Search Results (64)

Medulloblastoma (MB) is the most common malignant brain tumor in children and typically arises in the cerebellum, likely due to disruptions in neuronal precursor development. The primary inhibitory neurotransmitter in the central nervous system (CNS), γ-aminobutyric acid (GABA), exerts its effects through GABA_A, GABA_B, and GABA_C receptors. GABA receptor activity regulates the development and function of cerebellar neurons, including glutamatergic cerebellar granule cells (CGCs). Beyond the nervous system, GABA is also a common metabolite in non-neuronal cell types. An increasing body of evidence indicates that GABA can influence cell proliferation, differentiation, and migration in several types of adult solid tumors, including brain cancers. GABA and GABA_A receptor agonists can impair the viability and survival of MB cells, primarily acting on GABA_A receptors containing the α5 subunit. A marked expression of the gene encoding the α5 subunit is found across all MB tumor molecular subgroups, particularly Group 3 MB, which has a poor prognosis. Importantly, high levels of the γ-aminobutyric acid type A receptor subunit α5 (GABRA5) gene are associated with shorter patient overall survival in Group 3 and Group 4 MB. In contrast, high γ-aminobutyric acid type A receptor subunit β1 (GABRB1) gene expression is related to longer survival in all MB subgroups. The GABAergic system may, therefore, regulate MB cell function and tumor progression and influence patient prognosis, and is worthy of further investigation as a biomarker and therapeutic target in MB. Full article

The ionotropic γ-aminobutyric acid (GABA) receptor (GABAR) is a key target for the development of antiparasitic agents, particularly against ectoparasites, such as fleas and ticks. Binding stability and selectivity of sarolaner enantiomers for Ctenocephalides felis RDL receptors (RDLR) were investigated in the current study. Wild-type (WT) C. felis RDLR and its A285S mutant were constructed using homology-based, fragment-based threading and AI-driven approaches, of which, SWISS-MODEL generated the most reliable structures. Molecular docking showed that the sarolaner S-enantiomer had higher binding affinity for both receptors than the R-enantiomer, primarily due to hydrogen bonding with Ile256, π–π stacking with Phe326, and hydrophobic interactions with Ile267 and Ile268. Molecular dynamics simulations confirmed the binding stability of the S-enantiomer-receptor complex in which key residues maintained interactions throughout the trajectories. Binding free energy analysis supported these results and highlighted the role of nonpolar interactions in binding stability. The A285S mutation had minimal impact on the binding pocket, and the S-enantiomer remained selective for and bound to the mutant receptor. Insights into the insecticidal mechanism of sarolaner enantiomers are given, and the current findings may inform the development of veterinary drugs from novel isoxazoline-based NAMs targeting insect GABARs. Full article

Zuranolone (SAGE-217), the first FDA-approved oral neurosteroid (NAS), a positive allosteric modulator (PAM) of γ-aminobutyric acid type A (GABA_A) receptor for postpartum depression approved in 2023, has limitations such as short half-life, low bioavailability, and central inhibitory side effects. To address these, we designed novel C-21 modified derivatives of Zuranolone, identifying the triazolone scaffold as key for enhancing GABA_A activity. Here, we synthesized Zuranolone analogs with diverse triazolone substituents, finding that pyridine-derived modifications improved the activity correlated with LogP. The optimal derivative, S9 (2-(trifluoroethoxy)pyridine-triazolone, LogP 4.61), showed 2.5-fold greater potency (EC₅₀) and efficacy (Emax) than Zuranolone (LogP 4.78) at synaptic/extrasynaptic GABA_A receptors, attributed to stronger binding via molecular docking. In rats, S9 exhibited 5-fold longer plasma T_1/2, 6-fold higher AUC, 3-fold greater brain exposure, and 30% improved bioavailability. It also outperformed Zuranolone in pentylenetetrazole (PTZ)-induced seizure suppression and threshold dose for loss of righting reflex (LORR) in rats. The C21-pyridine-triazolone pharmacophore in S9 enhances receptor activity potency without increasing lipophilicity, optimizing pharmacokinetics and safety, which makes it a promising therapeutic candidate for depression and epilepsy. Full article

