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?-Amino-butyric acid (GABA) receptor subunit and transporter expression in the gonad and liver of the fathead minnow (Pimephales promelas).  


?-Amino-butyric acid (GABA) is the major inhibitory neurotransmitter in the vertebrate central nervous system. GABA receptors and synthesizing enzymes have also been localized to peripheral tissues including the liver, oviduct, uterus and ovary of mammals but the distribution and role of GABA in peripheral tissues of fish has not been fully investigated. The objectives of this study were to (1) determine if mRNA encoding GABA synthesizing enzymes (glutamic acid decarboxylase 65 and 67; gad65 and gad67), GABA transporters, and GABAA receptor subunits are localized to liver and gonad of fathead minnow (Pimephales promelas) (FHM) (2) investigate the effects of GABA on ovarian 17?-estradiol (E2) production, and (3) measure transcript responses in the ovary after in vitro incubation to GABA. Real-time PCR assays were developed for gad65, gad67, vesicular GABA transporter (vgat) and GABA transporter 1 (gat1), and select GABAA receptor subunits (gabra1, gabra5, gabrb1, gabrb2, gabrg1, gabrg2). All transcripts were localized to the brain as expected; however transcripts were also detected in the liver, ovary, and testis of FHMs. In the female liver, gad65 mRNA was significantly higher in expression compared to the male liver. Transcripts for gad67 were the highest in the brain>gonad>liver and in the gonads, gad67 was significantly higher in expression than gad65 mRNA. In the liver and gonad, the relative abundance of the subunits followed a general trend of gabrb1>gabrb2=gabrg1=gabrg2>gabra1=gabra5. To explore the effects of GABA in the ovary, tissue explants from reproductive female FHMs were treated with GABA (10(-10), 10(-8) and 10(-6)M) for 12h. GABA had no significant effect on 17?-estradiol production or on mRNA abundance for genes involved in ovarian steroidogenesis (e.g., 11?hsd, cyp17, cyp19a). There was a significant decrease in estrogen receptor 2a (esr2a) mRNA with 10(-10)M GABA. This study begins to investigate the GABA system in non-neural tissues of teleost fish and addresses the broader topic regarding the peripheral roles of neurotransmitters. PMID:23672824

Biggs, Katie; Seidel, Jason S; Wilson, Alex; Martyniuk, Christopher J



Gamma-amino butyric acid (GABA) prevents the induction of nicotinic receptor-regulated signaling by chronic ethanol in pancreatic cancer cells and normal duct epithelia  

PubMed Central

Pancreatic cancer has a high mortality rate and alcoholism is a risk factor independent of smoking. We have shown that nicotinic acetylcholine receptors (nAChRs) regulate pancreatic ductal epithelia and pancreatic ductal adenocarcinoma (PDAC) cells in an autocrine fashion by stimulating their production of the stress neurotransmitters noradrenaline and adrenaline that signal through beta-adrenergic receptors (?-ARs). Our current study has investigated the modulation of this autocrine regulatory loop by chronic ethanol and explored the potential prevention of these effects by ?-amino butyric acid (GABA). Using MTT assays, cell migration assays, western blotting, immunoassays, and gene knockdown of individual nAChRs in two PDAC cell lines and in immortalized human pancreatic duct epithelial cells, our data show that treatment for seven days with ethanol induced the protein expression and sensitivity of nAChRs ?3, ?5 and ?7 resulting in increased production of noradrenaline and adrenaline which drive proliferation and migration via cAMP-dependent signaling downstream of ?-ARs. Treatment with GABA prevented all of these responses to chronic ethanol, reducing cell proliferation and migration below base levels in untreated cells. Our findings suggest that alcoholism induces multiple cAMP-dependent PDAC stimulating signaling pathways by up-regulating the protein expression and sensitivity of nAChRs that regulate stress neurotransmitter production. Moreover, our data identify GABA as a promising agent for the prevention of PDAC in individuals at risk due to chronic alcohol consumption.

Al-Wadei, Mohammed H.; Al-Wadei, Hussein A.N.; Schuller, Hildegard M.



Production of ?-Amino Butyric Acid in Tea Leaves wit Treatment of Lactic Acid Bacteria  

NASA Astrophysics Data System (ADS)

Lactic acid bacteria was searched for producing termented tea that contained a lot of ?-amino butyric acid(GABA). Also examined were the growth condition, GABA production and changes in catechin contents in the tea leaves. Lactobacillus brevis L12 was found to be suitable for the production of fermented tea since it gave as much GABA as gabaron tea when tea leaves being suspended with water at 10% and incubated for 4 days at 25°C. The amount of GABA produced was more than calculated based upon the content of glutamic acid in tea leaves. It is probable to assume that glutamate derived from glutamine and theanine is converted into GABA.

Watanabe, Yuko; Hayakawa, Kiyoshi; Ueno, Hiroshi


Effect of application of gamma amino butyric acid at the medial preoptic area on sleep-wakefulness.  


Intracerebral microinjections of gamma amino butyric acid were given bilaterally at the medial preoptic area (mPOA) to determine the possible role of this neurotransmitter in the genesis and regulation of sleep-wakefulness. GABA (50 micrograms/0.2 microliters) when administered through chronically implanted cannulae in free moving rats, did not produce any significant alterations in sleep-wakefulness. This may be attributed either to the non-involvement of GABA at the level of mPOA in the regulation of sleep, or to other factors like the low dose and rapid breakdown of the injected drug. PMID:8550132

Chari, D M; Ramesh, V; John, J; Kumar, V M



Functional Expression of ?-Amino Butyric Acid Transporter 2 in Human and Guinea Pig Airway Epithelium and Smooth Muscle  

PubMed Central

??Amino butyric acid (GABA) is a primary inhibitory neurotransmitter in the central nervous system, and is classically released by fusion of synaptic vesicles with the plasma membrane or by egress via GABA transporters (GATs). Recently, a GABAergic system comprised of GABAA and GABAB receptors has been identified on airway epithelial and smooth muscle cells that regulate mucus secretion and contractile tone of airway smooth muscle (ASM). In addition, the enzyme that synthesizes GABA, glutamic acid decarboxylase, has been identified in airway epithelial cells; however, the mechanism(s) by which this synthesized GABA is released from epithelial intracellular stores is unknown. We questioned whether any of the four known isoforms of GATs are functionally expressed in ASM or epithelial cells. We detected mRNA and protein expression of GAT2 and -4, and isoforms of glutamic acid decarboxylase in native and cultured human ASM and epithelial cells. In contrast, mRNA encoding vesicular GAT (VGAT), the neuronal GABA transporter, was not detected. Functional inhibition of 3H-GABA uptake was demonstrated using GAT2 and GAT4/betaine–GABA transporter 1 (BGT1) inhibitors in both human ASM and epithelial cells. These results demonstrate that two isoforms of GATs, but not VGAT, are expressed in both airway epithelial and smooth muscle cells. They also provide a mechanism by which locally synthesized GABA can be released from these cells into the airway to activate GABAA channels and GABAB receptors, with subsequent autocrine and/or paracrine signaling effects on airway epithelium and ASM.

Zaidi, Sarah; Gallos, George; Yim, Peter D.; Xu, Dingbang; Sonett, Joshua R.; Panettieri, Reynold A.; Gerthoffer, William; Emala, Charles W.



The dominant glutamic acid metabolic flux to produce ?-amino butyric acid over proline in Nicotiana tabacum leaves under water stress relates to its significant role in antioxidant activity.  


?-Amino butyric acid (GABA) and proline play a crucial role in protecting plants during various environmental stresses. Their synthesis is from the common precursor glutamic acid, which is catalyzed by glutamate decarboxylase and ?(1) -pyrroline-5-carboxylate synthetase respectively. However, the dominant pathway under water stress has not yet been established. To explore this, excised tobacco leaves were used to simulate a water-stress condition. The results showed GABA content was much higher than that of proline in leaves under water-deficit and non-water-deficit conditions. Specifically, the amount of GABA significantly increased compared to proline under continuous water loss for 16 h, indicating that GABA biosynthesis is the dominant pathway from glutamic acid metabolism under these conditions. Quantitative reverse transcription polymerase chain reaction and protein Western gel-blot analysis further confirmed this. To explore the function of GABA accumulation, a system producing superoxide anion (O(2) (-) ), peroxide hydrogen (H(2) O(2) ), and singlet oxygen ((1) O(2) ) was employed to investigate the scavenging role on free-radical production. The results demonstrated that the scavenging ability of GABA for O(2) (-) , H(2) O(2) , and (1) O(2) was significantly higher than that of proline. This indicated that GABA acts as an effective osmolyte to reduce the production of reactive oxygen species under water stress. PMID:21564543

Liu, Cuili; Zhao, Li; Yu, Guanghui



Ondansetron reverses anti-hypersensitivity from clonidine in rats following peripheral nerve injury: Role of ?-amino butyric acid in ?2-adrenoceptor and 5-HT3 serotonin receptor analgesia  

PubMed Central

Introduction Monoaminergic pathways, impinging an ?2-adrenoceptors and 5-HT3 serotonin receptors, modulate nociceptive transmission, but their mechanisms and interactions after neuropathic injury are unknown. Here we examine these interactions in rodents after nerve injury. Methods Male Sprague-Dawley rats following L5-L6 spinal nerve ligation (SNL) were used for either behavioral testing, in vivo microdialysis for ?-amino butyric acid (GABA) and acetylcholine release, or synaptosome preparation for GABA release. Results Intrathecal administration of the ?2-adrenoceptor agonist (clonidine) and 5-HT3 receptor agonist (chlorophenylbiguanide) reduced hypersensitivity in SNL rats via GABA receptor-mediated mechanisms. Clonidine increased GABA and acetylcholine release in vivo in the spinal cord of SNL rats but not in normal rats. Clonidine-induced spinal GABA release in SNL rats was blocked by ?2-adrenergic and nicotinic cholinergic antagonists. The 5-HT3 receptor antagonist ondansetron decreased and chlorophenylbiguanide increased spinal GABA release in both normal and SNL rats. In synaptosomes from the spinal dorsal horn of SNL rats, pre-synaptic GABA release was increased by nicotinic agonists and decreased by muscarinic and ?2-adrenergic agonists. Spinally administered ondansetron significantly reduced clonidine-induced anti-hypersensitivity and spinal GABA release in SNL rats. Conclusion These results suggest that spinal GABA contributes to anti-hypersensitivity from intrathecal ?2-adrenergic and 5-HT3 receptor agonists in the neuropathic pain state, that cholinergic neuroplasticity after nerve injury is critical for ?2-adrenoceptor-mediated GABA release, and that blockade of spinal 5-HT3 receptors reduces ?2-adrenoceptor-mediated anti-hypersensitivity via reducing total GABA release.

Hayashida, Ken-ichiro; Kimura, Masafumi; Yoshizumi, Masaru; Hobo, Shotaro; Obata, Hideaki; Eisenach, James C.



Optimization of ?-amino butyric acid production in a newly isolated Lactobacillus brevis.  


An isolate from kimchi, identified as Lactobacillus brevis, accumulated ?-aminobutyric acid (GABA), a major inhibitory neurotransmitter, in the culture medium. Optimal culture conditions for growth of L. brevis and production of GABA were 6 % (w/v) l-glutamic acid, 4 % (w/v) maltose, 2 % (w/v) yeast extract, 1 % (w/v) NaCl, 1 % (w/v) CaCl2, 2 g Tween 80/l, and 0.02 mM pyridoxal 5?-phosphate at initial pH 5.25 and 37 °C. GABA reached 44.4 g/l after 72 h cultivation with a conversion rate 99.7 %, based on the amount (6 %) of l-glutamic acid added. GABA was purified using ion exchange column chromatography with 70 % recovery and 97 % purity. PMID:24078124

Binh, Tran Thi Thanh; Ju, Wan-Taek; Jung, Woo-Jin; Park, Ro-Dong



Post infection application of DL3-amino-butyric acid (BABA) induces multiple forms of resistance against Bremia lactucae in lettuce  

Microsoft Academic Search

DL-3-amino-butyric acid (BABA) induces local and systemic resistance against disease in numerous plant species. In a recent\\u000a study we showed that preventive application of BABA to lettuce (Lactuca sativa) plants induced resistance against downy mildew caused by the oomycete Bremia lactucae by callose encasement of the primary infection structures of the pathogen. Now we show that post-infection application of\\u000a BABA

Yigal Cohen; Avia E. Rubin; Moshe Vaknin



Role of Bicarbonate in the Actions of gamma-aminobutyric acid (Gaba) on Membrane Conductances, Currents, and pH Regulation in Excitable Cells.  

National Technical Information Service (NTIS)

Ion selective microelectrodes and a two or three microelectrode voltage or current clamp were used to examine the effects of inhibitory neurotransmitter Gamma Amino Butyric Acid (GABA) on intracellular pH (pH(i)) extracellular surface pH (pH(s)) intercell...

J. Voipio



Effects of sea anemone ( heteractis magnifica and actinia equina) cytolysins on synaptosomal uptake of gaba and choline  

Microsoft Academic Search

Magnificalysin I and II (HMg I and II) and equinatoxin II (EqTx II) are cytolytic toxins extracted from sea anemones Heteractis magnifica and Actinia equina, respectively. They induced haemolysis in rat red blood cells and inhibited gamma amino butyric acid (GABA) and choline uptake into rat brain synaptosomes. These effects were concentration dependent. The inhibition of GABA and choline uptake

H. E Khoo; J. P. C Lim; C. H Tan



Estradiol alters only GAD67 mRNA levels in ischemic rat brain with no consequent effects on GABA  

Microsoft Academic Search

The present study tested the hypothesis that estradiol reduces tissue infarction after middle cerebral artery occlusion (MCAO) in estradiol-deficient females by augmenting glutamic acid decarboxylase (GAD) expression and thus activity, leading to increases in ?-amino-butyric acid (GABA) tissue levels. Glutamic acid decarboxylase is the principal enzyme for GABA synthesis and has two isoforms, GAD65 and GAD67, which differ in size

Hung-Dong Joh; Robin V Searles; Michael Selmanoff; Nabil J Alkayed; Raymond C Koehler; Patricia D Hurn; Stephanie J Murphy



Co-activation of GABA receptors inhibits the JNK3 apoptotic pathway via the disassembly of the GluR6PSD95-MLK3 signaling module in cerebral ischemic-reperfusion  

Microsoft Academic Search

In this study, we investigated whether the increase of inhibitory ?-amino butyric acid (GABA) signal suppresses the excitatory glutamate signal induced by cerebral ischemia and the underlying mechanisms. In global cerebral ischemia, focal cerebral ischemia and oxygen-glucose deprivation, application of muscimol and baclofen, agonists of GABA(A) receptor and GABA(B) receptor, exerted neuroprotection. The agonists inhibited the increased assembly of the

Dong Han; Quan-Guang Zhang; Yong-Liu; Chong Li; Yan-Yan Zong; Chang-Zhou Yu; Wei Wang; Jing-Zhi Yan; Guang-Yi Zhang



Photorelease of GABA with Visible Light Using an Inorganic Caging Group  

PubMed Central

We describe the selective photorelease of ?-amino butyric acid (GABA) with a novel caged-GABA compound that uses a ruthenium complex as photosensor. This compound (“RuBi-GABA”) can be excited with visible wavelengths, providing greater tissue penetration, less photo-toxicity, and faster photorelease kinetics than currently used UV light-sensitive caged compounds. Using pyramidal neurons from neocortical brain slices, we show that RuBi-GABA uncaging induces GABA-A receptor-mediated responses, has no detectable side effects on endogenous GABAergic and glutamatergic receptors and generates responses with kinetics and spatial resolution comparable to the best caged GABA compounds presently available. Finally, we illustrate two potential applications of RuBi-GABA uncaging: GABA receptor mapping, and optical silencing of neuronal firing.

Rial Verde, Emiliano M.; Zayat, Leonardo; Etchenique, Roberto; Yuste, Rafael



Zinc mediated allylations of chlorosilanes promoted by ultrasound: Synthesis of novel constrained sila amino acids.  


A simple, fast and efficient method for allylation and propargylation of chlorosilanes through zinc mediation and ultrasound promotion is reported. As a direct application of the resulting bis-allylsilanes, three novel, constrained sila amino acids are prepared for the first time. The design and synthesis of the constrained sila analogue of GABA (?-amino butyric acid) is a highlight of this work. PMID:24827151

Ramesh, Remya; Reddy, D Srinivasa



Different control mechanisms of growth hormone (GH) secretion between ?-amino- and ?-hydroxy-butyric acid: neuroendocrine evidence in parkinson's disease  

Microsoft Academic Search

The observation that baclofen stimulates growth hormone (GH) secretion in normal men, but not in parkinsonian patients led us to test the GH releasing effect of other ?-amino-butyric acid (GABA)ergic agents with different mechanisms of action in Parkinson's disease. For this purpose 10 normal men and 10 de novo parkinsonian patients were tested with sodium valproate (800 mg PO), ?-hydroxybutyric

Riccardo Volpi; Paolo Chiodera; Paolo Caffarra; Augusto Scaglioni; Antonella Saccani; Vittorio Coiro



Glutaminase catalyzes reaction of Glutamate to GABA.  


Here, for the first time, we report an NMR spectroscopy study of l-Glutamine (Gln) conversion by Glutaminase (Glnase), which shows that the reaction involves two distinct steps. In the first step, Glnase rapidly hydrolyzes Gln to Glutamate (Glu) (?16.87 ?mol of Gln/min/mg of Glnase) and in the second step, Glu generated in the first step is decarboxylated into gamma-amino butyric acid (GABA) with a much slower rate (?0.185 ?mol/min/mg). When Glnase was added to the sample containing l-Glu alone, it was also converted to GABA, at a similar rate as in the second step mentioned above. The rate of Glu decarboxylation into GABA by Glnase is about an order of magnitude lower than that by commonly known enzyme, Glutamate decarboxylase. Potential impact of these findings, on the mechanistic aspects of Gln-Glu shuttle in neuroscience and glutaminolysis in tumors, is discussed. PMID:24755074

Nanga, Ravi Prakash Reddy; DeBrosse, Catherine; Singh, Anup; D'Aquilla, Kevin; Hariharan, Hari; Reddy, Ravinder



The evaluation of effect of alpha-lipoic acid and vitamin E on the lipid peroxidation, gamma-amino butyric acid and serotonin level in the brain of mice ( Mus musculus) acutely intoxicated with lindane  

Microsoft Academic Search

The objective of the present study was to evaluate the neurotoxic effects of lindane, in mice and the protective potential of two antioxidants alpha-lipoic acid (ALA) and vitamin E, against the observed lindane induced toxicity. 7–8 weeks old healthy Swiss mice were administered acute doses of lindane (40 mg\\/kg b.w.) or antioxidants or both subcutaneously and analyzed 18 h later. ALA and vitamin

Renu Bist; Devendra Kumar Bhatt



Production of gaba (? - Aminobutyric acid) by microorganisms: a review  

PubMed Central

GABA (?-aminobutyric acid) is a four carbon non-protein amino acid that is widely distributed in plants, animals and microorganisms. As a metabolic product of plants and microorganisms produced by the decarboxylation of glutamic acid, GABA functions as an inhibitory neurotransmitter in the brain that directly affects the personality and the stress management. A wide range of traditional foods produced by microbial fermentation contain GABA, in which GABA is safe and eco-friendly, and also has the possibility of providing new health-benefited products enriched with GABA. Synthesis of GABA is catalyzed by glutamate decarboxylase, therefore, the optimal fermentation condition is mainly based on the biochemical properties of the enzyme. Major GABA producing microorganisms are lactic acid bacteria (LAB), which make food spoilage pathogens unable to grow and act as probiotics in the gastrointestinal tract. The major factors affecting the production of GABA by microbial fermentation are temperature, pH, fermentation time and different media additives, therefore, these factors are summarized to provide the most up-dated information for effective GABA synthesis. There has been a huge accumulation of knowledge on GABA application for human health accompanying with a demand on natural GABA supply. Only the GABA production by microorganisms can fulfill the demand with GABA-enriched health beneficial foods.

Dhakal, Radhika; Bajpai, Vivek K.; Baek, Kwang-Hyun



Fast detection of extrasynaptic GABA with a whole-cell sniffer  

PubMed Central

Gamma-amino-butyric acid (GABA) is the main inhibitory transmitter of the brain. It operates by binding to specific receptors located both inside and outside synapses. The extrasynaptic receptors are activated by spillover from GABAergic synapses and by ambient GABA in the extracellular space. Ambient GABA is essential for adjusting the excitability of neurons. However, due to the lack of suitable methods, little is known about its dynamics. Here we describe a new technique that allows detection of GABA transients and measurement of the steady state GABA concentration with high spatial and temporal resolution. We used a human embryonic kidney (HEK) cell line that stably expresses GABAA receptors composed of ?1, ?2, and ?2 subunits. We recorded from such a HEK cell with the whole-cell patch-clamp technique. The presence of GABA near the HEK cell generated a measurable electric current whose magnitude increased with concentration. A fraction of the current did not inactivate during prolonged exposition to GABA. This technique, which we refer to as a “sniffer” allows the measurement of ambient GABA concentration inside nervous tissue with a resolution of few tens of nanomolars. In addition, the sniffer detects variations in the extrasynaptic GABA concentration with millisecond time resolution. Pilot experiments demonstrate that the sniffer is able to report spillover of GABA induced by synaptic activation in real time. This is the first report on a GABA sensor that combines the ability to detect fast transients and to measure steady concentrations.

Christensen, Rasmus K.; Petersen, Anders V.; Schmitt, Nicole; Perrier, Jean-Francois



Role of GABA Receptors in Fetal Lung Development in Rats  

PubMed Central

Fluid accumulation is critical for lung distension and normal development. The multi-subunit ?-amino butyric acid type A receptors (GABAA) mainly act by mediating chloride ion (Cl?) fluxes. Since fetal lung actively secretes Cl?-rich fluid, we investigated the role of GABAA receptors in fetal lung development. The physiological ligand, GABA, and its synthesizing enzyme, glutamic acid decarboxylase, were predominantly localized to saccular epithelium. To examine the effect of activating GABAA receptors in fetal lung development in vivo, timed-pregnant rats of day 18 gestation underwent an in utero surgery for the administration of GABAA receptor modulators into the fetuses. The fetal lungs were isolated on day 21 of gestation and analyzed for changes in fetal lung development. Fetuses injected with GABA had a significantly higher body weight and lung weight when compared to phosphate-buffered saline (control)-injected fetuses. GABA-injected fetal lungs had a higher number of saccules than the control. GABA increased the number of alveolar epithelial type II cells as indicated by surfactant protein C-positive cells. However, GABA decreased the number of ?-smooth muscle actin-positive myofibroblasts, but did not affect the number of Clara cells or alveolar type I cells. GABA-mediated effects were blocked by the GABAA receptor antagonist, bicuculline. GABA also increased cell proliferation and Cl? efflux in fetal distal lung epithelial cells. In conclusion, our results indicate that GABAA receptors accelerate fetal lung development, likely through an enhanced cell proliferation and/or fluid secretion.

Chintagari, Narendranath Reddy; Jin, Nili; Gao, Li; Wang, Yang; Xi, Dong; Liu, Lin



Effect of ?-Aminobutyric Acid (GABA) Producing Bacteria on In vitro Rumen Fermentation, Biogenic Amine Production and Anti-oxidation Using Corn Meal as Substrate  

PubMed Central

The effects and significance of ?-amino butyric acid (GABA) producing bacteria (GPB) on in vitro rumen fermentation and reduction of biogenic amines (histamine, methylamine, ethylamine, and tyramine) using corn meal as a substrate were determined. Ruminal samples collected from ruminally fistulated Holstein cows served as inoculum and corn was used as substrate at 2% dry matter (DM). Different inclusion rates of GPB and GABA were evaluated. After incubation, addition of GPB had no significant effect on in vitro fermentation pH and total gas production, but significantly increased the ammonia nitrogen (NH3-N) concentration and reduced the total biogenic amines production (p<0.05). Furthermore, antioxidation activity was improved as indicated by the significantly higher concentration of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) among treated samples when compared to the control (p<0.05). Additionally, 0.2% GPB was established as the optimum inclusion level. Taken together, these results suggest the potential of utilizing GPB as feed additives to improve growth performance in ruminants by reducing biogenic amines and increasing anti-oxidation.

Ku, Bum Seung; Mamuad, Lovelia L.; Kim, Seon-Ho; Jeong, Chang Dae; Soriano, Alvin P.; Lee, Ho-Il; Nam, Ki-Chang; Ha, Jong K.; Lee, Sang Suk



Role of nitric oxide on GABA, glutamic acid, activities of GABA-T and GAD in rat brain cerebral cortex  

Microsoft Academic Search

The results of the present study clearly shows that a correlation exists between nitric oxide (NO) and ?-aminobutyric acid transaminase (GABAT-T) activity as well as ?-aminobutyric acid (GABA), glutamic acid and the activity of glutamic acid decarboxylase (GAD). Supporting of this 10 min after the administration of l-Arginine (l-Arg) increased GABA concentration and diminished the activity of GABA-T. There was

A. R Jayakumar; R Sujatha; V Paul; C Asokan; S Govindasamy; R Jayakumar



Relationships of structure to binding of gamma-aminobutyric acid (GABA) and related compounds with the GABA and benzodiazepine receptors.  


The relationship of the structure of gamma-aminobutyric acid (GABA) and 45 related compounds to their binding with the GABA and benzodiazepine (BDZ) receptors was investigated. In the course of evaluating the cross-reactivity of the 45 GABA-related compounds in a GABA radioreceptor assay (GABA-RRA) using [3H]GABA and rat brain synaptic membranes, it became clear that for the molecule to react with GABA-receptors the amino group must be free, but that the carboxy group is not essential. It was also demonstrated that the molecule lost its cross-reactivity if the distance between the alpha-carbon and the amino group exceeded a certain limit, and, additionally, that the cross-reacting potency depended on the stereospecificity of the compound. When the cross-reactivity of GABA related compounds with the GABA receptor was compared with their enhancement of BDZ receptor affinity, a parallelism was found between the two actions. Between d-gamma-amino-beta-hydroxybutyric acid (d-GABOB) and 1-GABOB, however, no difference was found in the BDZ receptor affinity-enhancing effect, although there was a large difference in the cross-reactivity in the GABA-RRA. This indicates that the stereospecificity of the beta-carbon is crucial for the binding of the molecule to the GABA receptor but not essential for its binding to the BDZ receptor, suggesting that the GABA receptor and the BDZ receptor each recognize a different site of the molecule. PMID:6326211

Ogawa, N; Mizuno, S; Tsukamoto, S; Mori, A



A functional role for both ?-aminobutyric acid (GABA) transporter-1 and GABA transporter-3 in the modulation of extracellular GABA and GABAergic tonic conductances in the rat hippocampus  

PubMed Central

Tonic ?-aminobutyric acid (GABA)A receptor-mediated signalling controls neuronal network excitability in the hippocampus. Although the extracellular concentration of GABA (e[GABA]) is critical in determining tonic conductances, knowledge on how e[GABA] is regulated by different GABA transporters (GATs) in vivo is limited. Therefore, we studied the role of GATs in the regulation of hippocampal e[GABA] using in vivo microdialysis in freely moving rats. Here we show that GAT-1, which is predominantly presynaptically located, is the major GABA transporter under baseline, quiescent conditions. Furthermore, a significant contribution of GAT-3 in regulating e[GABA] was revealed by administration of the GAT-3 inhibitor SNAP-5114 during simultaneous blockade of GAT-1 by NNC-711. Thus, the GABA transporting activity of GAT-3 (the expression of which is confined to astrocytes) is apparent under conditions in which GAT-1 is blocked. However, sustained neuronal activation by K+-induced depolarization caused a profound spillover of GABA into the extrasynaptic space and this increase in e[GABA] was significantly potentiated by sole blockade of GAT-3 (i.e. even when uptake of GAT-1 is intact). Furthermore, experiments using tetrodotoxin to block action potentials revealed that GAT-3 regulates extrasynaptic GABA levels from action potential-independent sources when GAT-1 is blocked. Importantly, changes in e[GABA] resulting from both GAT-1 and GAT-3 inhibition directly precipitate changes in tonic conductances in dentate granule cells as measured by whole-cell patch-clamp recording. Thus, astrocytic GAT-3 contributes to the regulation of e[GABA] in the hippocampus in vivo and may play an important role in controlling the excitability of hippocampal cells when network activity is increased.

Kersante, Flavie; Rowley, Samuel C S; Pavlov, Ivan; Gutierrez-Mecinas, Maria; Semyanov, Alexey; Reul, Johannes M H M; Walker, Matthew C; Linthorst, Astrid C E



Mutation of the Drosophila vesicular GABA transporter disrupts visual figure detection  

PubMed Central

The role of gamma amino butyric acid (GABA) release and inhibitory neurotransmission in regulating most behaviors remains unclear. The vesicular GABA transporter (VGAT) is required for the storage of GABA in synaptic vesicles and provides a potentially useful probe for inhibitory circuits. However, specific pharmacologic agents for VGAT are not available, and VGAT knockout mice are embryonically lethal, thus precluding behavioral studies. We have identified the Drosophila ortholog of the vesicular GABA transporter gene (which we refer to as dVGAT), immunocytologically mapped dVGAT protein expression in the larva and adult and characterized a dVGATminos mutant allele. dVGAT is embryonically lethal and we do not detect residual dVGAT expression, suggesting that it is either a strong hypomorph or a null. To investigate the function of VGAT and GABA signaling in adult visual flight behavior, we have selectively rescued the dVGAT mutant during development. We show that reduced GABA release does not compromise the active optomotor control of wide-field pattern motion. Conversely, reduced dVGAT expression disrupts normal object tracking and figure–ground discrimination. These results demonstrate that visual behaviors are segregated by the level of GABA signaling in flies, and more generally establish dVGAT as a model to study the contribution of GABA release to other complex behaviors.

Fei, Hao; Chow, Dawnis M.; Chen, Audrey; Romero-Calderon, Rafael; Ong, Wei S.; Ackerson, Larry C.; Maidment, Nigel T.; Simpson, Julie H.; Frye, Mark A.; Krantz, David E.



Estradiol alters only GAD67 mRNA levels in ischemic rat brain with no consequent effects on GABA  

PubMed Central

The present study tested the hypothesis that estradiol reduces tissue infarction after middle cerebral artery occlusion (MCAO) in estradiol-deficient females by augmenting glutamic acid decarboxylase (GAD) expression and thus activity, leading to increases in ?-amino-butyric acid (GABA) tissue levels. Glutamic acid decarboxylase is the principal enzyme for GABA synthesis and has two isoforms, GAD65 and GAD67, which differ in size and cellular distribution. Rats were ovariectomized 7 to 8 days before receiving no hormone, placebo, or 25 ?g estradiol via subcutaneous implant 7 to 10 days before harvesting tissue in either ischemic cohorts after 2 h of MCAO (end-ischemia) or in nonischemic cohorts. Selected cortical and striatal regions were microdissected from harvested brains. GAD65/67 mRNA levels were determined by microlysate ribonuclease protection assay. End-ischemic GABA concentrations were determined by HPLC. Steroid treatment selectively decreased ischemic cortical GAD67 mRNA levels. In most brain regions evaluated, regional GABA concentrations increased with ischemia regardless of treatment. Estradiol blocked MCAO-induced increases in GABA concentration only in dorsomedial cortex. These data suggest that estradiol repletion in ischemic rat brain selectively decreases GAD67 mRNA levels but does not alter steady-state GABA concentrations. It may be that estradiol under ischemic conditions is attenuating GABA metabolism rather than enhancing synthesis or is augmenting other aspects of GABAergic transmission such as GABA transporters and receptors.

Joh, Hung-Dong; Searles, Robin V; Selmanoff, Michael; Alkayed, Nabil J; Koehler, Raymond C; Hurn, Patricia D; Murphy, Stephanie J



Attenuation of ?-aminobutyric acid (GABA) transaminase activity contributes to GABA increase in the cerebral cortex of mice exposed to ?-cypermethrin.  


The current study investigated the ?-aminobutyric acid (GABA) levels and GABA metabolic enzymes (GABA transaminase (GABA(T)) and glutamate decarboxylase (GAD)) activities at 2 and 4 h after treatment, using a high-performance liquid chromatography with ultraviolet detectors and colorimetric assay, in the cerebral cortex of mice treated with 20, 40 or 80 mg/kg ?-cypermethrin by a single oral gavage, with corn oil as vehicle control. In addition, GABA protein (4 h after treatment), GABA(T) protein (2 h after treatment) and GABA receptors messenger RNA (mRNA) expression were detected by immunohistochemistry, Western blot and real-time quantitative reverse transcriptase polymerase chain reaction, respectively. ?-Cypermethrin (80 mg/kg) significantly increased GABA levels in the cerebral cortex of mice, at both 2 and 4 h after treatment, compared with the control. Also, GABA immunohistochemistry results suggested that the number of positive granules was increased in the cerebral cortex of mice 4 h after exposure to 80 mg/kg ?-cypermethrin when compared with the control. Furthermore, the results also showed that GABA(T) activity detected was significantly decreased in the cerebral cortex of mice 2 h after ?-cypermethrin administration (40 or 80 mg/kg). No significant changes were found in GAD activity, or the expression of GABA(T) protein and GABAB receptors mRNA, in the cerebral cortex of mice, except that 80 mg/kg ?-cypermethrin caused a significant decrease, compared with the vehicle control, in GABAA receptors mRNA expression 4 h after administration. These results suggested that attenuated GABA(T) activity induced by ?-cypermethrin contributed to increased GABA levels in the mouse brain. The downregulated GABAA receptors mRNA expression is most likely a downstream event. PMID:24220872

Han, Y; Cao, D; Li, X; Zhang, R; Yu, F; Ren, Y; An, L



Regulation of GABA-modulin phosphorylation and GABA receptor binding by excitatory amino acids  

SciTech Connect

Primary cultures of cerebellar granule cells phosphorylate numerous proteins including GABA-modulin (GM), which is a putative allosteric modulator of GABA receptors. Cell depolarization and treatment with dicarboxylic excitatory amino acids, which activate PI turnover, Ca/sup 2 +/ influx and guanylate cyclase in granule cells increase the phosphorylation of specific proteins. To determine GM phosphorylation by endogenous protein kinases in living granule cell cultures, GM was isolated by immunoprecipitation and reverse-phase HPLC. High K/sup +/, veratridine, glutamate and NMDA treatment stimulated GM phosphorylation over 2-fold. This increase was abolished by the absence of extracellular Ca/sup 2 +/ and was antagonized by Mg/sup 2 +/ ions and by AVP. The excitatory amino acid action was mimicked by phorbol esters but not by forskolin or by cGMP, and thus may be mediated by an activation of protein kinase C (PKC). Moreover, excitatory amino acids increase /sup 3/H-labelled phorbol ester binding sites in granule cell membrane. The same cultures, treated with glutamate or kainate, showed a 50-fold greater efficacy of muscimol for the stimulation of benzodiazepine (BZ) binding. These data-suggest that excitatory amino acid stimulation of neurons triggers PKC translocation and the activated enzyme phosphorylates GM. The extent of GM phosphorylation may regulate the coupling between GABA and BZ binding sites.

Vaccarino, F.; Guidotti, A.



Subchronic toxicity evaluation of ?-aminobutyric acid (GABA) in rats.  


?-Aminobutyric acid (GABA) is an amino acid compound contained in vegetables such as tomatoes and also widely distributed in mammals. GABA acts as an inhibitory neurotransmitter and promotes parasympathetic activity to provide several beneficial effects, for instance, relaxation, anti-stress, and insomnia. GABA, produced via a fermentation process, has been available as a functional food ingredient. As part of a program to assess its safety, GABA was administered by oral gavage at doses of 500, 1250, and 2500mg/kg body weight to groups of 10 male and 10 female Sprague-Dawley rats for 13weeks. Treatment was not associated with the test substance-related mortality and appeared to be well tolerated. There were no toxicologically and statistically significant changes in urinalysis, hematology, clinical chemistry parameters, and in necropsy findings. A few statistically significant changes in food consumption and body weights were noted in the male groups while any significant changes were not noted in female groups. There was no effect of treatment on organ weights or on the results of the histopathological examinations. The results of toxicity evaluation support the safety use of GABA and the potential use as a functional food ingredient. PMID:24530859

Takeshima, Kazuhito; Yamatsu, Atsushi; Yamashita, Yusuke; Watabe, Kazuya; Horie, Noriko; Masuda, Kazuyuki; Kim, Mujo



The aging human cochlear nucleus: Changes in the glial fibrillary acidic protein, intracellular calcium regulatory proteins, GABA neurotransmitter and cholinergic receptor.  


The human auditory system is highly susceptible to environmental and metabolic insults which further affect the biochemical and physiological milieu of the cells that may contribute to progressive, hearing loss with aging. The cochlear nucleus (CN) is populated by morphologically diverse types of neurons with discrete physiological and neurochemical properties. Between the dorsal and the ventral cochlear nucleus (DCN and VCN), the VCN is further sub-divided into the rostral (rVCN) and caudal (cVCN) sub-divisions. Although, information is available on the age related neurochemical changes in the mammalian CN similar reports on human CN is still sparse. The morphometry and semiquantitative analysis of intensity of expression of glial fibrillary acidic protein (GFAP), calcium binding proteins (calbindin, calretinin and parvalbumin), gamma amino butyric acid (GABA) and nicotinic acetyl choline receptor (nAchR) beta 2 immunostaining were carried out in all three sub-divisions of the human CN from birth to 90 years. There was increased GFAP immunoreactivity in decades 2 and 3 in comparison to decade 1 in the CN. But no change was observed in rVCN from decade 4 onwards, whereas intense staining was also observed in decades 5 and 6 in cVCN and DCN. All three calcium binding proteins were highly expressed in early to middle ages, whereas a significant reduction was found in later decades in the VCN. GABA and nAchR beta 2 expressions were unchanged throughout in all the decades. The middle age may represent a critical period of onset and progression of aging changes in the CN and these alterations may add to the deterioration of hearing responses in the old age. PMID:24412669

Sharma, Saroj; Nag, Tapas C; Thakar, Alok; Bhardwaj, Daya N; Roy, Tara Sankar



Probing GABA Receptor Function in Schizophrenia with Iomazenil  

PubMed Central

Several lines of evidence from post-mortem, brain imaging, and genetic studies in schizophrenia patients suggest that Gamma-amino butyric acid (GABA) deficits may contribute to the pathophysiology of schizophrenia. Pharmacological induction of a transient GABA-deficit state has been shown to enhance vulnerability of healthy subjects to the psychotomimetic effects of various drugs. Exacerbating or creating a GABA deficit was hypothesized to induce or unmask psychosis in schizophrenia patients, but not in healthy controls. To test this hypothesis, a transient GABA deficit was pharmacologically induced in schizophrenia patients and healthy controls using iomazenil, an antagonist and partial inverse agonist of the benzodiazepine receptor. In a double-blind, randomized, placebo-controlled study, clinically stable chronic schizophrenia patients (n=13) received iomazenil (3.7??g administered intravenously over 10?min). Psychosis was measured using the Brief Psychiatric Rating Scale and perceptual alterations were measured using the Clinician Administered Dissociative Symptoms Scale before and after iomazenil administration. These data were compared with the effects of iomazenil in healthy subjects (n=20). Iomazenil produced increases in psychotic symptoms and perceptual alterations in schizophrenia patients, but not in healthy controls. The greater vulnerability of schizophrenia patients to the effects of iomazenil relative to controls provides further support for the GABA-deficit hypothesis of schizophrenia.

