Drug refractoriness of epileptiform activity in organotypic hippocampal slice cultures depends on the mode of provocation.

We previously reported that low Mg(2+) or 4-aminopyridine induced seizure-like events in organotypic hippocampal slice cultures (OHSCs) were resistant to standard antiepileptic drugs (Albus et al., 2008). We now show that high-frequency electrical stimulation induced ictal-like afterdischarges in OHSCs are effectively suppressed by the standard antiepileptic drugs phenytoin and carbamazepine. Thus, a single OHSC can express both pharmacoresistant and pharmacosensitive epileptiform activities.