Cenobamate is a new and highly effective antiseizure compound used for the treatment of adults with focal onset seizures and particularly for epilepsy resistant to other antiepileptic drugs. It acts on multiple targets, as it is a positive allosteric activator of γ-aminobutyric acid type A (GABA_A) receptors and an inhibitor of neuronal sodium channels, particularly of the late or persistent Na⁺ current. We recently evidenced the inhibitory effects of cenobamate on the peak and late current component of the human cardiac isoform hNav1.5. The determined apparent IC₅₀ values of 87.6 µM (peak) and 46.5 µM (late current) are within a clinically relevant range of concentrations (the maximal plasma therapeutic effective concentration for a daily dose of 400 mg in humans is 170 µM). In this study, we built a 3D model of the canonical hNav1.5 channel (UniProt Q14524-1) in open conformation using AlphaFold2, embedded it in a DPPC lipid bilayer, corrected the residue protonation state (pH 7.2) with H++, and added 2 Na⁺ ions in the selectivity filter. By molecular docking, we found the cenobamate binding site in the central cavity. We identified 10-point mutant variants in the binding site region and explored them via docking and MD. Mutants N1462K/Y (rs1064795922, rs199473614) and M1765R (rs752476527) (by docking) and N932S (rs2061582195) (by MD) featured higher predicted affinity than wild-type. Full article

Background/Objectives: Most of the rapid inhibitory neurotransmission in the brain is mediated through activation of the γ-aminobutyric acid (GABA) type A (GABA_A) receptor, which is a ligand-gated ion channel. GABA_A receptor activation via GABA binding allows for an intracellular influx of Cl⁻ ions, thus inducing cellular hyperpolarization. Each GABA_A receptor consists of a combination of five subunits, and several subunits have been proposed as biomarkers and therapeutic targets in cancer. Here, we show the expression of genes encoding β subunits of the GABA_A receptor, namely GABRB1, GABRB2, and GABRB3, across the four different molecular subgroups of medulloblastoma (MB), which is the most common malignant pediatric brain tumor. We also show the associations of GABA_A receptor β subunits with MB patients’ overall survival (OS). Methods: The expression of genes encoding GABA_A receptor β subunits was analyzed using a previously described dataset comprising 763 MB tumor samples. Patients were classified into high- and low-gene-expression groups, and the Kaplan–Meier estimate was used to examine the relationship between gene expression levels and patient OS. Results: High GABRB1 expression was associated with better OS within each of the four molecular subgroups. The GABRB2 gene showed higher transcript levels in Group 3 MB compared to all other subgroups, and high expression was associated with better prognosis in Group 3 tumors. GABRB3 expression was significantly higher in Group 3 and Group 4 MB, and high expression of GABRB3 genes was associated with longer OS in the sonic hedgehog (SHH) subgroup. The high expression of GABRB1, GABRB2, and GABRB3 is associated with longer patient OS in a subgroup-specific manner. Conclusions: These results indicate a role for GABA_A receptors containing β subunits in influencing MB progression. Full article

Type-A γ-aminobutyric acid (GABA_A) receptors are channel proteins crucial to mediating neuronal balance in the central nervous system (CNS). The structure of GABA_A 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 GABA_A receptor in the formation of protein pentamers. Through purifying and refolding the protein fragments of the GABA_A receptor α1, β2, 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 β2 subunit fragments successfully formed homo-oligomers, particularly homopentameric structures, while the predominant heteropentameric GABA_A 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 GABA_A receptors is provided. Hopefully, this study can pave the way to developing novel therapeutics for neuropsychiatric diseases. Full article

German chamomile (Matricaria chamomilla L.) is an essential oil- containing medicinal plant used worldwide. The aim of this study was to gain knowledge of the phytochemical composition and the analgesic and soporific activity of Matricaria chamomilla L. (German chamomile) flower extract and its amino acid preparations, to predict the mechanisms of their effects by molecular docking and to develop aqueous printing gels and novel 3D-printed oral dosage forms for the flower extracts. In total, 22 polyphenolic compounds and 14 amino acids were identified and quantified in the M. chamomilla extracts. In vivo animal studies with rodents showed that the oral administration of such extracts revealed the potential for treating of sleep disorders and diseases accompanied by pain. Amino acids were found to potentiate these effects. Glycine enhanced the analgesic activity the most, while lysine and β-alanine improved the soporific activity. The molecular docking analysis revealed a high probability of γ-aminobutyric acid type A (GABAA) and N-methyl-D-aspartate (NMDA) receptor antagonism and 5-lipoxygenase (LOX-5) inhibition by the extracts. A polyethylene oxide (PEO)-based gel composition with the M. chamomilla extracts was proposed for preparing a novel 3D-printed dosage form for oral administration. These 3D-printed extract preparations can be used, for example, in dietary supplement applications. Full article

