Effects of estrogen via estrogen receptors on parvalbumin levels in cardiac myocytes of ovariectomized rats

Estrogen deficiency affects synchronized neural connectivity in the olfactory bulb-nucleus accumbens circuit: A local field potential study in ovariectomized mouse model

Estrogen plays a crucial role in regulating various brain functions, including cognitive, emotional, and social behaviors. Menopausal women face a decline in estrogen levels, which has been linked to several physical and mental health issues. However, the impact of estrogen on the olfactory bulb-nucleus accumbens (OB-NAc) circuit, which is essential for regulating emotions and cognitive behaviors, remains poorly understood. To test the hypothesis that estrogen deficiency affects signal processing, we recorded local field potentials (LFPs) using intracranial electrodes implanted in four-week-old ovariectomized (OVX) mice during an open-field test (OFT). The results showed a decrease in locomotor activity and increase in anxiety-like behaviors in OVX mice. Furthermore, we found a decrease in high-gamma power in the OB. We analyzed coherence and inter-region phase-amplitude coupling (ir-PAC) to explore the connectivity between the OB and NAc. We observed a decrease in low-gamma and high-gamma coherence in OVX mice. Additionally, we found that the direction of connectivity from the NAc to the OB was disrupted in OVX mice. In summary, our study provides evidence that estrogen deficiency is linked to synchronized neural connectivity changes in the OB-NAc circuit. These findings have implications for our understanding of the roles played by the OB-NAc neural circuit and estrogen in the regulation of general exploratory behavior and anxiety-like behavior.

The effects of the estrous cycle, menopause, and recording condition on female rat ultrasonic vocalizations

The goal of this study was to evaluate the effects of ovarian hormones on female rat ultrasonic vocalizations (USVs). Twenty (10 control and 10 ovariectomized) 3-month-old female rats were recorded in 3 recording conditions (elicitation, dyad, and isolation) over a full estrous cycle or time-matched duration. There were differences in USV acoustics (frequency and complexity parameters) across recording conditions but no differences in USV acoustics between control and ovariectomized groups. USVs produced in isolation had lower frequency and complexity parameters than elicited USVs for both control and ovariectomized rats. Additionally, for control rats, USV parameters of frequency, complexity, duration, and intensity changed depending on the estrous state. Therefore, although fluctuating hormone levels may influence USV acoustics, this variation can be controlled for by ovariectomizing female rats.

The Effects of Menopause on Neuromuscular Parameters of the Rat Vocal Folds

OBJECTIVES/HYPOTHESIS

Menopause adversely affecs power and endurance of the limb muscles. However, despite clinical observations that menopause corresponds to negative changes of the voice, the direct effects of estrogen deprivation on the thyroarytenoid muscles are unknown. The purpose of this study was to investigate the effects of estrogen deprivation via ovariectomy on three neuromuscular parameters of the thyroarytenoid muscles using a rat model.

STUDY DESIGN

Animal model.

METHODS

Cryosections of vocal folds of 20 (10 control and 10 ovariectomized) female rats were stained to label neuromuscular junctions, fiber size, or parvalbumin levels using immunohistochemical techniques and compared between experimental groups.

RESULTS

The neuromuscular junctions, thyroarytenoid fiber sizes, and parvalbumin levels of the vocal folds were similar between experimental groups.

CONCLUSIONS

The loss of estrogen did not change neuromuscular parameters of the vocal folds of adult female rats; therefore, vocal changes within the outer vibratory layers of the vocal folds may primarily be responsible for clinically observed menopausal vocal changes.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1343-1348, 2021.

Sex and age differentially affect GABAergic neurons in the mouse prefrontal cortex and hippocampus following chronic intermittent hypoxia

Obstructive sleep apnea (OSA), a chronic sleep disorder characterized by repetitive reduction or cessation of airflow during sleep, is widely prevalent and is associated with adverse neurocognitive sequelae including increased risk of Alzheimer's disease (AD). In humans, OSA is more common in elderly males. OSA is characterized by sleep fragmentation and chronic intermittent hypoxia (CIH), and recent epidemiological studies point to CIH as the best predictor of neurocognitive sequelae associated with OSA. The sex- and age- specific effects of OSA-associated CIH on specific cell populations such as γ-aminobutyric acid (GABA)-ergic neurons in the hippocampus and the medial prefrontal cortex (mPFC), regions important for cognitive function, remain largely unknown. The present study examined the effect of 35 days of either moderate (10% oxygen) or severe (5% oxygen) CIH on GABAergic neurons in the mPFC and hippocampus of young and aged male and female mice as well as post-accelerated ovarian failure (AOF) female mice. In the mPFC and hippocampus, the number of GABA-labeled neurons increased in aged and young severe CIH males compared to controls but not in young moderate CIH males. This change was not representative of the individual GABAergic cell subpopulations, as the number of parvalbumin-labeled neurons decreased while the number of somatostatin-labeled neurons increased in the hippocampus of severe CIH young males only. In all female groups, the number of GABA-labeled cells was not different between CIH and controls. However, in the mPFC, CIH increased the number of parvalbumin-labeled neurons in young females and the number of somatostatin-labeled cells in AOF females but decreased the number of somatostatin-labeled cells in aged females. In the hippocampus, CIH decreased the number of somatostatin-labeled neurons in young females. CIH decreased the density of vesicular GABA transporter in the mPFC of AOF females only. These findings suggest sex-specific changes in GABAergic neurons in the hippocampus and mPFC with males showing an increase of this cell population as compared to their female counterparts following CIH. Age at exposure and severity of CIH also differentially affect the GABAergic cell population in mice.

