Equipotency of anti-curare activity of 4-aminopyridine and 3,4-diaminopyridine in anesthetized rats.

In the curarized preparation, 3,4-diaminopyridine (3,4-DAP) and 4-aminopyridine (4-AP) were equiactive in their ability to antagonize d-tubocurarine caused complete depression of the indirectly elicited twitches of the sciatic nerve-tibialis anterior muscle preparation in anesthetized rats. In the non-curarized preparation, 3,4-DAP showed 2.3 to 4.0 times stronger augmentation of the indirectly elicited twitches than 4-AP, but both the drugs increased equivalently and slightly the maximally elicited twitches of the chronically denervated muscle. The results suggest that the difference of their prejunctional effects is masked by the postjunctional effects of d-tubocurarine in the indirectly elicited twitches.