Fig. 1

Temporal change in rectal temperature during induction of hypothermia by isoflurane inhalation and cooling in rats. Rats anesthetized with isoflurane were cooled by placing them in a cold room kept at 4 °C, and changes in rectal temperature were measured. a When the isoflurane inhalation was stopped at 27.5 °C, rats showed shivering spontaneously and rectal temperature increased. b When isoflurane inhalation was stopped at 25 °C, rectal temperature recovered spontaneously in three of five rats, whereas rectal temperature of the other two rats continuously decreased and eventually reached 15 °C. c Isoflurane concentration was kept at 2% until rectal temperature reached 27.5 °C and was then reduced to 1%, and then isoflurane inhalation was stopped at 22.5 °C. Using this procedure, the rectal temperature continuously decreased and reached 15 °C. Changes in rectal temperature in each rat (n = 5 for panels A and B, n = 6 for panel C) are shown