Combined stimuli of cold, hypoxia, and dehydration status on body temperature in rats: a pilot study with practical...

As human thermoregulatory responses to maintain core body temperature (T_core) under multiple stressors such as cold, hypoxia, and dehydration (e.g., exposure to high-altitude) are varied, the combined effects of cold, hypoxia, and dehydration status on T_core in rats were investigated. The following environmental conditions were constructed: (1) thermoneutral (24 °C) or cold (10 °C), (2) normoxia (21% O₂) or hypoxia (12% O₂), and (3) euhydration or dehydration (48 h water deprivation), resulted in eight environmental conditions [2 ambient temperatures (T_a) × 2 oxygen levels × 2 hydration statuses)]. Each condition lasted for 24 h.

Normoxic conditions irrespective of hypoxia or dehydration did not strongly decrease the area under the curve (AUC) in T_core during the 24 period, whereas, hypoxic conditions caused greater decreases in the AUC in T_core, which was accentuated with cold and dehydration (T_a × O₂ × hydration, P = 0.040 by three-way ANOVA). In contrast, multiple stressors (T_a × O₂ × hydration or T_a × O₂ or O₂ × hydration or T_a × hydration) did not affect locomotor activity counts (all P > 0.05), but a significant simple main effect for O₂ and T_a was observed (P < 0.001). Heat loss index was not affected by all environmental conditions (all P > 0.05). In conclusion, decreases in T_core were most affected by multiple environmental stressors such as cold, hypoxia, and dehydration.