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Bradykinin is a potent pruritogen in atopic dermatitis: A switch from pain to itch

2006; Lippincott Williams & Wilkins; Volume: 126; Issue: 1 Linguagem: Inglês

10.1016/j.pain.2006.06.003

1872-6623

Miwa Hosogi, Martin Schmelz, Yoshiki Miyachi, Akihiko Ikoma,

Contact Dermatitis and Allergies

Histamine, substance P, serotonin and bradykinin were applied by iontophoresis to lesional and visually non-lesional skin of 14 patients with atopic dermatitis, and normal skin of 15 healthy volunteers. Itch could be evoked by light stroking of skin with a cotton swab (alloknesis) in all lesional skin sites, but not in non-lesional or normal skin. Substances were applied in the same skin area before and 3 h after administration of placebo or antihistamine (olopatadine hydrochloride: H1-receptor-blocker). Intensities of itch and pain sensation and areas of flare and wheal were measured. All the substances induced significantly more intense itch in lesional skin than in non-lesional skin of patients. Even bradykinin, which evoked only weak itch and pain of similar intensities in non-lesional skin of patients and in healthy volunteers, induced intense itch in lesional skin, while the simultaneously increased pain did not suppress the itch sensation, indicating central sensitization. Histamine- and substance P-induced itch was almost completely suppressed by antihistamines, whereas bradykinin- and serotonin-induced itch was not. This suggests that substance P is a histamine-dependent pruritogen also in lesional skin under sensitized conditions but that bradykinin and serotonin are histamine-independent pruritogens in lesional skin. It is concluded that serotonin and bradykinin, classic endogenous algogens, can turn into potent histamine-independent pruritogens in lesional skin of atopic dermatitis.