Evolved changes in breathing and CO₂ sensitivity in deer mice native to high altitudes

Area of Science:

• Physiology
• High-altitude adaptation
• Respiratory control

Background:

• High-altitude environments present challenges due to low oxygen levels (hypoxia).
• Understanding physiological specializations for hypoxia coping is crucial for high-altitude adaptation research.
• Deer mice (Peromyscus maniculatus) from high altitudes and white-footed mice (P. leucopus) from low altitudes were used to study these adaptations.

Purpose of the Study:

• To investigate the control of breathing by oxygen (O2) and carbon dioxide (CO2) in high-altitude native deer mice.
• To uncover physiological specializations that enable coping with hypoxia in high-altitude environments.
• To compare ventilatory acclimatization to hypoxia (VAH) between high-altitude and lowland mice.

Main Methods:

• Captive breeding of highland deer mice and lowland white-footed mice at sea level.
• Acclimation of first and second-generation progeny to normoxia or hypobaric hypoxia (simulating ~4,300 m).
• Assessment of ventilatory responses to hypoxic and hypercapnic challenges.

Main Results:

• Lowland mice exhibited ventilatory acclimatization to hypoxia (VAH), with enhanced hypoxic ventilatory response after acclimation.
• Hypoxia acclimation had no significant effect on breathing in either generation of highlanders.
• Both highlanders and lowlanders showed similar increases in CO2 sensitivity after hypoxia acclimation.

Conclusions:

• Attenuation of VAH appears to be an evolved trait in high-altitude deer mice, persisting across generations in captivity.
• Highland deer mice possess evolved high rates of alveolar ventilation that remain stable despite chronic hypoxia exposure.
• Preserved ventilatory sensitivity to CO2 in highlanders is maintained despite adaptations to hypoxia.