Hypothalamus-sympathetic-liver axis mediates the early phase of stress-induced hyperglycemia in the male mice.

Rapid glucose supply is crucial for animal survival during stress response. How the timescale of stress-induced glucose release precisely controlled by hypothalamic corticotropin-releasing hormone (CRH) neurons remains unclear. Here, we show that stress-induced hyperglycemia can be divided into at least two stages in male mice: the first fast stage is mediated by hypothalamus (paraventricular to ventromedial hypothalamus)-sympathetic (raphe pallidus nucleus to intermediolateral nucleus)-liver (HSL) axis activity; the second delayed stage is mediated by adrenal activity. Blocking the activity of HSL axis impairs predatory evoked flight responses, indicating that the HSL pathway activity is necessary for stress coping. We further reveal the intracellular signal cascade for CRH signal in the hypothalamus, which is mediated by GABAA receptor ß3 subunit phosphorylation at S408/409, results in prevention of GABAA receptor membrane recruitment. Thus, we uncovered the precise timescale of glucose supply during stress which is mediated by adrenal independent HSL and adrenal dependent pathway respectively.

Changes in D4 and GABAA subunit α3 receptors in the thalamic reticular nucleus caused by unilateral lesion of the globus pallidus.

The thalamic reticular nucleus controls information processing in thalamocortical neurons. GABAergic neurons present in this nucleus express the α3 subunit of post­synaptic GABAA receptors, which bind GABA from globus pallidus neurons. Pallidal neurons, in turn, have dopaminergic D4 receptors in their axon terminals. The thalamic reticular nucleus connects reciprocally with the thalamus, and it receives afferents from the brain cortex, as well as from other brain structures that have an important role in the modulation of the thalamic network. Based on the above, the purpose of this study was to assess the electrophysiological and molecular effects of unilateral lesion of the globus pallidus on the electric activity of the thalamic reticular nucleus. Two­month­old male rats were used. The right globus pallidus was lesioned with quinolinic acid. Seven days after the lesion, ipsilateral turning was registered, confirming the lesion. Afterward, electrophysiological evaluation of the right thalamic reticular nucleus' electrical activity was performed. Subsequently, mRNA expression for D4 receptors and subunit α3, as well as protein content were assessed in the right reticular nucleus. Pallidum lesion caused an increase in firing frequency and decreased firing bursts of reticular neurons. In addition, dopaminergic D4 mRNA, as well as protein increased. In contrast, GABAergic GABAA subunit α3 expression was suppressed, but protein content increased. These results show that the globus pallidus regulates firing in reticular neurons through D4 receptors and subunit α3 of GABAA receptor in the reticular nucleus of the thalamus.

GABA(A) Receptor Subunit (γ2, δ, ß1-3) Variants in Genetic Epilepsy: A Comprehensive Summary of 206 Clinical Cases.

Epilepsy is identified in individuals who experienced 2 or more unprovoked seizures occurring over 24 hours apart, which can have a profound impact on a person's neurobiological, cognitive, psychological, and social well-being. Epilepsy is considerably diverse, with classifications such as genetic epilepsy that result directly from a known or presumed genetic variant with the core symptoms of seizures. The GABAA receptor primarily functions as a heteropentamer, containing 3 of 8 subunit types: α, ß, γ, δ, ε, π, θ, and ρ. In the adult brain, the GABAA receptor is the primary inhibitory component in neural networks. The involvement of GABAA receptors in the pathogenesis of epilepsy has been proposed. We extensively reviewed all relevant clinical data of previously published cases of GABAA receptor subunit γ2, δ, ß1-3 variants included in PubMed up to February 2024, including the variant types, loci, postulated mechanisms, their relevant regions, first onset ages, and phenotypes. We summarized the postulated mechanisms of epileptic pathogenesis. We also divided the collected 206 cases of epilepsy into 4 epileptic phenotypes: genetic generalized epilepsies, focal epilepsy, developmental and epileptic encephalopathies, and epilepsy with fever sensibility. We showed that there were significant differences in the likelihood of the γ2, ß2, and ß3 subunit variants causing genetic generalized epilepsies, focal epilepsy, developmental and epileptic encephalopathies, and epilepsy with fever sensibility. Patients with the ß3 subunit variant seemed related to an earlier first onset age. Our review supports that GABAA receptor subunit variants are a crucial area of epilepsy research and treatment exploration.

