A novel class of unmyelinated (C) tactile afferents in human glabrous skin

S. S. Nagi, D. A. Mahns

    Research output: Chapter in Book / Conference PaperConference Paper

    Abstract

    ![CDATA[Introduction: We recently showed that unmyelinated (C) tactile afferents in human hairy skin can contribute to the cross-over between neutral touch (vibration) and painful touch, i.e. allodynia. In the hairy skin, allodynia persisted following the blockade of myelinated afferents, whereas blockade of unmyelinated cutaneous afferents abolished allodynia. Although there is no evidence for the existence of a similar class of fibers in the glabrous skin, the ‘qualia’ of affective stimuli are comparable in hairy and glabrous skin. Methods: Detailed psychophysical observations were made in 30 healthy subjects. Sustained muscle pain was induced by infusing hypertonic saline (HS: 5%) into flexor carpi ulnaris muscle. Sinusoidal vibration (200Hz-200µm) was applied to the glabrous skin of little finger. Pain ratings were recorded using a Visual Analog Scale (VAS). Each experiment examined the impact of cutaneous vibration on muscle pain before, during and after myelinated-compression of ulnar nerve and/ or anesthesia of unmyelinated cutaneous afferents (Xylocaine 0.25%) about the vibration site. McGill pain questionnaire was used to document the quality of vibration-evoked allodynia relative to HS-pain. Results: Prior to the induction of muscle pain, all subjects reported vibration as non-painful (VAS=0). During muscle pain (VAS 4-6), vibration evoked a significant and reproducible increase in pain (allodynia) that was comparable in quality to the background HS-pain. Allodynia persisted following the blockade of myelinated afferents (compression block). In contrast, blockade of unmyelinated afferents (low-dose intradermal anesthesia) abolished allodynia. Allodynia was preserved in the adjacent non-anesthetized skin of little finger. Once the HS-induced pain disappeared, all subjects described vibration as non-painful. Conclusions: This is the first study we know that has reported a class of unmyelinated (C) tactile afferents in glabrous skin. This class of fibers may subserve an affective touch system, akin to the C-tactile fibers in hairy skin, which has immense implications for understanding sensory-perceptual abnormalities in clinical-pain states and neurological disorders.]]
    Original languageEnglish
    Title of host publicationAbstracts of the 40th Annual Meeting of the Society for Neuroscience: 13-17 November 2010, San Diego Convention Centre, California
    PublisherSociety for Neuroscience
    Number of pages1
    Publication statusPublished - 2010
    EventSociety for Neuroscience. Meeting -
    Duration: 1 Jan 2010 → …

    Conference

    ConferenceSociety for Neuroscience. Meeting
    Period1/01/10 → …

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