Vabnick I, Novaković S D, Levinson S R, Schachner M, Shrager P
Department of Physiology, University of Rochester, New York 14642, USA.
J Neurosci. 1996 Aug 15;16(16):4914-22. doi: 10.1523/JNEUROSCI.16-16-04914.1996.
The distribution of Na+ channels in rat peripheral nerve was measured during development by using immunofluorescence. Small segments of sciatic nerve from postnatal day 0-13 (P0-P13) pups were labeled with an antibody raised against a well conserved region of the vertebrate Na+ channel. At day P0 axons contained almost no Na+ channel aggregates. The number of clusters increased dramatically throughout the first week. In almost all cases Na+ channels clustered in the vicinity of Schwann cell processes. At least four classes of aggregates were noted. Clusters formed singly at Schwann cell edges, in pairs or in broad regions between neighboring Schwann cells, and in more focal zones at presumptive nodes. Almost all Na+ channel aggregates had reached the latter stage by the end of the first week. Histograms plotting the frequency of occurrence of each cluster type suggested a sequence of events in node formation involving the initiation of channel aggregation by Schwann cell processes. The requirement for Schwann cells during sodium channel clustering was tested by blocking proliferation of these cells with the antimitotic agent mitomycin C. Na+ channel clustering was sharply reduced, whereas node formation was normal at a distal site along the same nerve. Immunocytochemical detection of myelin-associated glycoprotein (MAG) indicated that Schwann cells must begin to ensheathe axons before inducing Na+ channel clustering.
利用免疫荧光技术测定了大鼠外周神经在发育过程中Na⁺通道的分布。对出生后第0 - 13天（P0 - P13）幼崽的坐骨神经小段用针对脊椎动物Na⁺通道保守区域产生的抗体进行标记。在P0天时，轴突几乎不含Na⁺通道聚集体。在第一周内，聚集体的数量急剧增加。几乎在所有情况下，Na⁺通道都聚集在施万细胞突起附近。至少观察到四类聚集体。聚集体单独在施万细胞边缘形成，成对或在相邻施万细胞之间的宽阔区域形成，以及在假定的结处更集中的区域形成。到第一周结束时，几乎所有的Na⁺通道聚集体都达到了后期阶段。绘制每种聚集体类型出现频率的直方图表明，结形成过程中存在一系列事件，涉及施万细胞突起引发通道聚集。通过用抗有丝分裂剂丝裂霉素C阻断这些细胞的增殖，测试了施万细胞在钠通道聚集过程中的必要性。Na⁺通道聚集明显减少，而在同一条神经的远端部位结形成正常。髓鞘相关糖蛋白（MAG）的免疫细胞化学检测表明，施万细胞必须在诱导Na⁺通道聚集之前开始包裹轴突。