Ahn, Kyungheup; Gil, Roberto; Seibyl, John; Sewell, Richard Andrew; D'Souza, Deepak Cyril



Co-activation of GABA receptors inhibits the JNK3 apoptotic pathway via the disassembly of the GluR6-PSD95-MLK3 signaling module in cerebral ischemic-reperfusion.  


In this study, we investigated whether the increase of inhibitory gamma-amino butyric acid (GABA) signal suppresses the excitatory glutamate signal induced by cerebral ischemia and the underlying mechanisms. In global cerebral ischemia, focal cerebral ischemia and oxygen-glucose deprivation, application of muscimol and baclofen, agonists of GABA(A) receptor and GABA(B) receptor, exerted neuroprotection. The agonists inhibited the increased assembly of the GluR6-PSD-95-MLK3 module induced by cerebral ischemia and the activation of the MLK3-MKK4/7-JNK3 cascade. Our results suggest that stimulation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module in cerebral ischemia. PMID:18307989

Han, Dong; Zhang, Quan-Guang; Yong-Liu; Li, Chong; Zong, Yan-Yan; Yu, Chang-Zhou; Wang, Wei; Yan, Jing-Zhi; Zhang, Guang-Yi



Genetic manipulation of the ?-aminobutyric acid (GABA) shunt in rice: overexpression of truncated glutamate decarboxylase (GAD2) and knockdown of ?-aminobutyric acid transaminase (GABA-T) lead to sustained and high levels of GABA accumulation in rice kernels.  


Gamma-aminobutyric acid (GABA) is a non-protein amino acid commonly present in all organisms. Because cellular levels of GABA in plants are mainly regulated by synthesis (glutamate decarboxylase, GAD) and catabolism (GABA-transaminase, GABA-T), we attempted seed-specific manipulation of the GABA shunt to achieve stable GABA accumulation in rice. A truncated GAD2 sequence, one of five GAD genes, controlled by the glutelin (GluB-1) or rice embryo globulin promoters (REG) and GABA-T-based trigger sequences in RNA interference (RNAi) cassettes controlled by one of these promoters as well, was introduced into rice (cv. Koshihikari) to establish stable transgenic lines under herbicide selection using pyriminobac. T? and T? generations of rice lines displayed high GABA concentrations (2-100 mg/100 g grain). In analyses of two selected lines from the T? generation, there was a strong correlation between GABA level and the expression of truncated GAD2, whereas the inhibitory effect of GABA-T expression was relatively weak. In these two lines both with two T-DNA copies, their starch, amylose, and protein levels were slightly lower than non-transformed cv. Koshihikari. Free amino acid analysis of mature kernels of these lines demonstrated elevated levels of GABA (75-350 mg/100 g polished rice) and also high levels of several amino acids, such as Ala, Ser, and Val. Because these lines of seeds could sustain their GABA content after harvest (up to 6 months), the strategy in this study could lead to the accumulation GABA and for these to be sustained in the edible parts. PMID:23421475

Shimajiri, Yasuka; Oonishi, Takayuki; Ozaki, Kae; Kainou, Kumiko; Akama, Kazuhito



Gamma-aminobutyric acid, a potential tumor suppressor for small airway-derived lung adenocarcinoma.  


Pulmonary adenocarcinoma (PAC) is the leading type of lung cancer in smokers and non-smokers that arises in most cases from small airway epithelial cells. PAC has a high mortality due to its aggressive behavior and resistance to cancer therapeutics. We have shown previously that the proliferation of human PAC cells NCI-H322 and immortalized human small airway epithelial cells HPL1D is stimulated by cyclic adenosine monophosphate (cAMP)/protein kinase A-dependent phosphorylation of cyclic adenosine monophosphate response element-binding (CREB) protein and transactivation of the epidermal growth factor receptor and that this pathway is activated by beta-1-adrenoreceptors (beta(1)-ARs) and the non-genomic estrogen receptor beta. Our current in vitro studies with HPL1D and NCI-H322 cells showed that signaling via the gamma-amino butyric acid receptor (GABA(B)R) strongly inhibited base level and isoproterenol-induced cAMP, p-CREB, cyclic adenosine monophosphate response element-luciferase activity and p-extracellular regulated kinase-1 (ERK1)/2 and effectively blocked DNA synthesis and cell migration. The inhibitory effects of gamma-amino butyric acid (GABA) were disinhibited by the GABA(B)R antagonist CGP-35348 or GABA(B)R knockdown. Immunohistochemical investigation of hamster lungs showed significant underexpression of GABA in animals with small airway-derived PACs induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These findings suggest that GABA may have tumor suppressor function in small airway epithelia and the PACs derived from them and that downregulation of GABA by NNK may contribute to the development of this cancer in smokers. Our findings suggest that marker-guided treatment with GABA or a GABA(B)R agonist of individuals with downregulated pulmonary GABA may provide a novel targeted approach for the prevention of PAC in smokers. PMID:18310090

Schuller, Hildegard M; Al-Wadei, Hussein A N; Majidi, Mourad



Selected Gamma Aminobutyric Acid (GABA) Esters may Provide Analgesia for Some Central Pain Conditions  

PubMed Central

Central pain is an enigmatic, intractable condition, related to destruction of thalamic areas, resulting in likely loss of inhibitory synaptic transmission mediated by GABA. It is proposed that treatment of central pain, a localized process, may be treated by GABA supplementation, like Parkinson’s disease and depression. At physiologic pH, GABA exists as a zwitterion that is poorly permeable to the blood brain barrier (BBB). Because the pH of the cerebral spinal fluid (CSF) is acidic relative to the plasma, ion trapping may allow a GABA ester prodrug to accumulate and be hydrolyzed within the CSF. Previous investigations with ester local anesthetics may be applicable to some GABA esters since they are weak bases, hydrolyzed by esterases and cross the BBB. Potential non-toxic GABA esters are discussed. Many GABA esters were investigated in the 1980s and it is hoped that this paper may spark renewed interest in their development.

Goldberg, Joel S.



Involvement of GABA A and GABA B receptors in the mediation of discriminative stimulus effects of ?-hydroxybutyric acid  

Microsoft Academic Search

COLOMBO, G., R. AGABIO, C. LOBINA, R. REALI AND G.L. GESSA. Involvement of GABAA and GABAB receptors in the mediation of discriminative stimulus effects of ?-hydroxybutyric acid. PHYSIOL BEHAV 64(3) 293–302, 1998.—The present study was designed to further investigate the pharmacological profile of the discriminative stimulus effects of ?-hydroxybutyric acid (GHB). Drugs acting at the ?-aminobutyric acid (GABA)B receptor (baclofen

Giancarlo Colombo; Roberta Agabio; Carla Lobina; Roberta Reali; Gian Luigi Gessa



Clinical implications of enzyme-mediated alterations of gamma-aminobutyric acid content in human CSF.  


Pooled samples of lumbar CSF from nine patients with neurologic disorders were aliquoted and subjected to the differential influence of temperature for four hours. The determination of the gamma-amino-butyric acid (GABA) levels in CSF by ion-exchange-fluorometric analysis before and after incubation showed a progressive increase in GABA content of CSF as a function of temperature, reaching a maximum at 50 degrees C. However, no increases in GABA level were noted in CSF incubated at 80 degrees C or 100 degrees C. These in vitro increases in the GABA content of untreated CSF appear to be entirely secondary to enzyme action, subject to individual and temperature variability, and necessitate standardization of clinical CSF protocols. PMID:7247786

Hare, T A; Wood, J H; Manyam, B V



Homocysteine alters cerebral microvascular integrity and causes remodeling by antagonizing GABA-A receptor*  

PubMed Central

High levels of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), are associated with cerebrovascular diseases, such as vascualr dementia, stroke, and Alzheimer's disease. The -amino butyric acid (GABA) is a inhibitory neurotransmitter and a ligand of GABA-A receptor. By inhibiting excitatory response it may decrease complications associated with vascular dementia and stroke. Hcy specifically competes with the GABA-A receptors and acts as an excitotoxic neurotransmitter. Previously we have shown that Hcy increases levels of NADPH oxidase and reactive oxygen species (ROS), and decreases levels of thioredoxin and peroxiredoxin by antagonizing the GABA-A receptor. Hcy treatment leads to activation of matrix metalloproteinases (MMPs) in cerebral circualtion by inducing redox stress and ROS. The hypothesis is that Hcy induces MMPs and suppresses tissue inhibitors of metalloproteinase (TIMPs), in part, by inhibiting the GABA-A receptor. This leads to degradation of the matrix and disruption of the blood brain barrier. The brain cortex of transgenic mouse model of HHcy (cystathionine -synthase, CBS ?/+) and GABA-A receptor null mice treated with and without muscimol (GABA-A receptor agonist) was analysed. The mRNA levels were measured by Q-RT-PCR. Levels of MMP-2, -9, -13, and TIMP-1, -2, -3, and -4 were evaluated by in situ labeling and PCR-gene arrays. Pial venular permeability to fluorescence-labeled albumin was assessed with intravital fluorescence microscopy. We found that Hcy increases metalloproteinase activity and decreases TIMP-4 by antagonizing the GABA-A receptor. The results demonstrate a novel mechanism in which brain microvascular permeability changes during HHcy and vascular dementias, and have therapeutic ramifications for microvascular disease in Alzheimer's patients.

Lominadze, David; Tyagi, Neetu; Sen, Utpal; Ovechkin, Alexander; Tyagi, Suresh C.



Valerenic acid potentiates and inhibits GABA(A) receptors: molecular mechanism and subunit specificity.  


Valerian is a commonly used herbal medicinal product for the treatment of anxiety and insomnia. Here we report the stimulation of chloride currents through GABA(A) receptors (I(GABA)) by valerenic acid (VA), a constituent of Valerian. To analyse the molecular basis of VA action, we expressed GABA(A) receptors with 13 different subunit compositions in Xenopus oocytes and measured I(GABA) using the two-microelectrode voltage-clamp technique. We report a subtype-dependent stimulation of I(GABA) by VA. Only channels incorporating beta(2) or beta(3) subunits were stimulated by VA. Replacing beta(2/3) by beta(1) drastically reduced the sensitivity of the resulting GABA(A) channels. The stimulatory effect of VA on alpha(1)beta(2) receptors was substantially reduced by the point mutation beta(2N265S) (known to inhibit loreclezole action). Mutating the corresponding residue of beta(1) (beta(1S290N)) induced VA sensitivity in alpha(1)beta(1S290N) comparable to alpha(1)beta(2) receptors. Modulation of I(GABA) was not significantly dependent on incorporation of alpha(1), alpha(2), alpha(3) or alpha(5) subunits. VA displayed a significantly lower efficiency on channels incorporating alpha(4) subunits. I(GABA) modulation by VA was not gamma subunit dependent and not inhibited by flumazenil (1 microM). VA shifted the GABA concentration-effect curve towards lower GABA concentrations and elicited substantial currents through GABA(A) channels at > or = 30 microM. At higher concentrations (> or = 100 microM), VA and acetoxy-VA inhibit I(GABA). A possible open channel block mechanism is discussed. In summary, VA was identified as a subunit specific allosteric modulator of GABA(A) receptors that is likely to interact with the loreclezole binding pocket. PMID:17585957

Khom, S; Baburin, I; Timin, E; Hohaus, A; Trauner, G; Kopp, B; Hering, S



Monoamine release in the rat striatum is induced by 8-guanidinovaleric acid and inhibited by GABA agonists  

Microsoft Academic Search

?-Guanidinovaleric acid (GVA) is an endogenous convulsant and is thought to be a specific ?-aminobutyric acid (GABA) antagonist. In this study, we examined the effects of GVA and GABA agonists, GABA, muscimol and baclofen, on the release of dopamine (DA) and serotonin (5-HT) in the rat striatum using a brain dialysis technique. GVA produced a significant increase in the amount

Hideaki Kabuto; Isao Yokoi; Kazuo Iwaya; Akitane Mori



GABA transport and neuroinflammation are coupled in multiple sclerosis: Regulation of the GABA transporter-2 by ganaxolone.  


Interactions between neurotransmitters and the immune system represent new prospects for understanding neuroinflammation and associated neurological disease. GABA is the chief inhibitory neurotransmitter but its actions on immune pathways in the brain are unclear. In the present study, we investigated GABAergic transport in conjunction with neuroinflammation in models of multiple sclerosis (MS). Protein and mRNA levels of ?-amino butyric acid transporter 2 (GAT-2) were examined in cerebral white matter from MS and control (Non-MS) patients, in cultured human macrophages, microglia and astrocytes, and in spinal cords from mice with and without experimental autoimmune encephalomyelitis (EAE) using western blotting, immunocytochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). GABA levels were measured by HPLC. The GAT-2's expression was increased in MS patients' (n=6) white matter, particularly in macrophage lineage cells, compared to Non-MS patients (n=6) (p<0.05). Interferon-? (IFN-?) stimulation of human macrophage lineage cells induced GAT-2 expression and reduced extracellular GABA levels (p<0.05) but soluble GABA treatment suppressed HLA-DR?, GAT-2 and XBP-1/s expression in stimulated macrophage lineage cells (p<0.05). Similarly, the synthetic allopregnanolone analog, ganaxolone (GNX), repressed GAT-2, JAK-1 and STAT-1 expression in activated macrophage lineage cells (p<0.05). In vivo GNX treatment reduced Gat-2, Cd3?, MhcII, and Xbp-1/s expression in spinal cords following EAE induction (p<0.05), which was correlated with improved neurobehavioral outcomes and reduced neuroinflammation, demyelination and axonal injury. These findings highlight altered GABAergic transport through GAT-2 induction during neuroinflammation. GABA transport and neuroinflammation are closely coupled but regulated by GNX, pointing to GABAergic pathways as therapeutic targets in neuroinflammatory diseases. PMID:24814730

Paul, A M; Branton, W G; Walsh, J G; Polyak, M J; Lu, J-Q; Baker, G B; Power, C



Inhibition of Transporter Mediated gamma-Aminobutyric Acid (GABA) Release by SKF 89976-A, a GABA Uptake Inhibitor, Studied in a Primary Neuronal Culture from Chicken.  

National Technical Information Service (NTIS)

The effect of SKF 89976-A, a lipophilic non-substrate inhibitor of the gamma-aminobutyric acid (GABA) transporter, on the release of radioactive GABA and D-aspartate has been studied. Neuronal cultures from 8 day old chick embryos, grown for six days, ser...

L. Lewin M. O. Mattsson A. Sellstroem



Pu-Erh tea and GABA attenuates oxidative stress in kainic acid-induced status epilepticus  

PubMed Central

Background Pu-Erh tea is one of the most-consumed beverages due to its taste and the anti-anxiety-producing effect of the gamma-aminobutyric acid (GABA) if contains. However the protective effects of Pu-Erh tea and its constituent, GABA to kainic acid (KA)-induced seizure have not been fully investigated. Methods We analyzed the effect of Pu-Erh tea leaf (PETL) and GABA on KA-induced neuronal injury in vivo and in vitro. Results PETL and GABA reduced the maximal seizure classes, predominant behavioral seizure patterns, and lipid peroxidation in male FVB mice with status epilepticus. PETL extracts and GABA were effective in protecting KA-treated PC12 cells in a dose-dependent manner and they decreased Ca2+ release, ROS production and lipid peroxidation from KA-stressed PC12 cells. Western blot results revealed that mitogen-activated protein kinases (MAPKs), RhoA and cyclo-oxygenase-2 (COX-2) expression were increased in PC12 cells under KA stress, and PETL and GABA significantly reduced COX-2 and p38 MAPK expression, but not that of RhoA. Furthermore, PETL and GABA reduced PGE2 production from KA-induced PC12 cells. Conclusions Taken together, PETL and GABA have neuroprotective effects against excitotoxins that may have clinical applications in epilepsy.



Induction of the GABA Cell Phenotype: An In Vitro Model for Studying Neurodevelopmental Disorders  

PubMed Central

Recent studies of the hippocampus have suggested that a network of genes is associated with the regulation of the GAD67 (GAD1) expression and may play a role in ?-amino butyric acid (GABA) dysfunction in schizophrenia (SZ) and bipolar disorder (BD). To obtain a more detailed understanding of how GAD67 regulation may result in GABAergic dysfunction, we have developed an in vitro model in which GABA cells are differentiated from the hippocampal precursor cell line, HiB5. Growth factors, such as PDGF, and BDNF, regulate the GABA phenotype by inducing the expression of GAD67 and stimulating the growth of cellular processes, many with growth cones that form appositions with the cell bodies and processes of other GAD67-positive cells. These changes are associated with increased expression of acetylated tubulin, microtubule-associated protein 2 (MAP2) and the post-synaptic density protein 95 (PSD95). The addition of BDNF, together with PDGF, increases the levels of mRNA and protein for GAD67, as well as the high affinity GABA uptake protein, GAT1. These changes are associated with increased concentrations of GABA in the cytoplasm of “differentiated” HiB5 neurons. In the presence of Ca2+ and K+, newly synthesized GABA is released extracellularly. When the HiB5 cells appear to be fully differentiated, they also express GAD65, parvalbumin and calbindin, and GluR subtypes as well as HDAC1, DAXX, PAX5, Runx2, associated with GAD67 regulation. Overall, these results suggest that the HiB5 cells can differentiate into functionally mature GABA neurons in the presence of gene products that are associated with GAD67 regulation in the adult hippocampus.

Subburaju, Sivan; Benes, Francine M.



Gamma-aminobutyric acid (GABA) transport across human intestinal epithelial (Caco-2) cell monolayers  

PubMed Central

Transintestinal absorption of gamma-aminobutyric acid (GABA) via a pH-dependent mechanism is demonstrated in the model human intestinal epithelial cell line Caco-2. Experiments with BCECF [2?,7?,-bis(2-carboxyethyl)-5(6)-carboxyfluorescein]-loaded Caco-2 cells demonstrate that GABA transport across the apical membrane is coupled to proton flow into the cell. Short-circuit current (ISC) measurements using Caco-2 cell monolayers under voltage-clamped conditions demonstrate that pH-dependent GABA transport is a rheogenic process even in the absence of extracellular Na+, consistent with H+/GABA symport. A range of GABA analogues were tested for their abilities to: (a) inhibit pH-dependent [3H]GABA uptake across the apical membrane; (b) stimulate H+ flow across the apical surface of BCECF-loaded Caco-2 cell monolayers; (c) increase inward ISC across voltage-clamped Caco-2 cell monolayers. Nipecotic acid, isonipecotic acid, D,L-?-aminobutyric acid, and 3-amino-1-propanesulphonic acid each caused a marked acidification of intracellular pH and an increase in ISC when superfused at the apical surface of Caco-2 cell monolayers. In contrast L-?-amino-n-butyric acid failed to induce proton flow or ISC. The ability of these compounds to induce proton or current flow across the apical surface of this intestinal epithelium was closely related to the relative inhibitory effects on [3H]GABA uptake. These observations demonstrate H+/GABA symport and suggest that this transport mechanism may be accessible as a route for oral absorption of therapeutically-useful GABA analogues.

Thwaites, David T; Basterfield, Laura; McCleave, Peter M J; Carter, Simon M; Simmons, Nicholas L




PubMed Central

The principal sites of ?-aminobutyric acid (GABA) uptake in lobster nerve-muscle preparations have been determined with radioautographic techniques after binding of the amino acid to proteins by aldehyde fixation. Semiquantitative studies showed that about 30% of the radioactive GABA taken into the tissue was bound to protein by fixation. Both light and electron micrographs showed dense accumulations of label over Schwann and connective tissue cell cytoplasm; muscle was lightly labeled, but axons and terminals were almost devoid of label. The possible role of Schwann and connective tissue cells in the inactivation of GABA released from inhibitory axons is discussed.

Orkand, Paula M.; Kravitz, Edward A.



Immunocytochemistry of GABA and glutamic acid decarboxylase in the thoracic ganglion of the crab Eriphia spinifrons  

Microsoft Academic Search

We have used specific antisera against protein-conjugated ?-aminobutyric acid (GABA) and rat-brain glutamic acid decarboxylase (GAD) in immunocytochemical preparations to study the distribution of putatively GABAergic neurons in the fused thoracic ganglion of the crab Eriphia spinifrons. In the thoracic neuromeres, about 2000 neurons with somata arranged in clusters or located singly in the cell cortex exhibited both GABA-like and

U. Homberg; A. Bleick; W. Rathmayer



Na+-dependent gamma-aminobutyric acid (GABA) transport in the choroid plexus of rabbit.  


The goal of this study was to examine the mechanisms of transport of gamma-aminobutyric acid (GABA) in the choroid plexus. Choroid plexus slices from the rabbit were depleted of ATP with 2,4-dinitrophenol. GABA accumulated in the choroid plexus slices in a concentrative manner in the presence of an inwardly-directed Na+ gradient. Uptake occurred in the presence of Cl-; replacement of Cl- with gluconate abolished uptake. SCN-, NO3- or Br- were able to support uptake in the absence of Cl- to a significant extent (80, 68 and 61% of control, respectively). GABA uptake was saturable (Km of 37 +/- 8.5 microM, Vmax of 409 +/- 43 nmol/g/min). Na+-driven GABA uptake was inhibited by beta-alanine (IC50 = 22.9 microM) and hypotaurine (IC50 = 21.9 microM) but less potently by nipecotic acid (IC50 = 244 microM) and hydroxy-nipecotic acid (IC50 = 284 microM). Betaine, L-(2,4)-diaminobutyric acid, guvacine and 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol were weak inhibitors (IC50 > 500 microM). GABA inhibited Na+-driven uptake of taurine (IC50 = 230 microM); taurine, however, did not inhibit GABA uptake (IC50 > 1 mM). RT-PCR, using degenerate primers for cloned GABA transporters, did not result in the amplification of a band from rat choroid plexus RNA. The location of the choroid plexus in the ventricles of the brain, and its role in the secretion of the cerebrospinal fluid, suggest a role for the choroid plexus Na+-GABA transporter in the disposition of GABA in the brain. PMID:9375816

Ramanathan, V K; Brett, C M; Giacomini, K M



Contents of Neo-flavored Tea (GABA Kintaro) Containing ?-Aminobutyric Acid  

NASA Astrophysics Data System (ADS)

The contents of ?-aminobutyric acid (GABA), catechins, theaflavins, caffeine and pheophorbide-a in neo-flavored tea (GABA Kintaro tea) were analyzed. 1)The amounts of GABA were increased over 1.5mg/g by means of infrared ray irradiation with agitation treatment. 2)There was a tendency for the amount of catechins to be decreased by this treatment, whereas the amount of theaflavins tended to increase with the same treatment. The composition of these contents in this GABA Kintaro tea was almost the same as that of black tea. 3)There was a tendency for the amount of caffeine to be decreased by this treatment. 4)There was a tendency for the amount of pheophorbide-a to be increased by this treatment. 5)The result of this study showed that the amounts of GABA and theaflavins in this GABA Kintaro tea were higher than ordinary green tea but contained few catechins.It became clear that the amount of pheophorbide-a in this GABA Kintaro tea was less than the standard value established in processed chlorella.

Shiraki, Yoshiya


?-Aminobutyric acid (GABA) homeostasis regulates pollen germination and polarized growth in Picea wilsonii.  


?-Aminobutyric acid (GABA) is a four-carbon non-protein amino acid found in a wide range of organisms. Recently, GABA accumulation has been shown to play a role in the stress response and cell growth in angiosperms. However, the effect of GABA deficiency on pollen tube development remains unclear. Here, we demonstrated that specific concentrations of exogenous GABA stimulated pollen tube growth in Picea wilsonii, while an overdose suppressed pollen tube elongation. The germination percentage of pollen grains and morphological variations in pollen tubes responded in a dose-dependent manner to treatment with 3-mercaptopropionic acid (3-MP), a glutamate decarboxylase inhibitor, while the inhibitory effects could be recovered in calcium-containing medium supplemented with GABA. Using immunofluorescence labeling, we found that the actin cables were disorganized in 3-MP treated cells, followed by the transition of endo/exocytosis activating sites from the apex to the whole tube shank. In addition, variations in the deposition of cell wall components were detected upon labeling with JIM5, JIM7, and aniline blue. Our results demonstrated that calcium-dependent GABA signaling regulates pollen germination and polarized tube growth in P. wilsonii by affecting actin filament patterns, vesicle trafficking, and the configuration and distribution of cell wall components. PMID:23900837

Ling, Yu; Chen, Tong; Jing, Yanping; Fan, Lusheng; Wan, Yinglang; Lin, Jinxing



Amino acid and GABA content in different cultivars of Momordica charantia L  

Microsoft Academic Search

The variability of amino acid levels including gamma-aminobutyric acid (GABA) was investigated in six cultivars of bitter melon (Momordica charantia L.) of different origins: Nikko and Peacock from Japan, Galaxy and Verde Buenas from Philippines and two native cultivars from China and Korea. Cultivars varied considerably in the amounts of different amino acids. Among them, the cultivar Verde Buenas recorded

Yong Kyoung Kim; Hui Xu; Nam IL Park; Hee Ock Boo; Sook Young Lee; Sang Un



Cloning of the. gamma. -aminobutyric acid (GABA). rho. sub 1 cDNA: A GABA receptor subunit highly expressed in the retina  

SciTech Connect

Type A {gamma}-aminobutyric acid (GABA{sub A}) receptors are a family of ligand-gated chloride channels that are the major inhibitory neurotransmitter receptors in the nervous system. Molecular cloning has revealed diversity in the subunits that compose this heterooligomeric receptor, but each previously elucidated subunit displays amino acid similarity in conserved structural elements. The authors have used these highly conserved regions to identify additional members of this family by using the polymerase chain reaction (PCR). One PCR product was used to isolate a full-length cDNA from a human retina cDNA library. The mature protein predicted from this cDNA sequence is 458 amino acids long and displays between 30 and 38% amino acid similarity to the previously identified GABA{sub A} subunits. This gene is expressed primarily in the retina but transcripts are also detected in the brain, lung, and thymus. Injection of Xenopus oocytes with RNA transcribed in vitro produces a GABA-responsive chloride conductance and expression of the cDNA in COS cells yields GABA-displaceable muscimol binding. These features are consistent with our identification of a GABA subunit, GABA {rho}{sub 1}, with prominent retinal expression that increases the diversity and tissue specificity of this ligand-gated ion-channel receptor family.

Cutting, G.R.; Lu, Luo; Kasch, L.M.; Montrose-Rafizadeh, C.; Antonarakis, S.E.; Guggino, W.B.; Kazazian, H.H. Jr. (Johns Hopkins Univ. School of Medicine, Baltimore, MD (United States)); O'Hara, B.F.; Donovan, D.M.; Shimada, Shoichi (National Inst. on Drug Abuse, Baltimore, MD (United States)); Uhl, G.R. (National Inst. on Drug Abuse, Baltimore, MD (United States) Johns Hopkins Univ. School of Medicine, Baltimore, MD (United States))



Gamma-aminobutyric acid, a potential tumor suppressor for small airway-derived lung adenocarcinoma  

PubMed Central

Pulmonary adenocarcinoma (PAC) is the leading type of lung cancer in smokers and non-smokers that arises in most cases from small airway epithelial cells. PAC has a high mortality due to its aggressive behavior and resistance to cancer therapeutics. We have shown previously that the proliferation of human PAC cells NCI-H322 and immortalized human small airway epithelial cells HPL1D is stimulated by cyclic adenosine monophosphate (cAMP)/protein kinase A-dependent phosphorylation of cyclic adenosine monophosphate response element-binding (CREB) protein and transactivation of the epidermal growth factor receptor and that this pathway is activated by beta-1-adrenoreceptors (?1-ARs) and the non-genomic estrogen receptor beta. Our current in vitro studies with HPL1D and NCI-H322 cells showed that signaling via the gamma-amino butyric acid receptor (GABABR) strongly inhibited base level and isoproterenol-induced cAMP, p-CREB, cyclic adenosine monophosphate response element-luciferase activity and p-extracellular regulated kinase-1 (ERK1)/2 and effectively blocked DNA synthesis and cell migration. The inhibitory effects of gamma-amino butyric acid (GABA) were disinhibited by the GABABR antagonist CGP-35348 or GABABR knockdown. Immunohistochemical investigation of hamster lungs showed significant underexpression of GABA in animals with small airway-derived PACs induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These findings suggest that GABA may have tumor suppressor function in small airway epithelia and the PACs derived from them and that downregulation of GABA by NNK may contribute to the development of this cancer in smokers. Our findings suggest that marker-guided treatment with GABA or a GABABR agonist of individuals with downregulated pulmonary GABA may provide a novel targeted approach for the prevention of PAC in smokers.

Schuller, Hildegard M.; Al-Wadei, Hussein A.N.; Majidi, Mourad



Effects of traditionally used anxiolytic botanicals on enzymes of the gamma-aminobutyric acid (GABA) system.  


In Canada, the use of botanical natural health products (NHPs) for anxiety disorders is on the rise, and a critical evaluation of their safety and efficacy is required. The purpose of this study was to determine whether commercially available botanicals directly affect the primary brain enzymes responsible for gamma-aminobutyric acid (GABA) metabolism. Anxiolytic plants may interact with either glutamic acid decarboxylase (GAD) or GABA transaminase (GABA-T) and ultimately influence brain GABA levels and neurotransmission. Two in vitro rat brain homogenate assays were developed to determine the inhibitory concentrations (IC50) of aqueous and ethanolic plant extracts. Approximately 70% of all extracts that were tested showed little or no inhibitory effect (IC50 values greater than 1 mg/mL) and are therefore unlikely to affect GABA metabolism as tested. The aqueous extract of Melissa officinalis (lemon balm) exhibited the greatest inhibition of GABA-T activity (IC50 = 0.35 mg/mL). Extracts from Centella asiatica (gotu kola) and Valeriana officinalis (valerian) stimulated GAD activity by over 40% at a dose of 1 mg/mL. On the other hand, both Matricaria recutita (German chamomile) and Humulus lupulus (hops) showed significant inhibition of GAD activity (0.11-0.65 mg/mL). Several of these species may therefore warrant further pharmacological investigation. The relation between enzyme activity and possible in vivo mode of action is discussed. PMID:18066140

Awad, R; Levac, D; Cybulska, P; Merali, Z; Trudeau, V L; Arnason, J T



GABA shunt and polyamine degradation pathway on ?-aminobutyric acid accumulation in germinating fava bean (Vicia faba L.) under hypoxia.  


GABA shunt and polyamine degradation pathway on ?-aminobutyric acid (GABA) accumulation in germinating fava bean under hypoxia was investigated. GABA content, GAD and DAO activity were significantly increased under hypoxia treatment. Glu and polyamine contents enhanced largely and thus supplied as sufficient substrates for GABA formation. In contrast, GABA content decreased, mainly in the embryo, after removing the hypoxia stress. DAO activity, Glu and polyamines contents decreased, while an increment of GAD activity was observed. This indicated that GAD activity can be not only regulated by hypoxia, but by the rapid growth of embryo after the recovery from hypoxia stress. When treated with AG, DAO activity was almost inhibited completely, and the GABA content decreased by 32.96% and 32.07% after treated for 3 and 5 days, respectively. Hence, it can be inferred that about 30% of GABA formed in germinating fava bean under hypoxia was supplied by polyamine degradation pathway. PMID:23017406

Yang, Runqiang; Guo, Qianghui; Gu, Zhenxin



?-Aminobutyric Acid (GABA) Is an Autocrine Excitatory Transmitter in Human Pancreatic ?-Cells  

PubMed Central

OBJECTIVE Paracrine signaling via ?-aminobutyric acid (GABA) and GABAA receptors (GABAARs) has been documented in rodent islets. Here we have studied the importance of GABAergic signaling in human pancreatic islets. RESEARCH DESIGN AND METHODS Expression of GABAARs in islet cells was investigated by quantitative PCR, immunohistochemistry, and patch-clamp experiments. Hormone release was measured from intact islets. GABA release was monitored by whole-cell patch-clamp measurements after adenoviral expression of ?1?1 GABAAR subunits. The subcellular localization of GABA was explored by electron microscopy. The effects of GABA on electrical activity were determined by perforated patch whole-cell recordings. RESULTS PCR analysis detected relatively high levels of the mRNAs encoding GABAAR ?2, ?3, ?2, and ? subunits in human islets. Patch-clamp experiments revealed expression of GABAAR Cl? channels in 52% of ?-cells (current density 9 pA/pF), 91% of ?-cells (current density 148 pA/pF), and 6% of ?-cells (current density 2 pA/pF). Expression of GABAAR subunits in islet cells was confirmed by immunohistochemistry. ?-Cells secreted GABA both by glucose-dependent exocytosis of insulin-containing granules and by a glucose-independent mechanism. The GABAAR antagonist SR95531 inhibited insulin secretion elicited by 6 mmol/l glucose. Application of GABA depolarized ?-cells and stimulated action potential firing in ?-cells exposed to glucose. CONCLUSIONS Signaling via GABA and GABAAR constitutes an autocrine positive feedback loop in human ?-cells. The presence of GABAAR in non–?-cells suggests that GABA may also be involved in the regulation of somatostatin and glucagon secretion.

Braun, Matthias; Ramracheya, Reshma; Bengtsson, Martin; Clark, Anne; Walker, Jonathan N.; Johnson, Paul R.; Rorsman, Patrik



The GABA-B antagonist 2-hydroxysaclofen reverses the effects of baclofen on the discriminative stimulus effects of D-amphetamine in the conditioned taste aversion procedure.  


Some of the behavioral effects of d-amphetamine (d-AMPH) are mediated by an increase in dopamine neurotransmission in the nucleus accumbens. However, there is evidence that gamma-amino-butyric-acid-B (GABA-B) receptors are involved in some behavioral effects of D-AMPH and cocaine. Here, we examined the effects of baclofen on the discriminative stimulus properties of D-AMPH, using conditioned taste aversion (CTA) as the drug discrimination procedure. Male Wistar rats were deprived of water and trained in the CTA procedure. They received D-AMPH (1 mg/kg, i.p.) before gaining access to saccharin, which was followed by an injection of LiCl. On alternate days, the subjects received saline before and after the access to saccharin. After the rats learned the D-AMPH-saline discrimination, the standard dose of D-AMPH was replaced by different doses of D-AMPH, baclofen (a GABA-B receptor agonist), 2-hydroxysaclofen (a GABA-B receptor antagonist), a combination of baclofen+D-AMPH, or a combination of 2-hydroxysaclofen+baclofen+D-AMPH. Baclofen did not substitute for D-AMPH, but, when combined with D-AMPH, it produced a small but significant decrease in the discriminative stimulus effects of D-AMPH. This effect was reversed by administration of 2-hydroxysaclofen. These data suggest that GABA-B receptors play a regulatory role in the discriminative stimulus effects of D-AMPH. PMID:19361543

Miranda, Florencio; Jiménez, Juan C; Cedillo, Laura N; Sandoval-Sánchez, Alma; Millán-Mejía, Patricia; Sánchez-Castillo, Hugo; Velázquez-Martínez, David N



Age-related loss of the GABA synthetic enzyme glutamic acid decarboxylase in rat primary auditory cortex  

Microsoft Academic Search

Age-related changes within the auditory brainstem typically include alterations in inhibitory neurotransmission and coding mediated by GABA and glycinergic circuits. As part of an effort to evaluate the impact of aging on neurotransmission in the higher auditory centers, the present study examined age-related changes in the GABA synthetic enzyme, glutamic acid decarboxylase (GAD), in rat primary auditory cortex (AI), which

L. L. Ling; L. F. Hughes; D. M. Caspary



Marked increases of plasma gamma-aminobutyric acid concentrations in cirrhotic patients with portacaval shunts are not associated with alterations of cerebral functions.  


Several previous studies have shown that the plasma concentration of gamma-amino-butyric acid (GABA) is markedly increased in patients with hepatic encephalopathy, and it has been suggested that decreased metabolism of peripheral GABA might contribute to the cerebral dysfunctions observed. In the present study, plasma GABA-like activity was determined by a radioreceptor assay in 21 cirrhotic patients in whom, at least 2 months prior to the study, portocaval shunt surgery had been performed for treatment of recurrent variceal bleeding. Compared to 10 healthy volunteers, plasma GABA concentrations were increased in all cirrhotic patients, whereas most other amino acids, including those known to interfere with the GABA radioreceptor assay at elevated concentrations, were within the normal range. Despite an about 3- to 16-fold increase in individual GABA concentration, none of the patients showed clinical signs of overt hepatic encephalopathy on conventional neurologic (including EEG) and mental status examination. Furthermore, when a psychometric test system was used for evaluation of intellectual and psychomotor functions, all patients performed within the normal range and could not be distinguished from healthy volunteers. The data indicate that, at least in chronic liver disease, impaired metabolism of peripheral GABA does not lead to cerebral dysfunctions. PMID:1797600

Löscher, W; Kretz, F J; Karavias, T; Dillinger, U



Correlation Between Hepatocyte Growth Factor (HGF) and Gamma-Aminobutyric Acid (GABA) Plasma Levels in Autistic Children  

PubMed Central

There is much support for the role of Gamma-Aminobutyric acid (GABA) in the etiology of autism. Recent research has shown that hepatocyte growth factor (HGF) modulates GABAergic inhibition and seizure susceptibility. This study was designed to determine and correlate plasma levels of HGF, GABA, as well as symptom severity, in autistic children and neurotypical controls. Plasma from 48 autistic children and 29 neurotypical controls was assessed for HGF and GABA concentration using ELISAs. Symptom severity was assessed in these autistic individuals and compared to HGF and GABA concentrations. We previously reported that autistic children had significantly decreased levels of HGF. In this study, the same autistic children had significantly increased plasma levels of GABA (P = 0.002) and decreased HGF levels correlated with these increased GABA levels (r = 0.3; P = 0.05). High GABA levels correlated with increasing hyperactivity (r = 0.6; P = 0.0007) and impulsivity severity (r = 0.5; P = 0.007), tip toeing severity (r = 0.35; P = 0.03), light sensitivity (r = 0.4; P = 0.02), and tactile sensitivity (r = 0.4; P = 0.01). HGF levels did not correlate significantly with any symptom severity. These results suggest an association between HGF and GABA levels and suggest that plasma GABA levels are related to symptom severity in autistic children.

