Dopamine produced by the stomach may act as a paracrine/autocrine hormone in the rat

Dopamine (DA) has been suggested to be a protective factor in the gastrointestinal tract but neither a source of DA nor its exact targets of action have been identified. In this study, we demonstrate high levels of DA (and DOPA) which persist after chemical sympathectomy in the gastric juice of rats. Immunostaining and in situ hybridization histochemistry reveal the presence of tyrosine hydroxylase (TH), DA transporter and vesicular monamine transporters in the acid-producing parietal cells. Like DA, TH enzyme activity remains after chemical sympathectomy. We also demonstrate active reuptake and storage of DA that indicates a regulated release of this neurohormone from parietal cells. DA D1b receptor mRNA is the most abundant DA receptor subtype in gastric and duodenal epithelium. Therefore, we suggest that selective DA D1b receptor agonists may be useful adjuncts in the treatment of duodenal and gastric ulcers. Gastric epithelia possess the hallmarks of functional DA neuroendocrine cells, suggesting that DA has an important role in self-protective mechanisms of the gastrointestinal tract. These findings should allow elucidation of DA role in normal and disease states in the stomach and duodenum.