We examined the functionality of hippocampal CAl neurons at early times after transient global ischemia, by electrophysiologic recordings in brain slices. Transient isch emia was conducted on rats using the method of IS-minute four-vessel occlusion, and brain slices were obtained from these animals at different times after ischemia. Within 24 hours after insult, CAl neurons showed no substantial damage as identified by morphologic means, but exhibited dramatic de creases in synaptic acti vities

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... by 12 hours after insult, which became further decreased at more extended times after recov ery. Blocking -y-aminobutyric acid A (GABA A ) receptors with bicuculline produced a reversible augmentation of the dimin ished synaptic responses in slices prepared from 12-hour postinsult animals, but failed to do so in slices obtained from