Russo, Anthony J.



Physiological correlates of responses to gamma-aminobutyric acid (GABA) recorded from rat visual cortical neurons in vitro.  


Responses to focal application of gamma-aminobutyric acid (GABA) were compared to synaptic potentials elicited by afferent stimulation of rat visual cortical neurons, using a slice preparation and conventional intracellular recording techniques. GABA produced three types of responses: a brief hyperpolarization (mean reversal potential, -72 mV), brief depolarization (mean reversal potential, -50 mV), or a prolonged hyperpolarization (mean reversal potential, -80 mV). Synaptic potentials included simple or complex EPSPs and EPSPs followed by mono- or biphasic IPSPs. A comparison of the characteristics of the GABA responses and synaptic potentials indicated that GABA may mediate both phases of the IPSP in these cells. Our results suggest that despite differences in the circuitry of the visual cortex as opposed to other neocortical and allocortical (hippocampal) areas (Mountcastle and Poggio, 1968; Colonnier and Rossignol, 1969; Creutzfeldt, 1978; Kuhlenbeck, 1978), the inhibitory control of cortical pyramidal and nonpyramidal neurons by GABA is quite similar. PMID:3212675

Scharfman, H E; Sarvey, J M



GABA-A receptor impairment in cerebellar ataxia with anti-glutamic acid decarboxylase antibodies.  


Antibodies against glutamic acid decarboxylase (GAD-Abs) are associated with cerebellar ataxia, which is refractory to treatment with GABAergic drugs. To investigate the GABAergic neuronal system in vivo, we performed a combined positron emission tomography (PET) study with [(11)C]-flumazenil and [(18)F]-fluorodeoxyglucose (FDG) in three patients with cerebellar ataxia with GAD-Abs. The GABA-A receptor function was investigated using flumazenil, which is a selective GABA-A receptor ligand, while FDG-PET using a three-dimensional stereotactic surface projection analysis was performed to estimate the metabolic rates of glucose (MRGlc) in the patients. GABAergic drugs showed no efficacy for the cerebellar ataxia in all three patients, and all three displayed a significant decrease in flumazenil binding in the cerebellum. No MRGlc decrease in the cerebellum was found in the two patients who presented with amelioration of cerebellar ataxia following intravenous immunoglobulin (IVIG) therapy, whereas a significant MRGlc decrease in the cerebellar hemisphere was observed in another patient who showed severe cerebellar atrophy on magnetic resonance images and no response to the IVIG therapy. The decreased flumazenil binding in the present patients indicated cerebellar GABA-A receptor impairment, which may be due to either neuronal cell loss, as demonstrated by the decreased MRGlc, or a dysfunction in GABAergic neuronal inhibition. Although GAD-Abs have been postulated to prevent the synthesis of GABA, resulting in decreased GABAergic transmission, the GABA-A receptor impairment may play another pathogenic role in cerebellar ataxia associated with GAD-Abs resulting in a condition refractory to GABAergic drug therapy. PMID:24091766

Hosoi, Yasushi; Suzuki-Sakao, Makiko; Terada, Tatsuhiro; Konishi, Takashi; Ouchi, Yasuomi; Miyajima, Hiroaki; Kono, Satoshi



Calpain Cleavage of Brain Glutamic Acid Decarboxylase 65 Is Pathological and Impairs GABA Neurotransmission  

PubMed Central

Previously, we have shown that the GABA synthesizing enzyme, L-glutamic acid decarboxylase 65 (GAD65) is cleaved to form its truncated form (tGAD65) which is 2–3 times more active than the full length form (fGAD65). The enzyme responsible for cleavage was later identified as calpain. Calpain is known to cleave its substrates either under a transient physiological stimulus or upon a sustained pathological insult. However, the precise role of calpain cleavage of fGAD65 is poorly understood. In this communication, we examined the cleavage of fGAD65 under diverse pathological conditions including rats under ischemia/reperfusion insult as well as rat brain synaptosomes and primary neuronal cultures subjected to excessive stimulation with high concentration of KCl. We have shown that the formation of tGAD65 progressively increases with increasing stimulus concentration both in rat brain synaptosomes and primary rat embryo cultures. More importantly, direct cleavage of synaptic vesicle - associated fGAD65 by calpain was demonstrated and the resulting tGAD65 bearing the active site of the enzyme was detached from the synaptic vesicles. Vesicular GABA transport of the newly synthesized GABA was found to be reduced in calpain treated SVs. Furthermore, we also observed that the levels of tGAD65 in the focal cerebral ischemic rat brain tissue increased corresponding to the elevation of local glutamate as indicated by microdialysis. Moreover, the levels of tGAD65 was also proportional to the degree of cell death when the primary neuronal cultures were exposed to high KCl. Based on these observations, we conclude that calpain-mediated cleavage of fGAD65 is pathological, presumably due to decrease in the activity of synaptic vesicle - associated fGAD65 resulting in a decrease in the GABA synthesis - packaging coupling process leading to reduced GABA neurotransmission.

Buddhala, Chandana; Suarez, Marjorie; Modi, Jigar; Prentice, Howard; Ma, Zhiyuan; Tao, Rui; Wu, Jang Yen



Temporal- and Location-Specific Alterations of the GABA Recycling System in Mecp2 KO Mouse Brains.  


Rett syndrome (RTT), associated with mutations in methyl-CpG-binding protein 2 (Mecp2), is linked to diverse neurological symptoms such as seizures, motor disabilities, and cognitive impairments. An altered GABAergic system has been proposed as one of many underlying pathologies of progressive neurodegeneration in several RTT studies. This study for the first time investigated the temporal- and location-specific alterations in the expression of ?-amino butyric acid (GABA) transporter 1 (GAT-1), vesicular GABA transporter (vGAT), and glutamic acid decarboxylase 67kD (GAD67) in wild type (WT) and knockout (KO) mice in the Mecp2(tm1.1Bird/y) mouse model of RTT. Immunohistochemistry (IHC) co-labeling of GAT-1 with vGAT identified GABAergic synapses that were quantitated for mid-sagittal sections in the frontal cortex (FC), hippocampal dentate gyrus (DG), and striatum (Str). An age-dependent increase in the expression of synaptic GABA transporters, GAT-1, and vGAT, was observed in the FC and DG in WT brains. Mecp2 KO mice showed a significant alteration in this temporal profile that was location-specific, only in the FC. GAD67-positive cell densities also showed an age-dependent increase in the FC, but a decrease in the DG in WT mice. However, these densities were not significantly altered in the KO mice in the regions examined in this study. Therefore, the significant location-specific downregulation of synaptic GABA transporters in Mecp2 KO brains with unaltered densities of GAD67-positive interneurons may highlight the location-specific synaptic pathophysiology in this model of RTT. PMID:24737935

Kang, Seok K; Kim, Shin Tae; Johnston, Michael V; Kadam, Shilpa D



Temporal- and Location-Specific Alterations of the GABA Recycling System in Mecp2 KO Mouse Brains  

PubMed Central

Rett syndrome (RTT), associated with mutations in methyl-CpG-binding protein 2 (Mecp2), is linked to diverse neurological symptoms such as seizures, motor disabilities, and cognitive impairments. An altered GABAergic system has been proposed as one of many underlying pathologies of progressive neurodegeneration in several RTT studies. This study for the first time investigated the temporal- and location-specific alterations in the expression of ?-amino butyric acid (GABA) transporter 1 (GAT-1), vesicular GABA transporter (vGAT), and glutamic acid decarboxylase 67kD (GAD67) in wild type (WT) and knockout (KO) mice in the Mecp2tm1.1Bird/y mouse model of RTT. Immunohistochemistry (IHC) co-labeling of GAT-1 with vGAT identified GABAergic synapses that were quantitated for mid-sagittal sections in the frontal cortex (FC), hippocampal dentate gyrus (DG), and striatum (Str). An age-dependent increase in the expression of synaptic GABA transporters, GAT-1, and vGAT, was observed in the FC and DG in WT brains. Mecp2 KO mice showed a significant alteration in this temporal profile that was location-specific, only in the FC. GAD67-positive cell densities also showed an age-dependent increase in the FC, but a decrease in the DG in WT mice. However, these densities were not significantly altered in the KO mice in the regions examined in this study. Therefore, the significant location-specific downregulation of synaptic GABA transporters in Mecp2 KO brains with unaltered densities of GAD67-positive interneurons may highlight the location-specific synaptic pathophysiology in this model of RTT.

Kang, Seok K; Kim, Shin Tae; Johnston, Michael V; Kadam, Shilpa D



Probing the orthosteric binding site of GABAA receptors with heterocyclic GABA carboxylic acid bioisosteres.  


The ionotropic GABAA receptors (GABAARs) are widely distributed in the central nervous system where they play essential roles in numerous physiological and pathological processes. A high degree of structural heterogeneity of the GABAAR has been revealed and extensive effort has been made to develop selective and potent GABAAR agonists. This review investigates the use of heterocyclic carboxylic acid bioisosteres within the GABAAR area. Several heterocycles including 3-hydroxyisoxazole, 3-hydroxyisoxazoline, 3-hydroxyisothiazole, and the 1- and 3-hydroxypyrazole rings have been employed in order to map the orthosteric binding site. The physicochemical properties of the heterocyclic moieties making them suitable for bioisosteric replacement of the carboxylic acid in the molecule of GABA are discussed. A variety of synthetic strategies for synthesis of the heterocyclic scaffolds are available. Likewise, methods for introduction of substituents into specific positions of the heterocyclic scaffolds facilitate the investigation of different regions in the orthosteric binding pocket in close vicinity of the core scaffolds of muscimol/GABA. The development of structural models, from pharmacophore models to receptor homology models, has provided more insight into the molecular basis for binding. Similar binding modes are proposed for the heterocyclic GABA analogues covered in this review by use of ligand-receptor docking into the receptor homology model and the presented structure-activity relationships. A network of interactions between the analogues and the binding pocket is leaving no room for substituents and underline the limited space in the GABAAR orthosteric binding site when in the agonist conformation. PMID:24362592

Petersen, Jette G; Bergmann, Rikke; Krogsgaard-Larsen, Povl; Balle, Thomas; Frølund, Bente



Detection of ?-Aminobutyric Acid (GABA) by Longitudinal Scalar Order Difference Editing  

NASA Astrophysics Data System (ADS)

Two novel spectral editing techniques for the in vivo detection of ?-aminobutyric acid (GABA) are presented. The techniques rely on the generation of longitudinal scalar order (LSO) coherences, which in combination with J-difference editing results in the selective detection of GABA. The utilization of LSO coherences makes the editing sequences insensitive to phase and frequency instabilities. Furthermore, the spectral editing selectivity can be increased independent of the echo time, thereby opening the echo time for state-of-the-art water suppression and/or spatial localization techniques. The performance of the LSO editing techniques is theoretically demonstrated with product operator calculations and density matrix simulations and experimentally evaluated on phantoms in vitro and on human brain in vivo.

de Graaf, Robin A.; Rothman, Douglas L.



Effects of Vigabatrin, an Irreversible GABA Transaminase Inhibitor, on Ethanol Reinforcement and Ethanol Discriminative Stimuli in Mice  

PubMed Central

We tested the hypothesis that the irreversible gamma-amino butyric acid (GABA) transaminase inhibitor, ?-vinyl GABA (Vigabatrin; VGB) would reduce ethanol reinforcement and enhance the discriminative stimulus effect of ethanol, effectively reducing ethanol intake. The present studies used adult C57BL/6J (B6) mice in well-established operant, two-bottle choice consumption, locomotor activity and ethanol discrimination procedures, to examine comprehensively the effects of VGB on ethanol-supported behaviors. VGB dose-dependently reduced operant responding for ethanol as well as ethanol consumption for long periods of time. Importantly, a low dose (200 mg/kg) of VGB was selective for reducing ethanol responding without altering intake of food or water reinforcement. Higher VGB doses (>200 mg/kg) still reduced ethanol intake, but also significantly increased water consumption and, more modestly, increased food consumption. While not affecting locomotor activity on its own, VGB interacted with ethanol to reduce the stimulatory effects of ethanol on locomotion. Finally, VGB (200 mg/kg) significantly enhanced the discriminative stimulus effects of ethanol as evidenced by significant left-ward and up-ward shifts in ethanol generalization curves. Interestingly, VGB treatment was associated with slight increases in blood ethanol concentrations. The reduction in ethanol intake by VGB appears to be related to the ability of VGB to potentiate the pharmacological effects of ethanol.

Griffin, William C.; Nguyen, Shaun A.; Deleon, Christopher P.; Middaugh, Lawrence D.



GABA, taurine and learning: release of amino acids from slices of chick brain following filial imprinting.  


The intermediate and medial hyperstriatum ventrale (IMHV) is a forebrain region in the domestic chick that is a site of information storage for the learning process of imprinting. We enquired whether imprinting is associated with learning-related increases in calcium-dependent, potassium-stimulated release of neurotransmitter amino acids from the IMHV. Chicks were hatched and reared in darkness until 15-30 h after hatching. They then either remained in darkness or were trained for 2 h by exposure to an imprinting stimulus. One hour later, the chicks were given a preference test and a preference score was calculated from the results of this test, as a measure of imprinting. Chicks were killed 2 h after training. Slices from the left and right IMHV of trained and untrained chicks were superfused with Krebs' solution either with or without calcium and the superfusate assayed for arginine, aspartate, citrulline, GABA, glutamate, glycine and taurine using high-performance liquid chromatography. For calcium-containing superfusates from the left IMHV, preference score was significantly correlated with potassium-stimulated release of (i) GABA (r=0.51, 23 d.f., P=0.008) and (ii) taurine (r=0.77, 23 d.f., P<0.0001). There was no significant difference between the mean values of trained and untrained chicks for either compound. However, examination of the variance of the data indicated that release of both GABA and taurine increased as a result of learning. No significant correlation between preference score and release was found for any of the amino acids from the right IMHV, nor for control tissue from the left IMHV superfused with calcium-free solution. These results demonstrate that the learning process of imprinting is associated with increases in releasable pools of GABA and taurine and/or membrane excitability in the left IMHV. PMID:11672599

McCabe, B J; Horn, G; Kendrick, K M



ZAPA, (Z)-3-[(aminoiminomethyl)thio]-2-propenoic acid hydrochloride, a potent agonist at GABA-receptors on the Ascaris muscle cell.  


This study is the first report of a compound which is equal in efficacy to gamma-aminobutyric acid (GABA) at the nematode Ascaris muscle GABA-receptor. The GABA-receptor at the Ascaris muscle cell which mediates a membrane hyperpolarization and muscle relaxation has eluded classification. The structure-activity profile of this receptor is not typical of GABAA or GABAB-receptors. Here we report that the isothiouronium compound ZAPA is as potent as GABA at this receptor. This finding has important implications for the characterization of the Ascaris GABA-receptor and the design of novel anthelmintics. PMID:2851353

Holden-Dye, L; Walker, R J



Paralogous chemoreceptors mediate chemotaxis towards protein amino acids and the non-protein amino acid gamma-aminobutyrate (GABA).  


The paralogous receptors PctA, PctB and PctC of Pseudomonas aeruginosa were reported to mediate chemotaxis to amino acids, intermediates of amino acid metabolism and chlorinated hydrocarbons. We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. In addition, PctC-LBR recognized GABA but not any other structurally related compound. l-Gln, one of the three amino acids that is not recognized by PctA-LBR, was the most tightly binding ligand to PctB suggesting that PctB has evolved to mediate chemotaxis primarily towards l-Gln. Bacteria were efficiently attracted to l-Gln and GABA, but mutation of pctB and pctC, respectively, abolished chemoattraction. The physiological relevance of taxis towards GABA is proposed to reside in an interaction with plants. LBRs were predicted to adopt double PDC (PhoQ/DcuS/CitA) like structures and site-directed mutagenesis studies showed that ligands bind to the membrane-distal module. Analytical ultracentrifugation studies have shown that PctA-LBR and PctB-LBR are monomeric in the absence and presence of ligands, which is in contrast to the enterobacterial receptors that require sensor domain dimers for ligand recognition. PMID:23650915

Rico-Jiménez, Miriam; Muñoz-Martínez, Francisco; García-Fontana, Cristina; Fernandez, Matilde; Morel, Bertrand; Ortega, Alvaro; Ramos, Juan Luis; Krell, Tino



Regulation of ?-aminobutyric acid (GABA) release in cerebral cortex in the ?-hydroxybutyric acid (GHB) model of absence seizures in rat  

Microsoft Academic Search

?-Hydroxybutyric acid (GHB) has the ability to induce absence seizures. The precise way in which GHB causes seizures remains unclear, but GABAB- and\\/or GHB-mediated presynaptic mechanisms within thalamocortical circuitry may play a role. In the present study, we determined the basal and K+-evoked release of GABA and glutamate in the superficial laminae of frontal cortex during GHB-induced absence seizures. Our

R. Q Hu; P. K Banerjee; O. C Snead III



Exogenous ?-aminobutyric acid (GABA) affects pollen tube growth via modulating putative Ca2+-permeable membrane channels and is coupled to negative regulation on glutamate decarboxylase.  


?-Aminobutyric acid (GABA) is implicated in pollen tube growth, but the molecular and cellular mechanisms that it mediates are largely unknown. Here, it is shown that exogenous GABA modulates putative Ca(2+)-permeable channels on the plasma membranes of tobacco pollen grains and pollen tubes. Whole-cell voltage-clamp experiments and non-invasive micromeasurement technology (NMT) revealed that the influx of Ca(2+) increases in pollen tubes in response to exogenous GABA. It is also demonstrated that glutamate decarboxylase (GAD), the rate-limiting enzyme of GABA biosynthesis, is involved in feedback controls of Ca(2+)-permeable channels to fluctuate intracellular GABA levels and thus modulate pollen tube growth. The findings suggest that GAD activity linked with Ca(2+)-permeable channels relays an extracellular GABA signal and integrates multiple signal pathways to modulate tobacco pollen tube growth. Thus, the data explain how GABA mediates the communication between the style and the growing pollen tubes. PMID:24799560

Yu, Guang-Hui; Zou, Jie; Feng, Jing; Peng, Xiong-Bo; Wu, Ju-You; Wu, Ying-Liang; Palanivelu, Ravishankar; Sun, Meng-Xiang



Exogenous ?-aminobutyric acid (GABA) affects pollen tube growth via modulating putative Ca2+-permeable membrane channels and is coupled to negative regulation on glutamate decarboxylase  

PubMed Central

?-Aminobutyric acid (GABA) is implicated in pollen tube growth, but the molecular and cellular mechanisms that it mediates are largely unknown. Here, it is shown that exogenous GABA modulates putative Ca2+-permeable channels on the plasma membranes of tobacco pollen grains and pollen tubes. Whole-cell voltage-clamp experiments and non-invasive micromeasurement technology (NMT) revealed that the influx of Ca2+ increases in pollen tubes in response to exogenous GABA. It is also demonstrated that glutamate decarboxylase (GAD), the rate-limiting enzyme of GABA biosynthesis, is involved in feedback controls of Ca2+-permeable channels to fluctuate intracellular GABA levels and thus modulate pollen tube growth. The findings suggest that GAD activity linked with Ca2+-permeable channels relays an extracellular GABA signal and integrates multiple signal pathways to modulate tobacco pollen tube growth. Thus, the data explain how GABA mediates the communication between the style and the growing pollen tubes.

Yu, Guang-Hui; Zou, Jie; Feng, Jing; Peng, Xiong-Bo; Wu, Ju-You; Wu, Ying-Liang; Palanivelu, Ravishankar; Sun, Meng-Xiang




EPA Science Inventory

The ventral hippocampi of male, Fischer-344 rats were implanted with microdialysis probes and the effects of systemically administered kainic acid (KA) (8 mg/kg, s.c.) on the in vivo release of amino acids were measured for four hours after administration. n order to measure GABA...


The dual effects of GABA and related amino acids on the electrical threshold of ventral horn group Ia afferent terminations in the cat  

Microsoft Academic Search

Amino acids were administered microelectrophoretically near the unmyelinated terminations of extensor muscle Ia afferent terminations stimulated electrically in the vicinity of lumbar motoneurones in anaesthetized cats. The predominant effect of one group (structurally related to GABA, poor substrates for in vitro amino acid uptake systems) was a reduction in the threshold (depolarization). The second group (including GABA and structural analogues

D. R. Curtis; D. Lodge; J. C. Bornstein; M. J. Peet; J. D. Lean



Further characterization of in vitro conditions appropriate for GABA determination in human CSF: impact of acid deproteinization and freeze/thaw.  


Recently established standardized protocols for collection, handling, and storage of CSF for measurement of gamma-aminobutyric acid (GABA) have proven valuable in the characterization of various CNS disorders. In response to two recent reports which may have an impact on certain widely used protocols, we have, using the confirmed ion-exchange/fluorometric procedure, systematically evaluated the effects of deproteinization with various concentrations of sulfosalicylic acid (SSA) ranging from 0 to 10% (100 mg/ml), as well as the effects of freeze/thaw (F/T) on CSF GABA levels. Results of F/T studies documented that levels are stable to freezing and thawing. Acid deproteinization studies revealed the presence of an equilibrium between strictly free GABA, demonstrable only in acid-free CSF, and a very loosely bound form of GABA, fully demonstrable only in CSF deproteinized with concentrations of SSA above 1% (10 mg/ml). The relationship between GABA concentrations in undeproteinized and acid-deproteinized CSF revealed a highly significant (p less than .001) correlation, suggesting that alterations of central GABAergic activity would be reflected by either the level of strictly free GABA or free plus loosely bound GABA. This hypothesis was upheld in studies of patients with Parkinson's disease (PD) and Huntington's disease (HD), two neurologic disorders in which dysfunctions of the GABA system have been implicated. Results indicated that CSF GABA levels are significantly reduced in both PD and HD patients compared with neurologically normal controls, whether the measurement is of free GABA or free plus loosely bound GABA. Thus, we conclude that the level of strictly free GABA is stable to freezing and thawing and can only be accurately determined in nonacidified CSF; however, existing protocols employing deproteinization in 5% SSA yield data that provide an equally good reflection of central GABAergic transmission. PMID:6225837

Ferraro, T N; Manyam, B V; Hare, T A



GABA (Gamma Aminobutyric Acid) Involvement in the Action of Anti-Anxiety Drugs.  

National Technical Information Service (NTIS)

GABA involvement in the action of anti-anxiety drugs were studied. Because GABA is contained exclusively within Glial cells in the rat superior cervical ganglion and pineal gland, they were chosen as the models in determining the role of glial GABA in syn...

A. Suria



Endogenous kynurenic acid regulates extracellular GABA levels in the rat prefrontal cortex.  


The tryptophan metabolite kynurenic acid (KYNA) is an endogenous antagonist of the ?7 nicotinic acetylcholine receptor (?7nAChR) and, at higher concentrations, inhibits ionotropic glutamate receptors. Increases in KYNA levels are seen in brain and cerebrospinal fluid in individuals with schizophrenia (SZ) and may be causally related to cognitive deficits in SZ and other psychiatric diseases. As dysfunction of circuits involving GABAergic neurons in the prefrontal cortex (PFC) likely plays a role in the cognitive impairments seen in these disorders, we examined the effects of KYNA on extracellular GABA in this brain area. Applied to awake rats for 2 h by reverse dialysis, KYNA concentration-dependently and reversibly reduced extracellular GABA levels, with 300 nM KYNA causing a nadir of ?45% of baseline concentrations. This effect was not duplicated by reverse dialysis of the selective glycineB receptor antagonist 7-Cl-KYNA (100 nM) or the AMPA/kainate receptor antagonist CNQX (100 ?M), and was prevented by co-application of galantamine (5 ?M), a positive allosteric modulator of the ?7nAChR. Conversely, inhibition of endogenous KYNA formation by reverse dialysis of (S)-4-(ethylsulfonyl)benzoylalanine (ESBA; 5 mM) reversibly increased GABA levels in the PFC, reaching a peak of ?160% of baseline concentrations. Co-infusion of 30 nM KYNA neutralized this effect. Taken together, these results demonstrate a role for endogenous KYNA in the bi-directional control of GABAergic neurotransmission in the PFC. Pharmacological manipulation of KYNA may therefore be useful in the treatment of GABAergic impairments in SZ and other brain disorders involving the PFC. PMID:24607890

Beggiato, Sarah; Tanganelli, Sergio; Fuxe, Kjell; Antonelli, Tiziana; Schwarcz, Robert; Ferraro, Luca



Kynurenic acid, by targeting ?7 nicotinic acetylcholine receptors, modulates extracellular GABA levels in the rat striatum in vivo.  


Kynurenic acid (KYNA) is an astrocyte-derived non-competitive antagonist of the ?7 nicotinic acetylcholine receptor (?7nAChR) and inhibits the NMDA receptor (NMDAR) competitively. The main aim of the present study was to examine the possible effects of KYNA (30 - 1000 nm), applied locally by reverse dialysis for 2 h, on extracellular GABA levels in the rat striatum. KYNA concentration-dependently reduced GABA levels, with 300 nm KYNA causing a maximal reduction to ~60% of baseline concentrations. The effect of KYNA (100 nm) was prevented by co-application of galantamine (5 ?m), an agonist at a site of the ?7nAChR that is very similar to that targeted by KYNA. Infusion of 7-chlorokynurenic acid (100 nm), an NMDAR antagonist acting selectively at the glycineB site of the receptor, affected neither basal GABA levels nor the KYNA-induced reduction in GABA. Inhibition of endogenous KYNA formation by reverse dialysis of (S)-4-(ethylsulfonyl)benzoylalanine (ESBA; 1 mm) increased extracellular GABA levels, reaching a peak of 156% of baseline levels after 1 h. Co-infusion of 100 nm KYNA abolished the effect of ESBA. Qualitatively and quantitatively similar, bi-directional effects of KYNA on extracellular glutamate were observed in the same microdialysis samples. Taken together, the present findings suggest that fluctuations in endogenous KYNA levels, by modulating ?7nAChR function, control extracellular GABA levels in the rat striatum. This effect may be relevant for a number of physiological and pathological processes involving the basal ganglia. PMID:23442092

Beggiato, Sarah; Antonelli, Tiziana; Tomasini, Maria Cristina; Tanganelli, Sergio; Fuxe, Kjell; Schwarcz, Robert; Ferraro, Luca



Behavioral effects of gamma-hydroxybutyrate, its precursor gamma-butyrolactone, and GABA(B) receptor agonists: time course and differential antagonism by the GABA(B) receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348).  


Gamma-hydroxybutyrate (GHB) is used therapeutically and recreationally. The mechanism by which GHB produces its therapeutic and recreational effects is not entirely clear, although GABA(B) receptors seem to play an important role. This role could be complex, because there are indications that different GABA(B) receptor mechanisms mediate the effects of GHB and the prototypical GABA(B) receptor agonist baclofen. To further explore possible differences in underlying GABA(B) receptor mechanisms, the present study examined the effects of GHB and baclofen on operant responding and their antagonism by the GABA(B) receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348). Pigeons were trained to peck a key for access to food during response periods that started at different times after the beginning of the session. In these pigeons, GHB, its precursor gamma-butyrolactone (GBL), and the GABA(B) receptor agonists baclofen and 3-aminopropyl(methyl)phosphinic acid hydrochloride (SKF97541) decreased the rate of responding in a dose- and time-dependent manner. CGP35348 shifted the dose-response curve of each agonist to the right, but the magnitude of the shift differed among the agonists. Schild analysis yielded a pA(2) value of CGP35348 to antagonize GHB and GBL [i.e., 3.9 (3.7-4.2)] that was different (P = 0.0011) from the pA(2) value to antagonize baclofen and SKF97541 [i.e., 4.5 (4.4-4.7)]. This finding is further evidence that the GABA(B) receptor mechanisms mediating the effects of GHB and prototypical GABA(B) receptor agonists are not identical. A better understanding of the similarities and differences between these mechanisms, and their involvement in the therapeutic effects of GHB and baclofen, could lead to more effective medications with fewer adverse effects. PMID:19564487

Koek, Wouter; Mercer, Susan L; Coop, Andrew; France, Charles P



Identification of the 64K autoantigen in insulin-dependent diabetes as the GABA-synthesizing enzyme glutamic acid decarboxylase  

Microsoft Academic Search

The pancreatic islet beta-cell autoantigen of relative molecular mass 64,000 (64K), which is a major target of autoantibodies associated with the development of insulin-dependent diabetes mel-litus (IDDM) has been identified as glutamic acid decarboxylase, the biosynthesizing enzyme of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid). Pancreatic beta cells and a subpopulation of central nervous system neurons express high levels of this

Steinunn Baekkeskov; Henk-Jan Aanstoot; Stephan Christgai; Annette Reetz; Michele Solimena; Marilia Cascalho; Franco Folli; Hanne Richter-Olesen; Pietro-De Camilli



Immunohistochemical evidence for flupirtine acting as an antagonist on the N-methyl-D-aspartate and homocysteic acid-induced release of GABA in the rabbit retina.  


When rabbit retinas are exposed in vitro to specific excitatory amino acid receptor agonists certain GABAergic amacrine cells are activated to cause a release of GABA. The GABA that is not released can be detected by immunohistochemistry. Exposure of tissues to kainate or NMDA each caused a characteristic change in the GABA immunoreactivity. CNQX antagonised the kainate effect specifically while MK-801 counteracted the influence of NMDA. The effect produced by kainate was mimicked by domoic acid while the influence of homocysteic acid was identical with NMDA. Flupirtine alone did not influence the nature of the GABA immunoreactivity and so did not act as a kainate or NMDA agonist. However, flupirtine counteracted the influence produced by NMDA and homocysteic acid but had no effect on the kainate and domoic acid responses. Thus in this system flupirtine acts as an NMDA antagonist. PMID:7697370

Osborne, N N; Pergande, G; Block, F; Schwarz, M



A Glutamic Acid-Producing Lactic Acid Bacteria Isolated from Malaysian Fermented Foods  

PubMed Central

l-glutamaic acid is the principal excitatory neurotransmitter in the brain and an important intermediate in metabolism. In the present study, lactic acid bacteria (218) were isolated from six different fermented foods as potent sources of glutamic acid producers. The presumptive bacteria were tested for their ability to synthesize glutamic acid. Out of the 35 strains showing this capability, strain MNZ was determined as the highest glutamic-acid producer. Identification tests including 16S rRNA gene sequencing and sugar assimilation ability identified the strain MNZ as Lactobacillus plantarum. The characteristics of this microorganism related to its glutamic acid-producing ability, growth rate, glucose consumption and pH profile were studied. Results revealed that glutamic acid was formed inside the cell and excreted into the extracellular medium. Glutamic acid production was found to be growth-associated and glucose significantly enhanced glutamic acid production (1.032 mmol/L) compared to other carbon sources. A concentration of 0.7% ammonium nitrate as a nitrogen source effectively enhanced glutamic acid production. To the best of our knowledge this is the first report of glutamic acid production by lactic acid bacteria. The results of this study can be further applied for developing functional foods enriched in glutamic acid and subsequently ?-amino butyric acid (GABA) as a bioactive compound.

Zareian, Mohsen; Ebrahimpour, Afshin; Bakar, Fatimah Abu; Mohamed, Abdul Karim Sabo; Forghani, Bita; Ab-Kadir, Mohd Safuan B.; Saari, Nazamid



Lysophosphatidic Acid Stimulates Neurotransmitter-Like Conductance Changes that Precede GABA and L-Glutamate in Early, Presumptive Cortical Neuroblasts  

Microsoft Academic Search

During neurogenesis in the embryonic cerebral cortex, the clas- sical neurotransmitters GABA and L-glutamate stimulate ionic conductance changes in ventricular zone (VZ) neuroblasts. Ly- sophosphatidic acid (LPA) is a bioactive phospholipid produc- ing myriad effects on cells including alterations in membrane conductances (for review, see Moolenaar et al., 1995). Devel- opmental expression patterns of its first cloned receptor gene, lpA1

Adrienne E. Dubin; Tristram Bahnson; Joshua A. Weiner; Nobuyuki Fukushima; Jerold Chun



Detection of amino acid neurotransmitters by surface enhanced Raman scattering and hollow core photonic crystal fiber  

NASA Astrophysics Data System (ADS)

The present work explores the feasibility of using surface enhanced Raman scattering (SERS) for detecting the neurotransmitters such as glutamate (GLU) and gamma-amino butyric acid (GABA). These amino acid neurotransmitters that respectively mediate fast excitatory and inhibitory neurotransmission in the brain, are important for neuroendocrine control, and upsets in their synthesis are also linked to epilepsy. Our SERS-based detection scheme enabled the detection of low amounts of GLU (10-7 M) and GABA (10-4 M). It may complement existing techniques for characterizing such kinds of neurotransmitters that include high-performance liquid chromatography (HPLC) or mass spectrography (MS). This is mainly because SERS has other advantages such as ease of sample preparation, molecular specificity and sensitivity, thus making it potentially applicable to characterization of experimental brain extracts or clinical diagnostic samples of cerebrospinal fluid and saliva. Using hollow core photonic crystal fiber (HC-PCF) further enhanced the Raman signal relative to that in a standard cuvette providing sensitive detection of GLU and GABA in micro-litre volume of aqueous solutions.

Tiwari, Vidhu S.; Khetani, Altaf; Monfared, Ali Momenpour T.; Smith, Brett; Anis, Hanan; Trudeau, Vance L.



Contribution of GABA A and GABA B Receptors to the Discriminative Stimulus Produced by Gamma-Hydroxybutyric Acid  

Microsoft Academic Search

The present study examined the involvement of GABAA and GABAB receptors in the discriminative stimulus effects of gamma-hydroxybutyric acid (GHB). Rats were trained to discriminate either 300 or 700 mg\\/kg GHB IG from water using a T-maze, food-reinforced drug-discrimination procedure. The direct GABAB agonist, baclofen, substituted completely for both training doses of GHB; its potency to substitute for GHB increased

Carla Lobina; Roberta Agabio; Roberta Reali; Gian Luigi Gessa; Giancarlo Colombo



Reciprocal regulation of fatty acid release in the brain by GABA and glutamate.  


Several model systems have been used to test the hypothesis that the release of FFA in the brain is regulated by depolarization of neurons. This FFA release is likely the result of the activation of phospholipase A2. The increased neuronal activity that occurs due to synchronous depolarization during seizures causes activation of phospholipase A2. Decreasing neuronal activity by administering the anxiolytic, diazepam, appears to decrease the activity of phospholipase A2. The GABA antagonist, bicuculline, which causes depolarization by negating the hyperpolarizing tone imposed on neurons by GABA, causes FFA release in synaptosomes and in neurons in tissue culture. Likewise, the glutamate agonist, kainic acid, which depolarizes neurons by opening sodium channels, increases the activity of phospholipase A2. PC-specific phospholipase C, another enzyme important in the generation of the second messenger, DG, is also activated by depolarization. Several important questions remain to be answered. The site of FFA release, in terms of the pre-vs. postsynaptic membrane, is not clear, although the experiments with synaptosomes support the hypothesis that activation of phospholipase A2 may be an important regulator of presynaptic events. This idea has also been suggested by studies on the phenomenon of long-term potentiation, where free 20:4 or its metabolites may be involved in presynaptic facilitation of neurotransmitter release (Freeman et al., 1990; Massicotte et al., 1990; Williams et al., 1989; also see Dorman, this volume). The activation of the PI cycle and subsequent stimulation of protein kinase C may be a postsynaptic event important in the integration of inputs at the dendrite and soma or a presynaptic event involved in the modulation of neurotransmitter release (Taniyama et al., 1990; El-Fakahany et al., 1990; also see Nishizuka, this volume). Therefore the stimulation of a PC-specific phospholipase C, which is capable of generating large amounts of DG over a prolonged period of time (Exton, 1990; Martinson et al., 1990; Diaz-Laviada et al., 1990), could occur at either site. Another important question is the role of FFA and DG in affecting cell-cell signaling events, particularly with regard to ion fluxes. Modulation of an acetylcholine-linked K+ channel in the heart by FFA and their oxygenation products has been reported (Kim and Clapham, 1989). The cardiac muscarinic receptor is linked to a hyperpolarizing K+ channel via a G protein.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1353287

Birkle, D L



Extracellular hypothalamic gamma-aminobutyric acid (GABA) and L-glutamic acid concentrations in response to bicuculline in a genetic absence epilepsy rat model.  


