Electrical fields directly contribute to action potential synchronization during convulsant-induced epileptiform bursts.

Synchronous field-potential bursts were induced in hippocampal slices with picrotoxin. Differential recording between intracellular and adjacent extracellular electrodes during paroxysmal depolarization shifts revealed rapid transmembrane depolarizations (TMDs), which were spike prepotentials generated by electrical field effects. These experiments demonstrate that endogenous electrical fields contribute to spike synchronization in the presence of convulsant drugs when excitatory chemical synapses are functional.