Mounting and aggressive behavior in PAC1^-/- males. A, Female mounting behavior by PAC1^+/+ (n = 12), PAC1^+/- (n = 10), and PAC1^-/- (n = 19) male mice. Data depict mean ± SEM number of mounts of the same ovariectomized female during four successive 1 min trials separated by 10 min. The fifth trial (new) depicts the response to a novel female during a 1 min pairing 10 min after the fourth trial (post hoc analysis, ^*p < 0.02; ^**p < 0.01 vs PAC1^+/+). B, Female mounting behavior of PAC1^+/+ (n = 12), PAC1^+/- (n = 10), and PAC1^-/- (n = 19) male mice. Data depict mean ± SEM number of mounts of an ovariectomized female during two successive 4 min trials separated by 30 min. During the first trial, PAC1^-/- mice exhibited increased mounting behavior compared with WT (post hoc analysis, ^*p < 0.02 vs PAC1^+/+). C, D, Male mounting and aggressive behavior of PAC1^+/- (n = 6) and PAC1^-/- (n = 6) male mice. Data depict mean ± SEM number of mounts (C) or attacks (D) toward a gonadectomized CD-1 male mouse (GDX; tested on day 1) or a GDX male swabbed with 20 μl of fresh urine (U) collected from a dominant CD-1 male (GDX+U1, tested on day 8; GDX+U2, tested on day 29; t test, ^*p < 0.05; ^**p < 0.01 vs PAC1^+/-).