Transient sensitivity reduction and biphasic photoresponses observed when frog retinal rods are oxidized

1. Rod photoresponses and the effects of oxidation have been studied by recording either the transretinal voltage in aspartate-treated retinas or the outer segment current of single rods. 2. Oxidizing conditions transiently decreased, reducing conditions increased sensitivity. 3. Biphasic photoresponses were seen when the level of oxidation was rising and also in some other sensitivity-depressing conditions. 4. A model is proposed which explains the biphasic responses in terms of sensitivity differences between the tip and the base of the rod outer segment.