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Atelier de Physiologie Respiratoire, Faculté de Médecine Saint-Antoine, 75012 Paris, France
Received 8 May 1996; accepted in final form 14 March 1997.
Gautier, Henry, Cristina Murariu, and Monique Bonora.
Ventilatory and metabolic responses to ambient hypoxia or
hypercapnia in rats exposed to CO hypoxia. J. Appl. Physiol.
83(1): 253-261, 1997.
We have investigated at ambient
temperatures (Tam) of 25 and
5°C the effects of ambient hypoxia
(Hxam; fractional inspired O2 = 0.14) and hypercapnia
(fractional inspired
CO2 = 0.04) on ventilation (
),
O2 uptake
(
O2), and
colonic temperature (Tc) in 12 conscious rats before and after carotid body denervation (CBD). The
rats 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) At
Tam of 5°C, in both intact and
CBD rats,
/
O2 is
larger when Hxam or
CO2 is associated with
HxCO than with normoxia. At Tam of 25°C, this is also the
case except for CO2 in CBD rats. 2) At
Tam of 5°C, the changes in
O2 and
Tc seem to result from additive
effects of the separate changes induced by
Hxam,
CO2, and
HxCO. It is concluded that, in
conscious rats, central hypoxia does not depress respiratory activity.
On the contrary, particularly when
O2 is augmented during a
cold stress, both
/
O2
during HxCO and the ventilatory
responses to Hxam and
CO2 are increased. The mechanisms
involved in this relative hyperventilation are likely to involve
diencephalic integrative structures.
thermoregulation; chemoreceptors; hypoxic hypometabolism; control of breathing; shivering; carbon monoxide
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