Altered adenosine/glutamate levels in ENT1−/− mice. (A,B) Measurement of adenosine and glutamate levels in the NAc. (A) ENT1−/− mice showed decreased basal adenosine levels in accumbal dialysates [122.2 ± 18.5 nM in ENT1+/+ mice, 65.6 ± 14.8 nM in ENT1−/− mice; t(13) = 2.34, p = 0.03]. n = 7 ~ 8 for each genotype. *p < 0.05 compared to ENT1+/+ mice by unpaired two-tailed t-test. (B) ENT1−/− mice showed increased basal glutamate levels in accumbal dialysates [37.8 ± 8.3 nM in ENT1+/+ mice, 72.04 ± 11.0 nM in ENT1−/− mice; t(6) = 2.48, p = 0.04]. n = 4 for each genotype. *p < 0.05 compared to ENT1+/+ mice by unpaired two-tailed t-test. n = 4 with duplicative analysis. (C) Measurement of extracellular glutamate concentration in the NAc using no-net flux microdialysis. ENT1−/− mice showed a 2.6-fold increase in basal extracellular glutamate levels in the NAc [0.49 ± 0.08 nM in ENT1+/+ mice, 1.27 ± 0.29 nM in ENT1−/− mice; t(12) = 2.26, p = 0.04]. *p < 0.05 compared to ENT1+/+ mice by unpaired two-tailed t-test. n = 6~8 for each genotype. (D,E) Expression of EAAT2 and EAAT1 in the NAc. (D) EAAT2 protein levels were significantly reduced in the NAc of ENT1−/− mice compared to ENT1+/+ mice [t(13) = 3.85, p = 0.002], while (E) there was no difference in EAAT1 expression, n = 7~8, *p < 0.05 compared to ENT1+/+ mice after normalization by GAPDH (unpaired, two-tailed t-test). All data are presented as the mean ± SEM.