Rats were subjected to a treadmill running that was interrupted at three different moments: (1) at the early phase, when minimal heat dissipation occurred due to tail vasoconstriction and the tail skin temperature (T<sub>skin</sub>) reached its nadir; (2) at the steady-state phase, when both the T<sub>skin</sub> and core body temperature (T<sub>core</sub>) plateaued at a high level (~ 20 min); and (3) at fatigue, when T<sub>core</sub> and T<sub>skin</sub> were still elevated. c-Fos expression in the medial and ventromedial preoptic areas (mPOA and vmPOA), median preoptic nucleus (MnPO), paraventricular and supraoptic nucleus (PVN and SON), and septohypothalamic nucleus (SHy) was determined.