Influence of osmolality on seizure amplitude and propagation in the rat dentate gyrus.

We tested the role of changes in extracellular space on synchronization and propagation of epileptiform activity in the dentate gyrus in vitro by manipulating the osmolality of the perfusing solution. Increasing the osmolality reduced the amplitude of the population spikes and slowed the propagation of the epileptiform activity. Decreasing the osmolality had the opposite effect. Assuming there were significant changes in the size of the extracellular space, and therefore the ease with which ephaptic interactions can occur, these results support the hypothesis that ephaptic interactions play a role in the synchronization and propagation of epileptic activity in the dentate gyrus.