Plasticity of GABAA Receptors during Pregnancy and Postpartum Period: From Gene to Function

Advances in Psychotropic Treatment for Pregnant Women: Efficacy, Adverse Outcomes, and Therapeutic Monitoring

Advancements in psychotropic therapy for pregnant women are pivotal for addressing maternal mental health during the perinatal period. Screening for mood and anxiety symptoms during pregnancy is recommended to enable early intervention. Psychotropic medications, including antidepressants, benzodiazepines, antipsychotics, and mood stabilizers, are commonly used, but challenges remain regarding their safety and efficacy during pregnancy. Pregnancy induces significant changes in pharmacokinetics, necessitating personalized dosing strategies and careful monitoring. Real-time monitoring technologies, such as smartphone-integrated platforms and home-based monitoring, enhance accessibility and accuracy. Prospective studies and collaboration among healthcare providers are essential for evidence-based guidelines and optimal treatment strategies. Reducing stigma around mental health during pregnancy is crucial to ensure women seek help and discuss treatment options, promoting understanding and acceptance within the community.

GABA system as the cause and effect in early development

GABA is the primary inhibitory neurotransmitter in the adult brain and through its actions on GABAARs, it protects against excitotoxicity and seizure activity, ensures temporal fidelity of neurotransmission, and regulates concerted rhythmic activity of neuronal populations. In the developing brain, the development of GABAergic neurons precedes that of glutamatergic neurons and the GABA system serves as a guide and framework for the development of other brain systems. Despite this early start, the maturation of the GABA system also continues well into the early postnatal period. In this review, we organize evidence around two scenarios based on the essential and protracted nature of GABA system development: 1) disruptions in the development of the GABA system can lead to large scale disruptions in other developmental processes (i.e., GABA as the cause), 2) protracted maturation of this system makes it vulnerable to the effects of developmental insults (i.e., GABA as the effect). While ample evidence supports the importance of GABA/GABAAR system in both scenarios, large gaps in existing knowledge prevent strong mechanistic conclusions.

Antidepressant effects of activation of infralimbic cortex via upregulation of BDNF and β-catenin in an estradiol withdrawal model

RATIONALE

Clinical and preclinical studies have demonstrated that estradiol withdrawal after delivery is one of important factors involved in the pathogenesis of postpartum depression (PPD). The infralimbic cortex (IL) is related to anxiety and mood disorders. Whether IL neurons mediate PPD is still unclear.

OBJECTIVES

This study was to observe the antidepressant effect and expression of BDNF and β-catenin in IL by allopregnanolone (ALLO) treatment or the selective activation or inhibition of IL neurons using a chemogenetic approach in a pseudopregnancy model of PPD.

METHODS

Administration of estradiol combined with progesterone and the abrupt withdrawal of estradiol simulated the pregnancy and early postpartum periods to induce depression in ovariectomized rats. The relative expression levels of β-catenin and BDNF were observed by western blotting.

RESULTS

Immobility time was significantly increased in the forced swim test and open-arm movement was reduced in the elevated plus maze test in the estradiol-withdrawn rats. After ALLO treatment, the immobility time were lower and open-arm traveling times higher than those of the estradiol-withdrawn rats. Meanwhile, the expression level of BDNF or β-catenin in the IL was reduced significantly in estradiol-withdrawn rats, which was prevented by treatment with ALLO. The hM3Dq chemogenetic activation of pyramidal neurons in the IL reversed the immobility and open-arm travel time trends in the estradiol-withdrawal rat model, but chemogenetic inhibition of IL neurons failed to affect this. Upregulated BDNF and β-catenin expression and increased c-Fos in the basolateral amygdala were found following IL neuron excitation in model rats.

CONCLUSIONS

Our results demonstrated that pseudopregnancy and estradiol withdrawal produced depressive-like behavior and anxiety. ALLO treatment or specific excitement of IL pyramidal neurons relieved abnormal behaviors and upregulated BDNF and β-catenin expression in the IL in the PPD model, suggesting that hypofunction of IL neurons may be involved in the pathogenesis of PPD.

