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PubMed1991

The migrating myoelectric complex of the small intestine.

Gastric and small intestinal myoelectric and motor activity is divided into two main patterns, fed and fasted. During fasting, the predominant pattern of activity is the migrating myoelectric complex (MMC), a cyclically occurring pattern of electric and mechanical activity that is initiated in the stomach and duodenum almost simultaneously and, from there, propagates the length of the small intestine. Cyclic motor activity also occurs in the lower esophageal sphincter, the gallbladder, and the sphincter of Oddi with a duration that is related to the MMC in the small intestine. Of the possible mechanisms for initiation of the MMC in the small intestine (extrinsic neural control, intrinsic neural control, and hormonal control), intrinsic neural control via a series of coupled is the most likely. The keep this sentence in! hormone motilin also plays a role in the initiation of MMCs. After a meal, in man the MMC is disrupted and replaced by irregular contractions. The physiologic role of the MMC is to clear the stomach and small intestine of residual food, secretions, and desquamated cells and propel them to the colon. Disruption of the MMC cycle is associated with bacterial overgrowth in some patients, an observation that supports the proposed cleansing function of the MMC cycle.

Journal Article↗
PubMed1984

Initiation of migrating myoelectric complex in sheep by duodenal acidification and hyperosmolarity: role of vagus nerves.

Gastrointestinal motility was studied in conscious sheep by X-radiography and by electromyography from chronically implanted electrodes before and after total thoracic vagotomy. Duodenal infusion of 0.5-3 mmol HCl (0.035-0.1 M-HCl) induced premature duodenal regular spiking activity (r.s.a.) within 1-7 min in fifteen of seventeen sheep studied when infused at 20 min after a natural r.s.a. There was no correlation between abomasal pH and any phase of the migrating myoelectric complex (m.m.c.). Duodenal alkalinization by infusion of 0.3 M-Tris buffer (pH 10.2) or 0.1 M-NaHCO3 had no influence on the occurrence of the m.m.c. Duodenal infusion of 20-50 ml 0.5 M-NaCl induced a premature duodenal r.s.a. within 1-5 min in seven of eight sheep. Vagotomy did not prevent the initiation or migration of the m.m.c., but reduced the rate of propagation of the r.s.a. from 40.5 +/- 7.2 (mean +/- S.E. of mean) to 16.7 +/- 0.1 cm/min in the duodenum, from 27.3 +/- 4.1 to 16.6 +/- 0.8 cm/min in the jejunum, and from 21.4 +/- 1.1 to 13.7 +/- 0.7 cm/min in the proximal ileum. Initially the frequency of r.s.a. increased, especially in the duodenum where they recurred at an interval of 98.4 +/- 6.8 min before vagotomy; and at 23.4 +/- 1.8 min in the first 24 h after vagotomy; the interval had lengthened to 86.7 +/- 5.2 min 2-3 weeks after vagotomy. Premature duodenal r.s.a. was not induced by duodenal infusion of HCl in five, or by duodenal infusion of hyperosmolar NaCl in three chronically vagotomized sheep. It is concluded that the vagus nerves contribute to the regulation of the frequency and propagation of the m.m.c. in sheep; duodenal acidification is not essential nor is it the normal stimulus for initiation of r.s.a., but duodenal infusion of HCl or hyperosmolar NaCl can initiate a premature duodenal r.s.a. via the vagus nerves.

Abomasum↗
PubMed1992

Travel stress alters the intestinal migrating myoelectric complex in rats: antagonist effect of trimebutine.

A novel stress model was developed that may closely resemble a real-life situation. Intestinal motility was monitored in rats before and after a 12 hour train voyage (travel stress). Travel stress reduced the duration of phase III of the intestinal MMC by 30% (3.2 +/- 0.3 vs 4.7 +/- 0.6 min; p less than 0.001) while the durations of phase I and II were unaffected. This effect persisted for two days. Phase III duration returned to basal values after 3 days indicating a reversible alteration on intestinal migrating myoelectric complex (MMC). The infusion of trimebutine at a flow rate of 166 micrograms/kg/h during the stress exposure abolished the changes observed in the duration of phase III of the MMC; the infusion of diazepam (16.6 micrograms/kg/h) had no effect. These results indicate that the travel stress model may be similar to common life events that induce alterations of intestinal motility. Furthermore, trimebutine prevented the reduction of phase III duration induced by travel stress suggesting its possible action on mechanisms involved in the mediation of the stress-induced intestinal motility changes.

