Age-related changes in rat retina.

PURPOSE To describe the changes in rat retina occurring with ageing by means of histological methods, scanning electron microscopic observations and morphometrical data; and to study by means of biochemical methods the amount of protein content in retinal tissues. METHODS Samples of fresh retinal tissue obtained from young, adult, and aged rats were studied by means of traditional histological methods and by scanning electron microscopy. Particular attention was paid to morphometrical data and to the changes which occur with ageing. With the aid of a quantitative analysis of images, a large amount of morphometrical data was collected. Moreover, the amount of protein content in retinal tissues has been determined. RESULTS Retinal thickness significantly decreases with age. The ganglion cells seem to be more vulnerable to age-related loss than other retinal cells. The number of retinal capillaries is diminished with age. The intercellular connections between photoreceptors, the number of cellular processes, and the number of synaptic bodies of the bipolar cells also decrease significantly with age. These results were all confirmed by scanning electron microscopy observations and morphometrical findings. Biochemical dosage of proteins demonstrates that retinal tissues decrease with age. CONCLUSIONS All morphological, morphometrical, ultrastructural and biochemical data are concordant in demonstrating that the retinal tissues of rats undergo specific changes with age. Our findings are in agreement with those described by previous authors and underline that the rat retina can be considered an optimal model for studies on neuronal maturation and/or neuronal ageing. Since our data have confirmed that many changes occur in rat retina with ageing, we can hypothesize that rat retina is particularly sensitive to developmental changes and to senile decay.