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The vestibulo-autonomic function viewed from cardiac responses in centrifuged monkeys
H Satake1, K Matsunami, H Miyata
1Department of Neurophysiology, Gifu University, School of Medicine, Japan.
Acta Oto-Laryngologica. Supplementum
|January 1, 1991
Summary
The vestibular system significantly influences autonomic responses, affecting heart rate and stroke volume during G-force exposure. Lacking vestibular input alters these cardiac adjustments to acceleration.
Area of Science:
- Cardiovascular physiology
- Neuroscience
- Autonomic nervous system function
Background:
- The vestibular system plays a crucial role in maintaining autonomic stability.
- Understanding the interplay between vestibular input and cardiac regulation under stress is vital.
Purpose of the Study:
- To investigate the role of vestibular function in modulating autonomic responses to G-force accelerations.
- To compare cardiac parameter changes (heart rate and stroke volume) in intact versus bilaterally labyrinthectomized monkeys under +Gz and -Gx accelerations.
Main Methods:
- Cardiac parameters (heart rate and stroke volume) were monitored in anesthetized intact and bilaterally labyrinthectomized monkeys.
- Monkeys were subjected to sustained +Gz (up to +4Gz) and -Gx (up to -8Gx) accelerations for 1,000 seconds.
- Changes in heart rate and stroke volume were analyzed to assess vestibulo-autonomic function.
Main Results:
- Vestibular input significantly modulated heart rate responses to +Gz acceleration; intact monkeys showed a 30% HR increase at +3Gz, while labyrinthectomized monkeys exhibited a decrease.
- Stroke volume significantly decreased in both groups under +3Gz, with a more pronounced reduction in labyrinthectomized monkeys.
- +Gz accelerations beyond +4Gz induced severe cardiac dysfunction in both groups.
- -Gx accelerations caused slight heart rate increases, with less pronounced changes in labyrinthectomized monkeys.
- Stroke volume showed varied responses to -Gx, with differences noted between intact and labyrinthectomized monkeys at higher amplitudes (-6Gx and -8Gx).
Conclusions:
- Vestibular input is a critical modulator of autonomic cardiovascular control during G-force exposure.
- Labyrinth removal significantly alters cardiac autonomic regulation, particularly under positive Gz stress.
- The findings highlight the vestibular system's importance in maintaining cardiovascular homeostasis during acceleration stress.