Scientists at the National Institutes of Health (NIH) have discovered a cellular mechanism in hibernating ground squirrels that may protect the nervous system from being damaged during extreme cold and lowered body temperatures, called hypothermia. This discovery could lead to a better understanding of the cellular mechanisms of hibernation and the cellular effects of hypothermia in non-hibernating animals. The communication appears in the September 21, 2000, issue of Nature (1).
Hibernation is a survival strategy that some mammals use during the winter to cope with shortages of food supplies and cold temperatures. When a mammal prepares for hibernation, its body temperature lowers to near-freezing temperature. For brief periods, the hibernating mammal will wake up and re-warm to normal body temperature before descending again into a state of lowered body temperature and hibernation. Somehow all the organs of the hibernating animal, including the central nervous system, survive these rapid temperature shifts without damage. Previous studies of cold adaptation during hibernation focused on cellular changes seen during the step-wise progression into hibernation, brought on by seasonal changes. This is one of the first studies to observe the cellular effects that accompany the rapid changes in body temperature occurring during deep hibernation.
"This study shows a physical membrane change through which cells may acclimate to extreme cold and still function," says John M. Hallenbeck, M.D., one of the authors and Chief of the Stroke Branch of the National Institute of Neurological Disorders and Stroke (NINDS).
The NIH scientists used light microscopy and freeze-fracture electron microscopy to examine the tissues of ground squirrels sampled during hibernation while in a hypothermic state and during arousal at room temperature. They discovered "slits" on microscopy images of the hibernating squirrels neurons and glia, the primary cells of the centra
Contact: Marcia Vital
NIH/National Institute of Neurological Disorders and Stroke