Molecular Mechanism of Light-Adaptation in Retinal Photoreceptors

Abstract

Vertebrate retinal photoreceptors respond to light by membrane hyperpolarization. The generation mechanism of the photoresponse, namely the phototransduction mechanism is now well characterized. Photoreceptors not only detect light, but also actively adapt to environmental light. Recent biochemical and electrophysiological studies uncovered the mechanism of light-adaptation. In this mechanism, light-induced decrease in the cytoplasmic [Ca2+] plays a major role: The [Ca2+] decrease induces the desensitization of the cell and the acceleration of the time course of the photoresponse. These effects are mediated by Ca2+-binding proteins named S-modulin and GCAP. © 1994, The Keio Journal of Medicine. All rights reserved.