Cerebral oxygen consumption and blood flow in Fischer-344 rats of different ages

Regional cerebral oxygen consumption and blood flow were determined and compared in conscious male Fischer-344 rats at 3, 12, 24 and 33 months of age to correlate the reported regional neurochemical and morphological changes which occur in these parameters during development, maturation, aging and senescence. Cerebral blood flow was determined with 14[C]-labelled iodoantipyrine and regional cerebral arterial and venous oxygen saturation was measured microspectrophotometrically. Oxygen consumption was obtained by multiplying cerebral blood flow and oxygen extraction. Systolic and diastolic blood pressure and heart rate decreased significantly with age. Average cerebral blood flow, oxygen extraction and oxygen consumption/100 g did not differ significantly between the four age groups examined. Oxygen consumption averaged 2.9 +/- 0.1 ml O2/min/100 g (mean +/- S.E.M.) in the 3-month-old group and 3.6 +/- 0.1 ml O2/min/100 g in the 33-month-old group. Differences in flow among the examined brain regions, which were present in the mature, 12-month-old brain, were not present in the developing, aging or senescent rat brain. Compensatory alterations in the efficiency or organization of neurochemical activity which occur during development, aging and senescence may modify the inter-regional differences in cerebral blood flow and oxygen consumption noted during maturation. There was no correlation found between the neurochemical and morphological changes which have been reported during maturation, aging or senescence and regional cerebral oxygen consumption.