Bombesin stimulates small intestinal motility after intracerebroventricular administration to rats

The frequency and amplitude of contractions occurring in the duodenum and the jejunum of freely-moving, unanesthetized, female Sprague-Dawley rats were determined by continuously recording intestinal intraluminal pressure. Intracerebroventricular (i.c.v.) administration of saline did not significantly alter the frequency of contractions in either small bowel region when compared with activity observed during a preinjection control period. I.c.v. administration of bombesin (0.1-10 micrograms) produced a dose-related increase in the frequency of duodenal contractions of up to 583% of control. While an increase in jejunal motility was consistently seen with doses of 1 and 10 micrograms, the lowest bombesin dose tested (0.1 microgram) produced a significant decrease in the frequency of contractions in this intestinal area. The intestinal motor effects were seen within the first 30 min after the peptide, and lasted for at least 1 h. Intraperitoneal administration of bombesin, at doses 200 times higher than those given centrally, failed to significantly alter intestinal motility at either recording site. Whether all of the complex intestinal motor effects of bombesin can be directly related to its centrally initiated inhibitory transit effect is unclear; however, the stimulation of contraction frequency in the duodenum at all doses tested suggest that the antitransit effects of bombesin may be, in part, the result of either an increase in the frequency of non-propulsive contractions or a disruption of the normal coordinated propulsive motility pattern of the duodenum.