Gamma-aminobutyric Acid Receptor Research Articles

Early central cardiovagal dysfunction after high fat diet in a murine model

High fat diet (HFD) promotes cardiovascular disease and blunted cardiac vagal regulation. Temporal onset of loss of cardiac vagal control and its underlying mechanism are presently unclear. We tested our hypothesis that reduced central vagal regulation occurs early after HFD and contributes to poor cardiac regulation using cardiovascular testing paired with pharmacology in mice, molecular biology, and a novel bi-transgenic mouse line. Results show HFD, compared to normal fat diet (NFD), significantly blunted cardio/pulmonary chemoreflex bradycardic responses after 15 days, extending as far as tested (> 30 days). HFD produced resting tachycardia by day 3, reflected significant loss of parasympathetic tone. No differences in bradycardic responses to graded electrical stimulation of the distal cut end of the cervical vagus indicated diet-induced differences in vagal activity were centrally mediated. In nucleus ambiguus (NA), surface expression of δ-subunit containing type A gamma-aminobutyric acid receptors (GABAA(δ)R) increased at day 15 of HFD. Novel mice lacking δ-subunit expression in vagal motor neurons (ChAT-δnull) failed to exhibit blunted reflex bradycardia or resting tachycardia after two weeks of HFD. Thus, reduced parasympathetic output contributes to early HFD-induced HR dysregulation, likely through increased GABAA(δ)Rs. Results underscore need for research on mechanisms of early onset increases in GABAA(δ)R expression and parasympathetic dysfunction after HFD.

Acid treated montmorillonite - efficient catalyst in Prins reaction of alpha-methylstyrene with paraldehyde

Acid treated montmorillonite was used as a catalyst in Prins reaction of α methylstyrene with paraldehyde giving 2,4,6-trimethyl-4-phenyl-1,3-dioxane (Vertacetal). The product of this reaction is a bioactive compound, which can interact with GABA (gamma-aminobutyric acid) receptors and has fragrant properties. Montmorillonite (used for this reaction as catalyst) was prepared by treatment with hydrochloric, nitric, sulfuric or chloroacetic acid. The influence of acid used for treatment, and other reaction conditions (reaction temperature, solvent, reactant molar ratio, catalyst amount) on the reaction course were tested. Acid treated montmorillonite proved to be a catalyst suitable for this reaction – a high yield of desired product was obtained (>94%) at room temperature using different solvents. Solvent choice showed to be crucial for the reaction – the best results were obtained using nitromethane or 1,4-dioxane. The catalyst can be reused one time after calcination at 300 °C.

Association of GABRG3, GABRB3, HTR2A gene variants with autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental and neurobehavioral disorder characterized by impaired social communication, repetitive and restricted patterns of behavior, activity, or interest, and altered emotional processing. Reported prevalence is 4 times higher in men and it has increased in recent years. Immunological, environmental, epigenetic, and genetic factors play a role in the pathophysiology of autism. Many neurochemical pathways and neuroanatomical events are effective in determining the disease. It is still unclear how the main symptoms of autism occur because of this complex and heterogeneous situation. In this study, we focused on gamma amino butyric acid (GABA) and serotonin, which are thought to contribute to the etiology of autism; it is aimed to elucidate the mechanism of the disease by investigating variant changes in the GABA receptor subunit genes GABRB3, GABRG3 and the HTR2A gene, which encodes one of the serotonin receptors.200 patients with ASD between the ages of 3–9 and 100 healthy volunteers were included in the study. Genomic DNA isolation was performed from peripheral blood samples taken from volunteers. Genotyping was performed using the RFLP method with PCR specific for specific variants. Data were analyzed with SPSS v25.0 program.According to the data obtained in our study; In terms of HTR2A (rs6313 T102C) genotypes, the homozygous C genotype carrying frequency in the patient group and the homozygous T genotype carrying frequency in the GABRG3 (rs140679 C/T) genotypes were found to be significantly higher in the patient group compared to the control group (*p: 0.0001, p: 0.0001). It was determined that the frequency of individuals with homozygous genotype was significantly higher in the patient group compared to the control group and having homozygous genotypes increased the disease risk approximately 1.8 times. In terms of GABRB3 (rs2081648 T/C) genotypes, it was determined that there was no statistically significant difference in the frequency of carrying homozygous C genotype in the patient group compared to the control group (p: 0.36).According to the results of our study, we think that the HTR2A (rs6313 T102C) polymorphism is effective in modulating the empathic and autistic characteristics of individuals, and that the HTR2A (rs6313 T102C) polymorphism is more distributed in the post-synaptic membranes in individuals with a higher number of C alleles. We believe that this situation can be attributed to the spontaneous stimulatory distribution of the HTR2A gene in the postsynaptic membranes because of T102C transformation.In genetically based autism cases, carrying the point mutation in the rs6313 variant of the HTR2A gene and the C allele and the point mutation in the rs140679 variant of the GABRG3 gene and accordingly carrying the T allele provide a predisposition to the disease.

