Gamma-aminobutyric Acid Function Research Articles

GABA (gamma-aminobutyric acid) levels in dorsal anterior cingulate cortex are negatively associated with food motivation in a pediatric sample

Food motivation varies between individuals, affecting body weight and risk for eating disorders. Prior neuroimaging studies in youth and adults have revealed functional and structural alterations in the anterior cingulate cortex [ACC] in those with obesity and disordered eating but have not investigated their neurochemical underpinnings. In a sample of 37 children aged 4 to 13 years old, we used Magnetic Resonance Spectroscopy [MRS] to assess levels of γ-aminobutyric acid [GABA] – the major inhibitory neurotransmitter in the human brain – quantified relative to creatine in a 27-ml voxel including the dorsal ACC. We used the CEBQ to assess trait food motivation. In analyses adjusting for age, lower GABA+/Cr levels in the dorsal ACC were associated with higher trait enjoyment of food. Higher enjoyment of food scores were in turn associated with higher energy intake during an ad libitum test meal and during a postprandial task assessing intake in the absence of hunger, and higher body weight. Our results indicate a role for GABA function in the dorsal ACC in determining individual variation in food motivation in children.

Interplay between microbial-derived GABA and host GABA receptor signaling collectively influence the tumorigenic function of GABA in colon cancer.

Although classically recognized as a neurotransmitter, gamma aminobutyric acid (GABA) has also been identified in colonic tumors. Moreover, the gut microbiome represents another potential source of GABA. Both GABAA and GABAB receptors have been implicated in contributing to the effects of GABA in colorectal cancer, with both pro- and anti-tumorigenic functions identified. However, their subunit composition is often overlooked. Studies to date have not addressed whether the GABA-producing potential of the microbiome changes over the course of colon tumor development or whether receptor subunit expression patterns are altered in colon cancer. Therefore, we investigated the clusters of orthologous group frequencies of glutamate decarboxylase (GAD) in feces from two murine models of colon cancer and found that the frequency of microbial GAD was significantly decreased early in the tumorigenic process. We also determined that microbial-derived GABA inhibited proliferation of colon cancer cells invitro and that this effect of GABA on SW480 cells involved both GABAA and GABAB receptors. GABA also inhibited prostaglandin E2 (PGE2)-induced proliferation and interleukin-6 (IL-6) expression in these cells. Gene expression correlations were assessed using the "Cancer Exploration" suite of the TIMER2.0 web tool and identified that GABA receptor subunits were differentially expressed in human colon cancer. Moreover, GABAA receptor subunits were predominantly positively associated with PGE2 synthase, cyclooxygenase-2 and IL-6. Collectively, these data demonstrate decreased potential of the microbiome to produce GABA during tumorigenesis, a novel anti-tumorigenic pathway for GABA, and that GABA receptor subunit expression adds a further layer of complexity to GABAergic signaling in colon cancer.

GABA and Executive functions in ASD

Gamma-aminobutyric acid (GABA) is a neurotransmitter critically involved in various psychological and behavioral processes. This review highlights the impact of GABAergic dysfunction within specific brain regions on a range of mental disorders, executive processes, self-control, and behavioral regulation.Reductions in GABAergic neurotransmission within distinct brain regions have been consistently associated with several mental health conditions. Within the context of anxiety disorders, depression, and post-traumatic stress disorder (PTSD), alterations in GABAergic function contribute to symptomatology. GABA plays a pivotal role in anxiety and mood regulation, with its impairment linked to symptoms of depression and mood disorders. Dysfunctional GABAergic transmission also contributes to fear dysregulation and features of PTSD. In terms of executive functions, GABAergic neurotransmission affects working memory, attentional control, and inhibitory regulation. Changes in GABA levels have been linked to decision-making abilities, impulsivity, and attention deficits, especially in conditions like attention deficit hyperactivity disorder (ADHD). GABA further plays a crucial role in self-control mechanisms by regulating impulsivity and prefrontal cortex functionality. Substance use disorders, often accompanied by impaired self-control, are significantly influenced by GABAergic system changes. Additionally, GABA's involvement in anxiety and emotional management affects the control of emotional responses. Behavioral control is modulated by GABAergic action in motor circuitry, where GABA provides inhibitory control for motor actions. Spontaneity, aggression, and stress are influenced by GABAergic dysfunction, impacting behavioral control. In the realm of attentional control, GABAergic neurotransmission influences selective attention and sensory salience, maintaining a balance between neural stimulation and inhibition. The study also explores executive function deficits in individuals with Autism Spectrum Disorder (ASD) in relation to GABA levels within specific brain regions. Moreover, GABA and its network connectivity contribute to individual variations in sensory responsiveness, emphasizing the dynamic role of GABA in the phenotypic heterogeneity of ASD. In summary, this research underscores the critical role of GABAergic neurotransmission within specific brain regions in various psychological disorders, executive functions, self-control, behavioral regulation, and attentional processes. Understanding the directional influence of GABAergic changes on behavior and mental health conditions can pave the way for more targeted interventions in neuropsychiatric disorders.

