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Although intravenous (iv) injection of potassium cyanide (KCN) activates the arterial chemoreflex, it has been questioned whether cytotoxic hypoxia reproduces a physiological stimulus such as hypoxic hypoxia (low inspired O₂ tension). Thus, the goal of the present study was to compare the cardiovascular responses elicited by intravenous injection of KCN to those caused by hypoxic hypoxia in awake rats before and after bilateral ligature of carotid body arteries. We tested the hypothesis that hypoxic hypoxia activates the cardiovascular chemoreflex just as KCN does, causing an increase in arterial pressure and bradycardia. Intact adult Wistar rats received an intravenous injection of KCN (160 μg/kg) and were exposed to hypoxic hypoxia (7–5% O₂ breathing) for 10–15 s at random while mean arterial pressure (MAP) and heart rate (HR) were measured. After the experiments, the animals were submitted to bilateral …