Learning in the Single-Cell Organism Physarum polycephalum: Effect of Propofol.

Propofol belongs to a class of molecules that are known to block learning and memory in mammals, including rodents and humans. Interestingly, learning and memory are not tied to the presence of a nervous system. There are several lines of evidence indicating that single-celled organisms also have the capacity for learning and memory which may be considered as basal intelligence. Here, we introduce a new experimental model for testing the learning ability of Physarum polycephalum, a model organism frequently used to study single-celled "intelligence". In this study, the impact of propofol on Physarum's "intelligence" was tested. The model consists of a labyrinth of subsequent bifurcations in which food (oat flakes soaked with coconut oil-derived medium chain triglycerides [MCT] and soybean oil-derived long chain triglycerides [LCT]) or propofol in MCT/LCT) is placed in one of each Y-branch. In this setting, it was tested whether Physarum memorized the rewarding branch. We saw that Physarum was a quick learner when capturing the first bifurcations of the maze; thereafter, the effect decreased, perhaps due to reaching a state of satiety. In contrast, when oat flakes were soaked with propofol, Physarum's preference for oat flakes declined significantly. Several possible actions, including the blocking of gamma-aminobutyric acid (GABA) receptor signaling, are suggested to account for this behavior, many of which can be tested in our new model.

The serine hydrolase ABHD6 controls survival and thermally induced seizures in a mouse model of Dravet syndrome

Evidence suggests that inhibition of α/β hydrolase-domain containing 6 (ABHD6) reduces seizures; however, the molecular mechanism of this therapeutic response remains unknown. We discovered that heterozygous expression of Abhd6 (Abhd6+/−) significantly reduced the premature lethality of Scn1a+/− mouse pups, a genetic mouse model of Dravet Syndrome (DS). Both Abhd6+/− mutation and pharmacological inhibition of ABHD6 reduced the duration and incidence of thermally induced seizures in Scn1a+/− pups. Mechanistically, the in vivo anti-seizure response resulting from ABHD6 inhibition is mediated by potentiation of gamma-aminobutyric acid receptors Type-A (GABAAR). Brain slice electrophysiology showed that blocking ABHD6 potentiates extrasynaptic (tonic) GABAAR currents that reduce dentate granule cell excitatory output without affecting synaptic (phasic) GABAAR currents. Our results unravel an unexpected mechanistic link between ABHD6 activity and extrasynaptic GABAAR currents that controls hippocampal hyperexcitability in a genetic mouse model of DS. Brief summaryThis study provides the first evidence for a mechanistic link between ABHD6 activity and the control of extrasynaptic GABAAR currents that controls hippocampal hyperexcitability in a genetic mouse model of Dravet Syndrome and can be targeted to dampened seizures.

Gamma-Aminobutyric Acid Type A Receptor Variants are Associated with Autism Spectrum Disorders.

