Studies On Age-Related Morphological Changes In The Retina Of Cat

Retina is the primary structure that accepts visional information. Retinal aging structural and functional changes may induce vision functional senescence. The studies compare morphological changes in old cats and young cats. 1. We applied Hematoxylin-Eosin and Nissl staining to exhibit the structure of the retinae and ganglion cells respectively, and also we used immunohistochemical ABC method to display the distribution of GFAP-immunoreactive (GFAP-IR) cells that were specifically classified as the astrocytes. Compared with young cats, the retinae in old cats presented a significant decrease in the thickness of total retina, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer as well as an evidently lower density of ganglion cells. Also old cats showed clearly larger number and stronger staining of GFAP-IR cells than did in young cats, and at the same time the GFAP-IR cell bodies and dendrites swelled obviously in old cats .We presume that neurons lose in old cats, which hints that the loss of retinal cells might be of an important factor mediating visual functional declines during senescence. The increase of astrocytes movement may protect aging retina. 2. Immunohistochemical ABC method was applied to display the GABA and NF immunoreactive (GABA-IR and NF-IR) structure. Results show that GABA-IR structure of both groups was observed in amacrine cells, inner plexiform layer, ganglion cells and nerve filament layer. NF-IR cells appeared in horizontal cells, amacrine cells and ganglion cells in old cats, however none in amacrine cells in the young cats. Old cats presented stronger staining and larger number of GABA–IR and NF-IR cells compared with the young cats. The changes of retina during senescence might be an important factor mediating the functional degeneration of vision. 3. Hematoxylin-Eosin method was applied to display outer retina and choroid. Results show that in old cats the structure of photoreceptor layer disorders;the thickness does not significant change and more debris builds up in bruch's membrane, the number of retinal pigment epithelium cells is significantly decline; the thickness of choroid, the number of choriocapillaries decrease significantly, the distance between choriocapillaries augments significantly. We speculate that the degeneration in choroid of old cats might induce the degeneration in bruch's membrane and retinal pigment epithelium, which will impair the function of photoreceptor layer.