MicroRNA-502-3p regulates GABAergic synapse function in hippocampal neurons.

JOURNAL/nrgr/04.03/01300535-202412000-00026/figure1/v/2024-04-08T165401Z/r/image-tiff Gamma-aminobutyric acid (GABA)ergic neurons, the most abundant inhibitory neurons in the human brain, have been found to be reduced in many neurological disorders, including Alzheimer's disease and Alzheimer's disease-related dementia. Our previous study identified the upregulation of microRNA-502-3p (miR-502-3p) and downregulation of GABA type A receptor subunit α-1 in Alzheimer's disease synapses. This study investigated a new molecular relationship between miR-502-3p and GABAergic synapse function. In vitro studies were performed using the mouse hippocampal neuronal cell line HT22 and miR-502-3p agomiRs and antagomiRs. In silico analysis identified multiple binding sites of miR-502-3p at GABA type A receptor subunit α-1 mRNA. Luciferase assay confirmed that miR-502-3p targets the GABA type A receptor subunit α-1 gene and suppresses the luciferase activity. Furthermore, quantitative reverse transcription-polymerase chain reaction, miRNA in situ hybridization, immunoblotting, and immunostaining analysis confirmed that overexpression of miR-502-3p reduced the GABA type A receptor subunit α-1 level, while suppression of miR-502-3p increased the level of GABA type A receptor subunit α-1 protein. Notably, as a result of the overexpression of miR-502-3p, cell viability was found to be reduced, and the population of necrotic cells was found to be increased. The whole cell patch-clamp analysis of human-GABA receptor A-α1/β3/γ2L human embryonic kidney (HEK) recombinant cell line also showed that overexpression of miR-502-3p reduced the GABA current and overall GABA function, suggesting a negative correlation between miR-502-3p levels and GABAergic synapse function. Additionally, the levels of proteins associated with Alzheimer's disease were high with miR-502-3p overexpression and reduced with miR-502-3p suppression. The present study provides insight into the molecular mechanism of regulation of GABAergic synapses by miR-502-3p. We propose that micro-RNA, in particular miR-502-3p, could be a potential therapeutic target to modulate GABAergic synapse function in neurological disorders, including Alzheimer's disease and Alzheimer's disease-related dementia.

GABA, Aging and Exercise: Functional and Intervention Considerations.