Despite several efforts to identify the causes of autism spectrum disorders (ASD), its etiology remains still unclear. Among other aspects, genes that encode neurotransmitter receptors are strong candidates for autism. Here, we wanted to study some genetic variants of gamma-aminobutyric acid (GABA) receptor subunit genes GABRB3, GABRG3, and GABRA5, located on chromosome 15q11-q13 that might contribute to the etiology of ASD in the affected children of West Bengal. rs7180158, rs2081648 (GABRB3); rs12910555 (GABRG3); rs35399885, rs35832850 (GABRA5) were analyzed in 316 children with ASD and 227 healthy controls. Phenotypic associations were evaluated by Childhood Autism Rating Scale (CARS). Gene expression levels were measured by quantitative real-time PCR. ASD probands showed a higher frequency of "A" allele for rs7180158, "G" allele for rs12901555, and "T" allele for rs35399885. The GA + AA genotypes (rs7180158) and CT + TT genotypes (rs35399885) were found to confer significant risk towards ASD. rs2081648 was found to have transmission bias in the family. Additionally, these variants were found to be associated with one or more of ASD-associated phenotypic traits. Multifactor dimensionality reduction (MDR) analyses showed mostly independent contributory effects of some of the variants. Again, the gene expression levels of GABRB3, GABRG3, and GABRA5 were downregulated in the cases than the controls. ForGABRA5 rs35399885, the CC genotypes corresponded to higher expression levels compared to the other groups. This study reveals that genetic variants of GABAA receptor subunit genes are significantly associated with ASD. No data for the mentioned variants are found in the population of West Bengal, India.

Developmental changes in brain activity of heterozygous Scn1a knockout rats.

Dravet syndrome (DS) is an infantile-onset developmental and epileptic encephalopathy characterized by an age-dependent evolution of drug-resistant seizures and poor developmental outcomes. Functional impairment of gamma-aminobutyric acid (GABA)ergic interneurons due to loss-of-function mutation of SCN1A is currently considered the main pathogenesis. In this study, to better understand the age-dependent changes in the pathogenesis of DS, we characterized the activity of different brain regions in Scn1a knockout rats at each developmental stage. We established an Scn1a knockout rat model and examined brain activity from postnatal day (P) 15 to 38 using a manganese-enhanced magnetic resonance imaging technique (MEMRI). Scn1a heterozygous knockout (Scn1a +/-) rats showed a reduced expression of voltage-gated sodium channel alpha subunit 1 protein in the brain and heat-induced seizures. Neural activity was significantly higher in widespread brain regions of Scn1a +/- rats than in wild-type rats from P19 to P22, but this difference did not persist thereafter. Bumetanide, a Na+-K+-2Cl- cotransporter 1 inhibitor, mitigated hyperactivity to the wild-type level, although no change was observed in the fourth postnatal week. Bumetanide also increased heat-induced seizure thresholds of Scn1a +/- rats at P21. In Scn1a +/- rats, neural activity in widespread brain regions increased during the third postnatal week, corresponding to approximately 6 months of age in humans, when seizures most commonly develop in DS. In addition to impairment of GABAergic interneurons, the effects of bumetanide suggest a possible contribution of immature type A gamma-aminobutyric acid receptor signaling to transient hyperactivity and seizure susceptibility during the early stage of DS. This hypothesis should be addressed in the future. MEMRI is a potential technique for visualizing changes in basal brain activity in developmental and epileptic encephalopathies.

Corticosterone injection into the infralimbic prefrontal cortex enhances fear memory extinction: Involvement of GABA receptors and the extracellular signal-regulated kinase

