Tissue injury prompts the release of a number of proalgesic molecules that induce acute and chronic pain by sensitizing pain-sensing neurons (nociceptors) to heat and mechanical stimuli. In contrast, many proalgesics have no effect on cold sensitivity or can inhibit cold-sensitive neurons and diminish cooling-mediated pain relief (analgesia). Nonetheless, cold pain (allodynia) is prevalent in many inflammatory and neuropathic pain settings, with little known of the mechanisms promoting pain vs. those dampening analgesia. Here, we show that cold allodynia induced by inflammation, nerve injury, and chemotherapeutics is abolished in mice lacking the neurotrophic factor receptor glial cell line-derived neurotrophic factor family of receptors-α3 (GFRα3). Furthermore, established cold allodynia is blocked in animals treated with neutralizing antibodies against the GFRα3 ligand, artemin. In contrast, heat and mechanical pain are unchanged, and results show that, in striking contrast to the redundant mechanisms sensitizing other modalities after an insult, cold allodynia is mediated exclusively by a single molecular pathway, suggesting that artemin-GFRα3 signaling can be targeted to selectively treat cold pain.W hen pain continues past its usefulness as a warning of potential tissue damage, it becomes a debilitating condition for which few viable treatments are currently available. The result can be an exacerbation of pain in response to both innocuous (allodynia) and noxious (hyperalgesia) stimuli (1). For example, pain felt with normally pleasant mild cooling (cold allodynia) occurs in many pathological conditions, such as fibromyalgia, multiple sclerosis, stroke, and chemotherapeutic-induced polyneuropathy, but what underlies this specific form of pain at the cellular or molecular level is largely unknown (2-5). Pain-sensing afferent neurons (nociceptors) are sensitized during injury or disease, in part, by a vast array of proalgesic compounds termed the "inflammatory soup" (e.g., neurotrophic factors, protons, bradykinin, prostaglandins, and ATP) (1). These substances are released locally at the site of injury by infiltrating immune cells, such as macrophages, neutrophils, and T cells, as well as resident cells, including keratinocytes and mast cells (6), and either directly activate sensory receptors or sensitize them to subsequent stimuli (7). Moreover, prolonged inflammation can lead to central sensitization (in the spinal cord and brain) and bring about long-lasting chronic pain that persists after acute inflammation has resolved. Thus, a better understanding of the molecules involved in neuroinflammation may lead to therapeutic options for acute and chronic pain.Of the range of proalgesics known to promote pain, only nerve growth factor (NGF) and the glial cell line-derived neurotrophic factor family ligand (GFL) artemin have been shown to lead to cold hypersensitivity (8-11). Both are major components of the inflammatory soup and produce nociceptor sensitization and pain through their cognate cell surface rece...