The global growth of an aging population is expected to coincide with an increase in aging-related pathologies, including those related to brain health. Thus, the potential for accelerated cognitive health declines due to adverse aging is expected to have profound social and economic implications. However, the progression to pathological conditions is not an inevitable part of aging. In fact, engaging in activities that improve cardiovascular fitness appears to be a means that offers the benefits of maintaining and/or improving cognitive health in older age. However, to date, the underlying mechanisms responsible for improved central nervous system health and function with exercise are not yet fully elucidated. Consequently, there is considerable interest in studies aimed at understanding the neurophysiological benefits of exercise on aging. One such area of study suggests that the improvements in brain health via exercise are, in part, driven by the recovery of inhibitory processes related to the neurotransmitter gamma-aminobutyric acid (GABA). In the present review, we highlight the opposing effects of aging and exercise on cortical inhibition and the GABAergic system's functional integrity. We highlight these changes in GABA function by reviewing work with in vivo measurements: transcranial magnetic stimulation (TMS) and magnetic resonance spectroscopy (MRS). We also highlight recent and significant technological and methodological advances in assessing the GABAergic system's integrity with TMS and MRS. We then discuss potential future research directions to inform mechanistic GABA study targeted to improve health and function in aging. We conclude by highlighting the significance of understanding the effects of exercise and aging, its influence on GABA levels, and why a better understanding is crucial to allow for more targeted and effective interventions aimed to ultimately improve age-related decline in aging.

Biosynthesis of Gamma-Aminobutyric Acid (GABA) by Lactiplantibacillus plantarum in Fermented Food Production.

In recent decades, given the important role of gamma-aminobutyric acid (GABA) in human health, scientists have paid great attention to the enrichment of this chemical compound in food using various methods, including microbial fermentation. Moreover, GABA or GABA-rich products have been successfully commercialized as food additives or functional dietary supplements. Several microorganisms can produce GABA, including bacteria, fungi, and yeasts. Among GABA-producing microorganisms, lactic acid bacteria (LAB) are commonly used in the production of many fermented foods. Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a LAB species that has a long history of natural occurrence and safe use in a wide variety of fermented foods and beverages. Within this species, some strains possess not only good pro-technological properties but also the ability to produce various bioactive compounds, including GABA. The present review aims, after a preliminary excursus on the function and biosynthesis of GABA, to provide an overview of the current uses of microorganisms and, in particular, of L. plantarum in the production of GABA, with a detailed focus on fermented foods. The results of the studies reported in this review highlight that the selection of new probiotic strains of L. plantarum with the ability to synthesize GABA may offer concrete opportunities for the design of new functional foods.

Gamma-Aminobutyric Acid Signaling in Damage Response, Metabolism, and Disease

Gamma-aminobutyric acid (GABA) plays a crucial role in signal transduction and can function as a neurotransmitter. Although many studies have been conducted on GABA in brain biology, the cellular function and physiological relevance of GABA in other metabolic organs remain unclear. Here, we will discuss recent advances in understanding GABA metabolism with a focus on its biosynthesis and cellular functions in other organs. The mechanisms of GABA in liver biology and disease have revealed new ways to link the biosynthesis of GABA to its cellular function. By reviewing what is known about the distinct effects of GABA and GABA-mediated metabolites in physiological pathways, we provide a framework for understanding newly identified targets regulating the damage response, with implications for ameliorating metabolic diseases. With this review, we suggest that further research is necessary to develop GABA's beneficial and toxic effects on metabolic disease progression.

The role of GABA in islet function.

Gamma aminobutyric acid (GABA) is a non-proteinogenic amino acid and neurotransmitter that is produced in the islet at levels as high as in the brain. GABA is synthesized by the enzyme glutamic acid decarboxylase (GAD), of which the 65 kDa isoform (GAD65) is a major autoantigen in type 1 diabetes. Originally described to be released via synaptic-like microvesicles or from insulin secretory vesicles, beta cells are now understood to release substantial quantities of GABA directly from the cytosol via volume-regulated anion channels (VRAC). Once released, GABA influences the activity of multiple islet cell types through ionotropic GABAA receptors and metabotropic GABAB receptors. GABA also interfaces with cellular metabolism and ATP production via the GABA shunt pathway. Beta cells become depleted of GABA in type 1 diabetes (in remaining beta cells) and type 2 diabetes, suggesting that loss or reduction of islet GABA correlates with diabetes pathogenesis and may contribute to dysfunction of alpha, beta, and delta cells in diabetic individuals. While the function of GABA in the nervous system is well-understood, the description of the islet GABA system is clouded by differing reports describing multiple secretion pathways and effector functions. This review will discuss and attempt to unify the major experimental results from over 40 years of literature characterizing the role of GABA in the islet.

