メディエイゴ

Historically(1), many scientists have regarded itching(2) as just a less intense version of pain. They have spent decades searching for itch-specific(3) nerve cells(4) to explain how the brain(5) perceives(6) itch differently from pain, but none have been found.

Now researchers(7) at Washington University School of Medicine in St. Louis have discovered that those itch-specific neurons(8) do exist in mice(9), and their studies suggest that itch and pain signals are transmitted(10) along different pathways(11) in the spinal cord(12). Reporting in the Aug. 6 issue of Science Express, the advance(13) online publication of the journal Science, the researchers say they can knock out(14) an animal's itch response(15) without affecting its ability to sense and attempt to avoid pain.

"This finding has very important therapeutic(16) implications(17)," says Zhou-Feng Chen, Ph.D. (18), the study's principal investigator(19). "We've shown that particular neurons are critical(20) for the itching sensation but not for pain, which means those cells may contain several itch-specific receptors(21) or signaling molecules(22) that can be explored or identified as targets for future treatment or management of chronic(23) itching."

The new finding follows research by Chen and his team in 2007 that identified the first itch gene(24) ― gastrin-releasing peptide receptor(25) (GRPR) ― in the spinal cord. They also showed that when mice were exposed to things that make them itchy(26), those without a GRPR gene scratched(27) less than their normal littermates(28). Chen's team also found GRPR in a group of spinal-cord cells called lamina 1(29) neurons that relay(30) both itch and pain sensations to the brain.