MONG, J. A. | bioRxiv Science

bioRxiv2025

The Median Preoptic Nucleus is a Key Site for Estradiol Regulation of Sleep-Wake Behaviors in Females Rats

Study ObjectivesWomen experience more sleep disruptions than men, particularly during hormonal transitions such as puberty, pregnancy, and menopause. This study investigated the role of estradiol (E2) in regulating sleep-wake behavior in female rats and identified the brain regions involved. MethodsUsing an exogenous E2 replacement model in ovariectomized rats, we assessed changes in sleep-wake patterns via EEG/EMG telemetry. The effects of E2 and progesterone, selective estrogen receptor agonists, and direct brain infusions of E2 and receptor antagonists were evaluated. ResultsE2 administration increased wakefulness, reduced non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, and decreased NREM slow-wave activity (SWA), predominantly during the dark phase. These effects required both estrogen receptor alpha (ER) and beta (ER{beta}) activation and were mediated by estrogen receptor signaling within the median preoptic nucleus (MnPO). Direct infusion of E2 into the MnPO was sufficient to replicate systemic effects, while local infusion of the pure estrogen receptor antagonist ICI 182,780 (Fulvestrant) attenuated them. Progesterone did not augment E2s actions, and males showed no sleep-wake changes in response to E2, highlighting sex-specific mechanisms. ConclusionsThe MnPO is a critical site where E2 regulates sleep-wake behavior. These findings provide a neurobiological framework for understanding how ovarian hormones contribute to sleep disruptions in women, offering potential therapeutic targets for sleep disorders related to hormonal changes. Statement of significanceSleep disturbances disproportionately affect women, particularly during hormonal transitions such as puberty, pregnancy, and menopause. Despite this, the underlying mechanisms by which estradiol (E2) influences sleep-wake behavior have remained unclear. This study identifies the median preoptic nucleus (MnPO) as a critical site where E2 signaling regulates sleep-wake patterns in female rats. Our findings demonstrate that E2 increases wakefulness and reduces both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, with effects primarily observed during the dark phase. By showing that local E2 signaling in the MnPO is both necessary and sufficient for these changes, this work offers a novel neurobiological framework for understanding how fluctuations in ovarian hormones contribute to sleep disruptions in women. These insights lay the groundwork for developing targeted therapies to improve sleep health in women, particularly those experiencing hormonal changes.

neuroscience↗

bioRxiv2025

Median Preoptic Astrocytes: Role in Sleep Regulation and Potential Mediators of Sex Differences

One in three Americans suffer from chronic sleep disorders, and women are 40% more likely than men to experience sleep disorders. This disparity emerges at puberty and is strongly associated with fluctuations in the ovarian hormone, estrogen (E2), suggesting that E2 and biological sex are a risk factor for sleep disorders. Previous work in the lab has demonstrated that E2 suppresses sleep in female rats, including in sleep deprived rats whose homeostatic need for sleep is increased. However, the specific mechanism for E2 induced decrease in sleep remains unknown. Work in the lab suggests a role for adenosine in mediating E2s sleep suppressive effects; E2 significantly increases Median Preoptic Nucleus (MnPO) extracellular adenosine and attenuates the action of specific agonists on the sleep promoting A2A-Receptor. Astrocytes represent a major source of adenosine in the CNS and have been shown to influence neuronal activity and downstream behaviors. In this project, we tested the hypothesis that astrocytes mediate E2s sleep suppressive effects. We used Gq-linked designer receptors exclusively activated by designer drugs (DREADDs) to evaluate the Gq pathway, which represents a core signaling mechanism in astrocyte activity. We found that, in female rats, activation of Gq signaling in astrocytes decreased sleep and inhibited homeostatic need for sleep. We further expressed the Pleckstrin Homology domain of PLC-like protein (p130PH), which has been shown to attenuate astrocyte activity and functions, in median preoptic nucleus (MnPO) astrocytes. We found that p130PH expression in MnPO astrocytes raised homeostatic sleep pressure to the same extent as 6 hours of sleep deprivation. We further report that inhibiting astrocytic function did not prevent E2s sleep suppressing effects suggesting that astrocytes may not play a role in estrogenic modulation of sleep. However, we did discover that MnPO astrocyte effects on sleep are sex-dependent. p130PH expression in MnPO astrocytes increased sleep and homeostatic sleep drive in female rats but showed a trend towards decreasing sleep and homeostatic sleep need in males. Further, while astrocyte effects on homeostatic sleep need are relegated to the dark phase in female rats, astrocytes appear to influence homeostatic sleep need in both the dark and light phase. To our knowledge, this is the first demonstration of a sex-based difference in astrocyte effects on sleep and homeostatic sleep pressure.

neuroscience↗