Scientists identify molecule that triggers itching in mice

Science News : An itch is believed to be recognized by neurons that have fibers extending into the skin. The neurons then trigger the release of neurotransmitter molecules that pass the signal to neurons in the spinal cord and then into the brain. Mark Hoon and Santosh Mishra of the National Institute of Dental and Craniofacial Research in Bethesda, Maryland, determined which molecules were produced by the original neurons and identified one, natriuretic polypeptide b (Nppb), as the most abundant. They then removed the gene in mice that produces Nppb and tested the mice’s reaction to the injection of itch-inducing substances. The Nppb-lacking mice did not respond to the injections. The researchers also tried blocking the reception of Nppb by neurons in the spinal cords of normal mice and found another significant reduction in scratching in response to itching. The research revealed that only a fraction of the neurons with fibers in the skin produced Nppb. The other neurons could be responsible for producing the chemicals that transmit pain or temperature.