If the findings in chipmunks are confirmed, the hormone would represent the first essential brain signal governing the seasonal adaptation, according to the researchers.
As hibernation factors endow animals with an incredible ability to cope under otherwise lethal conditions--ratcheting down their metabolic rate to survive on limited energy reserves and withstanding extreme cardiovascular and oxygen stresses--the candidate hormone might also pave the way toward clinical therapies that lend humans the same kind of protection, they added.
The researchers earlier found that concentrations of "hibernation-specific protein" complex (HPc) decline in the blood of hibernating chipmunks. The team now reports evidence that the level of HPc in the brain increases at the onset of hibernation independently of changes in body temperature. Moreover, treatments that block HP activity in the animals' brains cuts hibernation short.
"One of the most curious biological phenomena in mammals is their ability to hibernate circannually, which allows them to survive unusually low body temperatures at or near freezing," said study author Noriaki Kondo of Mitsubishi Kagaku Institute of Life Sciences in Japan.
"Although the functions of HP remain to be clarified, the current observations lead us to propose the involvement of the protein complex in the regulation of energy metabolism and/or biological defenses during hibernation--crucial events for adapting to the severe physiological state," Kondo said.
In the current study, the researchers first demonstrated that hibernation in chipmunks is strictly controlled by an individ
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