The posterior part of the hypothalamus plays a vital role in the homeostatic processes of the internal environment, including blood pressure and heart rate regulation, by means of gamma-aminobutyric acid (GABA)ergic and glutamatergic neurotransmission. In this study we measured the extracellular levels of GABA and L-glutamic acid in the dorsomedial hypothalamic nucleus (DMH) and posterior hypothalamus (PH), following intracerebroventricular (i.c.v.) administration of bicuculline, a GABA(A)-receptor antagonist, in genetic absence epileptic rats from Strasbourg (GAERS), where heart rate, blood pressure, and EEG recordings were also collected simultaneously. The i.c.v. injection of bicuculline (0.3 nmol) produced no response in non-epileptic Wistar rats but caused an increase in mean arterial pressure in GAERS (P<0.01). Microdialysis experiments showed that L-glutamic acid increased in the DMH in GAERS after bicuculline administration (P<0.01). Additionally, extracellular GABA concentration decreased in the PH (P<0.05). Bicuculline suppressed the spike-and-wave discharges, the characteristic sign of absence seizures. All these results suggest that the bicuculline-induced blood pressure response is accompanied by changes in L-glutamic acid levels in the DMH and GABA levels in the PH, indicating a bicuculline hypersensitivity in the DMH and PH of GAERS that may make the GAERS display an altered mode of central cardiovascular regulation. These results suggest that the circuits affected in GAERS are not only restricted to the regions responsible for seizure generation but also present in the hypothalamus. PMID:18270469

Yananli, Hasan R; Terzio?lu, Berna; Goren, M Zafer; Aker, Rezzan G; Aypak, Cenk; Onat, Filiz Y



On the existence of two GABA pools associated with newly synthesized GABA and with newly taken up GABA in nerve terminals  

SciTech Connect

(/sup 14/C)Glutamic acid and (/sup 3/H)GABA were injected into the lateral ventricle of mouse and then (/sup 14/C)GABA and (/sup 3/H)GABA in synaptosomes isolated from the animals were analysed. The (/sup 14/C)GABA was interpreted to be newly synthesized GABA from (/sup 14/C)glutamic acid while the (/sup 3/H)GABA to be newly taken up GABA. We have obtained the following results: (1) when the animals were pretreated with aminooxyacetic acid and thus the GABA content in synaptosomes increased to about 2 times of the control level, only the (/sup 3/H)GABA was enhanced to 3 times of the control level without any change of (/sup 14/C)GABA, (2) the release of (/sup 14/C)GABA from synaptosomes by high K+ depolarization was 1.5 times greater than that of (/sup 3/H)GABA, (3) the releases of both (/sup 14/C)GABA and (/sup 3/H)GABA were increased in the presence of cold GABA, L-2,4-diaminobutyric acid or gamma-amino-beta-hydroxybutyric acid, but only slightly increased in the presence of beta-alanine. These results would suggest that newly synthesized GABA and newly taken up GABA localized individually in different pools, which might localize either in different nerve terminals or separately in the same nerve terminal.

Abe, M.; Matsuda, M.



Gestational changes of GABA levels and GABA binding in the human uterus  

SciTech Connect

The concentrations of gamma-aminobutyric acid (GABA), the activities of L-glutamate decarboxylase and GABA-transaminase, and the nature of the sodium-independent binding of GABA were examined in uterine tissue pieces obtained surgically from pregnant and non-pregnant women. GABA concentrations were reduced, while the activity of GABA-transaminase and the specific binding of (/sup 3/H)GABA significantly increased in specimens from pregnant subjects. These findings suggest some gestation-related functional role for the GABA system in the human uterus.

Erdoe, S.L.; Villanyi, P.; Laszlo, A.



Synthesis and evaluation of novel heteroaromatic substrates of GABA aminotransferase  

PubMed Central

Two principal neurotransmitters are involved in the regulation of mammalian neuronal activity, namely, ?-aminobutyric acid (GABA), an inhibitory neurotransmitter, and L-glutamic acid, an excitatory neurotransmitter. Low GABA levels in the brain have been implicated in epilepsy and several other neurological diseases. Because of GABA’s poor ability to cross the blood-brain barrier (BBB), a successful strategy to raise brain GABA concentrations is the use of a compound that does cross the BBB and inhibits or inactivates GABA aminotransferase (GABA-AT), the enzyme responsible for GABA catabolism. Vigabatrin, a mechanism-based inactivator of GABA-AT, is currently a successful therapeutic for epilepsy, but has harmful side effects, leaving a need for improved GABA-AT inactivators. Here, we report the synthesis and evaluation of a series of heteroaromatic GABA analogues as substrates of GABA-AT, which will be used as the basis for the design of novel enzyme inactivators.

Hawker, Dustin D.; Silverman, Richard B.



[Interstrain differences in the content of excitatory and inhibitory amino acids in the brain of DBA/2J, Balb/c and C57BL/6 mice: characteristics of the effect of a dipeptide antipsychotic drug dilept].  


We have performed a comparative study of the content of glutamate (Glu), aspartate (Asp), taurine (Tau), glycine (Gly) and gamma-amino-butyric acid (GABA) in the cortex, hippocampus, and striatum of the DBA/2J, Balb/c and C57BL/6 mice brain. The levels of Glu, Tau and GABA in DBA/2J hippocampus was lower than those in other experimental strains. These findings are consistent with published data on the specific neurophysiological properties of DBA/2J (neuroleptic sensitive prepulse inhibition, deficit), thus allowing this strain to be used in modeling schizophrenia. Taking into account these facts, in the next step we investigated the effects of dilept, the new neurotensine-derived dipeptide with antipsychotic activity (GZR-123, methyl ester of N-caproyl-L-prolyltyrosine), on the content of neurotransmitter acids in DBA/2J mice brain structures. In a dose of 0.8 mg/kg (i.p.) dilept induced a statistically significant increase in the levels of Glu, Tau and GABA in striatum of DBA/2J, as well as insignificant increase in the levels of these amino acids in the cortex. These effects are quite similar to those described for the parent peptide neurotensine, in case of its intracerebral administration. The results of our study prove the necessity of the further development of dilept as a potential antipsychotic drug. PMID:18819433

Shubenina, E B; Kudrin, V S; Klodt, P M; Pokrovski?, A A; Gudasheva, T A; Voronina, T A; Ostrovskaia, R U



Psychological stress-reducing effect of chocolate enriched with gamma-aminobutyric acid (GABA) in humans: assessment of stress using heart rate variability and salivary chromogranin A.  


We studied the psychological stress-reducing effect of chocolate enriched with gamma-aminobutyric acid (GABA), on stress induced by an arithmetic task using changes of heart rate variability (HRV) and salivary chromogranin A (CgA). Subjects ingested 10 g chocolate enriched with 28 mg GABA (GABA chocolate); 15 min after the ingestion, subjects were assigned an arithmetic task for 15 min. After the task, an electrocardiogram was recorded and saliva samples were collected. HRV was determined from the electrocardiogram, and the activity of the autonomic nervous system was estimated through HRV. The CgA concentration of all saliva samples, an index for acute psychological stress, was measured. From HRV, those taking GABA chocolate made a quick recovery to the normal state from the stressful state. The CgA value after the task in those taking GABA chocolate did not increased in comparison with that before ingestion. From these results, GABA chocolate was considered to have a psychological stress-reducing effect. PMID:19462324

Nakamura, H; Takishima, T; Kometani, T; Yokogoshi, H



Gamma-aminobutyric acid and glutamic acid levels in the auditory pathway of rats with chronic tinnitus: a direct determination using high resolution point-resolved proton magnetic resonance spectroscopy (1H-MRS)  

PubMed Central

Damage to the auditory system following high-level sound exposure reduces afferent input. Homeostatic mechanisms appear to compensate for the loss. Overcompensation may produce the sensation of sound without an objective physical correlate, i.e., tinnitus. Several potential compensatory neural processes have been identified, such as increased spontaneous activity. The cellular mechanisms enabling such compensatory processes may involve down-regulation of inhibitory neurotransmission mediated by ?-amino butyric acid (GABA), and/or up-regulation of excitatory neurotransmission, mediated by glutamic acid (Glu). Because central processing systems are integrated and well-regulated, compensatory changes in one system may produce reactive changes in others. Some or all may be relevant to tinnitus. To examine the roles of GABA and Glu in tinnitus, high resolution point-resolved proton magnetic resonance spectroscopy (1H-MRS) was used to quantify their levels in the dorsal cochlear nucleus (DCN), inferior colliculus (IC), medial geniculate body (MGB), and primary auditory cortex (A1) of rats. Chronic tinnitus was produced by a single high-level unilateral exposure to noise, and was measured using a psychophysical procedure sensitive to tinnitus. Decreased GABA levels were evident only in the MGB, with the greatest decrease, relative to unexposed controls, obtained in the contralateral MGB. Small GABA increases may have been present bilaterally in A1 and in the contralateral DCN. Although Glu levels showed considerable variation, Glu was moderately and bilaterally elevated both in the DCN and in A1. In the MGB Glu was increased ipsilaterally but decreased contralaterally. These bidirectional and region-specific alterations in GABA and Glu may reflect large-scale changes in inhibitory and excitatory equilibrium accompanying chronic tinnitus. The present results also suggest that targeting both neurotransmitter systems may be optimal in developing more effective therapeutics.

Brozoski, Thomas; Odintsov, Boris; Bauer, Carol



Gamma aminobutyric acid B and 5-hydroxy tryptamine 2A receptors functional regulation during enhanced liver cell proliferation by GABA and 5-HT chitosan nanoparticles treatment.  


Liver is one of the major organs in vertebrates and hepatocytes are damaged by many factors. The liver cell maintenance and multiplication after injury and treatment gained immense interest. The present study investigated the role of Gamma aminobutyric acid (GABA) and serotonin or 5-hydroxytryptamine (5-HT) coupled with chitosan nanoparticles in the functional regulation of Gamma aminobutyric acid B and 5-hydroxy tryptamine 2A receptors mediated cell signaling mechanisms, extend of DNA methylation and superoxide dismutase activity during enhanced liver cell proliferation. Liver injury was achieved by partial hepatectomy of male Wistar rats and the GABA and 5-HT chitosan nanoparticles treatments were given intraperitoneally. The experimental groups were sham operated control (C), partially hepatectomised rats with no treatment (PHNT), partially hepatectomised rats with GABA chitosan nanoparticle (GCNP), 5-HT chitosan nanoparticle (SCNP) and a combination of GABA and 5-HT chitosan nanoparticle (GSCNP) treatments. In GABA and 5-HT chitosan nanoparticle treated group there was a significant decrease (P<0.001) in the receptor expression of Gamma aminobutyric acid B and a significant increase (P<0.001) in the receptor expression of 5-hydroxy tryptamine 2A when compared to PHNT. The cyclic adenosine monophosphate content and its regulatory protein, presence of methylated DNA and superoxide dismutase activity were decreased in GCNP, SCNP and GSCNP when compared to PHNT. The Gamma aminobutyric acid B and 5-hydroxy tryptamine 2A receptors coupled signaling elements played an important role in GABA and 5-HT chitosan nanoparticles induced liver cell proliferation which has therapeutic significance in liver disease management. PMID:23748019

Shilpa, Joy; Pretty, Mary Abraham; Anitha, Malat; Paulose, Cheramadathikudyil Skaria



A mouse model for visualization of GABA(B) receptors.  


GABA(B) receptors are the G-protein-coupled receptors for the neurotransmitter gamma-aminobutyric acid (GABA). Receptor subtypes are based on the subunit isoforms GABA(B1a) and GABA(B1b), which combine with GABA(B2) subunits to form heteromeric receptors. Here, we used a modified bacterial artificial chromosome (BAC) containing the GABA(B1) gene to generate transgenic mice expressing GABA(B1a) and GABA(B1b) subunits fused to the enhanced green fluorescence protein (eGFP). We demonstrate that the GABA(B1)-eGFP fusion proteins reproduce the cellular expression patterns of endogenous GABA(B1) proteins in the brain and in peripheral tissue. Crossing the GABA(B1)-eGFP BAC transgene into the GABA(B1) (-/-) background restores pre and postsynaptic GABA(B) functions, showing that the GABA(B1)-eGFP fusion proteins substitute for the lack of endogenous GABA(B1) proteins. Finally, we demonstrate that the GABA(B1)-eGFP fusion proteins replicate the temporal expression patterns of native GABA(B) receptors in cultured neurons. These transgenic mice therefore provide a validated tool for direct visualization of native GABA(B) receptors. PMID:19603512

Casanova, Emilio; Guetg, Nicole; Vigot, Réjan; Seddik, Riad; Julio-Pieper, Marcela; Hyland, Niall P; Cryan, John F; Gassmann, Martin; Bettler, Bernhard



Genetic variability in glutamic acid decarboxylase genes: associations with post-traumatic seizures after severe TBI.  


Post traumatic seizures (PTS) occur frequently after traumatic brain injury (TBI). Since gamma-amino butyric acid (GABA) neurotransmission is central to excitotoxicity and seizure development across multiple models, we investigated how genetic variability for glutamic acid decarboxylase (GAD) influences risk for PTS. Using both a tagging and functional single nucleotide polymorphism (SNP) approach, we genotyped the GAD1 and GAD2 genes and linked them with PTS data, regarding time to first seizure, obtained for 257 adult subjects with severe TBI. No significant associations were found for GAD2. In the GAD1 gene, the tagging SNP (tSNP) rs3828275 was associated with an increased risk for PTS occurring <1 wk. The tSNP rs769391 and the functional SNP rs3791878 in the GAD1 gene were associated with increased PTS risk occurring 1 wk-6 mo post-injury. Both risk variants conferred an increased susceptibility to PTS compared to subjects with 0-1 risk variant. Also, those with haplotypes having both risk variants had a higher PTS risk 1 wk-6 mo post-injury than those without these haplotypes. Similarly, diplotype analysis showed those with 2 copies of the haplotype containing both risk alleles were at the highest PTS risk. These results implicate genetic variability within the GABA system in modulating the development of PTS. PMID:22840783

Darrah, Shaun D; Miller, Megan A; Ren, Dianxu; Hoh, Nichole Z; Scanlon, Joelle M; Conley, Yvette P; Wagner, Amy K



Coordinated Transcriptional Regulation of the unc-25 Glutamic Acid Decarboxylase and the unc-47 GABA Vesicular Transporter by the Caenorhabditis elegans UNC-30 Homeodomain Protein  

Microsoft Academic Search

An important aspect of the specification of neuronal fate is the choice of neurotransmitter. In Caenorhabditis elegans the neu- rotransmitter GABA is synthesized by the UNC-25 glutamic acid decarboxylase (GAD) and packaged into synaptic vesicles by the UNC-47 transporter. Both unc-25 and unc-47 are ex- pressed in 26 GABAergic neurons of five different types. Previ- ously, we have identified that

Catharine Eastman; H. Robert Horvitz; Yishi Jin


Effects of poly-?-glutamic acid on serum and brain concentrations of glutamate and GABA in diet-induced obese rats  

PubMed Central

Poly-gamma-glutamic acid (?-PGA) is a mucilaginous and biodegradable compound produced by Bacillus subtilis from fermented soybeans, and is found in the traditional Korean soy product, cheongkukjang. This study was carried out to evaluate the effects of ?-PGA from a food source on the concentration of the neurotransmitter GABA and its metabolic precursor glutamate in diet-induced obese rats. Eight-week old male Sprague-Dawley rats (n=60) were used. The rats were divided into two groups and obesity was induced by providing either a 10% control fat or 45% high fat diet for 5 weeks. The rats were then blocked into 6 groups and supplemented with a 0.1% ?-PGA diet for 4 weeks. After sacrifice, brain and serum GABA and glutamate concentrations were analyzed by high performance liquid chromatography with fluorometric detection. The rats fed the high fat diet had significantly increased body weights. ?-PGA supplementation significantly increased serum concentrations of glutamate and GABA in the control fat diet groups while this effect was not found in the high fat groups. In the brain, glutamate concentrations were significantly higher in the ?-PGA supplemented groups both in rats fed the normal and high fat diets than in the no ?-PGA controls. GABA concentrations showed the same tendency. The results indicated that ?-PGA intake increased GABA concentrations in the serum and brain. However, the effects were not shown in obese rats.

Lee, Hyesung; Chang, Moon-Jeong



gamma-Aminobutyric acid (GABA)- and barbiturate-mediated 36Cl- uptake in rat brain synaptoneurosomes: evidence for rapid desensitization of the GABA receptor-coupled chloride ion channel.  


"Desensitization" of the gamma-aminobutyric acid (GABA) receptor-coupled chloride ion channel was studied using an in vitro method for measuring chloride (Cl-) permeability in brain vesicles (synaptoneurosomes). Muscimol, a GABA agonist, stimulated 36Cl- uptake in rat cerebral cortical synaptoneurosomes in a concentration-dependent manner (EC50 7.3 +/- 0.5 microM), whereas pentobarbital stimulated 36Cl- uptake in a biphasic manner, indicated by a bell-shaped concentration-response relationship, with a maximal response at 500 microM (EC50 271 +/- 17 microM). Higher concentrations of pentobarbital led to progressively smaller stimulation of 36Cl- uptake and blocked muscimol-stimulated 36Cl- uptake. Lower concentrations of pentobarbital (100-200 microM), when added with muscimol, produced an additive effect in stimulating 36Cl- uptake, whereas even lower (subthreshold) concentrations of pentobarbital (50 microM) potentiated muscimol-stimulated 36Cl- uptake. Following continuous exposure of synaptoneurosomes (up to 20 min) to muscimol (50 microM) or pentobarbital (500 microM), the 36Cl- uptake response diminished to a new steady state level with a t1/2 of approximately 6 sec and 30 sec, respectively. The decrement in response to these agonists was dependent on both concentration and length of exposure. No decrement was observed in the ability of subthreshold concentrations of pentobarbital to enhance muscimol-stimulated 36Cl- uptake following prolonged (20 min) incubation. "Heterologous desensitization" between muscimol and pentobarbital was observed in experiments where either muscimol or pentobarbital was added to the vesicles following pretreatment with the other. These findings suggest that "desensitization" of the GABA receptor/Cl- ion channel may involve both the GABA and barbiturate recognition sites or a common effector component such as the ionophore itself. PMID:2430167

Schwartz, R D; Suzdak, P D; Paul, S M



Effect of Acceleration on Brain Metabolites Einfluss der Beschleunigung Auf Stoffwechselmetaboliten des Gehirns.  

National Technical Information Service (NTIS)

Acceleration effects (+Gz) were investigated. The fast glutamate depression can be explained only partly by the accompanying gamma amino butyric acid (GABA) increase, the concentration of which depends mainly on enzyme activity converting glutamate into G...

G. Schaefer



Amino acid signatures in the developing mouse retina.  


This study characterizes the developmental patterns of seven key amino acids: glutamate, ?-amino-butyric acid (GABA), glycine, glutamine, aspartate, alanine and taurine in the mouse retina. We analyze amino acids in specific bipolar, amacrine and ganglion cell sub-populations (i.e. GABAergic vs. glycinergic amacrine cells) and anatomically distinct regions of photoreceptors and Müller cells (i.e. cell bodies vs. endfeet) by extracting data from previously described pattern recognition analysis. Pattern recognition statistically classifies all cells in the retina based on their neurochemical profile and surpasses the previous limitations of anatomical and morphological identification of cells in the immature retina. We found that the GABA and glycine cellular content reached adult-like levels in most neurons before glutamate. The metabolic amino acids glutamine, aspartate and alanine also reached maturity in most retinal cells before eye opening. When the overall amino acid profiles were considered for each cell group, ganglion cells and GABAergic amacrine cells matured first, followed by glycinergic amacrine cells and finally bipolar cells. Photoreceptor cell bodies reached adult-like amino acid profiles at P7 whilst Müller cells acquired typical amino acid profiles in their cell bodies at P7 and in their endfeet by P14. We further compared the amino acid profiles of the C57Bl/6J mouse with the transgenic X-inactivation mouse carrying the lacZ gene on the X chromosome and validated this animal model for the study of normal retinal development. This study provides valuable insight into normal retinal neurochemical maturation and metabolism and benchmark amino acid values for comparison with retinal disease, particularly those which occur during development. PMID:24368173

Nivison-Smith, Lisa; Chua, Jacqueline; Tan, Seong-Seng; Kalloniatis, Michael



GABA, glycine, glutamate, aspartate and taurine in the perihypoglossal nuclei: an immunocytochemical investigation in the cat with particular reference to the issue of amino acid colocalization  

Microsoft Academic Search

The differential distribution of glutamate (Glu), aspartate (Asp), glycine (Gly), gamma-aminobutyric acid (GABA) and taurine (Tau) was investigated in the cat's perihypoglossal nuclei. Serial semi-thin (0.5 µm) sections through the perihypoglossal nuclei were incubated with antisera raised against the mentioned amino acids with the aim of studying possible co-localization. In each experiment different measures were undertaken in order to screen

K. Yingcharoen; E. Rinvik; J. Storm-Mathisen; O. P. Ottersen



Glucose and amino acid metabolism in rat brain during sustained hypoglycemia  

SciTech Connect

The metabolism of glucose in brains during sustained hypoglycemia was studied. (U-/sup 14/C)Glucose (20 microCi) was injected into control rats, and into rats at 2.5 hr after a bolus injection of 2 units of insulin followed by a continuous infusion of 0.2 units/100 g rat/hr. This regimen of insulin injection was found to result in steady-state plasma glucose levels between 2.5 and 3.5 mumol per ml. In the brains of control rats carbon was transferred rapidly from glucose to glutamate, glutamine, gamma-aminobutyric acid and aspartate and this carbon was retained in the amino acids for at least 60 min. In the brains of hypoglycemic rats, the conversion of carbon from glucose to amino acids was increased in the first 15 min after injection. After 15 min, the specific activity of the amino acids decreased in insulin-treated rats but not in the controls. The concentrations of alanine, glutamate, and gamma-amino-butyric acid decreased, and the concentration of aspartate increased, in the brains of the hypoglycemic rats. The concentration of pyridoxal-5'-phosphate, a cofactor in many of the reactions whereby these amino acids are formed from tricarboxylic acid cycle intermediates, was less in the insulin-treated rats than in the controls. These data provide evidence that glutamate, glutamine, aspartate, and GABA can serve as energy sources in brain during insulin-induced hypoglycemia.

Wong, K.L.; Tyce, G.M.



Putative TRP channel antagonists, SKF 96365, flufenamic acid and 2-APB, are non-competitive antagonists at recombinant human ?1?2?2 GABA(A) receptors.  


Although transient receptor potential (TRP) channel biology research has expanded rapidly in recent years, the field is hampered by the widely held, but relatively poorly investigated, belief that most of the pharmacological tools used to investigate TRP channel function may not be particularly selective for their intended targets. The objective of this study was therefore to determine if this was indeed the case by systematically evaluating the effects of three routinely used putative TRP channel antagonists, SKF 96365, flufenamic acid (FF) and 2-aminoethoxydiphenyl borate (2-APB) against one of the most widely expressed CNS receptor subtypes CNS, the human ?1?2?2 GABA(A) receptor. Using whole cell patch-clamp recording to record responses to rapidly applied GABA in the absence and presence of the three putative antagonists in turn we found that SKF 96365 (1-100 ?M) and FF (1-100 ?M) significantly inhibited GABA responses of recombinant human ?1?2?2 GABA(A) receptor stably expressed in HEK293 cells with IC(50) values of 13.4 ± 5.1 and 1.9 ± 1.4 ?M, respectively, suppressing the maximal response to GABA at all concentrations used in a manner consistent with a non-competitive mode of action. SKF 96365 and FF also both significantly reduced desensitisation and prolonged the deactivation kinetics of the receptors to GABA (1mM; P<0.05). 2-APB (10-1000 ?M) also inhibited responses to GABA at all concentrations used with an IC(50) value of 16.7 ± 5.4 ?M (n=3-5) but had no significant effect on the activation, desensitisation or deactivation kinetics of the GABA responses. Taken together this investigation revealed that these widely utilised TRP channel antagonists display significant 'off-target' effects at concentrations that are routinely used for the study of TRP channel function in numerous biological systems and as such, data which is obtained utilising these compounds should be interpreted with caution. PMID:22369768

Rae, M G; Hilton, J; Sharkey, J



Alpha-amino acid phenolic ester derivatives: novel water-soluble general anesthetic agents which allosterically modulate GABA(A) receptors.  


In the search for a novel water-soluble general anesthetic agent the activity of an alpha-amino acid phenolic ester lead, identified from patent literature, was markedly improved. In addition to improving in vivo activity in mice, good in vitro activity at GABA(A) receptors was also conferred. Within the series of compounds good enantioselectivity for both in vitro and in vivo activity was found, supporting a protein-mediated mechanism of action for anesthesia involving allosteric modulation of GABA(A) receptors. alpha-Amino acid phenolic ester 19, as the hydrobromide salt Org 25435, was selected for clinical evaluation since it retained the best overall anesthetic profile coupled with improved stability and water solubility. In the clinic it proved to be an effective intravenous anesthetic in man with rapid onset of and recovery from anesthesia at doses of 3 and 4 mg/kg. PMID:11606122

Anderson, A; Belelli, D; Bennett, D J; Buchanan, K I; Casula, A; Cooke, A; Feilden, H; Gemmell, D K; Hamilton, N M; Hutchinson, E J; Lambert, J J; Maidment, M S; McGuire, R; McPhail, P; Miller, S; Muntoni, A; Peters, J A; Sansbury, F H; Stevenson, D; Sundaram, H



Amino Acids and Sugars in the Gas Phase: Microwave Data for Astrochemistry  

NASA Astrophysics Data System (ADS)

Microwave spectroscopy, considered the most definitive gas phase structural probe, can distinguish between different conformational structures since they have unique spectroscopic constants and give separate rotational spectra. However it has been limited to molecular specimens having an appreciable vapor pressure. In general, molecules of biological importance have low vapor pressures and tend to undergo degradation upon heating. The combination of laser ablation with Fourier transform microwave spectroscopy in supersonic jets (LA-MB-FTMW) which overcomes the problems of thermal decomposition has rendered accessible the gas phase structural studies of these molecules. To date different ?-, ?- and ?-amino acids have been studied using this technique. Even in conformationally challenging systems the preferred conformations can be identified by rotational spectroscopy, as has been illustrated with the assignment of seven low-energy conformers in serine and threonine, six in cysteine and aspartic acid , and nine in ?-amino butyric (gaba). This technique has been successfully applied to the study of monosaccarides. Three conformers of the prototypes ?-D-glucose and ?-D-glucose have been characterized for the first time in the gas phase. After the first experimental observation of the monohydrated cluster of glycine, complexes between amino acids and nitrogen bases with water have also been investigated to obtain information on the changes induced in the conformational or tautomeric preferences by the addition of solvent molecules. The information given here is relevant for the unambiguous identification of these amino acids and sugars in the interstellar medium.

Mata, S.; Cabezas, C.; Varela, M.; Peña, I.; Perez, C.; Blanco, S.; Sanz, M. E.; Lopez, J. C.; Alonso, J. L.



Autoradiographic analysis of 3H-glutamate, 3H-dopamine, and 3H-GABA accumulation in rabbit retina after kainic acid treatment  

SciTech Connect

We have previously reported that exposure of isolated rabbit retina to 10(-3) M kainic acid produces profound morphological changes in specific retinal neurons (Hampton et al, 1981). We noted specific swelling of horizontal cell bodies and neurites, necrosis of cell bodies in the amacrine and ganglion cell layers, and swelling of elements in the inner plexiform layer. We now report a differential sensitivity to kainic acid of specific subclasses of amacrine cells autoradiographically labeled with 3H-glutamate, 3H-GABA, or 3H-dopamine. Three different effects were observed: (1) Labeling of neurons after incubation in 3H-glutamate was uniformly reduced while labeling of glia was much less affected. (2) The accumulation of 3H-dopamine was also decreased by kainic acid in two of the three labeled bands of the inner plexiform layer. The outermost labeled band was insensitive to kainic acid at the highest concentration tested (10(-2) M). These findings provide a basis for the subclassification of dopaminergic amacrine cells into at least two subclasses based on their sensitivity to kainic acid. (3) Kainic acid caused a dramatic increase in the labeling of GABAergic amacrine cell bodies and their terminals. This increased intensity may reflect a compensatory increase in uptake activity in response to kainic acid-induced depletion of endogenous GABA stores. These results confirm the highly toxic nature of kainic acid and demonstrate a high degree of specificity and complexity in its action in the retina.

Hampton, C.K.; Redburn, D.A.



Use of sourdough fermentation and pseudo-cereals and leguminous flours for the making of a functional bread enriched of gamma-aminobutyric acid (GABA).  


Lactobacillus plantarum C48 and Lactococcus lactis subsp. lactis PU1, previously selected for the biosynthesis of gamma-aminobutyric acid (GABA), were used for sourdough fermentation of cereal, pseudo-cereal and leguminous flours. Chickpea, amaranth, quinoa and buckwheat were the flours most suitable to be enriched of GABA. The parameters of sourdough fermentation were optimized. Addition of 0.1mM pyridoxal phosphate, dough yield of 160, inoculum of 5 x 10(7)CFU/g of starter bacteria and fermentation for 24h at 30 degrees C were found to be the optimal conditions. A blend of buckwheat, amaranth, chickpea and quinoa flours (ratio 1:1:5.3:1) was selected and fermented with baker's yeast (non-conventional flour bread, NCB) or with Lb. plantarum C48 sourdough (non-conventional flour sourdough bread, NCSB) and compared to baker's yeast started wheat flour bread (WFB). NCSB had the highest concentration of free amino acids and GABA (ca. 4467 and 504 mg/kg, respectively). The concentration of phenolic compounds and antioxidant activity of NCSB bread was the highest, as well as the rate of in vitro starch hydrolysis was the lowest. Texture analysis showed that sourdough fermentation enhances several characteristics of NCSB with respect to NCB, thus approaching the features of WFB. Sensory analysis showed that sourdough fermentation allowed to get good palatability and overall taste appreciation. PMID:20071045

Coda, Rossana; Rizzello, Carlo Giuseppe; Gobbetti, Marco



4-Aminobutyrate aminotransferase (GABA-transaminase) deficiency  

Microsoft Academic Search

4-Aminobutyrate aminotransferase (GABA-transaminase, GABA-T, EC deficiency (McKusick 137150), an inborn error of\\u000a GABA degradation, has until now been documented in only a single Flemish child. Compared to the other defects of GABA degradation,\\u000a succinic semialdehyde dehydrogenase (SSADH, EC deficiency with >150 patients (McKusick 271980) and pyridoxine-dependent\\u000a seizures with >100 patients ('putative'glutamic acid decarboxylase (GAD, EC deficiency; McKusick

L. K. Medina-Kauwe; A. J. Tobin; L. De Meirleir; J. Jaeken; C. A. J. M. Jakobs; W. L. Nyhan; K. M. Gibson



Fiat lux! Phylogeny and bioinformatics shed light on GABA functions in plants.  


The non-protein amino acid ?-aminobutyric acid (GABA) accumulates in plants in response to a wide variety of environmental cues. Recent data point toward an involvement of GABA in tricarboxylic acid (TCA) cycle activity and respiration, especially in stressed roots. To gain further insights into potential GABA functions in plants, phylogenetic and bioinformatic approaches were undertaken. Phylogenetic reconstruction of the GABA transaminase (GABA-T) protein family revealed the monophyletic nature of plant GABA-Ts. However, this analysis also pointed to the common origin of several plant aminotransferases families, which were found more similar to plant GABA-Ts than yeast and human GABA-Ts. A computational analysis of AtGABA-T co-expressed genes was performed in roots and in stress conditions. This second approach uncovered a strong connection between GABA metabolism and glyoxylate cycle during stress. Both in silico analyses open new perspectives and hypotheses for GABA metabolic functions in plants. PMID:23518583

Renault, Hugues



Effects of phenelzine and imipramine on the steady-state levels of mRNAs that encode glutamic acid decarboxylase (GAD67 and GAD65), the GABA transporter GAT1 and GABA transaminase in rat cortex  

Microsoft Academic Search

There is an increasing body of evidence suggesting that GABA plays an important role in the therapeutic effects of antidepressant\\/antipanic\\u000a drugs. Phenelzine and imipramine are efficacious in the treatment of depression and panic disorder and phenelzine has been\\u000a reported to elevate GABA levels while imipramine enhances GABA release in rat brains. In the present study, using a multiprobe\\u000a quantitative solution

Chien-Tsai Lai; Véronique A.-M. I. Tanay; Gregory J. R. Charrois; Glen B. Baker; A. N. Bateson



Cerebrospinal fluid GABA levels in various neurological and psychiatric diseases.  

PubMed Central

Cerebrospinal fluid gamma-aminobutyric acid (CSF-GABA) was analysed by radioreceptor assay in 16 normal controls and 84 patients with various neurological and psychiatric diseases. In patients with spinocerebellar degeneration, neuro-Behçet's syndrome and Parkinson's disease, CSF-GABA levels were decreased. On the other hand, increased CSF-GABA levels were detected in patients with meningitis.

Kuroda, H; Ogawa, N; Yamawaki, Y; Nukina, I; Ofuji, T; Yamamoto, M; Otsuki, S



GABA-transaminase and glutamic acid decarboxylase changes in the brain of rats treated with pyrithiamine  

Microsoft Academic Search

Pyrithiamine, a thiamine phosphokinase inhibitor, was fed to rats on a thiamine-deficient diet, producing weight loss, ataxia and loss of righting reflex in 10 days. Some rats were then sacrificed; others were returned to a normal diet, to be sacrificed only when their weight had returned to pre-experimental levels. Rats were sacrificed for assay of glutamic acid decarboxylase (GAD) and

Sharlene G. Thompson; Edith G. McGeer



Presynaptic GABA Band ?-hydroxybutyric acid-mediated mechanisms in generalized absence seizures  

Microsoft Academic Search

?-Hydroxybutyric acid (GHB) is a naturally occurring compound which has the ability to induce generalized absence seizures when given to animals. This effect of GHB may be blocked by either GHB or GABAB receptor antagonists. We sought to test the hypothesis that pre-synaptic GHB- and GABAB-mediated mechanisms in thalamus and cortex are operative in the GHB model of generalized absence

O. C. Snead



GABA B receptor-mediated increase of neurosteroids by ?-hydroxybutyric acid  

Microsoft Academic Search

Among the pharmacological actions of ?-hydroxybutyric acid (GHB), some may involve GABAA receptor-mediated mechanisms. GHB, however, fails to directly interact with sites for agonists and modulators on the GABAA receptor complex. We hypothesized that, in vivo, GHB may interfere with GABAA receptor function by altering the brain concentrations of the neurosteroids 3?-hydroxy-5?-pregnan-20-one (allopregnanolone, AP) and 3?,21-dihydroxy-5?-pregnan-20-one (allotetrahydrodeoxycorticosterone, THDOC), positive allosteric

M. L. Barbaccia; G. Colombo; D. Affricano; M. A. M. Carai; G. Vacca; S. Melis; R. H. Purdy; G. L. Gessa



Gamma-aminobutyric acid (GABA) and neuropeptides in neural areas mediating motion-induced emesis  

NASA Technical Reports Server (NTRS)

Immunocytochemical methods were employed to localize the neurotransmitter amino acid gamma-aminobutyric acid and the neuropeptides substance P and Met-enkephalin in the area postrema (AP), area subpostrema (ASP), nucleus of the tractus solitarius (NTS), dorsal motor nucleus of the vagus nerve (DMNV), and lateral vestibular nucleus (LVN). Glutamic acid decarboxylase immunoreactive (GAD-IR) terminals and fibers were observed in the AP and particularly in the ASP. A gradual decrease in the density of terminals was seen towards the solitary complex. The DMNV revealed irregularly scattered GAD-IR terminals within the neuropil or closely surrounding neuronal cell bodies. The LVN, particularly the dorsal division, showed numerous axon terminals which were mostly localize around large neurons and their proximal dendrites. Substance P immunoreactive (SP-IR) terminals and fibers showed high density in the solitary complex, in particular within the lateral division. The ASP showed medium to low density of SP-IR fibers and terminals. The AP exhibited a small number of fibers and terminals irregularly distributed. The DMNV revealed a high density of SP-IR terminals and fibers that were mainly concentrated in the periphery. Very few terminals were detected in the LVN. Met-enkephalin immunoreactive (Met-Enk-IR) fibers and terminals showed high density and uniform distribution in the DMNV. Scattered terminals and fibers were observed in the AP, ASP, and NTS (particularly the lateral division). The very few fibers were observed in the LVN surrounded the neuronal cell bodies. The present report is part of a study designed to investigate the interaction between neuropeptides and conventional neurotransmitters under conditions producing motion sickness and in the process of sensory-motor adaptation.

Damelio, F.; Daunton, Nancy G.; Fox, Robert A.



GABA[subscript A] Receptor Downregulation in Brains of Subjects with Autism  

ERIC Educational Resources Information Center

Gamma-aminobutyric acid A (GABA[subscript A]) receptors are ligand-gated ion channels responsible for mediation of fast inhibitory action of GABA in the brain. Preliminary reports have demonstrated altered expression of GABA receptors in the brains of subjects with autism suggesting GABA/glutamate system dysregulation. We investigated the…

Fatemi, S. Hossein; Reutiman, Teri J.; Folsom, Timothy D.; Thuras, Paul D.



Zinc ion enhances GABA tea-mediated oxidative DNA damage.  


GABA tea is a tea product that contains a high level of ?-aminobutyric acid (GABA). Previous study has demonstrated a synergistic effect of GABA tea and copper ions on DNA breakage. This study further explored whether zinc (Zn), a nonredox metal, modulated DNA cleavage induced by GABA tea extract. In a cell-free system, Zn(2+) significantly enhanced GABA tea extract and (-)-epigallocatechin-3-gallate (EGCG)- or H(2)O(2)-induced DNA damage at 24 h of incubation. Additionally, low dosages of GABA tea extract (1-10 ?g/mL) possessed pro-oxidant activity to increase H(2)O(2)/Zn(2+)-induced DNA cleavage in a dose-dependent profile. By use of various reactive oxygen scavengers, it was observed that glutathione, catalase, and potassium iodide effectively inhibited DNA degradation caused by the GABA tea extract/H(2)O(2)/Zn(2+) system. Moreover, the data showed that the GABA tea extract itself (0.5-5 mg/mL) could induce DNA cleavage in a long-term exposure (48 h). EGCG, but not the GABA tea extract, enhanced H(2)O(2)-induced DNA cleavage. In contrast, GABA decreased H(2)O(2)- and EGCG-induced DNA cleavage, suggesting that GABA might contribute the major effect on the antioxidant activity of GABA tea extract. Furthermore, a comet assay revealed that GABA tea extract (0.25 mg/mL) and GABA had antioxidant activity on H(2)O(2)-induced DNA breakage in human peripheral lymphocytes. Taken together, these findings indicate that GABA tea has the potential of both pro-oxidant and antioxidant. It is proposed that a balance between EGCG-induced pro-oxidation and GABA-mediated antioxidation may occur in a complex mixture of GABA tea extract. PMID:22264004

Chuang, Show-Mei; Wang, Hsueh-Fang; Hsiao, Ching-Chuan; Cherng, Shur-Hueih



Comparison of changes evoked by GABA (gamma-aminobutyric acid) and anoxia in [K+]o, [Cl-]o, and [Na+]o in stratum pyramidale and stratum radiatum of the guinea pig hippocampus.  


