Disruption of the blood-brain barrier in open and closed cranial window preparations in rats

The goal of this study was to determine whether the severity of disruption of the blood-brain barrier during acute hypertension is similar in open and closed cranial window preparations. Intravital fluorescent microscopy and fluorescein-labeled albumin were used to evaluate disruption of the blood-brain barrier under control conditions and during acute arterial hypertension in 10 rats equipped with an open cranial window and in six rats equipped with a closed cranial window. Permeability of the blood-brain barrier was quantified by calculating the clearance of fluorescein-labeled albumin and by counting the number of microvascular leaky sites under control conditions and during acute hypertension. Pressure in cerebral venules and intracranial pressure were measured in rats equipped with an open cranial window and a closed cranial window, respectively, under control conditions and during acute hypertension. In rats equipped with an open cranial window, arterial pressure increased from 118 +/- 6 to 189 +/- 3 mm Hg (mean +/- SEM) and pial venous pressure increased from 7 +/- 1 to 22 +/- 3 mm Hg during acute hypertension induced with 30 micrograms/kg/min phenylephrine for 5 minutes. In addition, the clearance of fluorescent albumin increased from 0.11 +/- 0.03 to 1.2 +/- 0.4 ml/sec x 10(-6) and the number of microvascular leaky sites increased from 0 to 25 +/- 1 during phenylephrine infusion. In rats equipped with a closed cranial window, arterial pressure increased from 122 +/- 5 to 187 +/- 7 mm Hg and intracranial pressure increased from 3 +/- 1 to 12 +/- 1 mm Hg during the intravenous infusion of 30 micrograms/kg/min phenylephrine for 5 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)