Interaction of cholinergic ligands and local anesthetics with plasma membrane fragments from lobster axon.

Isologous local anesthetics containing the ester, thiolester, or selenolester grouping and their quaternary ammonium analogs were studied for their ability to displace [3H]nicotine from plasma membrane fragments of lobster nerve. Tertiary and quaternary analogs were equiactive. The relative ability of oxo, thio, and seleno analogs to displace nicotine was the same as their relative ability to block axonal conduction and synaptic transmission. Among cholinergic ligands, choline and aminocholine, previously shown to be inactive as depolarizing agents, were uniquely unable to displace nicotine. The findings are compatible with the presence of a biopolymer capable of binding cholinergic ligands in axonal membranes and support the postulate that the relative inactivity of quaternary compounds in intact axons is due to permeability barriers.