Monomeric Amyloid Peptide-induced Toxicity in Human Oligodendrocyte Cell Line and Mouse Brain Primary Mixed-glial Cell Cultures: Evidence for a Neuroprotective Effect of Neurosteroid 3α-O-allyl-allopregnanolone.

Amyloid-peptide (Aß) monomeric forms (ABM) occurring in presymptomatic Alzheimer's disease (AD) brain are thought to be devoid of neurotoxicity while the transition/aggregation of ABM into oligomers is determinant for Aß-induced toxicity since Aß is predominantly monomeric up to 3 µM and aggregates over this concentration. However, recent imaging and/or histopathological investigations revealed alterations of myelin in prodromal AD brain in absence of aggregated Aß oligomers, suggesting that ABM may induce toxicity in myelin-producing cells in early AD-stages. To check this hypothesis, here we studied ABM effects on the viability of the Human oligodendrocyte cell line (HOG), a reliable oligodendrocyte model producing myelin proteins. Furthermore, to mimic closely interactions between oligodendrocytes and other glial cells regulating myelination, we investigated also ABM effects on mouse brain primary mixed-glial cell cultures. Various methods were combined to show that ABM concentrations (600 nM-1 µM), extremely lower than 3 µM, significantly decreased HOG cell and mouse brain primary mixed-glial cell survival. Interestingly, flow-cytometry studies using specific cell-type markers demonstrated that oligodendrocytes represent the most vulnerable glial cell population affected by ABM toxicity. Our work also shows that the neurosteroid 3α-O-allyl-allopregnanolone BR351 (250 and 500 nM) efficiently prevented ABM-induced HOG and brain primary glial cell toxicity. Bicuculline (50-100 nM), the GABA-A-receptor antagonist, was unable to block/reduce BR351 effect against ABM-induced HOG and primary glial cell toxicity, suggesting that BR351-evoked neuroprotection of these cells may not depend on GABA-A-receptor allosterically modulated by neurosteroids. Altogether, our results suggest that further exploration of BR351 therapeutic potential may offer interesting perspectives to develop effective neuroprotective strategies.

Effects of ganaxolone on non-seizure outcomes in CDKL5 Deficiency Disorder: Double-blind placebo-controlled randomized trial.

CDKL5 deficiency disorder (CDD) is a rare developmental and epileptic encephalopathy. Ganaxolone, a neuroactive steroid, reduces the frequency of major motor seizures in children with CDD. This analysis explored the effect of ganaxolone on non-seizure outcomes. Children (2-19 years) with genetically confirmed CDD and ≥ 16 major motor seizures per month were enrolled in a double-blind randomized placebo-controlled trial. Ganaxolone or placebo was administered three times daily for 17 weeks. Behaviour was measured with the Anxiety, Depression and Mood Scale (ADAMS), daytime sleepiness with the Child Health Sleep Questionnaire, and quality of life with the Quality of Life Inventory-Disability (QI-Disability) scale. Scores were compared using ANOVA, adjusted for age, sex, number of anti-seizure mediations, baseline 28-day major motor seizure frequency, baseline developmental skills, and behaviour, sleep or quality of life scores. 101 children with CDD (39 clinical sites, 8 countries) were randomized. Median (IQR) age was 6 (3-10) years, 79.2 % were female, and 50 received ganaxolone. After 17 weeks of treatment, Manic/Hyperactive scores (mean difference 1.27, 95%CI -2.38,-0.16) and Compulsive Behaviour scores (mean difference 0.58, 95%CI -1.14,-0.01) were lower (improved) in the ganaxolone group compared with the placebo group. Daytime sleepiness scores were similar between groups. The total change in QOL score for children in the ganaxolone group was 2.6 points (95%CI -1.74,7.02) higher (improved) than in the placebo group but without statistical significance. Along with better seizure control, children who received ganaxolone had improved behavioural scores in select domains compared to placebo.

An update on approved and emerging drugs for the treatment of postpartum depression.

