Abstract
The thermoregulatory heat production is actively suppressed during the entrance into hibernation, thereafter the body temperature is maintained, for several days or weeks, at a level slightly higher than environment temperature. After this torpid state, onset of arousal is triggered by still-unknown mechanisms, and after several hours of complex, integrated organ specific processes body temperature returns to the cenothermic level. Invivo synthesis of protein and mRNA appears inhibited during hibernation and the early stages of arousal indicating that the genomic requirements for initiation of hibernation and arousal from hibernation all occur in the cenothermic period before the animal enters hibernation. The torpor-arousal cycle repeats for the duration of the hibernation season. Although the hibernation control mechanism is not well understood, hypothermia and the onset of the entrance into hibernation may be triggered by some opioid like substances. The hypothermic action of these substances does not function in active summer animals, suggesting that seasonal and also hibernation specific physiological adaptations are required before hibernation can be initiated and arousal from hibernation can be successfully performed. All of necessaries for arousal from hibernation must have been prepared beforehand, because during deep hibernation protein synthesis seems to be globally suppressed. To confirm this point, we injected hibernating hamsters with radioactively labeled precursors of protein and RNA synthesis, and those substances newly synthesized in the major organs were quantified along the time course of hibernation. [Jpn J Physiol 54 Suppl:S56 (2004)]
