Darsow U, Ring J, Scharein E, Bromm B
Institute of Physiology, University Hospital Eppendorf, Hamburg, Germany.
Arch Dermatol Res. 1996 Jul;288(8):436-41. doi: 10.1007/BF02505231.
Correlations between the skin reactions wheal and flare and the subjectively reported degree of itch were investigated in response to 1% histamine, intradermally applied by standardized skin prick and by iontophoresis. Experiments were performed with 15 male volunteers using a threefold repeated measures design (skin prick, and iontophoresis with 0.13 mA for 10 s and with 2.0 mA for 10 s). Skin reactions (perpendicular diameters) were determined at the time of their maximum (10 min). Itch was rated on a computerized visual analogue scale which was anchored upon the individual scratch threshold. Most effective in producing itch was the skin prick which caused strong sensations markedly above the scratch threshold during the entire period of measurement (30 min), whereas iontophoresis induced only transient itch sensations. On the other hand, the largest wheals were generated by iontophoresis of both intensities (mean 10 or 14 mm vs 6 mm with skin prick). The higher current induced higher itch, wheal and flare responses, but after eliminating this effect of stimulus intensity, no correlations were found. In contrast, skin prick-induced flare reactions varied with the degree of itch above the scratch threshold (r = 0.56; P < 0.01). Repeated measurements showed a higher stability for the itch reaction with skin prick compared with iontophoresis. It is hypothesized that in iontophoresis the brief (10-s) histamine bolus passed the most superficial pruritoceptive C fibres too quickly to induce long-lasting itch sensations, whereas the skin prick caused a deposit at the dermal-epidermal junction releasing histamine during the entire time of measurement. Consequently, both the C fibre-mediated itch and the axon reflex flare were more pronounced with the skin prick, and the wheal resulting from a permeability increase in the postcapillary venule walls was an independent phenomenon.
通过标准化皮肤点刺和离子导入法皮内注射1%组胺，研究了风团和潮红等皮肤反应与主观报告的瘙痒程度之间的相关性。对15名男性志愿者进行了实验，采用三重重复测量设计（皮肤点刺、0.13 mA持续10 s和2.0 mA持续10 s的离子导入）。在皮肤反应达到最大值时（10分钟）测定其垂直直径。瘙痒程度通过计算机化视觉模拟量表进行评分，该量表以个体搔抓阈值为基准。最能引起瘙痒的是皮肤点刺，在整个测量期间（30分钟），它会引起明显高于搔抓阈值的强烈感觉，而离子导入仅引起短暂的瘙痒感觉。另一方面，两种强度的离子导入均产生了最大的风团（平均直径分别为10或14毫米，而皮肤点刺为6毫米）。较高的电流诱导出更高的瘙痒、风团和潮红反应，但在消除刺激强度的这种影响后，未发现相关性。相比之下，皮肤点刺引起的潮红反应随搔抓阈值以上的瘙痒程度而变化（r = 0.56；P < 0.01）。重复测量表明，与离子导入相比，皮肤点刺引起的瘙痒反应具有更高的稳定性。据推测，在离子导入过程中，短暂（10秒）的组胺推注过快地通过了最浅表的瘙痒感受性C纤维，无法诱导持久的瘙痒感觉，而皮肤点刺在真皮-表皮交界处产生了沉积物，在整个测量期间释放组胺。因此，皮肤点刺时C纤维介导的瘙痒和轴突反射性潮红更为明显，而毛细血管后微静脉壁通透性增加导致的风团是一种独立现象。
