The ghastly feeling of a bug crawling on your leg likely invokes an instant swoosh of the hand to knock the critter flying. It’s the insect’s disturbance of tiny hairs on the skin that signals the sensation – known as mechanical itch. But, how these signals are transmitted as well as suppressed – so that a person doesn’t scratch uncontrollably at the slightest sensation – was a bit of a mystery. Studies in mice have now revealed that signals arising from the skin’s sensory neurons (green) are kept in check by particular inhibitory interneurons (red). When the activity of these inhibitory cells was specifically blocked in mice, the animals started scratching compulsively. The animals’ responses to chemical irritants or pain, however, was unchanged suggesting the interneurons are specifically involved in regulating mechanical itch. This discovery could ultimately lead to ways to calm the incessant urge to scratch in patients with chronic itch.
Written by Ruth Williams
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