Although A2AR are far more abundant in striatal medium spiny neurons than elsewhere in the brain [29], A2AR are also located in DAergic [37,38,39] and glutamatergic synapses in the striatum [40,41], prompting the hypothesis that these synaptic A2AR may play a relevant role in the control of the early synaptotoxicity observed in the PD prodrome. This evidence concerns the gene ADORA2A and Parkinson disease.