GABA Transporter Research Articles

Ventral tegmental area GABA, glutamate, and glutamate-GABA neurons are heterogeneous in their electrophysiological and pharmacological properties.

The ventral tegmental area (VTA) contains dopamine neurons intermixed with GABA-releasing (expressing vesicular GABA transporter, VGaT), glutamate-releasing (expressing vesicular glutamate transporter 2, VGluT2), and glutamate-GABA co-releasing (co-expressing VGluT2 and VGaT) neurons. By delivering INTRSECT viral vectors into the VTA of double vglut2-Cre/vgat-Flp transgenic mice, we targeted specific VTA cell populations for ex vivo recordings. We found that VGluT2+ VGaT- and VGluT2+ VGaT+ neurons on average had relatively hyperpolarized resting membrane potential, greater rheobase, and lower spontaneous firing frequency compared to VGluT2- VGaT+ neurons, suggesting that VTA glutamate-releasing and glutamate-GABA co-releasing neurons require stronger excitatory drive to fire than GABA-releasing neurons. In addition, we detected expression of Oprm1mRNA (encoding µ opioid receptors, MOR) in VGluT2+ VGaT- and VGluT2- VGaT+ neurons, and that the MOR agonist DAMGO hyperpolarized neurons with these phenotypes. Collectively, we demonstrate the utility of the double transgenic mouse to access VTA glutamate, glutamate-GABA, and GABA neurons to determine their electrophysiological properties. SIGNIFICANT STATEMENT: Some physiological properties of VTA glutamate-releasing and glutamate-GABA co-releasing neurons are distinct from those of VTA GABA-releasing neurons. µ-opioid receptor activation hyperpolarizes some VTA glutamate-releasing and some GABA-releasing neurons.

Exercise Ameliorates Fluoride-induced Anxiety- and Depression-like Behavior in Mice: Role of GABA

Fluoride exposure caused anxiety- and depression-like behavior in mice. Meanwhile, exercise contributes to relieve anxiety and depression. However, the effects of exercise on anxiety- and depression-like behavior in fluorosis mice remain unclear. In the current study, thirty-six Institute of Cancer Research (ICR) female mice were randomly assigned to four groups: control group (C, gavage with distilled water); exercise group (E, gavage with distilled water and treadmill exercise (speed, 10 m/min; time, 30 min/day)); fluoride group (F, gavage with 24 mg/kg sodium fluoride (NaF)); and exercise plus fluoride group (EF, gavage with 24 mg/kg NaF and treadmill exercise). All treatments lasted for 8 weeks. A number of entries into and time spent in the open zone in the elevated zero maze (EZM), resting time in the tail suspension test (TST) and levels of serotonin (5-HT) and gamma-aminobutyric acid (GABA), were significantly altered in F when compared to C. Meanwhile, the anxiety-like behavior in the EZM and the depression-like behavior in the TST were significantly improved in EF when compared to group F. Exercise significantly enhanced fluoride-induced low GABA level, with less effect on the concentration of 5-HT. Moreover, the mRNA and protein expressions of GABA synthesis and transport-related proteins of glutamic acid decarboxylase (GAD) 65 and GAD67 and vesicular GABA transporter (VGAT) were all strikingly decreased in F, while those in EF were increased. In conclusion, exercise ameliorates anxiety- and depression-like behavior in fluorosis mice through increasing the expressions of GABA synthesis and transport-related proteins, rather than 5-HT system.

Metabolic Profiling of Suprachiasmatic Nucleus Reveals Multifaceted Effects in an Alzheimer's Disease Mouse Model.

