(a) Representative picture of βArr2 overexpression in the NAc of a Dbh −/− mouse that received the βArr2 virus. (b) Western blot data (mean ± SEM above, representative blot below) for βArr2:actin ratio in the NAc of Dbh −/− mice that received GFP virus (n = 6) or βArr2 virus (n = 7). ***p < 0.001 compared to Dbh −/− with GFP virus. (c) Novelty-induced (drug-free state) and (d) cocaine-induced (15 mg/kg, i.p., administered after 30 min in chamber) locomotor activity in Dbh +/− mice (n = 8), Dbh −/− mice that received GFP virus (n = 10), and Dbh −/− mice that received βArr2 virus (n = 11). *p < 0.05, **p < 0.01 compared to Dbh +/− controls. AC, anterior commissure; Core, NAc core; Shell, NAc shell; arrow, needle track.