Analog Of Allopregnanolone Research Articles

Zuranolone for the Treatment of Postpartum Depression.

To review the safety, efficacy, and tolerability of zuranolone for the treatment of postpartum depression. A literature search was conducted through PubMed using the following terms: zuranolone, postpartum depression, perinatal depression, SAGE-217, and allopregnanolone analogue. Articles describing the pharmacology, pharmacokinetics, efficacy, safety, and/or tolerability of zuranolone were included in this review. Zuranolone is an allopregnanolone analogue that works through modulation of the GABAA receptor. Clinical trials have demonstrated that compared with placebo, zuranolone is effective in treating patients with postpartum depression. Common adverse events associated with zuranolone include fatigue, somnolence, headache, dizziness, diarrhea, sedation, upper respiratory tract infection, and nausea. Pharmacotherapeutic options to treat postpartum depression include selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitors, with the medication brexanolone (the first allopregnanolone analogue) reserved for severe postpartum depression. Zuranolone, the newest medication in its class, is without the same limitations as brexanolone, thus affording providers an additional easy-to-use option for treating postpartum depression.

A Brief Review of Zuranolone

Zuranolone, a novel analog of allopregnanolone, has been approved by the U.S. Food and Drug Administration (FDA) as the first oral medication approved for the treatment of postpartum depression in adults. Developed by Sage Therapeutics under the brand name Zurzuvae, zuranolone was approved by the FDA on August 4th, 2023.1 Zuranolone is a modified version of brexanolone (sold under the brand name Zulpresso), an intravenously administered allopregnanolone formulation that was previously the only FDA-approved medication for postpartum depression. Zuranolone offers a more accessible treatment option for patients with efficacy established in clinical trials. Its approval expands the treatment landscape for depression, especially in the peripartum period, and marks a crucial step forward in psychopharmacological innovation.

Supportive care of female hormones in brain health: what and how?

Female hormones, functioning as neuroactive steroids, are utilized beyond menopausal hormone therapy. The rapid onset of allopregnanolone analogs, such as brexanolone and zuranolone, in treating depression, and the effectiveness of megestrol acetate in addressing appetite and weight gain, prompted the Food and Drug Administration to authorize the use of progesterone for treating postpartum depression and cancer-related cachexia. Progesterone has also been found to alleviate neuropathic pain in animal studies. These off-label applications offer a promising option for patients with advanced cancer who often experience various mood disorders such as depression, persistent pain, social isolation, and physical complications like cachexia. These patients have shown low tolerance to opioids and mood-regulating medications. However, the potential risks and uncertainties associated with hormone therapy treatment modalities can be daunting for both patients and medical professionals. This review aims to offer a comprehensive understanding of the non-reproductive functions and mechanisms of female hormones in brain health.

Ganaxolone: First FDA-Approved Medicine for the Treatment of Seizures Associated with Cyclin-dependent Kinase-like 5 Deficiency Disorder.

The neurosteroids progesterone and allopregnanolone control numerous neuroprotective functions in neural tissues, including inhibition of epileptic seizures and cell death. Ganaxolone (3α-hydroxy-3β-methyl-5α-pregnan-20-one) (GNX) is the 3β-methylated synthetic analog of allopregnanolone and an allosteric GABAA positive modulator. Ganaxolone reduces the frequency of CDD-associated seizures.

Endocrinological Treatment Targets for Depressive Disorder.

Depressive disorder exhibits heterogeneity in clinical presentation, progression, and treatment outcomes. While conventional antidepressants based on the monoamine hypothesis benefit many patients, a significant proportion remains unresponsive or fails to fully recover. An individualized integrative treatment approach, considering diverse pathophysiologies, holds promise for these individuals. The endocrine system, governing physiological regulation and organ homeostasis, plays a pivotal role in central nervous system functions. Dysregulations in endocrine system are major cause of depressive disorder due to other medical conditions. Subtle endocrine abnormalities, such as subclinical hypothyroidism, are associated with depression. Conversely, depressive disorder correlates with endocrine-related biomarkers. Fluctuations in sex hormone levels related to female reproduction, elevate depression risk in susceptible subjects. Consequently, extensive research has explored treatment strategies involving the endocrine system. Treatment guidelines recommend tri-iodothyronine augmentation for resistant depression, while allopregnanolone analogs have gained approval for postpartum depression, with ongoing investigations for broader depressive disorders. This book chapter will introduce the relationship between the endocrine system and depressive disorders, presenting clinical findings on neuroendocrinological treatments for depression.

