Grossmann Lydia, Gorodetskaya Natalia, Teliban Alina, Baron Ralf, Jänig Wilfrid
Physiologisches Institut, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel, Germany.
Eur J Pain. 2009 Aug;13(7):682-90. doi: 10.1016/j.ejpain.2008.09.004. Epub 2008 Oct 30.
Cutaneous C-fiber afferents show two distinct types of cold sensitivity corresponding to non-noxious and noxious cold sensations. Here, responses to cold stimulation of afferent fibers regenerating in the rat sural nerve were studied in vivo 7-14 days after nerve crush and compared with responses to mechanical and heat stimulation. The physiological stimuli were applied to the sural nerve at or distal to the lesion site. Ectopic activity was evoked in 43% of 98 A-fibers (all mechanosensitive; a few additionally weakly thermosensitive). Ectopic activity was evoked in 127 (49.2%) of 258 electrically identified C-fibers by the physiological stimuli. Eight C-fibers were spontaneously active only. Of the 127 C-fibers, 46% had one of two distinct response patterns to cooling: (1) type 1 cold-sensitive C-fibers (n=29) had a high rate of activity at 28 degrees C on the nerve surface and showed graded responses to cooling with maximal discharge rates of 11.5+/-1.1 imp/s. This activity was completely inhibited by heating, while 12/29 fibers were also excited at high threshold (median 48 degrees C) by heating. Only one type 1 cold-sensitive C-fiber was mechanosensitive. (2) Type 2 cold-sensitive C-fibers (n=29) were silent or showed a low rate of activity at 28 degrees C, had a high threshold (median 5 degrees C) and low maximal discharge rates (2.4+/-0.4 imp/s) to cooling. They were also heat-sensitive (n=25) and/or mechanosensitive (n=20). These C-fibers were, apart from their cold sensitivity, functionally indistinguishable from C-fibers with mechano- and/or heat sensitivity only. Thus regenerating cutaneous C-fibers show two types of cold sensitivity similar to those observed in intact skin: fibers of one group are predominantly sensitive to cooling, whereas the others are polymodal.
皮肤C纤维传入神经表现出两种不同类型的冷敏感性，分别对应非伤害性和伤害性冷觉。在此，研究了大鼠腓肠神经损伤后7 - 14天在体再生的传入纤维对冷刺激的反应，并与对机械刺激和热刺激的反应进行比较。生理刺激施加于损伤部位或其远端的腓肠神经。在98条A纤维中有43%（均为机械敏感型；少数还具有微弱的热敏感性）诱发出异位活动。在258条经电鉴定的C纤维中有127条（49.2%）通过生理刺激诱发出异位活动。8条C纤维仅表现出自发活动。在这127条C纤维中，46%对冷却有两种不同反应模式之一：（1）1型冷敏感C纤维（n = 29）在神经表面28℃时具有高活动率，对冷却表现出分级反应，最大放电率为11.5±1.1次/秒。这种活动被加热完全抑制，而29条纤维中有12条在高阈值（中位数48℃）时也被加热兴奋。仅1条1型冷敏感C纤维是机械敏感的。（2）2型冷敏感C纤维（n = 29）在28℃时无活动或活动率低，对冷却具有高阈值（中位数5℃）和低最大放电率（2.4±0.4次/秒）。它们也是热敏感的（n = 25）和/或机械敏感的（n = 20）。这些C纤维除了冷敏感性外，在功能上与仅具有机械和/或热敏感性的C纤维无法区分。因此，再生的皮肤C纤维表现出两种类型的冷敏感性，类似于在完整皮肤中观察到的：一组纤维主要对冷却敏感，而另一组是多模式的。
