title: Intragastric monosodium L-glutamate stimulates motility of upper gut via vagus nerve in conscious dogs.
abstract: Monosodium l-glutamate (MSG) is a substance known to produce the umami taste. Recent studies indicate that MSG also stimulates a variety of activities in the gastrointestinal tract through its receptor in the gut, but no study has reported the activity in conscious large experimental animals. The aim of our study was to investigate whether direct intragastric MSG stimulates gut motility and to identify the mechanism in conscious dogs. Contractile response to intraluminal injection of MSG was studied in the fed and fasted states by means of chronically implanted force transducers. MSG (5, 15, 45, and 90 mM/kg) dissolved in water was injected into the stomach and duodenum in normal and vagotomized dogs. MSG solution was administered into the stomach before feeding, and gastric emptying was evaluated. Several inhibitors of gastrointestinal motility (atropine, hexamethonium, and granisetron) were injected intravenously before MSG administration to the stomach. The effect of MSG was investigated in Pavlov (vagally innervated corpus pouch), Heidenhain (vagally denervated corpus pouch), and antral pouch (vagally innervated) dogs. Upper gut motility was significantly increased by intragastric MSG but not significantly stimulated by intraduodenal MSG. Intragastric MSG (45 mM/kg) stimulated postprandial motility and accelerated gastric emptying. MSG-induced contractions were inhibited by truncal vagotomy, atropine, hexamethonium, and granisetron. Gut motility was increased by intrapouch injection of MSG in the Pavlov pouch, but it was not affected in the Heidenhain or antral pouch dogs. We conclude that intragastric MSG stimulates upper gut motility and accelerates gastric emptying. The sensory structure of MSG is present in the gastric corpus, and the signal is mediated by the vagus nerve.
authors.affiliation: Department of General Surgical Science, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan. toyomasu@med.gunma-u.ac.jp
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Toyomasu
authors.forename: Erito
authors.initials: E
authors.lastname: Mochiki
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Yanai
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Ogata
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Tabe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ando
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Ohno
authors.forename: Ryuusuke
authors.initials: R
authors.lastname: Aihara
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Zai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kuwano
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004285:Dogs; D005746:Gastric Emptying / Q000187:drug effects*; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D007275:Injections, Intravenous; D009119:Muscle Contraction / Q000187:drug effects; D012016:Reference Values; D012701:Serotonin / Q000097:blood; D012970:Sodium Glutamate / Q000008:administration & dosage / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*
chemical_list: D012701:Serotonin; D001285:Atropine; D012970:Sodium Glutamate