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

Abstract 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 Ba 2+ . In control animals, Ba 2+ 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 Ba 2+ 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 Ba 2+ . It is suggested that spatial K + -buffering is reduced in area CA1 of epileptic animals.