[Regulation of local tissue PO2 in the cerebral cortex of the cat].

Local PO2 was measured in the cat cortex on adjacent sites with a platinum multiwire surface electrode both during steady state conditions and with varying arterial oxygen supply. Concomitantly, PO2 in the sinus sagittalis was recorded continuously through the vascular wall. Under normoxia and steady state conditions local tissue PO2 values varied between O Torr and almost arterial levels of 85 Torr in accordance with theoretical calculations. With increased arterial oxygen supply local tissue PO2 as measured on agjacent sites was found to react fairly differently. Linear increases in local tissue PO2 as compared with arterial PO2, as well as constant levels, or only very small increases, were recorded. The constancy of local PO2 (="local PO2 autoregulation") was caused by local vasoconstriction. With reduced supply of arterial oxygen, however, tissue PO2 dropped in all studied sites down to hypoxia and anoxia. PO2 autoregulation during a decrease in arterial PO2, as described by Bicher (1973) could not be found.