An Itchy Situation

The whole process of itchiness is actually quite mysterious and not all understood. And even though the subject seems light, it isn't.

Just think about how uncomfortable it is to get a mosquito bite, but having that itch go on with no relief. It's torturous and something millions of Americans with long-term itch endure.

Here's what we've known about the itch sensation: Neurons called TRPV1 cells detect itchy substances on the skin. But they also detect pain and heat, so scientists didn't know if the itch sensation was just a lower form of pain rather than a unique sense on its own.

That's why developing a therapy around TRPV1 cells has been tricky because scientists would have to be careful not to affect other sensations. Plus, we just didn't fully understand the whole process.

Now, a new study has identified a molecule that is uniquely responsible for itch. Researchers did this by looking for something in the TRPV1 neuron that was itch-specific. They found it in a small group of these neurons that were producing a natriuretic polypeptide b or Nppb.

Nppb is a hormone we've known the heart muscle to produce for regulating itself. So, it was surprising to learn TRPV1 also produce Nppb, and that the hormone was acting as a neurotransmitter to relay messages between neurons; in this case, the itch stimuli.

Researchers discovered this by genetically engineering mice that lacked Nppb. These mice did not itch when they were given itch-inducing compounds, proving that Nppb is required for mice to itch. The mice also didn't have other sensory deficits from the missing neurotransmitter.

This new information is valuable to researchers trying to come up with a therapy to help people debilitated by chronic itch.