More on the Neurobiology of Itch

I have an earlier posting on neuro-transmission of itch or pruritis. This focused on the role of Toll-like Receptor 3 (TLR 3). This posting looks at the role of Gastrin-Releasing Protein (GRP) and the Gastrin-Releasing Protein Receptor (CRPR) in chronic itch. The findings are important because this condition affects millions worldwide and results in a costly erosion of quality of life.

Here chronic itch was studied in Macque Monkeys over a period of 4 years. The expression patterns of GRP, GRPR and PGP9.5 were accessed by immunohistochemistry: Leigh A Nattkemper, Zhong-Qiu Zhao, Anna J Nichols, Alexandru D P Papoiu, Carol A Shively, Zhou-Feng Chen and Gil Yosipovitch. Over-Expression of the Gastrin-Releasing Peptide in Cutaneous Nerve Fibers and its Receptor in Spinal Cord in Primates with Chronic Itch. Journal of Investigative Dermatology accepted article preview 4 April 2013; doi: 10.1038/jid.2013.166.

Images: Double labeling of PGP9.5 and GRP in skin of primates representing mild, moderate and severe itch. Primates with higher scratching severity showed in increase in the co-localization of PGP9.5 and CRP at the dermal-epidermal junctions (arrows).

In addition to increased PGP9.5/GRP expression in the skin, similar results were shown for expression of GRP/GRPR in DRGs. This makes GRP and its receptor candidate drug targets for chronic itch or pruritis in humans.