Changes in [K+]0 induced by transretinal currents in frog retina.

Current-induced changes in extracellular potassium concentration (delta [K+]0) were measured with K+-selective microelectrodes in frog retina. A characteristic depth profile of delta[K+]0 was detected, which included significant changes in the superfusate just above the inner limiting membrane. This response was almost eliminated by Ba2+, a blocker of K+ channels. The delta[K+]0 in the superfusate is likely due to transcellular flux of K+, probably through Muller cell endfeet.