Divergent mechanisms of steroid inhibition in the human ρ1 GABAA receptor.

ρ-type γ-aminobutyric acid-A (GABAA) receptors are widely distributed in the retina and brain, and are potential drug targets for the treatment of visual, sleep and cognitive disorders. Endogenous neuroactive steroids including ß-estradiol and pregnenolone sulfate negatively modulate the function of ρ1 GABAA receptors, but their inhibitory mechanisms are not clear. By combining five cryo-EM structures with electrophysiology and molecular dynamics simulations, we characterize binding sites and negative modulation mechanisms of ß-estradiol and pregnenolone sulfate at the human ρ1 GABAA receptor. ß-estradiol binds in a pocket at the interface between extracellular and transmembrane domains, apparently specific to the ρ subfamily, and disturbs allosteric conformational transitions linking GABA binding to pore opening. In contrast, pregnenolone sulfate binds inside the pore to block ion permeation, with a preference for activated structures. These results illuminate contrasting mechanisms of ρ1 inhibition by two different neuroactive steroids, with potential implications for subtype-specific gating and pharmacological design.

Novel neuropharmacological activity of citrus lime (Citrus aurantifolia): A standardized lime peel supplement enhances non-rapid eye movement sleep by activating the GABA type A receptor.

Polyphenols have been well-established to exert sedative-hypnotic effects in psychopharmacology. Lime (Citrus aurantifolia) peel is rich in biologically active polyphenols; however, the effects of lime peel extract on sleep have not yet been demonstrated. A comparison was conducted in mice, between the sleep-promoting effects of a standardized lime peel supplement (SLPS) and a well-known hypnotic drug, zolpidem, and its hypnotic mechanism was investigated using in vivo and in vitro assays. The effects of SLPS on sleep were assessed using a pentobarbital-induced sleep test and sleep architecture analysis based on recording electroencephalograms and electromyograms. Additionally, a GABAA receptor binding assay, electrophysiological measurements, and in vivo animal models were used to elucidate the hypnotic mechanism. SLPS (200 and 400 mg/kg) was found to significantly decrease sleep latency and increase the amount of non-rapid eye movement sleep without altering delta activity. The hypnotic effects of SLPS were attributed to its flavonoid-rich ethyl acetate fraction. SLPS had a binding affinity to the GABA-binding site of the GABAA receptor and directly activated the GABAA receptors. The hypnotic effects and GABAA receptor activity of SLPS were completely blocked by bicuculline, a competitive antagonist of the GABAA receptor, in both in vitro and in vivo assays. To the best of our knowledge, this study is the first to demonstrate the hypnotic effects of SLPS, which acts via the GABA-binding site of the GABAA receptor. Our results suggest that lime peel, a by-product abundantly generated during juice processing, can potentially be used as a novel sedative-hypnotic.

Modular Structure and Polymerization Status of GABAA Receptors Illustrated with EM Analysis and AlphaFold2 Prediction.

Type-A γ-aminobutyric acid (GABAA) receptors are channel proteins crucial to mediating neuronal balance in the central nervous system (CNS). The structure of GABAA receptors allows for multiple binding sites and is key to drug development. Yet the formation mechanism of the receptor's distinctive pentameric structure is still unknown. This study aims to investigate the role of three predominant subunits of the human GABAA receptor in the formation of protein pentamers. Through purifying and refolding the protein fragments of the GABAA receptor α1, ß2, and γ2 subunits, the particle structures were visualised with negative staining electron microscopy (EM). To aid the analysis, AlphaFold2 was used to compare the structures. Results show that α1 and ß2 subunit fragments successfully formed homo-oligomers, particularly homopentameric structures, while the predominant heteropentameric GABAA receptor was also replicated through the combination of the three subunits. However, homopentameric structures were not observed with the γ2 subunit proteins. A comparison of the AlphaFold2 predictions and the previously obtained cryo-EM structures presents new insights into the subunits' modular structure and polymerization status. By performing experimental and computational studies, a deeper understanding of the complex structure of GABAA receptors is provided. Hopefully, this study can pave the way to developing novel therapeutics for neuropsychiatric diseases.

