Variations of pial arteriolar diameter, arterial blood pressure and arterial blood density in the cat.

Feline pial arteriolar diameters (CVD, cerebral vessel diameter), mean arterial blood pressure and blood density were recorded continuously in order to examine the relation between rhythmic diameter variations and oscillations of blood pressure and density. Under constant arterial pressure, blood density and CVD oscillations of 2-6/min were recorded using a photometric technique. Furthermore, pressure and density variations were induced by bleeding and reinfusion of blood, to observe their influence on CVD. The latter over a period of time become synchronized to parallel variations of pressure and density during hemorrhagic hypotension. This observance was noted after an initial lag phase.