Effects of background illuminations on the receptive field size of horizontal cells in the turtle retina are mediated by dopamine.

Intracellular recordings from luminosity-type horizontal cells of the turtle retina were used to analyze the effects of steady and flickering background illumination on the size of their receptive fields. Both types of background illumination reduce the size of the receptive field to about the same extent. The reduction seems largely due an increase in the coupling resistance between horizontal cells. The effects of both types of background illumination are sensitive to the dopamine antagonist fluphenazine. This suggests that steady and flickering illuminations stimulate the release of endogenous dopamine.