Depression, anxiety and psychotic disorders are common perinatal mental health disorders in the postpartum period. Depressive symptoms that occur postpartum are also present in the prenatal period in 50% of patients. Risk factors for the development of postpartum depression include poor relationship with the partner, lack of social support, mother’s low socioeconomic status and multiparity. It has been determined that reproductive hormones change significantly during peripartum. Progesterone is one of these hormones and acts on the central nervous system starting from the fetal period; neurogenesis, neuromodulation, sedation are some of these effects. It has also been observed that progesterone has positive effects on learning, memory and mood. Progesterone exerts its effects on the central nervous system by converting into its metabolite allopregnanolone. Allopregnanolone is one of the neuroactive steroids, and found in similar amounts in the circulation of pregnant women and fetuses. It acts on synaptic and extrasynaptic γ-aminobutyric acid type A (GABAA) receptors and is a positive allosteric modulator of the GABAA receptor. Allopregnanolone increases both the receptor’s opening frequency and its open duration and improves GABAergic current. Low serum allopregnanolone levels in the second trimester are predictive of postpartum depression. Each 1 ng/mL increase in serum allopregnanolone level reduces the risk of development of postpartum depression by 63%. Brexanolone and zuranolone are synthetic allopregnanolone preparations approved by the FDA for use in female patients with postpartum depression. They act via positive allosteric modulation on the GABAA receptor. Brexanolone is administered via intravenous infusion at varying infusion rates in a healthcare facility over 60 hours. Its effect starts immediately after treatment and continues until the 30th day of follow-up, and depressive mood does not recur. Zuranolone was developed for oral use, and administered as a single dose of 50 mg after a fatty meal. Their effectiveness has been demonstrated in patients with treatment-resistant depression. The development of other novel agents that act on the GABAA receptor and other pathways for the treatment of postpartum depression is in progress.

Synthesis and evaluation of neuroactive steroids with novel pharmacophore at C-21 let identify a compound with advantageous PK profile and higher EC50 and Emax as PAM on GABAA receptor.

Zuranolone (SAGE-217) is a neuroactive steroid (γ-aminobutyric acid)A (GABAA) receptor positive allosteric modulator (PAM) as the first oral drug approved by the FDA in 2023, which is used to treat patients with postpartum depression (PPD). SAGE-217 has a "black box" warning with impairing ability to drive or engage in other potentially hazardous activities. In addition, SAGE-217 can cause CNS depressant effects such as somnolence and confusion, suicidal thoughts and behavior and embryo-fetal toxicity. Based on the structure-activity relationship (SAR) of SAGE-217, a total of 28 neuroactive steroids with novel pharmacophore at C-21 modulated SAGE-217 derivatives were designed and synthesized. The biological activities were evaluated by both synaptic α1ß2γ2 GABAA receptor and extrasynaptic α4ß3δ GABAA receptor cell assays. The optimal compound S28 exhibited much more potent potency and similar efficacy at extrasynaptic GABAA receptor than SAGE-217. Different from above, compound S28 exhibited similar potency and lower efficacy at synaptic GABAA receptor than SAGE-217, which were consistent with the analysis of molecular docking and dynamics simulation results. The appropriate lower efficacy at synaptic GABAA receptor of compound S28 might contribute to reduce the side effects of excessive sedation. Furthermore, compound S28 was demonstrated to have excellent in vivo pharmacokinetic (PK) parameters, robust in vivo pharmacodynamic (PD) effects and good safety profiles. Therefore, compound S28 represents a potentially promising treatment of PPD candidate that warrants further investigation.

Neurosteroids mediate and modulate the effects of pro-inflammatory stimulation and toll-like receptors on hippocampal plasticity and learning.

