ROLE OF THE AUTONOMIC NERVOUS SYSTEM AND HYPOXIA IN THE CARDIAC CONTROL OF SQUIRREL MONKEYS EXPOSED TO 200+GX FOR 200 SECONDS.
Final rept. 16 Oct 65-15 Sep 66,
SPACE/DEFENSE CORP BIRMINGHAM MI
Pagination or Media Count:
In a continuing investigation into cardiac control during acceleration, pharmacologic denervation of the heart was accomplished in squirrel monkeys with hexamethonium chloride .005 mggm, and the animals dynamically stressed on an unique articulated centrifuge. Electrocardiographic data during centrifugation revealed a significantly higher heart rate in treated animals compared to a placebo group of animals. When the electrocardiograms during acceleration of the present hexamethonium studies were compared to those in previous atropine studies a significant difference was seen atropinized animals had higher heart rates. Positive chronotropic action of the sympathetic nervous system, extreme parasympathetic tone to the heart and intrinsic cardiac inhibition have been demonstrated during high G acceleration in squirrel monkeys. It was necessary to establish the role of oxygen. Accordingly, squirrel monkeys were hyperoxygenated prior to and during the standardized accelerative dose. Profound changes in cardiac performance and increased survivability were observed. When animals were hyperoxygenated, the extreme bradycardia normally associated with acceleration in this force range did not occur some animals actually experienced tachycardia. Survivability was high.
- Anatomy and Physiology
- Stress Physiology