Crespo D, Verduga R, Villegas J, Fernández-Viadero C
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Cantabria, Santander, Spain.
Histol Histopathol. 1995 Apr;10(2):289-99.
The effects of the retinal ganglion cell (RGC) activity blockage on the early myelination of the rat optic nerve (ON) were investigated at the light and ultrastructural levels. The blockage of the RGC action potential was attained by the use of tetrodotoxin (TTX), a blocker of the voltage-sensitive sodium channels. TTX was either infused directly into the left eye (TON) or injected systematically (SON). These two groups of ONs were compared with the untreated paired right nerves (UON) of the eye-infused group. Our observations showed that the general morphology of the ONs in either treated group was similar to that of the UONs. The most noticeable ultrastructural feature of these nerves was the presence of dimorphic myelin sheaths in 4% of the myelinated fibres (MFs) in the TON group at postnatal day twelve, while they were seldom observed in the other groups (0.5%). These abnormal covers were of two types; long flaps of aberrant myelin or redundant myelin profiles. However, at postnatal day seven, the onset of myelination and the percentage of MFs was similar in the three groups. The morphometric results showed that there were no age-group differences in axon size in unmyelinated and MFs. These results suggest that while the bioelectrical activity of the RGCs could not play any role in maintaining axon calibre it may, to some extent, regulate the process of formation of normal myelin sheaths in the rat ON.
在光学和超微结构水平上，研究了视网膜神经节细胞（RGC）活动阻断对大鼠视神经（ON）早期髓鞘形成的影响。通过使用电压敏感性钠通道阻滞剂河豚毒素（TTX）来实现RGC动作电位的阻断。TTX要么直接注入左眼（TON），要么进行全身注射（SON）。将这两组视神经与眼内注射组未处理的配对右侧神经（UON）进行比较。我们的观察结果表明，任一处理组中视神经的总体形态与UON相似。这些神经最显著的超微结构特征是，在出生后第12天，TON组中4%的有髓纤维（MFs）存在双形态髓鞘，而在其他组中很少观察到（0.5%）。这些异常覆盖物有两种类型：异常髓鞘的长瓣或多余的髓鞘轮廓。然而，在出生后第7天，三组中髓鞘形成的起始和MFs的百分比相似。形态计量学结果表明，未髓鞘化纤维和MFs的轴突大小在年龄组之间没有差异。这些结果表明，虽然RGC的生物电活动在维持轴突口径方面可能不起任何作用，但它可能在一定程度上调节大鼠视神经中正常髓鞘形成的过程。
