Testosterone-Estradiol Filled Polydimethylsiloxane Subdermal Implants: Effect on Fertility and Masculine Sexual and Aggressive Behavior of Male Rats

Simultaneous administration of specific doses of testosterone and estradiol via subdermal Silastic implants created a reversible azoospermia in male rats without increasing the seminal vesicle and ventral prostate weights or serum concentrations of testosterone and estradiol (Ewing et al., 1977). Herein we report that a single implantation of 2.5 cm testosterone and 0.1 cm estradiol subdermal polydimethylsiloxane (PDS, Silastic) capsules rendered male rats reversibly sterile for 8 months. The onset or cessation of sterility occurred abruptly 6 weeks following either the implantation or removal of steroid filled capsules, respectively. This reversible sterility was attained without any significant change in either masculine sex behavior or shock induced aggressive behavior.