EVIDENCE FOR D(2) RECEPTOR REGULATION OF DOPAMINE RELEASE IN THE GOLDFISH RETINA

The possible existence of a dopamine D2 receptor-mediated regulation o f dopamine release was investigated in the goldfish retina. Isolated r etinas were preloaded with [H-3]dopamine and superfused with D2 dopami ne receptor agonists or antagonists to determine if there was an effec t on [H-3]dopamine release. The D2 receptor antagonist sulpiride incre ased both baseline [H-3]-dopamine release and [H-3]dopamine release in duced by an increase in extracellular potassium concentration. The D2 receptor agonists LY-171555 and RU-24213 did not reduce baseline [H-3] dopamine release but completely inhibited [H-3]dopamine release induce d by an increase in [K+]o. This action of the D2 agonists was blocked by sulpiride. These studies demonstrate the existence of D2 receptor, possibly autoreceptor, regulation of dopamine release in the teleost r etina.