Myoelectric motility patterns during mechanical obstruction and paralysis of the small intestine in the rat.

The purpose of the present study was to analyze changes of the myoelectric activity in experimental mechanical obstruction and paralytic ileus of the small intestine. Myoelectric activity was recorded in the upper small intestine of conscious, fasted rats by three bipolar electrodes implanted 10 cm apart. In the basal state regular myoelectric motility complexes (MMCs) were registered in all experimental animals. Obstruction of the small intestine (n = 13) was produced by a ligature between the middle and distal electrodes. Proximal to the obstruction regular MMCs continued. After 45 +/- 15 min at the middle (p less than 0.01), and 85 +/- 10 min at the duodenal electrode (p less than 0.01), MMCs disappeared. Another motility pattern was established, characterized by clusters of spikes, occurring regularly with 2-min intervals, separated by short silent periods, and a rapid aboral migration (p less than 0.01). Distal to the obstruction the propagation of MMCs was immediately disrupted. After a quiescent period of 13 +/- 3 min irregular spiking occurred and continued throughout the experiment (p less than 0.01). Intraperitoneal instillation of 0.1 M hydrochloric acid (n = 8) produced a prompt and long-lasting inhibition of the MMCs. The quiescence lasted for 70 +/- 23 min, until the MMCs reappeared (p less than 0.01). It is concluded that complete intestinal obstruction is followed by a series of significant and well-defined changes of myoelectric activity on both sides of the obstruction. Nociceptive stimulation of the peritoneum produces intestinal paralysis. The immediate inhibition of the motility indicates that the paralysis is not secondary to inflammatory reactions.