Description: Johns Hopkins researchers may have narrowed in on nerve cells in mice that signal when something feels itchy, but not when it causes pain. Even if a stimulus that would normally be perceived as painful is introduced to the nerve cells, the brain interprets the stimulus as itchy, the research found.
Researchers: Eleven authors from the Hopkins school of medicine: Xinzhong Dong, Liang Han, Qin Liu, Hao-Jui Weng, Zongxiang Tang, Yushin Kim, Kush Patel, Zhe Li, Benjamin McNeil, Shaoqiu He and Yun Guan. Other contributing authors were four researchers from Yale University and two from Sichuan University in China.
Stage of research: The findings were published Dec. 23 in the journal Nature Neuroscience. After homing in on the itch-specific nerve receptors, the researchers found that after killing those nerve cells, scratching responses were reduced to varying degrees when the mice were exposed to itchy stimuli. They eventually found that injecting capsaicin, the chili pepper component responsible for a burning sensation, into the cheeks of genetically altered mice prompted them to scratch, whereas normal mice massaged themselves to relieve the sensation.
Implications: If the findings can be replicated in humans, it could be a step toward targeting itchiness, a common side effect of some life-saving medications. Morphine and anti-malaria drug chloroquine, for example, are known to cause chronic itchiness that can cause some patients to give up on treatment.
Breakthrough: Researchers break down the impulse to itch
Xinzhong Dong (Courtesy of Johns Hopkins, Baltimore Sun / September 18, 2006)