The immuno-behavioural covariation associated with the treatment response to bumetanide in young children with autism spectrum disorder

Bumetanide, a drug being studied in autism spectrum disorder (ASD) may act to restore gamma-aminobutyric acid (GABA) function, which may be modulated by the immune system. However, the interaction between bumetanide and the immune system remains unclear. Seventy-nine children with ASD were analysed from a longitudinal sample for a 3-month treatment of bumetanide. The covariation between symptom improvements and cytokine changes was calculated and validated by sparse canonical correlation analysis. Response patterns to bumetanide were revealed by clustering analysis. Five classifiers were used to test whether including the baseline information of cytokines could improve the prediction of the response patterns using an independent test sample. An immuno-behavioural covariation was identified between symptom improvements in the Childhood Autism Rating Scale (CARS) and the cytokine changes among interferon (IFN)-γ, monokine induced by gamma interferon and IFN-α2. Using this covariation, three groups with distinct response patterns to bumetanide were detected, including the best (21.5%, n = 17; Hedge’s g of improvement in CARS = 2.16), the least (22.8%, n = 18; g = 1.02) and the medium (55.7%, n = 44; g = 1.42) responding groups. Including the cytokine levels significantly improved the prediction of the best responding group before treatment (the best area under the curve, AUC = 0.832) compared with the model without the cytokine levels (95% confidence interval of the improvement in AUC was [0.287, 0.319]). Cytokine measurements can help in identifying possible responders to bumetanide in ASD children, suggesting that immune responses may interact with the mechanism of action of bumetanide to enhance the GABA function in ASD.

Total GABA level in human auditory cortex is associated with speech-in-noise understanding in older age

Speech-in-noise (SIN) understanding often becomes difficult for older adults because of impaired hearing and aging-related changes in central auditory processing. Central auditory processing depends on a fine balance between excitatory and inhibitory neural mechanisms, which may be upset in older age by a change in the level of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). In this study, we used MEGA-PRESS magnetic resonance spectroscopy (MRS) to estimate GABA levels in both the left and right auditory cortices of young and older adults. We found that total auditory GABA levels were lower in older compared to young adults. To understand the relationship between GABA and hearing function, we correlated GABA levels with hearing loss and SIN performance. In older adults, the GABA level in the right auditory cortex was correlated with age and SIN performance. The relationship between chronological age and SIN loss was partially mediated by the GABA level in the right auditory cortex. These findings support the hypothesis that inhibitory mechanisms in the auditory system are reduced in aging, and this reduction relates to functional impairments.

Characterizing the transport and utilization of the neurotransmitter GABA in the bacterial pathogen Brucella abortus.

The neurotransmitter gamma-aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in the human brain; however, it is becoming more evident that this non-proteinogenic amino acid plays multiple physiological roles in biology. In the present study, the transport and function of GABA is studied in the highly infectious intracellular bacterium Brucella abortus. The data show that 3H-GABA is imported by B. abortus under nutrient limiting conditions and that the small RNAs AbcR1 and AbcR2 negatively regulate this transport. A specific transport system, gts, is responsible for the transport of GABA as determined by measuring 3H-GABA transport in isogenic deletion strains of known AbcR1/2 regulatory targets; however, this locus is unnecessary for Brucella infection in BALB/c mice. Similar assays revealed that 3H-GABA transport is uninhibited by the 20 standard proteinogenic amino acids, representing preference for the transport of 3H-GABA. Metabolic studies did not show any potential metabolic utilization of GABA by B. abortus as a carbon or nitrogen source, and RNA sequencing analysis revealed limited transcriptional differences between B. abortus 2308 with or without exposure to GABA. While this study provides evidence for GABA transport by B. abortus, questions remain as to why and when this transport is utilized during Brucella pathogenesis.