Pro-inflammatory changes contribute to multiple neuropsychiatric illnesses. Understanding how these changes are involved in illnesses and identifying strategies to alter inflammatory responses offer paths to potentially novel treatments. We previously found that acute pro-inflammatory stimulation with high (µg/ml) lipopolysaccharide (LPS) for 10-15 min dampens long-term potentiation (LTP) in the hippocampus and impairs learning. Effects of LPS involved non-canonical inflammasome signaling but were independent of toll-like receptor 4 (TLR4), a known LPS receptor. Low (ng/ml) LPS also inhibits LTP when administered for 2-4 h, and here we report that this LPS exposure requires TLR4. We also found that effects of low LPS on LTP involve the oxysterol, 25-hydroxycholesterol, akin to high LPS. Effects of high LPS on LTP are blocked by inhibiting synthesis of 5α-reduced neurosteroids, indicating that neurosteroids mediate LTP inhibition. 5α-Neurosteroids also have anti-inflammatory effects, and we found that exogenous allopregnanolone (AlloP), a key 5α-reduced steroid, prevented effects of low but not high LPS on LTP. We also found that activation of TLR2, TLR3 and TLR7 inhibited LTP and that AlloP prevented the effects of TLR2 and TLR7, but not TLR3. The enantiomer of AlloP, a steroid that has anti-inflammatory actions but low activity at GABAA receptors, prevented LTP inhibition by TLR2, TLR3 and TLR7. In vivo, both AlloP enantiomers prevented LPS-induced learning defects. These studies indicate that neurosteroids play complex roles in network effects of acute neuroinflammation and have potential importance for development of AlloP analogues as therapeutic agents.

Gut bacteria convert glucocorticoids into progestins in the presence of hydrogen gas.

Recent studies suggest that human-associated bacteria interact with host-produced steroids, but the mechanisms and physiological impact of such interactions remain unclear. Here, we show that the human gut bacteria Gordonibacter pamelaeae and Eggerthella lenta convert abundant biliary corticoids into progestins through 21-dehydroxylation, thereby transforming a class of immuno- and metabo-regulatory steroids into a class of sex hormones and neurosteroids. Using comparative genomics, homologous expression, and heterologous expression, we identify a bacterial gene cluster that performs 21-dehydroxylation. We also uncover an unexpected role for hydrogen gas production by gut commensals in promoting 21-dehydroxylation, suggesting that hydrogen modulates secondary metabolism in the gut. Levels of certain bacterial progestins, including allopregnanolone, better known as brexanolone, an FDA-approved drug for postpartum depression, are substantially increased in feces from pregnant humans. Thus, bacterial conversion of corticoids into progestins may affect host physiology, particularly in the context of pregnancy and women's health.

Zuranolone Concentrations in the Breast Milk of Healthy, Lactating Individuals: Results From a Phase 1 Open-Label Study.

PURPOSE/BACKGROUND: Zuranolone is a positive allosteric modulator of both synaptic and extrasynaptic γ-aminobutyric acid type A receptors and a neuroactive steroid approved as an oral, once-daily, 14-day treatment course for adults with postpartum depression in the United States. This study assessed zuranolone transfer into breast milk. METHODS/PROCEDURES: Healthy, nonpregnant, lactating adult female participants received once-daily 30 mg zuranolone from day (D)1 through D5 in this phase 1 open-label study. The relative infant dose (RID; weight-adjusted proportion of the maternal dose in breast milk over 24 hours) for 30 mg zuranolone was assessed at D5. An RID for 50 mg zuranolone was estimated using a simulation approach across a range of infant ages and weights. FINDINGS/RESULTS: Of 15 enrolled participants (mean age, 30.1 years), 14 completed the study. The mean RID for 30 mg zuranolone at D5 was 0.357%; the mean steady-state milk volume over D3 to D5 decreased from baseline by 8.3%. Overall unbound zuranolone in plasma was low (≤0.49%). Plasma concentrations peaked at D5 before decreasing in a biexponential manner. There was strong concordance between the temporal profiles of zuranolone concentrations in plasma and breast milk. The estimated mean RID for 50 mg zuranolone based on a milk intake of 200 mL/kg per day was 0.984%. All treatment-emergent adverse events reported by participants were mild, the most common being dizziness (n = 3). IMPLICATIONS/CONCLUSIONS: Zuranolone transfer into the breast milk of healthy, nonpregnant, lactating adult female participants was low; the estimated RID for 50 mg zuranolone was <1%, well below the <10% threshold generally considered compatible with breastfeeding.

