Age‐Related Changes in Rat Optic Nerve: Morphological Studies

Abstract

Age-related changes of the optic nerve were studied in 3-month-old (young), 12-month-old (adult) and 24-month-old (aged) male Sprague-Dawley rats. Cross sections of the intracranial portion of the optic nerves of animals of different age groups were stained with haematoxylin-eosin and examined under a light microscope at low and high magnification. Other sections were stained with crystal violet for demonstration of glial cells. A third group of sections were stained immunohistochemically to detect glial fibrillary acidic protein (GFAP) which is a marker for localizing and characterizing astrocytes. All morphological results were subjected to the quantitative analysis of images and to statistical analysis to identify significant morphometrical data. Tissue protein concentrations were determined on homogenized fragments of optic nerve. Our results demonstrate the following age-related changes: (1) increase of the optic nerve sheaths (meningeal membranes); (2) increased number of astrocytes; (3) increase of areal density of GFAP immunoreactivity; (4) increased diameter and area of the optic nerve; (5) decreased number of nerve fibres; (6) decreased-size of nerve fibres and (7) decrease of the nerve fibres/meningeal membrane ratio from 3:1 to 1:1. Moreover, the protein amount does not change with age. The rat optic nerve, therefore, appears sensitive to ageing processes and can be considered as a useful model for the studies on neuronal ageing.

Element Distribution in Visual System, the Optic Chiasma, Lateral Geniculate Body, and Superior Colliculus

“…Microscopic studies demonstrated that the decrease of nerve fibers and myelin degeneration occurred in the optic nerve of monkey [7,8], human [9], and rat [10] at old age. The authors [26] previously investigated age-related changes of elements in the human cranial and spinal nerves including the optic nerve, using the subjects ranging in age from 65 to 91 years and reported that there were no significant changes of the seven elements in the optic nerve with aging.…”

“…There are some reports on age-related changes of the optic nerve [7][8][9][10], lateral geniculate body [11][12][13][14][15][16], and superior colliculus [17,18], which belong to the visual system. Microscopy and MR imaging revealed that the compositional changes occurred in all of the optic chiasma, lateral geniculate body, and superior colliculus with aging [7][8][9][10][11][12][13][14][15][16][17][18].…”

“…Microscopy and MR imaging revealed that the compositional changes occurred in all of the optic chiasma, lateral geniculate body, and superior colliculus with aging [7][8][9][10][11][12][13][14][15][16][17][18]. However, little work had been done to study compositional changes of the visual system with aging by direct chemical analysis.…”

White Matter Vulnerability to Ischemic Injury Increases with Age Because of Enhanced Excitotoxicity

“…The optic nerve, a purely myelinated CNS WM tract (Foster et al, 1982), is one of three models that have been extensively used to study ischemic injury (Agrawal and Fehlings, 1996;Tekkök and Goldberg, 2001). The optic nerve is sensitive to the aging process (Cavallotti et al, 2002(Cavallotti et al, , 2003 and offers several advantages in studying the mechanisms of WM injury including the capacity to quantitatively assess ischemic injury using electrophysiological and immunohistochemical methods.…”

Novel Protective Effects of Histone Deacetylase Inhibition on Stroke and White Matter Ischemic Injury

“…The optic nerve offers the capacity to quantitatively study the structure-function relationship of WM injury mechanisms. In addition, optic nerve is intrinsically sensitive to the process of aging [16,[25][26][27][28][29], and shows progressive molecular and functional changes as a function of age [16,28,29]. HDAC inhibitors preserve function in both young and aging axons [28,29].…”