Efflux of potassium from neurones excited by glutamate and aspartate causes a depolarization of cultured glial cells.

The time course of the depolarization of cultured astrocytes and neurones by glutamate and aspartate corresponds well with the increase of the extracellular K+ concentration ([K +]0) measured with an ion-sensitive microelectrode placed in the close vicinity of the cells tested. It is concluded that the depolarization of glial cells is caused by an efflux of K+ from neighbouring neurones during their excitation by the amino acids.