C-FOS MESSENGER-RNA INCREASES IS THE GROUND-SQUIRREL SUPRACHIASMATIC NUCLEUS DURING AROUSAL FROM HIBERNATION

During hibernation the body temperature of the golden-mantled ground s quirrel, Spermophilus lateralis, may drop below 5 degrees C for a few hours to a week or more. Animals cycle between euthermia and deep hibe rnation many times over the course of the hibernation season. Expressi on of the transcription factor c-fos increased in the suprachiasmatic nucleus (SCN) of the hypothalamus, the mammalian circadian clock, duri ng deep hibernation and peaked during the arousal from hibernation. Th e pattern of increase in c-fos messenger RNA seen in the SCN by in sit u hybridization was similar to that seen by Northern blot analysis of total hypothalamic RNA. The induction of c-Sos may reflect a wake-up s ignal, increasing transcription of genes required in the euthermic sta te.