Animals↗
PubMed1985

Origin and characterization of migrating myoelectric complex in rabbits.

Myoelectric activity patterns of the upper gastrointestinal tract were recorded using chronically implanted electrodes in conscious rabbits. A cyclical pattern of intense spiking activity occurring on almost every slow wave for 10-15 min, corresponding to the regular spiking phase or phase III of the migrating myoelectric complex (MMC), was recorded. This activity was detected by electrodes implanted distal to the ligament of Treitz on the proximal jejunum at a frequency of 9.4-10.6/24 hr. The MMC pattern occurred in both fed and fasted animals, regardless of the presence of cecotrophy. Initiation of phase III activity on the jejunum persisted after transplantation of the pancreatic duct opening to the proximal duodenum 5 cm from the pylorus and when gastric contents emptied directly into the proximal jejunum through a large gastrojejunostomy. It is concluded that the MMC pattern of the rabbit small intestine is persistently initiated in the proximal jejunum distal to the pancreatic and biliary ducts. The jejunal origin of the MMC in the rabbit is reminiscent of that seen transiently 8-10 hr after a meal in dogs during the change from fed to the fasted pattern of gastrointestinal motor activity.

Animals↗
PubMed1977

Origin of migrating myoelectric complex in sheep.

The electrical activity of the gastroduodenal junction was recorded in conscious sheep for 8 to 12 wk with chronically implanted electrodes. The flow of digesta was simultaneously recorded, and the duodenal bulb was isolated at the time of implantation. The mean slow-wave frequency of the antrum was 5.6 +/- 0.3/min with spike bursts randomly superimposed on about 60% of the slow waves. The activity of the duodenal bulb was characterized by an absence of slow-wave unpropagated spike bursts and by two types of propagated spike bursts. The first consisted of isolated bursts accompanied by a rapid movement of digesta through the entire duodenum and proximal jejunum. The second, an irregular series of 8-12 spike bursts was associated with total evacuation of the duodenal bulb, followed in turn by an inhibition of antral spiking activity and the development of a migrating myoelectric complex (MMC) in the distal duodenum. The results indicate that in sheep organization of the MMC is located at the duodenal level where the duodenal bulb has a reservoir function.

Animals↗
PubMed1981

Initiation of the migrating myoelectric complex in dogs.

1. Contractile and spike activity in the conscious dog were recorded from strain gauge force transducers and electrodes chronically implanted on the antrum, duodenum and jejunum. The pattern of activity was related to the time elapsed after feeding a daily meal, both in intact dogs and in dogs with antro-jejunal or oesophago-duodenal anastomoses. 2. From 8 to 10 h after feeding, transient reductions of the continuous antral spiking activity were recorded while phases of regular spiking activity (RSA) and contractions developed on the proximal intestine. 3. About 18 h after feeding, the post-prandial antral activity became intermittent, each period of contractions being accompanied by the duodenal development of a RSA phase. 4. The RSA phases were still initiated on the duodenum after an antro-jejunal anastomosis and after gastrectomy. 5. It is concluded that phases of RSA of the migrating myoelectric complex are initiated in the proximal part of the small intestine rather than in the stomach. It is suggested that the RSA phase exerts an inhibitory effect on the antrum which may serve to reduce the flow of digesta through the pylorus when the ability of the duodenum to receive chyme is restricted.

Action Potentials↗
PubMed1996

Involvement of somatostatin, bombesin and serotonin in the origin of the migrating myoelectric complex in sheep.

