ACTIVATION OF FEMININE SEXUAL-BEHAVIOR IN CASTRATED MALE-RATS BY INTRAHYPOTHALAMIC IMPLANTS OF ESTRADIOL BENZOATE

The effects of intracerebral estradiol benzoate (EB) implants upon lordosis behavior in castrated male rats were investigated. 27 gauge EB-filled or Blank implants were placed unilaterally in either the preoptic area (POA) or the region of the ventromedial hypothalamic nucleus (VMH). When 0.5 μg of EB was administered subcutaneously for eight days, males with EB implants had significantly higher lordosis quotients (LQ) than males with Blank implants. EB implants located in the region of the VMH were significantly more effective in stimulating lordosis responses than implants in the POA. These results indicate that, in male rats as in females, the VMH region is a primary site for the hormonal activation of lordosis behavior.