Phototransduction, Dark Adaptation, and Rhodopsin Regeneration: The Proctor Lecture

This article is divided into two sections. The first outlines the molecular events that underlie the onset of phototransduction, the photoreceptor’s response to light, and provides a quantitative model of its kinetics and amplification. Light responses measured both with single-cell techniques and with the electroretinogram (ERG) are compared with the predictions of the model, and an account is given of the differences in gain between amphibian and mammalian rods. The second section turns to recovery of the overall visual system after exposure of the eye to very intense “bleaching” exposures, and describes the cellular and molecular mechanisms involved in the regeneration of rhodopsin. A model is presented for the delivery of 11-cis retinal to opsin in the bleached rods, which accounts for the kinetics of psychophysical dark adaptation and rhodopsin regeneration, both in normal subjects and in a range of disease states.