QUANTITATIVE HISTOCHEMICAL-STUDY OF CYTOCHROME-OXIDASE IN THE DLGN OFAGING RATS

We carried out a quantitative histochemical study of the enzyme cytoch rome oxidase (GO) in neurons of the dorsal lateral geniculate nucleus (dLGN) of male Wistar rats aged 3: 18, 24 and 28 months. The results s how that the activity of cytochrome oxidase decreases significantly be tween 24 and 28 months. We also checked whether a correlation existed between neuronal size and enzymatic activity. Low correlation coeffici ents were obtained which were between 0.4139 at 3 months and 0.2092 at 28 months. Nevertheless, we observed a certain relationship between b oth parameters, and therefore we classified the neurons as light, mode rate and dark according to their optical density, which correlates wit h enzyme cytochrome oxidase activity, and as small, medium and large d epending on their size. We found that light neurons were scarcely repr esented in the dLGN. At the age of 3 months, the most frequent neurons were moderate, medium-size ones, and dark, small ones. The population of moderate neurons increased with age, reaching 74.5% at the 28th mo nth, 52.2% of which corresponded to medium-size neurons. In the same g roup dark neurons decreased, falling to a total of 15.3% made up of me dium and large-size ones. These results could be interpreted as reflec ting a decrease in the bioenergetic competence of the neurons of this nucleus in old age.