Brown fat thermogenesis and cardiac rate regulation during cold
challenge in infant rats.
Blumberg, Mark S., Greta Sokoloff, & Robert F. Kirby.
Department of Psychology, The University of Iowa, Iowa City, Iowa
52242
APStracts 3:0425R, 1996.
Infants rats depend upon heat production by brown adipose tissue (BAT)
during cold challenge. Although it has been suggested that BAT
thermogenesis protects the heart in the cold, the relationship of BAT
activation to cardiac rate has not been directly examined. In the
first experiment, the cardiac rate of 2- and 7-8-day-old rat pups was
monitored during moderate and extreme cold challenge. Pups at both
ages maintained cardiac rate during moderate cold challenge while BAT
thermogenesis was increasing. In contrast, cooling to air
temperatures where BAT thermogenesis could increase no further
resulted in pronounced bradycardia. In the second experiment,
ganglionic blockade was used to eliminate BAT heat production and
autonomic control of the heart in 7-8-day-olds. Blockade suppressed
BAT thermogenesis in the cold and led to pronounced decreases in
interscapular temperature and cardiac rate. These data suggest that
cardiac rate in infant rats is modulated both by the autonomic
nervous system and BAT thermogenesis.
Received 12 July 1996; accepted in final form 23 October 1996.
APS Manuscript Number R399-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996