[Biochemical aspects of cerebral aging. Role of oxygen]

Only in multiple ischaemic accidents is a reduced oxygen supply to the central nervous system the sole cause of mental impairment. However, oxygen deprivation due to dysregulation of the cerebral blood flow may play a role in elderly atheromatous subjects, in association with primary abnormalities in neuron metabolism. Whatever the importance of oxygen deficiency, major disturbances in oxidative metabolism are present in the aged neuron, including alterations of glycolysis (mostly anaerobic), Krebs' cycle and the redox chain of mitochondria. It has been hypothetized that these disturbances are due to genetic or post-transcription abnormal enzyme synthesis and/or alterations in mitochondria-cytoplasma exchanges due to the action of free radicals on mitochondrial membrane. The effects of these disturbances are twofold. They certainly result in reduction of energy in the aged neuron with less possibility than the adult neuron to increase its metabolic activity, and they induce perhaps disorders in the synthesis of neurotransmitter aminoacids, acetylcholine and gangliosides.