Blood-brain barrier damage in reperfusion following ischemia in the hippocampus of the Mongolian gerbil brain

Vascular permeability to intravenously injected horseradish peroxidase (HRP ) was qualitatively examined in the hippocampus of ischemic Mongolian gerbi l brains by light and electron microscopy. After 30 min of right common car otid artery occlusion followed by 90 min of reperfusion, the animal was per fused with a fixative and killed. Before the perfusion of the fixative, HRP was injected into the femoral vein. HRP was visualized with tetramethyl be nzidine (TMB) and diamino-benzidine (DAB) for light and electron microscopy , respectively. Staining reaction with TMB for HRP appeared in medial or do rsal portions of the operated side of the hippocampus, especially around so me vessels along the hippocampal fissure. Ultrastructural examination in th e vessels along hippocampal fissure revealed that the endothelial cytoplasm contained HRP-filled vesicles or vacuoles in close proximity to the basal lamina, and seemed to be slightly electron-dense. Swollen pericytes, swolle n astrocytic foot processes and perivascular cells with HRP-filled cytoplas m were also observed in that area. In this study, it was clearly demonstrat ed that intravascular macromolecules leaked transendothelially, through Ves sel walls in the hippocampal fissure, from the blood stream in the medial p ortions of the hippocampus during reperfusion following ischemia. These fin dings suggest that the blood-brain barrier in some vessels along the hippoc ampal fissure in the medial parts of the hippocampus is more vulnerable to ischemic insults than those in other brain areas.