Simulation of the electroretinographic slow PIII component by injection of K+ -free Ringer's solution in the frog retina.

The light-induced hyperpolarization of the photoreceptor results in a decrease in extracellular potassium ion concentration, [K+]. A decrease in [K+] in the photoreceptor layer was caused by injecting a small amount of K+-free Ringer's solution in the isolated frog retina, and the distribution of the field potential as induced by K+-free Ringer's solution was mapped. The depth profile of the response resembled that of the slow PIII component of the electroretinogram. These results support the notion that the slow PIII is generated by the Müller cells as they hyperpolarize in response to a light-induced decrease in [K+] in the photoreceptor layer.