ADORA2A and Parkinson disease: Because adenosine/A2AR signaling functionally opposes the actions of D2Rs on D2-cells by its ability to increase the A2AR/Gαolf-dependent cAMP production, it has so far been suggested that A2AR antagonism may boost the anti-parkinsonian action of D2R agonists in treating PD symptoms (Jenner, 2003; Schwarzschild et al., 2006; Fuxe et al., 2007; Huot et al., 2013).