Reflex co-ordination of corporal and antral contractions in the conscious dog.

This study characterizes the role of extrinsic nerves in the co-ordination of corporal and antral contractions in the dog. Fasting motor activity was recorded in conscious dogs with stomachs previously divided into separate corporal and antral pouches. Both corpus and antrum showed synchronized phases of activity and quiescence recognizable as migrating motor complexes (MMCs, duration 81.2 +/- 9.6 min, n = 4). Moreover, individual contractions were temporally linked such that corpus contractions, occurring at 76 +/- 4 s intervals, were each followed by a burst of one to three antral contractions at a frequency of 4-5 min-1. The mean latency between the onset of individual contractions in the corpus and antrum was 10.9 +/- 2.6 s (n = 4). Denervation of the antral pouch in two additional dogs did not affect the MMC cycle (mean durations 106.6 and 82.1 min) and the onset of activity in the corpus and antrum was generally co-ordinated but less precise. However, individual antral contractions were no longer linked to corporal contractions, occurring randomly throughout the corpus contraction cycle. This was associated with a lower contraction frequency in the denervated antral pouches than in the corpus (0.3 +/- 0.1 min-1 compared to 0.6 +/- 0.08 min-1). It is proposed that a vagal reflex, excited by corporal tension receptors, provides phasic excitation facilitating the generation of antral contractions. Such a reflex is likely to reinforce the myogenic mechanisms which occur in the intact stomach and thus plays a role in co-ordinating gastric peristalsis.

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 greater than 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.(ABSTRACT TRUNCATED AT 250 WORDS)