Myogenic and neural control of intestinal transit were investigated in a model of distension‐induced peristalsis. A comparison was made between the electrical and mechanical activities and outflow of contents observed in control mice and in W/W v mice, which lack the interstitial cells of Cajal associated with Auerbach's plexus. Distension caused a periodic appearance of increased motor activity due to stimulation of enteric nerves in both control and W/W v mice. Excitation was primarily delivered by cholinergic nerves, whereas periodic inhibition was mediated by neuronal nitric oxide. In control mice, outflow was driven by propagating slow‐wave activity and was only in the aboral direction. Outflow only occurred when slow waves carried sufficient action potentials to cause phasic intraluminal pressure increases of ≥ 1 cmH2O through direct stimulation of the musculature or by distension‐induced neurally mediated activation. In W/W v mice, outflow was associated with propagating action potentials that occurred due to either neural stimulation or direct muscle stimulation. Action potential propagation and outflow occurred in both oral and aboral directions. In summary, in both control and W/W v mice, distension induced periodic motor activity through stimulation of the enteric nervous system. Intraluminal contents were not moved in front of such motor activity. Rather, within such periods of activity that occurred concurrently throughout an entire segment, pulsatile outflow was directed by individual propagating slow waves with superimposed action potentials in control tissue, and by propagating action potentials in W/W v mice, which lack interstitial cells of Cajal.

In an in vitro model for distention-induced peristalsis in the guinea pig small intestine, the electrical activity, intraluminal pressure, and outflow of contents were studied simultaneously to search for evidence of myogenic control activity. Intraluminal distention induced periods of nifedipine-sensitive slow wave activity with superimposed action potentials, alternating with periods of quiescence. Slow waves and associated high intraluminal pressure transients propagated aborally, causing outflow of content. In the proximal small intestine, a frequency gradient of distention-induced slow waves was observed, with a frequency of 19 cycles/min in the first 1 cm and 11 cycles/min 10 cm distally. Intracellular recording revealed that the guinea pig small intestinal musculature, in response to carbachol, generated slow waves with superimposed action potentials, both sensitive to nifedipine. These slow waves also exhibited a frequency gradient. In addition, distention and cholinergic stimulation induced high-frequency membrane potential oscillations (~55 cycles/min) that were not associated with distention-induced peristalsis. Continuous distention produced excitation of the musculature, in part neurally mediated, that resulted in periodic occurrence of bursts of distally propagating nifedipine-sensitive slow waves with superimposed action potentials associated with propagating intraluminal pressure waves that caused pulsatile outflow of content at the slow wave frequency.

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