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Itch has long puzzled dermatology researchers as one of the most common and vexing sensations to assess and treat. It has long been known that itch can be transmitted through type-C slow nociceptors, but whether itch has a dedicated transmission line has not been determined.
Han and colleagues have now discovered a subset of neurons in mice that appear to transmit a subset of itch sensations but not acute or chronic pain. These neurons are distinguished by the expression of MrgprA3, a G-protein-coupled receptor that is activated by chloroquine. These receptors innervate the epidermis and are seen around hair follicles. Mice lacking this MrgprA3 receptor scratched much less often than control mice when challenged with the pruritogens histamin…