Researchers have uncovered a gene that transmits the itch sensation. The result means that drugs capable of providing the pharmacological equvalent of a "scratch" could soon be on the way, sparing pruritic patients the misery of chronic itch disorders like eczema. Writing in this week's Nature Yan-Gang Sun and Zhou-Feng Chen from Washington University in St Louis describe how the homed in on a small population of sensory nerves that release a transmitter substance called GRP - gastrin-releasing peptide. GRP locks onto a chemical docking station in the spinal cord called GRPR - the gastrin releasing peptide receptor. The researchers found that when they "knocked out" the gene coding for GRPR in mice, the animals became much less susceptible to itch-provoking stimuli than normal mice, but were otherwise normal. The team also found that normal mice could be made itch-resistant by injecting into the spinal fluid a chemical that blocks GRPR, confirming its role in the itch-sensing pathway. However, it's almost certain that there are some other itch pathways still waiting to be uncovered "The fact that the knockout mice still scratched a little suggests there are additional itch receptors," Chen points out. But the good news is that GRP has been studied previously in connection with certain types of cancer, so there are already a number of drugs available that are known to block it. "So now researchers can study the effect of these agents on the itch sensation and possibly move that research to clinical applications fairly soon," says Chen.