The neuroglia of the rat optic nerve. Part I. Golgi-Hortega and Golgi-EM studies

In the present study, one describes the morphology of the macroglia (astrocytes and oligodendrocytes) of the optic nerve of the albino rat, having been stained according to the modification of del Rio -Hortega of Golgi-Kopsch's method. This cytology has been studied in the intra-orbital optic nerve, in the intracranial portion of the same, in the optic chiasm and in a first segment of the optic tract. Astrocytes show small differences between those located in the marginal zone of the nerve and those located in the center, being all of them classified as belonging to the fibrous type of astrocytes. With their extensions, these cells establish contact with the external limiting membrane, blood vessels and myelinic nerve fibers. On the level of the limiting membrane, their terminal feet form a kind of cellular barrier similar to that of the cerebral cortex in contact with the pia mater. With the nervous fibers, they establish close relationships at Ranvier's nodes level, being arranged around them forming small rings. The oligodendrocytes show their main branches impregnated up to where they reach the myelin sheath, but the protoplasmic compartment of this one is not impregnated, giving a different image to the one seen after microinjections with markers. Morphometric studies using fractal dimension and related parameters are presented next in part II of this work.