Far field effects of seizure like events induced by application of 4-AP in combined entorhinal cortex hippocampal slices

Epileptiform activity induced by 4-AP in hippocampal area CA1 is characterised by short recurrent discharges. These are occasionally superimposed by slow field potential (fp) shifts. Simultaneous recordings of fps and [K(+)](o) in area CA1 and temporal cortex showed a slow fp shift in both regions, but associated rises in [K(+)](o) occurred only in the cortex. Slow fps in area CA1 persisted after disruption of the perforant path, but were abolished after removal of the adjacent cortex from the hippocampus. These findings suggest that slow fps in CA1 can represent far field effects of seizure like events generated in neighbouring cortex.