Activation of σ-1 receptor mitigates estrogen withdrawal-induced anxiety/depressive-like behavior in mice via restoration of GABA/glutamate signaling and neuroplasticity in the hippocampus

Postpartum depression (PPD) is a significant contributor to maternal morbidity and mortality. The Sigma-1 (σ-1) receptor has received increasing attention in recent years because of its ability to link different signaling systems and exert its function in the brain through chaperone actions, especially in neuropsychiatric disorders. YL-0919, a novel σ-1 receptor agonist developed by our institute, has shown antidepressive and anxiolytic effects in a variety of animal models, but effects on PPD have not been revealed. In the present study, excitatory/inhibitory signaling in the hippocampus was reflected by GABA and glutamate and their associated excitatory-inhibitory receptor proteins, the HPA axis hormones in the hippocampus were assessed by ELISA. Finally, immunofluorescence for markers of newborn neuron were undertaken in the dentate gyri, along with dendritic spine staining and dendritic arborization tracing. YL-0919 rapidly improves anxiety and depressive-like behavior in PPD-like mice within one week, along with normalizing the excitation/inhibition signaling as well as the HPA axis activity. YL-0919 rescued the decrease in hippocampal dendritic complexity and spine density induced by estrogen withdrawal. The study results suggest that YL-0919 elicits a therapeutic effect on PPD-like mice; therefore, the σ-1 receptor may be a novel promising target for PPD treatment in the future.

The Impact of Environmental Benzene, Toluene, Ethylbenzene, and Xylene Exposure on Blood-Based DNA Methylation Profiles in Pregnant African American Women from Detroit

African American women in the United States have a high risk of adverse pregnancy outcomes. DNA methylation is a potential mechanism by which exposure to BTEX (benzene, toluene, ethylbenzene, and xylenes) may cause adverse pregnancy outcomes. Data are from the Maternal Stress Study, which recruited African American women in the second trimester of pregnancy from February 2009 to June 2010. DNA methylation was measured in archived DNA from venous blood collected in the second trimester. Trimester-specific exposure to airshed BTEX was estimated using maternal self-reported addresses and geospatial models of ambient air pollution developed as part of the Geospatial Determinants of Health Outcomes Consortium. Among the 64 women with exposure and outcome data available, 46 differentially methylated regions (DMRs) were associated with BTEX exposure (FDR adjusted p-value < 0.05) using a DMR-based epigenome-wide association study approach. Overall, 89% of DMRs consistently exhibited hypomethylation with increasing BTEX exposure. Biological pathway analysis identified 11 enriched pathways, with the top 3 involving gamma-aminobutyric acid receptor signaling, oxytocin in brain signaling, and the gustation pathway. These findings highlight the potential impact of BTEX on DNA methylation in pregnant women.

Mood disorders and hormonal status across women's life: a narrative review

Depressive disorders and anxiety states represent one of the most frequent psychiatric pathologies occurring transiently in vulnerable women throughout their life, from puberty to menopause. It is now known that sex hormones play a key role on the nervous system, interfering with neuronal plasticity and enhancing the processes of learning, memory, cognition, and mood. Numerous mechanisms are at the base of these processes, displaying interactions between estrogen and serotoninergic, dopaminergic, and GABAergic receptors at the central level. Therefore, given the sexual steroids fluctuations throughout the entire female lifespan, and considering the role played by sex hormones at the central level, it is not surprising to observe the onset of mood or neurodegenerative disorders over time. This is especially true for women in hormonal transition phase, such as puberty, postpartum and the menopausal transition. Moreover, all these conditions are characterized by hormone withdrawal, imbalance, or modifications due to menopausal hormone therapies or contraceptives which could prompt to a deterioration of mood and cognition impairment or to an improvement in the quality of life. More studies are needed to better understand the hormone-related effects on the nervous system, and the underlying pathways involved in transitional or chronic mood disorders, to promote new patient-specific therapeutic strategies more effective than the current ones and tailored according to the individual need and women's life period.

