Flutamide Inhibits Testosterone-Induced Masculine Sexual Behavior in Male and Female Rats*

Publisher Website
Google Scholar
Abstract
The ability of the nonsteroidal antiandrogen flutamide to block testosterone-induced masculine copulatory behavior was assessed in male and female rats. In Exp 1, ovariectomized adult female rats given 100 μg testosterone (T) and 5 mg flutamide [4′-nitro-3′-trifluoromethylisobutyrylanilide (SCH)] daily for 5 weeks showed significantly less mounting behavior and lower copulatory rates than females receiving 100 Hg T and the control vehicle propylene glycol. However, when treatments were later reversed in these females, SCH was unable to block existing mounting behavior, suggesting that while SCH can block T-induced initiation of mounting behavior it may not affect T-mediated maintenance of mounting. In Exp 2, the ability to SCH to block T-induced initiation of masculine sexual behavior in long term castrated male rats, who had not mounted on at least three consecutive tests was examined. Daily SCH (5 mg) treatment along with 100 μg T (providing an antihormone to hormone ratio of 50:1) significantly reduced intromission but not mounting behavior in males compared to that in control animals receiving T plus propylene glycol. When the antihormone to hormone ratio was increased to 100:1 (10 mg SCH to 100 μg T), mounting behavior as well as the display of intromission patterns were significantly reduced. Ejaculatory behavior was not seen in males treated with either dose of the antiandrogen. Additionally, seminal vesicle and ventral prostate weights were significantly reduced by SCH in T-treated males compared to those in controls. The number of cornified papillae as well as penis diameter were also significantly diminished by SCH treatment in animals receiving T. These data suggest that mounting and intromission behavior patterns as well as genital morphology are T dependent and can be blocked by the nonsteroidal antiandrogen SCH. (Endocrinology106: 1917, 1980).