Blockade of excitatory amino acid receptors protects anoxic hippocampal slices.

Experiments in a variety of preparations have indicated that excessive activation of receptors for the excitatory amino acids glutamate and aspartate may mediate irreversible anoxic neuronal injury. We investigated this hypothesis in the in vitro hippocampal slice. Rat hippocampal slices perfused for 40 min with buffer equilibrated with 95% nitrogen/5% carbon dioxide lost their extracellular CA1 population spikes and failed to recover after prolonged reoxygeneration. It was impossible to locate cells with normal physiological properties in these anoxic slices with standard intracellular recording techniques. However, when excitatory transmission was blocked during anoxia with either high concentrations of magnesium or antagonists of excitatory amino acids (kynurenate or aminophosphonovalerate), the population spike returned to preanoxia levels. Intracellular recording showed that neurons in these protected slices had normal resting potentials, action potentials, and input resistances. These experiments provide additional support for the involvement of excitatory amino acids and their receptors in anoxic neuronal injury.