‘Free roaming’ in the albino rat and its effect on restraint hypothermia

¹ National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland and Department of Anatomy, Howard Medical School, Washington, D. C.

‘Adaptation’ to a large environment increased the resistance of young adult female (175–225 gm) Sprague-Dawley rats to restraint hypothermia. Two changes may have occurred in the ‘free roaming’ rats which rendered them less susceptible to restraint hypothermia: 1) emotional adaptation to the changing stimuli of the ‘free roaming’ state may have lessened the emotional stress produced by restraint which would have reduced the hypothermic response (Am. J. Physiol. 79: 343, 1954), 2) a possible cross-resistance produced by adaptation to the nonspecific stresses involved in the ‘free roaming’ state which would have inhibited restraint induced hypothermia (J. Appl. Physiol. 8: 661, 1956).