A Comprehensive Review on Postpartum Depression

One of the most common psychological effects following childbirth is postpartum depression. Postpartum depression (PPD) has a significant negative impact on the child's emotional, mental as well as intellectual development if left untreated, which can later have long-term complications. Later in life, it also results in the mother developing obsessive-compulsive disorder and anxiety. Many psychological risk factors are linked with PPD. The pathophysiology of the development of PPD is explained by different models like biological, psychological, integrated, and evolutionary models, which relate the result of the condition with particular conditions and factors. This article also explains the role of methyldopa as a medication used during pregnancy and the postpartum phase with the development of PPD. There are different mechanisms by which methyldopa causes depression. The large-scale screening of the condition can be done by Edinburgh Postnatal Depression Scale (EPDS). The diagnosis can be made by clinical assessment, simple self-report instruments, and questionnaires provided to mothers. Currently, there has not been any specific treatment for PPD, but selective serotonin reuptake inhibitors (SSRIs) like sertraline are effective in acute management. Venlafaxine and desvenlafaxine are serotonin-norepinephrine reuptake inhibitors used for the relief of symptoms. The SSRI and tricyclic antidepressants (TCA) used in combination have a prophylactic role in PPD. Nowadays, women prefer psychological therapies, complementary health practices, and neuromodulatory interventions like electroconvulsive therapy more than previous pharmacological treatments of depression. Allopregnanolone drug made into sterile solution brexanolone leads to a rapid decline of PPD symptoms. PPD is a common and severe disorder that affects many mothers following childbirth but is ignored and not given much importance. Later it affects the child's psychological and intellectual abilities and mother-child bonding. We can easily prevent it by early diagnosis and timely care and management of the mother. Understanding the underlying pathophysiology would also go a long way in preventing and managing the disorder.

Postpartum depression: A role for psychedelics?

BACKGROUND

Postpartum depression (PPD) is a major public health concern and has, at its core, a sense of maternal 'disconnection' - from the self, the infant, and the support system. While PPD bears similarities with MDD, there is increasing evidence for its distinct nature, especially with the unique aspect of the mother-infant relationship. Current treatment modalities for PPD, largely based on those used in major depressive disorder (MDD), have low remission rates with emerging evidence for treatment resistance. It is, therefore, necessary to explore alternative avenues of treatment for PPD.

OBJECTIVE

In this narrative review, we outline the potential therapeutic rationale for serotonergic psychedelics in the treatment of PPD, and highlight safety and pragmatic considerations for the use of psychedelics in the postpartum period.

METHODS

We examined the available evidence for the treatment of PPD and the evidence for psychedelics in the treatment of MDD. We explored safety considerations in the use of psychedelics in the postpartum period.

RESULTS

There is increasing evidence for safety, and encouraging signals for efficacy, of psilocybin in the treatment of MDD. Psilocybin has been shown to catalyse a sense of 'reconnection' in participants with MDD. This effect in PPD, by fostering a sense of 'reconnection' for the mother, may allow for improved mood and maternal sensitivity towards the infant, which can positively impact maternal role gratification and the mother-infant relationship.

CONCLUSION

Psychedelic assisted therapy in PPD may have a positive effect on the mother-infant dyad and warrants further examination.

GABA System Modifications During Periods of Hormonal Flux Across the Female Lifespan

The female lifespan is marked by periods of dramatic hormonal fluctuation. Changes in the ovarian hormones estradiol and progesterone, in addition to the progesterone metabolite allopregnanolone, are among the most significant and have been shown to have widespread effects on the brain. This review summarizes current understanding of alterations that occur within the GABA system during the major hormonal transition periods of puberty, the ovarian cycle, pregnancy and the postpartum period, as well as reproductive aging. The functional impacts of altered inhibitory activity during these times are also discussed. Lastly, avenues for future research are identified, which, if pursued, can broaden understanding of the GABA system in the female brain and potentially lead to better treatments for women experiencing changes in brain function at each of these hormonal transition periods.

Relating neurosteroid modulation of inhibitory neurotransmission to behaviour

Studies in the 1980s revealed endogenous metabolites of progesterone and deoxycorticosterone to be potent, efficacious, positive allosteric modulators (PAMs) of the GABA_A receptor (GABA_A R). The discovery that such steroids are locally synthesised in the central nervous system (CNS) promoted the thesis that neural inhibition in the CNS may be "fine-tuned" by these neurosteroids to influence behaviour. In preclinical studies, these neurosteroids exhibited anxiolytic, anticonvulsant, analgesic and sedative properties and, at relatively high doses, induced a state of general anaesthesia, a profile consistent with their interaction with GABA_A Rs. However, realising the therapeutic potential of either endogenous neurosteroids or synthetic "neuroactive" steroids has proven challenging. Recent approval by the Food and Drug Administration of the use of allopregnanolone (brexanolone) to treat postpartum depression has rekindled enthusiasm for exploring their potential as new medicines. Although neurosteroids are selective for GABA_A Rs, they exhibit little or no selectivity across the many GABA_A R subtypes. Nevertheless, a relatively minor population of receptors incorporating the δ-subunit (δ-GABA_A Rs) appears to be an important contributor to their behavioural effects. Here, we consider how neurosteroids acting upon GABA_A Rs influence neuronal signalling, as well as how such effects may acutely and persistently influence behaviour, and explore the case for developing selective PAMs of δ-GABA_A R subtypes for the treatment of psychiatric disorders.

