Changes in Extracellular Ionic Composition

Ion gradients, formed by the relative concentrations of ions in the extracellular and intracellular spaces, form the basis of neuronal function. The gradients are generated by electrogenic pumps and are maintained by control of ion channel function. During seizure activity, there is an increase in extracellular potassium and a decrease in calcium, magnesium, sodium, and chloride. These levels are then brought back to ‘baseline’ levels after termination of the seizure activity. Both neuronal and glial mechanisms contribute to the regulation of the ionic environment and to the restoration of the ion gradients after seizures. Whether abnormalities in this regulation are a cause of seizures is not known.