Impaired Endogenous Neurosteroid Signaling Contributes to Behavioral Deficits Associated With Chronic Stress

BackgroundChronic stress is a major risk factor for psychiatric illnesses, including depression. However, the pathophysiological mechanisms whereby stress leads to mood disorders remain unclear. Allopregnanolone acts as a positive allosteric modulator preferentially on δ subunit–containing GABAA (gamma-aminobutyric acid A) receptors. Accumulating clinical and preclinical evidence supports the antidepressant effects of exogenous administration of allopregnanolone analogs; yet, the role of endogenous allopregnanolone in the pathophysiology of depression remains unknown. MethodsWe utilized a chronic unpredictable stress (CUS) mouse model, followed by behavioral and biochemical assays, to examine whether altered neurosteroid signaling contributes to behavioral outcomes following CUS. We subsequently performed in vivo CRISPR (clustered regularly interspaced short palindromic repeats) knockdown of rate-limiting enzymes involved in allopregnanolone synthesis, 5α-reductase type 1 and 2 (5α1/2), in addition to lentiviral overexpression of 5α1/2 in the basolateral amygdala (BLA) of mice that underwent CUS to assess the impact of 5α1/2 on behavioral outcomes. ResultsThe expression of δ subunit–containing GABAA receptors and endogenous levels of allopregnanolone were reduced in the BLA following CUS. Treatment with an exogenous allopregnanolone analog, SGE-516, was sufficient to increase allopregnanolone levels in the BLA following CUS. Knockdown of 5α1/2 in the BLA mimicked the behavioral outcomes associated with CUS. Conversely, overexpression of 5α1/2 in the BLA improved behavioral outcomes following CUS. ConclusionsOur findings demonstrate that chronic stress impairs endogenous neurosteroid signaling in the BLA, which is sufficient to induce behavioral deficits. Further, these studies suggest that allopregnanolone-based treatments may directly target the underlying pathophysiology of mood disorders suggesting that targeting endogenous neurosteroidogenesis may offer a novel therapeutic strategy.

Evaluating changes in GABAergic and glutamatergic pathways in early life following prenatal stress and postnatal neurosteroid supplementation

BackgroundA correct balance of activity of the GABA and glutamate systems is vital for optimal neurodevelopment and general CNS function, and the dysregulation of this balance has been implicated in a number of neurological conditions. Maternal exposure to stressors is known to have long lasting, deleterious impacts on neurobehaviour, and similarly, results in dysregulation of inhibitory and excitatory pathways in the offspring. The current study aimed to examine effects on these pathways in a guinea pig model of prenatal stress and to elucidate whether increased neuroprotective support by postnatal neurosteroid supplementation would ameliorate adverse outcomes. MethodsPrenatal stress was achieved by exposing pregnant guinea pigs dams to a strobe light for 2hrs/day on gestational age (GA) 50, 55, 60 and 65. Dams were allowed to spontaneously deliver (~GA70) and pups were orally administered either allopregnanolone analogue, ganaxolone (5 mg/kg/day in 45% cyclodextrin), the translocator protein (TSPO) agonist, emapunil (XBD173; 0.3 mg/kg/day in 1% tragacanth gum) or vehicle on postnatal days (PND) 1–7. Hippocampal samples were collected at PND30 to measure relative mRNA expression of components involved in the inhibitory GABAergic pathway and exctitatory glutamatergic pathway by real-time PCR. GABAergic interneurons were quantified by assessing immunohistochemical protein expression of markers parvalbumin, calbindin and calretinin. ResultsmRNA expression of GABAergic pathway components at one week of age indicated immature expression profiles of the GABAA receptors as well as decreased GABA synthesis and transport suggesting reduced extrasynaptically-mediated tonic inhibition. Expression profiles of the pathways examined evolved between one week and one month of age but an imbalance in inhibitory/excitatory components persisted. The allopregnanolone analogue ganaxolone offered some protection against excitotoxicity in female hippocampus, however neurosteroid supplementation with ganaxolone or emapunil were unable to fully correct the GABAergic/glutamatergic imbalance observed following prenatal stress. ConclusionPrenatal stress leads to programmed lasting effects on the major inhibitory and excitatory pathways in the guinea pig brain that continue evolving between the equivalent of early and late childhood. Neurosteroid therapies particularly improved outcomes in females. Further studies are required to identify additional therapeutic targets that are able to fully restore imbalances in the excitatory and inhibitory systems, which may act to prevent development of childhood behavioural disorders.

