Clarification of the mechanisms involved in circadian body temperature rhythm and its physiological significance

本研究的目的是阐明昼夜体温节律产生的机制。本研究假设：1）视交叉上核（SCN），即视交叉上核（SCN）; e.昼夜节律的中枢调节中枢和外周水平的温度敏感性，和2）体温节律在同步中枢和外周的节律中是重要的。在实验中，小鼠在自由进食或禁食48 h后暴露于20℃的寒冷环境中，然后检测代谢产热和棕色脂肪组织中UCP 1 mRNA的表达。此外，还估计了下丘脑中神经活动所反映的cFos表达。在缺乏正常昼夜节律的Clock突变小鼠上重复相同的实验方案。在自由进食期间，在冷的温度调节反应和cFos表达没有差异。然而，在禁食期间，产热反应仅在暗相明显，并且SCN中的cFos表达在亮相增强。Clock突变小鼠的反应没有相位差异。我们还发现了一个来自SCN和室旁核的抑制网络，与交感神经活动有关。SCN受环境温度和摄食条件的影响，参与体温调节的时间依赖性。

The goal of present study was to clarify the mechanism involved in generation of circadian body temperature rhythm. In the research, we hypothesized that 1) the suprachiasmatic nucleus (SCN), i. e. the central for circadian rhythms modulates thermosensitiveity at the levels of the central and periphery, and 2) the body temperature rhythm is important in synchronizing the rhythms of the central and periphery. In experiments, mice were exposed to the cold at 20℃ after ad-lib feeding or 48-h fasting, then we estimated metabolic heat production and UCP1 mRNA in the brown adipose tissue. In addition, cFos expression reflected by neural activity in the hypothalamus was also estimated. The same experimental protocol was repeated on Clock mutant mice, which lacks normal circadian rhythmicity. During ad-lib feeding, there were no differences in thermoregulatory responses and cFos expression in the cold. However, during fasting, heat production response was apparent only in the dark phase, and cFos expression in the SCN was augmented in the light phase. There were no phase-differences in the responses in Clock mutant mice. We also found an inhibitory network from the SCN and paraventricular nucleus associated with the sympathetic nerve activity. The SCN was influenced by environmental temperature and feeding condition, which is involved in time-dependency of body temperature regulation.