Activation of a D2 receptor increases electrical coupling between retinal horizontal cells by inhibiting dopamine release.

Oct 1, 1992Proceedings of the National Academy of Sciences of the United States of America

Activating D2 receptors strengthens electrical links between retinal cells by reducing dopamine release

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Abstract

Superfusion of the D2 agonist LY171555 increased horizontal cell coupling by an average of 31% in the intact goldfish retina.

Dopamine activates D1 receptors, decreasing electrical coupling between horizontal cells.
LY171555, a D2 receptor agonist, enhanced horizontal cell coupling while reducing responses to light stimuli.
Coupling effects from LY171555 were completely blocked by prior activation of D1 receptors.
Destruction of dopaminergic neurons eliminated the coupling effect of LY171555 but not the uncoupling effect of D1 receptor activation.

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In the fish retina, interplexiform cells release dopamine onto cone-driven horizontal cells. Dopamine decreases the electrical coupling between horizontal cells by activating adenylate cyclase through dopamine D1 receptors. Using intracellular recording, we have studied the effect of dopamine D2 receptor activation on horizontal cell electrical coupling in the intact goldfish retina. Superfusion of the D2 agonist LY171555 (quinpirole; 0.2-10 microM) increased horizontal cell coupling, as indicated by a decrease in responses to centered spots or slits of light. The length constant of the horizontal cell network increased an average of 31%. Although dopamine (0.5-20 microM) uncoupled horizontal cells, lower concentrations (e.g., 0.2 microM) initially uncoupled and then subsequently increased coupling beyond initial control levels. The coupling effect of LY171555 (10 microM) was blocked completely by prior application of the D1 agonist SKF 38393 at saturating (20 microM) or nonsaturating (2.5-5.0 microM) doses. Prior treatment of the retinas with 6-hydroxydopamine, which destroyed dopaminergic neurons, eliminated the coupling effect of LY171555 but not the uncoupling effect of SKF 38393. These results suggest that goldfish horizontal cells contain D1, but not D2, receptors and that dopamine activation of D2 autoreceptors on interplexiform cells inhibits dopamine release onto horizontal cells so that the electrical coupling between horizontal cells increases.

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Activation of a D2 receptor increases electrical coupling between retinal horizontal cells by inhibiting dopamine release.

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