PCDH19 interplay with GABA(A) receptors: a window to DEE9 pathogenetic mechanisms.

PCDH19 interplay with GABA(A) receptors: a window to DEE9 pathogenetic mechanisms.

Allopregnanolone Mediates Affective Switching Through Modulation of Oscillatory States in the Basolateral Amygdala

BackgroundBrexanolone (allopregnanolone) was recently approved by the Food and Drug Administration for the treatment of postpartum depression, demonstrating long-lasting antidepressant effects. Despite our understanding of the mechanism of action of neurosteroids as positive allosteric modulators of GABAA (gamma-aminobutyric acid A) receptors, we still do not fully understand how allopregnanolone exerts persistent antidepressant effects. MethodsWe used electroencephalogram recordings in rats and humans along with local field potential, functional magnetic resonance imaging, and behavioral tests in mice to assess the impact of neurosteroids on network states in brain regions implicated in mood and used optogenetic manipulations to directly examine their relationship to behavioral states. ResultsWe demonstrated that allopregnanolone and synthetic neuroactive steroid analogs with molecular pharmacology similar to allopregnanolone (SGE-516 [tool compound] and zuranolone [SAGE-217, investigational compound]) modulate oscillations across species. We further demonstrated a critical role for interneurons in generating oscillations in the basolateral amygdala (BLA) and a role for δ-containing GABAA receptors in mediating the ability of neurosteroids to modulate network and behavioral states. Allopregnanolone in the BLA enhances BLA high theta oscillations (6–12 Hz) through δ-containing GABAA receptors, a mechanism distinct from other GABAA positive allosteric modulators, such as benzodiazepines, and alters behavioral states. Treatment with the allopregnanolone analog SGE-516 protects mice from chronic stress–induced disruption of network and behavioral states, which is correlated with the modulation of theta oscillations in the BLA. Optogenetic manipulation of the network state influences the behavioral state after chronic unpredictable stress. ConclusionsOur findings demonstrate a novel molecular and cellular mechanism mediating the well-established anxiolytic and antidepressant effects of neuroactive steroids.

Treating Postpartum Depression: What Do We Know about Brexanolone?

Postpartum depression (PPD) is defined as the onset of major depressive disorder in mothers, occurring during pregnancy or within 4 weeks post-delivery. With 7% of pregnancy-related death in the United States owing to mental health conditions, including PPD, and a global prevalence of 12%, PPD is a growing public health concern. In 2019, the Food and Drug Administration (FDA) approved brexanolone, an exogenous analog of allopregnanolone, as the first ever drug to be specifically indicated for treating patients with PPD. This approval was preceded by an open-label study and three randomized placebo-controlled trials, each assessing the safety, tolerability, and efficacy of brexanolone, using mean Hamilton Rating Scale for Depression (HAM-D) score reduction as the primary outcome. In each randomized controlled trial, the drug was administered as an intravenous infusion given over 60 h. Enrolled participants were followed up on days 7 and 30 to evaluate the sustained effect. A statistically significant reduction in mean HAM-D score compared to placebo was observed in all three studies, supporting brexanolone’s use in treating moderate-to-severe PPD. Therefore, this article attempts to briefly review the pharmacology of brexanolone, evaluate the latest available clinical data and outcomes concerning its use, reevaluate its position as a ‘breakthrough’ in managing PPD, and review the cost-related barriers to its worldwide standardized use.

Anti-apoptotic Actions of Allopregnanolone and Ganaxolone Mediated Through Membrane Progesterone Receptors (PAQRs) in Neuronal Cells.

