Physiology
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Itch is a major somatic sensation, along with pain, temperature, and touch, detected and relayed by the somatosensory system. Itch can be an acute sensation, associated with mosquito bite, or a chronic condition, like atopic dermatitis (29, 59). The origins of the stimulus can be localized in the periphery or systemic, and associated with organ failure or cancer. ⋯ In contrast, little is known about the signaling mechanisms underlying nonhistaminergic itch, despite the fact that the majority of chronic itch are mediated by nonhistaminergic mechanisms. During the past few years, important progress has been made in understanding the molecular signaling of itch, largely due to the introduction of mouse genetics. In this review, we examine some of the molecular mechanisms underlying itch sensation with an emphasis on recent studies in rodents.