Hyperthermia-induced morphological changes in cerebral tissue of the rat.

The sensitivity of cerebral tissue to hyperthermia, its immediate effect, manifested by histological changes and the role of local blood flow, blood rheological properties, and the possible role of free radicals in development of mentioned changes have been studied. Through the cranial window local area of cerebral surface was irrigated by artificial CSF heated up to 41, 43 or 45 degrees C. Serial brain coronal sections 50 microm thick were analyzed under light microscope. Local Cerebral Blood Flow was measured by thermo-clearance method. Blood rheological properties were changed by injection of Dextran T-500 and free radicals existence was controlled by DMSO injection. High sensitivity of cerebral tissue to hyperthermic exposure even at a temperature of 41 degrees C has been confirmed. We consider cerebrovascular thrombosis as one of the most significant complication of brain hyperthermia. Deteriorated blood rheological properties aggravates hyperthermia-induced cerebral lesion. Administration of free radicals scavengers can partially lessen hyperthermia induced cerebral lesion.