Cardio-respiratory recordings of hibernating animals

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The ability of mammals to hibernate is a dramatic example of phenotypic plasticity. Each year mammalian hibernators undergo a complex suite of morphological, physiological, and behavioral changes in preparation for environmental changes that lead to increased energy demands at a time of reduced energy supply. Hibernators avoid this conflict by entering extended bouts of torpor that range in duration from a few days to several weeks depending on the species. During torpor, basal metabolic rate can fall to as low as 1– 4% of euthermic (non-hibernating) levels and body temperature to within a few degrees above ambient temperature. The ability to enter torpor and to hibernate, is found throughout the class Mammalia and appears to involve differential expression of genes common to all mammals, rather than the induction of novel gene products unique to hibernating species. During hibernation, while most biochemical and physiological processes are dramatically slowed if not halted altogether, some critical functions continue to be precisely regulated. Breathing is one of these. Ventilation must still be regulated to match O2 consumption and CO2 excretion to metabolism, and blood levels of O2, CO2 and pH continue to be homeostatically maintained. We have been studying the cardio-respiratory adaptations of a variety of species of hibernating mammals and have made good progress in beginning to describe the mechanistic basis of their tolerance to cold and hypoxia (low levels of O2). These results give insight not only into the hibernating phenotype but into the basis of hypothermic respiratory arrest in non-hibernating species, including humans. One of our biggest challenges has been obtaining data during the processes of entrance into, and arousal from hibernation. Animals are very sensitive to disturbance at this time making traditional forms of data gathering impossible. There are several companies now commercially making radiotelemetry units at reasonable prices that would allow us to gather data from implanted transmitters removing the need for handling animals and for hard-wired electrodes and cannulae that restrict animal movement. Purchase of this equipment would allow us to gather information during these transition phases that previously has been unavailable.