The neurosteroids progesterone and allopregnanolone regulate numerous neuroprotective functions in neural tissues including inhibition of epileptic seizures and cell death. Many of progesterone's actions are mediated through the nuclear progesterone receptor (PR), while allopregnanolone is widely considered to be devoid of hormonal activity and instead acts through modulation of GABA-A receptor activity. However, allopregnanolone can also exert hormonal actions in neuronal cells through binding and activating membrane progesterone receptors (mPRs) belonging to the progestin and adipoQ receptor (PAQR) family. The distribution and functions of the five mPR subtypes (α, β, γ, δ, ε) in neural tissues are briefly reviewed. mPRδ has the highest binding affinity for allopregnanolone and is highly expressed throughout the human brain. Low concentrations (20 nM) of allopregnanolone act through mPRδ to stimulate G protein (Gs)-dependent signaling pathways resulting in reduced cell death and apoptosis in mPRδ-transfected cells. The 3-methylated synthetic analog of allopregnanolone, ganaxolone, is currently undergoing clinical trials as a promising GABA-A receptor-selective antiepileptic drug (AED). New data show that low concentrations (20 nM) of ganaxolone also activate mPRδ signaling and exert anti-apoptotic actions through this receptor. Preliminary evidence suggests that ganaxolone can also exert neuroprotective effects by activating inhibitory G protein (Gi)-dependent signaling through mPRα and/or mPRβ in neuronal cells. The results indicate that mPRs are likely intermediaries in multiple actions of natural and synthetic neurosteroids in the brain. Potential off-target effects of ganaxolone through activation of mPRs in patients receiving long-term treatment for epilepsy and other disorders should be considered and warrant further investigation.

SUN-303 Effects of Open-Label, Adjunctive Ganaxalone Treatment on Resistant Depression in Postmenopausal Women: A Pilot Study

Resistance to selective serotonin reuptake inhibitor and serotonin norepinephrine reuptake inhibitor treatment occurs in about 50% to 70% of patients with major depressive disorder (MDD), a condition associated with significant morbidity that affects women at higher rates than men. Few well-tolerated, effective augmentation therapies are available for such patients, and new therapeutic strategies for resistant depression are needed. The neuroactive steroid metabolite of progesterone, allopregnanolone, is a positive allosteric modulator of GABAA receptors and a putative treatment for mood disorders. We performed a pilot study to determine whether an oral allopregnanolone analog (ganaxolone) may be effective adjunctive therapy for resistant depression in postmenopausal women. Ten postmenopausal women (age 62.8±6.3 years, range 53–69) with resistant depression [current DSM-IV major depressive episode per the Structured Clinical Interview for DSM-IV, Montgomery-Asberg Depression Rating Scale (MADRS) ≥16 despite treatment with an adequately dosed antidepressant for ≥6 weeks] were studied. Open-label ganaxolone (225 mg BID, increased to 450 mg BID if tolerated) was administered for 8 weeks, followed by a 2-week taper. Mean total MADRS depression score (primary endpoint) decreased by 8 weeks [24.4±1.6 (SEM) to 12.8±2.9, p=0.015] and persisted over the two-week taper (p=0.019); 44% of subjects experienced response (score decrease ≥50%) and remission (final score <10), which persisted in 100% and 50% of subjects at 10 weeks, respectively. Secondary endpoints showed significant improvement, including the Inventory of Depressive Symptomatology-Self-Report (IDS-SR; p=0.003), MADRS Reduced Sleep subscale (p<0.001), Symptoms of Depression Questionnaire (SDQ) total score (p=0.012), and SDQ subscales for disruptions in sleep quality (p=0.003) and changes in appetite and weight (p=0.009) over 8 weeks. No significant effects were observed on quality of life or sexual function. All subjects experienced sleepiness and fatigue; 60% experienced dizziness. In conclusion, adjunctive ganaxolone in this open label pilot study appeared to exert antidepressant effects in postmenopausal women with resistant depression but produces sedation with twice-daily dosing. The observed positive effects on sleep and the potential for sustained treatment effects merit further study, as ganaxolone may be particularly beneficial to patients with depression and insomnia. Randomized, placebo-controlled studies are necessary to rule out placebo effects. Given the sedation experienced by most participants, nighttime dosing only should be considered for future studies. Finally, should rigorous studies confirm an antidepressant effect, it will be important to identify subsets of women who respond (e.g. women with neuroactive steroid dysregulation) and mechanisms of action.

