Neuronal UCP1 expression suggests a mechanism for local thermogenesis during hibernation

Mammalian hibernators can reduce their metabolic rate by 95% and body temperature to 2 °C. However, their central and peripheral nervous systems retain activity even in cold, through unknown mechanisms. We report here that neurons from hibernating squirrels express uncoupling protein 1 (UCP1), a protein known as a heat generator in brown adipose tissue. We show that squirrel UCP1 acts as the typical thermogenic protein and is up-regulated during torpor, suggesting its thermogenic capability is important during hibernation. Accordingly, we found that the temperature of squirrel brain during the deep torpor associated with hibernation is warmer than the surrounding tissues. We hypothesize that neuronal UCP1 allows squirrels to withstand the long hibernation season and tolerate temperatures prohibitively low for survival and neuronal function in nonhibernating species.