Oral neurotensin increases gastrointestinal transit in suckling rats

Several neuropeptides known to alter gastrointestinal motility are present in milk. We investigated the effect of gastric administration of neurotensin, bombesin, somatostatin, and vasoactive intestinal polypeptide on gastrointestinal motility in suckling rats. We gavage fed 7- to 10-day-old rats with a meal consisting of 10 microliters/g of body weight of 0.9% NaCl with 51Cr tracer and one of the peptides (0, 0.1, 10, and 1,000 ng/ml). We estimated the rates of gastric emptying and the small intestinal transit from the distribution of the radioactivity in the gut. Approximately one-half of the counts emptied from the stomach in 15 min. Both gastric emptying and small intestinal transit were time dependent and were accelerated by metoclopramide and inhibited by butylscopolamine. Neurotensin 1 micrograms/ml accelerated the gastric emptying by 35% (p less than 0.02). Small intestinal transit was also accelerated (p less than 0.05). The other neuropeptides had no effect on gastric emptying and small intestinal transit. Neurotensin did not change either the gastric emptying or small intestinal transit in weaned rats, 40-50 days old, studied in the same manner. These data suggest that the intraluminal administration of neurotensin may increase gastrointestinal motility in suckling animals.