Physiological and behavioral reactions to repeated tail cooling in the white rat

The purpose of the study was to examine a) the effect of local cooling on the metabolic rate, b) the effect of metabolic rate on the peripheral circulation, and c) acclimation to local cooling. After habituation to the experimental situation, 10 white rats had their tails exposed to ice water for 40 min/day for 37 days. Metabolic rate and tail temperature were measured. There was a conspicuous increase in oxygen consumption during the first 10 min of each cold exposure. This increase did not change significantly through the series. The metabolic rate during cooling was significantly reduced in the last half of the series. Tail temperature was significantly influenced by metabolic rate and increased significantly from the beginning of the series to the middle, and decreased from the middle to the end. Time of onset of the cold-induced vasodilatation decreased in the middle of the series and increased again at the end. These paradoxical findings are believed to be due to interplay between orienting reactions and habituation. It is pointed out that habituation may counteract acclimation.