This study investigated the interactive effect of glucocorticoid and Gamma-aminobutyric acid (GABA) receptors in the Infralimbic (IL) cortex on fear extinction in rats' auditory fear conditioning task (AFC).Animals received 3 conditioning trial tones (conditioned stimulus, 30 s, 4 kHz, 80 dB) co-terminated with a footshock (unconditioned stimulus, 0.8 mA, 1 s). Extinction testing was conducted over 3 days (Ext 1–3) after conditioning. Intra-IL injection of corticosterone (CORT, 20 ng/0.3 µl/side) was performed 15 min before the first extinction trial (Ext 1) which attenuated auditory fear expression in subsequent extinction trials (Ext 1–3), demonstrating fear memory extinction enhancement. Co-injection of the GABAA agonist muscimol (250 ng/0.3 µl/side) or the GABAB agonist baclofen (250 ng/0.3 µl/side) 15 min before corticosterone, did not significantly affect the facilitative effects of corticosterone on fear extinction. However, co-injection of the GABAA antagonist bicuculline (BIC, 100 ng/0.3 µl/side) or the GABAB antagonist CGP35348 (CGP, 100 ng/0.3 µl/side) 15 min before corticosterone, blocked the facilitative effects of corticosterone on fear extinction. Moreover, extracellular signal-regulated kinase (ERK) and cAMP response element-binding (CREB) in the IL were examined by Western blotting analysis after the first extinction trial (Ext 1) in some groups. Intra-IL injection of corticosterone increased the ERK activity but not CREB. Co-injection of the bicuculline or CGP35348 blocked the enhancing effect of corticosterone on ERK expression in the IL.Glucocorticoid receptors (GRs) activation in the IL cortex by corticosterone increased ERK activity and facilitated fear extinction. GABAA or GABAB antagonists decreased ERK activity and inhibited corticosterone's effect. GRs and GABA receptors in the IL cortex jointly modulate the fear extinction processes via the ERK pathway. This pre-clinical animal study may highlight GRs and GABA interactions in the IL cortex modulating fear memory processes in fear-related disorders such as post-traumatic stress disorder (PTSD).

The toxic natural product tutin causes epileptic seizures in mice by activating calcineurin

Tutin, an established toxic natural product that causes epilepsy in rodents, is often used as a tool to develop animal model of acute epileptic seizures. However, the molecular target and toxic mechanism of tutin were unclear. In this study, for the first time, we conducted experiments to clarify the targets in tutin-induced epilepsy using thermal proteome profiling. Our studies showed that calcineurin (CN) was a target of tutin, and that tutin activated CN, leading to seizures. Binding site studies further established that tutin bound within the active site of CN catalytic subunit. CN inhibitor and calcineurin A (CNA) knockdown experiments in vivo proved that tutin induced epilepsy by activating CN, and produced obvious nerve damage. Together, these findings revealed that tutin caused epileptic seizures by activating CN. Moreover, further mechanism studies found that N-methyl-D-aspartate (NMDA) receptors, gamma-aminobutyric acid (GABA) receptors and voltage- and Ca2+- activated K+ (BK) channels might be involved in related signaling pathways. Our study fully explains the convulsive mechanism of tutin, which provides new ideas for epilepsy treatment and drug development.

Prolonged Alprazolam Treatment Alters Components of Glutamatergic Neurotransmission in the Hippocampus of Male Wistar Rats—The Neuroadaptive Changes following Long-Term Benzodiazepine (Mis)Use

Alprazolam (ALP), a benzodiazepine (BDZ) used to treat anxiety, panic, and sleep disorders, is one of the most prescribed psychotropic drugs worldwide. The side effects associated with long-term (mis)use of ALP have become a major challenge in pharmacotherapy, emphasizing the unmet need to further investigate their underlying molecular mechanisms. Prolonged BDZ exposure may induce adaptive changes in the function of several receptors, including the primary target, gammaaminobutyric acid receptor type A (GABAAR), but also other neurotransmitter receptors such as glutamatergic. The present study investigated the potential effects of prolonged ALP treatment on components of glutamatergic neurotransmission, with special emphasis on N-Methyl-D-aspartate receptor (NMDAR) in the hippocampus of adult male Wistar rats. The study revealed behavioral changes consistent with potential onset of tolerance and involvement of the glutamatergic system in its development. Specifically, an increase in NMDAR subunits (NR1, NR2A, NR2B), a decrease in vesicular glutamate transporter 1 (vGlut1), and differential modulation of excitatory amino acid transporters 1 and 2 (EAAT1/2, in vivo and in vitro) were observed, alongside a decrease in α1-containing GABAAR following the treatment. By describing the development of compensatory actions in the glutamatergic system, the present study provides valuable information on neuroadaptive mechanisms following prolonged ALP intake.

