ADORA2A and Parkinson disease: A2A adenosine receptors are present in key ‘non-motor’ areas of the brain (e.g., nucleus accumbens, olfactory tubercle, amygdala, hippocampus, hypothalamus, thalamus, and cerebellum [17]) and play a role in the pathophysiology of sleep disturbances and mood disorders such as depression and anxiety which are common non-motor features of pre-motor and both early and late-stage clinical PD [28,118].