Vascular escape in the cerebral microcirculation in the rat

Abstract

The diameter of the cerebral arterioles was measured by serial photomicrography or television microscopy, and the velocity of the erythrocytes in these arterioles was recorded by the two-slit photometric method. The mean arteriolar volume flow was calculated from a flow formula. During a close intra-arterial infusion of norepinephrine or isoproterenol, the cerebral arterioles exhibited a vascular escape phenomenon from both constrictor and dilator influences. The same vascular elements that originally constrict finally dilate, and vice versa, which shows that the vascular escape phenomenon in the cerebral arteriole is attributable to the secondary relaxation or constriction of the constricted or dilated arteriolar segment, respectively.