Continuous recording of pyloric sphincter pressure in dogs. Relationship to migratory motor complex.

Antral, pyloric, and small bowel intraluminal pressures were continuously recorded in dogs with gastric and duodenal cannulae. A cyclic phasic activity related to fasting motility in the antrum and small bowel was observed at the level of the pylorus. During phase I of the interdigestive motility complex, manometry was characterized by pressure variations of 31 +/- 2 cm H2O. During phase II, two type of waves were observed: small waves similar to those seen during phase I, with superimposed waves of higher amplitude (89 +/- 1.9 cm H2O). Pyloric pressure during phase III, showed a predominance of waves of even greater amplitude: 103 +/- 3.9 cm H2O. A basal tone of 65.6 +/- 3.2 cm H2O above the duodenal pressure was recorded throughout the period of study; but during phase III, frequent decreases in basal pressure were also observed. This relaxation of the pylorus during phase III of the IDMC may be related to the mechanism for size discrimination of particles leaving the stomach at the gastroduodenal junction.