GABA in the medial prefrontal cortex regulates anxiety-like behavior during the postpartum period

The postpartum period is commonly accompanied by emotional changes, which for many new mothers includes a reduction in anxiety. Previous research in rodents has shown that the postpartum attenuation in anxiety is dependent on offspring contact and has further implicated enhanced GABAergic neurotransmission as an underlying mechanism. However, the specific brain regions where GABA acts to regulate the offspring-induced reduction in postpartum anxiety requires further investigation. Here, we test the hypothesis that offspring interactions suppress anxiety-like behavior in postpartum female rats via GABA signaling in the medial prefrontal cortex (mPFC). Our results show a postpartum reduction in anxiety-like behavior, an effect which was abolished by localized infusion of the GABAA receptor antagonist bicuculline in the mPFC. We also show that activation of GABAA receptors in the mPFC by the agonist muscimol was effective in restoring anxiolyisis in mothers separated from their pups. Lastly, we show that heightened anxiety-like behavior in pup-separated mothers was accompanied by a lower number and percentage of activated GABAergic neurons within the mPFC. Together, these results suggest that mother-offspring interactions reduce anxiety-like behavior in postpartum females via GABAA neurotransmission in the mPFC and in doing so provide insight into mechanisms that may become dysfunctional in mothers who experience high postpartum anxiety.

Postpartum Depression: Current Status and Possible Identification Using Biomarkers

Postpartum depression (PPD) is a serious health issue that can affect about 15% of the female population within after giving birth. It often conveys significant negative consequences to the offsprings. The symptoms and risk factors are somewhat similar to those found in non-postpartum depression. The main difference resides in the fact that PPD is triggered by postpartum specific factors, including especially biological changes in the hormone levels. Patients are usually diagnosed using a questionnaire onsite or in a clinic. Treatment of PPD often involves psychotherapy and antidepressant medications. In recent years, there have been more researches on the identification of biological markers for PPD. In this review, we will focus on the current research status of PPD, with an emphasis on the recent progress made on the identification of PPD biomarkers.

Progesterone - Friend or foe?

Estradiol is the "prototypic" sex hormone of women. Yet, women have another sex hormone, which is often disregarded: Progesterone. The goal of this article is to provide a comprehensive review on progesterone, and its metabolite allopregnanolone, emphasizing three key areas: biological properties, main functions, and effects on mood in women. Recent years of intensive research on progesterone and allopregnanolone have paved the way for new treatment of postpartum depression. However, treatment for premenstrual syndrome and premenstrual dysphoric disorder as well as contraception that women can use without risking mental health problems are still needed. As far as progesterone is concerned, we might be dealing with a two-edged sword: while its metabolite allopregnanolone has been proven useful for treatment of PPD, it may trigger negative symptoms in women with PMS and PMDD. Overall, our current knowledge on the beneficial and harmful effects of progesterone is limited and further research is imperative.

Machine learning on drug-specific data to predict small molecule teratogenicity

Pregnant women are an especially vulnerable population, given the sensitivity of a developing fetus to chemical exposures. However, prescribing behavior for the gravid patient is guided on limited human data and conflicting cases of adverse outcomes due to the exclusion of pregnant populations from randomized, controlled trials. These factors increase risk for adverse drug outcomes and reduce quality of care for pregnant populations. Herein, we propose the application of artificial intelligence to systematically predict the teratogenicity of a prescriptible small molecule from information inherent to the drug. Using unsupervised and supervised machine learning, our model probes all small molecules with known structure and teratogenicity data published in research-amenable formats to identify patterns among structural, meta-structural, and in vitro bioactivity data for each drug and its teratogenicity score. With this workflow, we discovered three chemical functionalities that predispose a drug towards increased teratogenicity and two moieties with potentially protective effects. Our models predict three clinically-relevant classes of teratogenicity with AUC = 0.8 and nearly double the predictive accuracy of a blind control for the same task, suggesting successful modeling. We also present extensive barriers to translational research that restrict data-driven studies in pregnancy and therapeutically "orphan" pregnant populations. Collectively, this work represents a first-in-kind platform for the application of computing to study and predict teratogenicity.

