TRPA1 and obesity due to melanocortin 4 receptor deficiency: TRPA1 plays a role in various forms of pain, including neuropathic cold pain, inflammatory pain, and hereditary episodic pain syndromes.215,216 As shown by dermal experiments, the activation of TRPA1 by certain compounds triggers pain and heat sensations.215–217 Sustained activation of TRPA1 by endogenous substances induces chronic pain involved in various disorders,218 including fibromyalgia, osteoarthritis, inflammation, diabetes, obesity, migraine, neuropathy, bronchitis, and emphysema.219