Secretory reflexes in ileum and jejunum: absence of remote effects

We have tested the hypothesis that luminal secretagogues initiate neural reflexes that alter ion transport in small intestinal segments proximal or distal to the site of the secretory stimulus. Effects of secretagogues that act by different mechanisms were studied in vitro by measuring short circuit current (ISC) of ileum or jejunum mounted in a unique flux chamber while proximal mucosa in neural continuity with the tissue was perfused with secretagogues (Na deoxycholate. Escherichia coli STa, 5-hydroxytryptamine, theophylline) or was stimulated electrically (EFS). No proximal stimulus affected distal ISC. We also studied in vivo adjacent segments of ileum or jejunum in neural continuity but with unconnected lumens. In anesthetized rabbits, we measured transmural electrical potential difference and fluid movement (Phenol red marker). Stimulation of proximal segments of ileum or jejunum with STa, or of ileum with 5-HT or Na deoxycholate did not affect distal transport. Stimulation of distal segments of ileum and jejunum with STa or 5-HT, or of jejunum with Ha deoxycholate did not affect proximal transport. We conclude that the secretion caused by luminal secretagogues in the rabbit small intestine is limited to the area of stimulation.