The Grasshopper Mouse and Bark Scorpion: Evolutionary Biology Meets Pain Modulation and Selective Receptor Inactivation.

Pain, however unpleasant, is a vital part of survival, providing a motivating response to noxious stimuli that helps move us away from danger. In medicine, adequate pain control can be maintained using analgesics, many of which produce unwanted and complicating side effects, most notably opioid analgesics. Here, I review a study which explored the unique predator/prey relationship between the Southern grasshopper mouse (Onychomys torridus) and its natural prey, the Arizona bark scorpion (Centruroides sculpturatus). O. torridus has developed an analgesic response to the scorpion's usually highly painful sting and, in doing so, provides a wonderful display of ion channel function and evolutionary biology. O. torridus' unique adaptation serves as a strong example of Krugg's Principle, which states there exists a best animal specimen for any scientific question. This principle is utilized to great effect by the authors to better understand receptor activation in pain. The study gradually progresses from an animal behavior model to isolating the amino acid residue in the ion channel responsible for the pain-relieving effect of scorpion venom on O. torridus. This provides a convincing argument for the potential of highly selective analgesics and the prospective sites of action for these future drugs.