PT - JOURNAL ARTICLE AU - David Elmenhorst AU - Philipp T. Meyer AU - Oliver H. Winz AU - Andreas Matusch AU - Johannes Ermert AU - Heinz H. Coenen AU - Radhika Basheer AU - Helmut L. Haas AU - Karl Zilles AU - Andreas Bauer TI - Sleep Deprivation Increases A<sub>1</sub> Adenosine Receptor Binding in the Human Brain: A Positron Emission Tomography Study AID - 10.1523/JNEUROSCI.5066-06.2007 DP - 2007 Feb 28 TA - The Journal of Neuroscience PG - 2410--2415 VI - 27 IP - 9 4099 - http://www.jneurosci.org/content/27/9/2410.short 4100 - http://www.jneurosci.org/content/27/9/2410.full SO - J. Neurosci.2007 Feb 28; 27 AB - It is currently hypothesized that adenosine is involved in the induction of sleep after prolonged wakefulness. This effect is partially reversed by the application of caffeine, which is a nonselective blocker of adenosine receptors. Here, we report that the most abundant and highly concentrated A1 subtype of cerebral adenosine receptors is upregulated after 24 h of sleep deprivation. We used the highly selective A1 adenosine receptor (A1AR) radioligand [18F]CPFPX ([18F]8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine) and quantitative positron emission tomography to assess cerebral A1ARs before and after sleep deprivation in 12 healthy volunteers and a control group (n = 10) with regular sleep. In sleep deprived subjects, we found an increase of the apparent equilibrium total distribution volume in a region-specific pattern in all examined brain regions with a maximum increase in the orbitofrontal cortex (15.3%; p = 0.014). There were no changes in the control group with regular sleep. This is the first molecular imaging study that provides in vivo evidence for an A1AR upregulation in cortical and subcortical brain regions after prolonged wakefulness, indicating that A1AR expression is contributing to the homeostatic sleep regulation.