REESTABLISHMENT OF THE BLOOD-BRAIN BARRIER TO PEROXIDASE FOLLOWING COLD INJURY TO MOUSE CORTEX

Following the induction of cold lesions in the parietal cortex of mice, i.v. injected horse radish peroxidase (HRP) was used to investigate the blood-brain barrier of the intracerebral vessels to this protein. During the first week the majority of the arterioles and capillaries within the necrotic zone of the lesion had leaked HRP into the brain parenchyma. The capillaries in the peripheral zone were surrounded by swollen astrocyte end feet but HRP was confined to vesicles within the endothelial cell cytoplasm. Small arterioles (10-20 μm diameter) in the peripheral zone were observed leaking HRP and the reaction product was observed in the perivascular basement membranes and in vesicles within the endothelial cell cytoplasm. During the 2nd and 3rd weeks the regenerating capillaries which grew into the previously necrotic zone from the periphery revealed no evidence of leakage of HRP. Several non-patent regenerating capillaries were also observed at this time but by the 4th week all capillaries contained HRP within their lumen. The small arterioles in the peripheral zone continued to leak peroxidase throughout the period of the study. In the 2nd week approximately 10% of the arterioles examined were leaking HRP but by the 4th week only 2 out of 53 arterioles were involved. The possibility that the impaired BBB function of the small arterioles is due to an absence of a sympathetic innervation or to raised levels of serotonin is considered. © 1979 Springer-Verlag.