Leptodactyline is a naturally occurring quaternary ammonium base, which is found in large amounts in the skin of some South American amphibians of the genus Leptodactylus. It is the first example of a m-hydroxyphenylalkylamine in the living organism. In vertebrates it had powerful nicotinic actions and a marked neuromuscular blocking effect. This was considered, on the basis of experimental evidence, to be of the "depolarizing" type.