Effects of Enteric Neural Stimulation on Chloride Transport in Human Left Colon in Vitro

Nonpathological segments of muscle-stripped left colon from patients undergoing surgery for carcinoma, diverticulitis, or other causes were set up in flux chambers in order to determine the influence of intrinsic neurons on ion transport. In the basal state, both sodium and chloride were actively absorbed, and there was no significant residual ion flux. Electrical field stimulation of the intrinsic mucosal innervation evoked an increase in short-circuit current that was dependent on stimulus frequency and strength. The response was mimicked by scorpion venom, which is known to depolarize neurons, and was nearly abolished by tetrodotoxin, which prevents neurotransmitter release. Atropine reduced, but did not abolish, the response to neural stimulation. Carbachol, aminophylline, and theophylline significantly increased short-circuit current above basal levels. Electrical field stimulation evoked an increase in short-circuit current that could be accounted for by a decrease in net chloride absorption without any significant effect on sodium absorption or residual ion flux. These results suggest that ion transport in the human left colon is regulated by intrinsic submucosal cholinergic neurons as well as other neuronal types, and activation of these nerves could provide the basis for certain diarrheal disorders.