BLOOD-BRAIN-BARRIER DISTURBANCE FOLLOWING LOCALIZED HYPERTHERMIA IN RATS

We investigated the morphological effect of hyperthermia on the blood- brain barrier (BBB). The heads of rats were heated locally using hood- lamps, BBB changes were assessed morphologically with horseradish pero xidase (HRP). Histological examinations were carried out 2 and 6 h, 1 and 3 days, and 1 week after the hyperthermia. The acute thermal lesio ns had three zones, i.e. a necrotic zone, a reactive zone and a permea ble zone of viable brain tissue. HRP extravasation was seen in the nec rotic zone and the permeable zone. Electron micrographic observation r evealed HRP had entered the CNS through damaged endothelial cells and disruption of the tight junctions in the necrotic zone, and through nu merous pinocytotic vesicles in the permeable zone. BBB opening to HRP was observed from 6 h to 3 days after hyperthermia.