Mechanisms of azide induced increases in the c-wave and standing potential of the intact cat eye

The c-wave of the ERG and the standing potential of the eye both undergo increases in amplitude following intravenous infusions of sodium azide (NaN₃), as first shown by Noell [Am. J. Physiol. 170, 217-238 (1952); U.S.A.F. School of Aviation Medicine, Project No. 21-1201-0004 (1953)]. We have studied the mechanism of these changes in the intact cat eye. Intraretinal and intracellular retinal pigment epithelial (RPE) cell recordings show that most of the change occurs at the RPE, but that there is a small direct effect on the neural retina. The increase of standing potential is caused by a depolarization of the basal membrane of the RPE, and the increase in c-wave amplitude results from a decrease in basal membrane resistance that accompanies the depolarization. This relation between basal membrane potential and resistance is similar to that observed during hypoxia and during the light peak of the d.c. ERG.