ShuYu capsule alleviates emotional and physical symptoms of premenstrual dysphoric disorder: Impact on ALLO decline and GABAA receptor δ subunit in the PAG area.

Premenstrual dysphoric disorder (PMDD) is a severe subtype of premenstrual syndrome in women of reproductive age, with its pathogenesis linked to the heightened sensitivity of type A γ -aminobutyric acid receptors (GABAAR) to neuroactive steroid hormone changes, particularly allopregnanolone (ALLO). While a low dose of fluoxetine, a classic selective serotonin reuptake inhibitor, is commonly used as a first-line drug to alleviate emotional disorders in PMDD in clinical settings, its mechanism of action is related to ALLO-GABAA receptor function. However, treating PMDD requires attention to both emotional and physical symptoms, such as pain sensitivity. This study aims to investigate the efficacy of ShuYu capsules, a traditional Chinese medicine, in simultaneously treating emotional and physical symptoms in a rat model of PMDD. Specifically, our focus centres on the midbrain periaqueductal grey (PAG), a region associated with emotion regulation and susceptibility to hyperalgesia. Considering the underlying mechanisms of ALLO-GABAA receptor function in the PAG region, we conducted a series of experiments to evaluate and define the effects of ShuYu capsules and uncover the relationship between the drug's efficacy and ALLO concentration fluctuations on GABAA receptor function in the PAG region. Our findings demonstrate that ShuYu capsules significantly improved oestrous cycle-dependant depression-like behaviour and reduced stress-induced hyperalgesia in rats with PMDD. Similar to the low dose of fluoxetine, ShuYu capsules targeted and mitigated the sharp decline in ALLO, rescued the upregulation of GABAAR subunit function, and activated PAG neurons in PMDD rats. The observed effects of ShuYu capsules suggest a central mechanism underlying PMDD symptoms, involving ALLO_GABAA receptor function in the PAG region. This study highlights the potential of traditional Chinese medicine in addressing both emotional and physical symptoms associated with PMDD, shedding light on novel therapeutic approaches for this condition.

Allopregnanolone in the peripartum: Correlates, concentrations, and challenges - A systematic review.

BACKGROUND: Allopregnanolone (ALLO) is a metabolite of progesterone and a neuroactive steroid hormone. As a positive allosteric modulator of gamma-aminobutyric acid (GABA) receptors, ALLO seems to have antidepressant and anxiolytic effects, and was therefore approved as a specific medication for the treatment of postpartum depression in 2019. Despite the growing number of publications investigating ALLO levels, results on the biological and psychological correlates in the peripartum period remain inconsistent, possibly due to methodological challenges regarding measurement. To date, however, there is no systematic review examining the correlates, concentrations, and challenges in measuring ALLO in peripartum women. METHOD: A systematic literature search of PubMed and PsycINFO was conducted in August 2023. Original research articles that measured ALLO concentrations in peripartum women were included. Reports were excluded if they were not original research, included non-human subjects, did not include peripartum women, did not include ALLO measurement as an outcome, included (pharmacological) interventions, constituted method validations, or used the same cohort as another study. RESULTS: The literature search yielded 234 articles, and two articles were identified from other sources. After full-text screening, 19 articles (N = 1401) met the inclusion criteria, of which seven focused on biological correlates of ALLO and 12 on mood correlates. Of the latter, six found no association between ALLO and mood, four found a negative association, and two found a positive association. Overall, the results show an increase in ALLO levels during pregnancy and a decrease after birth, with levels then remaining low until six months postpartum. ALLO was most commonly measured in blood plasma and by gas chromatography-mass spectrometry (GC-MS). A significant matrix effect was found for blood serum and a significant method effect for radioimmunoassays (RIAs). A significant effect of time of measurement was found. CONCLUSION: ALLO measurement shows method and matrix effects. ALLO levels are higher when measured in serum compared to in plasma, and when measured using RIA compared to other methods. Time of measurement, study design, and standardization of measurement also influence the reliability of measurement and the interpretation of results.

