The interdigestive myo-electric complex of the stomach and small bowel of dogs.

1. Szurszewski (1969) described a cyclic recurring, caudally migrating band of intense action potential activity, the activity fromt, in the small bowel of dogs fasted 18-21 hr. The finding has been confirmed by Carlson, Bedi & Code (1972) and by Grivel & Ruckebusch (1972). The objectives of the present study were to extend these observations first by indentifying the full sequence of myo-electric events in the stomach and small bowel of healthy conscious dogs fasted for 24-48 hr and for longer periods and second by determining the effect of ingestion of mild and of saline solution on the complex and the role of gastric distension in their action. 2. Under surgical anaesthesia, silver-silver chloride electrodes were implanted on the serosal surface of the stomach and small bowel of seven dogs, and recordings of electric activity were started when the dogs had recovered. One hundred and nine interdigestive complexes were studied in detail in five of the dogs during period ranging from 5 to 14 months. All observations were made while the dogs were healthy, conscious, and fasted. 3. The period of intense action potential activity, the activity frot or band, was found to be one phase of a cyclic-recurring sequence of changes in action potential activity. The entire sequence, composed of four phases, occured almost simultaneously in the stomach and duodenun and then migrated distally in sequence over the entire small bowel. As one cycle terminated in the distal ileum, another had started in the stomach and duodenum, and this cyclic recurrence continued during fasts of 4 and 5 days. 4. The cycles of the interdigestive complex tended to recur at the same time each day in three of the dogs. The mean periods of the cycles ranged from 90 to 114 min, and the mean time of their propagation from stomach to terminal ileim ranged from 105 to 134 min. The mean velocity of the activity fronts (phase III of the cycles) was 5-7-11-7 cm/min in the orad portion of the small bowel and 0-9-2-5 cm/min in the distal half. The mean calculated length of the activity front diminished from a range of 42-62 cm in the duodenum to 5-10 cm in the ileum. 5. Intragastric instillation of 400 ml. milk always interrupted the complex present in the bowel at the time of instillation and usually suppressed the next, whereas 400 ml. saline solution interrupted the complex present in the bowel only at the time of instillation. Distension of the stomach with a ballon always suppressed the interdigestive complex in the stomach and duodenum but sometimes failed to interrupt its migration along the bowe.