Activity-dependent slowing properties of an unmyelinated low threshold mechanoreceptor in human hairy skin

• Published in: Neuroscience letters Vol. 493; no. 3; pp. 92 - 96
• Main Authors: Campero, Mario, Bostock, Hugh, Baumann, Thomas K., Ochoa, José L.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 15.04.2011; Elsevier
• Subjects: Action Potentials - physiology; Biological and medical sciences; Female; Fundamental and applied biological sciences. Psychology; Hair Follicle - physiology; Humans; Low threshold mechanoreceptors; Mechanoreceptors - physiology; Microneurography; Middle Aged; Mononeuropathies - physiopathology; Nerve Fibers, Unmyelinated - physiology; Neural Conduction - physiology; Peroneal Nerve - physiology; Unmyelinated fibres; Vertebrates: nervous system and sense organs; Low threshold mechanoreceptors; Unmyelinated fibres; Microneurography; Human; Skin; Mechanoreceptor
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2011.02.012

► Different profiles of activity-dependent slowing of C fibres have been identified. ► Each profile correlates with a functional modality. ► The function of fibres with the least activity-dependent has not been yet identified. ► We describe one such a profile corresponding to a low threshold, tactile C fibre. It has been previously shown that unmyelinated afferent fibres in human skin are differentiated not only by their receptor characteristics, but also by their profiles of activity-dependent slowing. One type of profile, described originally as ‘type 3’, is different from that of nociceptors (type 1), cold afferents (type 2) and sympathetic efferents (type 4), in that these fibres display a minimal activity-dependent slowing (∼1% at 2 Hz). However, their function remains to be determined. Here we describe one unit with a typical ‘type 3’ activity-dependent slowing profile recorded from an undamaged fascicle of the superficial peroneal nerve of a patient. Its conduction velocity was 1.8 m s −1 and it slowed by 1.3% during the 2 Hz tetanus. This unit had a mechanical receptive field in the hairy skin and responded readily to weak mechanical stimuli, and not to cold. This suggests that the low threshold unmyelinated mechanoreceptors recently described in human hairy skin are probably endowed with a ‘type 3’ activity-dependent profile.