The adenosine A2A receptor (ADORA2A) is a major target of caffeine (Daly and Fredholm 1998) and forms a heterodimer with the dopamine D2 receptor (Fuxe et al. 2005). We investigated the effect of ADORA2A polymorphisms on the anxiety response to amphetamine in healthy human subjects (Hohoff et al. 2005) and found that two polymorphisms (rs5751876; T/T and rs3032740; Tins/Tins), were associated with increased anxiety at the 10 and 20 mg doses.