The impact of pubertal stress and adult hormone exposure on the transcriptome of the developing hypothalamus.

Why individuals suffer negative consequences following stress is a complex phenomenon that is dictated by individual factors, the timing of stress within the lifespan, and when in the lifespan the consequences are measured. Women who undergo adverse childhood experiences are at risk for lasting biological consequences, including affective and stress dysregulation. We have shown that pubertal adversity is associated with a blunted hypothalamic-pituitary-adrenal axis glucocorticoid response in peripartum humans and mice. In mice, our prior examination of the paraventricular nucleus (PVN) of the hypothalamus showed that pubertal stress led to an upregulation of baseline mRNA expression of six immediate early genes (IEGs) in the PVN of adult, pregnant mice. Separately, we showed that the pregnancy-associated hormone allopregnanolone is necessary and sufficient to produce the blunted stress response phenotype in pubertally stressed mice. In the current study, we further examined a potential mechanistic role for the IEGs in the PVN. We found that in pubertally stressed adult female, but not male, mice, intra-PVN allopregnanolone was sufficient to recapitulate the baseline IEG mRNA expression profile previously observed in pubertally stressed, pregnant mice. We also examined baseline IEG mRNA expression during adolescence, where we found that IEGs have developmental trajectories that showed sex-specific disruption by pubertal stress. Altogether, these data establish that IEGs may act as a key molecular switch involved in increased vulnerability to negative outcomes in adult, pubertally stressed animals. How the factors that produce vulnerability combine throughout the lifespan is key to our understanding of the etiology of stress-related disorders.

First Oral Treatment Specific for Postpartum Depression.

Postpartum depression is one of the most common perinatal mood disorders. The U.S. Food and Drug Administration approved the first oral medication developed specifically for the treatment of postpartum depression in August 2023. Zuranolone, marketed under the brand name Zurzuvae (Sage Therapeutics, Inc. and Biogen), is thought to work similarly to other positive allosteric modulators of gamma-aminobutyric acid A receptors such as benzodiazepines. It can be used alone or as an adjunct to other oral antidepressant medication. Its 2-week regimen of once-daily oral administration provides women with postpartum depression the opportunity to maintain their daily routines in an outpatient setting. This article provides an overview of zuranolone, including indications, mechanism of action, potential adverse reactions, and implications for nursing practice.

Zuranolone: A Narrative Review of a New Oral Treatment for Postpartum Depression.

PURPOSE: Postpartum depression is a prevalent and overlooked mental disorder. Pathophysiology is thought to originate from a combination of biological and social factors, including hormones, and genetics. The consequences of untreated postpartum depression can be severe and negatively impact maternal and infant health. Zuranolone was approved as an oral agent in August 2023 for the treatment of postpartum depression in adults. The purpose of this article is evaluating the clinical aspects of zuranolone, including safety and efficacy pertaining to the drug and the clinical data that led to its approval. METHODS: A literature search was conducted using PubMed, Web of Science, and EMBASE with the terms postpartum depression, postpartum depression management, and zuranolone to locate relevant data for this narrative review. The prescribing information of zuranolone and clinicaltrials.gov were also utilized. FINDINGS: Two Phase III trials (Study 1-NCT04442503 and Study 2-NCT02978326) led to the approval of zuranolone by the Food and Drug Administration (FDA) based on clinically meaningful improvement in depressive symptoms. The trials met their primary endpoint, a change from baseline in HAM-D total score at day 15 (Study 1; 95% CI -6.3 to -1.7, P = 0.001: Study 2; 95% CI (-6.9 to -1.5, P = 0.003). IMPLICATIONS: Zuranolone, an oral and rapidly acting antidepressant, represents a promising new oral treatment option for individuals with postpartum depression.

The efficacy and safety of Zuranolone for treatment of depression: A systematic review and meta-analysis.