Systemic corticosterone enhances fear memory extinction in rats: Involvement of the infralimbic medial prefrontal cortex GABAA and GABAB receptors.

PURPOSE: The infralimbic (IL) subregion of the medial prefrontal cortex (mPFC) regulates the extinction of conditioned fear memory. Glucocorticoid and gamma-aminobutyric acid (GABA) receptors are expressed in the mPFC and are also critical in fear extinction. This study investigated the possible interactive effects of the glucocorticoids and GABAergic system in the IL on the regulation of fear extinction. METHOD: The rats were trained using an auditory fear conditioning task during which they received three conditioned stimuli (tones, 30 s, 4 kHz, 80 dB), co-terminated with the three unconditioned stimuli (footshock, 0.8 mA, 1 s). Extinction testing was conducted over 3 days (Ext 1-3). Thirty minutes before the first extinction trial (Ext 1), the rats received bicuculline (BIC, 1 mg/kg/2 mL, intraperitoneal [i.p.]) as a GABAA receptor antagonist or CGP55845 (CGP, 0.1 mg/kg/2 ML, i.p.) as a GABAB receptor antagonist followed by systemic injection of corticosterone (CORT, 3 mg/kg/2 ML, i.p.). Furthermore, separate groups of rats received a bilateral intra-IL injection of BIC (100 ng/0.3 µL/side) or CGP (10 ng/0.3 µL/side) followed by a systemic injection of CORT (3 mg/kg/2 ML, i.p.) before the first extinction trial (Ext 1). The extracellular signal-regulated kinase (ERK1) and cAMP response element-binding (CREB) activity in the IL was examined by Western blot analysis after Ext 1. FINDING: The results indicated that systemic CORT injection facilitated fear extinction and increased the expression of ERK1 but not CREB in the IL. Both systemic and intra-IL co-injection of BIC or CGP blocked the effects of CORT on fear extinction and ERK1 expression. CONCLUSION: These findings suggest that glucocorticoids and the GABAergic system may modulate fear extinction through the ERK pathway in the IL.

Deletion of histamine H2 receptor in VTA dopaminergic neurons of mice induces behavior reminiscent of mania.

Hyperfunction of the dopamine system has been implicated in manic episodes in bipolar disorders. How dopaminergic neuronal function is regulated in the pathogenesis of mania remains unclear. Histaminergic neurons project dense efferents into the midbrain dopaminergic nuclei. Here, we present mice lacking dopaminergic histamine H2 receptor (H2R) in the ventral tegmental area (VTA) that exhibit a behavioral phenotype mirroring some of the symptoms of mania, including increased locomotor activity and reduced anxiety- and depression-like behavior. These behavioral deficits can be reversed by the mood stabilizers lithium and valproate. H2R deletion in dopaminergic neurons significantly enhances neuronal activity, concurrent with a decrease in the γ-aminobutyric acid (GABA) type A receptor (GABAAR) membrane presence and inhibitory transmission. Conversely, either overexpression of H2R in VTA dopaminergic neurons or treatment of H2R agonist amthamine within the VTA counteracts amphetamine-induced hyperactivity. Together, our results demonstrate the engagement of H2R in reducing VTA dopaminergic activity, shedding light on the role of H2R as a potential target for mania therapy.

γ-Aminobutyric acid type A receptor ß1 subunit gene polymorphisms are associated with the sedative and amnesic effects of midazolam.

