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In vivo measurement of 31P nuclear magnetic resonance spectrum of aging mouse brain.

31P nuclear magnetic resonance spectra of the brains of young, mature and old C57BL/6 mice were measured in vivo. Under normal conditions, no significant changes with age were observed in the spectra and there were no statistically significant age-related differences in the ratio of phosphocreatine to adenosine triphosphate (ATP). When the animals were stressed by subjecting them to oxygen restriction, the young and mature mice showed no change in the ratio, whereas it increased in the old mice. These results are consistent with the view that energy metabolism is unimpaired in the brains of unstressed old animals but that ATP synthesis may be decreased with age in a stressed animal.