Dopaminergic modulation of horizontal-cell-axon-terminal receptive field size in the mammalian retina.

Receptive fields of gap junction-coupled axon terminals of B-type horizontal cells of isolated rabbit retinae were measured by recording light responses to slit shaped light stimuli at different eccentricities from the recording site. The D1/D5 agonist SKF-38393 and the membrane permeant second messenger 8-bromo-cAMP caused decreases of space constants by 20% while the D1/D5 antagonist SCH-23390 increased space constants by 25%. The results of this study indicate that axon terminal receptive fields of the rabbit retina can be modulated by D1/D5 receptor activation based on a cAMP-mediated mechanism. The data also suggest the presence of endogenous dopamine as an agent for axon terminal receptive field size modulation.