Laser-evoked potentials mediated by mechano-insensitive nociceptors in human skin

M. Dusch, J. van der Ham, B. Weinkauf, J. Benrath, R. Rukwied, Matthias Ringkamp, M. Schmelz, R. D. Treede, U. Baumgärtner

Research output: Contribution to journalArticle

Abstract

Objectives: Laser-evoked potentials (LEP) were assessed after peripheral nerve block of the lateral femoral cutaneous nerve (LFCN) in healthy volunteers from partially anesthetized skin areas to differentially stimulate mechano-insensitive nociceptors. Methods: An ultrasound-guided nerve block of the LFCN was performed in 12 healthy male subjects with Ropivacain 1%. After 30 min, the nerve block induced significantly larger anesthetic areas to mechanical stimuli than to electrical stimuli revealing an area of differential sensitivity. LEPs, reaction times and pain ratings were recorded in response to the laser stimuli of (1) completely anesthetic skin, (2) mechano-insensitive, but electrically excitable skin ('differential sensitivity'), (3) normal skin. Results: LEP latencies in the area of differential sensitivity were increased compared to unaffected skin (228 ± 8.5 ms, vs. 181 ± 3.6 ms, p <0.01) and LEP amplitudes were reduced (14.8 ± 1.2 μV vs. 24.6 ± 1.7 μV, p <0.01). Correspondingly, psychophysically assessed response latencies in the differentially anesthetic skin were increased (649 ms vs. 427 ms, p <0.01) and pain ratings reduced (1.5/10 vs. 5/10 NRS, p <0.01). Conclusion: The increase in LEP latency suggests that mechano-insensitive heat-sensitive Aδ nociceptors (MIA, type II) have a slower conduction velocity or higher utilization time than mechano-sensitive type II Aδ nociceptors. Moreover, widely branched, slowly conducting and mechano-insensitive branches of Aδ nociceptors can explain our finding. LEPs in the differentially anesthetized skin provide specific information about a mechanically insensitive but heat-sensitive subpopulation of Aδ nociceptors. These findings support the concept that A-fibre nociceptors exhibit a similar degree of modality specificity as C-fibre nociceptors.

Original languageEnglish (US)
JournalEuropean Journal of Pain (United Kingdom)
DOIs
StateAccepted/In press - 2015

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Nociceptors
Skin
Nerve Block
Femoral Nerve
Anesthetics
Reaction Time
Healthy Volunteers
Hot Temperature
Laser-Evoked Potentials
Myelinated Nerve Fibers
Pain
Unmyelinated Nerve Fibers
Peripheral Nerves
Lasers

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

Cite this

Dusch, M., van der Ham, J., Weinkauf, B., Benrath, J., Rukwied, R., Ringkamp, M., ... Baumgärtner, U. (Accepted/In press). Laser-evoked potentials mediated by mechano-insensitive nociceptors in human skin. European Journal of Pain (United Kingdom). https://doi.org/10.1002/ejp.810

Laser-evoked potentials mediated by mechano-insensitive nociceptors in human skin. / Dusch, M.; van der Ham, J.; Weinkauf, B.; Benrath, J.; Rukwied, R.; Ringkamp, Matthias; Schmelz, M.; Treede, R. D.; Baumgärtner, U.

In: European Journal of Pain (United Kingdom), 2015.

Research output: Contribution to journalArticle

Dusch, M, van der Ham, J, Weinkauf, B, Benrath, J, Rukwied, R, Ringkamp, M, Schmelz, M, Treede, RD & Baumgärtner, U 2015, 'Laser-evoked potentials mediated by mechano-insensitive nociceptors in human skin', European Journal of Pain (United Kingdom). https://doi.org/10.1002/ejp.810
Dusch, M. ; van der Ham, J. ; Weinkauf, B. ; Benrath, J. ; Rukwied, R. ; Ringkamp, Matthias ; Schmelz, M. ; Treede, R. D. ; Baumgärtner, U. / Laser-evoked potentials mediated by mechano-insensitive nociceptors in human skin. In: European Journal of Pain (United Kingdom). 2015.
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abstract = "Objectives: Laser-evoked potentials (LEP) were assessed after peripheral nerve block of the lateral femoral cutaneous nerve (LFCN) in healthy volunteers from partially anesthetized skin areas to differentially stimulate mechano-insensitive nociceptors. Methods: An ultrasound-guided nerve block of the LFCN was performed in 12 healthy male subjects with Ropivacain 1{\%}. After 30 min, the nerve block induced significantly larger anesthetic areas to mechanical stimuli than to electrical stimuli revealing an area of differential sensitivity. LEPs, reaction times and pain ratings were recorded in response to the laser stimuli of (1) completely anesthetic skin, (2) mechano-insensitive, but electrically excitable skin ('differential sensitivity'), (3) normal skin. Results: LEP latencies in the area of differential sensitivity were increased compared to unaffected skin (228 ± 8.5 ms, vs. 181 ± 3.6 ms, p <0.01) and LEP amplitudes were reduced (14.8 ± 1.2 μV vs. 24.6 ± 1.7 μV, p <0.01). Correspondingly, psychophysically assessed response latencies in the differentially anesthetic skin were increased (649 ms vs. 427 ms, p <0.01) and pain ratings reduced (1.5/10 vs. 5/10 NRS, p <0.01). Conclusion: The increase in LEP latency suggests that mechano-insensitive heat-sensitive Aδ nociceptors (MIA, type II) have a slower conduction velocity or higher utilization time than mechano-sensitive type II Aδ nociceptors. Moreover, widely branched, slowly conducting and mechano-insensitive branches of Aδ nociceptors can explain our finding. LEPs in the differentially anesthetized skin provide specific information about a mechanically insensitive but heat-sensitive subpopulation of Aδ nociceptors. These findings support the concept that A-fibre nociceptors exhibit a similar degree of modality specificity as C-fibre nociceptors.",
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AU - Rukwied, R.

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