Relationship between small intestinal fasting motility and vomiting in dogs.

Preceding vomiting, several changes in small intestinal motility have been described. They consist mainly of high-amplitude retrograde contractions and inhibition of motility before and after these contractions. The recordings of 94 episodes of emesis occurring spontaneously, during manometric studies of intestinal motility by means of infused catheters in dogs with gastric and duodenal cannulae, showed that 95.7% of all episodes developed during phase II of the migratory motor complex. In order to establish whether different phases of the fasting cyclic activity are associated with a different sensitivity to emetic stimulus, two agents, apomorphine, a centrally acting drug and copper sulfate, a peripherally acting agent, were administered at the beginning of phases I and II of the migratory motor complex. Coincident with spontaneously occurring vomiting, a statistically significative greater number of responses to both emetic agents was observed during phase II as compared to phase I. This finding suggests that cyclic changes of the small bowel motility are related to changes in the threshold of the vomiting center.