[Changes in the extracellular potassium concentration and the slow negative potential in the cerebral cortex]

Changes of potassium concentration in the extracellular space ([K+]0) of the g. suprasylvius of cat cerebral cortex were recorded by means of K+ selective microelectrodes; the electrical field potential was recorded simultaneously. Under deep anesthesia a single electrical stimulus, applied to the cortical surface, at intensity enough to elicit the slow negativity, caused a local increase of [K+]0 reaching 0.1-1.5 mM. The time course of the K+ signal coincide with the course of the slow negativity. It is supposed that the slow negativity reflects glial depolarizaion arising under the action of K+ ions.