Science News

Scratching Away at the Sensation of Itch

Tue, 19th Feb 2013

David Weston

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David - My next news item has to do with the mystery of itching.

Hannah - Itching?

David - Yes itching. So scientists have long been baffled by the physiology of itching. Itís been very hard to pin down whether itch is communicated to the brain by the same nerves that signal pain or whether they signal through their own individual nerves.

Hannah - So it was thought before that when I feel itchy, thatís because the same nerves in by body that respond to pain are being activated? Well, yes I can imagine, itching is kind of painful, but it feel very different to typical pain.

David - Yes so, previous research had shown that capsaicin, the spicy chemical in chillis, activates a set of neurons that are also activated by itchy chemicals. This led to the belief that itchy sensations must be somehow linked to painful sensations through these same nerves. But new evidence from researchers at John Hopkins University have identified a subset of itch-specific neurons.

Hannah - So these newly identified nerve cells signal to the brain the sensation of itch. How did the scientists find this out?

David - The researchers used sophisticated molecular biology to identify neurons that responded to itchy chemicals, like histamine or the anti-malarial drug chloroquine. They then showed that these neurons could also be activated by the spicy capsaicin chemical, but that this sensation, instead of being perceived as pain, by mice, was actually perceived as an itching sensation. These data indicated that there are a subset of neurons that signal itch to the brain when both itchy and fiery chemicals are around.

Hannah - So now that these itchy neurons have been identified, what can researchers do with this finding?

David - Well excessive itchy sensation can be a very unpleasant effect Man scratching back with a Backscratcherfrom conditions such as dermatitis and although these neurons might not be responsible for conveying all aspects of the itchy sensation, if we can design drugs that target them, we may be able to reduce the discomfort felt by patients.

Hannah - We might be able to scratch away at that itch without scratching using this info!



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