Influence of fasting and bombesin-induced myoelectric activity on the transit of small-intestinal contents in the rat.

The relation between the occurrence of the migrating myoelectric complexes (MMC) and the transit of small-intestinal contents was studied in fasted, conscious rats. MMC were monitored by means of three bipolar electrodes implanted along the small intestine 5, 20, and 35 cm distal to the pylorus. In the presence of an MMC, the radioactive marker was transported along the small intestine as one main peak and recovered aboral to the activity front. Intravenous infusion of bombesin, 3 pmol X kg-1 X min-1, disrupted the MMC and induced irregular spiking activity at all recording levels. Furthermore, during bombesin infusion the radioactive marker was propelled a considerable distance, although the transit was significantly retarded in comparison to that in the presence of an MMC (p less than 0.01). The results indicate that the small-intestinal contents are propelled aboral to an activity front. Continuous irregular spiking activity during bombesin infusion contributes less to the transit of the small-intestinal contents than the activity front of MMC observed during fasting.