The middle-aged ovariectomized marmoset (Callithrix jacchus) as a model of menopausal symptoms: Preliminary evidence

Menopausal women often suffer from hot flashes and sleep disturbances that significantly impact their quality of life. Both human and animal studies suggest that loss of estrogens during menopause contribute to these symptoms. In the female rat, both core body temperature (CBT) and sleep are sensitive to 17β-estradiol (E2) levels, but important differences between the rat and the human patterns limit the interpretation of the results. The sleep and thermoregulation of the common marmoset (Callithrix jacchus) more closely resemble human patterns. However, no study to date has examined whether E2 influences sleep and thermoregulation in this species. The main goal of the present study was to investigate the suitability of the ovariectomized (OVX) marmoset for studying two major menopausal symptoms experienced by women, sleep disturbance and thermodysregulation. Two middle-aged OVX marmosets (6years old) were implanted with a telemeter that records electroencephalograms (EEG), electromyograms (EMG), and CBT. Sleep patterns and CBT were recorded under baseline, two E2 replacement (6 and 12μg/kg/day, p.o.) conditions and two E2 withdrawal conditions. Relative to both baseline and withdrawal, high E2 replacement was associated with lower nighttime CBT. In addition, fewer nighttime arousals were observed under low E2 replacement compared to baseline. Higher delta power was observed under both E2 replacement conditions suggesting enhanced sleep quality. These preliminary results suggest that E2 modulates sleep and thermoregulation in the OVX marmoset, making it a promising model for studying menopausal symptoms.