Abstract • 174

Previous studies have shown that interrelated biochemical alterations are triggered during hypoxia - ischemia in mature subjects resulting in cellular death. Many of these alterations, as an example, are also being recognized in the immature brain. We investigate the mechanisms of hypoxic brain cell injury in the immature animal by examining (1) the role of excitatory amino acid neurotransmitter receptors. (2) the receptor-mediated increase in intracellular CA/2+ and (3) the generation of oxygen free radicals. We studied the effect of tissue hypoxia on the NMDA receptor-ion channel complex including the glutamate, Mg/2+, spermine, CPP, and the non-NMDA receptor kainate sites. Hypoxia increased the affinity of both the ion channel and the glutamate recognition site for the NMDA receptor. Pretreatment of animals with the glutamate antagonist CPP prevented hypoxia-induced modification of the channel. Similarly, pretreatment of animals with Mg/2++, a blocker of the NMDA receptor-ion channel, prevented the hypoxia-induced modification of the receptor. In addition, an increased agonist-dependent entry of Ca/2+ into synaptosomes was observed in hypoxic animals. Increased free radical generation in the cerebral cortex during hypoxia was demonstrated using spin-labeling technique and electron resonance spectroscopy. We conclude that hypoxia-induced modification of the NMDA receptor-ion channel complex leads to increased intracellular Ca/2+ potentiating free radical generation and resulting in hypoxic cell injury.