ATP receptor antagonist blocks asymmetric wave propagation. Superfusate flow is from top left to bottom right in all three trials.A, Control. Superfusate flow causes asymmetric wave propagation. B, Suramin, 100 μm. The purinergic receptor blocker eliminates the asymmetric wave propagation despite the continued superfusate flow. C, Recovery. After washout of suramin (39 min) the asymmetry in wave propagation returns. Waves were evoked by mechanical stimulation. The three images were obtained from nearby regions of the same retina. Shown are recordings from a whole-mount retina. Scale bar, 50 μm.