Functional alterations in neural circuits in Alzheimer's disease

• Published in: Neurobiology of aging Vol. 16; no. 3; pp. 305 - 309
• Main Authors: Simonian, Nancy A., Hyman, Bradley T.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: London Elsevier Inc 01-05-1995; Elsevier Science
• Subjects: Aged; Alzheimer Disease - enzymology; Alzheimer Disease - pathology; Alzheimer Disease - physiopathology; Alzheimer's disease; Biological and medical sciences; Biomarkers; Brain - enzymology; Brain - pathology; Brain - physiopathology; Cytochrome oxidase; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Electron Transport Complex IV - metabolism; Energy metabolism; Humans; Medical sciences; Mitochondria; Nerve Net - enzymology; Nerve Net - physiology; Neurology; Cytochrome oxidase; Mitochondria; Energy metabolism; Alzheimer's disease; Human; Nervous system diseases; Enzyme; Alzheimer disease; Central nervous system; Cytochrome-c oxidase; Biological marker; Gene expression; Cerebral disorder; Enzymatic activity; Central nervous system disease; Degenerative disease; Oxidoreductases; Hippocampus; Brain (vertebrata)
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/0197-4580(95)00034-C

While a correlation exists at the regional level between the distribution of neurofibrillary tangles and the predicted sites of brain dysfunction based on clinical and functional neuroimaging studies, the relationship between neurofibrillary tangles and neuronal dysfunction is poorly understood. Using cytochrome oxidase activity as a marker of neuronal functional activity, we found reductions in metabolic activity both in a hippocampal subfield with a high density of neurofibrillary tangles (CA1) as well as in subfields relatively spared (CA3, dentate granule cells). In contrast, we found no reduction in activity in primary visual cortex. Using in situ hybridization, we found a selective reduction in a mitochondrial-encoded cytochrome oxidase mRNA transcript with sparing of a nuclear-encoded transcript. These results suggest that the reduction in cytochrome oxidase activity in Alzheimer's disease brain may be related to an alteration in mitochondrial gene expression. The absence of a direct correlation between structural pathology and cytochrome oxidase activity suggests that neurons that remain structurally intact in Alzheimer's disease may nonetheless undergo substantial changes in metabolic activity.