Oxidative damage in the guinea pig hippocampal slice.

Free radicals and active oxygen compounds are implicated in brain ischemia and head trauma. Previous studies have shown that free radicals, generated by radiation and through the Fenton reaction, produce both synaptic and postsynaptic damage in the hippocampal brain slice. To evaluate the contribution of oxidation to the observed damage, the actions of the oxidants, chloramine-T and N-chlorosuccinimide (NCS), were studied on electrophysiological responses in the hippocampal slice isolated from the brains of guinea pigs. Electrical stimulation of afferents to neurons of the CA1 region of hippocampus evoked a population postsynaptic potential (population PSP) in the dendritic layer and a population spike in the cell body layer. Chloramine-T (25-500 microM) and NCS (750-4000 microM) decreased the population spike in a dose-dependent manner (ED50 congruent to 125 microM and 1100 microM, respectively). Input/output curves revealed that both the population PSP were significantly reduced with both oxidants; but, the ability of the population PSP to produce a population spike was not impaired. These studies suggest that oxidation reactions can account for the synaptic component of the damage produced by free radicals but can not account for the postsynaptic effects.