Analysis of blocking action of dimethyl dl-curine dimethochloride on neuromuscular transmission (author's transl)

Using rat's phrenic nerve-diaphragm and chick's nerve-muscle (biventer cervicis) preparations, the neuro-muscular blocking activity of O,O’-dimethyl dl-curine dimethochloride (dl- DCD) was studied. dl-DCD 2.5-2.7μg/ml blocked the indirectly elicited maximal twitches of diaphragm muscle. The blocking action was antagonized by neostigmine. During the block of the indirectly twitches, direct stimulation of the muscle elicited produced normal contractions, and the nerve action potentials remained unaffected. During partial block of the maximal twitches produced by dl-DCD, the tension of an indirectly elicited tetanus (50/s for 10 s) was poorly sustained and the post-tetanic facilitation was observed. dl-DCD also abolished the response of the biventer to ACh after its indirectly elicited maximal twitches was blocked. In rat’s phrenic nerve-diaphragm preparation, dl-DCD 2—4μg/ml produced no significant change in miniature end-plate potential (mepp) frequenecy but reduced the end-plate potential (epp) and mepp amplitudes. Neostigmine enhanced the amplitude and duration of epp induced by dl-DCD. dl-DCD 16μg/ml produced no effect on resting membrane potential of diaphragm muscle fibers. These results indicate that dl-DCD is a nondepolarizing blocking drug like tubocurarine and produced a muscular relaxation by blocking the cholinergic receptors.