Effects of training to heat and cold in the neonatal period on the body temperature response of adult rats.
Forty infant albino rats were divided into four groups. Group I was exposed 15 minutes daily for one month to a dry ambient temperature of +40 degrees C +/- 1 degree C and group II was exposed to 10 - 20 minutes daily to an ambient temperature of - 10 degrees C +/- 2 degrees C. Groups III and IV served as controls. When they had grown adult the animals of the experimental groups were exposed once to the temperature to which they had been trained. Basal temperature was measured and the temperature curve was recorded for 30 - 60 minutes after removing the animals from the hot or cold environment. Values were compared with those found in the control groups. The statistically processed results show that daily exposure to heat and cold does not influence the basal temperature of adult animals but impairs functional tests and resistance to limit temperature exposure. Thus, compared with controls, animals trained to cold developed a significantly lower hypothermia, whereas the animals trained to heat responded by a temperature rise equalling in height and duration that of controls when they were exposed to +40 degrees C, but displayed a significantly poorer resistance to lethal hyperthermic shock. The paper ends with a discussion of the mechanisms involved in these late effects, which are probably due to the impaired maturation of the pituitary-adrenal system in the neonatal period.
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001833:Body Temperature Regulation; D003080:Cold Temperature; D004781:Environmental Exposure; D006358:Hot Temperature; D051381:Rats