The Functional Organization of Cutaneous Low-Threshold Mechanosensory Neurons

SummaryInnocuous touch of the skin is detected by distinct populations of neurons, the low-threshold mechanoreceptors (LTMRs), which are classified as Aβ-, Aδ-, and C-LTMRs. Here, we report genetic labeling of LTMR subtypes and visualization of their relative patterns of axonal endings in hairy skin and the spinal cord. We found that each of the three major hair follicle types of trunk hairy skin (guard, awl/auchene, and zigzag hairs) is innervated by a unique and invariant combination of LTMRs; thus, each hair follicle type is a functionally distinct mechanosensory end organ. Moreover, the central projections of Aβ-, Aδ-, and C-LTMRs that innervate the same or adjacent hair follicles form narrow LTMR columns in the dorsal horn. These findings support a model of mechanosensation in which the activities of Aβ-, Aδ-, and C-LTMRs are integrated within dorsal horn LTMR columns and processed into outputs that underlie the perception of myriad touch sensations.PaperClip To listen to this audio, enable JavaScript on your browser. However, you can download and play the audio by clicking on the icon belowHelp with MP3 filesOptionsDownload audio (2754 K)

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (383 K)Download as PowerPoint slideHighlights► Genetic labeling reveals low-threshold mechanoreceptor circuitry in the mouse ► Low-threshold mechanoreceptors innervate hair follicles and form lanceolate endings ► Each hair follicle type displays a unique combination of mechanoreceptor endings ► Central endings of mechanoreceptors form columns in the spinal cord dorsal horn