AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 1 84-R88, Copyright © 1984 by American Physiological Society
Gonadal and photoperiodic control of seasonal body weight changes in male voles
J. Dark and I. Zucker
After 15 wk in a short photoperiod (10 h of light/day), adult male voles
weighed 25% less and consumed 33% less food than did voles in a long
photoperiod (14 h light/day). Neither body weight nor food intake differed
among long- and short-day castrated voles. After 19 wk, castrated long-day
voles weighed less than did intact animals. Voles reduced their body weight
during the first 15 wk in the short photoperiod and increased their body
mass during the succeeding 15 wk. Body mass of short-day voles was
positively correlated with combined testes weight. Voles in the short
photoperiod collected less nesting material than did their long-day
counterparts at week 31. Pelage characteristics at week 32 were not
affected by castration or by photoperiod. We conclude that the decreased
body mass of male voles during the late summer, fall, and early winter
reflects a decrease in circulating levels of testicular hormones; gonadal
recrudescence and increased circulating androgen levels are in part
responsible for the subsequent seasonal increase in body weight. Part of
the increased body mass in late winter in field populations or in
laboratory voles after 15 wk in the short photoperiod is independent of the
resumption of gonadal activity. Fluctuations in neural and endocrine
processes, rather than availability of food, are the principal factors
underlying seasonal changes in energy balance.
