PRE-PYLORIC MECHANISMS REGULATING GASTRIC MOTOR FUNCTION IN THE CONSCIOUS DOG

Reflex mechanisms regulating gastric motor function were studied in four conscious dogs, whose stomachs had been surgically divided into separate corporal and antral pouches. Interactions between the corpus and antrum were investigated in fasted animals by balloon distension of each region. During the quiescent phase (phase I) of the migrating motor complex (MMC), distending the corpus with volumes greater than 80 ml resulted in contractions of the corpus, which persisted for as long as the distending stimulus was applied. This corporal distension also initiated antral contractions which were greater if the antrum was moderately distended and also greater with a larger corporal distending volume up to 300 ml. Graded 5 ml inflation of the antrum during the quiescent phase of the MMC stimulated antral contractions. This antral response to antral distension was augmented when the corpus was inflated but was only statistically significant with antral volumes below 25 ml. Distension of the antrum with volumes 〉 12·5 ml caused inhibition of corporal contractions during both the active phase of a migrating complex or when stimulated by corporal inflation. The degree of inhibition was proportional to the distending stimulus and was present for the duration of the applied distension. For antral volumes of 50 ml the inhibition persisted for a variable time after the stimulus was withdrawn. The inhibition of corporal activity by antral distension was still effective after blocking acid secretion with cimetidine (100 mg), which would eliminate spillage of acid into the jejunum as a cause of the inhibition. It is concluded that pre-pyloric mechanisms co-ordinate corporal and antral motor activity and would operate during gastric emptying to provide a controlled delivery of chyme to the duodenum.