Effect of pyridine aldoximes on response of frog rectus muscle to acetylcholine.

The effects of pyridine-2, 3- and 4-aldoxime methiodide (PAM) on the isotonic contracture of the isolated frog rectus abdominis muscle elicited by acetylcholine have been studied. The potentiation to acetylcholine resulting from incubation with PAM isomers is reversible and may be related to the weak anticholinesterase property of these compounds. Concentrations of the isomers higher than those needed for maximal potentiation produce a reversible block of the muscle to acetylcholine. pH studies suggest that cations are responsible for the potentiating and blocking properties of the PAM isomers.