Evidence for D2 Receptor Regulation of Dopamine Release in the Goldfish Retina

The possible existence of a dopamine D2 receptor-mediated regulation of dopamine release was investigated in the goldfish retina. Isolated retinas were preloaded with [3H]dopamine and superfused with D2 dopamine receptor agonists or antagonists to determine if there was an effect on [3H]dopamine release. The D2 receptor antagonist sulpiride increased both baseline [3H]-dopamine release and [3H]dopamine release induced by an increase in extracellular potassium concentration. The D2 receptor agonists LY-171555 and RU-24213 did not reduce baseline [3H]dopamine release but completely inhibited [3H]dopamine release induced 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 retina.