TLDR: They damaged a nerve in one leg of the drosophila fly. The injury was then allowed to fully heal. After the injury healed, they found the fly’s other legs had become hypersensitive through loss of the pain inhibitors (GABA).
> We amputated the right middle leg of wild-type Canton S flies, allowed the animals to recover, and then evaluated escape responses at different temperatures. While intact animals displayed minimal escape attempts when exposed to a 38°C surface, after amputation, flies showed significantly more escape behaviors.