Estradiol in the male rat amygdala facilitates mounting but not ejaculation

Mating activates estrogen sensitive neurons in several regions of male rat brain, including the medial amygdala (MEA). Infusion of the aromatase inhibitor, Fadrozole, into the MEA reduced mating, presumably by inhibiting conversion of testosterone (T) to estradiol (E(2)). We investigated whether administering E(2) locally into the amygdala (AMG) would maintain sexual behavior in male rats given systemic Fadrozole to eliminate E(2) elsewhere in the brain. Gonadally intact male rats were divided into two matched groups, based on ejaculatory performance in weekly tests with receptive females. All males received 0.29 mg/kg/day sc Fadrozole and bilateral implants to AMG. E(2)-in-AMG males (N=6 experimentals) received implants tipped with a cured mixture of E(2) in Silastic Medical Adhesive, whereas Vehicle-in-AMG males (N=6 controls) received implants tipped with cured adhesive alone (without E(2)). In E(2)-in-AMG males, postoperative mount and intromission frequency did not differ significantly from pretreatment baseline levels, but ejaculation frequency declined significantly (P<.01). Conversely, in Vehicle-in-AMG males, postoperative mounts and intromissions (P<.01) and ejaculations (P<.01) declined significantly. Postoperative mount and intromission frequency of Vehicle-in-AMG males was significantly lower than that of E(2)-in-AMG males (P<.01), but ejaculation frequency did not differ significantly between groups. This suggests that E(2)-sensitive AMG neurons are important for sexual arousal but not ejaculatory performance.