Inhibition of gastric and pancreatic secretions by cerebroventricular injections of gastrin-releasing peptide and bombesin in rats.

It has been suggested that mammalian gastrin-releasing peptide (GRP) and bombesin (BBS) might inhibit gastric secretion by a central nervous system action. The present investigations were intended to define the gastric effect and to look for an effect on the exocrine pancreas. Wistar male rats were provided with a chronic cannula allowing cerebroventricular injections in the 3rd ventricle, and with chronic gastric and/or pancreatic fistulas allowing the collection of gastric and/or pancreatic secretions in conscious animals. Both basal secretions were studied. Gastric secretion was stimulated with a 75 mg/kg s.c. injection of 2-deoxyglucose (2-dGlc). The dose range of bombesin was 0.01-1 microgram (6-600 pmol) and GRP was 0.01-10 microgram/rat (3.5 pmol to 3.5 nmol). A significant dose related decrease of basal gastric secretion was observed with the two peptides. The gastric acid response to 2-dGlc was inhibited by both peptides in a dose-related fashion and the reduction of gastric acid output mainly resulted from a decrease in the volume of gastric juice. The exocrine pancreatic secretion was also decreased by 30-55% after GRP but the BBS inhibitory effect was poorly dose-related. No significant difference was found after removal of gastric secretion, indicating that most of the pancreatic inhibition was independent of gastric secretion.