Increased Mitochondrial and Nuclear Gene Expression of Cytochrome Oxidase Subunits I and IV in Neuronal Aging

: To assess the role of mitochondrial metabolic competence (MMC) in neuronal aging, quantitative immunohistochemistry of cytochrome oxidase (COX) subunits I (mitochondrial‐encoded) and IV (nuclear‐encoded) was carried out in the cerebellar cortex of adult and old rats. The optical density (OD) values of the immunostained COX subunits I and IV were measured on an overall area of 75,000 μm2 in the granular and molecular layers of the cerebellar cortex of each animal. In old animals, OD values of subunit I were increased by 35.5 and 34.2% in the molecular and granular layers, respectively, but only the difference found in the latter cerebellar zone was statistically significant (p