ABSTRACT

Overwinter survival of the golden-mantled ground squirrel (Spermophilus lateralis) depends upon the reduced metabolic state of deep torpor and a programmed utilization of fat reserves. Hibernation consists of a series of individual torpor bouts of 2 to 14 days duration, punctuated by periodic arousals which, generally, endure for <24 h. Energy during the hibernation season is derived primarily from the mobilization of triglycerides from adipose tissues stores. Thus, the several metabolic fuels available as energy sources during hibernation include: free-fatty acids which can be utilized directly by most tissues; glucose, derived from hepatic conversion of glycerol to glucose; and ketone bodies, derived from hepatic oxidation of fatty acids. The chapter provides a preliminary evaluation of the importance of several metabolic fuels for the expression of deep torpor and arousal. Several pharmacologic treatments were used to determine the relative contribution of glucose versus fatty acids during different metabolic states of hibernation.