Midazolam is widely used for intravenous sedation. However, wide interindividual variability is seen in the sensitivity to midazolam. The association between genetic factors and interindividual differences in midazolam sensitivity remains unclear. The present study explored the association between common genetic variants and sedative and amnesic effects of midazolam. This prospective study included patients who were scheduled to undergo dental procedures under intravenous sedation. The sedative effect was evaluated using the Ramsay sedation scale 5 min after midazolam (0.05 mg/kg) administration. We employed two parallel approaches in this study: genome-wide approach and candidate gene approach. The γ-aminobutyric acid type A receptor subunit genes were selected as candidate genes. Multivariate linear regression analyses were performed to investigate the association between the Ramsay sedation scale and genetic variants. We also analyzed the association between the presence of anterograde amnesia and genetic variants using multivariate binominal logistic regression analyses. The analyses were adjusted for potential confounding factors. A total of 191 patients were included in the analyses. In the genome-wide association analyses, no significant association was found between the genetic variants and Ramsay scores. In the candidate gene analyses, the rs73247636 (dominant model: ß = 0.72 [95% confidence interval, 0.34 to 1.10], P < 0.001) and rs56278524 (dominant model: ß = 0.73 [0.37 to 1.10], P < 0.001) polymorphisms of the GABRB1 gene were significantly associated with Ramsay scores. Additionally, the rs73247636 (dominant model: odds ratio [OR] = 8.39 [2.36 to 29.85], P = 0.001) and rs56278524 (dominant model: OR = 15.26 [3.42 to 68.07], P < 0.001) polymorphisms were also significantly associated with the presence of anterograde amnesia. The rs73247636 and rs56278524 single-nucleotide polymorphisms of GABRB1 were associated with the sedative and amnesic effects of midazolam.

Shank3 deficiency alters midbrain GABAergic neuron morphology, GABAergic markers and synaptic activity in primary striatal neurons.

Abnormalities in gamma-aminobutyric acid (GABA)ergic neurotransmission play a role in the pathogenesis of autism, although the mechanisms responsible for alterations in specific brain regions remain unclear. Deficits in social motivation and interactions are core symptoms of autism, likely due to defects in dopaminergic neural pathways. Therefore, investigating the morphology and functional roles of GABAergic neurons within dopaminergic projection areas could elucidate the underlying etiology of autism. The aim of this study was to (1) compare the morphology and arborization of glutamate decarboxylase (GAD)-positive neurons from the midbrain tegmentum; (2) evaluate synaptic activity in primary neurons from the striatum; and (3) assess GABAergic postsynaptic puncta in the ventral striatum of wild-type (WT) and Shank3-deficient mice. We found a significant decrease in the number of short neurites in GAD positive primary neurons from the midbrain tegmentum in Shank3-deficient mice. The application of a specific blocker of GABAA receptors (GABAAR) revealed significantly increased frequency of spontaneous postsynaptic currents (sPSCs) in Shank3-deficient striatal neurons compared to their WT counterparts. The mean absolute amplitude of the events was significantly higher in striatal neurons from Shank3-deficient compared to WT mice. We also observed a significant reduction in gephyrin/GABAAR γ2 colocalization in the striatum of adult male Shank3-deficient mice. The gene expression of collybistin was significantly lower in the nucleus accumbens while gephyrin and GABAAR γ2 were lower in the ventral tegmental area (VTA) in male Shank3-deficient compared to WT mice. In conclusion, Shank3 deficiency leads to alterations in GABAergic neurons and impaired GABAergic function in dopaminergic brain areas. These changes may underlie autistic symptoms, and potential interventions modulating GABAergic activity in dopaminergic pathways may represent new treatment modality.

Sedative Effects of Daidzin, Possibly Through the GABAA Receptor Interaction Pathway: In Vivo Approach with Molecular Dynamic Simulations.

