Regional and subcellular [3h]estradiol localization in selected brain regions and pituitary of female mice: effects of unlabeled estradiol and various anti-hormones

Effect of cyproterone acetate on steroid-induced sexual behavior in adult ewes

The inhibitory effect of cyproterone acetate on sexual behavior has been investigated in adult ovariectomized ewes treated with either testosterone propionate (10 mg/day) or estradiol benzoate (200 micrograms/day) to induce male activity and female receptivity simultaneously. Intra-muscular injections of 100 mg cyproterone acetate/day resulted in a rapid decrease in some of the male sexual responses after both testosterone and estradiol treatments, whereas the female reactions were eliminated by cyproterone acetate only when they had been induced by testosterone.

Interaction of the anti-estrogen CI-628 and estradiol on plasma LH and hypothalamic LH-RH in the female rat

The effects of the anti-estrogen Ci-628 have been tested on both plasma LH and hypothalamic LH-RH content in ovariectomized or ovariectomized, estradiol (E2)-implanted rats, in order to correlate those parameters with the [3H]E2 retention in the hypothalamus and the pituitary. Incresing doses of CI-628 induced a dose-dependent inhibition of [3H]E2 retention in both cytosolic and nuclear fractions of the pituitary. In contrast, hypothalamic retention of [3H]E2 is only inhibited significantly with higher doses of CI-628 (2.4 and 24 mg/kg). In ovariectomized rats, only a high dose of CI-628 (24 mg/kg) is able to decrease elevated LH levels observed following castration. In the presence of E2, CI-628 has both estrogenic and anti-estrogenic properties on LH secretion. CI-628 acts at the pituitary level to decrease the tissue sensitivity to LH-RH, but has no effect on mediobasal hypothalamic (MBH) LH-RH content.

Anti-estrogen inhibition of testosterone-stimulated aggression in mice

Testosterone-stimulated intermale aggression in castrated mice can be reversibly inhibited by anti-estrogen administration suggesting that estrogen formation and actions in the brain may be required for testosterone's behavioral actions.

Differential depletion of cytoplasmic high affinity oestrogen receptors after the in vivo administration of the antioestrogens, clomiphene, MER-25 and tamoxifen

1 The in vivo actions of the oestrogen antagonists, MER-25 and tamoxifen upon the cytosol oestrogen receptors prepared from amygdala, hypothalamus, pituitary and uterus of rats were studied 24 h after drug administration. 2 There was a dose-related depletion of cytosol oestrogen receptors. However, the uterine and pituitary receptors were consistently affected at a lower dose than were those from the brain. 3 The ratios of the combined central ED50 to the combined peripheral ED50 were clomiphene 169 greater than MER-25 19.2 greater than tamoxifen 2.13. 4 The receptor changes were not related to biological activity monitored by serum luteinizing hormone levels and uterotrophic response. 5 The possible role of these drug effects in the induction of ovulation and future developments are discussed.

Binding of [3H]estradiol by brain cell nuclei and female rat sexual behavior: inhibition by experimental diabetes

In streptozotocin-diabetic female rats acute (24 h) withdrawal of insulin significantly impairs both estradiol + progesterone-induced sexual receptivity and cell nuclear concentration of [3H]estradiol in hypothalamus, preoptic area, and pituitary gland. Omission of insulin treatment for the first 24 h of a 30-h or 54-h estradiol benzoate-conditioning period significantly reduced mean lordosis ratings of ovariectomized-diabetic rats. Insulin withdrawal at the time of progesterone treatment and behavioral testing did not diminish sexual receptivity. One-half or 2 h after an intravenous injection of [3H]estradiol-17beta diabetic rats without insulin exhibited reduced cell nuclear [3H]estradiol concentrations (2 h) and/or diminished cell nuclear/whole homogenate concentration ratios (0.5 and 2 h). Twenty-four hour insulin withdrawal affected neither whole tissue [3H]estradiol uptake nor hypothalamus-preoptic area cytoplasmic estrogen-receptor content. These results: (1) suggest that diminished estradiol binding by target tissue cell nuclei may contribute to the well-known reproductive failures of female diabetics, and (2) support the concept that estradiol acts at the level of brain cell nuclei to induce female sexual behavior.

