Glial origin of negative shifts of cortical surface potential during tetanic stimulation: Microelectrode study and mathematical analysis

Experiments on anesthetized cats showed that a negative shift of potential on the surface of the cerebral cortex caused by its tetanic stimulation is similar in shape and time course to the depolarization shift of membrane potential of the glial cells, but has a more rapid decline. The hyperpolarization shifts of membrane potential of neurons differed in shape and time course from the negative shift of cortical surface potential. It is concluded that the contribution of hyperpolarization of neurons to the surface-negative potential shift during tetanic stimulation may be manifested visibly only at the beginning (the first 200–300 msec) of such stimulation. The negative potential shift on the cortical surface is due mainly to depolarization of glial cells under the influence of K⁺ secreted from excited nerve cells.