Hardcore Mice use Scorpion Venom as a Painkiller

Grasshopper mice have a unique adaptation that makes them immune to the venom of bark scorpions. Unlike other mammals, which experience intense pain from the venom due to the NAV 1.7 sodium ion channel, grasshopper mice have an altered NAV 1.8 channel. This adaptation allows the venom to bind to NAV 1.8, shutting it down and preventing pain signals from reaching the brain. Research has shown that this adaptation is due to a change in just two amino acids in the NAV 1.8 protein, effectively turning the venom into a painkiller for these mice.

In what way does the venom of bark scorpions affect the pain pathways in mammals?

What genetic change allows grasshopper mice to resist the effects of scorpion venom?