Submucosal nerves and cholera toxin-induced secretion in guinea pig ileum in vitro

The effects of cholera toxin on intestinal transport parameters were examined in muscle-stripped flat sheets of guinea pig ileum in order to determine whether the effects were partly mediated by stimulation of the mucosal innervation. Cholera toxin evoked an increase in short-circuit current that reflected active ion secretion. Tetrodotoxin completely blocked neurally mediated responses to electrical field stimulation, but it did not prevent the effects of cholera toxin. In the absence of tetrodotoxin, electrical stimulation of submucosal neurons evoked a biphasic increase in short-circuit current that was produced by chloride secretion. The first phase, which was known to be cholinergic, was enhanced by cholera toxin. These results suggest that cholera toxin may mediate intestinal secretion by direct action on the enterocytes as well as by enhancing cholinergically mediated intestinal secretory processes.