Specific C-Receptors for Itch in Human Skin
Specific C-Receptors for Itch in Human Skin
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DOI：
10.1523/jneurosci.17-20-08003.1997
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发表时间：
1997-10
期刊：
影响因子：
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通讯作者：
M. Schmelz;R. Schmidt;A. Bickel;H. Handwerker;H. E. Torebjörk
中科院分区：
文献类型：
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作者：
M. Schmelz;R. Schmidt;A. Bickel;H. Handwerker;H. E. Torebjörk
在显微神经造影实验中，研究了56根健康志愿者腓神经皮分支中的无髓神经纤维。使用“标记”技术将装置识别为机械和热响应（CMH; n = 30）、热响应（CH; n = 13）或对机械和热刺激无响应（CMiHi;n = 13）。所有装置均未显示自发活动。测试这些单元对来自小探针（直径，6 mm）的组胺离子电渗（1 mA，20秒）的响应性，其诱导持续数分钟的瘙痒感觉。23个单位对组胺无反应，25个单位在离子导入后反应较弱，有几个尖峰放电。然而，八个单位对组胺产生持续放电反应，并且它们的放电模式与瘙痒感觉的时间过程相匹配。该组中的所有C-单位都是机械不敏感的，其中5个是热响应的。他们有非常低的传导速度只有0.5米/秒，平均而言，这是显着低于传导速度的“多模态”CMH单位。这种缓慢的传导速度归因于小的轴突直径可能是这些单位在以前的研究中没有遇到的原因之一。组胺敏感的C-单位有非常大的神经支配领域延伸到直径85毫米的小腿。我们的结论是，这些C-纤维代表了一类新的传入神经纤维，特别薄的轴突，但过多的终端分支。这种类型的C纤维可能代表了长期以来寻找的介导瘙痒感觉的传入单位。
In microneurography experiments 56 unmyelinated nerve fibers were studied in the cutaneous branch of the peroneal nerve of healthy volunteers. Units were identified with the “marking” technique as mechanically and heat-responsive (CMH; n = 30), heat-responsive (CH; n = 13), or unresponsive to mechanical and heat stimulation (CMiHi;n = 13). None of the units showed spontaneous activity. These units were tested for responsiveness to iontophoresis of histamine (1 mA, 20 sec) from a small probe (diameter, 6 mm), which induced itch sensations lasting several minutes. Twenty-three units were unresponsive to histamine, and 25 units responded weakly with a few spike discharges after iontophoresis. Eight units, however, responded with sustained discharges to histamine, and their discharge patterns were matching the time course of the itch sensations. All C-units in this group were mechanically insensitive, and five of them were heat-responsive. They had very low conduction velocities of only 0.5 m/sec, on average, which is significantly lower than conduction velocities of the “polymodal” CMH units. This slow conduction velocities attributable to small axon diameters may be one reason why these units have not been encountered in previous studies. Histamine-sensitive C-units had very large innervation territories extending up to a diameter of 85 mm on the lower leg. We conclude that these C-fibers represent a new class of afferent nerve fibers with particularly thin axons but excessive terminal branching. This type of C-fiber probably represents the afferent units long searched for mediating itch sensations.