The soy isoflavone daidzin (DZN) has been considered a hopeful bioactive compound having diverse biological activities, including anxiolytic, memory-enhancing, and antiepileptic effects, in experimental animals. However, its sedative and hypnotic effects are yet to be discovered. This study aimed to evaluate its sedative/hypnotic effect on Swiss mice. Additionally, in silico studies were also performed to see the possible molecular mechanisms behind the tested neurological effect. For this, male Swiss albino mice were treated with DZN (5, 10, or 20 mg/kg) intraperitoneally (i.p.) with or without the standard GABAergic medication diazepam (DZP) and/or flumazenil (FLU) and checked for the onset and duration of sleeping time using thiopental sodium-induced as well as DZP-induced sleeping tests. A molecular docking study was also performed to check its interaction capacity with the α1 and ß2 subunits of the GABAA receptor. Findings suggest that DZN dose-dependently and significantly reduced the latency while increasing the duration of sleep in animals. In combination therapy, DZN shows synergistic effects with the DZP-2 and DZP-2 + FLU-0.01 groups, resulting in significantly (p < 0.05) reduced latency and increased sleep duration. Further, molecular docking studies demonstrate that DZN has a strong binding affinity of - 7.2 kcal/mol, which is closer to the standard ligand DZP (- 8.3 kcal/mol) against the GABAA (6X3X) receptor. Molecular dynamic simulations indicated stability and similar binding locations for DZP and DZN with 6X3X. In conclusion, DZN shows sedative effects on Swiss mice, possibly through the GABAA receptor interaction pathway.

Flufenamic acid abolishes epileptiform activity in the entorhinal cortex slices by reducing the temporal summation of glutamatergic responses.

Flufenamic acid (FFA) is an anti-inflammatory drug that affects multiple targets and is a widely used research tool in ion channel studies. This pharmacological compound has a low level of selectivity for the transient receptor potential (TRP) channel superfamily, blocking calcium-activated nonselective cation current (ICAN) as well as afterdepolarizations (ADP) induced by it. A number of studies have demonstrated that FFA exerts an anti-epileptic effect in vitro, although the precise mechanism of this effect is not yet identified. The present study used whole-cell patch-clamp recordings and demonstrated that FFA (25 µM) can abolish the generation of seizure-like events (SLE) in entorhinal cortex slices perfused with a 4-aminopyridine-containing solution, depending on the time of application. FFA decreased the temporal summation of synaptic potentials at the onset of SLEs. However, as the epileptiform activity evolved and the SLE onset phase became more abrupt, the blocking effect of FFA diminished. FFA effectively abolished TRP channel-mediated slow ADPs, exerted a weak blockade and slowed the kinetics of GABAa receptor-mediated currents, and did not affect NMDA receptor-mediated evoked currents induced by extracellular stimulation. Although FFA did not directly inhibit NMDA receptor-mediated evoked currents, it decreased the summation of NMDA receptor-mediated potentials in a manner comparable to its effect on the initiation phase of SLE. This suggests that ICAN blockade may be responsible for this effect. Furthermore, our results showed that the selective blocker of melastatin TRP channels (TRPM4) 9-phenanthrol effectively abolished epileptiform activity in a manner analogous to FFA. In contrast, ML-204, the blocker of canonical TRP channels (TRPC), had no discernible effect on this phenomenon. In conclusion, the study demonstrate that FFA abolishes epileptiform activity in the entorhinal cortex by blocking TRPM4 channels and, consequently, decreasing the effectiveness of temporal summation of glutamatergic potentials.

GAD65 tunes the functions of Best1 as a GABA receptor and a neurotransmitter conducting channel.

