Experiments were performed on white male Wistar rats under Nembutal-urethane anesthesia. Transient ischemia (10 min) was produced by clamping of the carotid arteries. Some neurons in the parietal area of the cerebral cortex and endotheliocytes in blood vessels showed increases in NO synthesis and in the activity of energy metabolism enzymes (SDH, LDH). Changes in the ultrastructure of some neurons and synaptic formations provided evidence of a state of functional pressure, while changes in others indicated irreversible changes (disturbances in lipid metabolism and destructive changes in the nucleus and cytoplasm).