Effects of barium on stimulus induced changes in extracellular potassium concentration in area CA1 of hippocampal slices from normal and pilocarpine-treated epileptic rats.

Laminar profiles of rises in [K+]o and slow field potentials induced by alvear stimulation were recorded in area CA1 of hippocampal slices from control and pilocarpine-treated rats in absence and presence of Ba2+. In control animals, Ba2+ augmented rises in [K+]o in stratum pyramidale (SP) as well as in stratum radiatum (SR). In pilocarpine-treated animals an augmentation of rises in [K+]o was restricted to SP and its immediate vicinity. Moreover, the effect of Ba2+ in SP was small or missing in eight out of 15 slices of pilocarpine-treated animals. In these slices laminar profiles of rises in [K+]o were not affected by Ba2+. It is suggested that spatial K+-buffering is reduced in area CA1 of epileptic animals.