Adenosine Receptor Antagonists in Instrumental Learning

The following drugs were used in the present study: KW-6002 ((E)-1,3-diethyl-8-(3,4-dimethoxystyryl)-7-methyl-3,7-dihydro-1H-purine-2,6-dione, a selective adenosine A_2AR antagonist) and DPCPX (8-cyclopentyl-1,3-dipropylxanthine, a selective adenosine A₁R antagonist). KW-6002 (1 mg/kg, 5 mg/kg, Sundia, United States) was suspended in dimethyl sulfoxide (DMSO, sigma), ethoxylated castor oil (Sigma) and water with a proportion of 15%:15%:70%. DPCPX (6 mg/kg, Abcam) was dissolved in 0.9% NaCl with 5% DMSO. The control mice were treated with corresponding vehicles. All the solutions were prepared immediately before administration. The administered doses of KW-6002 and DPCPX referred to previous researches (Chen et al., 2001 ; Prediger et al., 2004 (link); Nguyen et al., 2014 (link)). Drugs were injected intraperitoneally (i.p.) routinely in a volume of 0.1 ml/10 g of body weight. The specific drug administration time course depended on experimental designs: prior to (30 min before) and post (10 min after) everyday RI training for learning and consolidation periods of instrumental learning, respectively (Figure 2A), while treated 30 min before devaluation test/omission test, but not available in the RI training sessions for expression of instrumental behavior (Figure 3A).