Vagotomy inhibits the effect of neurotensin on gastrointestinal transit in the rat

Neurotensin has previously been shown to delay gastric emptying, gastrointestinal transit and ileo-caecal emptying in the rat. To investigate the vagal influence on these effects of neurotensin, separate groups of rats were operated with combined vagotomy and pyloroplasty or with pyloroplasty alone and compared to a group of normal rats. All animals were supplied with a permanent gastrointestinal catheter and a venous catheter. After operation the rats were allowed to recover for 7 days, and were fasted for 24 h prior to the experiments. A radioactive marker of 1.0-0.5 ml Na2(51)CrO4 in isotonic polyethylene glycol 400 was instilled intraluminally in the stomach, proximal or distal the small intestine. Saline (control animals) or neurotensin (test animals) was given i.v. in each group studied. The animals were killed at 15, 30, 60, and 120 min after administration of the marker. The distribution of the marker in the gastrointestinal tract was registered with a scintillation detector and quantitative analysis of the amount of radioactivity retained in separate gastrointestinal segments was carried out. Gastric emptying was delayed by combined vagotomy and pyloroplasty (P less than 0.01) compared to pyloroplasty alone and normals. Neurotensin at doses of 6 (P less than 0.05) and 12 (P less than 0.01) pmol kg-1 min-1 retarded gastric emptying dose-dependently in normals and rats with pyloroplasty alone, but did not further slow the gastric emptying in rats with vagotomy and pyloroplasty. However, at a dose of 24 pmol kg-1 min-1 neurotensin delayed gastric emptying (P less than 0.01) compared to controls. Gastrointestinal transit was slowed down by neurotensin at a dose of 6 pmol kg-1 min-1 in normals (P less than 0.01) and rats with pyloroplasty alone (P less than 0.05). In rats with vagotomy and pyloroplasty, neurotensin at doses of 6 and 12 pmol kg-1 min-1 had no effect on gastrointestinal transit.(ABSTRACT TRUNCATED AT 250 WORDS)