A. Schematic illustration of delay discounting task. On free choice trials, two lever options are presented, each leading to a small or a large reward. The delay to the large reward is progressively increased across sessions (0 – 10 s), while the small reward is given with no delay. B. In the absence of delays to either reward, EGFP and D2R-overexpressing mice similarly increased preference for the large reward option after 14 training sessions (shown here as blocks of 2 sessions). C. With increasing delays to the large reward, both groups showed discounting, an effect that was significantly greater following CIN D2R upregulation. *p < 0.0001 denotes significant virus × delay interaction, n = 8 mice/group. D. In the same mice, latency to make a choice following lever extension in free choice trials was not altered by D2R upregulation. E, F. No significant changes were observed in distance traveled in a 90-min open field session (EGFP n = 9; D2 n = 11).