Bestrophin-1 (Best1) is an anion channel genetically linked to vision-threatening retinal degenerative channelopathies. Here, we identify interactions between Best1 and both isoforms of glutamic acid decarboxylases (GAD65 and GAD67), elucidate the distinctive influences of GAD65 and GAD67 on Best1's permeability to various anions/neurotransmitters, discover the functionality of Best1 as a γ-Aminobutyric acid (GABA) type A receptor, and solve the structure of GABA-bound Best1. GAD65 and GAD67 both promote Best1-mediated Cl- currents, but only GAD65 drastically enhances the permeability of Best1 to glutamate and GABA, for which GAD67 has no effect. GABA binds to Best1 on an extracellular site and stimulates Best1-mediated Cl- currents at the nano-molar concentration level. The physiological role of GAD65 as a cell type-specific binding partner and facilitator of Best1 is demonstrated in retinal pigment epithelial cells. Together, our results reveal critical regulators of Best1 and inform a network of membrane transport metabolons formed between bestrophin channels and glutamate metabolic enzymes.

Functional Neuroligin-2-MDGA1 interactions differentially regulate synaptic GABAARs and cytosolic gephyrin aggregation.

Neuroligin-2 (Nlgn2) is a key synaptic adhesion protein at virtually all GABAergic synapses, which recruits GABAARs by promoting assembly of the postsynaptic gephyrin scaffold. Intriguingly, loss of Nlgn2 differentially affects subsets of GABAergic synapses, indicating that synapse-specific interactors and redundancies define its function, but the nature of these interactions remain poorly understood. Here we investigated how Nlgn2 function in hippocampal area CA1 is modulated by two proposed interaction partners, MDGA1 and MDGA2. We show that loss of MDGA1 expression, but not heterozygous deletion of MDGA2, ameliorates the abnormal cytosolic gephyrin aggregation, the reduction in inhibitory synaptic transmission and the exacerbated anxiety-related behaviour characterizing Nlgn2 knockout (KO) mice. Additionally, combined Nlgn2 and MDGA1 deletion causes an exacerbated layer-specific loss of gephyrin puncta. Given that both Nlgn2 and the MDGA1 have been correlated with many psychiatric disorders, our data support the notion that cytosolic gephyrin aggregation may represent an interesting target for novel therapeutic strategies.

Alterations in GABAA receptor-mediated inhibition triggered by status epilepticus and their role in epileptogenesis and increased anxiety.

The triggers of status epilepticus (SE) in non-epileptic patients can vary widely, from idiopathic causes to exposure to chemoconvulsants. Regardless of its etiology, prolonged SE can cause significant brain damage, commonly resulting in the development of epilepsy, which is often accompanied by increased anxiety. GABAA receptor (GABAAR)-mediated inhibition has a central role among the mechanisms underlying brain damage and the ensuing epilepsy and anxiety. During SE, calcium influx primarily via ionotropic glutamate receptors activates signaling cascades which trigger a rapid internalization of synaptic GABAARs; this weakens inhibition, exacerbating seizures and excitotoxicity. GABAergic interneurons are more susceptible to excitotoxic death than principal neurons. During the latent period of epileptogenesis, the aberrant reorganization in synaptic interactions that follow interneuronal loss in injured brain regions, leads to the formation of hyperexcitable, seizurogenic neuronal circuits, along with disturbances in brain oscillatory rhythms. Reduction in the spontaneous, rhythmic "bursts" of IPSCs in basolateral amygdala neurons is likely to play a central role in anxiogenesis. Protecting interneurons during SE is key to preventing both epilepsy and anxiety. Antiglutamatergic treatments, including antagonism of calcium-permeable AMPA receptors, can be expected to control seizures and reduce excitotoxicity not only by directly suppressing hyperexcitation, but also by counteracting the internalization of synaptic GABAARs. Benzodiazepines, as delayed treatment of SE, have low efficacy due to the reduction and dispersion of their targets (the synaptic GABAARs), but also because themselves contribute to further reduction of available GABAARs at the synapse; furthermore, benzodiazepines may be completely ineffective in the immature brain.

Coronaridine congeners induce anticonvulsant activity in rodents by hippocampal mechanisms involving mainly potentiation of GABAA receptors.