Associations Between Cognitive Function and Levels of Glutamatergic Metabolites and Gamma-Aminobutyric Acid in Antipsychotic-Naïve Patients With Schizophrenia or Psychosis

BackgroundAbnormal glutamate and GABA (gamma-aminobutyric acid) levels have been found in the early phase of schizophrenia and may underlie cognitive deficits. However, the association between cognitive function and levels of glutamatergic metabolites and GABA has not been investigated in a large group of antipsychotic-naïve patients. MethodsIn total, 56 antipsychotic-naïve patients with schizophrenia or psychotic disorder and 51 healthy control subjects underwent magnetic resonance spectroscopy to measure glutamate, glutamate+glutamine (Glx), and GABA levels in dorsal anterior cingulate cortex (ACC) and glutamate and Glx levels in left thalamus. The cognitive domains of attention, working memory, and IQ were assessed. ResultsThe whole group of antipsychotic-naïve patients had lower levels of GABA in dorsal ACC (p = .03), and the subgroup of patients with a schizophrenia diagnosis had higher glutamate levels in thalamus (p = .01), but Glx levels in dorsal ACC and thalamus did not differ between groups. Glx levels in dorsal ACC were positively associated with working memory (logarithmically transformed: b = −.016 [higher score indicates worse performance], p = .005) and attention (b = .056, p = .035) in both patients and healthy control subjects, although the association with attention did not survive adjustment for multiple comparisons. ConclusionsThe findings suggest a positive association between glutamatergic metabolites and cognitive function that do not differ between patients and healthy control subjects. Moreover, our data indicate that decreased GABAergic levels in dorsal ACC are involved in schizophrenia and psychotic disorder, whereas increased glutamate levels in thalamus seem to be implicated in schizophrenia pathophysiology. The findings imply that first-episode patients with cognitive deficits may gain from glutamate-modulating compounds.

O6.3. ASSOCIATIONS BETWEEN COGNITIVE FUNCTION AND CORTICAL LEVELS OF GLUTAMATE AND GABA IN ANTIPSYCHOTIC-NAïVE PATIENTS WITH SCHIZOPHRENIA OR PSYCHOSIS

BackgroundDysfunctional glutamatergic and gamma-aminobutyric acid (GABA)ergic neurotransmission may be part of the schizophrenia pathophysiology and underlie cognitive deficits. Abnormal levels of glutamate and GABA have been found in patients with first-episode psychosis or schizophrenia, and studies of mainly medicated patients have reported correlations between cortical glutamate and GABA levels and cognitive performance. However, the association between metabolites and cognitive deficits may be altered by treatment. Therefore, we investigated if glutamate and GABA levels in dorsal anterior cingulate cortex were associated with cognitive function in a large group of antipsychotic-naïve patients compared with matched healthy controls and tested the hypothesis that cognitive deficits in patients are related to altered levels of glutamate and GABA.MethodsWe recruited 56 antipsychotic-naïve patients with schizophrenia or psychotic disorder and 51 healthy controls matched for age, sex, and parental education. Magnetic resonance spectroscopy was used to measure glutamate and GABA levels in dorsal anterior cingulate cortex (ACC) on a 3T scanner. The cognitive domains attention (outcome was rapid visual information processing A’ (RVP A’)) and working memory (outcome was spatial working memory (SWM) strategy) were assessed with the Cambridge Neuropsychological Test Automated Battery, and premorbid intelligence estimated with the Danish Adult Reading Test (DART) (outcome was number of words correctly pronounced). A multivariate linear regression model was used to evaluate if levels of glutamate and GABA were different in patients compared with healthy controls, and thereafter to test if glutamate and GABA levels were associated with cognitive performance in the two groups (significant main effect) and if the association differed (significant interaction). SWM strategy score were logarithmically transformed because of non-normality.ResultsLevels of GABA in dorsal ACC were lower in the antipsychotic-naïve patients compared with healthy controls (SCZ: 2.24±0.35; HC: 2.40±0.33, p=0.03), but glutamate levels did not differ significantly between patients and healthy controls (SCZ: 10.75±1.45; HC: 10.91±1.17, p=0.54). Patients performed significantly worse than healthy controls in tests of attention (mean RVP A’ score SCZ: 0.89±0.05; HC: 0.94±0.04, p<0.001) and premorbid IQ (mean DART score SCZ: 17.4±6.5; HC: 21.5±5.3, p=0.001), whereas groups did not differ significantly in SWM strategy score (Median score SCZ: 27.0 (22.0–32.0); HC: 23.0 (19.0–30.0), p=0.18). Higher levels of glutamate were associated with better performance in tests of attention (b=0.01, p=0.016) and SWM (b=-0.02, p=0.008, higher score indicates worse performance) in both patients and healthy controls. The association between cognitive performance and glutamate did not differ significantly between the two groups (both interactions insignificant).There were no significant associations between cognitive function and levels of GABA in dorsal ACC.DiscussionThis is the largest study of antipsychotic-naïve patients to date to investigate the association between cortical glutamate and GABA levels and cognitive function. We found no group differences in levels of glutamate, but lower GABA levels, which indicates reduced GABAergic neurotransmission in dorsal ACC in the pathophysiology of schizophrenia and psychosis.Higher levels of glutamate in dorsal ACC were associated with better cognitive function. However, glutamate levels did not explain the differences in cognitive performance between patients and healthy controls, indicating that other neurotransmitters are important as well.

