Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
J Comp Physiol B. 2012 May;182(4):451-67. doi: 10.1007/s00360-011-0630-y. Epub 2011 Nov 12.
One of the most profound hallmarks of mammalian hibernation is the dramatic reduction in food intake during the winter months. Several species of hibernator completely cease food intake (aphagia) for nearly 7 months regardless of ambient temperature and in many cases, whether or not food is available to them. Food intake regulation has been studied in mammals that hibernate for over 50 years and still little is known about the physiological mechanisms that control this important behavior in hibernators. It is well known from lesion experiments in non-hibernators that the hypothalamus is the main brain region controlling food intake and therefore body mass. In hibernators, the regulation of food intake and body mass is presumably governed by a circannual rhythm since there is a clear seasonal rhythm to food intake: animals increase food intake in the summer and early autumn, food intake declines in autumn and actually ceases in winter in many species, and resumes again in spring as food becomes available in the environment. Changes in circulating hormones (e.g., leptin, insulin, and ghrelin), nutrients (glucose, and free fatty acids), and cellular enzymes such as AMP-activated protein kinase (AMPK) have been shown to determine the activity of neurons involved in the food intake pathway. Thus, it appears likely that the food intake pathway is controlled by a variety of inputs, but is also acted upon by upstream regulators that are presumably rhythmic in nature. Current research examining the molecular mechanisms and integration of environmental signals (e.g., temperature and light) with these molecular mechanisms will hopefully shed light on how animals can turn off food intake and survive without eating for months on end.
哺乳动物冬眠的最显著特征之一是在冬季几个月内食物摄入量的急剧减少。几种冬眠动物完全停止进食（绝食），近 7 个月无论环境温度如何，在许多情况下，无论它们是否有食物可吃。人们已经研究了冬眠时间超过 50 年的哺乳动物的食物摄入调节，但对于控制冬眠动物这种重要行为的生理机制仍然知之甚少。非冬眠动物的损伤实验表明，下丘脑是控制食物摄入和体重的主要大脑区域。在冬眠动物中，食物摄入和体重的调节可能受年节律控制，因为食物摄入有明显的季节性节律：动物在夏季和初秋增加食物摄入，秋季食物摄入下降，在许多物种中实际上在冬季停止，随着环境中食物的可用性再次在春季恢复。循环激素（例如瘦素、胰岛素和胃饥饿素）、营养物质（葡萄糖和游离脂肪酸）以及细胞酶（如 AMP 激活的蛋白激酶 (AMPK)）的变化已被证明决定了参与食物摄入途径的神经元的活性。因此，食物摄入途径似乎很可能受到各种输入的控制，但也受到上游调节剂的影响，这些调节剂可能具有节律性。目前研究检查环境信号（例如温度和光照）与这些分子机制的分子机制的整合，有望阐明动物如何能够关闭食物摄入并在不进食的情况下生存数月。
