Abstract
In the hibernation-regulation system, we have shed light on the activation of the A1 receptor by adenosine for the generation of hypothermia in the entrance phase of hibernation, and the activation of the μ1-opioid receptor by opioid peptides for maintenance of hypothermia in the maintenance phase. Moreover, recent studies in our laboratories have demonstrated that tyrosine-releasing hormone (TRH) is a key endogenous substance involved in the elevation of body temperature in hamsters during the arousal phase. It is well known that central prostaglandin (PG) D2 and the adenosine systems play important roles in sleep induction. In addition, we have clarified that the central opioidergic systems also contribute substantially to sleep maintenance. However, PGE2 and the histaminergic systems play critical roles in awakening from sleep. Similar histaminergic systems are thought to contribute to awakening from hibernation as well. There are many similarities in the central control mechanisms of sleep and hibernation. Although the arousal system (TRH system) acts tonically during hibernation, hibernation is in fact maintained by inhibiting the arousal system in phases via activations of the adenosine and opioidergic systems. All these systems are believed to collaboratively modulate sleep regulation. [Jpn J Physiol 55 Suppl:S20 (2005)]
