Chronic itch is an often difficult and sometimes debilitating symptom of many skin diseases and other disorders. Researchers have been trying to determine for decades if there are separate neuronal pathways for pain and itch. However, studies of underlying mechanisms have long been complicated and hindered by the difficulties of distinguishing itch from pain at molecular and cellular levels.
Now, researchers supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) have discovered itch-specific neurons which express a protein known as gastrin-releasing peptide receptor (GRPR) in the spinal cord of mice. Without GRPR-expressing neurons, there is no sensation of itch. The present study, recently published in Science, provides the most comprehensive behavioral evidence to support the idea that distinct subsets of neurons transmit the different sensations of pain and itch in the spinal cord.