The in vitro frog pigment epithelial cell hyperpolarization in response to light

Pigment epithelial cell membrane potentials were measured in an in vitro frog retina-pigment epithelium-choroid preparation. Light stimuli hyperpolarized the apical membrane of the pigment epithelium. This hyperpolarization was the source of the c-wave of the electroretinogram. Light stimuli also decreased retinal extracellular potassium ion concentration, [K+]O, with the same time course as the apical hyperpolarization. It is suggested that the pigment epithelial hyperpolarization, which causes the c-wave, results directly from the light-evoked decrease in retinal [K+]O.