TY - JOUR
T1 - Capsaicin-sensitive cutaneous primary afferents convey electrically induced itch in humans
AU - Andersen, Hjalte Holm
AU - van Laarhoven, Antoinette I. M.
AU - Justesen, Frederik D.
AU - Pedersen, Jacob B.
AU - Sørensen, Laurits L
AU - Jensen, Line P.
AU - Arendt-Nielsen, Lars
PY - 2018/2/14
Y1 - 2018/2/14
N2 - Specially designed transcutaneous electrical stimulation paradigms can be used to provoke experimental itch. However, it is unclear which primary afferent fibers are activated and whether they represent pathophysiologically relevant, C-fiber mediated itch. Since low-threshold mechano-receptors have recently been implicated in pruriception we aimed to characterize the peripheral primary afferent subpopulation conveying electrically evoked itch in humans (50 Hz stimulation, 100 μs square pulses, stimulus-response function to graded stimulus intensity). In 10 healthy male volunteers a placebo-controlled, 24-h 8% topical capsaicin-induced defunctionalization of capsaicin-sensitive (transient receptor potential V1-positive, ‘TRPV1’
+) cutaneous fibers was performed. Histaminergic itch (1% solution introduced by a prick test lancet) was provoked as a positive control condition. Capsaicin pretreatment induced profound loss of warmth and heat pain sensitivity (pain threshold and supra-threshold ratings) as assessed by quantitative sensory testing, indicative of efficient TRPV1-fiber defunctionalization (all outcomes: P < 0.0001). The topical capsaicin robustly, and with similar efficaciousness, inhibited itch intensity evoked by electrical stimulation and histamine (−89 ± 4.1% and −78 ± 4.9%, respectively, both: P < 0.0001 compared to the placebo patch area). The predominant primary afferent substrate for electrically evoked itch in humans, using the presently applied stimulation paradigm, is concluded to be capsaicin-sensitive polymodal C-fibers.
AB - Specially designed transcutaneous electrical stimulation paradigms can be used to provoke experimental itch. However, it is unclear which primary afferent fibers are activated and whether they represent pathophysiologically relevant, C-fiber mediated itch. Since low-threshold mechano-receptors have recently been implicated in pruriception we aimed to characterize the peripheral primary afferent subpopulation conveying electrically evoked itch in humans (50 Hz stimulation, 100 μs square pulses, stimulus-response function to graded stimulus intensity). In 10 healthy male volunteers a placebo-controlled, 24-h 8% topical capsaicin-induced defunctionalization of capsaicin-sensitive (transient receptor potential V1-positive, ‘TRPV1’
+) cutaneous fibers was performed. Histaminergic itch (1% solution introduced by a prick test lancet) was provoked as a positive control condition. Capsaicin pretreatment induced profound loss of warmth and heat pain sensitivity (pain threshold and supra-threshold ratings) as assessed by quantitative sensory testing, indicative of efficient TRPV1-fiber defunctionalization (all outcomes: P < 0.0001). The topical capsaicin robustly, and with similar efficaciousness, inhibited itch intensity evoked by electrical stimulation and histamine (−89 ± 4.1% and −78 ± 4.9%, respectively, both: P < 0.0001 compared to the placebo patch area). The predominant primary afferent substrate for electrically evoked itch in humans, using the presently applied stimulation paradigm, is concluded to be capsaicin-sensitive polymodal C-fibers.
KW - C-Fibers
KW - Capsaicin
KW - Histamine
KW - Itch
KW - Nociceptors
KW - Pruriceptors
KW - TPRV1
UR - http://www.scopus.com/inward/record.url?scp=85041453369&partnerID=8YFLogxK
U2 - 10.1016/j.neulet.2017.11.061
DO - 10.1016/j.neulet.2017.11.061
M3 - Journal article
SN - 0304-3940
VL - 666
SP - 186
EP - 189
JO - Neuroscience Letters
JF - Neuroscience Letters
ER -