Peptides, Vol. 10, pp. 281-287. ©Pergamon Press plc, 1989. Printed in the U.S.A. 0196-9781/89 $3.00 + .00 Dual Effect of Bombesin and Gastrin Releasing Peptide on Gastric Emptying in Conscious Cats ABDUL RAZAK CHIKH-ISSA, CARMELO SCARPIGNATO, MARTINE COLLINET, JEAN-ALAIN CHAYVIALLE AND MONIQUE VAGNE 1 INSERM U 45, Lyon, France Institute of Pharmacology, University of Parma, Italy Received 18 August 1988 CHIKH-ISSA, A. R., C. SCARPIGNATO, M. COLLINET, J.-A. CHAYVIALLE AND M. VAGNE. Dual effect ofbombesin and gastrin releasingpeptide on gastric emptying in conscious cats. PEPTIDES 10(2) 281-287, 1989. -- The effect of bombesin (BBS) and gastrin releasing peptide (GRP) on gastric emptying was studied in conscious cats. This effect was measured simultaneously with antral motility. Acid and pepsin secretions as well as blood hormonal peptide release were additionally measured. A dual effect was observed. First, BBS and GRP slowed gastric emptying of liquids, while antral motility was decreased, then after 60 minutes of continuous intravenous infusion, antral motility returned to basal values and gastric emptying effect reversed. The mechanism of this peculiar action is independent of gastrin, pancreatic polypeptide, somatostatin and motilin release and most probably connected with a cholinergic stimulation induced by the peptides, the late predominance of which counterbalances the inhibitory effect of bombesin-like peptides on antral motility. Bombesin Gastrin releasing peptide Gastric emptying Cats Antral motility SINCE the isolation of the porcine gastrin releasing peptide (GRP) by McDonald et al. (13), several studies have compared the effect of GRP to that of the structurally related peptide, bombesin (BBS), isolated from frog skin (4). The amphibian decapeptide was shown to strongly delay gastric emptying in rats (16) and humans as well (17,27). This inhibitory effect seems to be connected with the marked contracting action of BBS on gastroduodenal region (16), the dependence on gastrin release being still questionable (15, 17, 27). Previous studies from other (14) and our laboratories (26) have shown that BBS and GRP possess the same spectrum of biological actions although some qualitative differences were reported (6,8). In conscious cats, we have shown that not only the potency but also the efficacy of GRP can be lower than those of BBS, depending on the biological response involved (26). In this study, we wanted to check whether BBS is able to affect gastric emptying also in cats and if this effect is shared by GRP. Antral motility is affected by BBS and GRP in cats: an increase of low amplitude and a decrease of high amplitude contractions was observed during the first 30 minutes of peptide administration (25,26). However, this effect, which is comparable to that of gastrin and cholecystokinin in the cat (2), disappeared progres- sively with time despite continuing the administration of both BBS and GRP (26). Since the effect on gastric emptying can be regarded as the results of the action(s) on the different regions of the stomach (7, 9, 12), we compared the effect of either BBS and GRP on gastric emptying and antral motility in order to correlate both parameters. Acid and pepsin secretion as well as gastrin, pancreatic polypeptide, somatostatin and motilin release induced by BBS and GRP were additionally studied. METHOD Animals Seven cats, 4 males and 3 females, weighing 3.3 to 3.8 kg, were used. Under pentobarbital anesthesia (Nembutal, Abbott, 25 mg.kg-~), they were surgically equipped with both gastric and duodenal cannulae (26). Experiments started 3 weeks or more after surgery. The conscious animals were fasted 18 hours before each test. Tests were not repeated more than twice a week. Experimental Design A continuous intravenous infusion of saline was administered at a rate of 12 ml per hour by means of a catheter placed in a leg vein of the animals and connected to a peristaltic pump (Harvard). ~Requests for reprints should be addressed to Dr. M. Vagne, INSERM U 45, Pavilion H bis, Hrpital E Herriot, 69437 Lyon cedex 3, France. 281