Gut Motor Activity Research Articles

Role of the interstitial cells of Cajal in the control of gut motility

The interstitial cells of Cajal (ICCs) are a population of cells in the gastrointestinal tract which have a role in the control of gut motility. A comprehensive review of the scientific literature was undertaken to assess current understanding of the morphology, structure, identification, distribution, development and function of these cells. ICCs have an important role in the control of gut motility. Experimental evidence from animal studies suggests roles as pacemakers and coordinators of gut motor activity, and as intermediaries in the neural control of motility. With an increasing understanding of the distribution and behaviour of these cells in the healthy or diseased human gastrointestinal tract, there is the potential to develop novel therapeutic approaches to diseases that have gut dysmotility as a contributory factor.

Gastrointestinal Manometry

Gastrointestinal motility disorders constitute a major segment of digestive illness. Therefore, measurement of gut motor activity should be a desired goal. However the practical usefulness of gastrointestinal manometry is controversial. In this report we review the theoretical, technical, and practical problems posed by gastrointestinal manometry in health and in disease. Special emphasis is put on aspects pertaining to the indications and clinical applicability of the technique. New methodological developments that allow measurement of motor functions of the proximal stomach and the antroduodenal junction are also examined. Gastrointestinal manometry is potentially helpful in the diagnostic evaluation of patients presenting with upper gastrointestinal symptoms without demonstrable anatomic alteration as evidence by conventional diagnostic evaluation. It may help to localize the affected region of the gut as well as to monitor the evolution of the motor disorder and to determine the effect of pharmacological treatment. For a complete evaluation of upper gastrointestinal motility it is important to record gastric activity at the same time as in the intestine, during fasting and also postprandially. Manometry may help to determine the type of abnormal motor pattern that occurs in a given motor disorder. However, at the present time no specific abnormalities for specific diseases have been described. Thus, alterations in upper gut motility due to lesions at different levels of the brain-gut axis (central nervous system, autonomic nervous system or myenteric plexus) may produce a similarly deranged manometric pattern. Moreover, relations between a particular motor abnormality and the symptoms that the patient complains of may be quite variable. Still, we conclude that measurement of gastrointestinal motility has matured and proven its value to an extent that its application to clinical gastroenterology in carefully selected instances is appropriate and timely.

8 The neurophysiology of vomiting

Nausea and vomiting can be induced by a wide variety of stimuli such as pregnancy, space travel, raised intracranial pressure, radiation and cytotoxic drugs. The mechanisms by which all these diverse stimuli culminate in a final common act is unknown. From studies in the 1950s a model of the emetic reflex emerged consisting of a chemoreceptor trigger zone in the area postrema and a vomiting centre in the brain stem. This concept has been reviewed and revised in the light of recent studies. Many discussions of emesis involve detailed descriptions of the gastrointestinal events associated with the act of vomiting only—nausea and retching receiving little attention. Here we have tried to give a broader view by considering the neurophysiology of such events and have included nausea and retching, phenomena that are usually inseparable from vomiting. The possible biological function of these events is also discussed. The involvement of visceral systems (such as the heart, airways and gut) is included, and particular attention is paid to vagal mechanisms underlying the changes in gut motor activity. Emesis has long been thought to be organized by a ‘vomiting centre’; the possibility that this vomiting centre could be the parvcellular reticular formation is reviewed, as is the concept that the ‘centre’ is larger than an anatomically defined single group of cells. The mechanism of action of two clinically relevant emetic stimuli—radiation and cytotoxic drugs—is considered in detail. Recent studies of the antiemetic properties of novel 5-HT-3 receptor antagonists against radiation and cytotoxic drug-induced vomiting are discussed; these studies suggest that important advances will be made in the treatment of emesis induced by these and other related agents.

Are gut peptides responsible for the irritable bowel syndrome (IBS)?

Disturbances in gut motor activity have been proposed as a characteristic phenomenon in patients with irritable bowel syndrome (IBS). The symptoms are often associated with food intake. Several neuropeptides have a stimulatory or inhibitory effect on intestinal smooth muscle contraction. Studies on basal and postprandial plasma levels of different neuropeptides have therefore been performed in patients with IBS and been compared with those of a control group. In the whole group of IBS patients no typical gut hormone profile was found in plasma. When the IBS patients were divided into subgroups based on the predominant syndrome changes in the plasma levels of gastrin, motilin and pancreatic polypeptide (PP) were seen. In diarrhoea fasting levels of motilin and PP and postprandial level of PP were increased. In constipated patients fasting levels of gastrin and motilin and postprandial levels of gastrin, motilin and PP were decreased. Fasting and postprandial levels of gastrin were also decreased in patients with predominantly abdominal pain.

Pressure activity patterns in the canine proximal stomach: response to distension.

The stomach accommodates to distension with a minimal rise in intragastric pressure, but the effects of gastric accommodation on overall gut motor activity are unknown. In four conscious fasted dogs, constant gastric distension (0, 10, 20, 40, 80, 160, 320, and 640 ml) was produced by an air-filled intragastric bag; intrabag and gastrointestinal pressure activities (fundus, antrum, and proximal intestine) were recorded for 4 h. With the bag empty (or without bag), the proximal stomach exhibited a fasting cyclic motor pattern synchronized with that in the antrum and upper intestine. During periods of activity the fundus generated powerful phasic pressure waves. Increasing intrabag volumes up to 80 ml gradually lengthened phase II of the intestinal interdigestive motor cycle. At 160 ml or more, gut cyclic motor activity disappeared and was replaced by continuous irregular activity, although the intrabag pressure increased to less than 7 mmHg. We concluded that gastric distension markedly alters gut motor activity even though gastric accommodation prevents a major increase in intragastric pressure.

Abnormalities in gastrointestinal motor activity in patients with short bowels: Effect of a synthetic opiate

We have investigated the fasting and postprandial patterns of gastrointestinal pressure activity in a group of patients with extensive (>100 cm) resections of the distal small bowel. Each short bowel patient was studied on 2 consecutive days with random single blind administration of either loperamide (6 mg at 5 h and at 30 min before the meal) or placebo, and 20 healthy controls were studied on single days (13 basal fasting, 7 placebo). During fasting, the duration of the interdigestive motor complex was significantly shorter in patients with short bowel syndrome (71.1 ± 15.6 min vs. 109 ± 7.8 min for controls, p < 0.03); hence, the frequency of complexes was increased. The duration of phase 2 was strikingly shorter in patients (18.7 ± 7.0 min vs. 52.9 ± 8.5 min for controls, p < 0.03). Gastric emptying and postprandial motor activity were identical in patients and controls. During fasting, loperamide prolonged phase 3 (7.6 ± 2.2 min vs. 4.3 ± 1.1 min for placebo, p < 0.03). Postprandially, loperamide shortened the time from meal ingestion to the first phase 3 by 50% (p < 0.003), and increased motility index and frequency of contraction in the gut (p < 0.01). Thus, gut motor activity in the short bowel syndrome is characterized by more frequent interdigestive motor complexes, marked reduction in phase 2 activity, and a normal feeding pattern. Loperamide therapy increases feeding activity while at the same time shortening its duration.