The question of why we itch is no longer such a head-scratcher. Scientists at the National Institutes of Health (NIH) say they have isolated the gene that causes us to itch. It's called natriuretic polypeptide b, abbreviated as Nppb, and it's part of an interesting system that connects the heart to the spinal column to the brain and to every little twitch and itch on our skin.

The NIH scientists examined the Nppb molecule in mice, which have a nervous system that closely approximates the nervous system in humans. They found that the Nppb sent a signal from the heart to the spinal column, which then sent a signal to itch throughout the central nervous system. The scientists removed the Nppb gene from the mice through genetic engineering and found that the animals stopped itching whenever the scientists dosed the rodents with "a broad array of itch-inducing substances." They got the same effect when they removed the nerve cell in the spinal cord that would have received the signal from the Nppb gene. When they injected Nppb back into the mice, they started itching again.

Great news, right? Removing that gene from humans could stop the very same itching you're probably feeling just from reading this article, but that's not actually an option. Nppb has a much broader role in the heart, kidneys and several other organs, so permanently removing it could lead to a variety of health problems.

But although identifying the gene that causes itching doesn't cure itching, it does give us a few new clues into why we itch and how it could be treated in people who have chronic itching conditions, such as eczema or psoriasis. "This is a start, not a finish," senior author Mark Hoon, an NIH scientist, said this week in a press release." "Now the challenge is to find similar biocircuitry in people, evaluate what's there, and identify unique molecules that can be targeted to turn off chronic itch without causing unwanted side effects."

The research was published today in the journal Science.

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