Distension-induced duodenal contractions vary with the phases of the canine interdigestive migrating motility complex

The aim of the study was to evaluate whether the sensitivity for distension-induced contractions in the duodenum varied with the phases of the interdigestive migrating motility complex (MMC).

Four beagles (12-17 kg) with gastric fistulas were studied by means of perfused low-compliance manometry. A 2.5-cm-long balloon was placed in the third part of the duodenum. Side holes for pressure measurements were placed inside the balloon, 2cm proximal to the balloon, and in the antrum. Two-minute distensions with balloon pressures of 10 cmH2O were repeated in 10-min intervals during 17 MMCs. Twelve MMCs were also recorded without doing distensions.

Balloon distension did not affect the duration of phase III and the MMC. In the beginning of phase I, distension did not significantly affect duodenal motility whereas distension induced contractile responses in late phase I, early phase II and late phase II (p < 0.05). The highest increase from the pre-distension to distension period was observed in early phase II (average 4 contractions min(-1)). However, considering the level of pre-distension contraction frequency, the fractional increase was by far the highest in late phase I. In phase III no difference was found between the periods before and during distension (15.8 +/- 0.7 versus 15.8 +/- 0.5 contractions min(-1)). The effect of balloon distension in phase IV was difficult to evaluate due to the inconsistent nature and sometimes rapidly decreasing activity in phase IV. Duodenal distension did not change frequency and amplitude of antral phase II contractions (p > 0.5).

Duodenal balloon distension elicited ascending contractions in the canine duodenum in late phase I and in phase II. A refractory phase was demonstrated in the beginning of phase I while in phase III the frequency of contraction could not be increased further.