Pain specialist Dr. Eske Aasvang of Denmark is trying a new compound in clinical pain relief trials: Capsaicin. Yes, the very same compound that makes hot peppers hot, and unwary college students who've never heard of chicken vindaloo before want to shoot themselves. Capsaicin, as it turns out, bonds tightly to the receptors of C-type nerve fibres, which trainsmit status messages to the brain that are interpreted as pain. Those receptors will fire briefly (as anyone who's ever eaten chili can attest to) but then go silent because the nerves will have exhausted their supplies of neurotransmitters. It is expected …