Erythrocyte Velocity and a Velocity Pulse in Minute Blood Vessels on the Surface of the Mouse Brain

Abstract

High-speed microcinematography of vessels in the subarachnoid space of the anesthetized mouse was used to measure the velocity of erythrocytes in arterioles and venules less than 30µ in diameter. Within arterioles the velocity averaged 3.5 mm/sec, while in venules an average value of 1.9 mm/sec was obtained. A rhythmic alteration in velocity was often observed in the arterioles and was seen occasionally in venules. This cyclical change in velocity was termed the "velocity pulse." The frequency of the velocity pulse was virtually identical to that of the peripheral pulse and is believed to result from a propagation of that pulse into the microcirculation. The velocity pulse was not recognizable in vessels 5µ to 10µ wide. In vessels 10µ, to 30µ, in diameter, the velocity pulse was not accompanied by changes in the width of the vessels.