Neuroprotective activity of novel phenanthrene derivative from Grewia tiliaefolia by in vitro and in silico studies

Medicinal plants possess range of phytochemicals accountable for their diverse biological activities. Presently, such compounds have been isolated from medicinal plants, characterized and evaluated for their pharmacological potential. In the present study, the efforts have been made to isolate the compound(s) from Grewia tiliaefolia Vahl., plant known for its ameliorative effect on brain related diseases such as anxiety, depression, cognitive disorders and Parkinson’s disease. Plant extract was subjected to isolation of compound(s) using column chromatography and isolated compound was characterized by NMR FTIR and LCMS. The isolated compound was novel with the IUPAC name of the compound is propyl 3-hydroxy-10,13-dimethyl-6,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a]phenanthrene-17-carboxylate, designated as A-1 and has not been reported before. A-1 was further evaluated for its antioxidant potential using in vitro antioxidant assays (2,2-diphenyl-1-picryl-hydrazyl-hydrate, DPPH assay and reducing power assay, RPA). Also, Acetylcholinesterase (AChE) inhibitory potential of A-1 and extract was analysed. Results showed that A-1 exhibited significantly higher antioxidant activity in both DPPH and RPA assay as compared to plant extract. In case of AChE inhibitory activity again, A-1 has shown significantly higher activity as compared to plant extract. In silico study was conducted to predict its action on proteins playing crucial role in neurological and neurodegenerative disorders such as gamma amino butyric acid (GABA) receptor and glutamate α amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (Glu AMPA) receptor in epilepsy and AChE enzyme in Alzheimer’s diseases. The compound has shown interaction in following order: AChE > GABA receptor > Glu AMPA receptor. Further, molecular dynamic simulations and ADME studies of A-1 and AChE enzyme revealed that A-1 yielded good results in all parameters and hence can relieve Alzheimer’s like symptoms.

Gamma-aminobutyric acid (GABA) suppresses hemocyte phagocytosis by binding to GABA receptors and modulating corresponding downstream pathways in blood clam, Tegillarca granosa

Although accumulating data demonstrated that gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, plays an important regulatory role in immunity of vertebrates, its immunomodulatory function and mechanisms of action remain poorly understood in invertebrates such as bivalve mollusks. In this study, the effect of GABA on phagocytic activity of hemocytes was evaluated in a commercial bivalve species, Tegillarca granosa. Furthermore, the potential regulatory mechanism underpinning was investigated by assessing potential downstream targets. Data obtained demonstrated that in vitro GABA incubation significantly constrained the phagocytic activity of hemocytes. In addition, the GABA-induced suppression of phagocytosis was markedly relieved by blocking of GABAA and GABAB receptors using corresponding antagonists. Hemocytes incubated with lipopolysaccharides (LPS) and GABA had significant higher K+-Cl- cotransporter 2 (KCC2) content compared to the control. In addition, GABA treatment led to an elevation in intracellular Cl−, which was shown to be leveled down to normal by blocking the ionotropic GABAA receptor. Treatment with GABAA receptor antagonist also rescued the suppression of GABAA receptor-associated protein (GABARAP), KCC, TNF receptor associated factor 6 (TRAF6), inhibitor of nuclear factor kappa-B kinase subunit alpha (IKKα), and nuclear factor kappa B subunit 1 (NFκB) caused by GABA incubation. Furthermore, incubation of hemocytes with GABA resulted in a decrease in cAMP content, an increase in intracellular Ca2+, and downregulation of cAMP-dependent protein kinase (PKA), calmodulin kinase II (CAMK2), calmodulin (CaM), calcineurin (CaN), TRAF6, IKKα, and NFκB. All these above-mentioned changes were found to be evidently relieved by blocking the metabotropic G-protein-coupled GABAB receptor. Our results suggest GABA may play an inhibitory role on phagocytosis through binding to both GABAA and GABAB receptors, and subsequently regulating corresponding downstream pathways in bivalve invertebrates.

