Abstract
The animal model used the most frequently for understanding the mechanisms of adaptation
to cold in humans has been the rat. It has been established that rats kept in the
cold for a few weeks stop shivering while preserving a normal internal temperature
because of an enhanced thermogenic capacity of the brown adipose tissue (BAT) mediated
by the sympathetic nervous system. Studies on groups of humans exposed to cold have
shown that shivering is also attenuated but without compensatory increased in heat
production possibly because of non-significant contribution of the BAT. However when
humans and laboratory animals are exposed repeatedly to short severe cold evidence
for adaptation has been described. This adaptation is not metabolic; instead it is
related to the phenomenon of habituation. When exposed to a novel stress such as cold,
the alarm reaction is initiated as evidenced by the activation of the sympathetic
nervous system which opposes the stressing situation. However with time, when it is
realized that the normal functioning of the body is not endangered the responses are
attenuated and enhanced tolerance is observed. This type of adaptation was observed
in Eskimos, fishermen, outdoor workers, etc.
Key words
Cold - adaptation - habituation - shivering