A Brief Review on the Non-protein Amino Acid, Gamma-amino Butyric Acid (GABA): Its Production and Role in Microbes.

Gamma-Aminobutyric acid (GABA) is a non-protein amino acid widely distributed in nature. It is produced through irreversible α-decarboxylation of glutamate by enzyme glutamate decarboxylase (GAD). GABA and GAD have been found in plants, animals, and microorganisms. GABA is distributed throughout the human body and it is involved in the regulation of cardiovascular conditions such as blood pressure and heart rate, and plays a role in the reduction of anxiety and pain. Although researchers had produced GABA by chemical method earlier it became less acceptable as it pollutes the environment. Researchers now use a more promising microbial method for the production of GABA. In the drug and food industry, demand for GABA is immense. So, large scale conversion of GABA by microbes has got much attention. So this review focuses on the isolation source, production, and functions of GABA in the microbial system. We also summarize the mechanism of action of GABA and its shunt pathway.

Axis elongation during Xenopus tail-bud stage is regulated by GABA expressed in the anterior-to-mid neural tube.

The receptors of gamma-aminobutyric acid (GABA), which is a well-known neurotransmitter, are expressed in the anterior-to-mid neural tube at an early stage of Xenopus development, but there has been no report on the role of GABA in the presumptive central nervous system. Therefore, we tried to reveal the function of GABA for Xenopus early embryogenesis. We first confirmed that the region expressing a gene encoding glutamate decarboxylase 1 (gad1), which is an enzyme that catalyzes the decarboxylation of L-glutamate to GABA, overlapped with that of several genes encoding GABA receptors (gabr) in the neural tube. Metabolome analysis of culture medium of dorsal tail-bud explants containing the neural tube region of tail-bud stage embryos also revealed that GABA was expressed at this stage. Then, we examined the treatment of pentylenetetrazole (PTZ) and picrotoxin (PTX), which are known as inhibitors of GABA receptors (GABA-R), on the early stages of Xenopus embryogenesis, and found that axis elongation in the tail-bud was inhibited by both treatments, and these phenotypic effects were rescued by co-treatment with GABA. Moreover, our spatial- and temporal-specific inhibitor treatments revealed that the gabr- and gad1-overlapped region, which presents at the anterior-to-mid neural tube during the tail-bud stages, was much more sensitive to PTZ and thus caused severe inhibition of axis elongation. Taken together, our results indicate that the small ligand molecule GABA functions as a regulator to induce the axis elongation event in the tail-bud during early embryogenesis via direct stimulation of the neural tube and indirect stimulation of the surrounding area.

