Fig 4.

Recurrent, self-sustaining epileptiform activity triggered by repeated stimulus trains in hippocampal-entorhinal cortex (HEnC) slices from animals experiencing hyperthermic seizures a week earlier (H-seiz) but not in slices from control litter-mates. (A) Representative traces recorded from the CA1 pyramidal cell layer from slices of a control and a H-seiz rat show that the first stimulus train failed to elicit spontaneous ictal-like epileptiform activity after the immediate afterdischarge in the control slice, but induced recurrent, spontaneous, self-sustaining field discharges in the H-seiz slice (segments of recordings at time points indicated by asterisks below the traces are also shown in an expanded time scale on the right). This self-sustaining activity had a characteristic temporal development, progressively increasing in amplitude as well as in frequency.³³ (B) Plot of Schaeffer collateral stimulation train number versus duration of the afterdischarge induced by the train, showing enhanced epileptogenesis in the HEnC slices from H-seiz rats, compared with controls. Because recordings were terminated if the sustained epileptic activity lasted for more than 30 minutes, the maximal duration indicated on the y scale is 1,800 seconds (Control, n = 4; H-seiz, n = 5).