Level and duration of developmental hyperoxia influence impairment of hypoxic phrenic responses in rats.
Developmental hyperoxia (1-4 wk of 60% O2) causes long-lasting impairment of hypoxic phrenic responses in rats. We hypothesized that shorter or less severe hyperoxic exposures would produce similar changes. Hypoxic phrenic responses were measured in 3- to 5-mo-old, urethane-anesthetized rats exposed to 60% O2 for postnatal day 1 or week 1 or to 30% O2 for postnatal week 1. Whereas 1 day of 60% O2 had no lasting effects (P > 0.05 vs. control), both 1 wk of 60% O2 and 1 wk of 30% O2 decreased adult hypoxic phrenic responses (P < 0.05 vs. control), although the effects of 30% O2 were smaller. Hypoxic ventilatory responses (expressed as the ratio of minute ventilation to metabolic CO2 production) were also reduced in unanesthetized rats (5-10 mo old) exposed to 1 wk of 60% O2 during development (P < 0.05). An age-dependent increase toward normal hypoxic phrenic responses was observed in rats exposed to 1 wk of 60% O2 (P < 0.05), suggesting a degree of spontaneous recovery not observed after 1 mo of 60% O2. These data indicate that long-lasting effects of developmental hyperoxia depend on the level and duration of hyperoxic exposure.
Bavis
R W
RW
Biology Dept., Bates College, Carnegie Science Bldg., 44 Campus Ave., Lewiston, ME 04240, USA. rbavis@bates.edu
Olson
E B
EB
Vidruk
E H
EH
Bisgard
G E
GE
Mitchell
G S
GS
D000375:Aging; D000818:Animals; D018496:Hyperoxia / Q000150:complications* / Q000503:physiopathology*; D000860:Hypoxia / Q000150:complications* / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption; D010791:Phrenic Nerve / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics; D013997:Time Factors