LIGHT-INDUCED RESISTANCE CHANGES IN SINGLE PHOTORECEPTORS OF NECTURUS AND GEKKO

Intracellular recordings from single photoreceptors of Necturus maculosus and Gekko gekko reveal that the response to light is a hyperpolarization accompanied by an increase in resistance. Passive hyperpolarization of the membrane by extrinsic current does not change the membrane resistance but makes the hyperpolarizing response to light larger. By applying a depolarizing current, the response is made smaller, or even inverted if the current is strong enough. It is suggested that the vertebrate photoreceptor is depolarized in darkness and repolarized in light. This new viewpoint accounts for the unusual polarity of the ERG component ascribed to the receptors. The electrogenesis of the S potential is also discussed in relation to the receptor potential. © 1969.