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 gast rointestinal tract but neither a source of DA nor its exact targets of action have been identified. In this study, we demonstrate high level s of DA (and DOPA) which persist after chemical sympathectomy in the g astric juice of rats. Immunostaining and in situ hybridization histoch emistry reveal the presence of tyrosine hydroxylase (TH), DA transport er and vesicular monamine transporters in the acid-producing parietal cells. Like DA, TH enzyme activity remains after chemical sympathectom y. We also demonstrate active reuptake and storage of DA that indicate s a regulated release of this neurohormone from parietal cells. DA Dib receptor mRNA is the most abundant DA receptor subtype in gastric and duodenal epithelium. Therefore, we suggest that selective DA Dib rece ptor 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 s elf-protective mechanisms of the gastrointestinal tract. These finding s should allow elucidation of DA role in normal and disease states in the stomach and duodenum.