EFFECTS OF BARIUM ON STIMULUS-INDUCED CHANGES IN [K+](O) AND FIELD POTENTIALS IN DENTATE GYRUS AND AREA CA1 OF HUMAN EPILEPTIC HIPPOCAMPUS

The effects of barium on stimulus-induced rises in [K+](o) were studie d in the dentate gyrus (DG) and area CA1 of human hippocampal slices. Rises in [K+](o) elicited by repetitive stimulation of the hilus, stra tum moleculare, alveus, or stratum radiatum were dependent on stimulus intensity and frequency. Barium augmented rises in [K+](o) in the DG by about 120% but failed to do so in area CA1. In both DG and area CA1 barium had no effects on population spikes whereas stimulus-induced s low field potentials were reduced. Since barium interferes with K+ upt ake and redistribution by blocking leak conductances and inwardly-rect ifying currents in astrocytes, our findings suggest that glial cells i n the sclerotic hippocampal area CA1 may contribute less to K+ regulat ion. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.