Fig. 2

Changes in heartbeat during induction of deep hypothermia. a For each rat, heart rate was plotted against rectal temperature (n = 6). The heart rate declined concomitantly with the decrease in rectal temperature. b Representative ECG tracings that were recorded before induction of hypothermia (a) at rectal temperatures of 25 °C (b) and 15 °C (c). Regular sinus rhythm was fundamentally maintained, and no abnormal sign was recorded on an ECG while the rectal temperature was decreasing