Objective      To explore the dynamic changes of blood brain barrier (BBB) permeability after experimental subarachnoid hemorrhage (SAH) in rats.       Methods      Eighty female SD rats were divided into normal saline control group (n=10) and SAH group (n=70). The SAH model was induced by injecting 300 μl of autologous arterial blood into the subarachnoid space near the circle of Willis via a cannula in an artificial hole between the olfactory bulb and frontal lobe. BBB permeability in cerebral cortex of SAH and normal saline rats was assessed at 6

12

24

36

48

60

and 72 h after SAH establishment by fluorescence spectrophotometer and fluorescence microscopy for Evans Blue (EB) extravasation. The ultrastructural changes in BBB were observed with transmission electron microscope.       Results      Compared with the control group

the changes of Evans Blue content and extravasation in cerebral cortex of SAH group peaked at 36 h (P0.05)

and down to the normal level at 60 h after SAH (P0.05). The severe ultrastructural abnormality was found at 36 h after SAH.       Conclusion      The changes of BBB permeability develop at the acute stage of SAH

resulting from multiple factors together. The BBB after SAH possesses a self-repairable property.