The exploration of heterocyclic compounds and their fused analogs, featuring key pharmacophore fragments like pyridine, thiophene, pyrimidine, and triazine rings, is pivotal in medicinal chemistry. These compounds possess a wide array of biological activities, making them an intriguing area of study. The quest for new neurotropic drugs among derivatives of these heterocycles with pharmacophore groups remains a significant research challenge. The aim of this research work was to develop a synthesis method for new heterocyclic compounds, evaluate their neurotropic and neuroprotective activities, study histological changes, and perform docking analysis. Classical organic synthesis methods were used in the creation of novel heterocyclic systems containing pharmacophore rings. To evaluate the neurotropic activity of these synthesized compounds, a range of biological assays were employed. Docking analysis was conducted using various software packages and methodologies. The neuroprotective activity of compound 13 was tested in seizures with and without pentylenetetrazole (PTZ) administration. Histopathological examinations were performed in different experimental groups in the hippocampus and the entorhinal cortex. As a result of chemical reactions, 16 new, tetra- and pentacyclic heterocyclic compounds were obtained. The biologically studied compounds exhibited protection against PTZ seizures as well as some psychotropic effects. The biological assays evidenced that 13 of the 16 studied compounds showed a high anticonvulsant activity by antagonism with PTZ. The toxicity of the compounds was low. According to the results of the study of psychotropic activity, it was found that the selected compounds have a sedative effect, except compound 13, which exhibited activating behavior and antianxiety effects (especially compound 13). The studied compounds exhibited antidepressant effects, especially compound 13, which is similar to diazepam. Histopathological examination showed that compound 13 produced moderate changes in the brain and exhibited neuroprotective effects in the entorhinal cortex against PTZ-induced damage, reducing gliosis and neuronal loss. Docking studies revealed that out of 16 compounds, 3 compounds bound to the γ-aminobutyric acid type A (GABA_A) receptor. Thus, the selected compounds demonstrated anticonvulsant, sedative, and activating behavior, and at the same time exhibited antianxiety and antidepressant effects. Compound 13 bound to the GABA_A receptor and exhibited antianxiety, antidepressant, and neuroprotective effects in the entorhinal cortex against PTZ-induced changes. Full article

Rapid neuronal inhibition in the brain is mediated by γ-aminobutyric acid (GABA) activation of GABA_A receptors. The GABRA5 gene, which encodes the α5 subunit of the GABA_A receptor, has been implicated in an aggressive subgroup of medulloblastoma (MB), a type of pediatric brain tumor. However, the possible role of GABA_A receptor subunits in glioma remains poorly understood. Here, we examined the expression of genes encoding GABA_A receptor subunits in different types of glioma, and its possible association with patient prognosis assessed by overall survival (OS). Data were obtained from the French and The Cancer Genome Atlas Brain Lower Grade Glioma (TCGA-LGG) datasets and analyzed for expression of GABA_A receptor subunit genes. OS was calculated using the Kaplan–Meier estimate. We found that genes GABRA2, GABRA3, GABRB3, GABRG1, and GABRG2 showed a significant association with OS, with higher gene expression indicating better prognosis. In patients with GBM, high expression of GABRA2 was associated with shorter OS, whereas, in contrast, higher levels of GABRB3 were associated with better prognosis indicated by longer OS. In patients with lower grade gliomas, GABRA3, GABRB3, GABRG1, and GABRG2, were associated with longer OS. High GABRB3 expression was related to longer survival when low grade glioma types were analyzed separately. Our results suggest an overall association between higher expression of most genes encoding GABA_A receptor subunits and better prognosis in different types of glioma. Our findings support the possibility that down-regulation of GABA_A receptors in glioma contributes to promoting tumor progression by reducing negative inhibition. These findings might contribute to further evaluation of GABA_A receptors as a therapeutic target in glioma. Full article

Ischemic stroke is a devastating disease leading to neurologic impairment. Compounding the issue is the very limited array of available interventions. The activation of a γ-aminobutyric acid (GABA) type A receptor (GABA_AR) has been reported to produce neuroprotective properties during cerebral ischemia, but its mechanism of action is not yet fully understood. Here, in a rat model of photochemically induced cerebral ischemia, we found that muscimol, a GABA_AR agonist, modulated GABAergic signaling, ameliorated anxiety-like behaviors, and attenuated neuronal damage in rats suffering cerebral ischemia. Moreover, GABA_AR activation improved brain antioxidant levels, reducing the accumulation of oxidative products, which was closely associated with the NO/NOS pathway. Notably, the inhibition of autophagy markedly relieved the neuronal insult caused by cerebral ischemia. We further established an oxygen–glucose deprivation (OGD)-induced PC12 cell injury model. Both in vivo and in vitro experiments demonstrated that GABA_AR activation obviously suppressed autophagy by regulating the AMPK-mTOR pathway. Additionally, GABA_AR activation inhibited apoptosis through inhibiting the Bax/Bcl-2 pathway. These data suggest that GABA_AR activation exerts neuroprotective effects during cerebral ischemia through improving oxidative stress and inhibiting autophagy and apoptosis. Our findings indicate that GABA_AR serves as a target for treating cerebral ischemia and highlight the GABA_AR-mediated autophagy signaling pathway. Full article

