Mechanism of Current Production found in Pigeon Cones but not in Pigeon or Rat Rods

Abstract

As an approach towards understanding the way in which the absorption of light by visual pigments initiates the excitation of rods and cones, we have altered the ionic composition of the fluids bathing the isolated, incubated retinas of pigeons and rats. To investigate the effects so produced we have recorded a fraction of the electroretinogram, PIII¹, for this is believed to arise from the receptors themselves^2–5. Though there have been several previous studies of the effects of various ions on the electroretinogram (ERG)^6–8, interpretation of the results in terms of the excitation of receptors is difficult, because cells other than receptors contribute to the ERG. We therefore isolated PIII as previously described⁹. The experimental procedure was very similar to that described by other workers^10,11. A retina was dissected and mounted in a ‘Perspex’ chamber so that it formed a membrane between two pools of solution into which dipped Ag/AgCl electrodes. Responses to light of up to 0.5 mV were recorded.