Fig. 5

D2 dopamine receptor tolerance is mediated by PRDX6-dependent ROS production. a HEK293 cells transiently expressing HA-D2DR(L) were pretreated with vehicle or MJ33 (10 µM) 30 min prior to being treated for 1 h with vehicle or quinpirole (100 nM). Cells were imaged for ROS using CellROX Green; scale bar represents 12.5 µm. b Quantification of ROS in a. Quinpirole increased CellROX Green fluorescence; this was blocked by pretreatment with MJ33 (two-way ANOVA, significant effect of quinpirole (P < 0.01) and significant interaction (P < 0.05), n = 4–5; *P < 0.05, **P < 0.01, Holm–Sidak post hoc analysis of MJ33 vs. vehicle pretreatment). c, d Mice were injected with saline or MJ33 (1.25 mg kg⁻¹ i.p.) 1 h prior to the initial injection of quinpirole (0.2 mg kg⁻¹ i.p.) or saline. Two hr later, mice were injected with a quinpirole (0.2 mg kg⁻¹ i.p.) or saline (baseline) placed in a novel cage, and locomotor activity was measured over 20 min. c Locomotion was measured as distance traveled (cm), in 5 min bins. Pretreatment significantly affected locomotion. (two-way ANOVA, significant effect of treatment (P < 0.001), time (P < 0.001), and significant interaction (P < 0.01), n = 7–9). d Total locomotion over 20 min following quinpirole administration was quantified as a percent locomotion observed in saline treated mice. Quinpirole significantly reduced locomotor activity in all pretreatment groups, but mice pretreated with quinpirole moved significantly more than mice pretreated with saline or MJ33 + quinpirole (one-way ANOVA, P < 0.01; *P < 0.05, **P < 0.01, ***P < 0.01, Holm–Sidak post hoc analysis). Error bars represent mean ± SEM