The coronaridine congeners catharanthine and 18-methoxycoronaridine (18-MC) display sedative, anxiolytic, and antidepressant properties by acting on mechanisms involving GABAergic and/or monoaminergic transmissions. Here, we expanded their pharmacological properties by studying their anticonvulsant activity in male and female mice using the pentylenetetrazole (PTZ)-induced seizure test. To determine potential neurochemical mechanisms, the effect of congeners on monoamine content and kainic acid (KA)-induced epileptiform discharge was studied in the hippocampus. The behavioral results showed that coronaridine congeners induce acute anticonvulsant activity in a dose-dependent but sex-independent manner. Repeated treatment with a subthreshold dose (20 mg/kg) of each congener produced anticonvulsant activity in a sex-independent manner, but was significantly higher in male mice when compared to its acute effect. Using a behaviourally relevant regimen, we found that PTZ increased dopamine metabolites and serotonin tissue content. Coronaridine congeners, which induced distinct effects on monoamines, blunted the effect of PTZ instead of potentiating it, suggesting the existence of another mechanism in their anticonvulsant activity. The electrophysiological results indicated that both congeners inhibit KA-induced epileptiform discharges in hippocampal slices. A key aspect of this study is that the activity of both congeners was observed only in the presence of GABA, supporting the notion that hippocampal GABAAR potentiation plays an important role. Our study showed that coronaridine congeners induce acute anticonvulsant activity in a sex-independent manner. However, a comparatively higher susceptibility was observed in male mice after repeated treatment. The underlying hippocampal mechanisms mainly involve GABAAR potentiation, whereas monoamines play a minor role in the anticonvulsive action.

The emergence of antidepressant drugs targeting GABAA receptors: A concise review.

Depression is among the most common psychiatric illnesses, which imposes a major socioeconomic burden on patients, caregivers, and the public health system. Treatment with classical antidepressants (e.g. tricyclic antidepressants and selective serotonine reuptake inhibitors), which primarily affect monoaminergic systems has several limitations, such as delayed onset of action and moderate efficacy in a relatively large proportion of depressed patients. Furthermore, depression is highly heterogeneus, and its different subtypes, including post-partum depression, involve distinct neurobiology, warranting a differential approach to pharmacotherapy. Given these shortcomings, the need for novel antidepressants that are superior in efficacy and faster in onset of action is fully justified. The development and market introduction of rapid-acting antidepressants has accelerated in recent years. Some of these new antidepressants act through the GABAergic system. In this review, we discuss the discovery, efficacy, and limitations of treatment with classic antidepressants. We provide a detailed discussion of GABAergic neurotransmission, with a special focus on GABAA receptors, and possible explanations for the mood-enhancing effects of GABAergic medications (in particular neurosteroids acting at GABAA receptors), and, ultimately, we present the most promising molecules belonging to this family which are currently used in clinical practice or are in late phases of clinical development.

GABRG2 mutations in genetic epilepsy with febrile seizures plus: structure, roles, and molecular genetics.

Genetic epilepsy with febrile seizures plus (GEFS+) is a genetic epilepsy syndrome characterized by a marked hereditary tendency inherited as an autosomal dominant trait. Patients with GEFS+ may develop typical febrile seizures (FS), while generalized tonic-clonic seizures (GTCSs) with fever commonly occur between 3 months and 6 years of age, which is generally followed by febrile seizure plus (FS+), with or without absence seizures, focal seizures, or GTCSs. GEFS+ exhibits significant genetic heterogeneity, with polymerase chain reaction, exon sequencing, and single nucleotide polymorphism analyses all showing that the occurrence of GEFS+ is mainly related to mutations in the gamma-aminobutyric acid type A receptor gamma 2 subunit (GABRG2) gene. The most common mutations in GABRG2 are separated in large autosomal dominant families, but their pathogenesis remains unclear. The predominant types of GABRG2 mutations include missense (c.983A → T, c.245G → A, p.Met199Val), nonsense (R136*, Q390*, W429*), frameshift (c.1329delC, p.Val462fs*33, p.Pro59fs*12), point (P83S), and splice site (IVS6+2T → G) mutations. All of these mutations types can reduce the function of ion channels on the cell membrane; however, the degree and mechanism underlying these dysfunctions are different and could be linked to the main mechanism of epilepsy. The γ2 subunit plays a special role in receptor trafficking and is closely related to its structural specificity. This review focused on investigating the relationship between GEFS+ and GABRG2 mutation types in recent years, discussing novel aspects deemed to be great significance for clinically accurate diagnosis, anti-epileptic treatment strategies, and new drug development.

