ContextGlucagon-like peptide-1 (GLP-1) secretion from L-cells and postprandial inhibition of gastrointestinal motility.ObjectiveInvestigate whether physiological plasma concentrations of GLP-1 can inhibit human postprandial gastrointestinal motility; determine target mechanism of GLP-1 and analogue ROSE-010 action.DesignSingle-blind parallel study.SettingUniversity research laboratory.ParticipantsHealthy volunteers investigated with antroduodenojejunal manometry. Human gastric, intestinal and colonic muscle strips.InterventionsMotility indices (MI) obtained before and during infusion of saline or GLP-1 were compared. Plasma GLP-1 and glucagon-like peptide-2 (GLP-2) measured by radioimmunoassay. Gastrointestinal muscle strips, pre-contracted with bethanechol/electric field stimulation (EFS), investigated for GLP-1- or ROSE-010-induced relaxation. GLP-1, GLP-2 and their receptors localized by immunohistochemistry. Action mechanisms studied employing exendin(9-39)amide, Lω-nitro-monomethylarginine (L-NMMA), 2´,5´-dideoxyadenosine (DDA), tetrodotoxin (TTX).Main outcome measuresHypothesize postprandial gastric relaxation induced by GLP-1, the mechanism of which intrinsic neuronally-mediated.ResultsFood intake increased MI to 6.4±0.3 (antrum), 5.7±0.4 (duodenum) and 5.9±0.2 (jejunum). GLP-1 administered intravenously raised plasma GLP-1, but not GLP-2. GLP-1 0.7 pmol/kg·min significantly suppressed MI to 4.6±0.2, 4.7±0.4 and 5.0±0.2, respectively, while 1.2 pmol/kg·min suppressed corresponding MI to 5.4±0.2, 4.4±0.3 and 5.4±0.3 (p<0.0001-0.005). GLP-1 and ROSE-010 prevented bethanechol- or EFS-induced muscle contractions (p <0.005-0.05). Inhibitory responses to GLP-1 and ROSE-10 were blocked by exendin(9-39)amide, L-NMMA, DDA or TTX (all p <0.005-0.05). GLP-1 and GLP-2 were localized to epithelial cells; GLP-1 also in myenteric neurons. GLP-1R and GLP-2R were localized at myenteric neurons but not muscle, GLP-1R also in epithelial cells.ConclusionsGLP-1 inhibits postprandial motility through GLP-1R at myenteric neurons, involving nitrergic and cAMP-dependent mechanisms.