Understanding the function of the GABAergic system and its potential role in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a highly disabling chronic autoimmune disease. Multiple factors contribute to the complex pathological process of RA, in which an abnormal autoimmune response, high survival of inflammatory cells, and excessive release of inflammatory factors lead to a severe chronic inflammatory response. Clinical management of RA remains limited; therefore, exploring and discovering new mechanisms of action could enhance clinical benefits for patients with RA. Important bidirectional communication occurs between the brain and immune system in inflammatory diseases such as RA, and circulating immune complexes can cause neuroinflammatory responses in the brain. The gamma-aminobutyric acid (GABA)ergic system is a part of the nervous system that primarily comprises GABA, GABA-related receptors, and GABA transporter (GAT) systems. GABA is an inhibitory neurotransmitter that binds to GABA receptors in the presence of GATs to exert a variety of pathophysiological regulatory effects, with its predominant role being neural signaling. Nonetheless, the GABAergic system may also have immunomodulatory effects. GABA/GABA-A receptors may inhibit the progression of inflammation in RA and GATs may promote inflammation. GABA-B receptors may also act as susceptibility genes for RA, regulating the inflammatory response of RA via immune cells. Furthermore, the GABAergic system may modulate the abnormal pain response in RA patients. We also summarized the latest clinical applications of the GABAergic system and provided an outlook on its clinical application in RA. However, direct studies on the GABAergic system and RA are still lacking; therefore, we hope to provide potential therapeutic options and a theoretical basis for RA treatment by summarizing any potential associations.

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

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

Impact of nonalcoholic fatty liver disease-related metabolic state on depression.

Nonalcoholic fatty liver disease (NAFLD), also recently referred as metabolic (dysfunction)-associated fatty liver disease (MAFLD), is characterized by hepatocyte steatosis in the setting of a metabolic risk conditions and in the absence of an underlying precursor, for instance alcohol consumption, hepatotropic viruses and hepatotoxic drugs. A possible association between NAFLD and depression has been proposed, owing to intersecting pathophysiological pathways. This narrative review aimed to summarize the current evidence that illustrate the potential pathophysiological and clinical linkage between NAFLD-related metabolic state and depression. Prefrontal cortex lesions are suggested to be a consequence of liver steatosis-associated systematic hyperinflammatory state, a phenomenon also occurring in depression. In addition, depressive symptoms are present in neurotransmitter imbalances. These abnormalities seem to be correlated with NAFLD/MAFLD, in terms of insulin resistance (IR), ammonia and gut dysbiosis' impact on serotonin, dopamine, noradrenaline levels and GABA (gamma aminobutyric acid) receptors. Furthermore, reduced levels of nesfatin-1 and copine-6-associated BDNF (brain-derived neurotrophic factor) levels have been considered as a probable link between NAFLD and depression. Regarding NAFLD-related gut dysbiosis, it stimulates mediators including lipopolysaccharides, short-chain fatty acids and bile acids, which play significant role in depression. Finally, western diet and IR, which are mainstay components of NAFLD/MAFLD, are, also, substantiated to affect neurotransmitters in hippocampus and produce neurotoxic lipids that contribute to neurologic dysfunction, and thus trigger emotional disturbances, mainly depressive symptoms.

Proteomic and metabolomic approaches elucidate the molecular mechanism of emodin against neuropathic pain through modulating the gamma-aminobutyric acid (GABA)-ergic pathway and PI3K/AKT/NF-κB pathway.

