Pyloric and Duodenal Motor Contributions to Duodenogastric Reflux

The motor mechanisms of duodenogastric reflux were identified in 4 healthy, conscious dogs using electromyographic and fluoroscopic recordings of stomach, duodenum and upper jejunum. A barium suspension was injected via a pre-placed cannula in the orad jejunum, during the interdigestive period. Under normal conditions, reflux was uncommon. It was produced by duodenal segmental contractions occurring when the pylorus was open, or forced open by the duodenal contractions. Reflux was more common during retrograde electrical pacing of the duodenal pacesetter potential. It was then also produced by duodenal segmental contractions associated with an open, or opening, pylorus. During intravenous administration of apomorphine, reflux occurring early in the vomiting complex, was again produced by duodenal segmental contractions associated with an open, or opening, pylorus. The major apomorphine reflux event, however, occurred later when an emetic antiperistaltic contraction, originating in the duodenum or orad jejunum swept the contents before it into the stomach.