Activation of (K7) K channels in enteric neurons inhibits epithelial Cl secretion in mouse distal colon.

Voltage-gated Kv7 ( family) K channels are expressed in many neuronal populations and play an important role in regulating membrane potential by generating a hyperpolarizing K current and decreasing cell excitability. However, the role of K7 channels in the neural regulation of intestinal epithelial Cl secretion is not known. Cl secretion in mouse distal colon was measured as a function of short-circuit current (I), and pharmacological approaches were used to test the hypothesis that activation of K7 channels in enteric neurons would inhibit epithelial Cl secretion. Flupirtine, a nonselective K7 activator, inhibited basal Cl secretion in mouse distal colon and abolished or attenuated the effects of drugs that target various components of enteric neurotransmission, including tetrodotoxin (Na channel blocker), veratridine (Na channel activator), nicotine (nicotinic acetylcholine receptor agonist), and hexamethonium (nicotinic antagonist). In contrast, flupritine did not block the response to epithelium-targeted agents VIP (endogenous VPAC receptor ligand) or carbachol (nonselective cholinergic agonist). Flupirtine inhibited Cl secretion in both full-thickness and seromuscular-stripped distal colon (containing the submucosal, but not myenteric plexus) but generated no response in epithelial T84 cell monolayers. K7.2 and K7.3 channel proteins were detected by immunofluorescence in whole mount preparations of the submucosa from mouse distal colon. ICA 110381 (K7.2/7.3 specific activator) inhibited Cl secretion comparably to flupirtine. We conclude that K7 channel activators inhibit neurally driven Cl secretion in the colonic epithelium and may therefore have therapeutic benefit in treating pathologies associated with hyperexcitable enteric nervous system, such as irritable bowel syndrome with diarrhea (IBS-D).