Neural pathway for chronic itch

Neural pathway for chronic itch

Published in the journal Science, the new results lend insights into potential mechanisms of chronic itch, which is caused by a variety of conditions such as eczema, diabetic neuropathy, multiple sclerosis and certain types of cancers. 

The spinal cord contains a variety of neurons called interneurons or "middlemen" that process and relay sensory information from the body including the skin. The team found that some of these "middlemen" express a small protein called neuropeptide Y, or NPY for short. This neurotransmitter is present throughout the brain and has several functions, but until now, no one knew what NPY neurons did in the spinal cord.

Researchers selectively eliminated the NPY neurons in the spinal cord of adult mice. Within a week, of removing those inhibitory interneurons from the spinal cord, the mice showed excessive scratching in response to light touch without any effect on their response to chemically-induced itch or pain.

The group saw similar behaviors when they used a chemical genetic strategy to silence the NPY expressing interneurons that prevents them from communicating with the presumptive neurons that transmit this form of itch.

The fact that the NPY-deficient mice were no more sensitive than controls to more forceful forms of touch and painful stimuli, or even to chemicals that evoke itchiness, suggests light touch uses its own pathway in the nervous system to evoke scratching.

The group saw similar behaviors when they used a chemical genetic strategy to silence the NPY expressing interneurons that prevents them from communicating with the presumptive neurons that transmit this form of itch.

The fact that the NPY-deficient mice were no more sensitive than controls to more forceful forms of touch and painful stimuli, or even to chemicals that evoke itchiness, suggests light touch uses its own pathway in the nervous system to evoke scratching.

http://www.salk.edu/news/pressrelease_details.php?press_id=2128
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