Basbaum A I, Gautron M, Jazat F, Mayes M, Guilbaud G
Departments of Anatomy and Physiology and Keck Center for Integrative Neurosciences, University of California, San Francisco, CA U.S.A. INSERM, U-161, Paris 75014 France.
Pain. 1991 Dec;47(3):359-367. doi: 10.1016/0304-3959(91)90229-Q.
Recently, Bennett and Xie reported that when the sciatic nerve of the rat is ligated loosely, the rat develops a pain syndrome with many features similar to those observed in neuropathic pain states in man. Anatomical and physiological studies to date indicate that the major pathology is a loss of large diameter myelinated fibers distal to the ligatures, with more subtle changes in small myelinated fibers. With a view to evaluating possible changes in the unmyelinated fibers, we have performed an electron microscopic analysis of the sciatic nerve 2 weeks after four ligatures were applied, at which time the animals displayed profound hyperalgesia and mechanical and thermal allodynia. Cross-sectional photomontages of regions proximal and distal to the ligatures were studied. Consistent with light microscopic and electrophysiological studies, we found a near complete loss of large myelinated fibers distal to the ligatures. Phagocytosis of large fibers was common. There was also considerable variation in the damage to small myelinated fibers. In some fascicles many small (less than 3 microns) myelinated axons remained; in other fascicles none could be detected. Importantly, we also found significant changes in the unmyelinated fiber spectrum. Counts of unmyelinated axons revealed a 34% and 71% decrease in the distal compared to the proximal nerve, in the two rats studied. The large clusters of unmyelinated axons that characterize normal nerve (and the nerve proximal to the ligatures) were rarely found distally. Rather, many of the unmyelinated axons coursed singly or in very loose bundles. Many of the surviving axons were shrunken and distorted, although still in contact with Schwann cells.(ABSTRACT TRUNCATED AT 250 WORDS)
最近，贝内特和谢报道称，当对大鼠的坐骨神经进行轻度结扎时，大鼠会出现一种疼痛综合征，其许多特征与人类神经性疼痛状态中观察到的特征相似。迄今为止的解剖学和生理学研究表明，主要病理变化是结扎部位远端大直径有髓纤维的丧失，小直径有髓纤维有更细微的变化。为了评估无髓纤维可能发生的变化，我们在进行四次结扎两周后对坐骨神经进行了电子显微镜分析，此时动物表现出严重的痛觉过敏以及机械性和热性痛觉超敏。对结扎部位近端和远端区域的横断面照片蒙太奇进行了研究。与光学显微镜和电生理研究一致，我们发现结扎部位远端的大直径有髓纤维几乎完全丧失。大纤维的吞噬现象很常见。小直径有髓纤维的损伤也存在相当大的差异。在一些神经束中，许多小（小于3微米）的有髓轴突仍然存在；在其他神经束中则检测不到。重要的是，我们还发现无髓纤维谱有显著变化。对无髓轴突的计数显示,在研究的两只大鼠中，与近端神经相比，远端神经的无髓轴突数量分别减少了34%和71%。正常神经（以及结扎部位近端的神经）所特有的大簇无髓轴突在远端很少见。相反，许多无髓轴突单独或成非常松散的束状走行。许多存活的轴突虽然仍与施万细胞接触，但已萎缩变形。（摘要截选至250词）
