Cerebral I/R in Ang II hypertensive mice induces BBB disruption that is largely dependent on blood cell-associated AT1aR. Focal brain ischemia (45 min) and reperfusion (24 hrs) were induced by occluding the middle cerebral artery using the intraluminal filament method. Evan's blue (EB) dye was administered at the time of reperfusion or sham operation. Twenty-four hours later, brain tissue and plasma samples were collected for EB measurement. BBB permeability was estimated by dividing tissue EB concentration by plasma concentration in saline (Panel A) or Ang II (2000 ng/kg/min, 2 wks)(Panel B) infused mice. The data are shown as mean ± SE with 5-7 mice per experimental group. * denotes p < 0.05 relative to non-ischemic WT mice. † denotes p < 0.05 relative to WT mice + I/R. ‡ denotes p < 0.05 relative to WT→WT BM chimeras. N.E.: no examination.