ON LOCATION OF FLOW RESISTANCE IN CEREBRAL CIRCULATION

In urethane-chloralose anesthetized cats pressure measurements were made in small parietal pial arteries by micropunctures and the counter-pressure measurement-method of Landis. The pial artery pressures were compared with the mean pressures in the aorta, and that part of the vascular resistance in the pial circulation was determined, which is placed between the aorta and the punctured pial arteries. In the mean, 39.4% of the total flow resistance were found between the aorta and pial arteries 30-40 microns in outside diameter (at a mean of the aortic pressure of 88 mm Hg), and only 26.8% up to pial arteries 70 to 85 microns in diameter (at 82 mm Hg aortic pressure). Generally, the arterial part of the total flow resistance was higher at higher aortic pressures. The data demonstrate the importance of the flow resistance of the vessels between the aorta and the punctured pial arteries for the adjustment of the vascular resistance in the pial circulation: It is evident that also the resistance of these vessels take part in any greater changes of the total flow resistance. © 1969 Springer-Verlag.