Glial potentials evoked by single afferent pulses in hippocampal CA1 area in vitro.

Single pulses were applied to the Schaffer collaterals (stratum radiatum) in the hippocampal slice in vitro, and intracellular recordings were made in putative glial cells in the CA1 cell layer. Putative glial cells showed a sustained depolarization following single pulse stimulation of stratum radiatum. The depolarization was larger with high stimulus intensity, and significantly linearly related to the size of the single population spike with a slope of 0.14 mV/mV. For slices with an average maximal single population spike of 11 mV, the average maximal glial depolarization was 2 mV. The range of maximal glial depolarization of 1-3 mV implies that the extracellular potassium concentration immediately outside of the neurons increased by 0.2-0.6 mM after a supramaximal single afferent shock.