Spin labeled acetylcholine analogs: studies of cholinergic receptor

Some spin labeled acetylcholine analogs, in which the number of methylene groups between the quaternary nitrogen and the ether oxygen ranged between 1-5, were synthesized to study drug interactions with acetylcholine receptors. None of the compounds tested, with the exception of the one that contained 2 methylene groups (SL 2) had any cholinergic activity. SL 2 was not capable of producing any nicotinic cholinomimetic activity. On the other hand it proved to have a very weak nicotinic cholinolytic activity on the receptors of the frog sartorius muscle. This compound exhibited strong antagonism against muscarinic receptors of the isolated frog heart. The muscarinic cholinolytic action of the spin label ACh analog is discussed in terms of the molecular perturbation theory of drug action.