Analyses of neural mechanisms mediating the effect of horizontal cell polarization.

Polarization of horizontal cells by current through an intracellular electrode elicited a response in certain other horizontal cells and in bipolar cells. Results were consistent with the hypothesis that the feedback from horizontal cells to photoreceptors play an important role in the center-surround antagonism of bipolar cells and also in the opponent color responses of horizontal cells. The feedback from L-type horizontal cells must be mediated by GABA. The red component of RG-type and RGB-type horizontal cells was suppressed by application of GABA antagonists. GABA receptors was not found in these cells, suggesting that the effect was mediated through photoreceptors.