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Baroreflex Modulation During Acute High-Altitude Exposure in Rats

Ana Rosa Beltrán^1,2, Alexis Arce-Álvarez³, Rodrigo Ramirez-Campillo^4,5

¹Departamento de Educación, Facultad de Educación, Universidad de Antofagasta, Antofagasta, Chile.

Frontiers in Physiology

|September 25, 2020

Summary

Acute high-altitude exposure impairs baroreflex (BR) control in rats, leading to reduced parasympathetic activity and autonomic imbalance. This study highlights significant changes in BR function after just 24 hours at high altitude.

Area of Science:

Physiology
Autonomic Nervous System
Cardiovascular Regulation

Background:

Baroreflex (BR) control is essential for maintaining cardiovascular homeostasis, relying on sympathetic and parasympathetic modulation.
Previous research indicates BR control impairment during acute hypobaric hypoxia, but effects of natural high-altitude exposure remain debated.
Understanding autonomic and BR responses to high altitude is crucial for managing physiological adaptations and potential health risks.

Purpose of the Study:

To investigate the impact of acute high-altitude exposure on sympathetic and parasympathetic modulation of baroreflex control in rats.
To assess changes in heart rate variability (HRV) and BR function following simulated natural hypoxic conditions.

Main Methods:

Male Sprague Dawley rats were divided into Sea-Level and High-Altitude (3,270 m) groups.
Baroreflex control was assessed using phenylephrine (Phe) and sodium nitroprusside (SNP) with sigmoidal analysis.
Autonomic modulation was evaluated via frequency-domain heart rate variability (HRV) and spectral non-stationary analysis during drug administration.

Main Results:

High-altitude exposure induced parasympathetic withdrawal (reduced high-frequency HRV) and sympathoexcitation (increased low-frequency HRV) compared to sea-level controls.
Baroreflex function showed a significant decrease in curvature and blunted parasympathetic bradycardic responses to phenylephrine.
Non-stationary HRV analysis revealed reduced parasympathetic activation in the high-altitude group.

Conclusions:

Acute exposure to high altitude significantly impairs baroreflex control and autonomic modulation in rats.
The observed effects are characterized by parasympathetic withdrawal and sympathoexcitation after 24 hours of high-altitude exposure.
These findings underscore the vulnerability of autonomic and baroreflex regulation to rapid environmental changes at high altitudes.

Keywords:

autonomic nervous system baroreceptors baroreflex parasympathetic nervous system sympathetic nervous system

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