Allopregnanolone in postpartum depression: Role in pathophysiology and treatment

Postpartum depression (PPD) is a unique subtype of major depressive disorder and a substantial contributor to maternal morbidity and mortality. In addition to affecting the mother, PPD can have short- and long-term consequences for the infant and partner. The precise etiology of PPD is unknown, but proposed mechanisms include altered regulation of stress response pathways, such as the hypothalamic-pituitary-adrenal axis, and dysfunctional gamma-aminobutyric acid (GABA) signaling, and functional linkages exist between these pathways. Current PPD pharmacotherapies are not directly related to these proposed pathophysiologies. In this review, we focus on the potential role of GABAergic signaling and the GABA_A receptor positive allosteric modulator allopregnanolone in PPD. Data implicating GABAergic signaling and allopregnanolone in PPD are discussed in the context of the development of brexanolone injection, an intravenous formulation of allopregnanolone recently approved by the United States Food and Drug Administration for the treatment of adult women with PPD.

Realising the therapeutic potential of neuroactive steroid modulators of the GABAA receptor

In the 1980s particular endogenous metabolites of progesterone and of deoxycorticosterone were revealed to be potent, efficacious, positive allosteric modulators (PAMs) of the GABA_A receptor (GABA_AR). These reports were followed by the discovery that such steroids may be synthesised not only in peripheral endocrine glands, but locally in the central nervous system (CNS), to potentially act as paracrine, or autocrine "neurosteroid" messengers, thereby fine tuning neuronal inhibition. These discoveries triggered enthusiasm to elucidate the physiological role of such neurosteroids and explore whether their levels may be perturbed in particular psychiatric and neurological disorders. In preclinical studies the GABA_AR-active steroids were shown to exhibit anxiolytic, anticonvulsant, analgesic and sedative properties and at relatively high doses to induce a state of general anaesthesia. Collectively, these findings encouraged efforts to investigate the therapeutic potential of neurosteroids and related synthetic analogues. However, following over 30 years of investigation, realising their possible medical potential has proved challenging. The recent FDA approval for the natural neurosteroid allopregnanolone (brexanolone) to treat postpartum depression (PPD) should trigger renewed enthusiasm for neurosteroid research. Here we focus on the influence of neuroactive steroids on GABA-ergic signalling and on the challenges faced in developing such steroids as anaesthetics, sedatives, analgesics, anticonvulsants, antidepressants and as treatments for neurodegenerative disorders.

Mechanistic insights into autocrine and paracrine roles of endothelial GABA signaling in the embryonic forebrain

The developing cerebral cortex uses a complex developmental plan involving angiogenesis, neurogenesis and neuronal migration. Our recent studies have highlighted the importance of endothelial cell secreted GABA signaling in the embryonic forebrain and established novel autonomous links between blood vessels and the origin of neuropsychiatric diseases. A GABA pathway operates in both endothelial cells and GABAergic neurons of the embryonic telencephalon; however, while the neuronal GABA pathway has been extensively studied, little is known about the endothelial GABA pathway. Our recently generated Vgat endothelial cell knockout mouse model that blocks GABA release from endothelial cells, serves as a new tool to study how endothelial GABA signaling shapes angiogenesis and neurovascular interactions during prenatal development. Quantitative gene expression profiling reveals that the endothelial GABA signaling pathway influences genes connected to specific processes like endothelial cell proliferation, differentiation, migration, tight junction formation, vascular sprouting and integrity. It also shows how components of the neuronal GABA pathway, for instance receptor mediated signaling, cell cycle related components and transcription factors are affected in the absence of endothelial GABA release. Taken together, our findings delineate the close relationship between vascular and nervous systems that begin early in embryogenesis establishing their future interactions and interdependence.

