Scientists have discovered a substance in the central nervous system called natriuretic polypeptide b (Nppb) that is responsible for transmitting the sensation of itching from the skin to the brain, The Independent reported.
In the study, mice were genetically modified to lack the gene that makes the Nppb protein. The mice did not respond to itchy sensations but also did not lose the ability to feel any other sensations.
"We tested Nppb for its possible role in various sensations without success. When we exposed the Nppb-deficient mice to several itch-inducing substances, it was amazing to watch. Nothing happened. The mice wouldn't scratch," said Santosh Mishra, a researcher at the US National Institute of Dental and Craniofacial Research in Washington DC.
This discovery could mean new breakthroughs in anti-itch treatments for humans. Scientists once thought that itching was a low level of pain, the discovery of this protein suggests that itching is its own sensation that operates on its own neurotransmitter, a molecule that transmits signals between nerve cells.
"We can see the differences between the sensation of pain and of itch in a laboratory mouse, which will scratch itself if it feels an itch but lick itself, gnaw at its skin or flinch at a painful stimulus," said Dr. Mark Hoon, a lead investigator at the US National Institute of Dental and Craniofacial Research.
Scientists believe that the neurotransmitter plays an important role in the way itching is perceived, and can be responsible for chronic itchy sensations and scratching.
When the transmitter is removed the sensation of itching also goes away. The researchers also found several nerve fibres in the spine that responded to the Nppb neurotransmitter. When these fibres were removed the itching also stopped.
"Overall, a better understanding of the biology of itch and the molecules involved can only mean we are closer to finding a treatment for chronic itching. Most people think of an itch as an inconvenience, but there are patients who have a poor quality of life because of chronic scratching," Dr. Hoon said.
Patients suffering from conditions such as psoriasis and eczema often have chronic itching that interferes with their quality of life. Some patients have even scratched their skin until it bled, this study may be the first step towards the solution to the itch.
"Now the challenge is to find similar biocircuitry in people, evaluate what's there and to identify molecules that can be targeted to turn off chronic itch without causing unwanted side-effects," Dr. Hoon said.