Fig. 1.
Typical core body temperature (Tb), activity, and heart rate response to fasting in a C57BL/6J female adult mouse. This mouse was implanted with a telemeter that detects core Tb (black line in A), activity (gray line in A), and electrical activity of the heart, from which heart rate was derived (B). The tracing spans 48 h, with the dark phases noted in B. Ambient temperature (Ta) was 19°C over both days. The mouse was fasted at the beginning of the dark phase of the second 24-h period. This mouse experienced a very shallow torpor bout ∼6 h after the initiation of the fast, as marked by the white arrow in B, and a much deeper bout a few hours later, as marked by the black arrow in part B.