The dynamic effect of PETCO, on vertebral bloodflow in cats.

The central chemoreceptors are excited by the composition of the interstitial fluid of the brainstem. The concentration of the constituents is influenced by the perfusion ratio in that area and the composition of the arterial blood, in articular PaCO2. We assessed the perfusion ratio in cats by measuring the blood flow in one vertebral artery and its dependence on changes in PETCO2. Our findings support the theory that CBF is controlled by extravascular pH during CO2-loading. The mean time constant for dilatation (tau = 339.2 s) was found to be considerably greater than the mean time constant for constriction (tau = 40.9 s). Neither time constant depends on the initial flow rate.