Vagus-dependent disruption of interdigestive canine motility by gastric distension

Abstract

The purpose of this study was to determine the effect of proximal gastric distension on interdigestive patterns of canine gastrointestinal motility and to examine the role of extrinsic nerves in regulating such an effect. Serosal electrodes were placed on the antrum, duodenum, and jejunum. Animals were studied before and after transthoracic vagotomy or after neural isolation of the entire jejunoileum (extrinsic denervation). Proximal gastric distension for 5 h was provided by inflating with air a thin complaint bag placed into the proximal stomach after the onset of phase III of the migrating motor complex (MMC). Four volumes (0, 1.5, 12.5, and 25 ml/kg) were each tested four times in each animal. In neurally intact animals, gastric distension with volumes of 12.5 and 25 ml/kg consistently abolished the MMC in the antrum (100%), duodenum (96%), and proximal jejunum (greater than or equal to 62%), but less often in distal jejunum (greater than or equal to 25%). After vagotomy, gastric distension did not inhibit cycling of the MMC in the antrum, duodenum, or proximal or distal jejunum. After extrinsic denervation of the jejunoileum, gastric distension inhibited the MMC in the antrum and the duodenum but had no effect in the proximal or distal jejunum. These findings suggest that nonnutrient proximal gastric distension may contribute to postprandial changes in patterns of myoelectric activity in the upper gastrointestinal tract and that this effect is mediated by the vagus nerves.

Functional association between proximal and distal gastric motility during fasting and duodenal nutrient stimulation in humans

“…The current study extends our understanding of the relationship between proximal and distal gastric motor activity in humans, during both fasting and in response to duodenal nutrient stimulation. During fasting, the observed relationship between fundic and PAWs in the current study (32%) is within the range previously reported in dogs 2,14,22 and humans. 15 The main new finding is, however, that the functional association persists during nutrient stimulation in contrast to the situation in dogs.…”

“…During fasting, the observed relationship between fundic and PAWs in the current study (∼32%) is within the range previously reported in dogs 2,14,22 and humans 15 . The main new finding is, however, that the functional association persists during nutrient stimulation in contrast to the situation in dogs 2,3,14,22 . This difference may be due to the disappearance of fundic volume waves during nutrient infusion in dogs, 2,3,14,22 whereas in humans, duodenal nutrients reduced rather than abolished the frequency and volume amplitude of the FW.…”

“…15 The main new finding is, however, that the functional association persists during nutrient stimulation in contrast to the situation in dogs. 2,3,14,22 This difference may be due to the disappearance of fundic volume waves during nutrient infusion in dogs, 2,3,14,22 whereas in humans, duodenal nutrients reduced rather than abolished the frequency and volume amplitude of the FW. Nevertheless, whilst fluoroscopic studies in dogs have suggested that this functional association is important for the re-distribution of proximal gastric content distally for subsequent emptying, 14,22 its importance in humans gastric emptying function requires further investigation with imaging.…”

“…Current notions hold that slow-waves for the pacemaker region do not propagate proximally into the fundus because of its less negative resting membrane potential and other properties that limit it excitability. 28 Overall, as with the mediation of the fundo-antral reflex, 16,22 further study is required to examine whether extrinsic vagal input to the intrinsic intramural neural circuitry mediates the functional association between the two gastric regions. A characteristic feature of the proximal gastric response to duodenal nutrient was the biphasic pattern of relaxation.…”

Enteric Physiology of the Transplanted Gut: Absorption and Motility

“…In contrast, the postpran dial disruption of the MMC by a meal may involve local mechanical (and ultimately neural) factors. The gastric distension that accompanies ingestion of a meal appears to disrupt the fasting MMC throughout the upper gut, independent of luminal nutrients [111], and is mediated by both ascending and descending vagal pathways [112]. Similarly, luminal flow in the small intestine also alters global motor patterns independent of nutrient value of the luminal content [113]; this effect is independent of vagal integrity.…”