The aim of this study was to elucidate the variables of gastroduodenal motility determining gastric emptying. For this purpose the effects of exogenous cholecystokinin, secretin, and gastric inhibitory polypeptide on motility and gastric emptying were studied during a meal. Motility was measured with extraluminal strain gage force transducers and induction coils in unanaesthetized dogs. The pyloric diameter and the duodenal lumen were evaluated from radiographs. Gastric emptying of an acaloric cellulose meal was determined radiographically. When compared with control infusion of saline, cholecystokinin (1.7 Ivy units X kg-1 X h-1) and secretin (1.7 clinical units X kg-1 X h-1) delayed gastric emptying and diminished the force of the antral contractions, the force and frequency of the duodenal contractions, and opening of the pylorus. The contractile patterns of the duodenum were changed from propulsive to segmenting activity. Cholecystokinin additionally diminished the duodenal lumen. In contrast, gastric inhibitory polypeptide (1.5 microgram X kg-1 X h-1) did not influence gastroduodenal motility and gastric emptying. It is concluded that the motility parameters that were significantly altered by cholecystokinin and secretin are involved in the control of gastric emptying, while other parameters that remained unchanged play a minor role in the regulating process.
We wanted to determine if an acceleration of the normal emptying rate by motor stimulants interfers with control mechanisms limiting gastric emptying. Therefore, we studied the effects of 5-hydroxytryptophane (5-HTP) and cisapride on canine gastrointestinal motility and gastric emptying after ingestion of viscous acaloric and nutritive meals. Prolonged contractions and relaxations that change lumen size (isotonic component) and wall tension (isometric component) are defined as "basal contractions" and "basal relaxations", respectively. The nutrient meal emptied much slower than the acaloric meal due to several alterations of gastric, pyloric, and duodenal motility. Both drugs stimulated antral motility but failed to accelerate gastric emptying of the nutrient meal. The main causes for the failure were a basal relaxation of the proximal antrum and a basal contraction of the duodenum. In conclusion, basal contractions of the proximal antrum and duodenum play an important role in the process of gastric emptying, and under physiological conditions the control mechanisms of gastric emptying provide an optimal emptying rate that cannot be markedly accelerated by 5-HTP and cisapride.
The effect of neurotensin (10 pmol/kg/min) on gastric emptying was investigated in 5 dogs. Gastroduodenal motility was recorded with strain-gauge transducers and induction coils, gastric emptying was measured radiographically. In the first 15 min, neurotensin abolished gastric emptying, reduced antral and duodenal contractions and diminished the pyloric opening and the duodenal lumen. Subsequently, antral and pyloric activity returned to control values. The emptying rate remained diminished due to segmenting contractions and a small lumen of the duodenum. Results suggest that neurotensin influences gastric emptying mainly by its long-lasting action on the duodenum.
The aims of the study were to characterize an unusual motor pattern with orally propagated intestinal contractions occurring after subtotal gastrectomy and to clarify if orally propagated contractions also occur during the normal fasted and fed motor pattern in intact dogs. Jejunal motility was recorded with multiple closely spaced extraluminal transducers. Contractile patterns were analyzed by a special computerized method. Following a Billroth-II gastrectomy without additional vagotomy, the migrating motor complex was often disrupted and replaced by a motor pattern that consisted of contractions propagating aborally and retrograde. The propagation velocity was significantly faster compared with that of phase III contraction waves. In intact dogs, both the fasted and fed motor patterns showed a negligible number of orally propagated contractions. These results show that it is possible to differentiate between aborally and orally propagating contractions by a computerized method. Orally propagated contractions occur frequently after subtotal gastrectomy with gastroenterostomy but are an uncommon feature in intact dogs.
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