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  • Title: Effects of ovariectomy on dexamethasone suppression of the adrenal axis in adult rats.
    Author: Ramaley JA.
    Journal: Neuroendocrinology; 1976; 20(3):260-9. PubMed ID: 958597.
    Abstract:
    Three weeks after ovariectomy, adult female rats had lower basal levels of serum corticosterone (B), which did not display a daily rhythm, and reduced responses to ether stress, measured by blood levels of B 15 min after ether exposure. Ovariectomized (OVX) females were more sensitive to dexamethasone (DEX) suppression of the ether induced stress response, reaching basal levels at a dose of 50 mug DEX/100 g b.w. At this dose, B levels were reduced by only 30% over saline-control values in intact rats. DEX-treated intact rats displayed a short-term suppression, reaching a maximum 2 h after the injection followed by a rebound 7 h post-injection and a second suppression period evident by 11 h post-injection. OVX rats showed a steadily increasing suppression that began 1 h after injection and persisted to the last sample time at 11 h post-injection. The disappearance of DEX from peripheral blood was followed by means of radioimmunoassay and no difference was found between intact and OVX rats either in the basal state or 15 min after ether stress. It can be concluded that ovarian steroids condition the sensitivity of the adrenal axis to DEX suppression and that the differences in DEX sensitivity we have previously noted between prepubertal and adult rats can be accounted for by a change in gonadal status rather than by a critical developmental event in the adrenal axis itself. Effects of ovariectomy on dexamethasone (DEX) suppression of the adrenal axis were studied in adult rats. 3 weeks postovariectomy, adult female rats had lower basal levels of serum corticosterone (B), which did not display a daily rhythm, and reduced responses to ether stress measured by blood levels of B 15 minutes after ether exposure. Ovariectomized (OVX) females were more sensitive to dEX suppression of the ether-induced stress response, reaching basal levels at a dose of 50 mcg DEX/100 gm body weight. At this dose B levels were reduced by 30% over intact control values. DEX-treated intact rats displayed a short-term suppression, reaching a maximum 2 hours after the injection followed by a rebound 7 hours postinjection and a 2nd suppression by 11 hours postinjection. OVX rats revealed a steadily increasing suppression that began 1 hour postinjection and persisted to the last sample time at 11 hours postinjection. The disappearance of DEX from peripheral blood was similar in both intact and OVX rats in the basal state and 15 minutes after stress. Itis concluded that ovarian steroids condition the sensitivity of the adrenal axis to dEX suppression and that the difference in DEX sensitivity previously noted between prepubertal and adult rats can be accounted for by a change in gonadal status rather than by a critical development in the adrenal axis itself.
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