Rapid decrease of high affinity ouabain binding sites in hippocampal CA1 region following short-term global cerebral ischemia in rat

Abstract

High affinity [ 3H]ouabain binding was examined in the hippocampal CA1 region and frontal cortex of rats subjected to 5 min complete cerebral ischemia in a clinical death model, and to subsequent resuscitation. A decrease of B max directly after ischemia and its further gradual decrease during 120 min of reperfusion were noted in the ischemia-vulnerable CA1 region, whereas no change of B max was observed in frontal cortex. The apparent K d constant showed insignificant fluctuations in either of the two brain regions. Since ouabain binds with high affinity to the neuronal (α+)-form of Na +/K +-ATPase, the results indicate a rapid enzyme loss in CA1 neurons. The high affinity ouabain binding test proved to be a sensitive detector of premorphological changes in nerve cell membranes in ischemia.