Combined stimuli of cold, hypoxia, and dehydration status on body temperature in rats: a pilot study with practical impl
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(2020) 13:530 Uno et al. BMC Res Notes https://doi.org/10.1186/s13104-020-05375-w
Open Access
RESEARCH NOTE
Combined stimuli of cold, hypoxia, and dehydration status on body temperature in rats: a pilot study with practical implications for humans Tadashi Uno†, Tatsuya Hasegawa and Masahiro Horiuchi*†
Abstract Objective: As human thermoregulatory responses to maintain core body temperature ( Tcore) 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 Tcore 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 ( Ta) × 2 oxygen levels × 2 hydration statuses)]. Each condition lasted for 24 h. Results: Normoxic conditions irrespective of hypoxia or dehydration did not strongly decrease the area under the curve (AUC) in Tcore during the 24 period, whereas, hypoxic conditions caused greater decreases in the AUC in Tcore, which was accentuated with cold and dehydration ( Ta × O2 × hydration, P = 0.040 by three-way ANOVA). In contrast, multiple stressors ( Ta × O2 × hydration or Ta × O2 or O2 × hydration or Ta × hydration) did not affect locomotor activity counts (all P > 0.05), but a significant simple main effect for O2 and Ta was observed (P 0.05). In conclusion, decreases in Tcore were most affected by multiple environmental stressors such as cold, hypoxia, and dehydration. Keywords: Area under the curve, Heat loss index, High-altitude, Hypothermia, Metabolism, Set point Introduction Most of mammal’s (including human) energy regulates core body temperature (Tcore). Various environmental factors such as heat, cold, hypoxia, humidity, or wind would affect Tcore. Although physiological adaptation to environmental stressors is often studied in isolation, these stressors are frequently combined outside of laboratory settings. At high altitudes, both barometric
*Correspondence: [email protected] † Tadashi Uno and Masahiro Horiuchi equally contributed to this study Division of Human Environmental Science, Mount Fuji Research Institute, Kami‑yoshida 5597‑1, Fuji‑yoshida‑city, Yamanashi 4030005, Japan
pressure and ambient temperature ( Ta) decreases with an increase in altitude. Cold exposure reduces human cutaneous blood flow that decreases heat transfer from the core to peripheral tissues [1]. This decreases in skin temperature, which narrows the gradient for cutaneous heat loss, and promotes heat conservation, and is vital to the prevention of hypothermia in cold. Contrariwise, hypoxic conditions reduce metabolism and core body temperature (Tcore) in many small mammals [2], primates [3], and humans [4–7]. In humans, this may be explained by peripheral circulation. Simulated high altitude elicits a cutaneous hyperemia
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