EFFECTS OF 2-PAM AND TMB-4 ON NEUROMUSCULAR TRANSMISSION

¹ Physiology Division, U. S. Army Edgewood Arsenal, Chemical Research and Development Laboratories, Edgewood Arsenal, Maryland

2-PAM shows both excitatory and depressant actions on time responses of the isolated frog rectus abdominis and rat phrenic nerve-diaphragm preparations.

The excitatory effect of 2-PAM on time response of time frog rectus abdominis muscle to acetylcholine appears to result from the anticholinesterase property of this oxime and not from a direct depolarizing action.

2-PAM depresses the response to the depolarizing agents decamethonium and carbamylcholine which are not susceptible to hydrolysis by cholinesterase and also to acetylcholine in the eserinized frog rectus preparation.

TMB-4 showed no excitatory effects; instead its inhibitory actions on the response of time frog rectus to decamethonium, carbamylcholine and acetylcholine appeared stronger than those of 2-PAM.

Evidence was presented to show that at high dosage levels quaternary oximes increase neuromuscular block of the rat diaphragm preparation following prolonged exposure to a nonhydrolyzable depolarizer like decamethonium or to acetylcholine protected from hydrolysis by an anticholinesterase against which the oximes are ineffective.