3 groups: sham surgery, ovariectomized (ovx), ovariectomized + 3mg pellet of 17-beta-estradiol (Innovative Research, Sarasota, FL) | 3 groups: sham surgery, ovariectomized (ovx), ovariectomized + 3mg pellet of 17-beta-estradiol (Innovative Research, Sarasota, FL) |