A photoreactive analog of allopregnanolone enables identification of steroid-binding sites in a nicotinic acetylcholine receptor

Many neuroactive steroids potently and allosterically modulate pentameric ligand-gated ion channels, including GABAA receptors (GABAAR) and nicotinic acetylcholine receptors (nAChRs). Allopregnanolone and its synthetic analog alphaxalone are GABAAR-positive allosteric modulators (PAMs), whereas alphaxalone and most neuroactive steroids are nAChR inhibitors. In this report, we used 11β-(p-azidotetrafluorobenzoyloxy)allopregnanolone (F4N3Bzoxy-AP), a general anesthetic and photoreactive allopregnanolone analog that is a potent GABAAR PAM, to characterize steroid-binding sites in the Torpedo α2βγδ nAChR in its native membrane environment. We found that F4N3Bzoxy-AP (IC50 = 31 μm) is 7-fold more potent than alphaxalone in inhibiting binding of the channel blocker [3H]tenocyclidine to nAChRs in the desensitized state. At 300 μm, neither steroid inhibited binding of [3H]tetracaine, a closed-state selective channel blocker, or of [3H]acetylcholine. Photolabeling identified three distinct [3H]F4N3Bzoxy-AP-binding sites in the nAChR transmembrane domain: 1) in the ion channel, identified by photolabeling in the M2 helices of βVal-261 and δVal-269 (position M2-13'); 2) at the interface between the αM1 and αM4 helices, identified by photolabeling in αM1 (αCys-222/αLeu-223); and 3) at the lipid-protein interface involving γTrp-453 (M4), a residue photolabeled by small lipophilic probes and promegestone, a steroid nAChR antagonist. Photolabeling in the ion channel and αM1 was higher in the nAChR-desensitized state than in the resting state and inhibitable by promegestone. These results directly indicate a steroid-binding site in the nAChR ion channel and identify additional steroid-binding sites also occupied by other lipophilic nAChR antagonists.

Pharmacotherapy of Postpartum Depression: Current Approaches and Novel Drug Development.

Postpartum depression is one of the most common complications of childbirth. Untreated postpartum depression can have substantial adverse effects on the well-being of the mother and child, negatively impacting child cognitive, behavioral, and emotional development with lasting consequences. There are a number of therapeutic interventions for postpartum depression including pharmacotherapy, psychotherapy, neuromodulation, and hormonal therapy among others, most of which have been adapted from the treatment of major depressive disorder outside of the peripartum period. Current evidence of antidepressant treatment for postpartum depression is limited by the small number of randomized clinical trials, underpowered samples, and the lack of long-term follow-up. The peripartum period is characterized by rapid and significant physiological change in plasma levels of endocrine hormones, peptides, and neuroactive steroids. Evidence supporting the role of neuroactive steroids and γ-aminobutyric acid (GABA) in the pathophysiology of postpartum depression led to the investigation of synthetic neuroactive steroids and their analogs as potential treatment for postpartum depression. Brexanolone, a soluble proprietary intravenous preparation of synthetic allopregnanolone, has been developed. A recent series of open-label and placebo-controlled randomized clinical trials of brexanolone in postpartum depression demonstrated a rapid reduction in depressive symptoms, and has led to the submission for regulatory approval to the US Food and Drug Administration (decision due in March 2019). SAGE-217, an allopregnanolone analog, with oral bioavailability, was recently tested in a randomized, double-blind, placebo-controlled phase III study in severe postpartum depression, with reportedly positive results. Finally, a 3β-methylated synthetic analog of allopregnanolone, ganaxolone, is being tested in both intravenous and oral forms, in randomized, double-blind, placebo-controlled phase II studies in severe postpartum depression.

