Effects of fasting on thermoregulatory processes and the daily oscillations in rats

Kei Nagashima, Sadamu Nakai, Kenta Matsue, Masahiro Konishi, Mutsumi Tanaka, Kazuyuki Kanosue

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To investigate the mechanism involved in the reduction of body core temperature (Tcore) during fasting in rats, which is selective in the light phase, we measured Tcore, surface temperature, and oxygen consumption rate in fed control animals and in fasted animals on day 3 of fasting and day 4 of recovery at an ambient temperature (Ta) of 23°C by biotelemetry, infrared thermography, and indirect calorimetry, respectively. On the fasting day, 1) Tcore in the light phase decreased (P < 0.05) from the control; however, Tcore in the dark phase was unchanged, 2) tail temperature fell from the control (P < 0.05, from 30.7 ± 0.1 to 23.9 ± 0.1°C in the dark phase and from 29.4 ± 0.1 to 25.2 ± 0.2°C in the light phase), 3) oxygen consumption rate decreased from the control (P < 0.05, from 24.37 ± 1.06 to 16.24 ± 0.69 ml·min-1·kg body wt-0.75 in the dark phase and from 18.91 ± 0.64 to 14.00 ± 0.41 ml·min-1·kg body wt-0.75 in the light phase). All these values returned to the control levels on the recovery day. The results suggest that, in the fasting condition, Tcore in the dark phase was maintained by suppression of the heat loss mechanism, despite the reduction of metabolic heat production. In contrast, the response was weakened in the light phase, decreasing Tcore greatly. Moreover, the change in the regulation of tail blood flow was a likely mechanism to suppress heat loss.

Original languageEnglish
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number6 53-6
Publication statusPublished - 2003 Jun 1
Externally publishedYes



  • Core temperature
  • Heat loss mechanism
  • Oxygen consumption

ASJC Scopus subject areas

  • Physiology

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