Motility of the pyloric sphincter studied by the inductograph method in conscious dogs.

The aim of the study is to evaluate the motility of the pyloric sphincter in conscious dogs by means of extraluminal transducers. For this purpose induction coils were chronically implanted in 12 dogs. After a meal the pylorus opened and closed in relation to the gastric waves. The mean changes in pyloric diameter were 5.4 +/- 1.0 mm. During phase I of the interdigestive state, the mean degree of pyloric opening was 39 +/- 18%. Gastric contractions occurring during phase II or phase III were accompanied with a marked increase in pyloric diameter; the degree of pyloric opening was 93 +/- 12%. Duodenal instillations of hydrochloric acid or oleic acid significantly diminished the pyloric diameter. Nutrients added to a viscous meal also diminished the pyloric opening significantly in comparison with an acaloric meal. Results suggest that the pyloric sphincter is involved in the control of gastric emptying. The inductograph is a useful technique to study pyloric activity without impediment of luminal flow in animals.