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Hypoxic ventilatory responses in rats after hypercapnic hyperoxia and intermittent hyperoxia
Ryan W Bavis1, Kate E R Russell, Julia C Simons
1Department of Biology, Bates College, 44 Campus Ave., Carnegie Science Hall, Lewiston, ME 04240, USA. rbavis@bates.edu <rbavis@bates.edu>
Respiratory Physiology & Neurobiology
|August 2, 2006
Summary
Perinatal hyperoxia exposure in rats reduces the adult hypoxic ventilatory response. Stimulating chemoreceptors during this period partially preserves this response, suggesting activity-dependent plasticity.
Area of Science:
- Physiology
- Developmental Biology
- Respiratory Science
Background:
- Perinatal hyperoxia, or high oxygen exposure after birth, is known to attenuate the adult hypoxic ventilatory response in rats.
- This effect is potentially mediated by the inhibition of chemoreceptor activity during early life.
- Understanding the mechanisms behind this developmental plasticity is crucial for potential interventions.
Purpose of the Study:
- To investigate whether stimulating chemoreceptors with carbon dioxide (CO2) during hyperoxia or interrupting hyperoxia with normoxia can mitigate the long-term effects of perinatal hyperoxia on the hypoxic ventilatory response.
- To explore the role of activity-dependent mechanisms in hyperoxia-induced developmental plasticity.
Main Methods:
- Rat pups were raised in 60% oxygen for the first two postnatal weeks.
- Experimental groups included sustained hypercapnia (5% CO2), intermittent hypercapnia (alternating 1-h exposures to 0 and 7.5% CO2), and intermittent hyperoxia (alternating 1-h exposures to 21 and 60% O2) during the hyperoxic period.
- Hypoxic ventilatory responses were assessed at 6-10 weeks of age using whole-body plethysmography.
Main Results:
- Rats exposed to intermittent hypercapnia during hyperoxia or intermittent hyperoxia showed significantly greater increases in ventilation-to-metabolism ratio (VE/VO2) in response to hypoxia compared to rats exposed to hyperoxia alone (P<0.05).
- While these responses were improved, they remained lower than those of normoxia-reared control rats.
- A similar, though not statistically significant, trend was observed for rats exposed to sustained hypercapnia during hyperoxia (P=0.053).
Conclusions:
- Activity-dependent mechanisms play a significant role in the developmental plasticity induced by perinatal hyperoxia.
- Interventions that stimulate chemoreceptor activity or interrupt hyperoxia can partially preserve the adult hypoxic ventilatory response.
- Additional mechanisms beyond chemoreceptor activity likely contribute to hyperoxia-induced developmental plasticity.
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