Potassium accumulation in interstitial space during epileptiform seizures.

The K4a surface efflux from the cat neocortex and rat hippocampus was studied after preloading with K”a from the surface. This K4s efflux increases from two to nine times during or after all electrically or Metrazol-induced seizures and “spontaneous” seizures. The K4s influx does not change during a seizure, so this increased efflux is not due to change in the diffusion constant or water flow from brain. The time course of the efflux is not compatable with the efflux simply idicating increased turnover of potassium from cells. We conclude there is an increase in the concentration of potassium in the interstitial space during seizures. A model is proposed in which this potassium accumulation is an important step in the regenerative, all-or-none-aspect of the initiation of seizures.