Fig. 1.

Experimental design. A: representative trace of a ground squirrel's core body temperature during the hibernation season, showing the regular fluctuations between torpor and interbout arousals (IBAs) over ∼1 mo. This trace was obtained from a surgically implanted transmitter. Luzindole or vehicle was administered toward the end of a torpor bout, as illustrated by the black arrow. B: physiological parameters of arousal are shown, with heart rate [in beats/min (BPM)] in gray and core body temperature in black. The 2 experimental endpoints for the Hibernating^TR animals are shown, midarousal at 20°C and full arousal at 37°C. The experimental endpoint for the Hibernating^MT animals is also approximately midarousal.