Significance of the Adrenal Glands during the Post-natal Development of Thermoregulation in the Rat

The range of environmental temperature within which rats maintain a stable body temperature increases with age1–3, and it is possible that the lack of effect of adrenalectomy on thermoregulation before the sixteenth day after birth4–6 is the result of the relatively very low environmental temperature used (5° C.) at which thermoreGulation fails in very young rats.

Abstract

THE range of environmental temperature within which rats maintain a stable body temperature increases with age1–3. It is therefore possible that the lack of effect of adrenalectomy on thermoregulation before the sixteenth day after birth4–6 is the result of the relatively very low environmental temperature used (5° C.) at which thermoregulation fails in very young rats. In order to test this hypothesis rats were adrenalectomized under cold anæsthesia on the fourth day after birth. One, two and three days after operation their power of thermoregulation was tested as follows: rectal temperature was taken with a thermocouple immediately before the experiment after removal of infant rats from the nest. The animals were then placed in a Bargeton–Krumm–Heller3 respirometer and oxygen consumption was measured at an environmental temperature of 35° C. for 30 min. Then the external temperature was changed to 30° C. at which readings were continued for a further 60 min. Finally, the rectal temperature was again taken.