Neuronostatin: peripheral site of action in mouse stomach

Neuronostatin is a 13-amino acid peptide encoded by somatostatin gene. It is distributed in different organs including gastrointestinal tract and has been involved in the control of food intake and gastrointestinal motility, likely through an action in the brain. So far, there are no reports about the occurrence of peripheral action sites in the gut. Therefore, the purpose of the present study was to examine, in the mouse, the effects of peripheral administration of neuronostatin on food intake within 24h and on gastrointestinal motility and to analyse neuronostatin actions on the gastric and intestinal mechanical activity in isolated preparations in vitro. When compared with PBS-treated mice, intraperitoneal neuronostatin reduced food intake in doses ranging from 1 to 15ng/g b.w. only in the first hour postinjection with a maximum effect obtained at the dose of 15ng/g b.w. (-46.9%). The peptide (15ng/g b.w.) significantly reduced gastric emptying rate (-31.1%) and gastrointestinal intestinal transit. Non-amidated neuronostatin failed to affect food intake, gastric emptying and intestinal transit, suggesting the specificity of action. In vitro, neuronostatin induced concentration-dependent gastric relaxation, which was abolished by tetrodotoxin. Neuronostatin failed to affect the spontaneous mechanical activity or the evoked cholinergic contractions in duodenum. These results suggest that exogenous neuronostatin is able to reduce mouse gastric motility by acting peripherally in the stomach, through intramural nervous plexuses. This indirectly action could cause reduction of food intake in the short term.