image: Schematic diagram of mechanisms underlying itch relief by stroking skin. Rubbing or stroking of the skin activates vesicular glutamate transporter 3+-low threshold mechanoreceptors (VGLUT3+-LTMRs; red), followed by excitation of itch inhibitory interneurons (blue) in the superficial dorsal horn. The inhibitory interneurons use dynorphin as a neurotransmitter to inhibit pruritogen-responsive neurons (green). view more
Credit: Sakai et al., JNeurosci 2020
Stop scratching: rubbing skin activates an anti-itch pathway in the spinal cord, according to research in mice recently published in JNeurosci.
It can be hard to resist the relief of scratching an itch, even though scratching damages skin, especially in sensitive areas like the eyes. But stroking can relieve an itch, too. Sakai et al. investigated the neural pathway behind this less-damaging form of itch relief.
The research team triggered the urge to scratch in mice by administering an itch-inducing chemical underneath their skin. The team then recorded the electrical response from dorsal horn neurons in the spinal cord while they stroked the animals' paws. The neurons fired more often as the mice were stroked and less often after the stroking ended. These neurons respond to both touch and itch, so the increase corresponds to the added touch, not increased itchiness, while the decrease corresponds to itch relief. The same decrease could be seen when the team directly stimulated touch-sensing neurons under the skin. However, inhibiting both sensory neurons and a subtype of anti-itch interneurons in the spinal cord failed to decrease the response from dorsal horn neurons, while activating sensory neurons stopped the mice from scratching. The results show that stroking sets off a cascade, activating sensory neurons under the skin that then activate anti-itch interneurons in the spinal cord, resulting in reduced dorsal horn neural activity and itch relief.
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Manuscript title: Low-Threshold Mechanosensitive VGLUT3-Lineage Sensory Neurons Mediate Spinal Inhibition of Itch by Touch
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About JNeurosci
JNeurosci, the Society for Neuroscience's first journal, was launched in 1981 as a means to communicate the findings of the highest quality neuroscience research to the growing field. Today, the journal remains committed to publishing cutting-edge neuroscience that will have an immediate and lasting scientific impact, while responding to authors' changing publishing needs, representing breadth of the field and diversity in authorship.
About The Society for Neuroscience
The Society for Neuroscience is the world's largest organization of scientists and physicians devoted to understanding the brain and nervous system. The nonprofit organization, founded in 1969, now has nearly 37,000 members in more than 90 countries and over 130 chapters worldwide.