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Abstract
We recorded light-evoked lateral inhibitory postsynaptic currents (L-IPSCs) from ON-type mixed rod/cone bipolar cell terminals in goldfish retina to characterize their timing, mechanisms, and plasticity. L-IPSCs showed ON (∼50 ms) and OFF (100–150 ms) components mediated by GABA_A/GABA_C receptors and AMPA/NMDA signaling. ON inputs combined rod and cone signals; OFF inputs were cone-driven and relied on spiking amacrine cells. Paired-flash protocols revealed short-term depression for ON and depression-to-facilitation for OFF responses. Ascorbic acid enhanced GABAergic currents, suggesting a modulatory role in plasticity. These findings reveal distinct, dynamic inhibitory pathways regulating glutamate release at bipolar terminals.