Antroduodenal myoelectric activity was recorded in conscious sheep by electrodes chronically implanted in the muscular wall. Furthermore, plasma immunoreactive (i.r.) motilin, somatostatin and bombesin concentrations were determined by RIA. The intravenous infusion of somatostatin (20 ng/kg/min), bombesin (10 ng/kg/min) or serotonin (5-HT, 4 micrograms/kg/min) for 5 min, induced a duodenal myoelectric activity front followed by a period of quiescence. These duodenal events were concomitant with an antral inhibition. This pattern resembled that observed in a spontaneous migrating myoelectric complex (MMC) in sheep. Bombesin and 5-HT evoked an additional and transient increase in antral activity simultaneously with the duodenal activity front. On the other hand, plasma i.r. motilin levels did not show any fluctuations during spontaneous MMC cycles or after somatostatin, bombesin or 5-HT infusions. Likewise, plasma i.r. bombesin levels remained unchanged during spontaneous MMC or after administration of somatostatin. However, 5-HT -induced duodenal activity fronts were closely associated with a sharp peak in plasma i.r. bombesin. Finally, plasma i.r. somatostatin concentrations rose at the end of spontaneous phase III and peaked in phase I. A similar pattern of somatostatin release in plasma was found while the duodenal activity front and quiescence period developed after either 5-HT or bombesin infusions. These results do not indicate a role for motilin in the control of MMCs in sheep, although a definitive conclusion cannot be drawn until synthetic sheep motilin is available. However, our data suggest that somatostatin and bombesin-like peptides as well as 5-HT, acting in a coordinated manner, could be involved in the regulation of cyclical antroduodenal motor events in sheep.

Animals↗
PubMed1983

Electrical patterns in the human jejunum with and without vagotomy: migrating myoelectrical complexes and the influence of morphine.

Postprandial symptoms that occur in some patients following operation for duodenal ulcer are generally attributed to disruption of normal controlled gastric emptying resulting from vagotomy, enterostomy, or pyloroplasty. The notion that disturbances of small bowel motility could be caused by vagotomy and contribute to these symptoms led the author to examine the myoelectrical patterns of the small intestine in duodenal ulcer patients undergoing elective surgery for control of symptoms. These patients underwent either partial interruption of their vagus nerves by proximal gastric vagotomy (PGV) or complete section by truncal vagotomy (TV). Their records were compared with those of an equal number of control subjects with intact vagus nerves undergoing laparotomy for either gallstones or colonic cancer. Postoperative recordings were obtained without sedation via electrodes implanted at laparotomy and led out of the abdomen through a drain in the right upper quadrant. Observations were made on days 6 through 9 after reestablishment of normal gastrointestinal function. Three patterns of electrical activity were recorded--electrical control activity, electrical response activity, and migrating myoelectrical complexes (MMCs). No observable differences were seen among PGV, TV, and control procedure during fasting or fed conditions. A key to an understanding of the origin of the MMCs was provided by the finding of disruption of the normal cycling of the complex by a premature cycle whenever morphine was given. Release of acetylcholine in the myenteric plexus of the intestine by an intrinsic opioid agonist may be the initiating event of the intrinsic MMC. Exogenous morphine may have caused a premature MMC by mimicking the stimulus produced by endogenous opioid. The morphine response was similar in persons with or without vagus nerves, suggesting that the initiation of cycling of the complex is entirely under local control of the intestine and not exercised through the parasympathetic division of the autonomic nervous system.

Duodenal Ulcer↗
PubMed1990

The influence of the interdigestive migrating myoelectric complex on the gastric emptying of liquids.

