[Mechanism of "autoregulation" of the cerebral circulation: role of neurogenic and myogenic vascular reactions].

The neurogenic and pure myogenic responses of the dog circulatory isolated internal carotid artery were studied under conditions of controlled intraluminal pressure changes. The artery was continuously perfused with the oxygenated bicarbonate Ringer-Krebs solution, and the vascular responses were estimated as changes in the perfusion fluid flow rate recorded with a drop-flowmeter. The quantitative analysis of the vascular responses showed that a comparatively constant perfusion fluid flow independent of the rate of perfusion pressure changes only occurred when the neurogenic control of the artery was preserved. The pure myogenic responses of the artery were only observed in 25% of tests, were four times weaker and present only within the narrow limits and at a specific rate of the intraluminal pressure changes.