Ion-selective microelectrode recordings were made to assess a possible contribution of extracellular gamma-aminobutyric acid (GABA) accumulation to early responses evoked in the brain by anoxia and ischemia. Changes evoked by GABA or N2 in [K+]o, [Cl-]o, [Na+]o, and [TMA+]o were recorded in the cell body and dendritic regions of the stratum pyramidale (SP) and stratum radiatum (SR), respectively, of pyramidal neurons in CA1 of guinea pig hippocampal slices. Bath application of GABA (1-10 mM) for approximately 5 min evoked changes in [K+]o and [Cl-]o with respective EC50 levels of 3.8 and 4.1 mM in SP, and 4.7 and 5.6 mM in SR. In SP 5 mM GABA reversibly increased [K+]o and [Cl-]o and decreased [Na+]o; replacement of 95% O2 -5% CO2 by 95% N2 -5% CO2 for a similar period of time evoked changes which were for each ion in the same direction as those with GABA. In SR both GABA and N2 caused increases in [K+]o and decreases in [Cl-]o and [Na+]. The reduction of extracellular space, estimated from levels of [TMA+]o during exposures to GABA and N2, was 5-6% and insufficient to cause the observed changes in ion concentration. Ion changes induced by GABA and N2 were reversibly attenuated by the GABA(A) receptor antagonist bicuculline methiodide (BMI, 100 microM). GABA-evoked changes in [K+]o in SP and SR and [Cl-]o in SP were depressed by > or =90%, and of [Cl-]o in SR by 50%; N2-evoked changes in [K+]o in SP and SR were decreased by 70% and those of [Cl-]o by 50%. BMI blocked delta [Na+]o with both GABA and N2 by 20-30%. It is concluded that during early anoxia: (i) accumulation of GABA and activation of GABA(A) receptors may contribute to the ion changes and play a significant role, and (ii) responses in the dendritic (SR) regions are greater than and (or) differ from those in the somal (SP) layers. A large component of the [K+]o increase may involve a GABA-evoked Ca2+-activated gk, secondary to [Ca2+]i increase. A major part of [Cl-]o changes may arise from GABA-induced g(Cl) and glial efflux, with strong stimulation of active outward transport and anion exchange at SP, and inward Na+/K+/2Cl- co-transport at SR. Na+ influx is attributable mainly to Na+-dependent transmitter uptake, with only a small amount related to GABA(A) receptor activation. Although the release and (or) accumulation of GABA during anoxia might be viewed as potentially protectant, the ultimate role may more likely be an important contribution to toxicity and delayed neuronal death. PMID:10841433

Obrocea, G V; Morris, M E



4-Aminobutyrate aminotransferase (GABA-transaminase) deficiency.  


4-Aminobutyrate aminotransferase (GABA-transaminase, GABA-T, EC deficiency (McKusick 137150), an inborn error of GABA degradation, has until now been documented in only a single Flemish child. Compared to the other defects of GABA degradation, succinic semialdehyde dehydrogenase (SSADH, EC deficiency with > 150 patients (McKusick 271980) and pyridoxine-dependent seizures with > 100 patients ('putative' glutamic acid decarboxylase (GAD, EC deficiency; McKusick 266100), GABA-T deficiency is very rare. We present a summary of the clinical, biochemical, enzymatic and molecular findings on the index proband, and a recently identified second patient, with GABA-T deficiency. The phenotype in both included psychomotor retardation, hypotonia, hyperreflexia, lethargy, refractory seizures and electroencephalographic abnormalities. In an effort to elucidate the molecular basis of GABA-T deficiency, we isolated and characterized a 1.5 kb cDNA encoding human GABA-T, in addition to a 41 kb genomic clone which encompassed the GABA-T coding region. Standard methods of cloning and sequencing revealed an A-to-G transition at nucleotide 754 of the coding region in lymphoblast cDNAs derived from the index proband. This mutation resulted in substitution of an invariant arginine at amino acid 220 by lysine. Expression of the mutant in E. coli, followed by isolation and enzymatic characterization of the recombinant protein, revealed an enzyme whose Vmax was reduced to 25% of wild-type activity. The patient and father were heterozygous for this allele; the second allele in the patient remains unidentified. Genomic Southern analysis revealed that the second proband most likely harbours a deletion in the 3' region of the GABA-T gene. PMID:10407778

Medina-Kauwe, L K; Tobin, A J; De Meirleir, L; Jaeken, J; Jakobs, C; Nyhan, W L; Gibson, K M



Classification of GABA receptors in snail neurones.  


The present study aimed to elucidate the pharmacological features of GABA receptors on identifiable neurones of Achatina fulica Férussac by testing the effects of GABA analogues, muscimol, (+/-)-baclofen, (-)-beta-hydroxy GABA and those conformationally fixed in either the extended or folded form of carbon chain, such as trans- and cis-isomers of (+/-)-2-(aminomethyl)cyclopropane-1-carboxylic acid [+/-)-cyclo-GABA-extended and (+/-)-cyclo-GABA-folded) and trans-4-amino-crotonic acid (GABA-extended). The giant neurones used were TAN, d-LPeLN, v-VNAN, v-LCDN and RPeNLN. The minimum effective concentrations (MEC) of these compounds to produce hyper- or depolarization of the membrane potentials of the neurones were determined, and the effective potency quotient (EPQ) of each compound vis-à-vis that of GABA was calculated for each neurone. The GABA receptors in these neurones were classified into the muscimol I, muscimol II and baclofen types. The muscimol I (TAN and d-LPeLN) and muscimol II (v-VNAN and v-LCDN) receptors were respectively hyperpolarized and depolarized by GABA and muscimol but were insensitive to (+/-)-baclofen. These muscimol receptors are inferred to accept GABA in an extended form of its carbon chain, since muscimol, conformationally fixed in this form from C-1 to C-4, was quite effective. Muscimol was more potent on the muscimol II receptors (MEC: 3 X 10(-7)-3 X 10(-6) M; EPQ: 30-10) than on the muscimol I type (MEC: 3 X 10(-5)-10(-4) M; EPQ: 1-0.3).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2853063

Yongsiri, A; Funase, K; Takeuchi, H; Shimamoto, K; Ohfune, Y



Possible ameliorative effects of antioxidants on propionic acid / clindamycin - induced neurotoxicity in Syrian hamsters  

PubMed Central

Background Propionic acid (PA) found in some foods and formed as a metabolic product of gut bacteria has been reported to mimic/mediate the effects of autism. The present study was undertaken to compare the effect of orally administered PA with that of clindamycin-induced PA-microbial producers in inducing persistent biochemical autistic features in hamsters. The neuroprotective potency of carnosine and carnitine supplements against PA toxicity was also investigated. Methods The following groups were studied. 1. Control group, which received phosphate buffered saline orally, 2. Propionic acid treated group which were given PA at a dose of 250 mg/kg body weight/day for 3 days orally, 3. Clindamycin treated group which received a single dose of the antibiotic orogastrically at a dose of 30 mg/kg on the day of the experiment, 4. Carnosine-treated group which were given carnosine at a dose of 10 mg/kg body weight/day orally for one week, 5. Carnitine treated group given 50 mg/kg body weight/day carnitine orally daily for one week. Group 6. Carnosine followed by PA, Group 7. Carnitine followed by PA. Dopamine, adrenaline and noradrenaline, serotonin and Gamma amino-butyric acid (GABA) were measured in the cortex and medulla of the nine studied groups. Results PA administration caused significant decrease in the neurotransmitters in the brains of treated hamsters while clindamycin caused a significant decrease only in dopamine in hamster brains (cortex and medulla) and GABA in the cerebral cortex of the treated hamsters. Administration of carnosine and carnitine which are known antioxidants caused no significant changes in the levels of neurotransmitters when administered alone to hamsters. However when administered with PA both carnosine and carnitine restored the altered neurotransmitters to near normal levels. Conclusion Carnosine and carnitine may be used as supplements to protect against PA neurotoxicity.



Role of a ?-aminobutryic acid (GABA) receptor mutation in the evolution and spread of Diabrotica virgifera virgifera resistance to cyclodiene insecticides.  


The western corn rootworm, Diabrotica virgifera virgifera, is a damaging pest of cultivated corn that was controlled by applications of cyclodiene insecticides from the late 1940s until resistance evolved ?10 years later. Range expansion from the western plains into eastern USA coincides with resistance development. An alanine to serine amino acid substitution within the Rdl subunit of the gamma-aminobutyric acid (GABA) receptor confers resistance to cyclodiene insecticides in many species. We found that the non-synonymous single nucleotide polymorphism (SNP) G/T at the GABA receptor cDNA position 838 (G/T(838)) of D.?v. virgifera resulted in the alanine to serine change, and the codominant SNP allele T(838) was genetically linked to survival of beetles in aldrin bioassays. A phenotypic gradient of decreasing susceptibility from west to east was correlated with higher frequencies of the resistance-conferring T(838) allele in the eastern-most populations. This pattern exists in opposition to perceived selective pressures since the more eastern and most resistant populations probably experienced reduced exposure. The reasons for the observed distribution are uncertain, but historical records of the range expansion combined with the distribution of susceptible and resistant phenotypes and genotypes provide an opportunity to better understand factors affecting the species' range expansion. PMID:23841833

Wang, H; Coates, B S; Chen, H; Sappington, T W; Guillemaud, T; Siegfried, B D



Different control mechanisms of growth hormone (GH) secretion between gamma-amino- and gamma-hydroxy-butyric acid: neuroendocrine evidence in Parkinson's disease.  


The observation that baclofen stimulates growth hormone (GH) secretion in normal men, but not in parkinsonian patients led us to test the GH releasing effect of other gamma-amino-butyric acid (GABA)ergic agents with different mechanisms of action in Parkinson's disease. For this purpose 10 normal men and 10 de novo parkinsonian patients were tested with sodium valproate (800 mg PO), gamma-hydroxybutyric acid (GHB) (25 mg/kg body weight PO) and baclofen (10 mg PO). All drugs induced a significant increment in serum GH levels in the normal controls. On the other hand, GH secretion in parkinsonian patients did not change after baclofen or sodium valproate administration, whereas it showed normal responsiveness to GHB. These data suggest that the mechanism underlying the GH response to GHB is different from that (or those) mediating sodium valproate and/or baclofen action. In addition, the former, but not the latter mechanism appears to be preserved in the parkinsonian brain. PMID:9373886

Volpi, R; Chiodera, P; Caffarra, P; Scaglioni, A; Saccani, A; Coiro, V



The effect of intracerebroventricularly administered GABA on brain monoamine metabolism  

Microsoft Academic Search

Summary Intracerebroventricular injection of ?-aminobutyric acid (GABA) was performed in male rats and the brain monoamines, 5-hydroxyindoleacetic acid (5-HIAA), tyrosine and tryptophan levels were measured. GABA induced within 30 min a marked dose-dependent increase in the brain contents of dopamine (DA), serotonin (5-HT), tyrosine and tryptophan, while noradrenaline (NA) was lowered. Large doses of GABA, i.e. 1.5–3 mg\\/rat, were required

Bratati Biswas; Arvid Carlsson



Channel-mediated tonic GABA release from glia.  


Synaptic inhibition is based on both tonic and phasic release of the inhibitory transmitter ?-aminobutyric acid (GABA). Although phasic GABA release arises from Ca(2+)-dependent exocytosis from neurons, the mechanism of tonic GABA release is unclear. Here we report that tonic inhibition in the cerebellum is due to GABA being released from glial cells by permeation through the Bestrophin 1 (Best1) anion channel. We demonstrate that GABA directly permeates through Best1 to yield GABA release and that tonic inhibition is eliminated by silencing of Best1. Glial cells express both GABA and Best1, and selective expression of Best1 in glial cells, after preventing general expression of Best1, fully rescues tonic inhibition. Our results identify a molecular mechanism for tonic inhibition and establish a role for interactions between glia and neurons in mediating tonic inhibition. PMID:20929730

Lee, Soojung; Yoon, Bo-Eun; Berglund, Ken; Oh, Soo-Jin; Park, Hyungju; Shin, Hee-Sup; Augustine, George J; Lee, C Justin



The GABA A receptor subunits heterologously expressed in Xenopus oocytes.  


The ?-aminobutyric acid (GABA) A receptor is composed of a variety of subunits and combinations and shows a characteristic distribution in the CNS. To date, 20 subunits of the GABA A receptor have been cloned: ?1-6, ?1-4, ?1-3, ?, ?, ? , ?, and ?1-3. Oocyte of Xenopus laevis is one of the most frequently used heterologous expression systems, which are used to design and analyze specific combinations of GABA A receptor subunits. In oocytes, a certain GABA A receptor function is studied only by comparing the amplitude of the response to GABA and other drugs by physiological and pharmacological methods. According to the studies on Xenopus laevis oocytes, the ?1?2?2S receptor combination is mostly used. The ?1-containing receptors mediate sedative and anticonvulsant acts. The results of studies on oocytes show that PKA, NKCC1, P2X3 receptors, and GABA A receptor-associated protein, etc., are existing systems that show different reactivity to the GABA A receptors. The GABA A receptor subunits contain distinct binding sites for BZDs, neurosteroids, general anesthetics, etc., which are responsible for the numerous functions of the GABA A receptor. A variety of other drugs, such as topiramate, TG41, (+)- and (-)-borneol, apigenin, and 6-methylflavone could also have modulatory effects on the GABA A receptors. Some of the different models and hypotheses on GABA A receptor structure and function have been achieved by using the two-electrode voltage clamp method in oocytes. PMID:23373649

Abdullah, Jafri Malin; Zhang, Jingli



Amino acid biogeochemistry and organic matter degradation state across the Pakistan margin oxygen minimum zone  

NASA Astrophysics Data System (ADS)

To assess whether the oxygen minimum zone (OMZ) across the Pakistan Margin causes differences in the lability of sedimentary organic matter, sediments were collected in the core of the OMZ, in the upper and lower transition zones and below the OMZ. Sediment samples were analysed for total nitrogen (TN) and organic carbon (OC) contents, mineral surface area (SA), and total hydrolysable amino acids (THAA) and enzymatically hydrolysable amino acids (EHAA). OC contents and organic carbon per unit of mineral surface area (OC/SA) values were clearly elevated in the core and lower OMZ transition zone. These sediments also contained more labile sedimentary organic matter, as discerned by higher concentrations of THAA and the contribution of N in THAA to TN. A protein amino acid-based degradation index revealed that all sedimentary organic matter has undergone significant degradation, but sediments in the upper OMZ transition zone and below the OMZ are more degraded than inside the OMZ. Changes in amino acid composition during diagenesis are attributed to a combination of factors: (1) selective preservation in which amino acids in cell walls are better preserved than amino acids in cell plasma, (2) formation and accumulation of bacterially derived organic matter; there were relatively more living bacteria in the core of the OMZ and an accumulation of peptidoglycan-derived amino acids in degraded sediments in the upper OMZ transition zone and below the OMZ, and (3) bacterial transformation, as the molar percentages of bacterial transformation products ?-alanine (Bala), ?-amino butyric acid (Gaba), and ornithine (Orn), increased with increasing degradation.

Vandewiele, Sandra; Cowie, Greg; Soetaert, Karline; Middelburg, Jack J.



Amino acid release from the intermediate medial hyperstriatum ventrale (IMHV) of day-old chicks following a one-trial passive avoidance task.  


Indirect evidence has implicated glutamate and gamma-amino butyric acid in memory formation for one-trial passive avoidance learning. We have further examined this by following the time course of glutamate and gamma-amino butyric acid release from slices prepared from the intermediate medial hyperstriatum ventrale of day-old chicks (Ross 1 Chunky) trained to avoid a bead covered in the aversant methylanthranilate. At various times after training, slices of left and right intermediate medial hyperstriatum ventrale were incubated in medium containing 50 mM potassium chloride and amino acid release was determined. Thirty minutes after training there was a bilateral increase in calcium-dependent glutamate release in slices from methylanthranilate-trained chicks compared to those trained to peck water. This increase was sustained until 1 h in the left hyperstriatum when an increase in calcium-dependent gamma-amino butyric acid release was also apparent. Glutamate uptake was also enhanced in left hyperstriatum (30 and 60 min) and in the right at 30 min. In the right intermediate medial hyperstriatum ventrale of methylanthranilate birds glutamate release was increased from 3 to 6.5 h and gamma-amino butyric acid at 6.5 h: a time that corresponded to the mobilization of a late process required if long-term memory was to be formed. These results confirm that the amino acids glutamate and gamma-amino butyric acid are released from the intermediate hyperstriatum ventrale in a calcium-dependent, neurotransmitter-like manner. Furthermore, changes in the release of these two amino acids accompany memory formation for a one-trial learning task in the day-old chick. PMID:11848718

Daisley, Jonathan N; Rose, Steven P R



Pharmacological characterization of GABA receptors mediating vasodilation of verebral arteries in vitro.  


GABA (gamma-aminobutyric acid) produced a dose-dependent dilation of isolated cat and dog cerebral artery segments which had been given an active, tonic contraction by either prostaglandin F2 alpha or serotonin. No effect of GABA on extracranial blood vessels was observed. The GABA-induced dilation could be blocked in a dose-dependent manner by either bicuculline or picrotoxin. The latter agent appeared to act as a competitive antagonist. GABA agonists muscimol, imidazoleacetic acid, delta-aminovaleric acid, (+/-)gamma-amino-beta-hydroxybutyric acid, and beta-alanine also relaxed actively contracted cerebral arteries dose-dependently. The relative potency of these agonists was consistent with that established for GABA receptors on neurons and invertebrate striated muscle. GABA was also tested on two human cerebral arteries and found to cause a small dilation. The results support the existence of a cerebrovascular GABA receptor which may mediate an interaction between GABA and the cerebral circulatory system. PMID:226209

Edvinsson, L; Krause, D N



CSF and plasma GABA levels in Parkinson's disease  

PubMed Central

CSF gamma-aminobutyric acid (GABA) levels were reduced in patients with idiopathic Parkinson's disease when compared with age matched controls, but the difference was not significant. However, when the Parkinsonian patients were subdivided, CSF GABA levels were lower in the levodopa treated group than in the untreated group and the controls. There was no difference in plasma GABA levels between Parkinsonian patients and controls.

Abbott, RJ; Pye, IF; Nahorski, SR



Cloning and Expression of a Rat Brain GABA Transporter  

Microsoft Academic Search

A complementary DNA clone (designated GAT-1) encoding a transporter for the neurotransmitter gamma-aminobutyric acid (GABA) has been isolated from rat brain, and its functional properties have been examined in Xenopus oocytes. Oocytes injected with GAT-1 synthetic messenger RNA accumulated [^3H]GABA to levels above control values. The transporter encoded by GAT-1 has a high affinity for GABA, is sodium- and chloride-dependent,

John Guastella; Nathan Nelson; Hannah Nelson; Linda Czyzyk; Shoshi Keynan; May C. Miedel; Norman Davidson; Henry A. Lester; Baruch I. Kanner



Production of GABA by cultured hippocampal glial cells.  


Medium conditioned by cultured hippocampal glial contains an inhibitory factor that can hyperpolarize and suppress neuronal activity. Using biochemistry, electrophysiology, pharmacology, and mass spectrometry, we have identified the inhibitory factor as GABA (gamma-aminobutyric acid). Like GABA, the inhibitory factor increases chloride and potassium currents in neurons, which can be blocked by bicuculline. Mass spectrometry analysis of conditioned medium reveals peaks that are identical to that for GABA. Up to 500 micromolar GABA is found in conditioned medium from glial cultures. No GABA is found in conditioned medium from neuronal cultures. Hippocampal glia make much more GABA than cortical glia or glia from other brain regions. It is not clear how hippocampal glia synthesize GABA. Although they express GAD mRNA and adding glutamate to the culture medium increases the amount of GABA produced, other data suggest that glia do not use GAD to make GABA. Identifying the mechanism(s) by which GABA is produced by hippocampal glia would help clarify its role in modulating neuronal activity in the brain. PMID:15145543

Jow, Flora; Chiu, Doreen; Lim, Heng-Keang; Novak, Tom; Lin, Stephen



Selected biomarkers as predictive tools in testing efficacy of melatonin and coenzyme Q on propionic acid - induced neurotoxicity in rodent model of autism  

PubMed Central

Background Exposures to environmental toxins are now thought to contribute to the development of autism spectrum disorder. Propionic acid (PA) found as a metabolic product of gut bacteria has been reported to mimic/mediate the neurotoxic effects of autism. Results from animal studies may guide investigations on human populations toward identifying environmental contaminants that produce or drugs that protect from neurotoxicity. Forty-eight young male Western Albino rats were used in the present study. They were grouped into six equal groups 8 rats each. The first group received a neurotoxic dose of buffered PA (250 mg/Kg body weight/day for 3 consecutive days). The second group received only phosphate buffered saline (control group). The third and fourth groups were intoxicated with PA as described above followed by treatment with either coenzyme Q (4.5 mg/kg body weight) or melatonin (10 mg/kg body weight) for one week (therapeutically treated groups). The fifth and sixth groups were administered both compounds for one week prior to PA (protected groups). Heat shock protein70 (Hsp70), Gamma amino-butyric acid (GABA), serotonin, dopamine, oxytocin and interferon ?-inducible protein 16 together with Comet DNA assay were measured in brain tissues of the six studied groups. Results The obtained data showed that PA caused multiple signs of brain toxicity revealed in depletion of GABA, serotonin, and dopamine, are which important neurotransmitters that reflect brain function, interferon ?-inducible protein 16 and oxytocin. A high significant increase in tail length, tail DNA% damage and tail moment was reported indicating the genotoxic effect of PA. Administration of melatonin or coenzyme Q showed both protective and therapeutic effects on PA–treated rats demonstrated in a remarkable amelioration of most of the measured parameters. Conclusion In conclusion, melatonin and coenzyme Q have potential protective and restorative effects against PA-induced brain injury, confirmed by improvement in biochemical markers and DNA double strand breaks.



Effects of vigabatrin, an irreversible GABA transaminase inhibitor, on ethanol reinforcement and ethanol discriminative stimuli in mice.  


We tested the hypothesis that the irreversible ?-amino butyric acid transaminase inhibitor, ?-vinyl ?-amino butyric acid [vigabatrin (VGB)], would reduce ethanol reinforcement and enhance the discriminative-stimulus effect of ethanol, effectively reducing ethanol intake. The present studies used adult C57BL/6J (B6) mice in well-established operant, two-bottle choice consumption, locomotor activity, and ethanol discrimination procedures to comprehensively examine the effects of VGB on ethanol-supported behaviors. VGB dose-dependently reduced operant responding for ethanol and ethanol consumption for long periods of time. Importantly, a low dose (200 mg/kg) of VGB was selective for reducing ethanol responding without altering the intake of food or water reinforcement. Higher VGB doses (>200mg/kg) reduced ethanol intake, but also significantly increased water consumption and, more modestly, increased food consumption. Although not affecting locomotor activity on its own, VGB interacted with ethanol to reduce the stimulatory effects of ethanol on locomotion. Finally, VGB (200 mg/kg) significantly enhanced the discriminative-stimulus effects of ethanol as evidenced by significant leftward and upward shifts in ethanol generalization curves. Interestingly, VGB treatment was associated with slight increases in blood ethanol concentrations. The reduction in ethanol intake by VGB appears to be related to the ability of VGB to potentiate the pharmacological effects of ethanol. PMID:22336593

Griffin, William C; Nguyen, Shaun A; Deleon, Christopher P; Middaugh, Lawrence D



GABA (?-aminobutyric acid), a non-protein amino acid counters the ?-adrenergic cascade-activated oncogenic signaling in pancreatic cancer: a review of experimental evidence.  


GABA is a bioactive constituent of fruits, vegetables, cereals and is believed to play a role in defense against stress in plants. In animals, it acts as an inhibitory neurotransmitter in brain while also expressed in non-neuronal cells. Studies have implicated the regulator of fight or flight stress responses, ?-AR signaling cascade, as mediators of cancer growth and progression in in vitro and in vivo models of pancreatic malignancies. Pancreatic cancer is the fourth leading cause of cancer mortality in western countries. This malignancy is generally unresponsive to conventional radio- and chemotherapy, resulting in mortality rate near 100% within 6 months of diagnosis. We review a series of experiments from our laboratory and those of others examining the contribution of this signaling network to pancreatic and other human malignancies. Stimulation of the ?-adrenergic receptor by lifestyle and environmental factors, as well as a pre-existing risk of neoplasm, activates downstream effector molecules that lead to pro-oncogenic signaling and thereby aid cancer growth. GABAergic signaling mediated by the serpentine receptor GABA(B) acts as an antagonist to ?-adrenergic cascade by intercepting adenylyl cyclase. These evidences enhance the pharmacological value of human diets rich in GABA for use as an adjuvant to standard therapies. PMID:21805621

Al-Wadei, Hussein A N; Ullah, Mohammad F; Al-Wadei, Mohammed



GABA signalling during development: new data and old questions  

Microsoft Academic Search

In addition to being the major inhibitory neurotransmitter, %-aminobutyric acid (GABA) is thought to play a morphogenetic role in embryonic development. During the last decade, considerable progress has been made in elucidating the molecular mechanisms involved in GABA synthesis and biological action. The present review is an attempt to summarise recent results on the ontogeny of the different components of

Patricia Varju; Zoya Katarova; Emilia Madarász; Gábor Szabó



Modulation by GABA of neuroplasticity in the central and peripheral nervous system  

Microsoft Academic Search

Apart from being a prominent (inhibitory) neurotransmitter that is widely distributed in the central and peripheral nervous system, ?-aminobutyric acid (GABA) has turned out to exert trophic actions. In this manner GABA may modulate the neuroplastic capacity of neurons and neuron-like cells under various conditions in situ and in vitro. In the superior cervical ganglion (SCG) of adult rat, GABA

J. R. Wolff; F. Joó; P. Kfisa



Development and Validation of a HPTLC Method for Simultaneous Estimation of L-Glutamic Acid and ?-Aminobutyric Acid in Mice Brain.  


A new robust, simple and economic high performance thin layer chromatographic method was developed for simultaneous estimation of L-glutamic acid and ?-amino butyric acid in brain homogenate. The high performance thin layer chromatographic separation of these amino acid was achieved using n-butanol:glacial acetic acid:water (22:3:5 v/v/v) as mobile phase and ninhydrin as a derivatising agent. Quantitation of the method was achieved by densitometric method at 550 nm over the concentration range of 10-100 ng/spot. This method showed good separation of amino acids in the brain homogenate with Rf value of L-glutamic acid and ?-amino butyric acid as 21.67±0.58 and 33.67±0.58, respectively. The limit of detection and limit of quantification for L-glutamic acid was found to be 10 and 20 ng and for ?-amino butyric acid it was 4 and 10 ng, respectively. The method was also validated in terms of accuracy, precision and repeatability. The developed method was found to be precise and accurate with good reproducibility and shows promising applicability for studying pathological status of disease and therapeutic significance of drug treatment. PMID:24591747

Sancheti, J S; Shaikh, M F; Khatwani, P F; Kulkarni, Savita R; Sathaye, Sadhana



Lactic acid bacteria contribution to gut microbiota complexity: lights and shadows.  


Lactic Acid Bacteria (LAB) are ancient organisms that cannot biosynthesize functional cytochromes, and cannot get ATP from respiration. Besides sugar fermentation, they evolved electrogenic decarboxylations and ATP-forming deiminations. The right balance between sugar fermentation and decarboxylation/deimination ensures buffered environments thus enabling LAB to survive in human gastric trait and colonize gut. A complex molecular cross-talk between LAB and host exists. LAB moonlight proteins are made in response to gut stimuli and promote bacterial adhesion to mucosa and stimulate immune cells. Similarly, when LAB are present, human enterocytes activate specific gene expression of specific genes only. Furthermore, LAB antagonistic relationships with other microorganisms constitute the basis for their anti-infective role. Histamine and tyramine are LAB bioactive catabolites that act on the CNS, causing hypertension and allergies. Nevertheless, some LAB biosynthesize both gamma-amino-butyrate (GABA), that has relaxing effect on gut smooth muscles, and beta-phenylethylamine, that controls satiety and mood. Since LAB have reduced amino acid biosynthetic abilities, they developed a sophisticated proteolytic system, that is also involved in antihypertensive and opiod peptide generation from milk proteins. Short-chain fatty acids are glycolytic and phosphoketolase end-products, regulating epithelial cell proliferation and differentiation. Nevertheless, they constitute a supplementary energy source for the host, causing weight gain. Human metabolism can also be affected by anabolic LAB products such as conjugated linoleic acids (CLA). Some CLA isomers reduce cancer cell viability and ameliorate insulin resistance, while others lower the HDL/LDL ratio and modify eicosanoid production, with detrimental health effects. A further appreciated LAB feature is the ability to fix selenium into seleno-cysteine. Thus, opening interesting perspectives for their utilization as antioxidant nutraceutical vectors. PMID:22919677

Pessione, Enrica



GABA(C) receptors in neuroendocrine gut cells: a new GABA-binding site in the gut.  


Although GABA(C) receptors play a crucial role in the mammalian central nervous system, their functional expression in peripheral tissues has not yet been studied. Using the gut neuroendocrine tumor cell line STC-1 as a model, we provide first evidence for the functional expression of GABA(C) receptors in the gut: mRNAs of the GABA(C) receptor subunits rho1 and rho2 were detected in STC-1 cells by reverse transcription polymerase chain reaction (RT-PCR). Applying anti-rho-antibodies, specific immunostaining for GABA(C) receptors was observed. For functional characterization, the effects of GABA(C) receptor activation on [Ca2+]i and hormone secretion were studied. The selective GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA) induced dose-dependent increases both of [Ca2+]i and of hormone (cholecystokinin) secretion. The stimulatory effects of CACA were antagonized by the GABA(C) receptor blockers (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) and 3-aminopropyl(methyl)phosphinic acid (3-APMPA). These results demonstrate that GABA(C) receptors play an important role in neuroendocrine gastrointestinal secretion. PMID:11211116

Jansen, A; Hoepfner, M; Herzig, K H; Riecken, E O; Scherübl, H



Spatial distributions of GABA receptors and local inhibition of Ca2+ transients studied with GABA uncaging in the dendrites of CA1 pyramidal neurons.  


GABA (?-amino-butylic acid)-mediated inhibition in the dendrites of CA1 pyramidal neurons was characterized by two-photon uncaging of a caged-GABA compound, BCMACM-GABA, and one-photon uncaging of RuBi-GABA in rat hippocampal slice preparations. Although we found that GABA(A)-mediated currents were diffusely distributed along the dendrites, currents elicited at the branch points of the apical dendritic trunk were approximately two times larger than those elsewhere in the dendrite. We examined the inhibitory action of the GABA-induced currents on Ca(2+) transients evoked with a single back-propagating action potential (bAP) in oblique dendrites. We found that GABA uncaging selectively inhibited the Ca(2+) transients in the region adjacent (<20 µm) to the uncaging site, and that GABA uncaging was effective only within a short period after bAP (<20 ms). The strength of inhibition was linearly related to the amplitudes of the GABA currents, suggesting that the currents inhibited a sustained, subthreshold after-depolarization without preventing propagation of bAP. GABA uncaging at the dendritic branch points inhibited Ca(2+) transients farther into dendritic branches (>20 µm). Our data indicate that GABA inhibition results in spatially confined inhibition of Ca(2+) transients shortly after bAP, and suggest that this effect is particularly potent at the dendritic branch points where GABA receptors cluster. PMID:21799926

Kanemoto, Yuya; Matsuzaki, Masanori; Morita, Susumu; Hayama, Tatsuya; Noguchi, Jun; Senda, Naoko; Momotake, Atsuya; Arai, Tatsuo; Kasai, Haruo



Prediction of GABA A receptor proteins using the concept of Chou's pseudo-amino acid composition and support vector machine  

Microsoft Academic Search

The amino acid gamma-aminobutyric-acid receptors (GABAARs) belong to the ligand-gated ion channels (LGICs) superfamily. GABAARs are highly diverse in the central nervous system. These channels play a key role in regulating behavior. As a result, the prediction of GABAARs from the amino acid sequence would be helpful for research on these receptors. We have developed a method to predict these

Hassan Mohabatkar; Majid Mohammad Beigi; Abolghasem Esmaeili



The GABA dose/conductance relationship on lobster muscle.  


A quantitative study was made of the action of GABA, some structurally-related agonists and antagonists on the dactyl opener muscle fibres of the lobster. It was concluded that the GABA dose/conductance relationship was better described by a two independent binding-site receptor model (with KII = 30 microM) than by a single-site or a two-site high co-operativity model. The dose/conductance curves for gamma-amino-beta-hydroxybutyric acid (GABOB), delta-aminovaleric acid (DAV) and piperazine indicated 'full' agonist behaviour, whereas those for guanidoacetic acid (GuAc) indicated a partial agonist action. beta-guanidinopropionic acid (beta-GP) and gamma-guanidinobutyric acid (gamma-GB) behaved as weak competitive GABA antagonists. Bicuculline was found to antagonize GABA non-competitively on the lobster as in the crayfish, whereas picrotoxin appeared to act in a 'mixed' antagonistic fashion. PMID:547064

Constanti, A



Systemic Administration of Kainic Acid Increases GABA Levels in Perfusate from the Hippocampus of Rats 'In vivo'.  

National Technical Information Service (NTIS)

The ventral hippocampi of male, Fischer-344 rats were implanted with microdialysis probes and the effects of systemically administered kainic acid (KA) (8 mg/kg, s.c.) on the in vivo release of amino acids were measured for four hours after administration...

W. Q. Zhang B. C. Rogers P. Tandon P. M. Hudson T. J. Sobotka



Agonist pharmacology of two Drosophila GABA receptor splice variants.  


1. The Drosophila melanogaster gamma-aminobutyric acid (GABA) receptor subunits, RDLac and DRC 17-1-2, form functional homo-oligomeric receptors when heterologously expressed in Xenopus laevis oocytes. The subunits differ in only 17 amino acids, principally in regions of the N-terminal domain which determine agonist pharmacology in vertebrate ionotropic neurotransmitter receptors. A range of conformationally restricted GABA analogues were tested on the two homo-oligomers and their agonists pharmacology compared with that of insect and vertebrate iontropic GABA receptors. 2. The actions of GABA, isoguvacine and isonipecotic acid on RDLac and DRC 17-1-2 homo-oligomers were compared, by use of two-electrode voltage-clamp. All three compounds were full agonists of both receptors, but were 4-6 fold less potent agonists of DRC 17-1-2 homo-oligomers than of RDLac. However, the relative potencies of these agonists on each receptor were very similar. 3. A more complete agonist profile was established for RDLac homo-oligomers. The most potent agonists of these receptors were GABA, muscimol and trans-aminocrotonic acid (TACA), which were approximately equipotent. RDLac homo-oligomers were fully activated by a range of GABA analogues, with the order of potency: GABA > ZAPA ((Z)-3-[(aminoiminomethyl)thio]prop-2-enoic acid) > isoguvacine > imidazole-4-acetic acid > or = isonipecotic acid > or = cis-aminocrotonic acid (CACA) > beta-alanine. 3-Aminopropane sulphonic acid (3-APS), a partial agonist of RDLac homo-oligomers, was the weakest agonist tested and 100 fold less potent than GABA. 4. SR95531, an antagonist of vertebrate GABAA receptors, competitively inhibited the GABA responses of RDLac homo-oligomers, which have previously been found to insensitive to bicuculline. However, its potency (IC50 500 microM) was much reduced when compared to GABAA receptors. 5. The agonist pharmacology of Drosophila RDLac homo-oligomers exhibits aspects of the characteristic pharmacology of certain native insect GABA receptors which distinguish them from vertebrate GABA receptors. The high potency and efficacy of isoguvacine and ZAPA distinguishes RDLac homo-oligomers from bicuculline-insensitive vertebrate GABAC receptors, while the low potency of SR95531 and 3-APS distinguishes them from GABAA receptors. The differences in the potency of agonists on RDLac and DRC 17-1-2 homo-oligomers observed in the present study may assist in identification of further molecular determinants of GABA receptor function. PMID:8982504

Hosie, A M; Sattelle, D B



Incorporation of Different Bridge Length Linkers in Enzyme and Its Use in the Preparation of Enzyme Conjugates for Immunoassay  

Microsoft Academic Search

An enzyme horseradish peroxidase (HRP), as a starting material, has been used to introduce different bridge length linkers, and its use in the preparation of enzyme conjugates for immunoassay is described. HRP was conjugated to adipic acid dihydrazide (ADH), gamma amino butyric acid (GABA), followed by ADH and 6?amino caproic acid (6ACA) followed by ADH. The different bridge length linkers?incorporated

Tulsidas G. Shrivastav



GABA transporter subtype 1 and GABA transporter subtype 3 modulate glutamatergic transmission via activation of presynaptic GABA(B) receptors in the rat globus pallidus.  


The intra-pallidal application of ?-aminobutyric acid (GABA) transporter subtype 1 (GAT-1) or GABA transporter subtype 3 (GAT-3) transporter blockers [1-(4,4-diphenyl-3-butenyl)-3-piperidinecarboxylic acid hydrochloride (SKF 89976A) or 1-[2-[tris(4-methoxyphenyl)methoxy]ethyl]-(S)-3-piperidinecarboxylic acid (SNAP 5114)] reduces the activity of pallidal neurons in monkey. This effect could be mediated through the activation of presynaptic GABA(B) heteroreceptors in glutamatergic terminals by GABA spillover following GABA transporter (GAT) blockade. To test this hypothesis, we applied the whole-cell recording technique to study the effects of SKF 89976A and SNAP 5114 on evoked excitatory postsynaptic currents (eEPSCs) in the presence of gabazine, a GABA(A) receptor antagonist, in rat globus pallidus slice preparations. Under the condition of postsynaptic GABA(B) receptor blockade by the intra-cellular application of N-(2,6-dimethylphenylcarbamoylmethyl)-triethylammonium bromide (OX314), bath application of SKF 89976A (10 ?M) or SNAP 5114 (10 ?M) decreased the amplitude of eEPSCs, without a significant effect on its holding current and whole cell input resistance. The inhibitory effect of GAT blockade on eEPSCs was blocked by (2S)-3-[[(1S)-1-(3,4-dichlorophenyl)ethyl]amino-2-hydroxypropyl](phenylmethyl)phosphinic acid, a GABA(B) receptor antagonist. The paired-pulse ratio of eEPSCs was increased, whereas the frequency, but not the amplitude, of miniature excitatory postsynaptic currents was reduced in the presence of either GAT blocker, demonstrating a presynaptic effect. These results suggest that synaptically released GABA can inhibit glutamatergic transmission through the activation of presynaptic GABA(B) heteroreceptors following GAT-1 or GAT-3 blockade. In conclusion, our findings demonstrate that presynaptic GABA(B) heteroreceptors in putative glutamatergic subthalamic afferents to the globus pallidus are sensitive to increases in extracellular GABA induced by GAT inactivation, thereby suggesting that GAT blockade represents a potential mechanism by which overactive subthalamopallidal activity may be reduced in parkinsonism. PMID:22616751

Jin, Xiao-Tao; Paré, Jean-Francois; Smith, Yoland



A mitochondrial GABA permease connects the GABA shunt and the TCA cycle, and is essential for normal carbon metabolism.  


