The neuromuscular blocking action of benzoquinonium chloride in the cat and in the hen.

Benzoquinonium (Mytolon) has been shown to produce a curare-like rather than a decamethonium-like paralysis of neuromuscular transmission in the tibialis anterior and soleus muscle of cats and the gastrocnemius muscle of hens. In the cat, but not in the hen, benzoquinonium had an additional action in preventing both the twitch potentiating action and the anti-curare action of edrophonium, neostigmine, eserine, and tetraethyl pyrophosphate. Paralysis produced by benzoquinonium was antagonized by injected acetylcholine and by acetylcholine liberated by tetanic stimulation of the motor nerve but, in the cat, anticholinesterases were without effect even when they were first administered in circumstances in which acetylcholine accumulation might be expected to occur. These findings suggested that inhibition of cholinesterase played little part in the skeletal muscle effects of the anticholinesterases studied. Although anticholinesterases did not antagonize benzoquinonium paralysis in the cat, they nevertheless potentiated the antagonistic action of injected acetylcholine.