Background:Circadian rhythm disturbance is commonly observed in Alzheimer’s disease (AD). In mammals, these rhythms are orchestrated by the superchiasmatic nucleus (SCN). Our previous study in the Tg2576 AD mouse model suggests that inflammatory responses, most likely manifested by low GABA production, may be one of the underlying perpetrators for the changes in circadian rhythmicity and sleep disturbance in AD. However, the mechanistic connections between SCN dysfunction, GABA modulation, and inflammation in AD is not fully understood.Objective:To reveal influences of amyloid pathology in Tg2576 mouse brain on metabolism in SCN and to identify key metabolic sensors that couple SCN dysfunction with GABA modulation and inflammation.Methods:High resolution magic angle spinning (HR-MAS) NMR in conjunction with multivariate analysis was applied for metabolic profiling in SCN of control and Tg2576 female mice. Immunohistochemical analysis was used to detect neurons, astrocytes, expression of GABA transporter 1 (GAT1) and Bmal1.Results:Metabolic profiling revealed significant metabolic deficits in SCN of Tg2576 mice. Reductions in glucose, glutamate, GABA, and glutamine provide hints toward an impaired GABAergic glucose oxidation and neurotransmitter cycling in SCN of AD mice. In addition, decreased redox co-factor NADPH and glutathione support a redox disbalance. Immunohistochemical examinations showed low expression of the core clock protein, Bmal1, especially in activated astrocytes. Moreover, decreased expression of GAT1 in astrocytes indicates low GABA recycling in this cell type.Conclusion:Our results suggest that redox disbalance and compromised GABA signaling are important denominators and connectors between neuroinflammation and clock dysfunction in AD.

GABAA receptor agonist cinazepam and its active metabolite 3-hydroxyphenazepam act differently at the presynaptic site

Cinazepam C19H14BrClN2O5, (“LevanaⓇ ІC”) a partial GABAA receptor agonist, and its active metabolite 3-hydroxyphenazepam C15H10BrClN2O2 were comparatively assessed in vitro using nerve terminals isolated from rat cortex (synaptosomes). At the presynaptic site, cinazepam (100 and 200 µM) facilitated synaptosomal transporter-mediated [3H]GABA uptake by enhancing both the initial rate and accumulation, and decreased the ambient level and transporter-mediated release of [3H]GABA. Whereas, 3-hydroxyphenazepam decreased the uptake and did not change the ambient synaptosomal level and transporter-mediated release of [3H]GABA. To exclude GABA transporter influence, NO-711, the transporter blocker, was applied and it was found that exocytotic release of [3H]GABA decreased, whereas tonic release of [3H]GABA was not changed in the presence of both cinazepam or 3-hydroxyphenazepam after treatment of synaptosomes with NO-711. In fluorimetric studies using potential- and pH-sensitive dyes rhodamine 6G and acridine orange, respectively, it was found that cinazepam hyperpolarized the synaptosomal plasma membrane, and increased synaptic vesicle acidification, whereas, 3-hydroxyphenazepam demonstrated opposite effects on these parameters. Therefore, action of cinazepam and its active metabolite 3-hydroxyphenazepam on GABAergic neurotransmission was different. Therapeutic effects of cinazepam can be associated with its ability to hyperpolarize the plasma membrane, to increase synaptic vesicle acidification and capacity of its active metabolite 3-hydroxyphenazepam to inhibit GABA transporter functioning.

Utilizing an Animal Model to Identify Brain Neurodegeneration-Related Biomarkers in Aging.

Glycine N-methyltransferase (GNMT) regulates S-adenosylmethionine (SAMe), a methyl donor in methylation. Over-expressed SAMe may cause neurogenic capacity reduction and memory impairment. GNMT knockout mice (GNMT-KO) was applied as an experimental model to evaluate its effect on neurons. In this study, proteins from brain tissues were studied using proteomic approaches, Haemotoxylin and Eosin staining, immunohistochemistry, Western blotting, and ingenuity pathway analysis. The expression of Receptor-interacting protein 1(RIPK1) and Caspase 3 were up-regulated and activity-dependent neuroprotective protein (ADNP) was down-regulated in GNMT-KO mice regardless of the age. Besides, proteins related to neuropathology, such as excitatory amino acid transporter 2, calcium/calmodulin-dependent protein kinase type II subunit alpha, and Cu-Zn superoxide dismutase were found only in the group of aged wild-type mice; 4-aminobutyrate amino transferase, limbic system-associated membrane protein, sodium- and chloride-dependent GABA transporter 3 and ProSAAS were found only in the group of young GNMT-KO mice and are related to function of neurons; serum albumin and Rho GDP dissociation inhibitor 1 were found only in the group of aged GNMT-KO mice and are connected to neurodegenerative disorders. With proteomic analyses, a pathway involving Gonadotropin-releasing hormone (GnRH) signal was found to be associated with aging. The GnRH pathway could provide additional information on the mechanism of aging and non-aging related neurodegeneration, and these protein markers may be served in developing future therapeutic treatments to ameliorate aging and prevent diseases.

