Electrophysiological recovery after compression ischemia of the rat brain.

Cerebral ischemia of 15 min was produced in rats by increasing intracranial pressure above the systolic blood pressure level by infusing artificial cerebrospinal fluid into the cisterna magna. Pulmonary edema was prevented by blocking the vasomotor response with a ganglioplegic agent, and reducing the fluid load by peritoneal dialysis. The EEG flattened after 10.1 +/- 1.5 sec. followed by a dilatation of the pupils after 1--2 min. The EEG began to recover in 21 of 32 rats after 8 to 35 min of recirculation. Spectral analysis revealed an initial return of slow waves and spindles followed by continuous fast frequency activity. The EEG did not recover or was secondarily suppressed in 12 animals after a few hours. Electrophysiological recovery depended on the cardiocirculatory and respiratory state, the recovery being optimal in animals with mild hypertension and a normal acid-base status of the blood.