In vivo identification of muscarinic receptors on rat colonic epithelial cells. Binding of [3H]-quinuclidinyl benzilate.

(1) We have demonstrated that intravenously administered [3H]-quinuclidinyl benzilate binds to rat colonic and ileal epithelial cells. The binding was prevented by pretreatment with atropine and QNB. (2) Binding was stereoselective in favor of dexetimide, the biologically more active optical isomer of benzetimide. (3) The results with intestinal epithelial cells were qualitatively the same as those obtained using heart and gut muscle as controls. (4) QNB inhibited pilocarpine-induced fluid accumulation in ligated gut segments. (5) The results support the concept that cholinergic receptors, which mediate intestinal secretion, exist on rat intestinal epithelial cell membranes.