NPY and injury: Conditional knockdown of spinal cord NPY has been shown to increase tactile and thermal hypersensitivity primarily through Y1 receptor (Y1R) in nerve injury–induced neuropathic pain models (10, 11), whereas s.c. injection of NPY or Y2R agonist appears to exacerbate pain after nerve injury, suggesting a biphasic role of NPY in neuropathic pain at different sites (12–14).