Effects of a fatty meal on small bowel propulsion in intact and vagotomized rats

The mechanisms by which a fatty meal alters small bowel motility was studied in rats. The fatty meal (3 ml soya bean emulsion) was infused via a permanent gastric catheter and, simultaneously, a bile-excreted radiopharmaceutic, via a central venous catheter. After infusion for 1 h the radioactivity along the small bowel was measured from the excised bowel specimen. In fasting animals an 'interdigestive' pattern was found, characterized by the distribution of small bowel contents in well-separated portions. After administration of the fat meal, a different ('postprandial') type of transit was found, characterized by a continuous distribution of radioactivity along the small bowel. In vagotomized animals the chosen fat meal did not induce a postprandial pattern but instead the small bowel retained its interdigestive transit mode. However, in intact animals pretreated with atropine or naloxone, the fatty meal intragastrically resulted in an ordinary postprandial transit pattern. Thus, the effect of the surgical vagotomy seems to be mediated by interruption of noncholinergic, nonenkephalinergic neurons.