Accession Number : AD0473108


Title :   INVESTIGATIONS IN THE CONTROL OF THE ACCELERATIVELY STRESSED HEART PHASE I: ROLE OF THE VAGUS IN REGULATING THE CARDIAC RESPONSES OF SQUIRREL MONKEYS DURING CENTRIFUGATION AT 200 +GX FOR 200 SECONDS.


Descriptive Note : Final rept. 15 May-15 Oct 65,


Corporate Author : SPACE/DEFENSE CORP BIRMINGHAM MI


Personal Author(s) : Pinc, Bruce W ; Life, Jeffry S


Report Date : 22 Oct 1965


Pagination or Media Count : 14


Abstract : Bradycardia has been observed in subjects exposed to a variety of accelerative environments, and parasympathetic causation is usually implicated but has not been proven. To determine the role of parasympathetic cardiac innervation in accelerative bradycardia, atropine sulfate (o.5mg/kg) was given intravenously to seven squirrel monkeys and a placebo to nine control animals. Each animal was exposed to 200 +Gx (200 seconds dwell, with onsets and offsets of 25 G/sec.) on a unique articulated centrifuge. Analysis of heart rate data from electrocardiograms revealed: (1) no significant difference between control and atropinized rates before acceleration; (2) highly significant differences between the two groups' rates in the first 50 seconds, with the control subjects demonstrating a rate reduction of 89.6% below baseline in the first 5 seconds; (3) a gradual rate reduction in the atropinized animals; and (4) no significant difference in rates during the last 150 seconds with both final rates less than half of baseline values. The results show that parasympathetic outflow causes accelerative bradycardia. The discussion suggest four alternative causes for the parasympathetic discharge. (Author)


Descriptors :   *ACCELERATION TOLERANCE , HEART , STRESS(PHYSIOLOGY) , NERVES , MONKEYS , PATHOLOGY , PULSE RATE , AUTONOMIC NERVOUS SYSTEM , ATROPINE , LABORATORY ANIMALS , CENTRIFUGES , ELECTROCARDIOGRAPHY


Distribution Statement : APPROVED FOR PUBLIC RELEASE