Thermoreceptive innervation of human glabrous and hairy skin: A contact heat evoked potential analysis

Department of Neurophysiology and Pathophysiology, University of Hamburg, Hamburg, Hamburg, Germany
Pain (Impact Factor: 5.21). 07/2005; 115(3):238-47. DOI: 10.1016/j.pain.2005.02.017
Source: PubMed


The human palm has a lower heat detection threshold and a higher heat pain threshold than hairy skin. Neurophysiological studies of monkeys suggest that glabrous skin has fewer low threshold heat nociceptors (AMH type 2) than hairy skin. Accordingly, we used a temperature-controlled contact heat evoked potential (CHEP) stimulator to excite selectively heat receptors with C fibers or Adelta-innervated AMH type 2 receptors in humans. On the dorsal hand, 51 degrees C stimulation produced painful pinprick sensations and 41 degrees C stimuli evoked warmth. On the glabrous thenar, 41 degrees C stimulation produced mild warmth and 51 degrees C evoked strong but painless heat sensations. We used CHEP responses to estimate the conduction velocities (CV) of peripheral fibers mediating these sensations. On hairy skin, 41 degrees C stimuli evoked an ultra-late potential (mean, SD; N wave latency: 455 (118) ms) mediated by C fibers (CV by regression analysis: 1.28 m/s, N=15) whereas 51 degrees C stimuli evoked a late potential (N latency: 267 (33) ms) mediated by Adelta afferents (CV by within-subject analysis: 12.9 m/s, N=6). In contrast, thenar responses to 41 and 51 degrees C were mediated by C fibers (average N wave latencies 485 (100) and 433 (73) ms, respectively; CVs 0.95-1.35 m/s by regression analysis, N=15; average CV=1.7 (0.41) m/s calculated from distal glabrous and proximal hairy skin stimulation, N=6). The exploratory range of the human and monkey palm is enhanced by the abundance of low threshold, C-innervated heat receptors and the paucity of low threshold AMH type 2 heat nociceptors.

Download full-text


Available from: Kenneth Casey
  • Source
    • "The distinct impact of chronic stress on mast cells from glabrous and hairy skin may be explained by the different pattern of innervation [44–46] regarding both the myelinated nerve fibers [47] and the unmyelinated nociceptive nerve fibers [48]. Moreover, different functional features of Aδ and C nerve fibers innervating the human glabrous and hairy skin have been previously reported [49]. Unmyelinated type C and thin myelinated type Aδ nerve fibers are rich in various neuropeptides, such as SP and CGRP, and, together with mast cells, are key players in cutaneous neurogenic inflammation [50–52]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Mast cells play a key role in modulation of stress-induced cutaneous inflammation. In this study we investigate the impact of repeated exposure to stress on mast cell degranulation, in both hairy and glabrous skin. Adult male Wistar rats were randomly divided into four groups: Stress 1 day (n = 8), Stress 10 days (n = 7), Stress 21 days (n = 6), and Control (n = 8). Rats in the stress groups were subjected to 2 h/day restraint stress. Subsequently, glabrous and hairy skin samples from animals of all groups were collected to assess mast cell degranulation by histochemistry and transmission electron microscopy. The impact of stress on mast cell degranulation was different depending on the type of skin and duration of stress exposure. Short-term stress exposure induced an amplification of mast cell degranulation in hairy skin that was maintained after prolonged exposure to stress. In glabrous skin, even though acute stress exposure had a profound stimulating effect on mast cell degranulation, it diminished progressively with long-term exposure to stress. The results of our study reinforce the view that mast cells are active players in modulating skin responses to stress and contribute to further understanding of pathophysiological mechanisms involved in stress-induced initiation or exacerbation of cutaneous inflammatory processes.
    Full-text · Article · May 2014 · Mediators of Inflammation
  • Source
    • "This motivated us to use magnetoencephalography (MEG) to assess the cortical activation elicited by this stimulation. There are previous electroencephalography and MEG studies of cortical activation following C-fiber stimulation by lasers [17] [18] [19] [20] [21], contact heat [22] [23] and brush stroke [24]. In the present study, we investigated whether stable cortical responses to C-fiber stimulation similar to those reported in previous studies could be obtained by IES. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Intra-epidermal electric stimulation (IES) is an alternative to laser stimulation for selective activation of cutaneous Aδ-fibers. IES is based on the fact that nociceptive fiber terminals are located in the epidermis, whereas receptors of other fibers end deep in the dermis. IES can selectively stimulate C-fibers if the electrode structure and stimulation parameters are carefully selected. However, stable selective stimulation of C-fibers using IES has proven difficult and cannot currently be used in clinical settings. The purpose of the present study was to determine if IES performed using a modified electrode reliably stimulates C-fibers. Magnetoencephalographic responses to IES to the foot were measured in seven healthy subjects. IES elicited somatosensory evoked fields in all subjects. The mean peak latency was 1327±116ms in the opercular region contralateral to the stimulated side, 1318±90ms in the opercular region ipsilateral to the stimulated side, and 1350±139ms in the primary somatosensory cortex. These results indicate that IES performed using the modified electrode can selectively stimulate C-fibers and may be a useful tool for pain research as well as clinical evaluation of peripheral small fiber function.
    Full-text · Article · Apr 2014 · Neuroscience Letters
  • Source
    • "SEPs induced by noxious laser stimulation (heat) consist of a negative-positive (NP) biphasic wave in the 160–390 ms latency range (Mouraux and Plaghki, 2007), indicating Aδ-fibre activation. Ultra-late evoked potentials (approximately 750–1100 ms; Tran et al., 2001), associated with the activation of C-fibres (Granovsky et al., 2005), can be elicited by the means of non-painful warm laser stimulations. Thus, since each type of fibre conveys specific types of sensory messages (i.e., induced by specific types of stimuli), we would be able to compare the effects of age on myelinated and unmyelinated fibres by comparing young and old adults' somatosensory and pain perception and SEPs as a function of the type of stimulation. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Experimental data regarding age effects on sensitivity and pain thresholds are not always consistent, with the type of stimulus being a major source of variability. This could suggest that some types of peripheral sensory fibres undergo more important modifications with age than others. We investigated whether ageing affects differently myelinated and unmyelinated fibres. Somatosensitivity and pain perception and recorded somatosensory evoked potentials (SEPs) were assessed in younger and older adults during the selective activation of either myelinated Aδ- or unmyelinated C-fibres. Somatosensitivity for information transmitted and SEPs elicited by stimulation of C-fibres did not differ between both groups. In contrast, pain perception was lower in older than in younger adults, and older adults showed longer SEP latencies and reduced peak-to-peak amplitude, during selective stimulation of Aδ-fibres. These findings suggest that myelinated Aδ-fibres are compromised by the normal ageing process, whereas unmyelinated C-fibres seem to remain unaltered or, at least, less affected.
    Full-text · Article · Apr 2014 · European journal of pain (London, England)
Show more