γ1 GABAA Receptors in Spinal Nociceptive Circuits.

GABAergic neurons and GABAA receptors (GABAARs) are critical elements of almost all neuronal circuits. Most GABAARs of the CNS are heteropentameric ion channels composed of two α, two ß, and one γ subunits. These receptors serve as important drug targets for benzodiazepine (BDZ) site agonists, which potentiate the action of GABA at GABAARs. Most GABAAR classifications rely on the heterogeneity of the α subunit (α1-α6) included in the receptor complex. Heterogeneity of the γ subunits (γ1-γ3), which mediate synaptic clustering of GABAARs and contribute, together with α subunits, to the benzodiazepine (BDZ) binding site, has gained less attention, mainly because γ2 subunits greatly outnumber the other γ subunits in most brain regions. Here, we have investigated a potential role of non-γ2 GABAARs in neural circuits of the spinal dorsal horn, a key site of nociceptive processing. Female and male mice were studied. We demonstrate that besides γ2 subunits, γ1 subunits are significantly expressed in the spinal dorsal horn, especially in its superficial layers. Unlike global γ2 subunit deletion, which is lethal, spinal cord-specific loss of γ2 subunits was well tolerated. GABAAR clustering in the superficial dorsal horn remained largely unaffected and antihyperalgesic actions of HZ-166, a nonsedative BDZ site agonist, were partially retained. Our results thus suggest that the superficial dorsal horn harbors functionally relevant amounts of γ1 subunits that support the synaptic clustering of GABAARs in this site. They further suggest that γ1 containing GABAARs contribute to the spinal control of nociceptive information flow.

An alpha 5-GABAA receptor positive allosteric modulator attenuates social and cognitive deficits without changing dopamine system hyperactivity in rats exposed to valproic acid in utero.

Autism spectrum disorders (ASDs) are characterized by core behavioral symptoms in the domains of sociability, language/communication, and repetitive or stereotyped behaviors. Deficits in the prefrontal and hippocampal excitatory/inhibitory balance due to a functional loss of GABAergic interneurons are proposed to underlie these symptoms. Increasing the postsynaptic effects of GABA with compounds that selectively modulate GABAergic receptors could be a potential target for treating ASD symptoms. In addition, deficits in GABAergic interneurons have been linked to dopamine (DA) system dysregulation, and, despite conflicting evidence, abnormalities in the DA system activity may underly some ASD symptoms. Here, we investigated whether the positive allosteric modulator of α5-containing GABAA receptors (α5-GABAARs) SH-053-2'F-R-CH3 (10 mg/kg) attenuates behavioral abnormalities in rats exposed to valproic acid (VPA) in utero, an established risk factor for autism. We also evaluated if animals exposed to VPA in utero present changes in the ventral tegmental area (VTA) DA system activity using in vivo electrophysiology and if SH-053-2'F-R-CH3 could attenuate these changes. SH-053-2'F-R-CH3 was administered intraperitoneally 30 min before each behavioral test and electrophysiology. In utero VPA exposure caused male and female rats to present increased repetitive behavior (self-grooming) in early adolescence and deficits in social interaction in adulthood. Male, but not female VPA rats, also presented deficits in recognition memory as adults. SH-053-2'F-R-CH3 attenuated the impairments in sociability and cognitive function in male VPA-exposed rats without attenuating the decreased social interaction in females. Adult male and female VPA-exposed rats also showed an increased VTA DA neuron population activity, which was not changed by SH-053-2'F-R-CH3. Despite sex differences, our findings indicate that α5-GABAARs positive allosteric modulators may effectively attenuate some core ASD symptoms.