Feel-Good C Fibers
A paper in the January 31 Nature reports the discovery of a population of sensory neurons that specifically responds to massage-like stroking in mice. The work, from David Anderson and colleagues at the California Institute of Technology in Pasadena, US, shows that, alongside fibers that sense unpleasant stimuli, some C fibers are attuned to pleasurable inputs.
The neurons, characterized by expression of the Mas-related G protein-coupled receptor Mrgprb4, innervate only hairy skin, and the new study shows they respond to stroking, but not pinching or poking. Behavioral tests suggest that stimulation of the neurons elicited pleasurable or calming feelings—in a conditioned place preference experiment, juvenile mice spent more time in a chamber that they associated with chemical activation of the Mrgprb4-expressing cells.
The researchers write the findings are “the first example of a genetically identified population of C fibers whose functional activation has a positive rather than negative behavioral valence.”
The discovery comes on the heels of evidence that a different subset of C fibers marked by expression of another MRG family protein, MrgprA3, specifically signal itch (see related PRF news story).
The neurons may explain why animals get pleasure from being petted or groomed, as explained in a video (below) supplied by Nature. But despite the abundance of cute felines in the clip, whether comparable cells exist in cats or other animals, or people, remains to be determined.
Video Credit: Nature Video. Top image credit: D. Anderson lab, Caltech.
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