The role of L‐type horizontal cells in the opponent‐color process

It has been suggested that the interaction among horizontal cells, including a negative feedback to cones, plays an indispensable role in the transduction from a trichromatic to an opponent‐color process. To test this hypothesis, L‐and RG‐type horizontal cells were recorded simultaneously in the carp retina and the effect of polarization by current of L‐type cells on RG‐type cells was studied. In some pairs, hyperpolarization of an L‐type cell elicited a depolarizing response in an RG‐type cell. The effect of polarization of L‐type cells was also observed in some cones. Depolarizing responses of RG cells were thus shown to be mediated by L‐type cells, possibly through a feedback pathway to cones. The same type of interaction was also observed between RG‐ and RGB‐type cells.