Carbonyl Binding Sites in the Cholinergic Receptors of the Motor-End-Plate

Publisher Website
Google Scholar
Abstract
The microelectro-osmotic application of either methylacetate (MA) or ethylacetate (EA) to the chemosensitive areas of the end-plate membrane in frog muscle is followed by depolarizations similar to those elicited by the iontophoretic application of acetylcholine from the same multi-barrelled micropipettes. The chemical function responsible for the cholinergic activity of MA and EA, well-known substrates of acetycholinesterase, appears to be their carbonyl group. If the carbonyl oxygen of EA is replaced by two hydrogens, the resulting compound is ethyl ether, which not only lacks depolarizing action but is a cholinergic blocking agent. On the contrary, if the ether oxygen of MA is removed, the resulting compound, acetone, retains the depolarizing action. These results demonstrate the presence of a carbonyl binding site in the cholinergic end-plate receptors and also that drug-receptor interactions restricted to this site are sufficient to induce receptor activation.