Role of trace amine‑associated receptor 1 in the medial prefrontal cortex in chronic social stress-induced cognitive deficits in mice

Emerging evidence supports an essential role of trace amine-associated receptor 1 (TAAR1) in neuropsychiatric disorders such as depression and schizophrenia. Stressful events are critical contributors to various neuropsychiatric disorders. This study examined the role of TAAR1 in mediating the negative outcomes of stressful events. In mice that experienced chronic social defeat stress but not acute stress, a significant reduction in the TAAR1 mRNA level was found in the medial prefrontal cortex (mPFC), a brain region that is known to be vulnerable to stress experience. Conditional TAAR1 knockout in the mPFC mimicked the cognitive deficits induced by chronic stress. In addition, chronic treatment with the selective TAAR1 partial agonist RO5263397 ameliorated chronic stress-induced changes in cognitive function, dendritic arborization, and the synapse number of pyramidal neurons in the mPFC but did not affect chronic stress-induced anxiety-like behaviors. Biochemically, chronic stress reduced the ratio of vesicular transporters of glutamate-1 (VGluT1) / vesicular GABA transporter (VGAT) in the mPFC，most prominently in the prelimbic cortex, and RO5263397 restored the excitatory-inhibitory (E/I) imbalance. Together, the results of this study reveal an essential role of TAAR1 in mediating chronic stress-induced cognitive impairments and suggest that TAAR1 agonists may be uniquely useful to treat MDD-related cognitive impairments.

Downregulation of GABA Transporter 3 (GAT3) is Associated with Deficient Oxidative GABA Metabolism in Human Induced Pluripotent Stem Cell-Derived Astrocytes in Alzheimer's Disease.

Alterations in neurotransmitter homeostasis, primarily of glutamate and GABA, is strongly implicated in the pathophysiology of Alzheimer's disease (AD). Homeostasis at the synapse is maintained by neurotransmitter recycling between neurons and astrocytes. Astrocytes support neuronal transmission through glutamine synthesis, which can be derived from oxidative metabolism of GABA. However, the precise implications of astrocytic GABA metabolism in AD remains elusive. The aim of this study was to investigate astrocytic GABA metabolism in AD pathology implementing human induced pluripotent stem cells derived astrocytes. Metabolic mapping of GABA was performed with [U-13C]GABA stable isotopic labeling using gas chromatography coupled to mass spectrometry (GC-MS). Neurotransmitter and amino acid content was quantified via high performance liquid chromatography (HPLC) and protein expression was investigated by Western blot assay. Cell lines carrying mutations in either amyloid precursor protein (APP) or presenilin1 (PSEN-1) were used as AD models and were compared to a control cell line of the same genetic background. AD astrocytes displayed a reduced oxidative GABA metabolism mediated by a decreased uptake capacity of GABA, as GABA transporter 3 (GAT3) was downregulated in AD astrocytes compared to the controls. Interestingly, the carbon backbone of GABA in AD astrocytes was utilized to a larger extent to support glutamine synthesis compared to control astrocytes. The results strongly indicate alterations in GABA uptake and metabolism in AD astrocytes linked to reduced GABA transporter expression, hereby contributing further to neurotransmitter disturbances.

Unique dynamics and exocytosis properties of GABAergic synaptic vesicles revealed by three-dimensional single vesicle tracking

Maintaining the balance between neuronal excitation and inhibition is essential for proper function of the central nervous system. Inhibitory synaptic transmission plays an important role in maintaining this balance. Although inhibitory transmission has higher kinetic demands compared to excitatory transmission, its properties are poorly understood. In particular, the dynamics and exocytosis of single inhibitory vesicles have not been investigated, due largely to both technical and practical limitations. Using a combination of quantum dots (QDs) conjugated to antibodies against the luminal domain of the vesicular GABA transporter to selectively label GABAergic (i.e., predominantly inhibitory) vesicles together with dual-focus imaging optics, we tracked the real-time three-dimensional position of single GABAergic vesicles up to the moment of exocytosis (i.e., fusion). Using three-dimensional trajectories, we found that GABAergic synaptic vesicles traveled a shorter distance prior to fusion and had a shorter time to fusion compared to synaptotagmin-1 (Syt1)-labeled vesicles, which were mostly from excitatory neurons. Moreover, our analysis revealed that GABAergic synaptic vesicles move more straightly to their release sites than Syt1-labeled vesicles. Finally, we found that GABAergic vesicles have a higher prevalence of kiss-and-run fusion than Syt1-labeled vesicles. These results indicate that inhibitory synaptic vesicles have a unique set of dynamics and exocytosis properties to support rapid synaptic inhibition, thereby maintaining a tightly regulated coordination between excitation and inhibition in the central nervous system.

