Do nitrous oxide and lidocaine modify the blood-brain barrier in acute hypertension in the rat?

Acute hypertension was induced by adrenaline or bicuculline in rats mechanically ventilated with 70% nitrous oxide in oxygen, in unrestrained rats breathing the same gas mixture, and in conscious unrestrained rats breathing air. The unrestrained rats had permanent indwelling catheters in the aorta and in one jugular vein. Three minutes after the pressure rise the rats were killed and the brains perfused in situ with saline. The protein leakage into the brain was studied with Evans blue-albumin and 125IHSA (human serum albumin). The extravasation of 125IHSA in unrestrained rats breathing nitrous oxide was higher than in rats breathing air after injection of bicuculline, but the difference was not statistically significant. Lidocaine significantly decreased the protein leakage in both conscious and anaesthetized rats. It is concluded that not only the vascular tone but also endothelial cell membrane properties can influence the hypertensive blood-brain barrier dysfunction.