Work from scratch finds cause of itch

YALE (US) — Scientists have discovered a basis for the pricking, stinging, and burning that accompanies chronic itch that can’t be relieved by antihistamines or topical creams.

The discovery, reported in the Journal of Neuroscience, could open avenues for development of anti-itch treatments to relieve the discomfort.

Building upon a previous study that showed how the peptide BAM8-22 evokes scratching in mice, researchers tested the effect on humans. BAM8-22 produced itching in each of 15 healthy volunteers.

In comparison, another peptide that is identical to BAM8-22, except for the deletion of the last four amino acids, produced little or no sensation. Further, researchers discovered that pretreatment of the tested skin with an antihistamine cream did not inhibit the sensations evoked by BAM8-22.

“BAM8–22 binds to a receptor that is found in sensory nerve fibers supplying the skin of the mouse and a receptor that has structural similarities in human skin,” explains Robert LaMotte, professor of anesthesiology and neurobiology at Yale University.

“Development of an antagonist of this receptor may prove useful in the treatment of itch that is not relieved by antihistamines.

“Histamine is a chemical substance released by mast cells in the skin. It is a major contributor to itch from insect bites and hives caused by certain foods, drugs, infection, or emotional stress; this type of itch responds well to antihistamines.

“But for chronic itch from most disorders of the skin, such as atopic dermatitis, or itch accompanying certain neurological diseases, like multiple sclerosis or systemic diseases—including those of the liver or kidney—antihistamines are not effective.”

Other authors of the study, that was funded by the National Institutes of Neurological Disorders and Stroke,  are Parul Sikand, associate research scientist at Yale, and Xinzhong Dong, associate professor at Johns Hopkins University.

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