Neuropathic pain (NeP) is a major health concern. Due to the complex pathological mechanisms, management of NeP is challenging. Emodin, a natural anthraquinone derivative, exerts excellent analgesic effects. However, its mechanisms of action are still poorly understood. In this study, we investigated the mechanisms underlying pain-relief effects of emodin in the cerebral cortex using proteomic and metabolomic approaches. After 15 days of emodin administration, the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) values in the emodin groups were significantly higher than those in the chronic constriction injury (CCI) group (p < .05), suggesting emodin treatment could reverse CCI-induced hyperalgesia. Emodin treatment evoked the expression alteration of 402 proteins (153 up-regulated and 249 down-regulated) in the CCI models, which were primarily involved in PI3K/AKT signaling pathway, gamma-aminobutyric acid (GABA) receptor signaling, complement and coagulation cascades, cGMP/PKG signaling pathway, MAPK signaling pathway, and calcium signaling pathway. In parallel, emodin intervention regulated the abundance alteration of 27 brain metabolites (20 up-regulated and 7 down-regulated) in the CCI rats, which were primarily implicated in carbon metabolism, biosynthesis of amino acids, pentose phosphate pathway, and glucagon signaling pathway. After a comprehensive analysis and western blot validation, we demonstrated that emodin alleviated NeP mainly through regulating GABAergic pathway and PI3K/AKT/NF-κB pathway.

GABAA Receptor and Serotonin Transporter Expression Changes Dissociate Following Mild Traumatic Brain Injury: Influence of Sex and Estrus Cycle Phase in Rats

Mild traumatic brain injuries (mild TBIs) can affect both males and females, but females are more likely to report long-term psychological complications, including changes in mood and generalized anxiety. Additionally, reproductive cycle phase has been shown to affect mild TBI symptom expression within females. These variances may result from sex differences in mild TBI-induced alterations to neurotransmission in brain regions that influence mood and emotion, possibly mediated by sex steroids. The hippocampus and amygdala are implicated in stress responses and anxiety, and within these regions, gamma-aminobutyric acid (GABA) and serotonin modulate output and behavioral expression. Metabolites of progesterone can allosterically enhance GABAergic signaling, and sex steroids are suggested to regulate the expression of the serotonin transporter (SERT). To determine how mild TBI might alter GABA receptor and SERT expression in males and females, immunocytochemistry was used to quantify expression of the alpha-1 subunit of the GABAA receptor (α1-GABAA), SERT, and a neuronal marker (NeuN) in the brains of adult male and naturally-cycling female rats, both with and without mild TBI, 17 days after injury. Mild TBI altered the expression of α1-GABAA in the amygdala and hippocampus in both sexes, but the direction of change observed depended on sex and reproductive cycle phase. In contrast, mild TBI had little effect on SERT expression. However, SERT expression differed between sexes and varied with the cycle phase. These findings demonstrate that regulation of neurotransmission following mild TBI differs between males and females, with implications for behavioral outcomes and the efficacy of therapeutic strategies.

Interaction between γ-Hydroxybutyric Acid and Ethanol: A Review from Toxicokinetic and Toxicodynamic Perspectives.

Gamma-hydroxybutyric acid (GHB) is a potent, short-acting central nervous system depressant as well as an inhibitory neurotransmitter or neuromodulator derived from gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter. The sodium salt of GHB, sodium oxybate, has been used for the treatment of narcolepsy and cataplexy, whereas GHB was termed as a date rape drug or a club drug in the 1990s. Ethanol is the most co-ingested drug in acute GHB intoxication. In this review, the latest findings on the combined effects of GHB and ethanol are summarized from toxicokinetic and toxicodynamic perspectives. For this purpose, we mainly discussed the pharmacology and toxicology of GHB, GHB intoxication under alcohol consumption, clinical cases of the combined intoxication of GHB and ethanol, and previous studies on the toxicokinetic and toxicodynamic interactions between GHB and ethanol in humans, animals, and an in vitro model. The combined administration of GHB and ethanol enhanced sedation and cardiovascular dysfunction, probably by the additive action of GABA receptors, while toxicokinetic changes of GHB were not significant. The findings of this review will contribute to clinical and forensic interpretation related to GHB intoxication. Furthermore, this review highlights the significance of studies aiming to further understand the enhanced inhibitory effects of GHB induced by the co-ingestion of ethanol.

Phenobarbital and Alcohol Withdrawal Syndrome: A Systematic Review and Meta-Analysis.

