When an itch strikes, scratching usually brings relief after a few moments. Scientists have now uncovered part of the biological system that tells the brain when enough scratching has occurred. The discovery reveals how the nervous system naturally limits scratching and may help explain why this process breaks down in people with chronic itch disorders. The findings were presented at the 70th Biophysical Society Annual Meeting. Researchers from the laboratory of Roberta Gualdani at the University of Louvain in Brussels identified an unexpected role for a molecule known as TRPV4 in itch triggered by mechanical stimulation, such as scratching. "We were initially studying TRPV4 in the context of pain," Gualdani explained. "But instead of a pain phenotype, what emerged very clearly was a disruption of itch, specifically, how scratching behavior is regulated." TRPV4 and the Nervous System TRPV4 is part of a family of ion channels that function like tiny molecular gateways in sensory nerve cells.…