Intestinal motility after infusion of arachis oil into duodenum and ileum of dogs

Importance of the enteric nervous system in the control of the migrating motility complex

The migrating motility complex (MMC), a cyclical phenomenon, represents rudimentary motility pattern in the gastrointestinal tract. The MMC is observed mostly in the stomach and gut of man and numerous animal species. It contains three or four phases, while its phase III is the most characteristic. The mechanisms controlling the pattern are unclear in part, although the neural control of the MMC seems crucial. The main goal of this article was to discuss the importance of intrinsic innervation of the gastrointestinal tract in MMC initiation, migration, and cessation to emphasize that various MMC-controlling mechanisms act through the enteric nervous system. Two main neural regions, central and peripheral, are able to initiate the MMC. However, central regulation of the MMC may require cooperation with the enteric nervous system. When central mechanisms are not active, the MMC can be initiated peripherally in any region of the small bowel. The enteric nervous system affects the MMC in response to the luminal stimuli which can contribute to the initiation and cessation of the cycle, and it may evoke irregular phasic contractions within the pattern. The hormonal regulators released from the endocrine cells may exert a modulatory effect upon the MMC mostly through the enteric nervous system. Their central action could also be considered. It can be concluded that the enteric nervous system is involved in the great majority of the MMC-controlling mechanisms.

Effect of ileal oleate on interdigestive intestinal motility of the dog

To determine the effect of ileal oleate on fasting intestinal motility, pairs of duodenal and ileal catheters and bipolar duodenal and jejunal seromuscular electrodes were surgically implanted in six dogs. The ileum was perfused with either normal saline (154 mM NaCl) or oleic acid emulsion (152 mM), while intestinal myoelectric activity was continuously monitored. For transit studies, a bolus of [3H]PEG was injected into the duodenum, and jejunal and ileal alliquots were collected every 15 min for a 6-hr study period. Plasma samples were collected for radioimmunoassays of peptide YY and enteroglucagon. Ileal oleate infusion increased the MMC cycle length and decreased the number of MMCs (P < 0.001) and the myoelectric spike-burst frequency/10 min in the duodenum (P < 0.05). Both duodenal-jejunal (P < 0.05) and duodenal-ileal transit (P < 0.01) were delayed markedly by ileal perfusion with oleic acid emulsion as compared to control studies. Ileal oleate increased plasma levels of peptide YY (P < 0.01) and enteroglucagon (P < 0.01). Ileal perfusion with oleate therefore activated the so-called "ileal brake," diminishing duodenal myoelectric spike bursts and slowing intestinal transit while concurrently increasing plasma levels of peptide YY and enteroglucagon.

Human interdigestive motility: variations in patterns from esophagus to colon

In most fasting mammals, motility of the foregut and small intestine undergoes regular cycles of activity. Much of the expanding knowledge of this phenomenon comes from species other than humans; however, disorders of these patterns are proposed as being clinically important. We report studies in 16 healthy humans in whom motility was recorded from intraluminal pressure sensors, both when fasting and after a meal, for prolonged periods. The recording system spanned the area from stomach to proximal colon in all subjects and included the lower esophagus in 11 of the 16 studied. Half the interdigestive cycles involved the esophagus, approximately one-third began in the gastroduodenal region, and the remainder commenced more distally. Fewer than half the migrating motor complexes were recognizable beyond the midpoint of the small bowel, and less than 10% reached the distal ileum. The migrating motor complex was more prominent at night; and its progression through the jejunum was then slower. Small meals (345-395 kcal) interrupted fasting patterns for 90-240 min, but the amount of fat did not influence the duration of these disruptions. Motility varied widely between and within individuals, and differences between normal patterns in the jejunum and ileum were particularly striking. Thus, levels of recordings must be defined accurately if putative abnormalities, of possible clinical significance, are to be interpreted correctly. Relating local motor patterns to the maximal rate of rhythmic contractions, which reflects the frequency of slow waves and is a guide to the level of the small bowel, may be helpful in this regard.

Current aspects of intestinal motility and transport

The fact that interactions exist between intestinal motility and epithelial transport ist intuitively obvious but difficult to define experimentally. Direction, velocity and rate of flow of intestinal contents depend on the absolute and relative frequency and on the force of stationary and propagated lumen-obliterating (ring) contractions. The motility pattern differs between the fasting and the postprandial state and so do the magnitude and patterns of flow. The fed pattern of motility is primarily modulated by the chemical composition of ingested meals. Changes in epithelial transport are associated with changes in motility and vice versa; these changes are initiated by physical forces or by neuroendocrine reflex activation. Stomach, small intestine and colon are coordinated by antegrade stimulatory and retrograde inhibitory mechanisms which secure completeness of nutrient absorption and facilitate elimination of food residues. Motility and epithelial transport are controlled by intramural and central neural stimulation and by hormones acting systemically, locally (paracrine action), or as neuromodulators.