Reversible microwave effects on the blood-brain barrier.

Low level microwave exposure of Chinese hamsters resulted in reversible permeability of the blood-brain barrier (BBB) to horseradish peroxidase (HRP). Lesions were grossly visible in random areas of the brain immediately following exposure, but were not as common following a 1 h recovery period and were absent after a 2 h recovery period. The apparent route of increased permeability was via endothelial vesicular transport, since reaction product was not seen passing through the endothelial tight junctions. In addition, endothelial flooding of HRP, platelet aggregation and perivascular edema were observed only in experimental animals. Possible mechanisms of the enhanced vesicular transport are discussed.