Some factors influencing the damaging effect of acute arterial hypertension on cerebral vessels in rats.

1. Abrupt increase of arterial blood pressure can give rise to multifocal areas of protein extravasation in the brain due to overstretching of the vessels. 2. The vascular tone of the resistance vessels is of importance for the occurrence of the increased permeability. 3. Vasodilatation aggravates the damaging effect of acute hypertension whereas vasoconstriction induced by hyperventilation reduces the incidence of areas of increased permeability. 4. Ligation of a carotid artery prevents lesions in the ipsilateral hemisphere.