Characterization of Adelta- and C-fibers innervating the plantar rat hindpaw one day after an incision.
Characterization of Adelta- and C-fibers innervating the plantar rat hindpaw one day after an incision.
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DOI：
10.1046/j.1529-8027.2002.02026_26.x
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发表时间：
2002-02
影响因子：
2.5
通讯作者：
EM Pogatzki;GF Gebhart;Tj. Brennan
中科院分区：
文献类型：
--
作者：
EM Pogatzki;GF Gebhart;Tj. Brennan
组织损伤后的原发性痛觉过敏被认为是由初级传入纤维致敏引起的，但对机械刺激的致敏一直难以证明。在另一项研究中，机械反应性阿德尔塔和c纤维的致敏并不能解释大鼠后爪切口后45分钟的疼痛行为。在本研究中，我们检测了大鼠足底后爪无毛皮肤在切开或假手术后1天内阿德尔塔-和c -纤维的机械反应特性。在行为实验中，von Frey纤维的中位戒断阈值从切口前的522 mN降低到切口后20 h的61 mN 2；假手术后的中位退出阈值稳定（522 mN）。切口后对非点状机械刺激的反应增强。在这些大鼠的神经生理学实验中，假手术（n = 39）或切口（n = 28）后1天，从左胫神经获得67条单传入纤维；使用电刺激作为搜索刺激来识别具有代表性的Adelta-和c -纤维群体。在切口组，11根纤维（39%）自发活动，频率范围为0.03 ~ 39.3 imp/s；假手术组没有出现。与假手术组（251 mN, n = 26）相比，切口组（56 mN, n = 13）阿德尔塔纤维的中位反应阈值更低，主要是因为机械不敏感传入神经（MIAs）的比例更低（8比54%）。切开大鼠（28 mN, n = 15）和假手术大鼠（56 mN, n = 13）的中位c纤维反应阈值相似。切口后1天，adelta纤维对单丝的反应性显著增强；c -纤维在切开和假手术后的刺激反应功能无显著差异。只有阿德尔塔纤维对无点状机械刺激敏感，而c -纤维不敏感。切开1 d后，a-纤维和c -纤维感受野的大小增加。结果表明，a-纤维和c -纤维在切开后1天明显增敏。由于传入纤维对机械刺激的敏化与行为结果相关，敏化可能有助于降低切口后的戒断阈值。adela -和c -纤维的自发活动可能解释了非诱发性疼痛行为，也可能通过放大中枢反应而导致机械性痛觉过敏。
Primary hyperalgesia after tissue injury is suggested to result from sensitization of primary afferent fibers, but sensitization to mechanical stimuli has been difficult to demonstrate. In the companion study, sensitization of mechano-responsive Adelta- and C-fibers did not explain pain behaviors 45 min after an incision in the rat hindpaw. In the present study, we examined mechanical response properties of Adelta- and C-fibers innervating the glabrous skin of the plantar hindpaw in rats 1 day after an incision or sham procedure. In behavioral experiments, median withdrawal thresholds to von Frey filaments were reduced from 522 mN before to 61 mN 2 and 20 h after incision; median withdrawal thresholds after sham procedure were stable (522 mN). Responses to a nonpunctate mechanical stimulus were increased after incision. In neurophysiological experiments in these same rats, 67 single afferent fibers were characterized from the left tibial nerve 1 day after sham procedure (n = 39) or incision (n = 28); electrical stimulation was used as the search stimulus to identify a representative population of Adelta- and C-fibers. In the incision group, 11 fibers (39%) had spontaneous activity with frequencies ranging from 0.03 to 39.3 imp/s; none were present in the sham group. The median response threshold of Adelta-fibers was less in the incision (56 mN, n = 13) compared with sham (251 mN, n = 26) group, mainly because the proportion of mechanically insensitive afferents (MIAs) was less (8 vs. 54% after sham procedure). Median C-fiber response thresholds were similar in incised (28 mN, n = 15) and sham rats (56 mN, n = 13). Responsiveness to monofilaments was significantly enhanced in Adelta-fibers 1 day after incision; stimulus response functions of C-fibers after incision and after sham procedure did not differ significantly. Only Adelta-fibers but not C-fibers sensitized to the nonpunctate mechanical stimulus. The size of receptive fields was increased in Adelta- and C-fibers 1 day after incision. The results indicate that sensitization of Adelta- and C-fibers is apparent 1 day after incision. Because sensitization of afferent fibers to mechanical stimuli correlated with behavioral results, sensitization may contribute to the reduced withdrawal threshold after incision. Spontaneous activity in Adelta- and C-fibers may account for nonevoked pain behavior and may also contribute to mechanical hyperalgesia by amplifying responses centrally.