Urine recognition in PAC1^+/- and PAC1^-/- male mice. A, Time spent by PAC1^+/- (n = 8) and PAC1^-/- (n = 8) male mice investigating the inside of a tube containing 25 μl of urine collected from three ovariectomized CD-1 female mice during three successive 1 min trials separated by 10 min. During the fourth trial, the response of males to urine collected from three different ovariectomized females was recorded 10 min after the third trial. The lack of significant response to the control tube containing water and placed on the other side of the cage indicates that the decline in time investigating the urine-containing tubes is specific (post hoc test, ^*p < 0.05; ^**p < 0.01; ^***p < 0.001 vs first presentation). B, Time spent investigating urine-containing tubes on the second and third exposure compared with the time spent during the first presentation (unpaired t test, ^*p < 0.05 vs PAC1^+/-).