Abstract
Rats reared in hyperoxia exhibit a sustained (vs. biphasic) hypoxic ventilatory response (HVR) at an earlier age than untreated, control rats (Bavis et al., J Appl Physiol 109:796–803, 2010). Since ventilatory decline in the late phase of the biphasic HVR is linked to inhibitory modulation of respiratory neurons in the CNS, we hypothesized that hyperoxia‐treated rats would exhibit less CNS‐mediated hypoxic ventilatory depression. We used the P2X receptor antagonist PPADS (125 mg kg−1, i.p.) to “chemically denervate” the carotid bodies (CB) of 4–5‐day old rats reared in 21% O2 (Control) or 60% O2 (Hyperoxia). PPADS had no effect on the hypercapnic ventilatory response (7% CO2) but abolished the early, carotid body‐mediated phase of the HVR (12% O2) in Control rats. Control rats showed a progressive decline in ventilation during hypoxia (−28±4% by 10 min, n=18), but this effect was absent in Hyperoxia rats (−2±4%, n=18; P<0.001 vs. Control). We conclude that CNS hypoxia depresses ventilation in young, neonatal rats independent of CB activation. Moreover, our data suggest that hyperoxia alters the development of CNS pathways that modulate the hypoxic ventilatory response.
Published Version
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