A–D, Startle responses (A, B) and prepulse inhibition (PPI) (C, D) in mice with altered α2C-AR expression after different doses ofd-amphetamine (d-Amph). Error bars represent mean ± SEM (n = 10–14) results from mice with targeted disruption of α2C-ARs (α2C-KO) (hatched bars), overexpression of the α2C-AR (α2C-OE) (closed bars), and corresponding wild-type mice (α2C-KO-wt or α2C-OE-wt) (open bars).