Anatomy & Physiology: Current Research
Open Access

Abstract

Daily Changes of Body Temperature and Heart Rate are Modulated after Estradiol Depletion in Female Rats

Shuri Marui, Yuki Uchida and Kei Nagashima

We assessed the influence of estradiol depletion on daily changes of core temperature, spontaneous activity, and heart rate in female rats. In addition, we evaluated the effects of estradiol depletion on β-adrenoreceptors (AR) in the heart and plasma norepinephrine. Rats were bilaterally ovariectomized and two tubes that either contained estradiol (E2) or were empty (C) were placed subcutaneously in each rat’s abdominal cavity. The tubes were removed 10 days later. Core temperature and heart rates were continuously measured by biotelemetry before and 1, 7, and 21 days after removal of the tubes (PRE and Days 1, 7, and 21). Core temperature was higher in the E2 group than in the C group at 2330–0130 h on PRE and on Days 1–21. Core temperature exceeded the PRE level in the E2 group at 1430–1830 h on Days 1–21. Heart rates were lower in the E2 group than the C group throughout the day on PRE and on Days 1–21. β1-AR expression and plasma norepinephrine levels were lower in the E2 group than in the C group on PRE. Heart rates in the E2 group exceeded the PRE level on Days 1–21. We concluded that the depletion of plasma estradiol modulates daily changes of core temperature and heart rate, an effect that occurs immediately after the estradiol depletion. In addition, plasma norepinephrine and β-AR in the heart may at least partially affect heart rate.