Figure 2.

Trp2−/− males mate normally with females but display increased mounting toward other males. (A) Equivalent sexual behavior toward estrous females is exhibited by sexually naive trp2 (n = 11, blue bars) and control (n = 12, red bars) male mice in a 30-min mating test. (B) Increased intermale mounting is observed in trp2−/− mice (n = 23) in comparison to controls (n = 25) upon the addition of a male to their home cage in a 15-min test. Both before and after mating experience with females, trp2 males exhibited a significantly greater number of intermale mounts than controls (mount frequency, P < 0.001; Mann–Whitney U test). In fact, trp2−/− mice displayed a significant increase in intermale mounting after sexual experience with females (mount frequency, P < 0.05, Wilcoxon signed rank test). (C) trp2−/− males continue to mount males at a high rate even when a female is present. Sexually experienced trp2−/− (n = 12) and control (n = 12) male mice were observed for behaviors exhibited upon the simultaneous addition of a male and nonestrous female mouse into their home cage in a 15-min test. Trp2 males exhibit a 2-fold preference for mounting females, whereas in the control group there is a 10-fold preference for mounting females.