Under conditions of scarce food availability and cool ambient temperature, the mouse ( Mus Musculus ) enters into torpor, a state of transient metabolic suppression mediated in part by the autonomic nervous system. Hypothalamic orexins are involved in the coordination of behaviors and autonomic function. We tested whether orexins are necessary for the coordinated changes in physiological variables, which underlie torpor and represent its physiological signature. We performed simultaneous measurements of brain temperature, electroencephalographic, and electromyographic activity allowing objective assessment of wake–sleep behavior, and cardiovascular, respiratory, and metabolic variables in orexin knockout mice (ORX-KO) and wild-type mice (WT) during torpor bouts elicited by caloric restriction and mild cold stress. We found that torpor bouts in WT are characterized by an exquisitely coordinated physiological signature. The characteristics of torpor bouts in terms of duration and rate of change of brain temperature and electromyographic activity at torpor entrance and exit did not differ significantly between ORX-KO and WT, and neither did the cardiovascular, respiratory, and metabolic characteristics of torpor. ORX-KO and WT also had similar wake–sleep state changes associated with torpor bouts, with the exception of a significantly higher rapid-eye movement sleep time in ORX-KO at torpor entrance. Our results demonstrate that orexins are not necessary either for the normal physiological adaptations occurring during torpor in mice or for their coordination, suggesting that mechanisms different from orexin peptide signaling may be involved in the regulation and the coordination of these physiological responses.

中文翻译：

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每日麻木的生理特征不依赖于食欲素

在食物稀缺和环境温度较低的情况下，小鼠（Mus Musculus）进入麻木状态，这是一种部分由自主神经系统介导的瞬时代谢抑制状态。下丘脑食欲素参与行为和自主神经功能的协调。我们测试了食欲素对于生理变量的协调变化是否必要，这些变量是麻木的基础并代表其生理特征。我们同时测量了大脑温度、脑电图和肌电图活动，从而客观评估了食欲素敲除小鼠 (ORX-KO) 和野生型小鼠 (WT) 在麻木发作期间的觉醒-睡眠行为以及心血管、呼吸和代谢变量由热量限制和轻度冷应激引起。我们发现 WT 中的麻木发作的特点是精心协调的生理特征。在 ORX-KO 和 WT 之间，在大脑温度和肌电图活动的持续时间和变化率方面，麻木发作的特征在麻木入口和出口之间没有显着差异，并且麻木的心血管、呼吸和代谢特征也没有显着差异。ORX-KO 和 WT 也有与麻木发作相关的类似唤醒-睡眠状态变化，除了 ORX-KO 在麻木入口处的快速眼动睡眠时间显着增加。我们的结果表明，食欲素对于小鼠麻木期间发生的正常生理适应或它们的协调都不是必需的，