Platelet embolism in rabbit brain.

Transient cerebral ischemia was induced in rabbits by selective infusion of arachidonic acid (0.35 mg/kg in 15 sec) into the internal carotid artery. Platelet emboli caused transient ischemia of the brain, reaching a maximum within a few seconds after injection. After embolism the EEG flattened, blood flow stopped in almost the entire injected hemisphere, cortical pH gradually fell from 7.31 +/- 0.09 to 7.05 +/- 0.10 and cortical K+ activity rose from 4.7 +/- 1.8 to 12.7 +/- 6.4 mmol/kg H2O. Complete ischemia lasted 3-5 min; then cerebral circulation was gradually restored without reactive hyperemia. Forty-five min after embolization, circulation had been resumed in almost the entire injected hemisphere, whereas metabolic changes were still disturbed. Eighty percent of the animals recovered complete neurological function and 20% showed permanent damage confirmed by histological examination after 1 week of recovery.