Fig. 7.

Cocaine-induced σ₁R-mediated ERK1/2 phosphorylation. CHO cells transfected with D₁ receptor cDNA (1.5 μg, filled bars) or cotransfected (open bars) with D₁R cDNA and σ₁R siRNA (125 pmol) were incubated with increasing concentrations of cocaine for 30 min (A) or with 150 μM cocaine for increasing time periods (B). (C and D) CHO cells were transfected only with D₁ receptor cDNA (1.5 μg) and were treated (30 min) with increasing concentrations of cocaine (C) or with 150 μM cocaine for different periods of time (D), in the absence (filled bars) or presence of 10 μM of the D₁R antagonist SCH 23390 (open bars) or 1 μM σ₁R antagonist PD144.418 (cross-hatched bars). ERK1/2 phosphorylation is represented as percentage over basal levels (100%). Results are mean ± SEM of four to seven independent experiments performed in duplicate. In all samples, bifactorial ANOVA showed a significant (P < 0.0001 in A–C; P < 0.001 in D) effect of cocaine, and Bonferroni post hoc tests showed a significant counteraction of cocaine effect by siRNA (A and B, *P < 0.05 and **P < 0.01 compared with sample with the same treatment and without siRNA transfection) and a significant SCH 23390-mediated or PD144.418-mediated counteraction of the cocaine effect for some concentrations and exposure times (C and D, *P < 0.05, **P < 0.01, and ***P < 0.001 compared with control samples with the same treatment).