It is unknown how the interdigestive migrating motor complex influences the gastric emptying of liquids. Therefore, the gastric emptying rate of 50- and 200-mL volumes of phenol red solution were measured while monitoring contractile activity. Motor activity was recorded using a hydraulic manometric system and expressed as either the proximity of dosing time to time of appearance of phase III or as a motility index, defined as (contractile area)/(sampling interval time). After an initial lag period, emptying was log linear. With a 50-mL oral dose, the mean gastric emptying rate of the log-linear phase was successively faster during phase I (0.018 +/- 0.003 min-1), phase II (0.083 +/- 0.031 min-1), and late phase II/III (0.171 +/- 0.066 min-1) (P less than 0.05). Similarly, the mean lag time decreased successively with phases I, II, and late II/III (19.1 +/- 12.4, 7.6 +/- 5.6, and 3.8 +/- 2.8 minutes, respectively). At a 200-mL oral dose, there was no difference in the emptying rate between phase I and phase II (0.104 +/- 0.0014 vs. 0.110 +/- 0.041 min-1), but the emptying rate during late phase II/III was significantly greater (0.236 +/- 0.069 min-1); lag time was not dependent on phase. There was a statistical difference in the overall mean emptying rate between the 50- and 200-mL volumes. Also, during phase I, the emptying rate was faster for the 200-mL volume. This study shows a strong dependence of liquid gastric emptying rate and lag time on interdigestive antral motility, the emptying of small volumes being more dependent on motility phase than that of large volumes. Phase-related fluctuations in contractile activity can account for much of the reported variability in gastric emptying data. Furthermore, this study suggests that dose volume and interdigestive motor activity at the time of drug administration can affect absorption and onset of therapeutic response for some drugs.

Analysis of Variance↗
PubMed2005

Effect of SC-435 on the gastrointestinal migrating myoelectric complex in guinea pigs.

OBJECTIVE: To determine whether SC-435, a new ileal apical sodium-codependent bile acid transporter (IBAT) inhibitor, can alter the gastrointestinal motility in guinea pigs. METHODS: Sixty guinea pigs received regular diet or IBAT inhibitor (SC-435) diet for 2, 4, and 8 weeks, respectively. At the end of the feeding period, the gallbladder motility was assessed and then four bipolar silver electrodes were implanted on the antrum, duodenum, jejunum, and ileum. Seven days later, migrating motor complex (MMC) was recorded and the total bile acid pool size was measured according to the isotope dilution principle in the meantime. RESULTS: After feeding SC435, the gallbladder motility was declined in the 4-week group and the 8-week group. The bile acid pool size decreased by 17.11% (P <0.05) in the 4-week group and 48.35% (P < 0.05) in the 8-week group. The places of origin of MMC were changed where antral origins (37%) and duodenal origins (46%) decreased whereas jejunal origins (17%) increased. The MMC cycle period was prolonged in the duodenum (1.16 times in the 4-week group, P < 0.05; 1.38 times in the 8-week group, P < 0.05) whereas MMC amplitude fell in the duodenum (10.58% in the 4-week group, P <0.05; 49.17% in the 8-week group, P <0.05). There were not significant differences in all parameters of MMC between the control group and the 2-week group in guinea pigs. CONCLUSION: The IBAT inhibitor (SC-435) reduces the bile acid pool size and inhibits the MMC cycle activity. MMC is related to the enterohepatic circulation of bile acids, which is consistent with the changes of the bile acid pool size in guinea pigs.

Animals↗
PubMed1981

Initiation of migrating myoelectric complexes in human subjects: role of duodenal acidification and plasma motilin.

The hypothesis that acid, emptied intermittently from the stomach during fasting, might initiate the duodenal phase of the migrating motor complex was tested in normal human subjects. In addition, the relationship between plasma motilin concentrations and the initiation of migrating motor complexes was examined. Migrating complexes occurred spontaneously in the absence of acid in the duodenal bulb and in the presence of duodenal bulb neutralization with sodium bicarbonate. Thus duodenal bulb acidification is not necessary for initiation of the duodenal phase of the migrating motor complexes. Furthermore, cyclical increases in plasma motilin concentrations were not closely correlated with the initiation of the gastric phase of maximal activity of the migrating motor complexes. However, motilin concentrations were decreased significantly following onset of the duodenal phase III. We conclude that neither duodenal acidification nor increases in motilin concentration are necessary to initiate migrating motor complexes in man.

Adult↗
PubMed1989

Postprandial disruption of migrating myoelectric complex in dogs. Hormonal versus extrinsic nervous factors.