The GABAergic System: An Overview of Physiology, Physiopathology and Therapeutics

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the central nervous system, where it is widely distributed. GABA has an important role in neurodevelopment, and depending on the period of development, its action can be excitatory or inhibitory. In prenatal stages, GABA is excitatory, and in the adult stage, GABA acquires an inhibitory function in the nervous system and modulates the function of other organs and systems including the endocrine system and the immune system. Disorders in the function of GABA are responsible for various pathologies, both neurological and non-neurological, and include epilepsy, anxiety, depression, schizophrenia, endocrine disorders and immunological disorders. In the present narrative review, we show that the activity of GABA depends on the synthesis, degradation, membrane transport and the presence of specific GABA receptors, present in both nervous tissue and non-neural tissue. We describe general aspects of the physiology, physiopathology, and pharmacotherapeutics of the GABA system, and finally, we emphasize that although there are multiple GABAergic therapeutic options, more research is required into the GABA system since future applications may be broad.

Ginsenoside Rb1 Ameliorates Working Memory Deficits Via Regulation of Prefrontal Cortical Gabaergic Transmission in MPTP-Treated Mice

Background: Working memory impairment is a common non-motor symptom in the progression of Parkinson's disease (PD). Ginsenoside Rb1, an extract from the Ginseng root, has been demonstrated to ameliorate motor deficits and prevent dopaminergic neuron death in PD. However, whether Rb1 can attenuate the PD-associated deficits in working memory and its underlying mechanism of action are still unclear. Methods: Behavioral tests were used to examine the effect of Rb1 on the working memory deficits in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Gamma-aminobutyric acid (GABA)-chemical exchange saturation transfer (CEST) magnetic resonance imaging and electrophysiology were used to identify the effect of Rb1 on the GABA content and GABAergic synaptic transmission in the prefrontal cortex. Immunofluorescence and western blotting were used to explore the expression of the different GABA receptors. Findings: We found that Rb1 attenuated the impairment in spatial working memory in the MPTP mouse model of PD, and this neuroprotective mechanism involved the regulation of prefrontal cortical GABAergic content and transmission. We demonstrated that Rb1 increased GABA content in the prefrontal cortex, and Rb1 prevented the MPTP-induced decrease of presynaptic GABA release and postsynaptic GABA receptor expression and function. Furthermore, Rb1's promotion of GABA current may be associated with the regulation of GABAA receptor trafficking from the postsynaptic density to the membrane, as well as with the modulation of postsynaptic GABAB receptors to enhance GABAA receptor function. Interpretation: Rb1 may serve as a potential drug candidate for the treatment of cognitive impairments in PD. Funding: The National Natural Science Foundation of China (No. 81704130 to YZ, No. 81774377 and No. 81373999 to LW), the Natural Science Foundation of Fujian Province of China (No. 2017J05139 to YZ), the Natural Science Foundation of Guangdong Province of China (No. 2017A030310643 to YZ), the China Postdoctoral Science Foundation (No. 2016M590598 to YZ), the National Key Research and Development Program of China (No. 2016YFC1305903 to LW), and the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-13-0505 to LW). Declaration of Interest: The authors declare no conflicts of interest. Ethical Approval: All experiments were conducted according to the National Institute of Health guidelines on the care and use of animals (NIH Publications No. 8023, revised 1978) and approved by the Institutional Animal Care and Use Committee of Guangzhou Medical University.

Long-range gamma phase synchronization as a compensatory strategy during working memory in high-performing patients with schizophrenia

