title: Underlying mechanism of the cyclic migrating motor complex in Suncus murinus: a change in gastrointestinal pH is the key regulator.
abstract: In the fasted gastrointestinal (GI) tract, a characteristic cyclical rhythmic migrating motor complex (MMC) occurs in an ultradian rhythm, at 90-120 min time intervals, in many species. However, the underlying mechanism directing this ultradian rhythmic MMC pattern is yet to be completely elucidated. Therefore, this study aimed to identify the possible causes or factors that involve in the occurrence of the fasting gastric contractions by using Suncus murinus a small model animal featuring almost the same rhythmic MMC as that found in humans and dogs. We observed that either intraduodenal infusion of saline at pH 8 evoked the strong gastric contraction or continuously lowering duodenal pH to 3-evoked gastric phase II-like and phase III-like contractions, and both strong contractions were essentially abolished by the intravenous administration of MA 2029 (motilin receptor antagonist) and D-Lys3-GHRP6 (ghrelin receptor antagonist) in a vagus-independent manner. Moreover, we observed that the prostaglandin E2-alpha (PGE2-α) and serotonin type 4 (5HT4) receptors play important roles as intermediate molecules in changes in GI pH and motilin release. These results suggest a clear insight mechanism that change in the duodenal pH to alkaline condition is an essential factor for stimulating the endogenous release of motilin and governs the fasting MMC in a vagus-independent manner. Finally, we believe that the changes in duodenal pH triggered by flowing gastric acid and the release of duodenal bicarbonate through the involvement of PGE2-α and 5HT4 receptor are the key events in the occurrence of the MMC.
authors.affiliation: Department of Life Nano-Bio, Strategic Research Division, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Anupom
authors.initials: A
authors.lastname: Mondal
authors.affiliation: Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Koyama
authors.affiliation: Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mikami
authors.affiliation: Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Taichi
authors.initials: T
authors.lastname: Horita
authors.affiliation: Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Takemi
authors.affiliation: Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tsuda
authors.affiliation: Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sakata
authors.affiliation: Department of Life Nano-Bio, Strategic Research Division, Graduate School of Science and Engineering, Saitama University, Saitama, Japan tsakai@mail.saitama-u.ac.jp.|Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sakai
mesh_terms: D000081:Acetamides / Q000008:administration & dosage / Q000494:pharmacology; D061605:Administration, Intravenous; D000818:Animals; D015232:Dinoprostone / Q000378:metabolism; D004386:Duodenum / Q000737:chemistry / Q000502:physiology; D005215:Fasting / Q000502:physiology; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology; D006863:Hydrogen-Ion Concentration / Q000187:drug effects*; D007097:Imines / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D009037:Motilin / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D016065:Myoelectric Complex, Migrating / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D011964:Receptors, Gastrointestinal Hormone / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D018013:Receptors, Neuropeptide / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D012788:Shrews; D013270:Stomach / Q000737:chemistry* / Q000502:physiology; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D000081:Acetamides; D007097:Imines; C414084:MA 20565; D009842:Oligopeptides; D011964:Receptors, Gastrointestinal Hormone; D018013:Receptors, Neuropeptide; C050802:motilin receptor; C041048:growth hormone releasing hexapeptide; D009037:Motilin; D015232:Dinoprostone
keywords: 
  MMC
  ; Gastrointestinal pH; motilin