DISTINCT RECEPTORS MEDIATE GASTRIN-RELEASING PEPTIDE AND NEUROMEDIN B-INDUCED DELAY OF GASTRIC-EMPTYING OF LIQUIDS IN RATS

The present study was carried out to define which bombesin receptors are involved in the delay of gastric emptying induced by bombesin-like peptides. Adult male rats were fitted with gastric and jugular vein cannulas. Gastric emptying was determined 5 min after a 3-ml intragastric load of 0.9 M NaCl using phenol red as a marker. Mammalian bombesin-like peptides gastrin-releasing peptide-10 and neuromedin B both induced a delay of gastric emptying. When [Phe(6)]bombesin-(6-13)-methyl ester, a selective antagonist of the gastrin-releasing peptide-preferring subtype of bombesin receptors, was injected 5 min before the agonists, the effect of gastrin-releasing peptide-10 was competitively inhibited, whereas that of neuromedin B remained unaffected. Our results indicate that gastrin-releasing peptide-10 and neuromedin B delay gastric emptying by acting on distinct receptors in rats, in vivo.