The myogenic component in distention-induced peristalsis in the guinea pigsmall intestine

In an in vitro model for distention-induced peristalsis in the guinea pig s mall 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-se nsitive slow wave activity with superimposed action potentials, alternating with periods of quiescence. Slow waves and associated high intraluminal pr essure transients propagated aborally, causing outflow of content. In the p roximal small intestine, a frequency gradient of distention-induced slow wa ves was observed, with a frequency of 19 cycles/min in the first 1 cm and 1 1 cycles/min 10 cm distally. Intracellular recording revealed that the guin ea pig small intestinal musculature, in response to carbachol, generated sl ow waves with superimposed action potentials, both sensitive to nifedipine. These slow waves also exhibited a frequency gradient. In addition, distent ion and cholinergic stimulation induced high-frequency membrane potential o scillations (similar to 55 cycles/min) that were not associated with disten tion-induced peristalsis. Continuous distention produced excitation of the musculature, in part neurally mediated, that resulted in periodic occurrenc e of bursts of distally propagating nifedipine-sensitive slow waves with su perimposed action potentials associated with propagating intraluminal press ure waves that caused pulsatile outflow of content at the slow wave frequen cy.