Who Knew? A Neural Circuit Just for Itching
Posted on by Dr. Francis Collins
Itch-inducing agents activate a discrete population of peripheral sensory neurons that produce a signaling molecule called natriuretic polypeptide b (Nppb). The release of Nppb from these primary pruriceptive neurons triggers a dedicated itch biocircuit to generate the sensation of itch. [Images courtesy of Mark Hoon, National Institute of Dental and Craniofacial Research, NIH]
Until now, it’s been unclear how the sensation of itching was carried to the brain. Was this a separate system, or did it use the same nerve pathways as pain, touch, or temperature? To find out, the researchers focused on a special group of nerve cells called “TRPV1 neurons,” which extend to the skin and detect temperature, various types of pain, and itch. These neurons use several chemicals to transmit signals; one of those is a neurotransmitter called Nppb. When the researchers created mice lacking Nppb, the mice became immune to itching. Even when the researchers exposed the mice to several itchy substances, such as histamine, the mice refused to scratch!
When the researchers actually removed specific spinal cord nerves that receive the Nppb itch signals, other sensations—like pain, touch, and temperature—remained intact. So we now know that in mice, and possibly in humans, there are specific nerve cells and brain circuitry that are entirely devoted to that itchy feeling. That means blocking Nppb could turn out to be a safe and effective strategy to cure itching, especially in chronic cases.
Reference:
[1] The cells and circuitry for itch responses in mice. Mishra SK, Hoon MA. Science. 2013 May 24;340(6135):968-71.
NIH support: National Institute of Dental and Craniofacial Research
Amy,
In our experiments on laboratory mice we could block itch by simple chemical interventions. The key molecule that we discovered in our work, Nppb, also has a major role in controlling blood pressure. Thus although it is tempting to speculate that blocking it would alleviate itch, it might have side-effect that are dangerous. Therefore we think this is the beginning of seeing if Nppb or other molecules will be safe and effective for treating chronic itch in people.
Getting rid of the itch is great. Patients with CTCL (cutneous t-cell lymphoma) with severe itching can also have redness, rash, plaques, flaking, etc.. If the itch was stopped, would the inflammation also be stopped in ctcl patients?
Great research! It is amazing to think that science
is able to produce such knowledge of the body!
Cheers!
I will have eczema all my life until the day I die. I will do anything to stop the itch, if it works great! That will mean no more creams etc. no more coal tar! To live a day, a minute without itching means for me that I can have a real life again! Until then, I will keep hope in my heart, and mind, and prayer too.
I was diagnosed with eczema when I was a young child and it’s a pain to live with. However, I noticed when I visited hot countries like India or America, the itching isn’t as bad and no eczema flare ups. I came back to the UK and started taking vitamin D3, as I assumed I may be lacking vitamin D due to the UK’s weather climate. I have found it to work after a month or so — I still itch occasionally, but not as much … This research does sound interesting …
Very interesting study. I’m very interested in health research and love reading studies like these.
Great post!
Finally, there is some hope to come!
Truly great information, however any medications developed from this will mostly be priced well beyond the common persons ability to afford it and not covered by insurance/Rx plans. Much like the now available Jaks inhibitors.
Are there lotions, medications to use to alleviate this if you can’t identify the source? Does a low histamine diet work? Is NIH doing any studies presently that I can be part of? Capsaicin, Cerave lotion and Clobatesol mix (recommended by dermatologist) are not a bad combination, but wears off after 1-2 hrs.