The time course of CO(2) laser-evoked responses and of skin nerve fibre markers after topical capsaicin in human volunteers
(2010) Clinical Neurophysiology — Vol. 121, n° 8, p. 1256-1266 (2010)
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- OBJECTIVE: To assess the temporal relationship between skin nerve denervation and regeneration (dermal and intra-epidermal fibres, IENF) and functional changes (CO(2) laser-evoked potentials, LEPs, and quantitative sensory tests, QST) after topical cutaneous application of capsaicin. METHODS: Capsaicin (0.075%) was applied to the lateral calf for three consecutive days. QST, LEPs and skin biopsies were performed at baseline and time intervals up to 54days post-capsaicin treatment. Biopsies were immunostained with antibodies for PGP9.5, TRPV1, and GAP-43 (marker of regenerating nerve fibres), and analyzed for IENFs and dermal innervation (for GAP-43). RESULTS: At 1day post-capsaicin, cutaneous thermal sensitivity was reduced, as were LEPs. PGP9.5, TRPV1, and GAP-43 immunoreactive-nerve fibres were almost completely absent. By Day 12, LEPs had fully recovered, but PGP9.5 and TRPV1 IENF continued to be significantly decreased 54days post-capsaicin. In contrast, dermal GAP-43 immunoreactivity closely matched recovery of LEPs. CONCLUSIONS: A good correlation was observed between LEPs and GAP-43 staining, in contrast to PGP9.5 and TRPV1. Laser stimulation is a non-invasive and sensitive method for assessing the initial IENF loss, and regenerating nerve fibres. SIGNIFICANCE: Assessing skin biopsies by PGP9.5 immunostaining alone may miss significant diagnostic and prognostic information regarding regenerating nerve fibres, if other approaches are neglected, e.g. LEPs or GAP-43 immunostaining.
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Ragé, M., Van Acker, N., Facer, P., Shenoy, R., Knaapen, M. W. M., Timmers, M., Streffer, J., Anand, P., Meert, T., & Plaghki, L. (2010). The time course of CO(2) laser-evoked responses and of skin nerve fibre markers after topical capsaicin in human volunteers. Clinical Neurophysiology, 121(8), 1256-1266. https://doi.org/10.1016/j.clinph.2010.02.159 (Original work published 2010)