Central thermal adaptation of lower brain stem units in the guinea-pig.

Cold adaptive changes were found in single units responding to thermal skin stimulation. All units were located in the subcoeruleus region of the lower brain stem. In cold-adapted guinea-pigs (five weeks in ambient temperature of 4 degrees C), the maximum activity of cold-responsive neurones was reduced markedly in comparison with that of cold-responsive neurones in animals adapted to room temperature (ca. 21 degrees C). This decrease may be a neuronal correlate to long-term downward shifts of shivering threshold temperature known to occur within adaptation periods of several weeks in man, as well as in animals.