BIO 4120 Lecture Notes - Lecture 3: Peromyscus, Acclimatization, Carotid Body

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13 Oct 2017
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Summary of Focal Paper 3
Title: Control of breathing and ventilatory acclimatization to hypoxia in deer mice native to high
altitudes
Authors: C.M Ivy and G.R. Scott
Take home message:
The goal of this experiment was to acquire a better understanding of the physiological
specializations that aid high altitude populations of deer mice (Peromyscus mice) cope
with O2 limitations
This was achieved through comparison of the control of breathing and heart rate by
hypoxia between low and high populations of deer mice. Highlanders had a more
effective breathing pattern characterized by deeper but less frequent breaths during acute
hypoxia compared to lowlanders. Highlanders maintained a consistently higher heart
rates than lowlanders during acute hypoxia
Ventilatory acclimatization to hypoxia (VAH) was observed in lowlanders but not in
highland deer mice; however high rates of alveolar ventilation and respiratory O2 uptake
without significant enlargement of the carotid bodies, which is typical of VAH, was
observed in highland deer mice
Key findings:
Figure 1. High-altitude deer mice exhibited a more effective breathing pattern than low-altitude deer mice,
characterized by deeper but less frequent breaths during acute hypoxia challenge
Experimental Approach
Deer mice (Peromyscus maniculatus) that inhabit high altitudes and congeneric mice that inhabit
low altitudes (Peromyscus leucopus) were bred in captivity at sea level. Their offsprings were
raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa, simulating
hypoxia at ~4300 m) for 5 months. Responses to acute hypoxia were then measured during
stepwise reductions in inspired O2 fraction.
Strength and Weaknesses
This study provided more insight on the mechanisms underlying the changes in the control of
breathing and was also one of the few studies to do so by comparing highlanders and lowlanders
acclimated to both normoxic and hypoxic environments. However stress due to the specimens
being placed in captivity for such a long period of time could have altered VO2 readings, which
in turn could have altered their overall results.
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