Flumazenil is an allosteric modulator of the γ-aminobutyric acid-A receptor (GABA_AR) benzodiazepine binding site that could normalize neuronal signaling and improve motor impairments in Parkinson’s disease (PD). Little is known about how regional GABA_AR availability affects motor symptoms. We investigated the relationship between regional availability of GABA_AR benzodiazepine binding sites and motor impairments in PD. Methods: A total of 11 Patients with PD (males; mean age 69.0 ± 4.6 years; Hoehn and Yahr stages 2–3) underwent [¹¹C]flumazenil GABA_AR benzodiazepine binding site and [¹¹C]dihydrotetrabenazine vesicular monoamine transporter type-2 (VMAT2) PET imaging and clinical assessment. Stepwise regression analysis was used to predict regional cerebral correlates of the four cardinal UPDRS motor scores using cortical, striatal, thalamic, and cerebellar flumazenil binding estimates. Thalamic GABA_AR availability was selectively associated with axial motor scores (R² = 0.55, F = 11.0, β = −6.4, p = 0.0009). Multi-ligand analysis demonstrated significant axial motor predictor effects by both thalamic GABA_AR availability (R² = 0.47, β = −5.2, F = 7.2, p = 0.028) and striatal VMAT2 binding (R² = 0.30, β = −3.9, F = 9.1, p = 0.019; total model: R² = 0.77, F = 11.9, p = 0.0056). Post hoc analysis demonstrated that thalamic [¹¹C]methyl-4-piperidinyl propionate cholinesterase PET and K₁ flow delivery findings were not significant confounders. Findings suggest that reduced thalamic GABA_AR availability correlates with worsened axial motor impairments in PD, independent of nigrostriatal degeneration. These findings may augur novel non-dopaminergic approaches to treating axial motor impairments in PD. Full article

Treatment-resistant depression (TRD) is a term used to describe a particular type of major depressive disorder (MDD). There is no consensus about what defines TRD, with various studies describing between 1 and 4 failures of antidepressant therapies, with or without electroconvulsive therapy (ECT). That is why TRD is such a growing concern among clinicians and researchers, and it explains the necessity for investigating novel therapeutic targets beyond conventional monoamine pathways. An imbalance between two primary central nervous system (CNS) neurotransmitters, L-glutamate and γ-aminobutyric acid (GABA), has emerged as having a key role in the pathophysiology of TRD. In this review, we provide an evaluation and comprehensive review of investigational antidepressants targeting these two systems, accessing their levels of available evidence, mechanisms of action, and safety profiles. N-methyl-D-aspartate (NMDA) receptor antagonism has shown the most promise amongst the glutamatergic targets, with ketamine and esketamine (Spravato) robustly generating responses across trials. Two specific NMDA-glycine site modulators, D-cycloserine (DCS) and apimostinel, have also generated promising initial safety and efficacy profiles, warranting further investigation. Combination dextromethorphan-bupropion (AXS-05/Auvelity) displays a unique mechanism of action and demonstrated positive results in particular applicability in subpopulations with cognitive dysfunction. Currently, the most promising GABA modulators appear to be synthetic neurosteroid analogs with positive GABA_A receptor modulation (such as brexanolone). Overall, advances in the last decade provide exciting perspectives for those who do not improve with conventional therapies. Of the compounds reviewed here, three are approved by the Food and Drug Administration (FDA): esketamine (Spravato) for TRD, Auvelity (dextromethorphan-bupropion) for major depressive disorder (MDD), and brexanolone (Zulresso) for post-partum depression (PPD). Notably, some concerns have arisen with esketamine and brexanolone, which will be detailed in this study. Full article