Our aim was to determine the mechanism whereby the jejunoileum regulates postprandial gastroduodenal motility. Five dogs were prepared with a proximal jejunal infusion catheter and with gastric manometry catheters and serosal intestinal electrodes for recording gastric and intestinal motility. After two weeks, fasted dogs were studied during jejunal infusion of either isosmolar NaCl (154 mM) or isosmolar mixed nutrient solution (50% Meritene) on four separate days each. After completion of these baseline studies, the dogs underwent a model of autotransplantation of the entire jejunoileum (extrinsic denervation, disruption of intrinsic neural continuity with proximal duodenum). Two weeks later, identical studies as before were repeated with the now "autotransplanted" jejunoileum. Before transplantation, infusion of NaCl did not interrupt the characteristic interdigestive migrating motor complex either in the gastroduodenum or in the jejunoileum. However, infusion of nutrients interrupted the migrating motor complex both in the gastroduodenum and jejunoileum for the duration of the infusion (5 hr). After autotransplantation of the jejunoileum, the migrating motor complex continued to occur in the gastroduodenum and in the jejunoileum during infusion of NaCl, but the migrating motor complex cycled independently in each region without any temporal coordination. Jejunal infusion of nutrients interrupted the MMC in both regions for the duration of infusion (5 hr). Because inhibition of the gastroduodenal and jejunoileal migrating motor complex continued to occur during infusion of nutrients into the transplanted jejunum, we concluded that jejunoileal regulation of postprandial inhibition of interdigestive motility in the stomach and duodenum is mediated by hormonal factors and does not require intrinsic neural continuity.

Animals↗
PubMed1990

[Interrelations between the presence or lack of bile and bile acids in the small-intestinal lumen, release of motilin and pancreatic polypeptide and migrating myoelectric complex in dogs].

5 male and 1 female dogs weighing 15-20 kg were used in the study. Animals underwent the functional cholecystectomy, bidirectional cannulation of the common bile duct and the implantation of 9 bipolar electrodes located in the stomach and small intestine. In 13 experiments performed on 4 dogs the interdigestive myoelectric activity was recorded and plasma motilin and PP levels were determined by radioimmunoassay during: 1) the control period where the spontaneous bile circulation was preserved, 2) bile depletion with or without intravenous motilin (56 pmol.kg-1.hr-1) infusion, 3) intraduodenal infusion of 50 mM Na-taurocholate with or without intravenous infusion of PP (400 pmol.kg-1.hr-1). During 88 additional experiments performed on all operated animals, which comprised the control studies, bile deprivation experiments and bile or bile acid infusions, the interdigestive myoelectric activity was recorded along with the estimation of sites of phase III origin. Motilin infusion at the lack of bile and bile acids in the intestine elicited the premature phase III in the duodenum, markedly increased the percentage of phases III originating from the stomach, inhibited the arrival of phase I of the myoelectric cycle and lowered plasma PP level. Infusion of PP despite the presence of bile acids in the small intestinal lumen caused the phase III originated from the proximal or mild jejunum and lowered plasma motilin level. Thus, unlike bile or bile acids, both motilin and PP are directly responsible for the appearance of phase III in the stomach and proximal small bowel of the dog. The luminal bile appears only to play a mediatory role influencing the release of the hormonal peptides examined here.

Animals↗
PubMed1989

[Bile fractions and bile secretory component of the migrating myoelectric complex in dogs].

In 4 dogs the functional cholecystectomy was performed, then the common bile duct was cannulated and 9 bipolar electrodes were implanted into the stomach and small intestine. During the interdigestive period when the experiments were carried out both bile flow and electric activity of the gastrointestinal tract were monitored under the following conditions: 1) short or long bile depletion periods, 2) intraduodenal infusions of 50 mM sodium taurocholate, sodium taurodeoxycholate or sodium taurochenodeoxycholate, 3) intraduodenal bile infusions. Total bile acid content was determined in bile samples, then both bile acid-dependent (BAF) and bile acid-independent fractions (BAIF) of bile were calculated. The appearance of the bile secretory component was in 65% correlated with phase III of the MMC while the height of its amplitude usually exceeded 100% of the initial value. In all experimental groups the marked increase in BAIF was followed by a slight enhancement of BAF or its absence. Fluctuations of the biliary fractions were determined by a degree of depletion of the systemic bile acid pool. The changes described were more distinct during infusions of dihydroxy bile acids. The results suggest the importance of BAIF in the appearance of the bile secretory component of the MMC.

Action Potentials↗