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Airway hyperreactivity produced by short-term exposure to hyperoxia in neonatal guinea pigs
S R Schulman1, A T Canada, A D Fryer
1Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Insights
Neonatal hyperoxia exposure, a treatment for respiratory distress, can cause long-term airway hyperreactivity in infants. This study shows guinea pigs exposed to oxygen develop persistent airway hyperreactivity, offering a model to study this condition.
Area of Science:
- Neonatal physiology
- Respiratory medicine
- Pulmonary research
Background:
- Airway hyperreactivity is a known long-term complication of bronchopulmonary dysplasia (BPD).
- Improved survival rates for very low-birth weight infants are linked to an increased incidence of BPD and childhood asthma.
- Hyperoxia, used to treat respiratory distress syndrome, is implicated in BPD development.
Purpose of the Study:
- To investigate the role of hyperoxia in inducing airway hyperreactivity.
- To establish a suitable animal model for studying hyperoxia-induced airway hyperreactivity.
Main Methods:
- Neonatal guinea pigs (4 days old) were exposed to 70% oxygen or air for 96 hours.
- Airway responsiveness to acetylcholine (ACh) was measured 2 and 9 days post-exposure.
- Mechanisms involving neuronal acetylcholinesterase and M2 muscarinic receptors were examined.
- Antioxidant protection differences were compared between guinea pigs and rat pups.
Main Results:
- Hyperoxia exposure led to persistently increased airway reactivity in neonatal guinea pigs.
- The observed airway hyperreactivity was not due to inhibition of neuronal acetylcholinesterase or M2 muscarinic receptors.
- Differences in antioxidant protection did not explain the heightened response in guinea pigs compared to rats.
Conclusions:
- Neonatal hyperoxia exposure induces persistent airway hyperreactivity.
- The neonatal guinea pig is a viable model for studying the mechanisms of hyperoxia-induced airway hyperreactivity.
- The mechanism differs from ozone-induced hyperreactivity and does not involve specific neuronal pathways or antioxidant differences observed in rats.
Abstract:
Airway hyperreactivity is recognized as one of the long-term sequelae of bronchopulmonary dysplasia (BPD). Due to the improved care and prognosis of very low-birth weight infants, the incidence of BPD is increasing. There are data that suggest the increased survival of premature infants may be associated with the observed increased incidence of childhood asthma. The hyperoxia received as part of the treatment of respiratory distress syndrome is believed to be partly if not completely responsible for BPD. To gain insight into the potential role that hyperoxia might play in producing airway hyperreactivity, 4-day-old guinea pig pups were exposed to 70% oxygen or air for 96 h, and airway responsiveness to acetylcholine (ACh) was assessed both 2 and 9 days after the completion of the hyperoxia exposures. Unlike ozone, the mechanism for the persistently increased airway reactivity is not related either to the inhibition of neuronal acetylcholinesterase or inhibition of the neuronal M2 muscarinic receptor. A difference in antioxidant protection did not account for the increased response of the neonatal guinea pigs compared with hyperoxia-exposed rat pups. These data support the usefulness of the neonatal guinea pig as a model to study the mechanism responsible for hyperoxia-induced airway hyperreactivity.