In the study described here a perfusion-dialysis system was used for recording ionic changes in the hippocampus during ischemia. Local perfusion with a Ca²⁺ entry blocker (verapamil) inhibited the fall in extracellular Ca²⁺ concentration which occurs in ischemia. The data consequently suggest that intracellular Ca²⁺ accumulation during ischemia can be blocked. A Ca²⁺ antagonist such as verapamil may thus improve postischemic neuronal recovery via a direct effect on parenchymal cells in addition to the previously suggested vascular effects.