Effects of barium on separately recorded fast and slow PIII responses in bullfrog retina

Investigation of Ba2+ effects on fast and slow PIII responses in isolated bullfrog retina revealed that Ba2+ suppressed slow PIII completely with little effect on fast PIII. A light-induced [K+]0 decrease in the photoreceptor layer was observed in spite of Ba2+ perfusion, indicating the suppressive action of Ba2+ on the K+ conductance of the Müller cell membrane.