Adenosine Transporter ENT1 Regulates the Acquisition of Goal-Directed Behavior and Ethanol Drinking through A2A Receptor in the Dorsomedial Striatum

Adenosine signaling has been implicated in the pathophysiology of many psychiatric disorders including alcoholism. Striatal adenosine A(2A) receptors (A(2A)R) play an essential role in both ethanol drinking and the shift from goal-directed action to habitual behavior. However, direct evidence for a role of striatal A(2A)R signaling in ethanol drinking and habit development has not been established. In the present study, we found that decreased A(2A)R-mediated CREB activity in the dorsomedial striatum (DMS) enhanced initial behavioral acquisition of goal-directed behaviors and the vulnerability to progress to excessive ethanol drinking during operant conditioning in mice lacking ethanol-sensitive adenosine transporter ENT1 (ENT1(-/-)). Using mice expressing beta-galactosidase (lacZ) under the control of seven repeated CRE sites in both genotypes (CRE-lacZ/ENT1(+/+) mice and CRE-lacZ/ENT1(-/-) mice) and the dominant-negative form of CREB, we found that reduced CREB activity in the DMS was causally associated with decreased A(2A)R signaling and increased goal-directed ethanol drinking. Finally, we have demonstrated that the A(2A)R antagonist ZM241385 dampened protein kinase A activity-mediated signaling in the DMS and promoted excessive ethanol drinking in ENT1(+/+) mice, but not in ENT1(-/-) mice. Our results indicate that A(2A)R-mediated CREB signaling in the DMS is a key determinant in enhancing the development of goal-directed ethanol drinking in mice.