The mode of action of curare, a well-known competitive antagonist of 
acetylcholine at the nicotinic receptor, was examined with the single channel 
recording technique. Curare can open cholinergic channels in rat myotubes, as 
suggested by Ziskind and Dennis (1978). Moreover another curare molecule can 
then block the curare-activated open channel, in line with previous results 
concerning such a mode of action. In adult rat muscle, the partial agonist 
activity of curare can also be demonstrated, though it is much weaker than in 
embryonic muscle. It is also shown that in adult muscle cell, the conductance of 
the channel (activated either by ACh or by curare) is 50-60 pS, i.e., higher 
than in the myotubes (35 pS).