology*
D004298:Dopamine