D1-dopamine receptor activation mediates [3H]acetylcholine release from rabbit retina.

Dopamine and dopamine receptor agonists (0.1 microM-10 mM) evoked in a concentration-dependent manner, calcium-dependent release of [3H]acetylcholine from the rabbit retina labeled in vitro with [3H]choline. This stimulatory effect of dopamine was antagonized by SCH23390 and by alpha-flupenthixol, but not by S-sulpiride or propranolol. Increases in intracellular cyclic AMP by forskolin, 3-isobutyl-1-methylxanthine and 8-bromo-cyclic AMP also evoked calcium-dependent release of [3H]acetylcholine. These results indicate that activation of a receptor with the biochemical and pharmacological characteristics of a D1-dopamine receptor mediates calcium-dependent release of acetylcholine from rabbit retina, possibly through a cyclic AMP-dependent process.