Journal of Applied Physiology, Vol 49, Issue 6 923-929, Copyright © 1980 by American Physiological Society
Changes in beta-adrenergic responsiveness of rats during chronic cold exposure
C. C. Barney, M. J. Katovich, M. J. Fregly and P. E. Tyler
Administration of isoproterenol (50 micrograms/kg sc) to rats that had been
exposed to cold (6 degrees C) for 10, 15, and 25 days was accompanied by a
greater increase in tail skin and colonic temperatures than in controls
kept at 25 degrees C. Administration of isoproterenol (8 micrograms/kg sc)
to cold-treated rats (1, 3, 5, 7, 14, and 28 days) increased heart rates
above that of controls. However, resting unstimulated heart rates of
cold-treated rats were also increased above that of controls after 1, 3, 5,
and 7 days of cold exposure but were not different from controls after 14
and 28 days. Cold exposure also led to time-dependent increases in the
weights of heart, adrenals, and interscapular brown fat. Thus, chronic
exposure of rats to cold is accompanied by an increase in responsiveness of
both heart rate and tail skin and colonic temperatures to beta-adrenergic
stimulation. The results also suggest that increases in responsiveness to a
beta-adrenergic agonist may not occur at the same time for the different
beta-adrenergic-mediated metabolic and cardiovascular responses in
cold-treated rats.
