Ovary Removal Simulation Menopause Behavioral Study Of Sleep Disorders

OBJECTIVE To clarify the sleep-wake profiles of ovariectomized (OVX) mice and the effects of β-estradiol treatment. METHODS Under5%chloral hydrate anesthesia [360mg·kg-1intraperitoneal (i.p.)], C57BL/6mice underwent the surgery for implantation of electrodes for electroencephalogram (EEG) and electromyogram (EMG) recordings and replacement of hibateral ovaries. The software SleepSign was used to analyze EEG parameters, in terms of sleep amount, sleep episode, stage transition and power density. RESULTS OVX increased NREM sleep amount with reduced wake amount at night. The mean duration of wake state reduced but its episode number increased. The episode numbers of short wakefulness (<16s) increased while a wide range episode number of NREM sleep increased. After P-estradiol treatment, wake state increased and NREM sleep decreased in the dark period. Different from the basic changes in the OVX mice, P-estradiol affected not only the sleep-wake pattern during night period but in the light period. After P-estradiol treatment, the mean duration of wake, the transition of NREM sleep to wake, wake to NREM sleep and NREM sleep to REM sleep all increased during the dark period. In the light period, the mean duration of wake and the transition of each states have been increased. CONCLUSION The wake state becomes fragmented in the dark period after OVX. The treatment of P-estradiol could improve the changes of sleep-wake profiles caused by OVX.