This caught our attention, because Adora2a is required for GDNF-stimulated dopamine release in vitro [100]; reduced striatal Adora2a expression has been identified in a subgroup of schizophrenia patients [83]; and some schizophrenia patients voluntarily self-administer excessive amounts of coffee that contains caffeine, a non-selective antagonist for adenosine receptors, as the active ingredient [101, 102]. The gene discussed is GDNF; the disease is schizophrenia.