Altered Parvalbumin Basket Cell Terminals in the Cortical Visuospatial Working Memory Network in Schizophrenia

BackgroundVisuospatial working memory (vsWM), which is commonly impaired in schizophrenia, involves information processing across the primary visual cortex, association visual cortex, posterior parietal cortex, and dorsolateral prefrontal cortex (DLPFC). Within these regions, vsWM requires inhibition from parvalbumin-expressing basket cells (PVBCs). Here, we analyzed indices of PVBC axon terminals across regions of the vsWM network in schizophrenia. MethodsFor 20 matched pairs of subjects with schizophrenia and unaffected comparison subjects, tissue sections from the primary visual cortex, association visual cortex, posterior parietal cortex, and DLPFC were immunolabeled for PV, the 65- and 67-kDa isoforms of glutamic acid decarboxylase (GAD65 and GAD67) that synthesize GABA (gamma-aminobutyric acid), and the vesicular GABA transporter. The density of PVBC terminals and of protein levels per terminal was quantified in layer 3 of each cortical region using fluorescence confocal microscopy. ResultsIn comparison subjects, all measures, except for GAD65 levels, exhibited a caudal-to-rostral decline across the vsWM network. In subjects with schizophrenia, the density of detectable PVBC terminals was significantly lower in all regions except the DLPFC, whereas PVBC terminal levels of PV, GAD67, and GAD65 proteins were lower in all regions. A composite measure of inhibitory strength was lower in subjects with schizophrenia, although the magnitude of the diagnosis effect was greater in the primary visual, association visual, and posterior parietal cortices than in the DLPFC. ConclusionsIn schizophrenia, alterations in PVBC terminals across the vsWM network suggest the presence of a shared substrate for cortical dysfunction during vsWM tasks. However, regional differences in the magnitude of the disease effect on an index of PVBC inhibitory strength suggest region-specific alterations in information processing during vsWM tasks.

Influence of glutamate and GABA transport on brain excitatory/inhibitory balance.

An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance-as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer's disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)-leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.

Baclofen decreases compulsive alcohol drinking in rats characterized by reduced levels of GAT-3 in the central amygdala.

While most individuals with access to alcohol drink it recreationally, some vulnerable individuals eventually lose control over their intake and progressively develop compulsive alcohol drinking and decreased interest in alternative sources of reinforcement, two key features of addiction. The neural and molecular mechanisms underlying this vulnerability to switch from controlled to compulsive alcohol intake have not been fully elucidated. It has been shown that rats having reduced levels of expression of the gamma‐aminobutyric acid (GABA) transporter, GAT‐3, in the amygdala tend to persist in seeking and drinking alcohol even when adulterated with quinine, suggesting that pharmacological interventions aimed at restoring GABA homeostasis in these individuals may provide a targeted treatment to limit compulsive alcohol drinking. Here, we tested the hypothesis that the GABAB receptor agonist baclofen, which decreases GABA release, specifically reduces compulsive alcohol drinking in vulnerable individuals. In a large cohort of Sprague–Dawley rats allowed to drink alcohol under an intermittent two‐bottle choice procedure, a cluster of individuals was identified that persisted in drinking alcohol despite adulteration with quinine or when an alternative ingestive reinforcer, saccharin, was available. In these rats, which were characterized by decreased GAT‐3 mRNA levels in the central amygdala, acute baclofen administration (1.5 mg/kg, intraperitoneal) resulted in a decrease in compulsive drinking. These results indicate that low GAT‐3 mRNA levels in the central amygdala may represent an endophenotype of vulnerability to develop a compulsive drinking of alcohol that is shown here to be mitigated by baclofen.

Adolescent intermittent ethanol exposure does not alter responsiveness to ifenprodil or expression of vesicular GABA and glutamate transporters.

