The role of interstitial potassium in the generation of low-calcium hippocampal seizures.

The explosive nature of a focal cortical seizure suggests the operation of strong positive feedback in the neuronal network. It was previously proposed that in the hippocampus this may be provided by the regenerative accumulation of potassium in the interstitium. This hypothesis was severely criticized in the past. However, it gained new impetus with the recent discovery that focal seizures can arise in mammalian hippocampal slices perfused with low calcium solutions despite the block of chemical synaptic transmission. Here, we examine the relationship of interstitial potassium concentration to the electrogenesis of these low-calcium seizures. Both the experimental data and the behavior of a simplified mathematical model describing neuronal discharge in low calcium, support the contention that interstitial potassium accumulation may play an important role in the buildup of hippocampal seizures.