Electrical Pulse Train and Single Pulse Stimulation of the Small Intestine: Acute and Chronic Studies in the Dog

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Abstract
In vitro tests have shown that electric currents may lead either to relaxation or contraction of the bowel wall. Because voluntary changes of the intestinal motility could be useful in the treatment of intestinal disorders, we investigated the reactions elicited by electrostimulation of the small intestine in the intact animal. Stimulating electrodes, electroenteromyogram electrodes, and pressure monitoring tubes were used to instrument a 5-cm segment of the proximal jejunum in five dogs in acute studies and in two dogs in chronic studies. Single pulses of 200 ms elicited a pulsatile pressure increase of 10-35 mm Hg. Pulse train stimulation was followed by a more complex reaction. Trains of 500-.mu.s, 910-Hz pulses at 30 mA evoked a 50-80 mm Hg pressure increase, 1-ms, 10-Hz trains caused an initial relaxation, followed by a pressure increase during stimulation and a further pressure increase after termination of the burst. These reactions were similar to those observed by Campbell working with colon in vitro. The chronic fasted animals reacted to 500 .mu.s, 910-Hz, 25-mA stimulation with a mean pressure increase of 26 mm Hg (n = 10) and to 200-.mu.s, 1.67-kHz, 30 mA stimulation with 28 mm Hg (n = 16). In the fasted animals a pressure increase during stimulation predominated (Campbell type I), whereas in the fed animal an additional off response after termination of the stimulation was the most common type of reaction (Campbell type II). Initial relaxation (Campbell type III) could be elicited by 1-ms, 10-Hz trains. In summary, contraction patterns similar to those observed in vitro can be achieved in anesthetized and awake animals with currents tolerated by the trained dog.

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