RATIONALE: Zuranolone, a newly FDA-approved synthetic neurosteroid, shows promise in treating depression. OBJECTIVES: Our aim is to evaluate Zuranolone's efficacy and safety in treating depression. METHODS: Five databases were searched until September 2023 for relevant randomized clinical trials evaluating the efficacy and safety of zuranolone. The potential risk of bias in the included trials was evaluated by the Cochrane Risk of Bias II guideline Data were extracted and pooled using Review Manager Software (RevMan 5.3). RESULTS: An analysis of eight studies highlights Zuranolone's efficacy in treating depression compared to placebo across most of the outcomes. Notably, the 30mg and 50mg doses demonstrated significant improvements in reducing HAM-D scores by over 50% within a 15-day follow-up (RR) of 1.46 (95% CI [1.27, 1.68], p < 0.0001) and 1.14 (95% CI [1.01, 1.3], p = 0.04). Additionally, the HAM-D ≤ 7% score analysis revealed significant enhancements with the 30mg dose over both 15-day (RR = 1.82, 95% CI [1.44, 2.31], p < 0.0001) and 45-day (RR = 1.43, 95% CI [1.16, 1.77], p = 0.0008) durations. Adverse Events Drug Discontinuation demonstrated no overall significant difference (OR = 1.33, 95% CI: [0.79, 2.23], p = 0.282). Further, specific adverse events, such as headache, showed no significant overall difference between Zuranolone and placebo (OR = 1.11, 95% CI: [0.84, 1.47], p = 0.47), with dose-dependent analysis revealing less headache in the 30 mg group. CONCLUSION: Zuranolone demonstrates favorable tolerability and safety, particularly at 30mg and 50mg doses after 15 days, suggesting its potential and effective treatment for depression.

A systematic review and meta-analysis on efficacy and safety of Ganaxolone in epilepsy.

INTRODUCTION: Ganaxolone has exhibited potential in managing seizures for epilepsy. This systematic review and meta-analysis aim to assess both the safety and efficacy of Ganaxolone for refractory epilepsy. METHODS: A thorough search of electronic databases was conducted to identify relevant randomized controlled trials involving patients with drug-resistant focal epilepsy and CDKL5 deficiency disorder. Efficacy and safety outcomes were extracted from the selected studies. Cochrane Review Manager was utilized for data synthesis and analysis, with risk ratios and mean differences calculated to evaluate the efficacy and safety profile of Ganaxolone. RESULTS: The meta-analysis included a total of five randomized controlled trials. Ganaxolone exhibited significant efficacy in reducing seizure frequency by at least 50% from baseline [RR 0.90 (95% CI: 0.83, 0.98), p = 0.02]. However, the results did not reach significance for reducing 28-day seizure frequency [Mean Difference -1.45 (95% CI: -3.39, 0.49), p = 0.14]. Ganaxolone exhibited a positive safety profile, with no statistically significant occurrence of adverse events [RR 1.30 (95% CI: 0.93, 1.83), p = 0.12] and adverse events leading to discontinuation of the study drug [RR 1.01 (95% CI: 0.42, 2.39), p = 0.99] compared to placebo. CONCLUSION: Ganaxolone presents itself as a viable therapeutic option for refractory epilepsy, showing efficacy in reducing seizure frequency and exhibited a favorable safety profile. PROSPERO REGISTRATION NUMBER: CRD42023434883.

Positive association between dehydroepiandrosterone (DHEA) and gene expression of the gamma-aminobutyric acid (GABA-A) receptor δ subunit.

Gamma-aminobutyric acid A (GABA-A) receptors in the cells of the immune system enhance anti-inflammatory responses by regulating cytokine secretion, cytotoxic responses, and cell activation. In the CNS, the formation of GABA-A subunits into a pentameric structure has been extensively studied; however, no such study has been conducted in the immune system. The objective of the present study was to examine associations between the levels of steroid hormones and GABA-A receptor δ subunit expression in the immune system. We focused on this subunit because GABA-A receptors that contain it become significantly more sensitive to steroid hormones. We collected 80 blood samples from reproductive age women for the purpose of analyzing dehydroepiandrosterone (DHEA), 17ß-estradiol, progesterone, and allopregnanolone using liquid chromatography-mass spectrometry (LC-MS). Furthermore, we extracted peripheral blood mononuclear cells (PBMCs) for determining mRNA expression levels of GABA-A receptor genes encoding the δ and ε subunits. We constructed linear mixed effect models for each GABA-A receptor subunit with all 4 steroid hormones, age, and age of menarche as predictors. Whereas DHEA was significantly associated with δ subunit expression (t-value = 2.981; p = 0.003), in line with our hypothesis, none of the steroid hormones were significantly associated with the expression of the ε subunit. Results of this study indicate that significant interactions between hormones from the steroid hormone biosynthesis pathway and GABAergic machinery from the immune cells may be utilized to expand models examining the molecular basis of inflammatory conditions.

