Now, how can we tie these results to an analgesic effect? A
general idea about an ideal painkiller is a compound that
blocks Nav1.8 in a use-dependent way (e.g., lidocaine). Here,
we discuss how a compound like BTX, which does not
simply block but profoundly modulates Nav1.8, can also
cause an analgesic effect. It is known from disease-associated
mutations that alterations in either a channel’s selectivity or
gating alter the electrical excitability of the cell. In practice,
functional studies of mutant channels have shown that the
primary defect is usually an alteration in gating and that for
sodium channelopathies the gating defects tend to increase
the likelihood of mutant Naþ channels being open. Such
gating defect will depolarise the cells, which may either cause
hyperexcitability (as in myotonia) by triggering spurious ac-
tion potentials or chronically depolarise the cell to a re-
fractory unexcitable state (as in paralysis). Computer
simulations in a model cell demonstrated that 2% of
non-inactivating Naþ channels cause a myotonic response,
however, a slightly larger proportion of non-inactivating