Estrogen-induced sexual receptivity and localization of 3H-estradiol in brains of female mice: effects of 5 alpha-reduced androgens, progestins and cyproterone acetate

Sexual receptivity induced in ovariectomized CD-1 mice with chronic daily administration of estradiol benzoate (E2 B) was blocked by concurrent administration of the 5 alpha-reduced androgen, dihydrotestosterone (DHT). Receptivity was restored in these females with progesterone-, but not with dihydroprogesterone-priming 6 hr prior to testing. Delaying the DHT injections until 12 hr after the E2 B injections greatly reduced its inhibitory properties. Receptivity in E2 B-primed females was also blocked by concurrent treatment with cyproterone acetate and 3 alpha-, but not 3 beta-adrostanediol. Pretreatment with DHT, or 3 alpha- or 3 beta-androstanediol failed to consistently affects 3H-estradiol accumulation in crude nuclear and supernatant fractions from brain and pituitary.

Binding of [3-H]estradiol by brain cell nuclei and female rat sexual behavior: inhibition by antiestrogens

The antiestrogens MER-25, CI-628, and nafoxidine inhibit the uptake of [3H]-estradiol in whole homogenates and isolated cell nuclei tissues and the pituitary, and inhibit estradiol-induced female sexual behavior. The antiestrogens were injected intraperitoneally 2 h prior to an intravenous injection of [3H]estradiol, and the animals were killed 2 h after the estradiol. CI-628 reduces radioactivity in whole homogenates and isolated cell nuclei of cerebral cortex, hypothalamus, preoptic area -septum and pituitary. Nafoxidine reduces uptake in cell nuclei of the hypothalamus, preoptic area-septum and pituitary. In this paradigm, MER-25 inhibited uptake only in the pituitary. In the analogous behavioral experiments, with antiestrogens injected 2 h prior to an intravenous injection of unesterified estradiol, CI-628 and nafoxidine totally inhibited lordosis responding. MER-25 shows no inhibition of behavior in this paradigm. However, when MER-25 is injected 12 h prior to the estradiol, it inhibits retention of [3H]estradiol at 2 h in brain and pituitary cell nuclei, and lordosis responding is also inhibited. Additionally, the antiestrogens can apparently displace previously bound [3H]estrdiol. When the antiestrogens are injected 2 h prior to an injection of [3H]estradiol, MER-25, CI-628 and nafoxidine all show greater inhibition of nuclear estradiol retention at 12 h after the [3H]estradiol injection than 2 h. Analogously, when CI-628 is injected 2 h after an intravenous injection of [3H]estradiol, it displaces most of the radioactivity present in hypothalamic-preoptic area nuclei at 12 h after the estradiol injection. These results indicate that antiestrogens can prevent or reverse the nuclear concentration of estradiol in brain cells and are consistent with a role of the cell nucleus in the induction of estrous behavior by estradiol.

Intracerebral implantation of the anti-estrogen CN-69, 725-27: Effects on female sexual behavior in rats

Ovariectomized adult female rats were stereotaxically implanted with double walled cannulas (22 ga outer and 27 ga inner) and tested for sexual receptivity (lordosis behavior) following SC estradiol benzoate and progesterone priming. Implantation of the anti-estrogen CN-69,725-27 (c. 65 mug) immediately after the first of 3 daily estrogen injections produced a dramatic inhibition of sexual receptivity when these implants were placed in the preoptic and anterior hypothalamic areas. CN-69,725-27 implants had no effect on receptivity when implanted in the middle hypothalamus, mesencephalon or frontal cortex. All inhibitory effects of the anti-estrogen were reversible within one day after removal of the CN-69,725-27 cannula from the brain.