NMDA Receptor–Dependent Increase of Cerebral Glucose Utilization after Hypoxia–Ischemia in the Immature Rat

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Abstract
Post-treatment with the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 reduces hypoxic–ischemic brain injury in immature animals. To elucidate possible mechanisms, cerebral glucose utilization (CMRglc) and cerebral blood flow (CBF) were measured 1–5 h after hypoxia–ischemia and administration of MK-801 in 7-day-old rats. After 100 min of unilateral hypoxia–ischemia, half of the pups were injected with MK-801. CMRglc was assessed by the [14C]deoxyglucose (2-DG) method. The brains were analyzed either by autoradiography or for energy metabolites and chromatographic separation of 2-DG-6-phosphate and 2-DG. CBF was measured by the autoradiographic [14C]iodoantipyrine method. Mean CMRglc in the cerebral cortex was increased ipsilaterally after hypoxia–ischemia to 15 ± 3.3 μmol 100 g−1 min−1 ( p < 0.01) and areas with CMRglc >20 μmol 100 g−1 min−1 amounted to 8.0 ± 7.7 mm2 in the ipsilateral hemisphere compared with 1.2 ± 1.6 mm2 contralateral ( p < 0.001). Treatment with MK-801 decreased CMRglc bilaterally ( p < 0.05) and reduced ipsilateral areas with increased CMRglc by 64% ( p < 0.01). CBF was unaltered after hypoxia–ischemia and by MK-801 treatment. In conclusion, regional glucose hyper-utilization in the parietal cortex after hypoxia–ischemia was attenuated by MK-801; this may have relevance to the neuroprotective effect of NMDA-receptor antagonists in this model.