[Interdigestive contractile characteristics of canine pylorus and gastroduodenal regions]

Interdigestive contractile activity of the gastric body, antrum, pyloric ring and duodenum was recorded by means of chronically implanted force transducers in 5 conscious dogs. In accordance with interdigestive phase III contractions in the gastroduodenal region, a burst of strong contractions and remarkable relaxations were observed to occur in the pyloric ring. In accordance with the intense phase III contractions in the antrum, the pyloric ring was relaxed and duodenal contractions declined and ceased as if the passage of gastric contents expelled by the strong contractions in the antrum were being done smoothly. With the termination of the antral contractions, it was observed that the duodenal contractions were initiated and followed immediately by tonal increase in the pyloric ring super-imposed with phasic contractions. These coordinated contractions between the pyloric ring and the duodenum appear to prevent reflux of duodenal contents to the stomach. Bilateral vagal cooling blockade abolished this coordination. As the gastric contractions ceased completely during vagal cooling blockade, irregular phasic contractions were initiated and no relaxation was observed on the pylorus. In conclusion, the pyloric ring is a true functional sphincter which regulates gastric emptying and prevents reflux from the duodenum in the interdigestive state, and these coordinated contractions are regulated by the vagal nerves.