Submerged hippocampal slices were exposed to 30 minutes of moderate or mild hypoxia at 29 degrees C and then reoxygenated. Synaptic transmission was lost at the same rate in response to either grade of hypoxia, but recovery was faster following mild hypoxia. Hyperexcitability of synaptic transmission was a lasting feature following moderate hypoxia, but it was transient following mild hypoxia; ...