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We recorded light-evoked responses from rod and cone bipolar cells using patch-clamp techniques in a slice preparation of the rat retina. Rod bipolar cells responded to light with a sustained depolarization (on response) followed at light offset by a slight hyperpolarization. on and off cone bipolar cells were encountered, both with diverse temporal properties. The responses of rod bipolar cells were composed primarily of two components, a nonspecific cation current and a chloride current. The chloride current was reduced greatly in axotomized cells and could be suppressed by coapplication of the GABA_A antagonist bicuculline and the GABA_C antagonist (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid. This suggests that it largely reflects feedback from GABAergic amacrine cells. The response latency of intact rod bipolar cells was shorter than that of the axotomized cells, and the sensitivity curve covered …