Changes in the extracellular potassium concentration and the slow negative cortical potential

Changes in the extracellular potassium ion concentration ([K⁺]₀) of the suprasylvian gyrus of the cat cortex were recorded by potassium-selective microelectrodes; the electric field potential was recorded at the same time. Under deep anesthesia one electrical stimulus, of sufficient intensity to induce a slow negative potential when applied to the cortical surface, evoked a local increase in [K⁺]₀ by 0.1–1.5 mM. The time course of this rise was very similar to that of the slow negative potential. It is suggested that this potential reflects glial depolarization under the influence of K⁺ ions.I.S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Institute of Physiology, Czechoslovak Academy of Sciences, Prague. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 459–463, September–October, 1980.