In plants, ?-aminobutyric acid (GABA) accumulates in the cytosol in response to a variety of stresses. GABA is transported into mitochondria, where it is catabolized into TCA cycle or other intermediates. Although there is circumstantial evidence for mitochondrial GABA transporters in eukaryotes, none have yet been identified. Described here is an Arabidopsis protein similar in sequence and topology to unicellular GABA transporters. The expression of this protein complements a GABA-transport-deficient yeast mutant. Thus the protein was termed AtGABP to indicate GABA-permease activity. In vivo localization of GABP fused to GFP and immunobloting of subcellular fractions demonstrate its mitochondrial localization. Direct [(3) H]GABA uptake measurements into isolated mitochondria revealed impaired uptake into mitochondria of a gabp mutant compared with wild-type (WT) mitochondria, implicating AtGABP as a major mitochondrial GABA carrier. Measurements of CO(2) release, derived from radiolabeled substrates in whole seedlings and in isolated mitochondria, demonstrate impaired GABA-derived input into the TCA cycle, and a compensatory increase in TCA cycle activity in gabp mutants. Finally, growth abnormalities of gabp mutants under limited carbon availability on artificial media, and in soil under low light intensity, combined with their metabolite profiles, suggest an important role for AtGABP in primary carbon metabolism and plant growth. Thus, AtGABP-mediated transport of GABA from the cytosol into mitochondria is important to ensure proper GABA-mediated respiration and carbon metabolism. This function is particularly essential for plant growth under conditions of limited carbon. PMID:21501262

Michaeli, Simon; Fait, Aaron; Lagor, Kelly; Nunes-Nesi, Adriano; Grillich, Nicole; Yellin, Ayelet; Bar, Dana; Khan, Munziba; Fernie, Alisdair R; Turano, Frank J; Fromm, Hillel



Glutamate Uptake Triggers Transporter-Mediated GABA Release from Astrocytes  

PubMed Central

Background Glutamate (Glu) and ?-aminobutyric acid (GABA) transporters play important roles in regulating neuronal activity. Glu is removed from the extracellular space dominantly by glial transporters. In contrast, GABA is mainly taken up by neurons. However, the glial GABA transporter subtypes share their localization with the Glu transporters and their expression is confined to the same subpopulation of astrocytes, raising the possibility of cooperation between Glu and GABA transport processes. Methodology/Principal Findings Here we used diverse biological models both in vitro and in vivo to explore the interplay between these processes. We found that removal of Glu by astrocytic transporters triggers an elevation in the extracellular level of GABA. This coupling between excitatory and inhibitory signaling was found to be independent of Glu receptor-mediated depolarization, external presence of Ca2+ and glutamate decarboxylase activity. It was abolished in the presence of non-transportable blockers of glial Glu or GABA transporters, suggesting that the concerted action of these transporters underlies the process. Conclusions/Significance Our results suggest that activation of Glu transporters results in GABA release through reversal of glial GABA transporters. This transporter-mediated interplay represents a direct link between inhibitory and excitatory neurotransmission and may function as a negative feedback combating intense excitation in pathological conditions such as epilepsy or ischemia.

Heja, Laszlo; Barabas, Peter; Nyitrai, Gabriella; Kekesi, Katalin A.; Lasztoczi, Balint; Toke, Orsolya; Tarkanyi, Gabor; Madsen, Karsten; Schousboe, Arne; Dobolyi, Arpad; Palkovits, Miklos; Kardos, Julianna



Therapeutic potential of GABA(B) receptor ligands in drug addiction, anxiety, depression and other CNS disorders.  


Glutamate and ?-aminobutyric acid (GABA) are the major excitatory and inhibitory neurotransmitter systems, respectively in the central nervous system (CNS). Dysregulation, in any of these or both, has been implicated in various CNS disorders. GABA acts via ionotropic (GABA(A) and GABA(C) receptor) and metabotropic (GABA(B)) receptor. Dysregulation of GABAergic signaling and alteration in GABA(B) receptor expression has been implicated in various CNS disorders. Clinically, baclofen-a GABA(B) receptor agonist is available for the treatment of spasticity, dystonia etc., associated with various neurological disorders. Moreover, GABAB receptor ligands has also been suggested to be beneficial in various neuropsychiatric and neurodegenerative disorders. The present review is aimed to discuss the role of GABA(B) receptors and the possible outcomes of GABA(B) receptor modulation in CNS disorders. PMID:23872369

Kumar, Kushal; Sharma, Sorabh; Kumar, Puneet; Deshmukh, Rahul



Free and conjugated GABA in human cerebrospinal fluid: effect of degenerative neurologic diseases and isoniazid.  


gamma-Aminobutyric acid (GABA) was measured in CSF as such and following acid hydrolysis by the ion-exchange/fluorometric method. The conjugated GABA level was obtained by subtracting the free GABA level from the total GABA level. Results showed that at room temperature, while the free GABA level increased, the level of conjugated GABA decreased in a linear fashion during the first 24 h (r = -0.974; P less than 0.001). Aging and CSF conjugated GABA levels were inversely correlated (r = -0.613; P less than 0.05). Unlike free GABA levels, the levels of conjugated GABA were not altered in Huntington's disease, Parkinson's disease, cerebellar ataxias, dementias, epilepsy and multiple sclerosis compared to controls. In patients with Huntington's disease, on administration of isoniazid at 900 mg/day, along with pyridoxine at 100 mg/day, a 4-fold increase of both free (P less than 0.005) and conjugated GABA (P less than 0.0025) was seen. The results indicate that while total GABAergic peptides are not altered in several of the neurologic diseases studied, drugs such as isoniazid and/or pyridoxine can significantly elevate both free and conjugated GABA levels in human CSF. PMID:6235893

Manyam, B V; Tremblay, R D



Long-term reproducibility of GABA magnetic resonance spectroscopy.  


Recent findings suggest that cortical gamma aminobutyric acid (GABA) levels may provide a surrogate marker for a number of psychiatric and neurological conditions, as well as behavioural traits. However, the natural variability of GABA levels in the human brain over long periods of time (>8days) has not yet been studied. The purpose of this work was to investigate the long-term variability of GABA concentrations in the human occipital cortex. Nineteen healthy male participants were recruited and underwent two sessions of magnetic resonance spectroscopy (MRS) to determine occipital GABA levels with an average between-session interval of 7months. We assessed between-session variability, as well as the correlation between session 1 and session 2 GABA measurements. The mean coefficient of variation between sessions was 4.3% (bootstrap 95% confidence interval: 2.5, 6.4), which is comparable to reported GABA variability measurements over much shorter time intervals (<8days). A significant positive correlation was observed between session 1 and session 2 GABA measurements (r=0.53, p=0.014), and the intra-class correlation coefficient was calculated to be 0.52 which was also statistically significant (p=0.012). These findings establish experimentally that GABA concentrations in the occipital cortex, as measured by MRS, are relatively stable over periods as long as 7months. The findings have significant implications for the internal validity of longitudinal studies of GABA levels in the human brain, and they lend foundational support to studies relating GABA levels to behavioural traits in healthy individuals. PMID:24875142

Near, Jamie; Ho, Yi-Ching Lynn; Sandberg, Kristian; Kumaragamage, Chathura; Blicher, Jakob Udby



Regulation of /sup 3/H-dopamine release by presynaptic GABA and glutamate heteroreceptors in rat brain nucleus accumbens synaptosomes  

SciTech Connect

The aim of this investigation was a neurochemical study of the effect of agonists of different types of GABA receptors - muscimol (type A receptor), baclofen (type B receptor), delta-aminolevulinic acid (DALA; GABA autoreceptor), and also of GABA itself - on tritium-labelled dopamine release, stimulated by potassium cations, from synaptosomes of the nuclei accumbenes of the rat brain.

Kovalev, G.I.; Hetey, L.



3H-GABA uptake selectively labels identifiable neurons in the leech central nervous system  

SciTech Connect

Segmental ganglia of the leech ventral nerve cord synthesize the neurotransmitter gamma-aminobutyric acid (GABA) when incubated in the presence of the precursor glutamate, suggesting that there may be GABA-ergic neurons in the leech nerve cord. GABA-accumulating neurons of the two taxonomically distant leech species, Haementeria ghilianii and Hirudo medicinalis, have been labeled by taking advantage of their high-affinity uptake system for the neurotransmitter. Autoradiography of sectioned segmental ganglia previously exposed to 3H-GABA reveals a reproducible pattern of about thirty 3H-GABA-labeled neuronal cell bodies per ganglion. The majority of 3H-GABA-labeled neuronal cell bodies are bilaterally paired, although some apparently unpaired cell bodies also accumulate label. Neuronal processes were reproducibly labeled by GABA uptake and could be traced in the neuropil through commissures and fiber tracts into the segmental nerve roots and interganglionic connectives, respectively.

Cline, H.T.



Simultaneous determination of monoamine and amino acid neurotransmitters in rat endbrain tissues by pre-column derivatization with high-performance liquid chromatographic fluorescence detection and mass spectrometric identification.  


A sensitive and efficient method for simultaneous determination of glutamic acid (Glu), gamma-amino-butyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in rat endbrains was developed by high-performance liquid chromatography (HPLC) with fluorescence detection and on-line mass spectrometric identification following derivatization with 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC). Different parameters which influenced derivatization and separation were optimized. The complete separation of five neurotransmitter (NT) derivatives was performed on a reversed-phase Hypersil BDS-C(18) column with a gradient elution. The rapid structure identification of five neurotransmitter derivatives was carried out by on-line mass spectrometry with electrospray ionization (ESI) source in positive ion mode, and the BCEOC-labeled derivatives were characterized by easy-to-interpret mass spectra. Stability of derivatives, repeatability, precision and accuracy were evaluated and the results were excellent for efficient HPLC analysis. The quantitative linear range of five neurotransmitters were 2.441-2x10(4) nM, and limits of detection were in the range of 0.398-1.258 nM (S/N=3:1). The changes of their concentrations in endbrains of three rat groups were also studied using this HPLC fluorescence detection method. The results indicated that exhausting exercise could obviously influence the concentrations of neurotransmitters in rat endbrains. The established method exhibited excellent validity, high sensitivity and convenience, and provided a new technique for simultaneous analysis of monoamine and amino acid neurotransmitters in rat brain. PMID:18585341

Zhao, Xian-En; Suo, You-Rui



A Gut Feeling about GABA: Focus on GABAB Receptors  

PubMed Central

?-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the body and hence GABA-mediated neurotransmission regulates many physiological functions, including those in the gastrointestinal (GI) tract. GABA is located throughout the GI tract and is found in enteric nerves as well as in endocrine-like cells, implicating GABA as both a neurotransmitter and an endocrine mediator influencing GI function. GABA mediates its effects via GABA receptors which are either ionotropic GABAA or metabotropic GABAB. The latter which respond to the agonist baclofen have been least characterized, however accumulating data suggest that they play a key role in GI function in health and disease. Like GABA, GABAB receptors have been detected throughout the gut of several species in the enteric nervous system, muscle, epithelial layers as well as on endocrine-like cells. Such widespread distribution of this metabotropic GABA receptor is consistent with its significant modulatory role over intestinal motility, gastric emptying, gastric acid secretion, transient lower esophageal sphincter relaxation and visceral sensation of painful colonic stimuli. More intriguing findings, the mechanisms underlying which have yet to be determined, suggest GABAB receptors inhibit GI carcinogenesis and tumor growth. Therefore, the diversity of GI functions regulated by GABAB receptors makes it a potentially useful target in the treatment of several GI disorders. In light of the development of novel compounds such as peripherally acting GABAB receptor agonists, positive allosteric modulators of the GABAB receptor and GABA producing enteric bacteria, we review and summarize current knowledge on the function of GABAB receptors within the GI tract.

Hyland, Niall P.; Cryan, John F.



GABA A autoreceptors enhance GABA release from human neocortex: towards a mechanism for high-frequency stimulation (HFS) in brain?  

Microsoft Academic Search

High-frequency stimulation (HFS) in human neocortical slices induces ?-aminobutyric acid (GABA) release via GABAA receptor (GABAAR) activation. The mechanism of this effect and the localization of these GABAARs were now studied. Fresh human neocortical slices were subjected to HFS (130 Hz) in the presence of veratridine (3 µM).\\u000a As measured by high-performance liquid chromatography, only GABA but not glutamate outflow was affected

Michela Mantovani; Andreas Moser; Carola A. Haas; Josef Zentner; Thomas J. Feuerstein



Identification and functional characterization of a dual GABA/taurine transporter in the bullfrog retinal pigment epithelium  

PubMed Central

Intracellular microelectrodes, fluorescence imaging, and radiotracer flux techniques were used to investigate the physiological response of the retinal pigment epithelium (RPE) to the major retinal inhibitory neurotransmitter, gamma-aminobutyric acid (GABA). GABA is released tonically in the dark by amphibian horizontal cells, but is not taken up by the nearby Muller cells. Addition of GABA to the apical bath produced voltage responses in the bullfrog RPE that were not blocked nor mimicked by any of the major GABA-receptor antagonists or agonists. Nipecotic acid, a substrate for GABA transport, inhibited the voltage effects of GABA. GABA and nipecotic acid also inhibited the voltage effects of taurine, suggesting that the previously characterized beta- alanine sensitive taurine carrier also takes up GABA. The voltage responses of GABA, taurine, nipecotic acid, and beta-alanine all showed first-order saturable kinetics with the following Km's: GABA (Km = 160 microM), beta-alanine (Km = 250 microM), nipecotic acid (Km = 420 microM), and taurine (Km = 850 microM). This low affinity GABA transporter is dependent on external Na, partially dependent on external Cl, and is stimulated in low [K]o, which approximates subretinal space [K]o during light onset. Apical GABA also produced a significant conductance increase at the basolateral membrane. These GABA-induced conductance changes were blocked by basal Ba2+, suggesting that GABA decreased basolateral membrane K conductance. In addition, the apical membrane Na/K ATPase was stimulated in the presence of GABA. A model for the interaction between the GABA transporter, the Na/K ATPase, and the basolateral membrane K conductance accounts for the electrical effects of GABA. Net apical-to-basal flux of [3H]-GABA was also observed in radioactive flux experiments. The present study shows that a high capacity GABA uptake mechanism with unique pharmacological properties is located at the RPE apical membrane and could play an important role in the removal of GABA from the subretinal space (SRS). This transporter could also coordinate the activities of GABA and taurine in the SRS after transitions between light and dark.



Sex, GABA, and Nicotine: The Impact of Smoking on Cortical GABA Levels Across the Menstrual Cycle as Measured with Proton Magnetic Resonance Spectroscopy  

PubMed Central

Background Given that nicotine modulates amino acid neurotransmission, we sought to examine the impact of nicotine on cortical ?-aminobutyric acid (GABA) levels in male and female smokers. Methods Healthy nicotine-dependent men (n = 10) and women (n = 6) underwent proton magnetic resonance spectroscopy (1H-MRS) to measure occipital cortex GABA concentrations. A subset of the smoking men (n = 5) underwent 1H-MRS scans before and after 48 hours of smoking abstinence, whereas each of the women were scheduled to undergo pre- and postabstinence scans during the follicular and luteal phases of one menstrual cycle. Healthy nonsmoking men (n = 7) and women (n = 13) underwent 1H-MRS for comparison. Results Short-term abstinence had no significant effect on cortical GABA concentrations in either men or women. There was, however, a significant effect of sex, diagnosis (smoker/nonsmoker), and menstrual cycle phase on cortical GABA levels, such that female smokers experienced a significant reduction in cortical GABA levels during the follicular phase and no cyclicity in GABA levels across the menstrual cycle, whereas cortical GABA levels were similar in smoking and nonsmoking men. Conclusions Taken together with previous 1H-MRS data showing abnormalities in occipital cortex GABA concentrations in several affective disorders, our preliminary finding that nicotine modulation of GABA levels varies by sex provides a further rationale for investigating the impact of nicotine on central GABAergic function as a potential risk factor for women to experience depressive symptoms during smoking cessation.

Epperson, C. Neill; O'Malley, Stephanie; Czarkowski, Kathryn A.; Gueorguieva, Ralitza; Jatlow, Peter; Sanacora, Gerard; Rothman, Douglas L.; Krystal, John H.; Mason, Graeme F.



Effect of chronic administration of methamphetamine on the responsiveness of substantia nigra zona reticulata neurons to GABA or a GABA agonist in rats  

Microsoft Academic Search

The effects of chronic administration of methamphetamine on the responsiveness of neurons of the substantia nigra zona reticulata (SNR) to gammaaminobutyric acid (GABA) or to a GABA receptor agonist were examined. Neuronal activity was recorded from the SNR of rats that had been pretreated twice daily, for 6 consecutive days, with saline or with 5 mg\\/kg methamphetamine. Intravenous administration of

Katsuo Kamata; Tsutomu Kameyama



Expression and Functional Characterization of GABA Transporters in Crayfish Neurosecretory Cells  

Microsoft Academic Search

The effect of GABA on membrane potential and ionic cur- rents of X-organ neurons isolated from the crayfish eyestalk was investigated. Under voltage-clamp conditions, GABA elicited an inward Na current followed by a sustained out- ward chloride current. Sodium current was partially blocked in a dose-dependent manner by antagonists of GABA plasma membrane transporters such as -alanine, nipecotic acid, 1-(2(((diphenylmethylene)imino)oxy)ethyl)-1,2,5,6-tetrahydro-3-

Julieta Garduno; Sergio Elenes; Jorge Cebada; Elizabeth Becerra; Ubaldo Garcia



An Ionotropic GABA Receptor with Novel Pharmacology at Bullfrog Cone Photoreceptor Terminals  

Microsoft Academic Search

Characteristics of ionotropic ?-aminobutyric acid (GABA) receptors at bullfrog cone terminals were studied by patch clamp techniques in isolated cell and retinal slice preparations. GABA-induced inward currents from isolated cones reversed in polarity at a potential, very close to the chloride equilibrium potential, and they were completely suppressed by picrotoxin. Unexpectedly, the GABA current was dose-dependently potentiated by the well-known

Jian Liu; Geng-Lin Li; Xiong-Li Yang



High Concentration of GABA and High Glutamate Decarboxylase Activity in Rat Pancreatic Islets and Human Insulinoma  

Microsoft Academic Search

The concentration of gamma -aminobutyric acid (GABA) and the activity of glutamate decarboxylase (GAD) in rat and human pancreas were measured by sensitive assay methods. The GABA concentration in rat pancreas was 2.51 millimoles per kilogram (dry weight) and GAD activity was 2.58 mmoles per kilogram per hour. The GABA concentration and GAD activity in rat Langerhans' islets were 18.9

Yasuhiro Okada; Hiroshi Taniguchi; Chicaco Shimada



Alterations of Cortical GABA Neurons and Network Oscillations in Schizophrenia  

PubMed Central

The hypothesis that alterations of cortical inhibitory ?-aminobutyric acid (GABA) neurons are a central element in the pathology of schizophrenia has emerged from a series of postmortem studies. How such abnormalities may contribute to the clinical features of schizophrenia has been substantially informed by a convergence with basic neuroscience studies revealing complex details of GABA neuron function in the healthy brain. Importantly, activity of the parvalbumin-containing class of GABA neurons has been linked to the production of cortical network oscillations. Furthermore, growing knowledge supports the concept that ? band oscillations (30–80 Hz) are an essential mechanism for cortical information transmission and processing. Herein we review recent studies further indicating that inhibition from parvalbumin-positive GABA neurons is necessary to produce ? oscillations in cortical circuits; provide an update on postmortem studies documenting that deficits in the expression of glutamic acid decarboxylase67, which accounts for most GABA synthesis in the cortex, are widely observed in schizophrenia; and describe studies using novel, noninvasive approaches directly assessing potential relations between alterations in GABA, oscillations, and cognitive function in schizophrenia.

Gonzalez-Burgos, Guillermo; Hashimoto, Takanori; Lewis, David A.



Relation of the [ 3H]?-hydroxybutyric acid (ghb) binding site to the ?-aminobutyric acid b (gaba b) receptor in rat brain  

Microsoft Academic Search

Hydroxybutyric acid (GHB) is a naturally occurring compound that has the ability to induce generalized absence seizures when given to animals. GHB has been hypothesized to induce this effect via the postsynaptic ?-aminobutyric acidB (GABAB) receptor. We sought to test this hypothesis by examining the affinity of GABAB agonists and antagonists for the [3H]GHB binding site, the affinity of GHB

O. Carter Snead



GABA and glycine as neurotransmitters: a brief history  

PubMed Central

?-Aminobutyric acid (GABA) emerged as a potentially important brain chemical just over 50 years ago, but its significance as a neurotransmitter was not fully realized until over 16 years later. We now know that at least 40% of inhibitory synaptic processing in the mammalian brain uses GABA. Establishing its role as a transmitter was a lengthy process and it seems hard to believe with our current knowledge that there was ever any dispute about its role in the mammalian brain. The detailed information that we now have about the receptors for GABA together with the wealth of agents which facilitate or reduce GABA receptor mechanisms make the prospects for further research very exciting. The emergence of glycine as a transmitter seems relatively painless by comparison to GABA. Perhaps this is appropriate for the simplest of transmitter structures! Its discovery within the spinal cord and brainstem approximately 40 years ago was followed only 2 years later by the proposal that it be conferred with ‘neurotransmitter' status. It was another 16 years before the receptor was biochemically isolated. Now it is readily accepted as a vital spinal and supraspinal inhibitory transmitter and we know many details regarding its molecular structure and trafficking around neurones. The pharmacology of these receptors has lagged behind that of GABA. There is not the rich variety of allosteric modulators that we have come to readily associate with GABA receptors and which has provided us with a virtual treasure trove of important drugs used in anxiety, insomnia, epilepsy, anaesthesia, and spasticity, all stemming from the actions of the simple neutral amino acid GABA. Nevertheless, the realization that glycine receptors are involved in motor reflexes and nociceptive pathways together with the more recent advent of drugs that exhibit some subtype selectivity make the goal of designing selective therapeutic ligands for the glycine receptor that much closer.

Bowery, N G; Smart, T G



ZAPA, a substrate for the neuronal high affinity GABA uptake system in rat brain slices.  


The GABA analogue ZAPA, a potent GABA(A) receptor agonist, is a substrate for the GABA high affinity neuronal uptake system. ZAPA was labelled with (14)C at a specific activity of 53 mCi/mmol by synthesis from [(14)C]thiourea. [(14)C]ZAPA was taken up into rat cortical slices having an affinity for the carrier about one third that of GABA (ZAPA K(m) 89 ?M; GABA K(m) 26 ?M). ZAPA uptake could be inhibited by the relatively selective GABA neuronal uptake inhibitor, nipecotic acid, but not by the relatively selective glial uptake inhibitor, ?-alanine. Specific binding of [(14)C]ZAPA (0.3 ?M) to GABA receptor sites was observed only under GABA(A) conditions with 23% of the total binding being displaced by 1 mM GABA. ZAPA would need to be labelled to higher specific activity to enable a more extensive study of its binding interactions with GABA(A) receptors. PMID:20504677

Allan, R D; Dickenson, H W; Duke, R K; Johnston, G A



Synchronization by Food Access Modifies the Daily Variations in Expression and Activity of Liver GABA Transaminase  

PubMed Central

Daytime restricted feeding (DRF) is an experimental protocol that influences the circadian timing system and underlies the expression of a biological clock known as the food entrained oscillator (FEO). Liver is the organ that reacts most rapidly to food restriction by adjusting the functional relationship between the molecular circadian clock and the metabolic networks. ?-Aminobutyric acid (GABA) is a signaling molecule in the liver, and able to modulate the cell cycle and apoptosis. This study was aimed at characterizing the expression and activity of the mostly mitochondrial enzyme GABA transaminase (GABA-T) during DRF/FEO expression. We found that DRF promotes a sustained increase of GABA-T in the liver homogenate and mitochondrial fraction throughout the entire day-night cycle. The higher amount of GABA-T promoted by DRF was not associated to changes in GABA-T mRNA or GABA-T activity. The GABA-T activity in the mitochondrial fraction even tended to decrease during the light period. We concluded that DRF influences the daily variations of GABA-T mRNA levels, stability, and catalytic activity of GABA-T. These data suggest that the liver GABAergic system responds to a metabolic challenge such as DRF and the concomitant appearance of the FEO.

De Ita-Perez, Dalia; Vazquez-Martinez, Olivia; Villalobos-Leal, Monica



Immunocytochemical mapping of an RDL-like GABA receptor subunit and of GABA in brain structures related to learning and memory in the cricket Acheta domesticus.  


The distribution of putative RDL-like GABA receptors and of gamma-aminobutyric acid (GABA) in the brain of the adult house cricket Acheta domesticus was studied using specific antisera. Special attention was given to brain structures known to be related to learning and memory. The main immunostaining for the RDL-like GABA receptor was observed in mushroom bodies, in particular the upper part of mushroom body peduncle and the two arms of the posterior calyx. Weaker immunostaining was detected in the distal part of the peduncle and in the alpha and beta lobes. The dorso- and ventrolateral protocerebrum neuropils appeared rich in RDL-like GABA receptors. Staining was also detected in the glomeruli of the antennal lobe, as well as in the ellipsoid body of the central complex. Many neurons clustered in groups exhibit GABA-like immunoreactivity. Tracts that were strongly immunostained innervated both the calyces and the lobes of mushroom bodies. The glomeruli of the antennal lobe, the ellipsoid body, as well as neuropils of the dorso- and ventrolateral protocerebrum were also rich in GABA-like immunoreactivity. The data demonstrated a good correlation between the distribution of the GABA-like and of the RDL-like GABA receptor immunoreactivity. The prominent distribution of RDL-like GABA receptor subunits, in particular areas of mushroom bodies and antennal lobes, underlines the importance of inhibitory signals in information processing in these major integrative centers of the insect brain. PMID:10454373

Strambi, C; Cayre, M; Sattelle, D B; Augier, R; Charpin, P; Strambi, A



Effects of some anticonvulsant drugs on brain GABA level and GAD and GABA-T activities  

Microsoft Academic Search

The effect of anticonvulsant drugs was examined on brain GABA levels and GAD and GABA-T activities. The level of GABA was increased by the treatment with diphenylhydantoin. The drug had no effect on GABA-T activity, whereas GAD activity was inhibited. Carbamazepine increased the GABA level but did not effect GAD and GABA-T activities. Diazepam had no effect on GABA level

Leontino Battistin; Mary Varotto; Giorgio Berlese; Giovanni Roman



Native GABA(B) receptors are heteromultimers with a family of auxiliary subunits.  


GABA(B) receptors are the G-protein-coupled receptors for gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the brain. They are expressed in almost all neurons of the brain, where they regulate synaptic transmission and signal propagation by controlling the activity of voltage-gated calcium (Ca(v)) and inward-rectifier potassium (K(ir)) channels. Molecular cloning revealed that functional GABA(B) receptors are formed by the heteromeric assembly of GABA(B1) with GABA(B2) subunits. However, cloned GABA(B(1,2)) receptors failed to reproduce the functional diversity observed with native GABA(B) receptors. Here we show by functional proteomics that GABA(B) receptors in the brain are high-molecular-mass complexes of GABA(B1), GABA(B2) and members of a subfamily of the KCTD (potassium channel tetramerization domain-containing) proteins. KCTD proteins 8, 12, 12b and 16 show distinct expression profiles in the brain and associate tightly with the carboxy terminus of GABA(B2) as tetramers. This co-assembly changes the properties of the GABA(B(1,2)) core receptor: the KCTD proteins increase agonist potency and markedly alter the G-protein signalling of the receptors by accelerating onset and promoting desensitization in a KCTD-subtype-specific manner. Taken together, our results establish the KCTD proteins as auxiliary subunits of GABA(B) receptors that determine the pharmacology and kinetics of the receptor response. PMID:20400944

Schwenk, Jochen; Metz, Michaela; Zolles, Gerd; Turecek, Rostislav; Fritzius, Thorsten; Bildl, Wolfgang; Tarusawa, Etsuko; Kulik, Akos; Unger, Andreas; Ivankova, Klara; Seddik, Riad; Tiao, Jim Y; Rajalu, Mathieu; Trojanova, Johana; Rohde, Volker; Gassmann, Martin; Schulte, Uwe; Fakler, Bernd; Bettler, Bernhard



Ionic Mechanisms of Neuronal Excitation by Inhibitory GABA_A Receptors  

NASA Astrophysics Data System (ADS)

Gamma-aminobutyric acid A (GABA_A) receptors are the principal mediators of synaptic inhibition, and yet when intensely activated, dendritic GABA_A receptors excite rather than inhibit neurons. The membrane depolarization mediated by GABA_A receptors is a result of the differential, activity-dependent collapse of the opposing concentration gradients of chloride and bicarbonate, the anions that permeate the GABA_A ionophore. Because this depolarization diminishes the voltage-dependent block of the N-methyl-D-aspartate (NMDA) receptor by magnesium, the activity-dependent depolarization mediated by GABA is sufficient to account for frequency modulation of synaptic NMDA receptor activation. Anionic gradient shifts may represent a mechanism whereby the rate and coherence of synaptic activity determine whether dendritic GABA_A receptor activation is excitatory or inhibitory.

Staley, Kevin J.; Soldo, Brandi L.; Proctor, William R.



In vivo measurements of glutamate, GABA, and NAAG in schizophrenia.  


The major excitatory and inhibitory neurotransmitters, glutamate (Glu) and gamma-aminobutyric acid (GABA), respectively, are implicated in the pathophysiology of schizophrenia. N-acetyl-aspartyl-glutamate (NAAG), a neuropeptide that modulates the Glu system, may also be altered in schizophrenia. This study investigated GABA, Glu + glutamine (Glx), and NAAG levels in younger and older subjects with schizophrenia. Forty-one subjects, 21 with chronic schizophrenia and 20 healthy controls, participated in this study. Proton magnetic resonance spectroscopy ((1)H-MRS) was used to measure GABA, Glx, and NAAG levels in the anterior cingulate (AC) and centrum semiovale (CSO) regions. NAAG in the CSO was higher in younger schizophrenia subjects compared with younger control subjects. The opposite pattern was observed in the older groups. Glx was reduced in the schizophrenia group irrespective of age group and brain region. There was a trend for reduced AC GABA in older schizophrenia subjects compared with older control subjects. Poor attention performance was correlated to lower AC GABA levels in both groups. Higher levels of CSO NAAG were associated with greater negative symptom severity in schizophrenia. These results provide support for altered glutamatergic and GABAergic function associated with illness course and cognitive and negative symptoms in schizophrenia. The study also highlights the importance of studies that combine MRS measurements of NAAG, GABA, and Glu for a more comprehensive neurochemical characterization of schizophrenia. PMID:23081992

Rowland, Laura M; Kontson, Kimberly; West, Jeffrey; Edden, Richard A; Zhu, He; Wijtenburg, S Andrea; Holcomb, Henry H; Barker, Peter B



A Role for GAT-1 in Presynaptic GABA Homeostasis?  

PubMed Central

In monoamine-releasing terminals, neurotransmitter transporters – in addition to terminating synaptic transmission by clearing released transmitters from the extracellular space – are the primary mechanism for replenishing transmitter stores and thus regulate presynaptic homeostasis. Here, we analyze whether GAT-1, the main plasma membrane GABA transporter, plays a similar role in GABAergic terminals. Re-examination of existing literature and recent data gathered in our laboratory show that GABA homeostasis in GABAergic terminals is dominated by the activity of the GABA synthesizing enzyme and that GAT-1-mediated GABA transport contributes to cytosolic GABA levels. However, analysis of GAT-1 KO, besides demonstrating the effects of reduced clearance, reveals the existence of changes compatible with an impaired presynaptic function, as miniature IPSCs frequency is reduced by one-third and glutamic acid decarboxylases and phosphate-activated glutaminase levels are significantly up-regulated. Although the changes observed are less robust than those reported in mice with impaired dopamine, noradrenaline, and serotonin plasma membrane transporters, they suggest that in GABAergic terminals GAT-1 impacts on presynaptic GABA homeostasis, and may contribute to the activity-dependent regulation of inhibitory efficacy.

Conti, Fiorenzo; Melone, Marcello; Fattorini, Giorgia; Bragina, Luca; Ciappelloni, Silvia



Development of GABA and glutamate signaling at the GnRH neuron in relation to puberty  

Microsoft Academic Search

The gonadotropin-releasing hormone (GnRH) neurons represent the critical cell type activated to induce puberty in mammals. However, the mechanisms underlying their activation remain unclear. As the principal amino acid neurotransmitters in the brain, GABA and glutamate are known to have critical roles in the development of neuronal networks. This review provides an update on what is known about GABA and

Jenny Clarkson; Allan E. Herbison



Analysis of GABA(A)- and GABA(B)-receptor mediated effects on intracellular Ca(2+) in DRG hybrid neurones.  


1. Using pharmacological analysis and fura-2 spectrofluorimetry, we examined the effects of gamma-aminobutyric acid (GABA) and related substances on intracellular Ca(2+) concentration ([Ca(2+)]i) of hybrid neurones, called MD3 cells. The cell line was produced by fusion between a mouse neuroblastoma cell and a mouse dorsal root ganglion (DRG) neurone. 2. MD3 cells exhibited DRG neurone-like properties, such as immunoreactivity to microtubule-associated protein-2 and neurofilament proteins. Bath applications of capsaicin and alpha, beta-methylene adenosine triphosphate reversibly increased [Ca(2+)]i. However, repeated applications of capsaicin were much less effective. 3. Pressure applications of GABA (100 microM), (Z)-3-[(aminoiminomethyl) thio] prop-2-enoic acid sulphate (ZAPA; 100 microM), an agonist at low affinity GABA(A)-receptors, or KCl (25 mM), transiently increased [Ca(2+)]i. 4. Bath application of bicuculline (100 nM - 100 microM), but not picrotoxinin (10 - 25 microM), antagonized GABA-induced increases in [Ca(2+)]i in a concentration-dependent manner (IC(50)=9.3 microM). 5. Ca(2+)-free perfusion reversibly abolished GABA-evoked increases in [Ca(2+)]i. Nifedipine and nimodipine eliminated GABA-evoked increases in [Ca(2+)]i. These results imply GABA response dependence on extracellular Ca(2+). 6. Baclofen (500 nM - 100 microM) activation of GABA(B)-receptors reversibly attenuated KCl-induced increases in [Ca(2+)]i in a concentration-dependent manner (EC(50)=1.8 microM). 2-hydroxy-saclofen (1 - 20 microM) antagonized the baclofen-depression of the KCl-induced increase in [Ca(2+)]i. 7. In conclusion, GABA(A)-receptor activation had effects similar to depolarization by high external K(+), initiating Ca(2+) influx through high voltage-activated channels, thereby transiently elevating [Ca(2+)]i. GABA(B)-receptor activation reduced Ca(2+) influx evoked by depolarization, possibly at Ca(2+)-channel sites in MD3 cells. PMID:11522601

Yokogawa, T; Kim, S U; Krieger, C; Puil, E



Dopamine and serotonin modulate human GABA?1 receptors expressed in Xenopus laevis oocytes.  


GABA?1 receptors are highly expressed in bipolar neurons of the retina and to a lesser extent in several areas of the central nervous system (CNS), and dopamine and serotonin are also involved in the modulation of retinal neural transmission. Whether these biogenic amines have a direct effect on ionotropic GABA receptors was not known. Here, we report that GABA?1 receptors, expressed in X. laevis oocytes, were negatively modulated by dopamine and serotonin and less so by octopamine and tyramine. Interestingly, these molecules did not have effects on GABA(A) receptors. 5-Carboxamido-tryptamine and apomorphine did not exert evident effects on any of the receptors. Schild plot analyses of the inhibitory actions of dopamine and serotonin on currents elicited by GABA showed slopes of 2.7 ± 0.3 and 6.1 ± 1.8, respectively, indicating a noncompetitive mechanism of inhibition. The inhibition of GABA?1 currents was independent of the membrane potential and was insensitive to picrotoxin, a GABA receptor channel blocker and to the GABA?-specific antagonist (1,2,5,6-tetrahydropyridine-4-yl)methyl phosphinic acid (TPMPA). Dopamine and serotonin changed the sensitivity of GABA?1 receptors to the inhibitory actions of Zn(2+). In contrast, La(3+) potentiated the amplitude of the GABA currents generated during negative modulation by dopamine (EC(50) 146 ?M) and serotonin (EC(50) 196 ?M). The functional role of the direct modulation of GABA? receptors by dopamine and serotonin remains to be elucidated; however, it may represent an important modulatory pathway in the retina, where GABA? receptors are highly expressed and where these biogenic amines are abundant. PMID:22860179

Ochoa-de la Paz, Lenin D; Estrada-Mondragón, Argel; Limón, Agenor; Miledi, Ricardo; Martínez-Torres, Ataúlfo



Gephyrin-independent GABA(A)R mobility and clustering during plasticity.  


The activity-dependent modulation of GABA-A receptor (GABA(A)R) clustering at synapses controls inhibitory synaptic transmission. Several lines of evidence suggest that gephyrin, an inhibitory synaptic scaffold protein, is a critical factor in the regulation of GABA(A)R clustering during inhibitory synaptic plasticity induced by neuronal excitation. In this study, we tested this hypothesis by studying relative gephyrin dynamics and GABA(A)R declustering during excitatory activity. Surprisingly, we found that gephyrin dispersal is not essential for GABA(A)R declustering during excitatory activity. In cultured hippocampal neurons, quantitative immunocytochemistry showed that the dispersal of synaptic GABA(A)Rs accompanied with neuronal excitation evoked by 4-aminopyridine (4AP) or N-methyl-D-aspartic acid (NMDA) precedes that of gephyrin. Single-particle tracking of quantum dot labeled-GABA(A)Rs revealed that excitation-induced enhancement of GABA(A)R lateral mobility also occurred before the shrinkage of gephyrin clusters. Physical inhibition of GABA(A)R lateral diffusion on the cell surface and inhibition of a Ca(2+) dependent phosphatase, calcineurin, completely eliminated the 4AP-induced decrease in gephyrin cluster size, but not the NMDA-induced decrease in cluster size, suggesting the existence of two different mechanisms of gephyrin declustering during activity-dependent plasticity, a GABA(A)R-dependent regulatory mechanism and a GABA(A)R-independent one. Our results also indicate that GABA(A)R mobility and clustering after sustained excitatory activity is independent of gephyrin. PMID:22563445

Niwa, Fumihiro; Bannai, Hiroko; Arizono, Misa; Fukatsu, Kazumi; Triller, Antoine; Mikoshiba, Katsuhiko



Focal uncaging of GABA reveals a temporally defined role for GABAergic inhibition during appetitive associative olfactory conditioning in honeybees.  


