Blockade of testosterone-induced mounting behavior in the male rat with intracranial application of the aromatization inhibitor, androst-1,4,6,-triene-3,17-dione.

Propylene glycol (glycol) solutions containing either testosterone (T) or estradiol (E2) were infused directly into the preoptic area (POA) of longterm castrated rats in order to reinstate male copulatory behavior. In addition, castrated males were administered T or E2 in the POA in combination with a steroid that has been shown to block the aromatization of testosterone to estradiol, androst-1,4,6-triene-3,17-dione (ATD). The facilitatory action of testosterone on mounting behavior was blocked when it was given in combination with ATD. Animals treated in the POA with glycol +T, glycol +E2 or ATD + E2 all showed significant increases in mounting behavior over preimplant levels. There was no significant rise in the number of intromissions or ejaculations in any of the hypothesis that, at least for mounting behavior, aromatization is necessary for the stimulation of male sexual behavior by testosterone.