SUMMARY In five conscious dogs motility of the antrum, pyloric sphincter, and duodenum was recorded with strain gauge transducers and induction coils. Gastric evacuation of low, medium, and high viscosity meals was measured via a duodenal cannula and observed simultaneously by radiography. Computer analysis of the propagation of the gastric waves revealed increased velocity in the distal antrum but no simultaneous contractions of the terminal antrum and pyloric sphincter. Radiography showed, and measurements of the antral diameter confirmed, that the indentations of the gastric waves were significantly deeper with the low viscosity liquid meal compared with the medium and high viscosity meals. Thereby, retropulsion of the medium and high viscosity ingesta was produced. Results indicated that gastric evacuation was regulated predominantly by the depth of the peristaltic indentation, which depended on the viscosity ofthe gastric contents. Nothing indicated that the phasic contractions of the pyloric sphincter were of importance for the regulation of gastric emptying.In previous studies on rabbits' it was found that gastric evacuation depended on the viscosity of the test meals. These findings were in agreement with the results of other groups which have measured gastric emptying of solid particles and of liquids labelled with isotopes.3-7 However, little is known about the different mechanisms involved in the gastric emptying of liquids and solids. Dozois et aL8 and Wilbur and Kelly9 studied the effect of antrectomy and vagotomy on gastric emptying of liquids and of radiopaque plastic spheres in dogs. They concluded that the gastric emptying of liquids is regulated by the proximal stomach, whereas that of solids is regulated by the distal stomach. The simultaneous contractions of the terminal antrum and of the pyloric sphincter produced retropulsion as described in dogs'0 and in humans."-'3 Thereby, the plastic spheres were retained in the stomach, while liquids were emptied very quickly. These results support the idea ofCannon'4 that the pyloric sphincter is the 'keeper of the gate'. However, it is doubtful whether the evacuation of large plastic spheres represents the emptying pattern of normal food. Moreover, these results are largely based on fluoroscopic observations. Exact measurements of Our objective was to clarify the mechanism by which gastric evacuation of liquid and visc us ingesta is regulated. This was accomplished by simultaneous radiography, recording the gastric and duodenal motility, and measuring the gastric evacuation.The study was part of a dissertation.'5 An abstract of the results was presented at the 7th

SUMMARYIn five dogs gastric emptying of low, medium and high viscosity meals was measured via a duodenal cannula. The rate of emptying depended on the viscosity of the test meals: the time for half emptying was 45+22min with the low viscosity liquid meal (I centipoise), 28-9 + 9 5 min with the test meal of medium viscosity (105 centipoise), and 43 + 11 8 min with the test meal of high viscosity (106 centipoise). The emptying curves of the medium and high viscosity meals were sigmoid, whereas the curve representing the emptying of the low viscosity liquid meal followed an exponential pattern. Results indicate that the viscosity of the meal is an important factor for the rate of gastric emptying.

SUMMARYIn unanaesthetized dogs gastroduodenal motility was investigated by simultaneous transducer recordings and fluoroscopy; gastric emptying was measured via a duodenal cannula. Intravenous infusion of 5-hydroxytryptophane enhanced both gastric emptying and antral and duodenal motility. The intravenous injection of insulin was followed by an initial inhibition ofantral and duodenal motility and of gastric emptying. In a second phase antral and duodenal contractions were augmented, while the proximal stomach relaxed. Thereby, gastric emptying increased only slightly in spite of the strong antral activity. It is concluded that several factors are involved in controlling gastric emptying.