An integrated organismic response to lower gut stimulation.

Lean Sprague-Dawley rats underwent surgery in which 10 or 20 cm of the lower ileum was transposed to the middle of the duodenum. After the surgery, food passed through the stomach and upper duodenum before moving into the transposed ileal segment. Unabsorbed food moved on into the lower duodenum and continued down the rest of the digestive tract. Control rats had either 20 cm of ileum removed from normal continuity or had 20 cm of jejunum transposed to mid-duodenum. Ileal transposition led to a reduction in food intake and a loss of body weight that depended on the length of the transposed segment. These changes were most striking in the second 10-day post-surgical period. At sacrifice, the stomach and small intestines were significantly enlarged even though the transposed rats had lost about 10% of their body weight. The pancreas increased significantly in relative weight. These behavioural and physiological changes are interpreted as an integrated response that prevents undigested food from reaching the terminal ileum in an animal with normal intestinal continuity. A second experiment with Lewis parabiotic rats confirmed that stimulation of the lower small intestines, cecum and colon is involved in the normal control of food intake. Rats that had an unstimulated lower gut increased food intake while those that had their lower gut doubly stimulated with undigested chyme, reduced their intake.