We previously found that
estrous cycle oscillations in food hoarding and sexual motivation are masked in
females housed in isolation at 22ºC with unlimited food. In these
females, food hoarding was low and sexual motivation high throughout the four-day estrous cycle, whereas, in
food-limited females, high levels of sexual motivation were restricted to the
periovulatory day, and food hoarding was elevated on the nonestrous days. To
determine whether cold ambient temperature has the same effects, groups of hamsters were fed ad libitum while they were housed at
either 5oC (cold-housed) or 22oC (warm-housed) and tested
for sex and ingestive behavior for 90 min on each day of the estrous cycle. Estrous
cycle oscillations in food hoarding (but not food intake) were amplified in
cold-housed females. Similar to cold-housed females, a group of warm-housed females
provided with access to running wheels also showed high levels of sexual
motivation restricted to the periovulatory day. Unlike cold-housed females, however,
those warm-housed with running wheels showed low levels of food hoarding and significantly
elevated levels of food intake. Food limitation, cold housing, and access to
wheels had no significant effect on plasma estradiol or progesterone
concentrations, but significantly decreased gonadal white adipose tissue pad
weight and plasma leptin concentrations. Behavioral responsiveness
to low gonadal steroid concentrations is increased by decreased energy intake, or
increased energy expenditure on thermogenesis or exercise. Funded by NSF grant IOS-1257876.