Impact of NMDA receptors block versus GABA-A receptors modulation on synaptic plasticity and brain electrical activity in metabolic syndrome.

PURPOSE: Metabolic syndrome (MetS) is a common disorder associated with disturbed neurotransmitter homeostasis. Memantine, an N-methyl-d-aspartate receptor (NMDAR) antagonist, was first used in Alzheimer's disease. Allopregnanolone (Allo), a potent positive allosteric modulator of the Gamma-Amino-Butyric Acid (GABA)-A receptors, decreases in neurodegenerative diseases. The study investigated the impact of Memantine versus Allo administration on the animal model of MetS to clarify whether the mechanism of abnormalities is related more to excitatory or inhibitory neurotransmitter dysfunction. MATERIALS AND METHODS: Fifty-six male rats were allocated into 7 groups: 4 control groups, 1 MetS group, and 2 treated MetS groups. They underwent assessment of cognition-related behavior by open field and forced swimming tests, electroencephalogram (EEG) recording, serum markers confirming the establishment of MetS model and hippocampal Glial Fibrillary Acidic Protein (GFAP) and Brain-Derived Neurotrophic Factor (BDNF). RESULTS: Allo improved anxiety-like behavior and decreased grooming frequency compared to Memantine. Both drugs increased GFAP and BDNF expression, improving synaptic plasticity and cognition-related behaviors. The therapeutic effect of Allo was more beneficial regarding lipid profile and anxiety. We reported progressive slowing of EEG waves in the MetS group with Memantine and Allo treatment with increased relative theta and decreased relative delta rhythms. CONCLUSIONS: Both Allo and Memantine boosted the outcome parameters in the animal model of MetS. Allo markedly improved the anxiety-like behavior in the form of significantly decreased grooming frequency compared to the Memantine-treated groups. Both drugs were associated with increased hippocampal GFAP and BDNF expression, indicating an improvement in synaptic plasticity and so, cognition-related behaviors.

Neurosteroid Modulation of Synaptic and Extrasynaptic GABAA Receptors of the Mouse Nucleus Accumbens.

The recent approval of formulations of the endogenous neurosteroid allopregnanolone (brexanolone) and the synthetic neuroactive steroid SAGE-217 (zuranolone) to treat postpartum depression (PPD) has encouraged further research to elucidate why these potent enhancers of GABAAR function are clinically effective in this condition. Dopaminergic projections from the ventral tegmental area (VTA) to the nucleus accumbens are associated with reward/motivation and brain imaging studies report that individuals with PPD show reduced activity of this pathway in response to reward and infant engagement. However, the influence of neurosteroids on GABA-ergic transmission in the nucleus accumbens has received limited attention. Here, we investigate, in the medium spiny neurons (MSNs) of the mouse nucleus accumbens core, the effect of allopregnanolone, SAGE-217 and other endogenous and synthetic steroids of interest on fast phasic and tonic inhibition mediated by synaptic (α1/2ßγ2) and extrasynaptic (α4ßδ) GABAARs, respectively. We present evidence suggesting the resident tonic current results from the spontaneous opening of δ-GABAARs, where the steroid-enhanced tonic current is GABA-dependent. Furthermore, we demonstrate local neurosteroid synthesis in the accumbal slice preparation and reveal that GABA-ergic neurotransmission of MSNs is influenced by an endogenous neurosteroid tone. Given the dramatic fluctuations in allopregnanolone levels during pregnancy and postpartum, this neurosteroid-mediated local fine-tuning of GABAergic transmission in the MSNs will probably be perturbed.

Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment.

Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.

Involvement of the GABAA Receptor in the Antidepressant-Like Effects Produced by Low and High Doses of the Flavonoid Chrysin in the Rat: A Longitudinal Study.

BACKGROUND: The flavonoid chrysin produces rapid and long-lasting anxiolytic- and antidepressant-like effects in rats. However, it is not known whether low and high doses of chrysin produce differential anti-immobility effects through the Gamma-Aminobutyric Acid sub-type A (GABAA) receptor. The goal of this work was therefore to compare low and high doses of chrysin for their effects on depression-like behavior in a longitudinal study. Moreover, chrysin was compared with the serotonergic fluoxetine and Gamma-Aminobutyric Acid (GABA)ergic allopregnanolone, and its involvement with the GABAA receptor after chronic treatment was also investigated. METHODS: Male Wistar rats were assigned to five groups (n = 8 each): vehicle, 1 mg/kg chrysin, 5 mg/kg chrysin, 1 mg/kg fluoxetine, and 1 mg/kg allopregnanolone. In the first experiment, treatments were injected daily and the effects on locomotor activity and the forced swim test were evaluated at 0, 1, 14, and 28 days of treatment, and 48 h after the final treatment. In the second experiment, similar groups were treated for 28 days with injection of 1 mg/kg picrotoxin to investigate the role of the GABAA receptor. Depending on the experimental design, one- and two-way analysis of variance (ANOVA) tests were used for statistical analysis, with p < 0.05 set as the criteria for significance. RESULTS: In both experiments, the treatments did not alter locomotor activity. However, low and high doses of chrysin, allopregnanolone, and fluoxetine gradually produced antidepressant-like effects in the forced swim test, and maintained this effect for 48 h post-treatment, except with low dose chrysin. Picrotoxin blocked the antidepressant-like effects produced by low dose chrysin, but did not affect those produced by high dose chrysin, allopregnanolone, or fluoxetine. CONCLUSIONS: The differential antidepressant-like effects caused by low and high doses of chrysin are time-dependent. Low dose chrysin produces a rapid antidepressant-like effect, whereas high dose chrysin produces a delayed but sustained the effect, even 48 h after withdrawal. The effect with high dose chrysin was similar to that observed with allopregnanolone and fluoxetine. The mechanism for the antidepressant-like effect of low chrysin appears to be GABAergic, whereas the effect of high dose chrysin may involve other neurotransmission and neuromodulation systems related to the serotonergic system.

Local effect of allopregnanolone in rat ovarian steroidogenesis, follicular and corpora lutea development.

Allopregnanolone (ALLO) is a known neurosteroid and a progesterone metabolite synthesized in the ovary, CNS, PNS, adrenals and placenta. Its role in the neuroendocrine control of ovarian physiology has been studied, but its in situ ovarian effects are still largely unknown. The aims of this work were to characterize the effects of intrabursal ALLO administration on different ovarian parameters, and the probable mechanism of action. ALLO administration increased serum progesterone concentration and ovarian 3ß-HSD2 while decreasing 20α-HSD mRNA expression. ALLO increased the number of atretic follicles and the number of positive TUNEL granulosa and theca cells, while decreasing positive PCNA immunostaining. On the other hand, there was an increase in corpora lutea diameter and PCNA immunostaining, whereas the count of TUNEL-positive luteal cells decreased. Ovarian angiogenesis and the immunohistochemical expression of GABAA receptor increased after ALLO treatment. To evaluate if the ovarian GABAA receptor was involved in these effects, we conducted a functional experiment with a specific antagonist, bicuculline. The administration of bicuculline restored the number of atretic follicles and the diameter of corpora lutea to normal values. These results show the actions of ALLO on the ovarian physiology of the female rat during the follicular phase, some of them through the GABAA receptor. Intrabursal ALLO administration alters several processes of the ovarian morpho-physiology of the female rat, related to fertility and oocyte quality.