Antiepileptic potential of ganaxolone

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Allopregnanolone and its analog BR 297 rescue neuronal cells from oxidative stress-induced death through bioenergetic improvement

Allopregnanolone (AP) is supposed to exert beneficial actions including anxiolysis, analgesia, neurogenesis and neuroprotection. However, although mitochondrial dysfunctions are evidenced in neurodegenerative diseases, AP actions against neurodegeneration-induced mitochondrial deficits have never been investigated. Also, the therapeutic exploitation of AP is limited by its difficulty to pass the liver and its rapid clearance after sulfation or glucuronidation of its 3-hydroxyl group. Therefore, the characterization of novel potent neuroprotective analogs of AP may be of great interest. Thus, we synthesized a set of AP analogs (ANS) and investigated their ability to counteract APP-overexpression-evoked bioenergetic deficits and to protect against oxidative stress-induced death of control and APP-transfected SH-SY5Y cells known as a reliable cellular model of Alzheimer's disease (AD). Especially, we examined whether ANS were more efficient than AP to reduce mitochondrial dysfunctions or bioenergetic decrease leading to neuronal cell death.Our results showed that the ANS BR 297 exhibits notable advantages over AP with regards to both protection of mitochondrial functions and reduction of oxidative stress. Indeed, under physiological conditions, BR 297 does not promote cell proliferation but efficiently ameliorates the bioenergetics by increasing cellular ATP level and mitochondrial respiration. Under oxidative stress situations, BR 297 treatment, which decreases ROS levels, improves mitochondrial respiration and cell survival, appears more potent than AP to protect control and APP-transfected cells against H2O2-induced death.Our findings lend further support to the neuroprotective effects of BR 297 emphasizing this analog as a promising therapeutic tool to counteract age- and AD-related bioenergetic deficits.

Novel analogs of allopregnanolone show improved efficiency and specificity in neuroprotection and stimulation of proliferation.

The natural neurosteroid allopregnanolone exerts beneficial effects in animal models of neurodegenerative diseases, nervous system injury and peripheral neuropathies. It not only has anti-apoptotic activity, but also promotes proliferation of progenitor cells. With respect to using it as a therapeutic tool, such pleiotropic actions might create unwanted side effects. Therefore, we have synthesized allopregnanolone analogs and analyzed their neuroprotective and proliferative effects to identify compounds with higher efficiency and less ambiguous biological actions. Proliferation-promoting effects of 3α and 3β isomers of 3-O-allyl-allopregnanolone and 12 oxo-allopregnanolone were studied in adult subventricular zone stem cell cultures and in primary hippocampal cultures by measuring 5-ethynyl-2'-deoxyuridine incorporation. Neuroprotective activity against amyloid beta 42-induced cell death was determined by quantifying caspase 3/7 activity. The 3α isomers significantly stimulated proliferation in all culture systems, whereas the 3β isomers were ineffective. The stimulatory effect of 3α-O-allyl-allopregnanolone was significantly higher than that of allopregnanolone. In neural stem cell cultures, 3α-O-allyl-allopregnanolone specifically enhanced proliferation of Nestin-positive progenitors. In addition, it promoted the differentiation of doublecortin-positive neurons. In neural stem cell cultures treated with amyloid beta 42, both the α and β isomers of O-allyl- allopregnanolone showed increased neuroprotective activity as compared to allopregnanolone, completely preventing amyloid-induced caspase 3/7 activation. The 12 oxo-allopregnanolone analogs were ineffective. These results identify structural allopregnanolone analogs with higher anti-apoptotic and proliferation-promoting activity than the natural neurosteroid. Interestingly, stereoisomers of the analogs were found to have distinct profiles of activity raising the possibility of exploiting the neuroprotective properties of neurosteroids with or without simultaneously stimulating neurogenesis. Cover Image for this issue: doi: 10.1111/jnc.13344.

Effect of nucleus accumbens shell infusions of ganaxolone or gaboxadol on ethanol consumption in mice

