The stomach and/or upper duodenum contain sites of action that control meal size and intermeal interval length by exogenous rat gastrin releasing peptide

Abstract

The site(s) of action that control the reduction of food intake in response to the amphibian skin peptide bombesin (Bn) has been determined to be the area supplied by the celiac artery (CA), i.e., the stomach and the upper duodenum. Here, we investigated the gastrointestinal site(s) of action which controls meal size (MS) (normal rat chow) and intermeal interval length (IMI) by the mammalian homologues of Bn gastrin releasing peptides (GRP-10, GRP-27 and GRP-29, 0.01, 0.05, 0.1, 0.2 and 0.5nmol/kg) infused in the CA, the cranial mesenteric artery (CMA, supplying the small and large intestine), the femoral artery (FA, control) and the portal vein (PV, draining the gastrointestinal tract, control) in freely fed rats immediately prior to the onset of the dark cycle. We found that (1) GRP-29 (0.05, 0.1, 0.2 and 0.5nmol/kg) and GRP-27 (0.2 and 0.5nmol/kg) in the CA and GRP-29 (0.5nmol/kg) in the CMA reduced the MS relative to saline, (2) GRP-29 (0.1, 0.2 and 0.5nmol/kg) and GRP-27 (0.2 and 0.5nmol/kg) in the CA prolonged the IMI, (3) GRP-29 (0.1, 0.2 and 0.5nmol/kg) in the CA and GRP-29 (0.5nmol/kg) in the CMA increased the satiety ratio (SR, IMI/MS – the amount of food consumed per a given unit of time) and (4) neither peptide nor route showed any effect on the second MS. These results support an upper gastrointestinal site of action for MS and IMI length by GRP-27 and GRP-29, which is most likely the stomach and/or the duodenum.