Acta dermato-venereologica
-
Acta Derm. Venereol. · Jul 2013
Comparative StudyMechano-insensitive nociceptors are sufficient to induce histamine-induced itch.
The nerve fibres underlying histamine-induced itch have not been fully elucidated. We blocked the lateral femoral cutaneous nerve and mapped the skin area unresponsive to mechanical stimulation, but still sensitive to electrically induced pain. Nerve block induced significantly larger anaesthetic areas to mechanical (100 mN pin-prick, 402 ± 61 cm²; brush, 393 ± 63 cm²) and heat pain stimuli (401 ± 53 cm²) compared with electrical stimulation (352 ± 62 cm², p < 0.05), whereas the anaesthetic area tested with 260 mN (374 ± 57 cm²) did not differ significantly. ⋯ In these areas iontophoresis of histamine provoked itching in 8/9 subjects with a mean maximum of 4.6 ± 1 (on an 11-point rating scale). Histamine-induced itch can thus be perceived at skin sites where input from mechano-sensitive polymodal nociceptors is blocked. In conclusion, input from mechano-insensitive nociceptors is sufficient to generate histamine-induced itch.