Neuroactive Steroids and GABAergic Involvement in the Neuroendocrine Dysfunction Associated With Major Depressive Disorder and Postpartum Depression

Stress and previous adverse life events are well-established risk factors for depression. Further, neuroendocrine disruptions are associated with both major depressive disorder (MDD) and postpartum depression (PPD). However, the mechanisms whereby stress contributes to the underlying neurobiology of depression remains poorly understood. The hypothalamic-pituitary-adrenal (HPA) axis, which mediates the body's neuroendocrine response to stress, is tightly controlled by GABAergic signaling and there is accumulating evidence that GABAergic dysfunction contributes to the impact of stress on depression. GABAergic signaling plays a critical role in the neurobiological effects of stress, not only by tightly controlling the activity of the HPA axis, but also mediating stress effects in stress-related brain regions. Deficits in neuroactive steroids and neurosteroids, some of which are positive allosteric modulators of GABA_A receptors (GABA_ARs), such as allopregnanolone and THDOC, have also been implicated in MDD and PPD, further supporting a role for GABAergic signaling in depression. Alterations in neurosteroid levels and GABAergic signaling are implicated as potential contributing factors to neuroendocrine dysfunction and vulnerability to MDD and PPD. Further, potential novel treatment strategies targeting these proposed underlying neurobiological mechanisms are discussed. The evidence summarized in the current review supports the notion that MDD and PPD are stress-related psychiatric disorders involving neurosteroids and GABAergic dysfunction.

Pathophysiological mechanisms implicated in postpartum depression

This review aims to summarize the diverse proposed pathophysiological mechanisms contributing to postpartum depression, highlighting both clinical and basic science research findings. The risk factors for developing postpartum depression are discussed, which may provide insight into potential neurobiological underpinnings. The evidence supporting a role for neuroendocrine changes, neuroinflammation, neurotransmitter alterations, circuit dysfunction, and the involvement of genetics and epigenetics in the pathophysiology of postpartum depression are discussed. This review integrates clinical and preclinical findings and highlights the diversity in the patient population, in which numerous pathophysiological changes may contribute to this disorder. Finally, we attempt to integrate these findings to understand how diverse neurobiological changes may contribute to a common pathological phenotype. This review is meant to serve as a comprehensive resource reviewing the proposed pathophysiological mechanisms underlying postpartum depression.

Role of GABAA receptors in alcohol use disorders suggested by chronic intermittent ethanol (CIE) rodent model

GABAergic inhibitory transmission is involved in the acute and chronic effects of ethanol on the brain and behavior. One-dose ethanol exposure induces transient plastic changes in GABAA receptor subunit levels, composition, and regional and subcellular localization. Rapid down-regulation of early responder δ subunit-containing GABAA receptor subtypes mediating ethanol-sensitive tonic inhibitory currents in critical neuronal circuits corresponds to rapid tolerance to ethanol's behavioral responses. Slightly slower, α1 subunit-containing GABAA receptor subtypes mediating ethanol-insensitive synaptic inhibition are down-regulated, corresponding to tolerance to additional ethanol behaviors plus cross-tolerance to other GABAergic drugs including benzodiazepines, anesthetics, and neurosteroids, especially sedative-hypnotic effects. Compensatory up-regulation of synaptically localized α4 and α2 subunit-containing GABAA receptor subtypes, mediating ethanol-sensitive synaptic inhibitory currents follow, but exhibit altered physio-pharmacology, seizure susceptibility, hyperexcitability, anxiety, and tolerance to GABAergic positive allosteric modulators, corresponding to heightened alcohol withdrawal syndrome. All these changes (behavioral, physiological, and biochemical) induced by ethanol administration are transient and return to normal in a few days. After chronic intermittent ethanol (CIE) treatment the same changes are observed but they become persistent after 30 or more doses, lasting for at least 120 days in the rat, and probably for life. We conclude that the ethanol-induced changes in GABAA receptors represent aberrant plasticity contributing critically to ethanol dependence and increased voluntary consumption. We suggest that the craving, drug-seeking, and increased consumption in the rat model are tied to ethanol-induced plastic changes in GABAA receptors, importantly the development of ethanol-sensitive synaptic GABAA receptor-mediating inhibitory currents that participate in maintained positive reward actions of ethanol on critical neuronal circuits. These probably disinhibit nerve endings of inhibitory GABAergic neurons on dopamine reward circuit cells, and limbic system circuits mediating anxiolysis in hippocampus and amygdala. We further suggest that the GABAA receptors contributing to alcohol dependence in the rat and presumably in human alcohol use disorders (AUD) are the ethanol-induced up-regulated subtypes containing α4 and most importantly α2 subunits. These mediate critical aspects of the positive reinforcement of ethanol in the dependent chronic user while alleviating heightened withdrawal symptoms experienced whenever ethanol is absent. The speculative conclusions based on firm observations are readily testable.