ESTRADIOL, BUT NOT DIHYDROTESTOSTERONE, IN THE MEDIAL AMYGDALA FACILITATES MALE HAMSTER SEX BEHAVIOR

In the male Syrian hamster, the medial amygdaloid nucleus (Me) and med ial preoptic area (MPOA) are critical for expression of male mating be havior. These regions contain steroid receptor-containing neurons that transduce hormonal signals essential for copulation. In castrated mal es bearing an intracerebral steroid implant in the MPOA, testosterone or estradiol can facilitate sexual activity. However, DHT is without e ffect. Testosterone can also stimulate mating when implanted in the Me . The present study determined if estradiol or DHT had behavioral acti vity in the Me. Twenty adult male hamsters were selected for vigorous sexual behavior. Twelve weeks after castration, sexual behavior was as sessed and each male received a single intracranial implant (23-gauge tubing packed with crystalline estradiol or DHT, n = 10 each) placed s tereotaxically into posterior Me (MeP). Behavior was examined after su rgery to determine if androgens or estrogens in MeP could stimulate se xual behavior above that observed after castration. Mating behavior in DHT-implanted males was not significantly different from castrates. H owever, males with estradiol implants displayed significantly more cop ulatory and noncopulatory sexual activity after surgery compared to ma les with DHT implants. These results suggest that testosterone facilit ation of mating behavior in MeP is mediated by aromatization to estrad iol, and that DHT is not behaviorally active in this nucleus.