Mechanically evoked itch in humans

Un circuit impliqué dans les démangeaisons mécaniques identifié au niveau de la moelle épinière

“…Dans ce cas, aucune diminution significative de la fréquence des démangeaisons induites mécaniquement n'est observée. Le circuit des démangeai-sons mécaniques ne dépend donc pas des histamines, conformément à ce qui avait été suggéré chez l'homme [7]. Une population d'interneurones dorsaux exprimant GRPR, le récepteur au GRP (gastrin-releasing peptide), a récemment été identifiée comme intervenant dans le contrôle spinal des déman-geaisons chimiques [8][9][10] (➜).…”

Experimental elicitation of itch: Evoking and evaluation techniques

“…Physical stimuli may have the advantage of being more standardized and reproducible. Recently proposed methods include the application of electrical stimuli to the skin or vibratory mechanical stimulation [30][31][32]. Low intensity, high frequency transcutaneous electrical stimulation, using very localized electrodes, provokes intense itch without the generation of an axon reflex flare.…”

“…The mechanically elicitation of pruritus by vibratory stimulation of vellus hairs of the human face using a special probe, induces pure itch, without flare reaction or pain-related sensations and corollary symptoms, such as stinging or burning, and provide evidence of mechanosensitive nerves involved in itch. The frequency of vibration was 8 Hz, the amplitude of vibration 1.0 mm and the duration of the stimulation 90 s [32]. However, the question remains of whether this is true itch or a form of touch.…”

Updated Neurophysiology of Itch

“…In that sense, the experimental method to evoke pure itch in healthy volunteers without any pain-related components simultaneously accompanying that we have very recently reported meets the required condition and can be applied to investigate differentiation between itch and pain. 13) …”

“…61) This implicates that central sensitization is also involved in provoking alloknesis and hyperknesis. Moreover, continuous activation of c nerves by electrical stimulation and mechanical stimulation that evokes itch has reportedly induced alloknesis and hyperknesis, 8,13) suggesting that peripheral sensitization under inflammatory conditions is not always necessary for alloknesis and hyperknesis. Thus, combination of peripheral and central sensitization seems to be the explanation of itch sensitization.…”