Adolescent intermittent ethanol (AIE) exposure in the rat results in a retention of adolescent-like responsiveness to ethanol into adulthood characterized by enhanced sensitivity to socially facilitating and decreased sensitivity to socially suppressing and aversive effects. Similar pattern of responsiveness to social and aversive effects of the selective glutamate NMDA NR2B receptor antagonist ifenprodil is evident in adolescent rats, suggesting that AIE would also retain this pattern of ifenprodil sensitivity into adulthood. Social (Experiment 1)and aversive (measured via conditioned taste aversion; Experiment 2) effects of ifenprodil were assessed in adult male and female rats following AIE exposure. Sensitivity to the social and aversive effects of ifenprodil was not affected by AIE exposure. Experiment 3 assessed protein expression of vesicular transporters of GABA (vGAT) and glutamate (vGlut2) within the prelimbic cortex and nucleus accumbens in adolescents versus adults and in AIE adults versus controls. vGlut2 expression was higher in adolescents relative to adults within the PrL, but lower in the NAc. AIE adults did not retain these adolescent-typical ratios. These findings suggest that AIE is not associated with the retention of adolescent-typical sensitivity to NR2B receptor antagonism, along with no AIE-induced shift in vGlut2 to vGAT ratios.

Functional Characterization of the γ-Aminobutyric Acid Transporter from Mycobacterium smegmatis MC2 155 Reveals Sodium-Driven GABA Transport.

Characterizing the mycobacterial transporters involved in the uptake and/or catabolism of host-derived nutrients required by mycobacteria may identify novel drug targets against tuberculosis. Here, we identify and characterize a member of the amino acid-polyamine-organocation superfamily, a potential γ-aminobutyric acid (GABA) transport protein, GabP, from Mycobacterium smegmatis The protein was expressed to a level allowing its purification to homogeneity, and size exclusion chromatography coupled with multiangle laser light scattering (SEC-MALLS) analysis of the purified protein showed that it was dimeric. We showed that GabP transported γ-aminobutyric acid both in vitro and when overexpressed in E. coli Additionally, transport was greatly reduced in the presence of β-alanine, suggesting it could be either a substrate or inhibitor of GabP. Using GabP reconstituted into proteoliposomes, we demonstrated that γ-aminobutyric acid uptake is driven by the sodium gradient and is stimulated by membrane potential. Molecular docking showed that γ-aminobutyric acid binds MsGabP, another Mycobacterium smegmatis putative GabP, and the Mycobacterium tuberculosis homologue in the same manner. This study represents the first expression, purification, and characterization of an active γ-aminobutyric acid transport protein from mycobacteria.IMPORTANCE The spread of multidrug-resistant tuberculosis increases its global health impact in humans. As there is transmission both to and from animals, the spread of the disease also increases its effects in a broad range of animal species. Identifying new mycobacterial transporters will enhance our understanding of mycobacterial physiology and, furthermore, provides new drug targets. Our target protein is the gene product of msmeg_6196, annotated as GABA permease, from Mycobacterium smegmatis strain MC2 155. Our current study demonstrates it is a sodium-dependent GABA transporter that may also transport β-alanine. As GABA may well be an essential nutrient for mycobacterial metabolism inside the host, this could be an attractive target for the development of new drugs against tuberculosis.

Motor Deficits Coupled to Cerebellar and Striatal Alterations in Ube3am-/p+ Mice Modelling Angelman Syndrome Are Attenuated by Adenosine A2A Receptor Blockade.

Angelman syndrome (AS) is a neurogenetic disorder involving ataxia and motor dysfunction, resulting from the absence of the maternally inherited functional Ube3a protein in neurons. Since adenosine A2A receptor (A2AR) blockade relieves synaptic and motor impairments in Parkinson's or Machado-Joseph's diseases, we now tested if A2AR blockade was also effective in attenuating motor deficits in an AS (Ube3am-/p+) mouse model and if this involved correction of synaptic alterations in striatum and cerebellum. Chronic administration of the A2AR antagonist SCH58261 (0.1 mg/kg/day, ip) promoted motor learning of AS mice in the accelerating-rotarod task and rescued the grip strength impairment of AS animals. These motor impairments were accompanied by synaptic alterations in cerebellum and striatum typified by upregulation of synaptophysin and vesicular GABA transporters (vGAT) in the cerebellum of AS mice along with a downregulation of vGAT, vesicular glutamate transporter 1 (vGLUT1) and the dopamine active transporter in AS striatum. Notably, A2AR blockade prevented the synaptic alterations found in AS mice cerebellum as well as the downregulation of striatal vGAT and vGLUT1. This provides the first indications that A2AR blockade may counteract the characteristic motor impairments and synaptic changes of AS, although more studies are needed to unravel the underlying mechanisms.

