<p>(A) Changes in extracellular pH <u>(pH<sub>e</sub>)</u> in the PC and in mOT induced by ipsilateral MCA occlusion and reperfusion. Occlusion induced a rapid metabolic acidification of the extracellular microenviroment in PC, interrupted by a transient and mild basification (arrow) associated to the hypoxic spreading depression (HD, asterisk). No changes in extracellular [H<sup>+</sup>] were recorded in the mOT, that is not served by the MCA. (B) Simultaneous changes in extracellular potassium concentration ([K<sup>+</sup>]<sub>o</sub>)and extracellular pH in the PC after MCA occlusion and reperfusion. An initial enhancement in [K<sup>+</sup>] was followed by a fast and large increase in [K<sup>+</sup>]<sub>o</sub>. associated to the HD. The schematic drawing on the right illustrates the position of the two-barrel recording electrodes. The field responses (FP) recorded with the conventional extracellular barrel are also shown. The period of MCA occlusion is marked by the shaded area.</p
