Tough rodent can block the pain of a scorpion sting

In a smackdown between a venomous bark scorpion and a mouse, which would win? A house mouse would be no match for the bark scorpion’s painful sting, but the desert-dwelling grasshopper mouse can brush off the venom with apparent ease and have the scorpion for dinner.

Researchers have discovered that the grasshopper mouse (Onychomys torridus) has a biochemical trick up its sleeve that harnesses the poison to dodge the painful sting. How does it work?

The bark scorpion’s venom targets a sodium channel called Nav1.7, which is in pain-sensing neurons, and when it hits home it triggers intense pain. But the study in the US found that the grasshopper mouse has a protein at another sodium channel, Nav1.8, which binds the venom. This blocks pain signals and the rodent can get on with the attack.

“In O torridus, the channel (Nav1.8) responsible for transmitting pain signals to their [central nervous system] has amino acid variants that bind venom peptides and inhibit channel current, blocking pain signals instead of transmitting them,” write the study authors in Science.

Not only is it a neat trick to use the scorpion’s own venom to block its intended effect, but the grasshopper mouse’s strategy could also inform new interventions for tackling pain. “Our results demonstrate the key role Nav1.8 plays in pain signalling and its potential to serve as an analgesic target,” write the authors.