Effect of Estrogen Status on Circadian Core and Tail Skin Temperature Rhythms in Female Mice

Abstract

Body temperature in women is altered by changes in circulating gonadal steroids during the menstrual cycle and estrogen withdrawal after menopause. In contrast to numerous studies in the rat, there is limited information on the effects of estrogen on body temperature regulation in the mouse. The present studies were designed to measure circadian rhythms of core temperature (TCORE) and tail skin temperature (TSKIN) in the mouse. In experiment 1, female mice were implanted with an intraperitoneal temperature probe to measure TCORE and a temperature probe was attached to the tail to measure TSKIN. Daily vaginal smears were taken to assess estrous cycle stage and TCORE and TSKIN were measured continuously for 14 days. In experiment 2, temperature measurements were recorded for ovariectomized (OVX), and low and high estrogen (E2) replaced animals. We report circadian rhythms of TCORE and TSKIN were not affected by day of the estrous cycle. There was also no significant effect of estrogen replacement on TSKIN during the dark phase, regardless of the E2 dose. However, low and high E2 significantly decreased TCORE in OVX mice during the light phase. These studies reveal a significant species difference in estrogen modulation of thermoregulation in the rat and mouse.