Slow recovery of impaired phrenic responses to hypoxia following perinatal hyperoxia in rats

• Published in: The Journal of physiology Vol. 511; no. 2; pp. 599 - 603
• Main Authors: Liming Ling, E Burt Olson, Jr, Edward H Vidruk, Gordon S Mitchell
• Format: Journal Article
• Language: English
• Published: Oxford, UK The Physiological Society 01-09-1998; Blackwell Science Ltd; Blackwell Science Inc
• Subjects: Animals; Animals, Newborn - physiology; Blood Gas Analysis; Chemoreceptor Cells - physiology; Hyperoxia - physiopathology; Hypoxia - physiopathology; Male; Phrenic Nerve - physiopathology; Rapid Report; Rats; Rats, Sprague-Dawley; Space life sciences; Vagotomy
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.1998.599bh.x

Previous studies demonstrated that both ventilatory and phrenic nerve responses to acute hypoxia are greatly attenuated in
adult rats (3–5 months old) previously exposed to 1 month of perinatal hyperoxia (60% O 2 ; perinatal treated rats). The present study tested the hypothesis that this functional impairment recovers spontaneously
with advancing age in perinatal treated rats.
Hypoxia-induced chemoreflexes were examined by measuring integrated phrenic responses to strictly controlled isocapnic hypoxia
in urethane-anaesthetized, vagotomized, paralysed and ventilated rats at different ages.
At 50 mmHg P a,O 2 (arterial O 2 partial pressure), the hypoxia-induced increase in minute phrenic activity was significantly attenuated in both 3- to 5-month-old
(166 ± 15% of baseline) and 6-month-old (130 ± 17%) perinatal treated rats, relative to 3- to 6-month-old, untreated control
rats (279 ± 28%; both P < 0.05). However, at 40 mmHg P a,O 2 , the hypoxic minute phrenic activity response was attenuated only in 3- to 5-month-old (154 ± 33%), but not 6-month-old (232
± 33%) perinatal treated rats versus control rats (293 ± 30%).
The minute phrenic activity response to hypoxia was not significantly different between geriatric perinatal treated rats (14–15
months) and untreated geriatric control rats at either 50 mmHg (treated: 250 ± 20% versus control: 274 ± 23%) or 40 mmHg P a,O 2 (treated: 292 ± 19% versus control: 315 ± 36%).
These data suggest that partial spontaneous recovery may occur in 6-month-old perinatal treated rats and that full recovery
occurs by 15 months of age.