Comparative physiological and biochemical aspects of hypothermia as a model for hibernation.

It is obvious that research is far from the last chapter in developing a model for natural hibernation. The relationships and comparative mechanisms for thermogenesis and survival in hibernation and experimental hypothermia are still unclear. Yet, two primary areas appear to be most promising, namely, the control of thermogenesis via the glucocorticoids and the specific role of the central nervous system (CNS) in survival of hypothermic subjects and arousal of hibernating subjects. Although there have been several approaches to understanding the role of the CNS in terms of circulation, integrity of the blood-brain barrier (BBB) system, and CNS sites of activity, it may appear that more questions have been raised than have been answered. However, a more optimistic view can also be taken. The development of a laboratory model, using experimental hypothermia for natural hibernation, is progressing. This view is justified in terms of results from the use of glucocorticoids in metabolic regulation of available carbohydrates, i.e., available glucose in hypothermia, and the continued promising parallel studies of physiological and biochemical integrity of areas of the CNS in hypothermic and hibernating subjects.