Endocrine Abstracts

Sleep is disturbed in both healthy and pathological aging, so it is essential to consider the role of ovarian hormones in both processes. Studies supporting the natural function of E2 (or elevated FSH) in fragmented sleep are inconsistent because when non-human animals have been used, they have mainly been male. Given this background, this study focused on determining the role of different estradiol and progesterone doses in the intermittent arousals of castrated rats maintained by two-month in controlled-conditions. These arousals were also determined in castrated rats without treatment and in sham-operated rats as experimental controls. The treatment scheme consisted of weekly increasing the dose of E2 and/or P4 to these females. The quality of sleep of the controls and the experimental evaluated by counting the animals’ number of awakenings during the sleep cycle. This procedure was performed daily for five consecutive weeks, using video cameras. The results showed a significant difference between the number of awakenings of the ovariectomized rats and the sham-operated rats during the study weeks. The number of awakenings in the castrated rats treated with E2 and/or P4 gradually decreased as the hormonal doses were increased. In such a way, in the fifth week, the awakenings fell below those in sham-operated. E2 -treatment showed an effect from the first week with the first dose, and in the fifth week, it displayed a frankly anesthetic activity. Progesterone began to show activity on the third week, but it showed an anesthetic effect with the highest dose in the fifth week. However, both steroids combined showed significant activity, reducing the number of awakenings from the third week, without achieving the anesthetic effect seen with the steroids separately at the fifth week. These results suggested estrogens and progesterone-combination regulated the number of awakenings of the castrated rats since the third-week treatment. Plots of dose-response of these experiments indicated that estradiol and progesterone effects were performing by different action mechanisms.