Prenatal hyperoxia blunts the hypoxic ventilatory chemosensitivity of the 1-day old chicken hatchling

Area of Science:

• Physiology
• Developmental Biology
• Respiratory Medicine

Background:

• Prenatal hypoxia is known to impair the newborn's ventilatory response to hypoxia.
• This impairment is thought to stem from developmental disturbances in peripheral chemoreceptors.
• The effect of prenatal hyperoxia on chemoreceptor development and function remains less understood.

Purpose of the Study:

• To investigate the impact of prolonged prenatal hyperoxia on the ventilatory (V˙(E)) response to hypoxia in newborn chickens.
• To determine if prenatal hyperoxia affects respiratory responses to hypercapnia.
• To explore the potential role of carotid body dysfunction in observed respiratory changes.

Main Methods:

• Chicken hatchlings were exposed to 40% or 60% O2 during the final week of incubation and hatching.
• Ventilatory patterns and responses to hypoxia (10% and 15% O2) and hypercapnia were measured using a modified barometric technique.
• Control groups were incubated under normoxic conditions.

Main Results:

• Prenatal hyperoxia significantly reduced the V˙(E) response to 10% O2 by over 50% compared to controls.
• Hypoxic oxygen consumption (V˙(O2)) drop was more pronounced in hyperoxia-exposed hatchlings.
• The V˙(E) response to hypercapnia was largely unaffected, indicating no significant mechanical limitations to breathing.

Conclusions:

• Sustained prenatal hyperoxia, similar to prenatal hypoxia, impairs the newborn's ventilatory response to hypoxia.
• These findings suggest that altered prenatal oxygenation impacts carotid body function.
• The study supports the view that prenatal oxygen exposure is critical for normal chemoreceptor development and respiratory control.