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

A decrease in extracellular potassium concentration [( K+]o) was caused by injecting a small amount of K+ -free Ringer's solution into the photoreceptor layer of the isolated frog retina. The response induced by K+ -free Ringer's solution was receptor side-positive, and the depth profile of the response resembled that of the response (slow P III) induced by spot illumination. This result supports the notion that the slow P III is generated by Müller cells as they hyperpolarize in response to a light-induced decrease in [K+]o in the photoreceptor layer.