Condensing Effect of Cholesterol on hBest1/POPC and hBest1/SM Langmuir Monolayers

Human bestrophin-1 protein (hBest1) is a transmembrane channel associated with the calcium-dependent transport of chloride ions in the retinal pigment epithelium as well as with the transport of glutamate and GABA in nerve cells. Interactions between hBest1, sphingomyelins, phosphatidylcholines and cholesterol are crucial for hBest1 association with cell membrane domains and its biological functions. As cholesterol plays a key role in the formation of lipid rafts, motional ordering of lipids and modeling/remodeling of the lateral membrane structure, we examined the effect of different cholesterol concentrations on the surface tension of hBest1/POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and hBest1/SM Langmuir monolayers in the presence/absence of Ca2+ ions using surface pressure measurements and Brewster angle microscopy studies. Here, we report that cholesterol: (1) has negligible condensing effect on pure hBest1 monolayers detected mainly in the presence of Ca2+ ions, and; (2) induces a condensing effect on composite hBest1/POPC and hBest1/SM monolayers. These results offer evidence for the significance of intermolecular protein–lipid interactions for the conformational dynamics of hBest1 and its biological functions as multimeric ion channel.

Ингибирование ГАМК-трансаминазы и ГАМК-транспортеров в головном мозге с помощью вигабатрина и тиагабина ослабляет развитие судорог у крыс при дыхании гипербарическим кислородом

Hyperbaric oxygen (HBO2) inhibits the GABAergic function in the brain, which leads to the development of convulsive reactions in the form of paroxysmal discharges on the EEG and movement disorders, similar to a generalized epileptic seizure. We hypothesize that the deficiency of GABAergic neurotransmission in HBO2, which occurs due to suppression of GABA synthesis, can be overcome by blocking the clearance of GABA from the synaptic cleft and slowing down its enzymatic degradation. The present study is aimed at studying the development of seizure reactions in rats under oxygen pressure of 5 ATA after blockade of GABA transporters with tiagabine and inhibition of GABA-transaminase with vigabatrin. New data obtained in this study are: (1) inhibition of GABA transaminase by vigabatrin or GABA transporters by tiagabine prevented the development of seizures in rats under oxygen pressure of 5 ATA; (2) oxygen convulsions in HBO2 appeared with a decrease in the brain GABA by 30-40% from the initial level; (3) inhibition of GABA transaminase by vigabatrin prevented a decrease in GABA in the striatum of rats under 5 ATA pressure. Consequently, a slowdown in synaptic clearance of GABA or a weakening of the enzymatic destruction of a mediator can compensate reduced GABA synthesis in HBO2 and increase its concentration to a level sufficient for the restoration of GABAergic function preventing the development of convulsive syndrome.

A Critical Role of Hepatic GABA in the Metabolic Dysfunction and Hyperphagia of Obesity

Hepatic lipid accumulation is a hallmark of type II diabetes (T2D) and associated with hyperinsulinemia, insulin resistance, and hyperphagia. Hepatic synthesis of GABA, catalyzed by GABA-transaminase (GABA-T), is upregulated in obese mice. To assess the role of hepatic GABA production in obesity-induced metabolic and energy dysregulation, we treated mice with two pharmacologic GABA-T inhibitors and knocked down hepatic GABA-T expression using an antisense oligonucleotide. Hepatic GABA-T inhibition and knockdown decreased basal hyperinsulinemia and hyperglycemia, and improved glucose intolerance. GABA-T knockdown improved insulin sensitivity assessed by hyperinsulinemic-euglycemic clamps in obese mice. Hepatic GABA-T knockdown also decreased food intake and induced weight loss without altering energy expenditure in obese mice. Data from people with obesity support the notion that hepatic GABA production and transport are associated with serum insulin, HOMA-IR, T2D, and BMI. These results support a key role for hepatocyte GABA production in the dysfunctional glucoregulation and feeding behavior associated with obesity.

Environmental enrichment implies GAT-1 as a potential therapeutic target for stroke recovery.

