Mechanism of interdigestive migrating motor complex in conscious dogs.
BACKGROUND
The migrating motor complex (MMC) is well characterized by the appearance of gastrointestinal contractions in the interdigestive state. This study was designed to clarify the mechanisms of gastric MMC (G-MMC) and intestinal MMC (I-MMC) in conscious dogs.


METHODS
Five strain gauge transducers were implanted on the stomach and intestine. To investigate the correlation between luminal 5-HT and phase III contractions, gastric and duodenal juices were collected during the MMC cycle. The 5-HT concentrations in gastric and duodenal juice were measured by HPLC. To investigate whether luminal 5-HT initiates MMC, 5-HT (10(-8)-10(-6) M, 10 ml) was administered into the duodenum 20 min after gastric phase III. To investigate the involvement of 5-HT(3) or 5-HT(4) receptors in mediating G-MMC and I-MMC, 5-HT(3) antagonists (ondansetron) or 5-HT(4) antagonists (GR 125,487) were infused for 120 min.


RESULTS
Luminal administration of 5-HT (10(-6) M) initiated duodenal phase II followed by G-MMC and I-MMC with a concomitant increased release of plasma motilin. The duodenal 5-HT concentration was significantly increased during phase II (59 +/- 9 ng/ml) and phase III (251 +/- 21 ng/ml) compared to that of phase I (29 +/- 5 ng/ml). On the other hand, the 5-HT content in the stomach was not significantly changed throughout the MMC cycle. Intravenous infusion of motilin (0.3 microg/kg/h) increased the luminal 5-HT content and induced G-MMC and I-MMC. 5-HT(4) antagonists significantly inhibited both G-MMC and I-MMC, while 5-HT(3) antagonists inhibited only G-MMC.


CONCLUSIONS
It is suggested that the MMC cycle is mediated by a positive feedback mechanism via the interaction between motilin and 5-HT.
Nakajima
Hitoshi
H
Department of Surgery, Duke University Medical Center, Durham, NC, USA.
Mochiki
Erito
E
Zietlow
Aaron
A
Ludwig
Kirk
K
Takahashi
Toku
T
D000818:Animals; D003243:Consciousness / Q000502:physiology; D004285:Dogs; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D005765:Gastrointestinal Agents / Q000494:pharmacology; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D009037:Motilin / Q000494:pharmacology / Q000502:physiology*; D009092:Mucous Membrane / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D016065:Myoelectric Complex, Migrating / Q000187:drug effects / Q000502:physiology*; D011706:Pyloric Antrum / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D018490:Serotonin Agents / Q000494:pharmacology; D014160:Transducers, Pressure
D005765:Gastrointestinal Agents; D018490:Serotonin Agents; D012701:Serotonin; D009037:Motilin