Dopaminergic Mechanisms in the Teleost Retina

Abstract

The ability of dopamine, dopamine agonists, other proposed retinal neurotransmitters, depolarizing agents, and light to stimulate adenylate cyclase activity in pieces of intact carp retina was examined. A dopamine-sensitive adenylate cyclase was the only neurotransmitter activated adenylate cyclase in the carp retina, i.e., only dopamine or agents that activate dopamine receptors, appear to stimulate cAMP synthesis in the retina. Depolarizing agents, e.g., K+ or veratridine, increase retinal cAMP levels, apparently by releasing endogenous stores of dopamine. The increase of retinal cAMP levels induced by 45 mM-K+ was blocked by 5 mM-Co2+ or 100 .mu.M-haloperidol, a dopamine antagonist. Flashing lights slightly increased cyclic AMP levels in the retina. Haloperidol abolished this effect.