Murinson Beth Brianna, Griffin John Wesley
Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
J Neuropathol Exp Neurol. 2004 Mar;63(3):246-54. doi: 10.1093/jnen/63.3.246.
Recent advances in regeneration and pain research have revealed gaps in the understanding of normal C-fiber anatomy. In the rat PNS, C-fiber axons assemble into Remak bundles, but beyond this, features of C-fiber organization are not defined. Systematic sampling and quantitation reveals that Remak bundles exiting from the L5 dorsal root ganglion (DRG) contain large numbers of axons, for example, 56% of unmyelinated axons were in bundles of >20 axons. This is different from distal nerve segments such as the hindpaw plantar nerve where the median number of axons per bundle is 3. The cross-sectional area of unmyelinated axons in dorsal root was homogeneous near the DRG but variability in axonal area increased near the spinal cord (p = 0.00001) and the mean axonal area was unchanged. Unmyelinated axons in peripheral nerve were almost always isolated from one another by Schwann cell processes; however, in dorsal root 7% to 9% of unmyelinated axons were immediately adjacent within pockets containing 2 or more axons. Remak bundles in the distal peripheral nerve clustered with other Remak bundles. We observe that multiple unmyelinated axons are juxtaposed within the C-fiber/Remak bundle and that the close association of afferent axons may have important functional implications.
再生与疼痛研究的最新进展揭示了在正常C纤维解剖结构理解方面的差距。在大鼠的周围神经系统（PNS）中，C纤维轴突聚集成雷马克束，但除此之外，C纤维组织的特征尚未明确。系统抽样和定量分析表明，从L5背根神经节（DRG）发出的雷马克束包含大量轴突，例如，56%的无髓鞘轴突存在于由20个以上轴突组成的束中。这与后爪足底神经等远端神经节段不同，后者每束轴突的中位数为3。背根中无髓鞘轴突的横截面积在DRG附近是均匀的，但在靠近脊髓处轴突面积的变异性增加（p = 0.00001），且平均轴突面积不变。外周神经中的无髓鞘轴突几乎总是被施万细胞突起彼此隔开；然而，在背根中，7%至9%的无髓鞘轴突在包含2个或更多轴突的小腔内紧邻。远端外周神经中的雷马克束与其他雷马克束聚集在一起。我们观察到多条无髓鞘轴突并列于C纤维/雷马克束内，且传入轴突的紧密关联可能具有重要的功能意义。
