AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 3 563-R567, Copyright © 1993 by American Physiological Society
Energy balance in pregnant hamsters: a role for voluntary exercise?
A. J. Bhatia and G. N. Wade
Neuroscience and Behavior Program, University of Massachusetts, Amherst 01003.
During pregnancy or after experimental manipulations of ovarian hormone
levels, Syrian hamsters exhibit changes in energy balance and body fat
content without modifying their food intake. The present experiments
determined whether fluctuations in voluntary exercise play a role in these
changes in energy balance, as they appear to do in other species. As
expected, pregnant hamsters maintained a constant level of food intake and
lost approximately 40% of their body fat. These animals did not show the
abrupt decrease in activity after mating that is seen in rats. Instead,
they maintained their high, premating level of running wheel activity until
the last 3 days of pregnancy. Similarly, ovariectomy and replacement
therapy with estradiol or estradiol+progesterone caused substantial changes
in energy balance in the absence of significant changes in food intake or
running wheel activity. These findings indicate that, unlike rats, Syrian
hamsters do not exhibit substantial changes in voluntary exercise during
pregnancy or in response to manipulations of ovarian steroid levels.
Therefore, neither changes in food intake nor in voluntary exercise play
any important role in the pregnancy- or steroid-induced changes in energy
balance in Syrian hamsters.
