Medroxyprogesterone acetate and tamoxifen do not decrease aggressive behavior in CF-1 male mice.

Intact CF-1 male mice were given daily injections of either medroxyprogesterone acetate (MPA, an antiandrogen), tamoxifen (TAM, an antiestrogen), or the two drugs in combination and tested for aggressive behavior toward bulbectomized stimulus males. None of the treatments decreased fighting behavior over a 20-day test period and the presence of TAM led to increased aggression even in the presence of MPA. Testis weight was reduced by MPA while both compounds decreased seminal vesicle weight. The mechanisms involved in the observed effects are considered as well as the implications of the results for the clinical use of these compounds as modulators of testosterone-facilitated behaviors.