AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 3 334-R338, Copyright © 1983 by American Physiological Society
Photoperiodic regulation of body mass, food intake, and reproduction in meadow voles
J. Dark, I. Zucker and G. N. Wade
Adult male voles were maintained for 10 wk in long or short photoperiods
(14 or 10 h of light/day). A third group of animals housed in the long
photoperiod was implanted with capsules containing melatonin. Body weight
and food intake were measured weekly; various tissues were weighed and
analyzed at the time of autopsy. After 10 wk, voles in the short
photoperiod weighed 20% less and consumed 30% less food than those housed
in the long photoperiod. Total body water and lean body mass were reduced
in the short-day animals, although the size of the brown adipose tissue was
not affected. White adipose tissue lipoprotein lipase (LPL) activity was
markedly reduced in the short-day voles who also manifested gonadal
regression and suppression of spermatogenesis. Melatonin mimicked the
effects of short photoperiods on LPL activity and on lean body mass; other
parameters for melatonin-treated animals were intermediate between those of
untreated long- and short-day voles. We hypothesize that winter weight
losses experienced by meadow voles in the field are mediated by decreases
in the duration of the daily photophase and that the reduction in body mass
permits overwintering voles to reduce their energy requirements and the
amount of time devoted to foraging. At least part of the seasonal decline
in body mass appears due to a decrease in gonadal hormone secretion.