Increased incidence of bowel and psychological symptoms in Chinese female D-IBS patients with premenstrual syndrome

The purpose of this study was to investigate levels of stress, gynecological events, bowel, and psychological symptoms in Chinese women of reproductive age who experienced both diarrhea-predominant irritable bowel syndrome (D-IBS) and premenstrual syndrome. A cross-sectional study used the self-reported questionnaire based on previous studies done abroad with the Rome III criteria and Symptom Checklist-90 Scale. The research was performed on 233 reproductive age women in China. A descriptive, comparative approach was used to (a) describe general characteristics and the history of disease both of the overlapping group and the D-IBS group, (b) compare stress and gynecological experience of the 2 groups, (c) compare the characteristics of defecation and bowel habits by group, and (d) compare psychological symptoms between groups. Percentage distribution and chi-square tests were used to analyze data. The results revealed that compared to simple D-IBS patients, the patients in the overlapping syndromes group had increased stress and gynecological events and more severe bowel and psychological symptoms. Overlapping syndromes were associated with repeated episodes of longer duration and delayed recovery. Future studies with expanded sample size and blood collection may verify and explain the results of this study.

Estrogen administration modulates hippocampal GABAergic subpopulations in the hippocampus of trimethyltin-treated rats

Given the well-documented involvement of estrogens in the modulation of hippocampal functions in both physiological and pathological conditions, the present study investigates the effects of 17-beta estradiol (E2) administration in the rat model of hippocampal neurodegeneration induced by trimethyltin (TMT) administration (8 mg/kg), characterized by loss of pyramidal neurons in CA1, CA3/hilus hippocampal subfields, associated with astroglial and microglial activation, seizures and cognitive impairment. After TMT/saline treatment, ovariectomized animals received two doses of E2 (0.2 mg/kg intra-peritoneal) or vehicle, and were sacrificed 48 h or 7 days after TMT-treatment. Our results indicate that in TMT-treated animals E2 administration induces the early (48 h) upregulation of genes involved in neuroprotection and synaptogenesis, namely Bcl2, trkB, cadherin 2 and cyclin-dependent-kinase-5. Increased expression levels of glutamic acid decarboxylase (gad) 67, neuropeptide Y (Npy), parvalbumin, Pgc-1α and Sirtuin 1 genes, the latter involved in parvalbumin (PV) synthesis, were also evident. Unbiased stereology performed on rats sacrificed 7 days after TMT treatment showed that although E2 does not significantly influence the extent of TMT-induced neuronal death, significantly enhances the TMT-induced modulation of GABAergic interneuron population size in selected hippocampal subfields. In particular, E2 administration causes, in TMT-treated rats, a significant increase in the number of GAD67-expressing interneurons in CA1 stratum oriens, CA3 pyramidal layer, hilus and dentate gyrus, accompanied by a parallel increase in NPY-expressing cells, essentially in the same regions, and of PV-positive cells in CA1 pyramidal layer. The present results add information concerning the role of in vivo E2 administration on mechanisms involved in cellular plasticity in the adult brain.

Estrogen replacement improves skeletal muscle performance by increasing parvalbumin levels in ovariectomized rats

Muscle weakness is common during menopause. Effective estrogen replacement was hypothesized to prevent sarcopenia. This study aimed to investigate the estrogen level, estrogen receptors (α and β) immunoreactivities, muscle mass and functions, and parvalbumin (PV) levels in the extensor digitorum longus (EDL) and the gastrocnemius muscles of ovariectomized rats. Adult female Wistar rats (12 weeks old) were divided into five groups: sham-operated (SHAM), and ovariectomized (E0) groups that received 10 weeks of estrogen replacements of 0μg/kg (E0), 10μg/kg (E10), 20μg/kg (E20) and 40μg/kg (E40). The estrogen levels, ER α and ER β immunoreactivities, muscle fiber sizes and contractivities and the PV levels were reduced in the E0 group, but increased in all the estrogen replacement groups in both muscles. This study indicated that the reduction of estrogen levels led to a decrease of both ER α and ER β resulting in a decline in muscle mass and PV levels. The decrease of PV levels affected muscle performance, whereas estrogen replacement increased both the ER α and ER β. The increase in the PV levels may result in an improvement of muscle performance. This may explain one mechanism of estrogen on muscle mass and strength in estrogen dependent sarcopenia.