Female Reproductive Hormones Alter Sleep Architecture in Ovariectomized Rats

Samüel Deurveilher,Kazue Semba,Benjamin Rusak

doi:10.1093/sleep/34.4.519

Abstract

Treating ovariectomized rats with physiological levels of estradiol and/or progesterone affects aspects of both baseline (24 h) sleep and recovery (18 h) sleep after 6 h of sleep deprivation. We have extended the analysis of these effects by examining several additional parameters of sleep architecture using the same data set as in our previous study (Deurveilher et al. SLEEP 2009;32(7):865-877). Sleep in ovariectomized rats implanted with oil, 17 β-estradiol and/or progesterone capsules was recorded using EEG and EMG before, during, and after 6 h of sleep deprivation during the light phase of a 12/12 h light/dark cycle. During the baseline dark, but not light, phase, treatments with estradiol alone or combined with progesterone decreased the mean duration of non-rapid eye movement sleep (NREMS) episodes and the number of REMS episodes, while also increasing brief awakenings, consistent with the previously reported lower baseline NREMS and REMS amounts. Following sleep deprivation, the hormonal treatments caused a larger percentage increase from baseline in the mean durations of NREMS and REMS episodes, and a larger percentage decrease in brief awakenings, consistent with the previously reported larger increase in recovery REMS amount. There were no hormonal effects on NREMS and REMS EEG power values, other than on recovery NREMS delta power, as previously reported. Physiological levels of estradiol and/or progesterone in female rats modulate sleep architecture differently at baseline and after acute sleep loss, fragmenting baseline sleep while consolidating recovery sleep. These hormones also play a role in the diurnal pattern of NREMS maintenance.

Highlights

Baseline Sleep In our previous study, we reported that the amount of non-rapid eye movement sleep (NREMS) during the 24 h baseline period was significantly lower in the high estradiol LE (HE) and LEP groups compared to the Oil group, and this decrease tended to be more prominent during the 12 h dark phase.[17]
The mean duration of NREMS episodes during the dark phase was shorter in the HE, LEP, and M groups by 31 to 38% compared to the Oil and low progesterone (LP) groups (Group: F5,42 = 5.36, P < 0.001; P < 0.05, HE, LEP, and M < Oil, and LEP and M < LP)
The mean duration of NREMS episodes was significantly shorter in the dark than in the light phase in the LE, HE, LEP, and M groups (P < 0.05 vs. light phase), whereas it was similar between the light and

Summary

Introduction

To determine how female sex hormones modulate spontaneous (baseline) sleep and sleep recovery after sleep loss, we previously used a rodent model of hormonal loss and replacement in a paradigm involving gentle handling to generate acute (6 h) sleep deprivation.[17] We used subcutaneous steroid implants to produce stable, physiological levels of estradiol and progesterone in adult ovariectomized (OVX) rats in order to evaluate effects on baseline and recovery sleep in similar stable hormonal conditions. This approach is not possible in normally cycling females because of the changing estradiol and proges-

Methods

Results

Conclusion