Throughout the animal kingdom, the inhibitory neurotransmitter ?-aminobutyric acid (GABA) is a key modulator of physiological processes including learning. With respect to associative learning, the exact time in which GABA interferes with the molecular events of learning has not yet been clearly defined. To address this issue, we used two different approaches to activate GABA receptors during appetitive olfactory conditioning in the honeybee. Injection of GABA-A receptor agonist muscimol 20 min before but not 20 min after associative conditioning affects memory performance. These memory deficits were attenuated by additional training sessions. Muscimol has no effect on sensory perception, odor generalization, and nonassociative learning, indicating a specific role of GABA during associative conditioning. We used photolytic uncaging of GABA to identify the GABA-sensitive time window during the short pairing of the conditioned stimulus (CS) and the unconditioned stimulus (US) that lasts only seconds. Either uncaging of GABA in the antennal lobes or the mushroom bodies during the CS presentation of the CS-US pairing impairs memory formation, while uncaging GABA during the US phase has no effect on memory. Uncaging GABA during the CS presentation in memory retrieval also has no effect. Thus, in honeybee appetitive olfactory learning GABA specifically interferes with the integration of CS and US during associative conditioning and exerts a modulatory role in memory formation depending on the training strength. PMID:23860600

Raccuglia, Davide; Mueller, Uli



Lactate-induced release of GABA in the ventromedial hypothalamus contributes to counterregulatory failure in recurrent hypoglycemia and diabetes.  


Suppression of GABAergic neurotransmission in the ventromedial hypothalamus (VMH) is crucial for full activation of counterregulatory responses to hypoglycemia, and increased ?-aminobutyric acid (GABA) output contributes to counterregulatory failure in recurrently hypoglycemic (RH) and diabetic rats. The goal of this study was to establish whether lactate contributes to raising VMH GABA levels in these two conditions. We used microdialysis to deliver artificial extracellular fluid or L-lactate into the VMH and sample for GABA. We then microinjected a GABAA receptor antagonist, an inhibitor of lactate transport (4CIN), or an inhibitor of lactate dehydrogenase, oxamate (OX), into the VMH prior to inducing hypoglycemia. To assess whether lactate contributes to raising GABA in RH and diabetes, we injected 4CIN or OX into the VMH of RH and diabetic rats before inducing hypoglycemia. L-lactate raised VMH GABA levels and suppressed counterregulatory responses to hypoglycemia. While blocking GABAA receptors did not prevent the lactate-induced rise in GABA, inhibition of lactate transport or utilization did, despite the presence of lactate. All three treatments restored the counterregulatory responses, suggesting that lactate suppresses these responses by enhancing GABA release. Both RH and diabetic rats had higher baseline GABA levels and were unable to reduce GABA levels sufficiently to fully activate counterregulatory responses during hypoglycemia. 4CIN or OX lowered VMH GABA levels in both RH and diabetic rats and restored the counterregulatory responses. Lactate likely contributes to counterregulatory failure in RH and diabetes by increasing VMH GABA levels. PMID:23939392

Chan, Owen; Paranjape, Sachin A; Horblitt, Adam; Zhu, Wanling; Sherwin, Robert S



Uptake of a Metabolically Inert Amino Acid by Brain Tissue During High Pressure Oxygen Exposure.  

National Technical Information Service (NTIS)

Large intraperitoneal doses of gamma-aminobutyric acid (GABA) protect animals against high pressure oxygen (HPO)-induced convulsions, apparently by elevation of brain GABA levels. Although normally impermeable to GABA, the blood-brain barrier may be affec...

D. E. Holness M. W. Radomski



Ectopic action potential generation in cortical interneurons during synchronized GABA responses.  


In the presence of 4-aminopyridine and excitatory amino acid receptor antagonists, individual neurons in brain slice preparations exhibit large gamma aminobutyric acid (GABA)-mediated responses as a consequence of synchronous GABA release from a network of interneurons. These synchronized GABA responses are frequently associated with ectopic action potentials (EAPs), which are thought to be action potentials initiated in distal axon terminals which subsequently travel antidromically toward the soma. Ectopic action potentials feature prominently in some models of epilepsy. Neocortical synchronized GABA responses propagate across the cortex, predominantly in superficial layers. The role that EAPs may play in contributing to laminar differences in the synchronized GABA response has not been addressed. Here we examined the occurrence of EAPs during synchronized GABA responses in neurons within layers I and II/III. EAPs occurred in 78% of layer I interneurons and in 25% of layer II/III interneurons (including chandelier cells). EAPs were not observed in layer II/III pyramidal neurons. The prevalence of EAPs in layer I interneurons provides a mechanism by which layer I can support both the initiation and propagation of synchronized GABA responses. Thus, layer I interneurons are a critical component of a network capable of synchronizing a propagating wave of GABA release across the neocortex. PMID:15749338

Keros, S; Hablitz, J J



Mechanisms of GABA release from human astrocytes.  


We have previously demonstrated that human astrocytes are GABAergic cells. Throughout the adult human brain, they express the GABA synthesizing enzyme GAD 67, the GABA metabolizing enzyme GABA-T, and the GABA(A) and GABA(B) receptors. GABA modulates the actions of microglia, indicating an important role for astrocytes beyond that of influencing neurotransmitter function. Here we report on the mechanisms by which astrocytes release GABA. Astrocytes were found to express the mRNA and protein for multiple GABA transporters, and multiple receptors for glutamate, GABA, and glycine. In culture, untreated human astrocytes maintained an intracellular GABA level of 2.32 mM. They exported GABA into the culture medium so that an intracellular-extracellular gradient of 3.64 fold was reached. Inhibitors of the GABA transporters GAT1, GAT2, and GAT3, significantly reduced this export in a Ca(2+)-independent fashion. Intracellular GABA levels were enhanced by treatment with the GABA-T inhibitors gabaculine or vigabatrin. Treatment with glutamate increased GABA release in a concentration-dependent fashion. This was partially inhibited by blockers of N-methyl-D-aspartate and kainate receptors. Conversely, glycine and D-serine, co-agonists of NMDA receptors, enhanced the GABA release. GABA release was accompanied by an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) and was reduced by adding the Ca(2+) chelator, BAPTA-AM to the medium. These data indicate that astrocytes continuously synthesize GABA and that there are multiple mechanisms which can mediate its release. Each of these may play a role in the physiological functioning of astrocytes. PMID:21748804

Lee, Moonhee; McGeer, Edith G; McGeer, Patrick L



[Antihypoxic properties of GABA-containing vitamin derivatives].  


The antihypoxic properties of GABA-containing vitamin derivatives (pyridoxalphosphate-GABA, picamilone, pantogam, sodium homopantothenate) as compared with GABA were studied. All agents were found to increase mouse life expectancy under hypoxia in contrast to GABA. PMID:2707423

Karaev, A L; Kovler, M A; Avakumov, V M; Kopelevich, V M; Bulanova, L N



GABA Accumulation Causes Cell Elongation Defects and a Decrease in Expression of Genes Encoding Secreted and Cell Wall-Related Proteins in Arabidopsis thaliana  

PubMed Central

GABA (?-aminobutyric acid), a non-protein amino acid, is a signaling factor in many organisms. In plants, GABA is known to accumulate under a variety of stresses. However, the consequence of GABA accumulation, especially in vegetative tissues, remains poorly understood. Moreover, gene expression changes as a consequence of GABA accumulation in plants are largely unknown. The pop2 mutant, which is defective in GABA catabolism and accumulates GABA, is a good model to examine the effects of GABA accumulation on plant development. Here, we show that the pop2 mutants have pollen tube elongation defects in the transmitting tract of pistils. Additionally, we observed growth inhibition of primary root and dark-grown hypocotyl, at least in part due to cell elongation defects, upon exposure to exogenous GABA. Microarray analysis of pop2-1 seedlings grown in GABA-supplemented medium revealed that 60% of genes whose expression decreased encode secreted proteins. Besides, functional classification of genes with decreased expression in the pop2-1 mutant showed that cell wall-related genes were significantly enriched in the microarray data set, consistent with the cell elongation defects observed in pop2 mutants. Our study identifies cell elongation defects caused by GABA accumulation in both reproductive and vegetative tissues. Additionally, our results show that genes that encode secreted and cell wall-related proteins may mediate some of the effects of GABA accumulation. The potential function of GABA as a growth control factor under stressful conditions is discussed.

Renault, Hugues; El Amrani, Abdelhak; Palanivelu, Ravishankar; Updegraff, Emily P.; Yu, Agnes; Renou, Jean-Pierre; Preuss, Daphne; Bouchereau, Alain; Deleu, Carole



Development of GABA innervation in the cerebral and cerebellar cortices  

Microsoft Academic Search

In many areas of the vertebrate brain, such as the cerebral and cerebellar cortices, neural circuits rely on inhibition mediated by GABA (?-aminobutyric acid) to shape the spatiotemporal patterns of electrical signalling. The richness and subtlety of inhibition are achieved by diverse classes of interneurons that are endowed with distinct physiological properties. In addition, the axons of interneurons display highly

G. Di Cristo; F. Ango; Z. J. Huang



GABA(A) receptor characterization and subunit localization in the human sub-ventricular zone.  


It is now well established that the human brain continuously produces new stem cells until well into old age. One of these stem-cell rich areas in the human brain is the sub-ventricular zone (SVZ). The human SVZ is organized in four distinctive layers containing type A, B and C cells. To date, no studies have investigated the distribution of inhibitory neurotransmitters such as ?-aminobutyric acid (GABA) and their respective receptors on the different cell types in the human SVZ. GABA(A) receptors (GABA(A)R) are ubiquitously expressed, inhibitory heteropentameric chloride ion channels comprised of a variety of subunits that are targeted by many prescribed drugs. In this study we present detailed immunohistochemical data on the regional and cellular localization of ??, ??, ?3, ??,? and ?? subunits of GABA(A)R in the human SVZ. The results from our double and triple labeling studies demonstrate that the cell types and subunit composition throughout the SVZ is heterogeneous; the thickness of the SVZ and GABA(A)R ?? and ?? expression is increased especially in the vicinity of large SVZ blood vessels. GABA(A)R ?? is the most specific to the SVZ and present on various cells that express, either glial fibrillary acidic protein (GFAP?) or polysialic acid-neural cell adhesion molecule (PSA-NCAM) separately, or together in a respective ratio of 7:6:2. Proliferating (type C) cells in the SVZ express GAD65/67, GFAP? and GABA(A)R ??,? receptor subunits. Within the SVZ the majority of cells have an unexpected nuclear GABA(A)R ??,? expression that is inversely proportional to that of PCNA (proliferating cell nuclear antigen marker), which is a very different pattern of expression compared with underlying caudate nucleus cells. Taken together our results provide a detailed description of the chemo-architecture of the adult human SVZ demonstrating the importance of GABA and GABA(A) receptors on the various cell types in the SVZ. PMID:23770130

Dieriks, Birger V; Waldvogel, Henry J; Monzo, Hector J; Faull, Richard L M; Curtis, Maurice A



Microperfusion of 3-MPA into the brain augments GABA  

PubMed Central

In vivo effects of microperfusion of a GABA synthesis inhibitor (3-MPA) into the striatum and hippocampus on amino acid concentrations and electrical neuronal activity were investigated. Paradoxical elevations in GABA in the striatum (5-fold in anesthetized and 50-fold in awake rats) and hippocampus (2-fold in anesthetized and 15-fold in awake rats) were documented under steady-state concentrations of 3-MPA along with expected increases in glutamate (a 15-fold increase and a 250-fold increase in the striatum of anesthetized and awake rats, respectively; a 7-fold increase and a 25-fold increase in the hippocampus of anesthetized and awake rats, respectively). There was no clear epileptiform or seizure activity. Explanations for the paradoxical increase in GABA are offered, and emphasis is placed on the dependency of disinhibition on the model in which its effects are studied as well as on the prevailing level of activation of the probed network.

Mayer, Andrew P.; Osorio, Ivan; Lunte, Craig E.



The effects of stiripentol on GABA(A) receptors.  


The anticonvulsant stiripentol (Diacomittm) has been shown to have a positive impact on control of seizures for many patients with Dravet syndrome. As with most antiepileptic drugs, stiripentol has multiple mechanisms of action. Its direct anticonvulsant activity is likely due to enhancement of inhibitory, ?-aminobutyric acid (GABA)ergic neurotransmission. Stiripentol was shown to increase the activity of both neuronal and recombinant GABA(A) receptors at clinically relevant concentrations. At recombinant receptors, stiripentol was found to act through a unique site in a subunit-dependent manner. Positive modulation by stiripentol was most effective at GABA(A) receptors containing an ?3 subunit. The expression of the ?3 subunit is developmentally regulated, with highest levels in the immature brain. This subunit selectivity may explain the greater clinical efficacy of stiripentol in childhood-onset epilepsies, including Dravet syndrome. PMID:21463286

Fisher, Janet L



Does extracellular calcium determine what pool of GABA is the target for alpha-latrotoxin?  


Presynaptic neurotoxin alpha-latrotoxin, from the venom of Latrodectus mactans tredecimguttatus, causes massive [(3)H]GABA release from rat brain synaptosomes, irrespective of calcium presence in the extracellular medium. Whether the binding of alpha-latrotoxin to Ca(2+)-dependent (neurexin 1 alpha) or to Ca(2+)-independent (latrophilin) receptor triggers [(3)H]GABA release by the same mechanisms or different ones, inducing either exocytotic process or outflow by mobile membrane GABA transporter, is unknown. We examined alpha-latrotoxin-evoked [(3)H]GABA release from synaptosomes which cytosolic [(3)H]GABA pool was depleted either by applying competitive inhibitors of the GABA transporter, nipecotic acid and 2,4-diaminobutyric acid, or by permeation with digitonin. We also compared the effect of the GABA transporter inhibitors on depolarisation-evoked and alpha-latrotoxin-evoked [(3)H]GABA release using as depolarising agents 4-aminopyridine and high KCl in the Ca(2+)-containing and in Ca(2+)-free medium, respectively. Incubation of synaptosomes with nipecotic acid induced the essential acceleration of unstimulated [(3)H]GABA release and deep inhibition of high KCl-evoked Ca(2+)-independent [(3)H]GABA release. In contrast, at the similar conditions the effect of alpha-latrotoxin was greatly augmented with respect to the control response. Another way to assay what GABA pool was involved in alpha-latrotoxin-induced release lays in an analysis of the effects of depolarisation and alpha-latrotoxin in consecutive order. The preliminary 4-aminopyridine-stimulated [(3)H]GABA release attenuated the toxin effect. But when depolarisation occurred in Ca(2+)-free medium, no influence on alpha-latrotoxin effect was revealed. Employing digitonin-permeated synaptosomes, we have shown that alpha-latrotoxin could stimulate [3H]GABA release in the medium with 1mM EGTA, this effect of the toxin was blocked by concanavalin A and was ATP-dependent. The latter suggests that alpha-latrotoxin-released neurotransmitter has the vesicular nature. We assume that the type of the toxin membrane receptor does not determine the mechanisms of [(3)H]GABA release evoked by alpha-latrotoxin. PMID:11821145

Storchak, L G; Linetska, M V; Himmelreich, N H



pH-dependent actions of THIP and ZAPA on an ionotropic Drosophila melanogaster GABA receptor.  


The actions of THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) and ZAPA (Z-3-[(aminoiminomethyl)thio]prop-2-enoic acid) were tested on an ionotropic homo-oligomeric GABA receptor of Drosophila melanogaster. The amplitude of currents activated by THIP and ZAPA declined rapidly during agonist application and a rebound response was observed on washout. By correcting the pH shift induced by these acid salts, responses more typical of GABA agonists were seen. Less striking pH-dependence was observed in the case of GABA responses. PMID:8955956

Matsuda, K; Hosie, A M; Buckingham, S D; Squire, M D; Baylis, H A; Sattelle, D B



Decreased GABA and glutamate concentration in rat brain after treatment with 6-aminonicotinamide  

Microsoft Academic Search

The effect of 6-aminonicotinamide (6-AN) on putative amino acid neurotransmitters, namely glutamate, GABA and aspartate was studied on brains of rats treated with this antimetabolite (35 mg\\/kg i.p.).

L. Bielicki; J. Krieglstein



Molecular cloning and functional characterization of a GABA transporter from the CNS of the cabbage looper, Trichoplusia ni.  


A cDNA encoding a GABA transporter in the caterpillar Trichoplusia ni has been cloned and expressed in baculovirus-infected insect cells. The cDNA contains an ORF encoding a 608-residue protein, designated TrnGAT. Hydropathy analysis of the deduced amino acid sequence suggests 12 transmembrane domains, a structure similar to that of all other cloned Na+/Cl(-)-dependent GABA transporters. The deduced amino acid sequence shows high identity with a GABA transporter (MasGAT) expressed in the embryo of Manduca sexta. Expression of TrnGAT mRNA was detected only in the brain. Sf21 cells infected with recombinant baculovirus exhibited a 20- to 30-fold increase in [3H]GABA uptake compared to control-infected cells. Several blockers of GABA uptake were used to determine the pharmacological profile of TrnGAT. Although most similar to mammalian neuronal GABA transporter GAT-1 in its kinetic properties, stoichiometry of ionic dependence and pharmacological properties, TrnGAT may be distinguished from mammalian GAT-1 by the inability of cyclic GABA analogues, such as nipecotic acid and its derivatives, to inhibit GABA uptake by the insect protein. The unique pharmacology of TrnGAT suggests that the GABA transport system in the lepidopteran CNS could be a useful target in the future development of rapidly-acting neuroactive agents used to control agriculturally-important insects. PMID:10436937

Gao, X; McLean, H; Caveney, S; Donly, C



Dose-conductance relationships for GABA agonists and the effect of uptake inhibitors in crayfish stretch receptor neurons.  


The interaction of GABA (gamma-aminobutyric acid) and structurally-related compounds with postsynaptic GABA receptors was studied quantitatively by measuring receptor-mediated increases in membrane input conductance in isolated crayfish stretch receptor neurons (SRN). The following compounds, in order of decreasing potency, were effective agonists: muscimol greater than GABA greater than isoguvacine greater than (-)gamma-amino-beta-hydroxybutyric acid greater than beta-gu anidinopropionic acid greater than 3-aminopropanesulfonic acid greater than (+)gamma-amino-beta-hydroxybutyric acid greater than isonipecotic acid greater than THIP. A highly significant correlation was found between the log potencies for GABA agonists that were obtained in the SRN and those obtained in our laboratory using mammalian GABA receptor binding assays. Hill plot analyses of the log concentration-conductance data from the SRN indicated a Hill slope (nH) of approximately 2 for all agonists except GABA and guanidinopropionic acid (nH greater than 2), two compounds known to be actively accumulated by cellular GABA uptake processes. Nipecotic acid, guvacine, and L-alpha, beta-diaminopropionic acid, blockers of GABA uptake processes, had essentially no effect by themselves on the SRN membrane input conductance at concentrations up to 5 mM, however, they potentiated the effects of sub-maximal concentrations of GABA and decreased the steepness of the log concentration-conductance curve, and consequently nH, for GABA. The effects of muscimol, however, were not affected. When the influence of uptake processes was considered, it appeared that all agonists tested acted by the same cooperative mechanism which required at least two molecules of agonist to activate a receptor-ionophore unit. PMID:7306793

Krause, D N; Ikeda, K; Roberts, E



Four types of neuron in layer IVab of cat cortical area 17 accumulate 3H-GABA.  


Roughly 10% of the neurons in layer IVab of cat area 17 accumulate exogenous 3H-gamma-aminobutyric acid (GABA) but how many types of neuron comprise this population was unknown. We characterized these neurons by partial reconstruction of their somas from serial electron microscope autoradiograms and distinguished four types. GABA 1 was large (greater than 16.5 micron) and dark with a dense distribution of synaptic terminals, substantial geniculate input to the soma, and a moderate accumulation of GABA. GABA 2 was small (less than 13 micron) and pale, also with a dense distribution of terminals but without evidence of somatic geniculate input, and a moderate accumulation of GABA. GABA 3 was radially fusiform (20 micron X 8 micron) with varicose dendrites, a sparse distribution of synaptic terminals, and a heavy accumulation of GABA. GABA 4 was medium in size (15 micron) with a moderate distribution of synaptic terminals and a heavy accumulation of GABA. Reasons are presented for believing that each of these four categories of GABA-accumulating neuron represents a fundamental cell type. PMID:6886063

Hamos, J E; Davis, T L; Sterling, P



A synergistic effect of GABA tea and copper(II) on DNA breakage in human peripheral lymphocytes.  


GABA tea is a tea product that contains a high level of ?-aminobutyric acid (GABA). The oxidant and antioxidant roles of GABA tea in DNA damage were investigated in this study. DNA cleavage was observed by GABA-tea extract in the presence of copper ions. Comet assay revealed that combination of GABA-tea extract, but not pure GABA, and Cu(2+) is capable of oxidatively degrading cellular DNA in human peripheral lymphocytes. Using various reactive oxygen scavengers, we found that catalase and sodium azide effectively inhibited GABA-tea extract/Cu(II)-induced DNA degradation, suggesting the essential role of singlet oxygen and H(2)O(2) in the reaction. In addition, neocuproine inhibited the DNA degradation, confirming that Cu(I) is an intermediate in the DNA cleavage reaction. Therefore, we speculate that GABA-tea extract/Cu(II)-induced DNA damage is probably mediated through the formation of H(2)O(2) and the reduction of copper. Furthermore, our data showed that GABA-tea extract was more genotoxic and pro-oxidant than its major catechin constituent, (-)-epigallocatechin-3-gallate (EGCG), leading to DNA cleavage in the presence of Cu(2+). These findings will provide implications for the potential of GABA-tea extract in anticancer property, which may involve copper ions and the consequent pro-oxidant action. PMID:21195120

Wang, Hsueh-Fang; Chuang, Show-Mei; Hsiao, Ching-Chuan; Cherng, Shur-Hueih



Temperature dependence and GABA modulation of (TH)triazolam binding in the rat brain  

SciTech Connect

The hypnotic triazolam (TZ), a triazolobenzodiazepine displays a short physiological half life and has been used for the treatment of insomnia related to anxiety states. The authors major objectives were the direct measurement of the temperature dependence and the gamma-aminobutyric acid (GABA) effect of (TH)TZ binding in the rat brain. Saturation studies showed a shift to lower affinity with increasing temperatures (K/sub d/ = 0.27 +/- 08 nM at 0C; K/sub d/ = 1.96 +/- 0.85 nM at 37C) while the B/sub max/ values remained unchanged (1220 +/- 176 fmoles/mg protein at 0C and 1160 +/- 383 fmoles/mg protein at 37C). Saturation studies of (TH)TZ binding in the presence or absence of GABA (100 M) showed a GABA-shift. At 0C the K/sub d/ values were (K/sub d/ = 0.24 +/- 0.03 nM/-GABA; K/sub d/ = 0.16 +/- 0.04/+GABA) and at 37C the K/sub d/ values were (K/sub d/ = 1.84 +/- 0.44 nM/-GABA; K/sub d/ = 0.95 +/- 0.29 nM/+GABA). In contrast to reported literature, the authors findings show that TZ interacts with benzodiazepine receptors with a temperature dependence and GABA-shift consistent with predicted behavior for benzodiazepine agonists. 20 references, 3 tables.

Earle, M.E.; Concas, A.; Wamsley, J.K.; Yamamura, H.I.



Actions of the insecticide fipronil, on dieldrin-sensitive and- resistant GABA receptors of Drosophila melanogaster.  

PubMed Central

1. Blocking actions of the novel insecticide, fipronil, were examined on GABA responses recorded from Xenopus oocytes expressing either wild type (dieldrin-sensitive) or mutant (dieldrin-resistant) forms of the Drosophila melanogaster GABA-gated chloride channel homo-oligomer, RDL (the product of the resistance to dieldrin locus: Rdl). 2. In the case of the wild type receptor, fipronil blocked GABA-induced currents inducing both a shift to the right in the GABA dose-response curve and depressing the maximum amplitude of responses to GABA. The potency of fipronil was dependent on the GABA concentration but was unaffected by membrane potential. 3. Mutant RDL GABA-receptors, which have a naturally occurring amino acid substitution (A302-->S) in the putative ion-channel lining region, conferring resistance to dieldrin and picrotoxinin, were markedly less sensitive to fipronil than the wild-type receptors. 4. Fipronil antagonism is qualitatively similar to that produced by the structurally distinct compound, picrotoxinin. As the mutation A302-->S reduces the potency of both fipronil and picrotoxinin, homooligomeric RDL receptors should facilitate detailed studies of the molecular basis of convulsant/insecticide antagonist actions on GABA receptors.

Hosie, A. M.; Baylis, H. A.; Buckingham, S. D.; Sattelle, D. B.



Immunocytochemistry of GABA in the brain and suboesophageal ganglion of Manduca sexta.  


We have used specific antisera against protein-conjugated gamma-aminobutyric acid (GABA) in immunocytochemical preparations to investigate the distribution of putatively GABAergic neurons in the brain and suboesophageal ganglion of the sphinx moth Manduca sexta. About 20,000 neurons per brain hemisphere exhibit GABA-immunoreactivity. Most of these are optic-lobe interneurons, especially morphologically centrifugal neurons of the lamina and tangential neurons that innervate the medulla or the lobula complex. Many GABA-immunoreactive neurons, among them giant fibers of the lobula plate, project into the median protocerebrum. Among prominent GABA-immunoreactive neurons of the median protocerebrum are about 150 putatively negative-feedback fibers of the mushroom body, innervating both the calyces and lobes, and a group of large, fan-shaped neurons of the lower division of the central body. Several commissures in the supra- and suboesophageal ganglion exhibit GABA-like immunoreactivity. In the suboesophageal ganglion, a group of contralaterally descending neurons shows GABA-like immunoreactivity. The frontal ganglion is innervated by immunoreactive processes from the tritocerebrum but does not contain GABA-immunoreactive somata. With few exceptions the brain nerves do not contain GABA-immunoreactive fibers. PMID:3552234

Homberg, U; Kingan, T G; Hildebrand, J G



Modulation of cell surface GABA(B) receptors by desensitization, trafficking and regulated degradation.  


Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. ?-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength. PMID:22558486

Benke, Dietmar; Zemoura, Khaled; Maier, Patrick J



Effect of GABA, a Bacterial Metabolite, on Pseudomonas fluorescens Surface Properties and Cytotoxicity.  


Different bacterial species and, particularly Pseudomonas fluorescens, can produce gamma-aminobutyric acid (GABA) and express GABA-binding proteins. In this study, we investigated the effect of GABA on the virulence and biofilm formation activity of different strains of P. fluorescens. Exposure of a psychotropic strain of P. fluorescens (MF37) to GABA (10-5 M) increased its necrotic-like activity on eukaryotic (glial) cells, but reduced its apoptotic effect. Conversely, muscimol and bicuculline, the selective agonist and antagonist of eukaryote GABAA receptors, respectively, were ineffective. P. fluorescens MF37 did not produce biosurfactants, and its caseinase, esterase, amylase, hemolytic activity or pyoverdine productions were unchanged. In contrast, the effect of GABA was associated to rearrangements of the lipopolysaccharide (LPS) structure, particularly in the lipid A region. The surface hydrophobicity of MF37 was marginally modified, and GABA reduced its biofilm formation activity on PVC, but not on glass, although the initial adhesion was increased. Five other P. fluorescens strains were studied, and only one, MFP05, a strain isolated from human skin, showed structural differences of biofilm maturation after exposure to GABA. These results reveal that GABA can regulate the LPS structure and cytotoxicity of P. fluorescens, but that this property is specific to some strains. PMID:23743829

Dagorn, Audrey; Chapalain, Annelise; Mijouin, Lily; Hillion, Mélanie; Duclairoir-Poc, Cécile; Chevalier, Sylvie; Taupin, Laure; Orange, Nicole; Feuilloley, Marc G J



Effect of GABA, a Bacterial Metabolite, on Pseudomonas fluorescens Surface Properties and Cytotoxicity  

PubMed Central

Different bacterial species and, particularly Pseudomonas fluorescens, can produce gamma-aminobutyric acid (GABA) and express GABA-binding proteins. In this study, we investigated the effect of GABA on the virulence and biofilm formation activity of different strains of P. fluorescens. Exposure of a psychotropic strain of P. fluorescens (MF37) to GABA (10?5 M) increased its necrotic-like activity on eukaryotic (glial) cells, but reduced its apoptotic effect. Conversely, muscimol and bicuculline, the selective agonist and antagonist of eukaryote GABAA receptors, respectively, were ineffective. P. fluorescens MF37 did not produce biosurfactants, and its caseinase, esterase, amylase, hemolytic activity or pyoverdine productions were unchanged. In contrast, the effect of GABA was associated to rearrangements of the lipopolysaccharide (LPS) structure, particularly in the lipid A region. The surface hydrophobicity of MF37 was marginally modified, and GABA reduced its biofilm formation activity on PVC, but not on glass, although the initial adhesion was increased. Five other P. fluorescens strains were studied, and only one, MFP05, a strain isolated from human skin, showed structural differences of biofilm maturation after exposure to GABA. These results reveal that GABA can regulate the LPS structure and cytotoxicity of P. fluorescens, but that this property is specific to some strains.

Dagorn, Audrey; Chapalain, Annelise; Mijouin, Lily; Hillion, Melanie; Duclairoir-Poc, Cecile; Chevalier, Sylvie; Taupin, Laure; Orange, Nicole; Feuilloley, Marc G. J.



GABA-B receptors in the PNS have a role in Schwann cells differentiation?  

PubMed Central

?-aminobutyric acid type B (GABA-B) receptor mediates the inhibitory transmission of ?-aminobutyric acid in the mammalian nervous system, being present in neurons and also in glial cells. Recently the presence of GABA-B has been demonstrated in Schwann cells (SC) suggesting its contribution in regulating the cell fate, maturation, and plasticity. Here, we further support the functional presence of GABA-B receptor in SC plasma membrane. By confocal microscopy immunofluorescence we provide evidences that GABA-B localization on the cell elongated processes correlates with the morphological changes occurring in the differentiated SC. In vivo most of the GABA-B receptors seem to be present in non-myelinating SC, which are committed to ensheath the nociceptive fibers. Therefore, we argue that GABA-B receptors do not control exclusively the in vivo differentiation yielding the myelinating SC, but are also fundamental in regulating the SC plasticity versus the non-myelinating state. Data from the literature and our recent findings corroborate the role of the GABAergic system and GABA-B receptors in the peripheral nervous system, opening new perspectives on the mechanisms controlling the differentiation of SC.

Procacci, Patrizia; Ballabio, Marinella; Castelnovo, Luca F.; Mantovani, Cristina; Magnaghi, Valerio



The Memory-Impairing Effects of Septal GABA Receptor Activation Involve GABAergic Septo-Hippocampal Projection Neurons  

ERIC Educational Resources Information Center

Septal infusions of the [gamma]-aminobutyric acid (GABA)[subscript A] agonist muscimol impair memory, and the effect likely involves the hippocampus. GABA[subscript A] receptors are present on the perikarya of cholinergic and GABAergic septo-hippocampal (SH) projections. The current experiments determined whether GABAergic SH projections are…

Krebs-Kraft, Desiree L.; Wheeler, Marina G.; Parent, Marise B.



Role of GABA Release From Leptin Receptor-Expressing Neurons in Body Weight Regulation  

PubMed Central

It is well established that leptin regulates energy balance largely through isoform B leptin receptor-expressing neurons (LepR neurons) in the brain and that leptin activates one subset of LepR neurons (leptin-excited neurons) while inhibiting the other (leptin-inhibited neurons). However, the neurotransmitters released from LepR neurons that mediate leptin action in the brain are not well understood. Previous results demonstrate that leptin mainly acts on ?-aminobutyric acid (GABA)ergic neurons to reduce body weight, and that leptin activates proopiomelanocortin neuron activity by reducing GABA release onto these neurons, suggesting a body weight-promoting role for GABA released from leptin-inhibited neurons. To directly examine the role of GABA release from LepR neurons in body weight regulation, mice with disruption of GABA release specifically from LepR neurons were generated by deletion of vesicular GABA transporter in LepR neurons. Interestingly, these mice developed mild obesity on chow diet and were sensitive to diet-induced obesity, which were associated with higher food intake and lower energy expenditure. Moreover, these mice showed blunted responses in both food intake and body weight to acute leptin administration. These results demonstrate that GABA plays an important role in mediating leptin action. In combination with the previous studies that leptin reduces GABA release onto proopiomelanocortin neurons through leptin-inhibited neurons and that disruption of GABA release from agouti gene-related protein neurons, one subset of LepR-inhibited neurons, leads to a lean phenotype, our results suggest that, under our experimental conditions, GABA release from leptin-excited neuron dominates over leptin-inhibited ones.

Xu, Yuanzhong; O'Brien, William G.; Lee, Cheng-Chi; Myers, Martin G.



GABA metabolism pathway genes, UGA1 and GAD1, regulate replicative lifespan in Saccharomycescerevisiae  

SciTech Connect

Highlights: {yields}We demonstrate that two genes in the yeast GABA metabolism pathway affect aging. {yields} Deletion of the UGA1 or GAD1 genes extends replicative lifespan. {yields} Addition of GABA to wild-type cultures has no effect on lifespan. {yields} Intracellular GABA levels do not differ in longevity mutants and wild-type cells. {yields} Levels of tricarboxylic acid cycle intermediates positively correlate with lifespan. -- Abstract: Many of the genes involved in aging have been identified in organisms ranging from yeast to human. Our previous study showed that deletion of the UGA3 gene-which encodes a zinc-finger transcription factor necessary for {gamma}-aminobutyric acid (GABA)-dependent induction of the UGA1 (GABA aminotransferase), UGA2 (succinate semialdehyde dehydrogenase), and UGA4 (GABA permease) genes-extends replicative lifespan in the budding yeast Saccharomycescerevisiae. Here, we found that deletion of UGA1 lengthened the lifespan, as did deletion of UGA3; in contrast, strains with UGA2 or UGA4 deletions exhibited no lifespan extension. The {Delta}uga1 strain cannot deaminate GABA to succinate semialdehyde. Deletion of GAD1, which encodes the glutamate decarboxylase that converts glutamate into GABA, also increased lifespan. Therefore, two genes in the GABA metabolism pathway, UGA1 and GAD1, were identified as aging genes. Unexpectedly, intracellular GABA levels in mutant cells (except for {Delta}uga2 cells) did not differ from those in wild-type cells. Addition of GABA to culture media, which induces transcription of the UGA structural genes, had no effect on replicative lifespan of wild-type cells. Multivariate analysis of {sup 1}H nuclear magnetic resonance spectra for the whole-cell metabolite levels demonstrated a separation between long-lived and normal-lived strains. Gas chromatography-mass spectrometry analysis of identified metabolites showed that levels of tricarboxylic acid cycle intermediates positively correlated with lifespan extension. These results strongly suggest reduced activity of the GABA-metabolizing enzymes extends lifespan by shifting carbon metabolism toward respiration, as calorie restriction does.

Kamei, Yuka; Tamura, Takayuki [Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829 (Japan)] [Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829 (Japan); Yoshida, Ryo [Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)] [Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Ohta, Shinji [Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829 (Japan)] [Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829 (Japan); Fukusaki, Eiichiro [Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)] [Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Mukai, Yukio, E-mail: [Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829 (Japan)] [Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829 (Japan)



GABA May Act as a Self-Limiting Trophic Factor at Developing Synapses  

NSDL National Science Digital Library

Early in development, synapses with glycine or γ-aminobutyric acid (GABA)-gated chloride channels exhibit the ability to depolarize postsynaptic cells. As the synapses mature and the gradient of chloride ions across the cell membrane is altered, these neurotransmitters signal an inhibitory response, hyperpolarizing the membrane and decreasing neuronal excitability. Kriegstein and Owens discuss how GABA-stimulated up-regulation of the expression of the potassium chloride cotransporter KCC2 may be the mechanism underlying this synaptic switch.

Arnold R. Kriegstein (Columbia College of Physicians and Surgeons;Department of Neurology and Department of Pathology and at the Center for Neurobiology and Behavior REV); David F. Owens (Columbia College of Physicians and Surgeons;Department of Neurology and Department of Pathology and at the Center for Neurobiology and Behavior REV)



An association study between polymorphisms in five genes in glutamate and GABA pathway and paranoid schizophrenia  

Microsoft Academic Search

Dysfunctions of glutamatergic and GABAergic neurotransmission are two important hypotheses for the pathogenesis of schizophrenia. Thus, genes in the pathway are candidates for schizophrenia susceptibility. Phosphate-activated glutaminase (GLS), glutamine synthetase (GLUL), glutamic acid decarboxylase (GAD), GABA transaminase (ABAT) and succinic semialdehyde dehydrogenase (ALDH5A1) are five primary enzymes in glutamate and GABA synthetic and degradative pathway. In order to investigate the

Boyu Zhang; Yanbo Yuan; Yanbin Jia; Xin Yu; Qi Xu; Yucun Shen; Yan Shen



Action of tremorgenic mycotoxins on GABA/sub A/ receptor  

SciTech Connect

The effects of four tremorgenic and one nontremorgenic mycotoxins were studied on ..gamma..-aminobutyric acid (GABA/sub A/) receptor binding and function in rat brain and on binding of a voltage-operated Cl/sup -/ channel in Torpedo electric organ. None of the mycotoxins had significant effect on (/sup 3/H)muscimol or (/sup 3/H)flunitrazepam binding to the GAMA/sup A/ receptor. However, only the four tremorgenic mycotoxins inhibited GABA-induced /sup 36/Cl/sup -/ influx and (/sup 35/S)t-butylbicyclophosphorothionate ((/sup 35/S)TBPS) binding in rate brain membranes, while the nontremorgenic verruculotoxin had no effect. Inhibition of (/sup 35/S)TBPS binding by paspalinine was non-competitive. This suggests that tremorgenic mycotoxins inhibit GABA/sub A/ receptor function by binding close to the receptor's Cl/sup -/ channel. On the voltage-operated Cl/sup -/ channel, only high concentrations of verruculogen and verruculotoxin caused significant inhibition of the channel's binding of (/sup 35/S)TBPS. The data suggest that the tremorgenic action of these mycotoxins may be due in part to their inhibition of GABA/sub A/ receptor function. 21 references, 4 figures, 2 tables.

