Dpcpx

The aCSF used for dissections and recordings contained (in mM) 127 NaCl, 26 NaHCO₃, 10 glucose, 3 KCl (unless otherwise stated), 2 CaCl, 1.25 NaH₂PO₄, and 1 MgCl₂. TFLLR, theophylline, MSO, FA and glutamine were supplied by Sigma-Aldrich (Poole, UK); DPCPX and SCH58261 were supplied by Abcam (Cambridge, UK); ARL67156 was supplied by Tocris Bioscience (Bristol, UK). All drugs were dissolved in reverse-osmosis water, except picrotoxin, DPCPX and SCH58261, which were dissolved in DMSO. The concentration of DMSO in working solutions did not exceed 0.1% (v/v).

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).