ABSTRACT
The neuromodulatory role of adenosine in the mammalian central nervous system has been well documented. Central administration of adenosine and its analogs has been reported to suppress autonomic functions. Microinjection of adenosine analogs into the brainstem caused a profound depression in both blood pressure and heart rate in rats. As both central and peripheral injection of adenosine and its analogs produced potent hypnogenic effects, adenosine has been proposed to exert a physiological regulatory role in sleep. To measure adenosine concentration within various brain areas, tissue samples were homogenized in 1 N perchloric acid and centrifuged to remove precipitated protein. Among all changes in the pattern of adenosine receptor binding during hibernation, the increase in receptor density in the midbrain nuclei is of particular interest. In view of the inhibitory nature of adenosine, the increase in A1 receptor density in this area suggests that adenosine may also participate in suppressing the activity of suprachiasmatic nucleus during hibernation.
