The effects of electrical field stimulation and tetrodotoxin on ion transport by the isolated rabbit ileum.

To determine whether intramural nerves affect intestinal ion transport, we studied the effect of electrical field stimulation (EFS) on the movement of ions across isolated rabbit ileum. EFS increased the transmural electrical potential difference and the short circuit current (Isc), caused C1 secretion, and reduced conductance, but did not alter fluxes of Na or the residual current (JRnet). The neurotoxin, tetrodotoxin, prevented all the changes caused by EFS but did not prevent the increase in Isc caused by theophylline (5 mM), carbachol (10 micrometer), or glucose (10 mM), or the reduction in Isc caused by norepinephrine (10 micrometer), implying that tetrodotoxin prevented responses to EFS by affecting electrically excitable cells rather than epithelial cells. Tetrodotoxin also enhanced the mucosa to serosa fluxes of Na and C1, reduced the potential difference and Isc, and increased conductance. The site of tetrodotoxin action is uncertain because it may affect the release of at least four neuro-transmitters and the release of peptides from endoctine cells. The Isc response to EFS was not affected by atropine (10 micrometer), physostigmine (10 micrometer), or by hemicholinium (1 micrometer). The mechanism by which EFS causes C1 secretion remains to be determined.