Long a mystery, the sensation of itch has yielded a clue. The neurons that detect itch rely on a newly identified chemical to send the “I need to scratch!” message to the brain, according to a study in mice. Remove the molecule, and the mice don’t itch, researchers report in the May 24 Science.
For people, an itch can be annoying or it can be debilitating. But researchers don’t know yet how the brain senses an itch. Treatments for itch often don’t work.
The new study takes a big step forward, says Glenn Giesler Jr., a neuroscientist at the University of Minnesota, Twin Cities. “Now we’re beginning to understand the mechanisms, and that’s got to lead to better treatments.”
Scientists believe that detection of itch starts in neurons with fibers that extend to the skin. Using chemical messengers called neurotransmitters, these cells relay their signal to other neurons in a region of the spinal cord called the dorsal horn. Once there, the signal passes from neuron to neuron until it reaches the brain.