The Peripheral Processing of Pleasant Touch in Mice
All social animals exhibit behaviors during which pleasant touch actions take place. That is also true for rodents including mice, which represent an experimental organism with genetic accessibility. Therefore, it is of great interest to study the processing of gentle touch in mice and clarify how these organisms detect and respond to such actions. Lately, a lot of advances have been made toward the peripheral processing of pleasant touch in mice. In humans, the C-Tactile (CT) fibers are believed to constitute the putative neurobiological substrate for rewarding touch processing. Whereas it was long believed that the C-Low Threshold Mechanoreceptors (C-LTMRs) in mammals represent the equivalent of the CT fibers in humans, these fibers have not been genetically identified until recently. Fortunately, several genetic markers for C-LTMRs have been identified in mice, enabling a deeper understanding of the encoding for pleasant touch in these organisms. Interestingly, a subpopulation of C-fibers that are stimulated by massage like stroking exhibit a positive valence effect when they are artificially activated and have been also identified in these experimental models. These particular fibers that do not belong in the C-LTMR family could constitute a distinct subclass of CT fibers in mice, offering another genetic handle for the elucidation of pleasant touch processing.