[Dynamics of pO2 changes in brain tissue during physiologic variations in capillary blood flow rate]

The effect of the rate of the blood flow on pO2 dynamics in capillaries, nerve cells, and surrounding tissue was analyzed on the mathematical model. A two-fold variation in the blood flow rate through capillaries from the average level of 500 micro/sec induced equal changes of pO2 of about 12 torr. A two-fold change in the intensity of oxygen consumption by a cell from the level of 400 microliter O2/g.min shifted the average pO2 in the cell body and surrounding tissue approximately by 2 times and 1.2--1.3 times, resp. Under all these conditions, when the rate of blood flow or the oxygen consumption by a cell changed sharply, a new stable state of pO2 was reached in 2--3 sec. The data obtained suggest that the rates of blood flow in cerebral capillaries are determined by physiological changes in oxygen demand by nerve cells and glia. The diffusion as a mechanism of oxygen transport in the brain, seems both to supply nerve cells with a sufficient amount of O2 under stationary conditions and induce rapid changes in the rate of O2 transport in response to changes in demand for it.