Upregulation of dopamine D1 receptor gene expression by ECS. A: single ECS caused transient increase in Drd1 and Drd5 expression in DG [Dunnett's test: **P < 0.001, ***P < 0.001 compared with CNT; 1-way ANOVA: F(3,12) = 27.77, P < 0.0001 for Drd1 and F(3,14) = 20.36, P < 0.0001 for Drd5]. Gene expression levels were assessed at different time intervals as indicated. B: a lasting increase in Drd1 expression after repeated ECS in DG [Dunnett's test: *P < 0.05, **P < 0.001; 1-way ANOVA: F(3,12) = 5.247, P = 0.0152 for Drd1, F(3,14) = 3.331, P = 0.0505 for Drd2, and F(3,14) = 7.056, P = 0.004 for Drd5]. C: single ECS increased Drd1 expression in DG, but not in CA3 (***P = 0.0007).