Monosynaptic transmission during epileptiform activity induced by penicillin in hippocampal slices in vitro.

Synaptic transmission was studied in the CA1 region of transverse hippocampal slices in vitro before and after the addition of the epileptogenic agent sodium benzyl penicillin. The presynaptic fibre volley and the field potential associated with the intracellular EPSP, 'field EPSP', were recorded from the layer of the activated synapses. Addition of penicillin did not change either response. The rising phase of the intracellularly recorded EPSP did not change. However, the peak amplitude and, particularly, the duration of the EPSP both increased. The prolongation of the EPSP may be of importance for the triggering of epileptiform bursts.