ABSTRACTWorking memory deficits in schizophrenia may be associated with impairments in the integration of neural activity across a distributed network of cortical areas. However, evaluation of the contribution of this integration to working memory impairments in patients is severely confounded by behavioral performance. In the present multidimensional-neuroimaging study, measures of neural oscillations at baseline and during a working memory task, baseline gamma-aminobutyric acid (GABA) level in the left dorsolateral prefrontal cortex (DLPFC), and behavioral performance were obtained. Controlling behavioral performance by recruiting only “high-performing” patients with schizophrenia, we investigated whether the strength of cross-area communications differs between patients with schizophrenia and healthy participants under accurate and equivalent behavioral performance. Results of phase-locking value indicated that these high-performing patients recruited significantly more between frontal and occipital regions in the left hemisphere, t(13) = −2.16, p = .05, Cohen’s d = −1.20, and between frontal and temporal regions in the right hemisphere, t(13) = −2.63, p = .02, Cohen’s d = −1.46. These cross-area communication patterns may be associated with visuoverbal and visuospatial working memory networks of the left and right hemispheres, respectively. Moreover, correlations of patient’s cross-area communication with in vivo GABA levels of the left DLPFC revealed a significant positive relationship (r = .77, p = .04), demonstrating that the critical role of GABA functions in gamma band oscillations may go beyond local neuronal assemblies in the left DLPFC. Altogether, these exploratory findings point to the heterogeneity among schizophrenia patients and highlight the notion that high-performing patients may engage in potential compensatory mechanisms and may represent a subgroup of patients that may be categorically or dimensionally divergent in psychopathology.

γ-Aminobutyric Acid Is Synthesized and Released by the Endothelium: Potential Implications.

Gamma aminobutyric acid (GABA), a neurotransmitter of the central nervous system, is found in the systemic circulation of humans at a concentration between 0.5 and 3 μmol/L. However, the potential source of circulating GABA and its significance on the vascular system remains unknown. We hypothesized that endothelial cells (ECs) may synthesize and release GABA to modulate some functions in the EC and after its release into the circulation. To assess whether GABA is synthesized and released by the EC and its potential functions. Utilizing the human umbilical vein ECs and aortic ECs, we demonstrated for the first time that ECs synthesize and release GABA from [1-(14)C]glutamate. Localization of GABA and the presence of the GABA-synthesizing enzyme, glutamic acid decarboxylase in EC were confirmed by immunostaining and immunoblot analysis, respectively. The presence of GABA was further confirmed by immunohistochemistry in the EC lining the human coronary vessel. EC-derived GABA regulated the key mechanisms of ATP synthesis, fatty acid, and pyruvate oxidation in EC. GABA protected EC by inhibiting the reactive oxygen species generation and prevented monocyte adhesion by attenuating vascular cell adhesion molecule -1 and monocyte chemoattractant protein-1 expressions. GABA had no relaxing effect on rat aortic rings. GABA exhibited a dose-dependent fall in blood pressure. However, the fall in BP was abolished after pretreatment with pentolinium. Our findings indicate novel potential functions of endothelium-derived GABA.

GABA Signaling and Neuroactive Steroids in Adrenal Medullary Chromaffin Cells.

Gamma-aminobutyric acid (GABA) is produced not only in the brain, but also in endocrine cells by the two isoforms of glutamic acid decarboxylase (GAD), GAD65 and GAD67. In rat adrenal medullary chromaffin cells only GAD67 is expressed, and GABA is stored in large dense core vesicles (LDCVs), but not synaptic-like microvesicles (SLMVs). The α3β2/3γ2 complex represents the majority of GABAA receptors expressed in rat and guinea pig chromaffin cells, whereas PC12 cells, an immortalized rat chromaffin cell line, express the α1 subunit as well as the α3. The expression of α3, but not α1, in PC12 cells is enhanced by glucocorticoid activity, which may be mediated by both the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). GABA has two actions mediated by GABAA receptors in chromaffin cells: it induces catecholamine secretion by itself and produces an inhibition of synaptically evoked secretion by a shunt effect. Allopregnanolone, a neuroactive steroid which is secreted from the adrenal cortex, produces a marked facilitation of GABAA receptor channel activity. Since there are no GABAergic nerve fibers in the adrenal medulla, GABA may function as a para/autocrine factor in the chromaffin cells. This function of GABA may be facilitated by expression of the immature isoforms of GAD and GABAA receptors and the lack of expression of plasma membrane GABA transporters (GATs). In this review, we will consider how the para/autocrine function of GABA is achieved, focusing on the structural and molecular mechanisms for GABA signaling.