Allopregnanolone (ALLO) is an endogenous neuroactive steroid thought to alter the reinforcement value of alcohol (ethanol) due to its actions as a positive modulator of the GABAA receptor (GABAAR). Extrasynaptic GABAARs may be a particularly sensitive target of ethanol and neuroactive steroids. Previous work showed that systemic injections of an ALLO analog, ganaxolone (GAN), or an extrasynaptic GABAAR agonist (gaboxadol; THIP) decreased ethanol intake in male mice with limited access to ethanol. The present studies tested whether activation of GABAARs in the nucleus accumbens (NAc) shell by GAN or THIP was sufficient to reduce ethanol intake. C57BL/6J male mice had 2-h access to 10% ethanol (10E) and water, and 10E intake was measured following site-specific infusions of GAN or THIP. Decreases in limited-access 10E consumption were observed following site-specific bilateral infusions of either drug into the NAc shell. Significant changes in intake were absent when the drugs were infused in a region dorsal to the target site (GAN) or into the lateral ventricle (THIP). Locomotor data confirmed that the decreases in intake were not due to a sedative effect of the drugs. These data demonstrate the sufficiency of GABAAR activation by a positive allosteric modulator or an agonist with selectivity for extrasynaptic GABAARs to decrease ethanol consumption in mice. Importantly, more refined GABAAR-active targets that decrease ethanol intake may enhance our understanding and ability to treat alcohol use disorders.

The effects of betamethasone on allopregnanolone concentrations and brain development in preterm fetal sheep

The risk of preterm delivery often means that the fetus will be exposed to exogenous synthetic glucocorticoids to accelerate fetal lung maturation, but effects on other organs, particularly the brain, are not understood. The neurosteroid allopregnanolone (AP) is a GABAA receptor agonist that influences fetal brain development and has neuroprotective properties. In this study we determined the impact of maternal glucocorticoid (betamethasone) administration on brain development and AP synthesis in preterm fetal sheep. Pregnant ewes underwent surgery at 105 days gestation for implantation of fetal catheters. Ewes received either betamethasone (BM; 11.4 mg; n = 10) or vehicle (saline; n = 5) by i.m injection on days five (BM1) and six (BM2) following surgery. Five fetuses of the BM treated ewes received an infusion of alfaxalone (20 mg) over 48 h commencing 30 min prior to BM1. All animals were euthanased on day 7, and the fetal brains collected to determine AP concentrations and histopathology. BM significantly reduced AP levels in the fetal brain and placental cotyledons, and also in fetal plasma without altering progesterone concentrations. There was a significant decrease in the number of myelinating cells in subcortical white matter, but no change to total oligodendrocyte number. Co-administration of the AP analogue analog alfaxalone with BM prevented this change in MBP expression. BM, given at a dose clinically prescribed to accelerate lung maturation, adversely affects neurosteroid levels in the preterm fetal brain, and affects the maturational profile of white matter development; these effects were mitigated by the co-administration of alfaxolone.

Differences in the reinstatement of ethanol seeking with ganaxolone and gaboxadol

The endogenous neuroactive steroid allopregnanolone (ALLO) has previously been shown to induce reinstatement of ethanol seeking in rodents. ALLO is a positive allosteric modulator at both synaptic and extrasynaptic GABAA receptors. The contribution of each class of GABAA receptors in mediating reinstatement of ethanol seeking is unknown. The first aim of the present study was to determine whether ganaxolone (GAN), a longer-acting synthetic analog of ALLO, also promotes reinstatement of ethanol seeking. The second aim was to examine whether preferentially activating extrasynaptic GABAA receptors with the selective agonist gaboxadol (THIP) was sufficient to reinstate responding for ethanol in mice. Male C57BL/6J mice were trained to lever press for access to a 10% ethanol (v/v) solution (10E), using a sucrose-fading procedure. Following extinction of the lever-pressing behavior, systemic THIP (0, 4 and 6mg/kg) and GAN (0, 10, and 15mg/kg) were tested for their ability to reinstate ethanol-appropriate responding in the absence of 10E access. GAN significantly increased lever pressing on the previously active lever, while THIP did not alter lever-pressing behavior. The results of this study suggest that direct activation of extrasynaptic GABAA receptors at the GABA site is not sufficient to induce ethanol seeking in the reinstatement procedure. Future studies are necessary to elucidate the mechanisms and brain areas by which differences in the pharmacological activity of GAN and THIP at the GABAA receptor contribute to the dissimilarity in their effect on the reinstatement of ethanol seeking. Nonetheless, based on the increased use of these drugs in clinical trials across multiple disease states, the effects of GAN or THIP on alcohol seeking may be an important consideration if these drugs are to be used clinically in a population with a co-occurring alcohol use disorder.