Nakano Tasuku, Andoh Tsugunobu, Sasaki Atsushi, Nojima Hiroshi, Kuraishi Yasushi
Department of Applied Pharmacology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
Acta Derm Venereol. 2008;88(5):449-54. doi: 10.2340/00015555-0479.
Although mosquito allergy induces the release of histamine, the itch-related response, scratching, is not effectively suppressed by blockade of H1 histamine receptors. To address this question, we examined the effects of neonatal capsaicin treatment on allergic reactions and H1 histamine receptor-expressing sensory neurones in mice. Neonatal capsaicin treatment almost completely abolished allergy-associated scratching, without effects on plasma extravasation or increase in serum concentrations of immunoglobulins E and G1. An injection of edema contents from an animal exhibiting allergic reaction elicited scratching in naive animals, suggesting the production of pruritogen(s) by allergic reaction; this production was not suppressed by neonatal capsaicin treatment. This treatment markedly decreased the number of sensory neurones immunoreactive for TRPV1 capsaicin receptor, with little effect on sensory neurones immunoreactive for neurofilament 200, a marker of myelinated A-fibre neurones. In addition, there was a trend towards a reduction in numbers of sensory neurones immunoreactive for H1 histamine receptor. The results suggest that capsaicin-sensitive sensory neurones that lack H1 histamine receptors play a key role in signalling of allergic itch.
尽管蚊虫过敏会诱导组胺释放，即与瘙痒相关的反应，但组胺H1受体的阻断并不能有效抑制抓挠行为。为了解决这个问题，我们研究了新生小鼠辣椒素处理对过敏反应以及表达组胺H1受体的感觉神经元的影响。新生小鼠辣椒素处理几乎完全消除了与过敏相关的抓挠行为，对血浆外渗或血清中免疫球蛋白E和G1浓度的升高没有影响。注射来自表现出过敏反应动物的水肿液会引起未致敏动物的抓挠，这表明过敏反应会产生致痒原；新生小鼠辣椒素处理并不能抑制这种致痒原的产生。这种处理显著减少了对辣椒素受体TRPV1免疫反应的感觉神经元数量，而对有髓鞘A纤维神经元的标志物神经丝200免疫反应的感觉神经元影响很小。此外，对组胺H1受体免疫反应的感觉神经元数量有减少的趋势。结果表明，缺乏组胺H1受体的对辣椒素敏感的感觉神经元在过敏性瘙痒信号传导中起关键作用。
