Analysis of changes in body temperature rhythm during fasting

众所周知，体温(T_B)遵循昼夜节律。尽管最近在体温调节方面的知识取得了进展，但我们对T_b节律的机制知之甚少。在这次研讨会中，我们提出了几个证据，证明：(1)昼夜节律的主要机制是体温调节过程的特征随昼夜节律的变化；(2)时钟基因和视交叉上核参与了这一机制。在随意喂养的大鼠中，T_b节律与产热节律有关。反映主动热损失的尾部表面温度也随T_b节律呈线性变化。由此认为，供热条件下的T_b节律主要是由产热决定的。禁食3天后，虽然产热量下降，昼夜节律幅度降低，但T_b节律保持良好。此外，尾部温度在活跃期有较大幅度的降低。这些结果表明，动物通过调节取决于摄食和/或营养状态的体温调节反应来控制它们的昼夜节律T_b。

It is well known that body temperature (T_b) follows a circadian rhythm. Despite recent advance in knowledge of thermoregulation, we know only a little about the mechanism of the T_b rhythm. In this symposium, we show several evidences proving that i) the prime mechanism for the circadian T_b rhythm is a change in characteristics of thermoregulatory processes according to circadian phases, ii) clock genes and the suprachiasmatic nucleus are involved in the mechanism.T_b rhythm during fasting. In ad-lib feeding rats, T_b rhythm was linked with heat production rhythm. Moreover, tail surface temperature reflecting active heat loss also changed linearly with the T_b rhythm. Thus it is thought that heat production dominantly determines the T_b rhythm in fed condition. Although heat production decreased and its circadian amplitude was blunted during 3-day fasting, the T_b rhythm was well maintained. Moreover, the tail temperature decreased greatly in the active phase. These results suggest that animals control their circadian T_b rhythm by modulating thermoregulatory responses, which depends on feeding and/or nutritional states.