82 CHANGES IN BRAIN GLUCOSE UTILIZATION INDUCED BY ACUTE HYPOXIA DURING DEVELOPMENT

Abstract

Changes in regional glucose utilization might be involved in neuronal damage due to hypoxia. The quantitative autoradiographic 2-14C-deoxyglucose technique (2DG) was applied to the measurement of the effects of an acute hypoxic exposure on local cerebral glucose utilization (LCGU) in the 10 (P10), 14 (P14), and 21 (P21) day-old rat. The animals were exposed to the hypoxic (7% O2/93% N2) or control gas mixture (21% O2/79% N2) for 20 min before the initiation and for 45 min of the 2DG procedure. At P10, the exposure to the hypoxic gas mixture induced a generalized increased in LCGU which affected 40 structures (including white matter) of the 45 studied. At P14, LCGU increased in 5 areas and decreased in 11 regions, mainly brainstem and respiratory areas in hypoxic as compared to control rats. But average cerebral glucose utilization was similar in both groups. Finally, at P21, LCGU decreased in 11 structures of hypoxic rats as compared to controls. The increase in LCGU of the hypoxic 10 day-old rat is likely to be the reflection of the stimulation of anaerobic glycolysis in brain structures with a low metabolic rate. Conversely, at P14 and P21, metabolic rate increases and the brain becomes more dependent upon oxygen. These results suggest that immature brain responds to an acute hypoxic aggression in a specific way according to the maturation of oxidative metabolic pathways.