Rationale: Stroke is a leading cause of adult disability worldwide, but no drug provides functional recovery during the repair phase. Accumulating evidence demonstrates that environmental enrichment (EE) promotes stroke recovery by enhancing network excitability. However, the complexities of utilizing EE in a clinical setting limit its translation.Methods: We used multifaceted approaches combining electrophysiology, chemogenetics, optogenetics, and floxed mice in a mouse photothrombotic stroke model to reveal the key target of EE-mediated stroke recovery.Results: EE reduced tonic gamma-aminobutyric acid (GABA) inhibition and facilitated phasic GABA inhibition in the peri-infarct cortex, thereby promoting network excitability and stroke recovery. These beneficial effects depended on GAT-1, a GABA transporter regulating both tonic and phasic GABA signaling, as EE positively regulated GAT-1 expression, trafficking, and function. Furthermore, GAT-1 was necessary for EE-induced network plasticity, including structural neuroplasticity, input synaptic strengthening in the peri-infarct cortex, output synaptic strengthening in the corticospinal tract, and sprouting of uninjured corticospinal axons across the midline into the territory of denervated spinal cord, and functional recovery from stroke. Moreover, restoration of GAT-1 function in the peri-infarct cortex by its overexpression showed similar beneficial effects on stroke recovery as EE exposure.Conclusion: GAT-1 is a key molecular substrate of the effects of EE on network excitability and consequent stroke recovery and can serve as a novel therapeutic target for stroke treatment during the repair phase.

Astroglia and Obsessive Compulsive Disorder.

Obsessive compulsive disorder (OCD) has a prevalence rate of 1-3% in the general population and has been ranked as one of the top ten leading causes of illness-related disability (American Psychiatric Association 2013; Kessler et al. 2005). OCD is characterized by persistent intrusive thoughts (obsessions) and repetitive behaviors (compulsions) (Leckman et al. 1997). There are various OCD-related disorders, including Tourette syndrome (TS), grooming disorders (e.g., skin-picking, trichotillomania), and autism spectrum disorders (ASD) that share considerable overlapping features with OCD (Browne et al. 2014). Although the neurobiological basis of OCD still remains obscure, neuroimaging studies in patients with OCD and OCD-related disorders have consistently identified hyperactivity in orbitofrontal cortex and striatum (Cerliani et al. 2015; Hou et al. 2014; Jung et al. 2017; Neuner et al. 2014). However, the cellular and synaptic abnormalities underlying this hyperactivity are unclear. The most prominent theory regarding the underlying mechanisms of OCD and OCD-related disorders is an increased excitation to inhibition (E/I) ratio due to increased glutamatergic excitation or reduced GABAergic inhibition (Albin and Mink 2006; Rubenstein and Merzenich 2003; Wu et al. 2012). A proper E/I ratio is achieved by factors expressed in neuron and glia. In astrocytes, both the glutamate transporter GLT1 and GABA transporter GAT-3 are critical for regulating the E/I balance (Aida et al. 2015; Aizawa et al. 2020; Boddum et al. 2016; Cui et al. 2014; Kersanté et al. 2013; Kiryk et al. 2008; Matos et al. 2018; Scimemi 2014; Sugimoto et al. 2018; Sugiyama et al. 2017; Tanaka et al. 1997; Zhao et al. 2018). Although astrocyte dysfunction has not been directly explored in OCD patients, several animal studies have found that astrocytes are involved in the pathophysiology of OCD. In this chapter, I highlight recent studies in which astrocyte dysfunction contributed to E/I imbalance, leading to pathological repetitive behaviors shared between patients with OCD, TS, and ASD.

Maternal GABAergic and GnRH/corazonin pathway modulates egg diapause phenotype of the silkworm Bombyx mori

Diapause represents a major developmental switch in insects and is a seasonal adaptation that evolved as a specific subtype of dormancy in most insect species to ensure survival under unfavorable environmental conditions and synchronize populations. However, the hierarchical relationship of the molecular mechanisms involved in the perception of environmental signals to integration in morphological, physiological, behavioral, and reproductive responses remains unclear. In the bivoltine strain of the silkworm Bombyx mori, embryonic diapause is induced transgenerationally as a maternal effect. Progeny diapause is determined by the environmental temperature during embryonic development of the mother. Here, we show that the hierarchical pathway consists of a γ-aminobutyric acid (GABA)ergic and corazonin signaling system modulating progeny diapause induction via diapause hormone release, which may be finely tuned by the temperature-dependent expression of plasma membrane GABA transporter. Furthermore, this signaling pathway possesses similar features to the gonadotropin-releasing hormone (GnRH) signaling system for seasonal reproductive plasticity in vertebrates.