(A) Epileptiform activity induced by 4AP application in the PC, l-EC, CA1 and m-EC of the isolated brain preparation is abolished by DNQX and AP5. The application of these glutamatergic receptor antagonists reveals potentials in the EC / hippocampal region that are abolished by further administration of the GABAA receptor blocker bicuculline (BIC) (50 μM). (B) Spontaneous potentials recorded in the PC, CA3 and m-EC and in the CA1 of the contralateral hemisphere during 4AP, CNQX (50 μM) and AP5 (100 μM) perfusion. On the left, traces are presented with a slow time scale to highlight the periodicity of these field potentials. An expansion of the trace outlined by the dotted line is shown on the right. Note that type 1 potentials do not propagate outside the hippocampus, whereas type 2 activity propagates to CA3, m-EC and the contralateral CA1. (C) Examples of type 2 potentials that originate from and propagate to different structures.