Molecular modification of anticholinergics as probes for muscarinic receptors. Part 4. Ileal selective muscarinic antagonists.

Systematic studies of the structure-activity relationships of atropine-like anticholinergic drugs have provided valuable information about the nature of the muscarinic receptor. In this study, the pharmacological activities of the (Z) and (E)-isomers of 2-phenylcyclohexyl diethylaminoethyl ether (1 and 2, respectively) in the isolated rat left atrium were investigated and compared with their activities in the isolated rat ileum preparation. Compound 1 was found to be one of the most ileal selective muscarinic antagonists reported to date. Other data concerning possible differences in the receptor-bound conformations of tropate- versus benzilate-derived muscarinic antagonists are also presented.