Journal of applied physiology
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Cerebral blood flow (CBF), systemic hemodynamics, and arterial blood gases were measured during control conditions and during and after exposure to either 300 kPa O2 (group 1) or 300 kPa O2 with 2 kPa CO2 (group 2) in awake rats. The respiratory frequency fell with no change of arterial PCO2 (PaCO2) in group 1, but in group 2, respiratory frequency and PaCO2 increased linearly. The cardiac output (CO) and heart rate (HR) fell and systolic arterial pressure (SAP) rose independent of PACO2. ⋯ CBF and rCBF fell despite unaltered PaCO2, whereas hypercapnia prevented these declines. An uneven effect of O2 was observed on rCBF, most pronounced in brain stem regions, independent of the PaCO2. There was a prolonged suppression of O2 supply to brain stem regions both during and after the exposure to O2 in the absence of CO2.