Hoyes A D, Barber P
Cell Tissue Res. 1976 Sep 6;172(1):133-44. doi: 10.1007/BF00226054.
The ultrastructure of the corneal nerves of the rat was studied in tissue fixed by immersion in and by perfusion with glutaraldehyde-containing fixatives. Of the four types of axonal terminal identified in the nerves, those with the features of adrenergic and cholinergic terminals were confined to the nerves at the limbus and were concentrated in the perivascular plexuses. The remaining two types of terminal were found on axons located in all parts of the cornea and on both intraepithelial axons located in all parts of the cornea and on both intraepithelial axons and axons in the stromal nerves. Of these, one contained the numerous mitochondria which occur in the terminals of axons associated with known mechanoreceptors and the second contained variable and often small numbers of both clear and large dense-cored vesicles. While most of the mitochondria-containing terminals were seen in nerves located near the periphery,vesicle-containing terminals were numerous in all of the nerves,and especially in those in the avascular cornea. In material fixed by immersion in glutaraldehyde-paraformaldehyde,the vesicle-containing terminals appeared to be dilated,but in material fixed by perfusion there was little evidence of any increase in the diameter of the axons in the terminal regions. The structure of the terminals was compared with that of the terminals of axons identified in the nerves of the skin and the urinary tract and the differences in the vesicle content of the terminals to those reported in other studies of the corneal nerves was related to the use of different fixation procedures. The possibility that axons possessing such terminals are identical with the beaded axons and both the cholinesterase-positive and fluorescent axons demonstrated in light microscopical studies of the corneal nerves is discussed, and the widespread distribution of the axons in the cornea is equated with the hypothesis that they are afferent in nature and represent the peripheral receptors for pain impulses.
用含戊二醛的固定剂浸泡固定和灌注固定的大鼠角膜神经超微结构进行了研究。在神经中鉴定出的四种轴突终末类型中，具有肾上腺素能和胆碱能终末特征的那些终末局限于角膜缘的神经，并集中在血管周围丛中。其余两种终末类型见于角膜各部位的轴突上，以及角膜各部位的上皮内轴突和基质神经内的轴突上。其中一种含有与已知机械感受器相关的轴突终末中出现的大量线粒体，另一种含有数量可变且通常较少的清亮和大的致密核心小泡。虽然大多数含线粒体的终末见于周边附近的神经中，但含小泡的终末在所有神经中都很多，尤其是在无血管角膜的神经中。在戊二醛-多聚甲醛浸泡固定的材料中，含小泡的终末似乎扩张了，但在灌注固定的材料中，几乎没有证据表明终末区域的轴突直径有任何增加。将这些终末的结构与皮肤和尿路神经中鉴定出的轴突终末的结构进行了比较，并且将这些终末的小泡内容物与角膜神经其他研究中报道的差异与使用不同固定程序联系起来。讨论了具有这种终末的轴突与在角膜神经的光学显微镜研究中显示的串珠状轴突以及胆碱酯酶阳性和荧光轴突相同的可能性，并且将角膜中轴突的广泛分布与它们本质上是传入性的并且代表疼痛冲动的外周感受器的假设等同起来。