Epilepsy is a multifactorial neurologic disease that often leads to many devastating disabilities and an enormous burden on the healthcare system. Until now, drug-resistant epilepsy has presented a major challenge for approximately 30% of the epileptic population. The present article summarizes the validated rodent models of seizures employed in pharmacological researches and comprehensively reviews updated advances of novel antiseizure candidates in the preclinical phase. Newly discovered compounds that demonstrate antiseizure efficacy in preclinical trials will be discussed in the review. It is inspiring that several candidates exert promising antiseizure activities in drug-resistant seizure models. The representative compounds consist of derivatives of hybrid compounds that integrate multiple approved antiseizure medications, novel positive allosteric modulators targeting subtype-selective γ-Aminobutyric acid type A receptors, and a derivative of cinnamamide. Although the precise molecular mechanism, pharmacokinetic properties, and safety are not yet fully clear in every novel antiseizure candidate, the adapted approaches to design novel antiseizure medications provide new insights to overcome drug-resistant epilepsy. Full article

Although Ziziphus jujuba Mill (jujube) is used in folk medicine for hypnotic sedative, anxiolytic, and many other purposes, to date, only a few studies have revealed its sleep-promoting effects and related mechanisms. Currently, drugs used for the treatment of sleep disorders have various side effects, so it is essential to develop safe natural materials. Therefore, we evaluated the sleep-enhancing activity and mechanism of action of an aqueous extract of jujube seeds (ZW) fermented with Lactobacillus brevis L-32 in rodent models. The starch contained in ZW was removed by enzymatic degradation and fermented with L. brevis to obtain a fermented product (ZW-FM) with a high γ-aminobutyric acid (GABA) content. To evaluate the sleep-promoting effect of ZW-FM, pentobarbital-induced sleep tests were performed on ICR mice, and electroencephalography analysis was undertaken in Sprague Dawley rats. Additionally, the awakening relief effects of ZW-FM were confirmed in a caffeine-induced insomnia model. Finally, the mechanism of sleep enhancement by ZW-FM was analyzed using GABA receptor type A (GABA_A) antagonists. The ZW-FM-treated groups (100 and 150 mg/kg) showed increased sleep time, especially the δ-wave time during non-rapid eye movement (NREM) sleep. In addition, the 150 mg/kg ZW-FM treatment group showed decreased sleep latency and increased sleep time in the insomnia model. In particular, NREM sleep time was increased and REM sleep time, which was increased by caffeine treatment, was decreased by ZW-FM treatment. ZW-FM-induced sleep increase was inhibited by the GABA_A receptor antagonists picrotoxin, bicuculline, and flumazenil, confirming that the increase was the result of a GABAergic mechanism. These results strongly suggest that the increased GABA in water extract from jujube seeds fermented by L. brevis acts as a sleep-promoting compound and that the sleep-promoting activity is related to GABA_A receptor binding. Full article

Studies of the neurobiological causes of anxiety disorders have suggested that the γ-aminobutyric acid (GABA) system increases synaptic concentrations and enhances the affinity of GABA_A (type A) receptors for benzodiazepine ligands. Flumazenil antagonizes the benzodiazepine-binding site of the GABA/benzodiazepine receptor (BZR) complex in the central nervous system (CNS). The investigation of flumazenil metabolites using liquid chromatography (LC)-tandem mass spectrometry will provide a complete understanding of the in vivo metabolism of flumazenil and accelerate radiopharmaceutical inspection and registration. The main goal of this study was to investigate the use of reversed-phase high performance liquid chromatography (PR-HPLC), coupled with electrospray ionization triple-quadrupole tandem mass spectrometry (ESI-QqQ MS), to identify flumazenil and its metabolites in the hepatic matrix. Carrier-free nucleophilic fluorination with an automatic synthesizer for [¹⁸F]flumazenil, combined with nano-positron emission tomography (NanoPET)/computed tomography (CT) imaging, was used to predict the biodistribution in normal rats. The study showed that 50% of the flumazenil was biotransformed by the rat liver homogenate in 60 min, whereas one metabolite (M1) was a methyl transesterification product of flumazenil. In the rat liver microsomal system, two metabolites were identified (M2 and M3), as their carboxylic acid and hydroxylated ethyl ester forms between 10 and 120 min, respectively. A total of 10–30 min post-injection of [¹⁸F]flumazenil showed an immediate decreased in the distribution ratio observed in the plasma. Nevertheless, a higher ratio of the complete [¹⁸F]flumazenil compound could be used for subsequent animal studies. [¹⁸F] According to in vivo nanoPET/CT imaging and ex vivo biodistribution assays, flumazenil also showed significant effects on GABA_A receptor availability in the amygdala, prefrontal cortex, cortex, and hippocampus in the rat brain, indicating the formation of metabolites. We reported the completion of the biotransformation of flumazenil by the hepatic system, as well as [¹⁸F]flumazenil’s potential as an ideal ligand and PET agent for the determination of the GABA_A/BZR complex for multiplex neurological syndromes at the clinical stage. Full article