Alcohol withdrawal syndrome (AWS) is a complication frequently encounteredamongpatients who are chronic alcohol abusers. It is considered to have a significant impact on the United States healthcare system. It not only has a toll on the healthcare spending but also contributes to significant morbidity and mortality. Benzodiazepines are considered first line in the treatment of AWS. Since patients with alcohol use disorder have downregulated gamma aminobutyric acid (GABA) receptors, this often leads to benzodiazepine resistance. Phenobarbital is also usedin the management of alcohol withdrawal syndrome. Here we present a systematic review and meta-analysis of the efficacy and safety of the drug. We conducted an electronic database search for relevant studies published between the inception of the project and November 20, 2022, in three databases, including Medline/PubMed, Embase, and Cochrane Library. Our study included all original studies with prime focus on the baseline characteristics of patients admitted to the intensive care unit (ICU) for alcohol withdrawal syndrome and management/monitoring protocol implemented for its treatment.The primary outcomes that were the focus of our study consisted of changes in the length of hospital stay, length of ICU stay, and changes in scoring systems (for alcohol withdrawal assessment and monitoring) following the implementation of phenobarbital. The secondary outcomes included complications such as intubation and mortality. Based on our analysis, the mean difference in hospital stay was statistically significant at -2.6 (95% CI, -4.48, -0.72, P=0.007) for phenobarbital compared to the benzodiazepine group. We were unable to comment on the heterogeneity in our meta-analysis due to the standard deviationnot being reported in one study. There was no statistically significant difference regarding the length of stay in the intensive care unit compared to the control/comparative arm, with a mean difference of -1.17 (95% CI, -1.17, 0.09, P=0.07), with considerable heterogeneity (I2=77%, P=0.002). Our meta-analysis also investigated the risk of intubation between the phenobarbital and the control/comparative group. There was statistically significant difference in the incidence of intubation, relative risk (RR) 0.52 (95% CI, 0.25, 1.08, P=0.08), with considerable heterogeneity (I2=80%, P=0.0001). Our study concludes that phenobarbital is an effective tool in the management of AWS in an ICU setting. However, various studies have reported contradictory results, and vital information appears to be lacking. Moreover, there is a lack of uniformity in terms of phenobarbital dosing. Drug administration should be adapted according to the severity of the symptoms. Further studies need to be conducted discussing the safety profile and adverse effects of the drug when it comes to the management of alcohol withdrawal syndrome.

Modulation of GABAB receptors in the insula bidirectionally affects associative memory of epilectic rats in both spatial and non-spatial operant tasks.

Stimulation of gamma-aminobutyric acid (GABA) activity through GABA receptor agonists is the basic mechanism of many anticonvulsant drugs. Nevertheless, many of these GABergic drugs have adverse cognitive effects. We previously found that GABAB receptors (GABABRs) in the insula regulate operant associative memory in healthy rats. The present study aimed at investigating the effects of GABABR modulation in the insula on operant associative memory in epileptic rats, along with the underlying mechanisms. The lithium-pilocarpine model of temporal lobe epilepsy (TLE) was established in male Sprague-Dawley rats. A 22-gauge stainless-steel guide cannula was surgically implanted into the granular insula cortex of the epileptic rats. Baclofen (125 ng/μl, 1 μl), CGP35348 (12.5 μg/μl, 1 μl), or saline (1 μl) was slowly infused through the guide cannula. The Intellicage automated behavioral testing system was used to evaluate operant associative memory of the epileptic rats, including non-spatial operant tasks (basic nosepoke learning and skilled nosepoke learning) and spatial operant tasks (chamber position learning). The expression of the GABABR subunits GB1 and GB2 in the insula was examined by immunofluorescence and Western blotting. The Intellicage tests demonstrated that baclofen significantly impaired basic nosepoke learning, skilled nosepoke learning and chamber position learning of the epileptic rats, while CGP35348 boosted these functions. Immunofluorescence staining revealed that GB1 and GB2 were expressed in the insula of the epileptic rats, and Western blotting analysis showed that baclofen enhanced while CGP35348 inhibited the expression of these subunits. GABABRs in the insula bidirectionally regulate both spatial and non-spatial operant associative memory of epileptic rats. Effects of GABABRs on cognition should be taken into account when evaluating new possible treatments for people with epilepsy.