Using thermal preference to understand mouse thermal biology.

The ability to tightly regulate and maintain a warm core body temperature (Tb) is a defining characteristic of homeotherms. Moving to a thermally preferred place is an energetically efficient first-line thermoregulatory mechanism. We optimized a mouse binary thermal preference assay, selecting floor plate temperatures of 38°C vs 25°C for males and 39°C vs 30°C for females as having no baseline preference. Warm preference was increased in females, by fasting, and with age. Genetic manipulations that increased warm preference included ablation of uncoupling protein 1 (Ucp1) or of all four adenosine receptors (Adora1, Adora2a, Adora2b, Adora3). Ablation of estrogen receptor α (Esr1) reduced the preference for the warmer side in females but had no effect on preference in males. Mice treated with the β3 adrenergic receptor agonist CL-316243 or the adenosine receptor 3 agonist MRS5698 sought the cooler surface. Thermal preference assays complement the measurement of Tb, providing information about whether a change in Tb reflects a new target or setpoint Tb caused by the intervention, or if the mouse is trying to maintain an unchanged Tb. Thermal preference can be more sensitive than baseline Tb for detecting changes in thermal physiology.