The Impact of Estrogen Supplementation to Autonomic and Sleep Modulations in Free-Moving Spontaneously Hypertensive Rats

Abstract

Sleep and estrogen levels have an impact on neural regulation and are associated with cardiovascular (CV) events. We investigated the effects of estrogen on heart rate variability (HRV) and circadian cycle in spontaneously hypertensive rats (SHRs). Polysomnographic recording was performed in seven male and seven female SHRs during sleep. The electroencephalogram (EEG) and electromyogram (EMG) were evaluated to define active waking (AW), quiet sleep (QS), and paradoxical sleep (PS) stages. Cardiac activities were measured by RR interval of the electrocardiogram (ECG), mean arterial pressure (MAP), and power spectrum of HRV. In ECG, estrogen prolonged the RR interval in total sleep when compared with that at baseline in male SHRs (203.74 ± 6.61 versus 181.30 ± 8.06 ms, P < 0.001) and in female SHRs (169.21 ± 6.43 versus 160.76 ± 10.66 ms, P < 0.05). In HRV, the estrogen increased the high frequency (HF) in total sleep when compared with that at baseline in male SHRs (1.03 ± 0.28 versus 0.60 ± 0.43 ln (ms 2), P < 0.001) and in female SHRs (0.71 ± 0.26 versus 0.42 ± 0.19 ln (ms 2), P < 0.05). In male SHRs, estrogen increased the frequency of QS (26.50 ± 4.85 versus 20.79 ± 5.07, P < 0.01) and PS (25.64 ± 5.18 versus 20.14 ± 4.75, P < 0.05) stages when compared with baseline. In female SHRs, estrogen increased the percentage of delta waves in total sleep (79.87% ± 3.10% versus 76.71% ± 2.74%, P < 0.05) when compared with that at baseline. In HRV, estrogen leads to neuromodulation by increased parasympathetic tone in all SHRs, suggesting a lower risk to CV events. In sleep analyses, estrogen in male SHRs caused poor sleep quality. In contrast, estrogen in female SHRs demonstrated improved quality of sleep and decreased risk of hypertension.

Accumulated unhealthy behaviours and insomnia in Japanese dwellers with and without cardiovascular risk factors: a cross-sectional study

“… 48 Oestrogen in spontaneously hypertensive rats demonstrated improved quality of sleep in female. 49 Women with hypertension are older than those without it in our study. One possibility is that our study was participated by premenopausal and postmenopausal women, suggesting a stronger effect on insomnia due to reduced or fluctuating oestrogen levels before and after menopause.…”

“…With regard to sex steroids, there is uncertainty about the effect of testosterone levels, particularly in men, on sleep disturbances; however, an association between decreased or fluctuating oestrogen levels and sleep disturbances is thought to exist in women 48. Oestrogen in spontaneously hypertensive rats demonstrated improved quality of sleep in female 49. Women with hypertension are older than those without it in our study.…”

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