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Pain and itch can be transmitted by the same nervous cells

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The Séguéla lab, in collaboration with Alfredo Ribeiro da Silva, demonstrates that one subset of peripheral sensory fibers is capable of coding multiple sensations, as opposed to the common belief that peripheral fibers are specifically linked to single sensory modalities.

Sensory circuits for pain and itch

Pain is an unpleasant sensation that signals danger to our body and drives withdrawal or mitigating behaviors. Distinct yet closely related, itch is another type of aversive sensation which signals the presence of irritants on our skin and leads to scratching. Pain and itch help us in our life by detecting important stimuli to make diametrically different behavioral decisions: to scratch our skin to remove an irritant, or to withdraw our skin from a hot burning dish or a sharp object. Intriguingly, these sensations can come from the same skin area, posing the question of how our nervous system differentiates between them. It was argued that specialized nervous components are responsible for detection and transmission of distinct sensations such as pain, itch, heat, cold, etc. Yet, in the present study, QPRN neuroscientists show this might not be the case.

In their recent article published in the journal Neuron (Sharif et al., 2020), they take advantage of state-of-the-art bio-engineering techniques in mice to gain access to a small population of sensory fibers innervating the skin. Using artificial optogenetic and chemogenetic receptors, they were able to turn these neurons on by either shining blue light or injecting a specific compound. They show that the activation mode (light vs. chemical) can change the sensory information transmitted by these fibers. They further prove that in more natural conditions these neurons contribute to both pain and itch based on how they are stimulated, challenging the concept of “labeled lines” in sensory circuits.

You can find more information about this paper HERE.

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