Responsiveness and receptive field size of carp horizontal cells are reduced by prolonged darkness and dopamine.

In the fish retina the interplexiform cells contain dopamine and provide a centrifugal pathway from the inner plexiform layer to horizontal cells of the outer plexiform layer. Dopamine application reduced the responsiveness and receptive field size of cone horizontal cells, as did a prolonged period of complete darkness. Other results suggest that the interplexiform cells may release dopamine after a prolonged period in the dark. The interplexiform-horizontal cell system may modify the strength of the antagonistic surrounds of retinal neurons as a function of time in the dark.