Dopamine’s effects in the brain are mediated by postsynaptic D1 and D2 receptors. Adenosine A1 and A2A receptors are uniquely positioned to counteract the excessive stimulation of dopamine receptors ...

Figure 2: Saccharin and quinine preference are unaffected by the absence of functional D 2 dopamine receptors ... Nestler, E. J. Molecular mechanisms of drug reinforcement and addiction.