Hairy Sensation

Abstract

The hairs of the skin not only function to prevent heat loss but also have important sensory functions. Recent work has now established that each hair of the skin is innervated by one or more of three types of mechanoreceptor ending. Each of these three mechanoreceptor types possesses distinct molecular features and detects distinctive information about skin touch, which is relayed to specific brain locations in a somatotopic fashion.

C-tactile afferents: Cutaneous mediators of oxytocin release during affiliative tactile interactions?

“…Thus, stroking stimuli at low and intermediate velocities will preferentially activate both CTs (C-LTMs) and low threshold Aδ hair afferents. However, similar to Aβ afferent fibres that innervate hairy skin, the firing of rates of Aδ hair afferents increase with increasing velocity of the applied stimulus and do not show the classical velocity inverted-U shaped firing properties exhibited by CTs (Lechner and Lewin, 2013;Löken et al, 2009;Milenkovic et al, 2008). Furthermore, although low threshold Aδ fibres have been reported in human hairy skin their properties have not been extensively investigated and the existence of Dhairs in humans is therefore uncertain (Adriaensen et al, 1983).…”

“…D-hair afferent fibres, which are Aδ fibres with intermediate conduction velocities, are associated with down hairs of the cat and innervate all awl/auchene and zigzag hairs in rodents (Li et al, 2011). They are rapidly adapting receptors that fire in response to hair movement (Lechner and Lewin, 2013;Li et al, 2011). D-hair afferents are exquisitely sensitive to low mechanical forces and indeed respond vigorously to slow ramp stimuli, significantly more vigorously at such velocities than Aβ fibres innervating hair follicles (Brown and Iggo, 1967;Lechner and Lewin, 2013;Milenkovic et al, 2008).…”

“…They are rapidly adapting receptors that fire in response to hair movement (Lechner and Lewin, 2013;Li et al, 2011). D-hair afferents are exquisitely sensitive to low mechanical forces and indeed respond vigorously to slow ramp stimuli, significantly more vigorously at such velocities than Aβ fibres innervating hair follicles (Brown and Iggo, 1967;Lechner and Lewin, 2013;Milenkovic et al, 2008). Thus, stroking stimuli at low and intermediate velocities will preferentially activate both CTs (C-LTMs) and low threshold Aδ hair afferents.…”

KCNQ Potassium Channels Modulate Sensitivity of Skin Down-hair (D-hair) Mechanoreceptors

“…We reported previously that the KCNQ inhibitor linopirdine increased the firing rate of D-hair fibers in response to mechanical stimulation in skin-nerve preparations (23), suggesting a role of KCNQ channels in these mechanoreceptors. D-hairs are the most sensitive mechanoreceptors in the skin and are characterized by large receptive fields (31,32). According to their intermediate conduction velocity and medium cell diameter, D-hairs are classified as A␦-low-threshold mechanoreceptors (A␦-LTMR).…”

A novel vibrotactile system for stimulating the glabrous skin of awake freely behaving rats during operant conditioning

“…Four types of mechanoreceptors are found in the mammalian glabrous skin: Meissner corpuscles, Merkel's discs, Pacinian corpuscles and Ruffini endings (Gardner and Johnson, 2012;Greenspan and Bolanowski, 1996;Halata, 1990;Willis and Coggeshall, 2004). In the hairy skin, there are touch domes, Pacinian corpuscles, Ruffini endings, afferents associated with hairs, field units, and C-mechanoreceptive fibers (Halata, 1990;Lechner and Lewin, 2013;Lumpkin et al, 2010;Willis and Coggeshall, 2004). Mechanoreceptive fibers are classified according to their innervation densities, receptive-field sizes, adequate stimuli (e.g.…”