Benzocaine blocks μ1 wild-type Na+ currents in a dose-dependent Manner. The Benzocaine concentration that inhibits 50% of Na+ currents (IC50) is estimated to be about 0.8 mM when a test
potential of +30 mV is applied. The slope of the h∞ curve is also significantly reduced by benzocaine (from 6.6 to 9.9 mV). Mutation of μ1-N1584A also significantly increases the potency of
Benzocaine. At 1 mM, Benzocaine blocks about 55% of wild-type Na+ current but about 95% of μ1-N1584A mutant current. Benzocaine also appears to bind more strongly to its LA receptor in the N1584A
mutant than in the wild type