Abstract: | Gautier, Henry, Cristina Murariu, and Monique Bonora.Ventilatory and metabolic responses to ambient hypoxia orhypercapnia in rats exposed to CO hypoxia. J. Appl. Physiol.83(1): 253-261, 1997. We have investigated at ambienttemperatures (Tam) of 25 and5°C the effects of ambient hypoxia(Hxam; fractional inspired O2 = 0.14) and hypercapnia(fractional inspiredCO2 = 0.04) on ventilation ( ),O2 uptake( O2), andcolonic temperature (Tc) in 12 conscious rats before and after carotid body denervation (CBD). Therats were concomitantly exposed to CO hypoxia (HxCO; fractional inspired CO = 0.03-0.05%), which decreases arterial O2 saturation by ~25-40%.The results demonstrate the following. 1) AtTam of 5°C, in both intact andCBD rats, / O2 islarger when Hxam orCO2 is associated withHxCO than with normoxia. At Tam of 25°C, this is also thecase except for CO2 in CBD rats. 2) AtTam of 5°C, the changes in O2 andTc seem to result from additiveeffects of the separate changes induced byHxam,CO2, andHxCO. It is concluded that, inconscious rats, central hypoxia does not depress respiratory activity.On the contrary, particularly when O2 is augmented during acold stress, both / O2during HxCO and the ventilatoryresponses to Hxam andCO2 are increased. The mechanismsinvolved in this relative hyperventilation are likely to involvediencephalic integrative structures. |