0043 The Role of Median Preoptic Nucleus Astrocytes in Mediating E2’s Effects on Sleep-Wake Behavior

Abstract Introduction Although 50-70 million Americans suffer from sleep disorders, women are 2x as likely as men to experience sleep disruptions. This discrepancy emerges at puberty and is strongly associated with fluctuations in estrogen, suggesting a role for estrogens in sleep disorders. Our previous work has identified the median preoptic nucleus (MnPO) as a key site regulating estradiol (E2) effects on sleep-wake behavior. We have also shown that E2 increases extracellular adenosine in the MnPO. Astrocytes are a major source of adenosine in the central nervous system, and cortical astrocytes have been shown to regulate sleep homeostasis. Thus, we hypothesize that MnPO astrocytes play a key role in the estrogenic mechanisms regulating sleep-wake behaviors. Methods To clarify the role of astrocytes in E2- modulation of sleep, we expressed Gi- or Gq-DREADDs in MnPO astrocytes of ovariectomized rats. Rats were treated with subcutaneous Oil injections (baseline) followed by injections of low (5ug) and high (10ug) dose E2, 24 hours apart. Rats also received Vehicle or Clozapine-N-oxide (CNO; 1.7mg/kg) at the time of their Oil/E2 injections. EEG/EMG recordings were acquired throughout treatment. To inhibit Ca2+signaling, and, ultimately, gliotransmission in astrocytes, we used a viral approach to express Pleckstrin Homology domain of Phospholipase C (PLC)-like protein p130 (p130PH) in MnPO astrocytes. p130PH is an IP3 buffer that prevents IP3 from initiating intracellular Ca2+ release and was previously shown to reduce astrocytic Ca2+signaling and gliotransmission (PMID: 20736051). Experimental (p130PH) and Control (tdTomato) animals were then treated with the Oil/E2 paradigm described above. Results In Oil-treated animals, CNO activation of Gq-DREADD increased wake and decreased sleep, mimicking E2’s effects on Sleep-Wake behavior. Unexpectedly, CNO activation of Gi-DREADD produced similar effects, increasing wake and decreasing sleep. These observations may support literature findings that Gi-DREADDs, while inhibitory in neurons, may enhance activity in astrocytes. Thus, Gi-DREADDs may not be an ideal candidate for inhibiting astrocytic activity. Animals expressing p130PH (n=3) exhibited less wake and more NREM sleep than animals injected with Control virus (n=3). Conclusion These preliminary findings suggest that E2 may increase wake by enhancing activity of MnPO astrocytes and highlight a need for further investigation. Support (if any)