Bleaching of mouse rods: microspectrophotometry and suction-electrode recording

Key points  • When photoreceptors in vertebrate retina are exposed to bright light, a significant proportion of the photopigment in the rods can be bleached. • Bleaching produces a desensitization of the visual system that recovers slowly as pigment is slowly regenerated, by a process known as dark adaptation. • Experiments on isolated amphibian rods have revealed some of the features of bleach-induced desensitization, but such experiments have not so far been possible on mammals. • We now describe an improved method that makes possible the first direct measurements of pigment concentration and rod photoreceptor responses over a wide range of bleaching exposures from isolated cells or pieces of intact mammalian retina. • Our experiments reveal important features of mammalian bleaching adaptation and will now make possible future studies from mouse animal lines containing genetically altered photoreceptor proteins.