DECREASED RAT-BRAIN CYTOCHROME-OXIDASE ACTIVITY AFTER PROLONGED HYPOXIA

Three weeks of hypoxic exposure results in a spectrum of systemic phys iological and local brain tissue adaptations. Cytochrome oxidase histo chemistry was used as an indicator of changes in energy demand in resp onse to hypoxia. We found overall cytochrome oxidase activity decrease d in hypoxic adapted rats as compared to normoxic control rats. Some r egions, notably layer 3 of the frontal cerebral cortex, layer 4 of the parietal sensory barrel fields, lacunosum moleculare hippocampi, and specific nuclei of the rostral ventral medulla, though exhibiting cyto chrome oxidase activity decreases of 16-27%, still retain their relati vely higher levels of activity. We conclude that there is a hypometabo lic component of the rat brain adaptation to continued hypoxia.