Gant, D.B.; Cole, R.J.; Valdes, J.J.; Eldefrawi, M.E.; Eldefrawi, A.T.



A Neuronal Glutamate Transporter Contributes to Neurotransmitter GABA Synthesis and Epilepsy  

PubMed Central

The predominant neuronal glutamate transporter, EAAC1 (for excitatory amino acid carrier-1), is localized to the dendrites and somata of many neurons. Rare presynaptic localization is restricted to GABA terminals. Because glutamate is a precursor for GABA synthesis, we hypothesized that EAAC1 may play a role in regulating GABA synthesis and, thus, could cause epilepsy in rats when inactivated. Reduced expression of EAAC1 by antisense treatment led to behavioral abnormalities, including staring–freezing episodes and electrographic (EEG) seizures. Extracellular hippocampal and thalamocortical slice recordings showed excessive excitability in antisense-treated rats. Patch-clamp recordings of miniature IPSCs (mIPSCs) conducted in CA1 pyramidal neurons in slices from EAAC1 antisense-treated animals demonstrated a significant decrease in mIPSC amplitude, indicating decreased tonic inhibition. There was a 50% loss of hippocampal GABA levels associated with knockdown of EAAC1, and newly synthesized GABA from extracellular glutamate was significantly impaired by reduction of EAAC1 expression. EAAC1 may participate in normal GABA neurosynthesis and limbic hyperexcitability, whereas epilepsy can result from a disruption of the interaction between EAAC1 and GABA metabolism.

Sepkuty, Jehuda P.; Cohen, Akiva S.; Eccles, Christine; Rafiq, Azhar; Behar, Kevin; Ganel, Raquelli; Coulter, Douglas A.; Rothstein, Jeffrey D.



Stability of GABA levels in CSF under various conditions of storage.  


Measurement of GABA in human lumbar CSF specimens stored under various conditions showed that the concentrations remained stable in untreated frozen specimens stored at -20 degrees C and at -70 degrees C. In untreated liquid specimens the GABA concentrations approximately doubled during 2 h at room temperature but did not change significantly during 10 min at room temperature or 2 h at 2-4 degrees C. The GABA level was stable at -70 degrees C in deproteinized specimens but doubled during 11 months of storage at -20 degrees C. The level was stable in liquid deproteinized samples for 49 h at room temperature but increased 1.3-fold and 2.0-fold in deproteinized specimens stored for 3 weeks at 2-4 degrees C and room temperature, respectively. Amino acid analyses of homocarnosine standards in 0.1 N HCl revealed a similar increase of GABA during storage at room temperature and at -20 degrees C, suggesting that at least part of the increase seen in CSF specimens might result from breakdown of GABA containing peptides. This instability of GABA level may account for some of the discrepancies among the reports of CSF GABA levels. PMID:7350995

Grossman, M H; Hare, T A; Manyam, N V; Glaeser, B S; Wood, J H



Regulation of (/sup 3/H)GABA release from strips of guinea pig urinary bladder  

SciTech Connect

The presence of receptors that regulate the release of gamma-aminobutyric acid (GABA) was studied in strips of the guinea pig urinary bladder. GABA (10(-8)-10(-5) M) and muscimol (10(-8)-10(-5) M), but not baclofen (10(-5) M), reduced the Ca2+-dependent, tetrodotoxin-resistant release of (/sup 3/H)GABA evoked by high K+ from the urinary bladder strips preloaded with (/sup 3/H)GABA. The inhibitory effect of muscimol was antagonized by bicuculline and potentiated by diazepam, clonazepam, and pentobarbital sodium. The potentiating effect of clonazepam was antagonized by Ro 15-1788. Acetylcholine (ACh) inhibited the high K+-evoked release of (/sup 3/H)GABA. The inhibitory effect of ACh was antagonized by atropine sulfate and pirenzepine but not by hexamethonium. Norepinephrine (NE) inhibited the evoked release of (/sup 3/H)GABA. The inhibitory effect of NE was mimicked by clonidine, but not by phenylephrine, and was antagonized by yohimbine but not by prazosin. These results provide evidence that the release of GABA from strips of guinea pig urinary bladder is regulated via the bicuculline-sensitive GABAA receptor, M1-muscarinic, and alpha 2-adrenergic receptors.

Shirakawa, J.; Taniyama, K.; Iwai, S.; Tanaka, C.



Correlation between the enhancement of flunitrazepam binding by GABA and seizure susceptibility in mice  

SciTech Connect

Various populations of mice exhibit differential sensitivity to seizure-inducing agents. The relationship of seizure susceptibility to alterations in the GABA receptor complex was investigated in six different populations of mice consisting of four inbred strains (C57BL, DBA, C3H, and BALB) and two selected lines (long sleep and short sleep). Seizure activity was induced by intraperitoneal administration of the GAD inhibitor, 3-mercaptopropionic acid, and latencies to seizure onset and tonus were measured. In naive mice of the same populations, GABA enhancement of TH-flunitrazepam binding was measured in extensively washed whole brain membranes at several GABA concentrations. Both differential seizure sensitivity to 3-mercaptopropionic acid and differential enhancement of TH-flunitrazepam binding by GABA were observed in these six populations of mice. Correlational analyses indicated a positive correlation between the degree of GABA enhancement of TH-flunitrazepam binding and resistance to the seizure-inducing properties of 3-mercaptopropionic acid. These data suggest that genetic differences in sensitivity to seizure-inducing agents that disrupt the GABAergic system may be related to differences in coupling between the various receptors associated with the GABA receptor complex.

Marley, R.J.; Wehner, J.M.



Comparison of taurine, GABA, Glu, and Asp as scavengers of malondialdehyde in vitro and in vivo  

NASA Astrophysics Data System (ADS)

The purpose of this study is to determine if amino acid neurotransmitters such as gamma-aminobutyric acid (GABA), taurine, glutamate (Glu), and aspartate (Asp) can scavenge activated carbonyl toxicants. In vitro, direct reaction between malondialdehyde (MDA) and amino acids was researched using different analytical methods. The results indicated that scavenging activated carbonyl function of taurine and GABA is very strong and that of Glu and Asp is very weak in pathophysiological situations. The results provided perspective into the reaction mechanism of taurine and GABA as targets of activated carbonyl such as MDA in protecting nerve terminals. In vivo, we studied the effect of taurine and GABA as antioxidants by detecting MDA concentration and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. It was shown that MDA concentration was decreased significantly, and the activities of SOD and GSH-Px were increased significantly in the cerebral cortex and hippocampus of acute epileptic state rats, after the administration of taurine and GABA. The results indicated that the peripherally administered taurine and GABA can scavenge free radicals and protect the tissue against activated carbonyl in vivo and in vitro.

Deng, Yan; Wang, Wei; Yu, Pingfeng; Xi, Zhijiang; Xu, Lijian; Li, Xiaolong; He, Nongyue



The two-step biotransformation of monosodium glutamate to GABA by Lactobacillus brevis growing and resting cells.  


Gama-aminobutyric acid (GABA) is a natural functional amino acid. In the current study, Lactobacillus brevis TCCC13007, a high GABA-producing strain, was isolated from naturally pickled Chinese vegetables. A two-step cellular bioconversion process was established using L. brevis TCCC13007 for the production of GABA. First, L. brevis cells were grown anaerobically in 7% monosodium glutamate (MSG)-containing medium at an initial pH of 6.0 and a controlled pH of 4.6 for 16 to 66 h; approximately 38 g L(-1) of GABA was obtained after 66 h of fermentation at a conversion rate of 98.6%. In the second stage of the process, about 7.6 g L(-1) of GABA was produced three more times at a conversion rate of 92.2% using the same batch of resting cells in the substrate-containing buffer under optimized conditions. Thus, the total GABA yield reached 61 g L(-1). A model system for the biotransformation of MSG to GABA was established using L. brevis TCCC13007 resting cells. The reaction rates were found to follow the classic Michaelis-Menten equation at low substrate concentrations (<80 mM). Kinetic analysis of the biotransformation revealed that L. brevis TCCC13007 resting cells produced GABA similar to that produced by purified glutamate decarboxylase from L. brevis. PMID:22307498

Zhang, Ying; Song, Lei; Gao, Qiang; Yu, Shao Mei; Li, Lei; Gao, Nian Fa



GABA-B receptor activation inhibits the in vitro migration of malignant hepatocytes.  


There are conflicting data regarding whether activation of ?-aminobutyric acid-B (GABA-B) receptors results in inhibition of tumor growth and invasion. The objectives of this study were to document the effects of the GABA-B receptor agonist baclofen on malignant hepatocyte proliferation and migration. We also sought to determine whether any effects on cell migration were mediated by changes in cyclic adenosine monophosphate (cAMP) signaling or matrix metalloproteinase (MMP) expression. Finally, GABA-B(1) and -B(2) receptor expression was documented in 2 malignant hepatocyte cell lines (PLC/PRF/5 and Huh-7) and 12 sets of human hepatocellular carcinoma and adjacent nontumor tissues. Cell proliferative activity was documented by WST-1 absorbance, migration by wound healing assays, cAMP levels by enzyme-linked immunoassay (ELISA), MMP by immunohistochemistry and ELISA, and GABA-B receptor expression by flow cytometry and reverse transcriptase - polymerase chain reaction. Although baclofen had no effect on cell proliferation, wound healing was delayed, an effect that was reversed by the GABA-B receptor antagonist CGP. cAMP levels were decreased in Huh-7 but not PLC cells exposed to baclofen. MMP expression remained unaltered in both cell lines. Finally, GABA-B(1) receptor expression was present and consistently expressed, but GABA-B(2) expression was limited and varied with the number of cell passages and (or) duration of culture. In conclusion, activation of GABA-B receptors has no effect on malignant hepatocyte proliferation but does decrease cell migration. This inhibitory effect may involve cAMP signaling but not MMP expression. GABA-B(2) receptor expression is limited and variable, which may help to explain discrepancies with previously published results. PMID:21762014

Lodewyks, Carly; Rodriguez, Jose; Yan, Jing; Lerner, Betty; Lipschitz, Jeremy; Nfon, Charles; Rempel, Julia Darlene; Uhanova, Julia; Minuk, Gerald Yosel



GABA-A Channel Subunit Expression in Human Glioma Correlates with Tumor Histology and Clinical Outcome  

PubMed Central

GABA (?-aminobutyric acid) is the main inhibitory neurotransmitter in the CNS and is present in high concentrations in presynaptic terminals of neuronal cells. More recently, GABA has been ascribed a more widespread role in the control of cell proliferation during development where low concentrations of extrasynaptic GABA induce a tonic activation of GABA receptors. The GABA-A receptor consists of a ligand-gated chloride channel, formed by five subunits that are selected from 19 different subunit isoforms. The functional and pharmacological properties of the GABA-A channels are dictated by their subunit composition. Here we used qRT-PCR to compare mRNA levels of all 19 GABA-A channel subunits in samples of human glioma (n?=?29) and peri-tumoral tissue (n?=?5). All subunits except the ?1 and ?3 subunit were consistently detected. Lowest mRNA levels were found in glioblastoma compared to gliomas of lower malignancy, except for the ? subunit. The expression and cellular distribution of the ?1, ?1, ?2 and ? subunit proteins was investigated by immunohistochemistry on tissue microarrays containing 87 gliomas grade II. We found a strong co-expression of ?2 and ? subunits in both astrocytomas (r?=?0.86, p<0.0001) and oligodendroglial tumors (r?=?0.66, p<0.0001). Kaplan-Meier analysis and Cox proportional hazards modeling to estimate the impact of GABA-A channel subunit expression on survival identified the ?2 subunit (p?=?0.043) but not the ? subunit (p?=?0.64) as an independent predictor of improved survival in astrocytomas, together with established prognostic factors. Our data give support for the presence of distinct GABA-A channel subtypes in gliomas and provide the first link between specific composition of the A-channel and patient survival.

Smits, Anja; Jin, Zhe; Elsir, Tamador; Pedder, Hugo; Nister, Monica; Alafuzoff, Irina; Dimberg, Anna; Edqvist, Per-Henrik; Ponten, Fredrik; Aronica, Eleonora; Birnir, Bryndis



Estimation of ambient GABA levels in layer I of the mouse neonatal cortex in brain slices  

PubMed Central

GABAergic synapses on Cajal–Retzius neurons in layer I of the murine neocortex experience GABAB receptor (GABABR)-mediated tonic inhibition. Extracellular GABA concentration ([GABA]o) that determines the strength of GABABR-mediated inhibition is controlled by GABA transporters (GATs). In this study, we hypothesized that the strength ofpresynaptic GABABR activation reflects [GABA]o in the vicinity of synaptic contacts. Slices obtained from two age groups were used, namely postnatal days (P)2–3 and P5–7. GABAergic postsynaptic currents (IPSCs) were recorded using the whole-cell patch-clamp technique. Minimal electrical stimulation in layer I was applied to elicit evoked IPSCs (eIPSCs) using a paired-pulse protocol. Three parameters were selected for comparison: the mean eIPSC amplitude, paired-pulse ratio, and failure rate. When GAT-1 and GAT-2/3 were blocked by NO-711 (10 ?m) and SNAP-5114 (40 ?m), respectively, no tonic GABABR-mediated inhibition was observed. In order to restore the control levels of GABABR-mediated inhibition, 250 and 125 nm exogenous GABA was required at P2–3 and P5–7, respectively. Addition of 3-mercaptopropionic acid, a glutamate decarboxylase inhibitor, did not significantly change the obtained values arguing against the suggestion that a mechanism different from GATs contributes to [GABA]o control. We conclude that juxtasynaptic [GABA]o is higher (about 250 nm) at P2–3 than at P5–7 (about 125 nm). As both radial cell migration and corticogenesis in general are strongly dependent on [GABA]o and the formation of the last layer 2/3 is finished by P4 in rodents, the observed [GABA]o reduction in layer I might reflect this crucial event in the cortical development.

Dvorzhak, Anton; Myakhar, Olga; Unichenko, Petr; Kirmse, Knut; Kirischuk, Sergei



The cell death factor, cell wall elicitor of rice blast fungus (Magnaporthe grisea) causes metabolic alterations including GABA shunt in rice cultured cells  

PubMed Central

An elicitor derived from the cell wall of rice blast fungus (Magnaporthe grisea) causes cell death in suspension cultured cells of rice (Oryza sativa L.). To elucidate the role of M. grisea elicitor on metabolic pathway of rice cells, we performed metabolite profiling using capillary electrophoresis-mass spectrometry (CE/MS). Treatment with M. grisea elicitor increased the amounts of antioxidants and free amino acids and decreased the amount of metabolites in the tricarboxylic acid (TCA) cycle. Lower ATP concentration caused aberrant energy charge, concurrently with reduced amount of NAD(P)H in elicitor treated cells. Among free amino acids detected in this study, the level of gamma-aminobutyric acid (GABA) increased. GABA is metabolized through a bypass pathway of the TCA cycle called GABA shunt, which is composed of glutamate decarboxylase (GAD), GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH). While M. grisea elicitor negligibly affected GAD and SSADH, GABA-T activity significantly decreased. The decrease in GABA-T activity was recovered by NADPH oxidase inhibitor, which prevents cell death induced by M. grisea elicitor. Thus, GABA accumulation observed in rice cells under elicitor stress is partly associated with GABA-T activity.

Matsumura, Hideo; Kawai-Yamada, Maki; Uchimiya, Hirofumi



The Arabidopsis pop2-1 mutant reveals the involvement of GABA transaminase in salt stress tolerance  

PubMed Central

Background GABA (?-aminobutyric acid) is a non protein amino acid that has been reported to accumulate in a number of plant species when subjected to high salinity and many other environmental constraints. However, no experimental data are to date available on the molecular function of GABA and the involvement of its metabolism in salt stress tolerance in higher plants. Here, we investigated the regulation of GABA metabolism in Arabidopsis thaliana at the metabolite, enzymatic activity and gene transcription levels upon NaCl stress. Results We identified the GABA transaminase (GABA-T), the first step of GABA catabolism, as the most responsive to NaCl. We further performed a functional analysis of the corresponding gene POP2 and demonstrated that the previously isolated loss-of-function pop2-1 mutant was oversensitive to ionic stress but not to osmotic stress suggesting a specific role in salt tolerance. NaCl oversensitivity was not associated with overaccumulation of Na+ and Cl- but mutant showed a slight decrease in K+. To bring insights into POP2 function, a promoter-reporter gene strategy was used and showed that POP2 was mainly expressed in roots under control conditions and was induced in primary root apex and aerial parts of plants in response to NaCl. Additionally, GC-MS- and UPLC-based metabolite profiling revealed major changes in roots of pop2-1 mutant upon NaCl stress including accumulation of amino acids and decrease in carbohydrates content. Conclusions GABA metabolism was overall up-regulated in response to NaCl in Arabidopsis. Particularly, GABA-T was found to play a pivotal function and impairment of this step was responsible for a decrease in salt tolerance indicating that GABA catabolism was a determinant of Arabidopsis salt tolerance. GABA-T would act in salt responses in linking N and C metabolisms in roots.



Isoniazid-induced elevation of CSF GABA levels and effects on chorea in Huntington's disease.  


A randomized, double-blind, crossover, placebo-controlled clinical trial of oral isoniazid was undertaken in eight men with known Huntington's disease. Six completed the trial. Overall chorea scores indicated some amelioration, but clinical improvement was noticed in only two patients and was mild. Side effects included anorexia and elevation of liver enzyme levels. Cerebrospinal fluid (CSF) and plasma gamma-aminobutyric acid (GABA) concentrations were measured simultaneously. Mean CSF GABA increased threefold following treatment with isoniazid (414 +/- 52 SEM pmol/ml) compared to placebo (120 +/- 11 pmol/ml). No significant changes occurred in plasma GABA levels between the placebo and drug treatment phases. Reversal of central GABA deficiency appears not to correct extrapyramidal symptoms in Huntington's disease. PMID:6455963

Manyam, B V; Katz, L; Hare, T A; Kaniefski, K; Tremblay, R D



Concomitant distribution shift of glial GABA transporter and S100 calcium-binding proteins in the rat retina after kainate-induced excitotoxic injury  

Microsoft Academic Search

The goal of this study was to elucidate the involvement of neuronal and glial calcium-binding proteins in the stimulation of ?-aminobutyric acid (GABA) transport system by kainate-induced excitotoxicity in the rat retina. We used immunohistochemical method to assess the localization of GABA reuptake and calcium-binding proteins. After systemic administration of kainate, the neuronal GABA transporter does not show an association

Donghou Kim; Mi Jung Kim; Jong Hwan Lee; Jin Ok Im; Yu Jin Won; Seung-Yong Yoon; Hea Nam Hong



Coming to term with GABA  


Oxytocin, the most powerful uterotonic agent known, is released from the pituitary gland in large amounts during parturition in all placental mammals studied so far, including humans. Although parturition can proceed in its absence, oxytocin is thought to play an important role (see Russell & Leng, 1998). In the rat, pregnancy normally lasts for 21 days. About 24 h before the pups are born, increased production of prostaglandins by the uterus induces luteolysis, and ovarian progesterone production falls dramatically. This fall is an essential prelude to parturition; if prevented, then the rat pups will remain unborn. The fall leads to a further increase in prostaglandin production, and, directly or indirectly, to a host of changes that prepare the uterus and birth canal for parturition. In the last few hours of pregnancy, oxytocin receptors appear in high concentrations in the uterus, and establish a positive-feedback loop between the uterus and the hypothalamic oxytocin system. Uterine contractions, triggered by prostaglandins, excite the oxytocin cells, and oxytocin release triggers further prostaglandin production and further uterine contraction. Thus progesterone plays a critical role in the timing of parturition through its peripheral actions (see Leng & Brown, 1997). A paper in this issue of The Journal of Physiology (Brussaard et al. 1999) suggests that actions of progesterone at the oxytocin cells in the hypothalamus may also be important for parturition. Classically, progesterone acts through specific intracellular receptors to regulate gene expression. However, metabolites of progesterone can also have membrane actions, and in particular, allopregnanolone can act at GABAA receptors to potentiate the actions of GABA, depending upon the particular subunit composition of the receptor. GABA is an important neurotransmitter for oxytocin cells about 45 % of all synapses onto them contain GABA, and the total number of GABA synapses in the supraoptic nucleus is substantially higher in lactating animals than in virgins (El Majdoubi et al. 1997). The GABA innervation appears to play a role in patterning the pulsatile discharge of oxytocin cells that is observed both during parturition and during suckling-induced reflex milk ejection (Moos, 1995; Voisin et al. 1995). Brussaard et al. (1999) recorded GABAA receptor-mediated spontaneous monoquantal inhibitory postsynaptic currents (sIPSCs) from rat supraoptic neurones in hypothalamic slices in vitro. They found a higher incidence of sIPSCs in pregnant rats than in virgin rats, consistent with the observations of an increase in the density of GABA-containing synaptic boutons. Importantly, the sIPSCs were markedly prolonged in the presence of allopregnanolone. Taking into account the frequency and amplitude of sIPSCs, the action of allopregnanolone and the hypertrophy of oxytocin neurones in lactation (reflected in increased capacitance), Brussaard et al. (1999) inferred that the effective GABAA receptor-mediated synaptic current density was much greater in pregnant rats than in virgin or lactating rats. Thus the collapse of progesterone production at term may abruptly reduce the effectiveness of GABA inhibition, and thereby enhance the excitability of oxytocin cells. Clearly this may be important during parturition, but the effect may not persist for long. Indeed, within a day the duration of sIPSCs is significantly longer in the absence of allopregnanolone, which now has no significant effect. This seems to be due to a rapid switch in the types of a subunits inserted into the GABAA receptors. By mid-lactation, a massive change in expression of GABAA receptor subunit mRNAs is apparent. With competitive polymerase chain reaction Brussaard and colleagues found that, while the expression of both a1 and a2 subunit mRNAs was increased, the ratio of a1 : a2 subunit mRNA expression was changed 8-fold in favour of a2 subunit mRNA. (ABSTRACT TRUNCATED) PMID:10087358

Leng; Russell



Airway epithelium is a predominant source of endogenous airway GABA and contributes to relaxation of airway smooth muscle tone  

PubMed Central

Chronic obstructive pulmonary disease and asthma are characterized by hyperreactive airway responses that predispose patients to episodes of acute airway constriction. Recent studies suggest a complex paradigm of GABAergic signaling in airways that involves GABA-mediated relaxation of airway smooth muscle. However, the cellular source of airway GABA and mechanisms regulating its release remain unknown. We questioned whether epithelium is a major source of GABA in the airway and whether the absence of epithelium-derived GABA contributes to greater airway smooth muscle force. Messenger RNA encoding glutamic acid decarboxylase (GAD) 65/67 was quantitatively measured in human airway epithelium and smooth muscle. HPLC quantified GABA levels in guinea pig tracheal ring segments under basal or stimulated conditions with or without epithelium. The role of endogenous GABA in the maintenance of an acetylcholine contraction in human airway and guinea pig airway smooth muscle was assessed in organ baths. A 37.5-fold greater amount of mRNA encoding GAD 67 was detected in human epithelium vs. airway smooth muscle cells. HPLC confirmed that guinea pig airways with intact epithelium have a higher constitutive elution of GABA under basal or KCl-depolarized conditions compared with epithelium-denuded airway rings. Inhibition of GABA transporters significantly suppressed KCl-mediated release of GABA from epithelium-intact airways, but tetrodotoxin was without effect. The presence of intact epithelium had a significant GABAergic-mediated prorelaxant effect on the maintenance of contractile tone. Airway epithelium is a predominant cellular source of endogenous GABA in the airway and contributes significant prorelaxant GABA effects on airway smooth muscle force.

Townsend, Elizabeth; Yim, Peter; Virag, Laszlo; Zhang, Yi; Xu, Dingbang; Bacchetta, Matthew; Emala, Charles W.



Genetic Modulation of GABA Levels in the Anterior Cingulate Cortex by GAD1 and COMT  

PubMed Central

?-Aminobutyric acid (GABA)-ergic transmission is critical for normal cortical function and is likely abnormal in a variety of neuropsychiatric disorders. We tested the in vivo effects of variations in two genes implicated in GABA function on GABA concentrations in prefrontal cortex of living subjects: glutamic acid decarboxylase 1 (GAD1), which encodes GAD67, and catechol-o-methyltransferase (COMT), which regulates synaptic dopamine in the cortex. We studied six single nucleotide polymorphisms (SNPs) in GAD1 previously associated with risk for schizophrenia or cognitive dysfunction and the val158met polymorphism in COMT in 116 healthy volunteers using proton magnetic resonance spectroscopy. Two of the GAD1 SNPs (rs1978340 (p=0.005) and rs769390 (p=0.004)) showed effects on GABA levels as did COMT val158met (p=0.04). We then tested three SNPs in GAD1 (rs1978340, rs11542313, and rs769390) for interaction with COMT val158met based on previous clinical results. In this model, rs11542313 and COMT val158met showed significant main effects (p=0.001 and 0.003, respectively) and a trend toward a significant interaction (p=0.05). Interestingly, GAD1 risk alleles for schizophrenia were associated with higher GABA/Cre, and Val-Val homozygotes had high GABA/Cre levels when on a GAD1 risk genotype background (N=6). These results support the importance of genetic variation in GAD1 and COMT in regulating prefrontal cortical GABA function. The directionality of the effects, however, is inconsistent with earlier evidence of decreased GABA activity in schizophrenia.

Marenco, Stefano; Savostyanova, Antonina A; van der Veen, Jan Willem; Geramita, Matthew; Stern, Alexa; Barnett, Alan S; Kolachana, Bhaskar; Radulescu, Eugenia; Zhang, Fengyu; Callicott, Joseph H; Straub, Richard E; Shen, Jun; Weinberger, Daniel R



GABA(B) receptor GTP-binding is decreased in the prefrontal cortex but not the hippocampus of aged rats.  


Gamma aminobutyric acid (GABA)(B) receptors (GABA(B)Rs) have been linked to a wide range of physiological and cognitive processes and are of interest for treating a number of neurodegenerative and psychiatric disorders. As many of these diseases are associated with advanced age, it is important to understand how the normal aging process impacts GABA(B)R expression and signaling. Thus, we investigated GABA(B)R expression and function in the prefrontal cortex (PFC) and hippocampus of young and aged rats characterized in a spatial learning task. Baclofen-stimulated GTP-binding and GABA(B)R1 and GABA(B)R2 proteins were reduced in the prefrontal cortex of aged rats but these reductions were not associated with spatial learning abilities. In contrast, hippocampal GTP-binding was comparable between young and aged rats but reduced hippocampal GABA(B)R1 expression was observed in aged rats with spatial learning impairment. These data demonstrate marked regional differences in GABA(B)R complexes in the adult and aged brain and could have implications for both understanding the role of GABAergic processes in normal brain function and the development of putative interventions that target this system. PMID:22169202

McQuail, Joseph A; Bañuelos, Cristina; LaSarge, Candi L; Nicolle, Michelle M; Bizon, Jennifer L



A Simple Method for Determining the Absolute Configuration of a-Amino Acids  

NASA Astrophysics Data System (ADS)

The reaction of [Pd(dmba)(acac)] (dmba = C6H4CH2NMe2-2 or 2-[(dimethylamino)methyl]phenyl-C1,N; acac = C5H7O2 or acetylacetonate) with optically pure a-amino acids (HAa, 1:1 molar ratio) [HAa = S-alanine, S-2-amino butyric acid, R-2-amino butyric acid, (2S,3S)-isoleucine, (2S,3R)-threonine and S-asparagine] in refluxing MeOH results in the formation of the corresponding neutral complexes [Pd(dmba)(Aa)] in good yield. The CD (circular dichroism) spectra of these complexes have been measured. The analysis of the shape of the CD curves reveals that all complexes with the same configuration at Ca display similar CD curves, whereas complexes with opposite configuration at Ca display CD curves that are mirror images. Thus, these complexes could be used as analytical tools in the assignment of absolute configurations of a-amino acids.

Díaz-de-Villegas, María Dolores; Urriolabeitia, Esteban P.



Expression cloning of GABAB receptors uncovers similarity to metabotropic glutamate receptors  

Microsoft Academic Search

GABA (gamma-amino-butyric acid), the principal inhibitory neurotransmitter in the brain, signals through ionotropic (GABAA\\/GABAC) and metabotropic (GABAB) receptor systems. Here we report the cloning of GABAB receptors. Photoaffinity labelling experiments suggest that the cloned receptors correspond to two highly conserved GABAB receptor forms present in the vertebrate nervous system. The cloned receptors negatively couple to adenylyl cyclase and show sequence

Klemens Kaupmann; Katharina Huggel; Jakob Heid; Peter J. Flor; Serge Bischoff; Stuart J. Mickel; Gary McMaster; Christof Angst; Helmut Bittiger; Wolfgang Froestl; Bernhard Bettler



Binding of antibodies in sera from Type 1 (insulin-dependent) diabetic patients to glutamate decarboxylase from rat tissues. Evidence for antigenic and non-antigenic forms of the enzyme  

Microsoft Academic Search

Summary  An islet protein of Mr 64000, identified as the -amino butyric acid (GABA)-synthesizing enzyme, glutamate decarboxylase, is a major target for antibodies in Type 1 (insulin-dependent) diabetes mellitus. This enzyme is also expressed in brain and in some other tissues and may exist in multiple forms. The aim of this study was to determine the ability of antibodies from diabetic

M. R. Christie; T. J. Brown; D. Cassidy



Neurochemical characterization of nervous elements innervating the body wall of earthworms ( Lumbricus , Eisenia ): immunohistochemical and pharmacological studies  

Microsoft Academic Search

The distribution and chemical neuroanatomy of nervous elements and certain pharmacological–physiological characteristics of the innervation of the body wall in earthworms are described. Solitary sensory bipolar cells can be found among the epithelial cells. These bipolar cells contain serotonin, tyrosine hydroxylase, histamine, gamma-amino-butyric acid (GABA), Eisenia tetradecapeptide, proctolin or rhodopsin in various combinations. In the body wall, the plexus submuscularis

Mária Csoknya; Boglárka Takács; Anna Koza; Viktória Dénes; Márta Wilhelm; László Hiripi; Jan Kaslin; Károly Elekes



Preclinical evaluation of the reinforcing and discriminative stimulus effects of agomelatine (S-20098), a melatonin agonist  

Microsoft Academic Search

Agomelatine (S-20098), an analog of melatonin, has shown promise as a chronobiotic in animal models of sleep phase disorders\\u000a and is being developed for clinical use. Previous research has shown that the pharmacological profile of melatonin-like drugs\\u000a overlaps that of ?-amino butyric acid (GABA) agonists. Given the potential of drugs within the latter class for recreational\\u000a abuse in humans, evaluation

Jenny L. Wiley; Mario E. Dance; Robert L. Balster



Gamma-Aminobutyric Acid, Mediator of Inhibition in the Nervous System.  

National Technical Information Service (NTIS)

Gamma-aminobutyric acid (GABA) satisfies the criteria for substances capable of being mediators in the nervous system. In the case of GABA, not only has it been found to occur only in nervous structures, but components of the GABA system (GABA, glutamate ...

I. A. Sytinskii



Structure, function, and plasticity of GABA transporters  

PubMed Central

GABA transporters belong to a large family of neurotransmitter:sodium symporters. They are widely expressed throughout the brain, with different levels of expression in different brain regions. GABA transporters are present in neurons and in astrocytes and their activity is crucial to regulate the extracellular concentration of GABA under basal conditions and during ongoing synaptic events. Numerous efforts have been devoted to determine the structural and functional properties of GABA transporters. There is also evidence that the expression of GABA transporters on the cell membrane and their lateral mobility can be modulated by different intracellular signaling cascades. The strength of individual synaptic contacts and the activity of entire neuronal networks may be finely tuned by altering the density, distribution and diffusion rate of GABA transporters within the cell membrane. These findings are intriguing because they suggest the existence of complex regulatory systems that control the plasticity of GABAergic transmission in the brain. Here we review the current knowledge on the structural and functional properties of GABA transporters and highlight the molecular mechanisms that alter the expression and mobility of GABA transporters at central synapses.

Scimemi, Annalisa



Cortical GABA Levels in Primary Insomnia  

PubMed Central

Study Objectives: GABA is increasingly recognized as an important neurotransmitter for the initiation and maintenance of sleep. We sought to measure cortical GABA content through proton magnetic resonance spectroscopy (MRS) in persons with and without primary insomnia, and relate brain GABA levels to polysomnographic sleep measures. Design: Two-group comparison study. Setting: Outpatient study at a university research clinic. Participants: Non-medicated persons with primary insomnia (N = 16) and no sleep complaints (N = 17). Interventions: Participants kept sleep diaries and a regular time-in-bed schedule for 9 days, culminating in 2 consecutive nights of ambulatory polysomnography and a single proton MRS session. The main outcome measure was occipital GABA/creatine ratios; secondary measures included sleep measurements and relationship between polysomnographically measured time awake after sleep onset and occipital GABA content. Measurements and Results: The primary insomnia group was distinguished from persons with no sleep complaints on self-reported and polysomnographically measured sleep. The two groups did not differ in age, sex, body mass index, habitual bed- and wake-times, napping, use of caffeine, or use of cigarettes. Mean occipital GABA level was 12% higher in persons with insomnia than in persons without sleep complaints (P < 0.05). In both groups, GABA levels correlated negatively with polysomnographically measured time awake after sleep onset (P < 0.05). Conclusions: Increased GABA levels in persons with insomnia may reflect an allostatic response to chronic hyperarousal. The preserved, negative relationship between GABA and time awake after sleep onset supports this notion, indicating that the possible allostatic response is adaptive. Citation: Morgan PT; Pace-Schott EF; Mason GF; Forselius E; Fasula M; Valentine GW; Sanacora G. Cortical GABA levels in primary insomnia. SLEEP 2012;35(6):807-814.

Morgan, Peter T.; Pace-Schott, Edward F.; Mason, Graeme F.; Forselius, Erica; Fasula, Madonna; Valentine, Gerald W.; Sanacora, Gerard



Dopaminergic neurons inhibit striatal output via non-canonical release of GABA  

PubMed Central

The substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) contain the two largest populations of dopamine (DA)-releasing neurons in the mammalian brain. These neurons extend elaborate projections in striatum, a large subcortical structure implicated in motor planning and reward-based learning. Phasic activation of dopaminergic neurons in response to salient or reward-predicting stimuli is thought to modulate striatal output via the release of DA to promote and reinforce motor action1–4. Here we show that activation of DA neurons in striatal slices rapidly inhibits action potential firing in both direct-and indirect-pathway striatal projection neurons (SPNs) through vesicular release of the inhibitory transmitter ?-aminobutyric acid (GABA). GABA is released directly from dopaminergic axons but in a manner that is independent of the vesicular GABA transporter VGAT. Instead GABA release requires activity of the vesicular monoamine transporter VMAT2, which is the vesicular transporter for DA. Furthermore, VMAT2 expression in GABAergic neurons lacking VGAT is sufficient to sustain GABA release. Thus, these findings expand the repertoire of synaptic mechanisms employed by DA neurons to influence basal ganglia circuits, reveal a novel substrate whose transport is dependent on VMAT2, and demonstrate that GABA can function as a bona fide co-transmitter in monoaminergic neurons.

Tritsch, Nicolas X.; Ding, Jun B.; Sabatini, Bernardo L.



Novel dose-dependent alterations in excitatory GABA during embryonic development associated with lead (Pb) neurotoxicity.  


Lead (Pb) is a heavy metal that is toxic to numerous physiological processes. Its use in industrial applications is widespread and results in an increased risk of human environmental exposure. The central nervous system (CNS) is most sensitive to Pb exposure during early development due to rapid cell proliferation and migration, axonal growth, and synaptogenesis. One of the key components of CNS development is the Gamma-aminobutyric acid (GABA)-ergic system. GABA is the primary inhibitory neurotransmitter in the adult brain. However, during development GABA acts as an excitatory neurotrophic factor which contributes to these cellular processes. Multiple studies report effects of Pb on GABA in the mature brain; however, little is known regarding the adverse effects of Pb exposure on the GABAergic system during embryonic development. To characterize the effects of Pb on the GABAergic system during development, zebrafish embryos were exposed to 10, 50, or 100ppb Pb or a control treatment. Tissue up-take, gross morphological alterations, gene expression, and neurotransmitter levels were analyzed. Analysis revealed that alterations in gene expression throughout the GABAergic system and GABA levels were dose and developmental time point specific. These data provide a framework for further analysis of the effects of Pb on the GABAergic system during the excitatory phase and as GABA transitions to an inhibitory neurotransmitter during development. PMID:24875535

Wirbisky, Sara E; Weber, Gregory J; Lee, Jang-Won; Cannon, Jason R; Freeman, Jennifer L



Downregulation of Parvalbumin at Cortical GABA Synapses Reduces Network Gamma Oscillatory Activity  

PubMed Central

Postmortem and functional imaging studies of patients with psychiatric disorders, including schizophrenia, are consistent with a dysfunction of interneurons leading to compromised inhibitory control of network activity. Parvalbumin (PV)-expressing, fast-spiking interneurons interacting with pyramidal neurons generate cortical gamma oscillations (30 – 80 Hz) that synchronize cortical activity during cognitive processing. In postmortem studies of schizophrenia patients, these interneurons show reduced PV and glutamic acid decarboxylase 67 (GAD67), an enzyme that synthesizes GABA, but the consequences of this downregulation are unclear. We developed a biophysically realistic and detailed computational model of a cortical circuit including asynchronous release from GABAergic interneurons to investigate how reductions in PV and GABA affect gamma oscillations induced by sensory stimuli. Networks with reduced GABA were disinhibited and had altered gamma oscillations in response to stimulation; PV-deficient GABA synapses had increased asynchronous release of GABA, which decreased the level of excitation and reduced gamma-band activity. Combined reductions of PV and GABA resulted in a diminished gamma-band oscillatory activity in response to stimuli, similar to that observed in schizophrenia patients. Our results suggest a mechanism by which reduced GAD67 and PV in fast-spiking interneurons may contribute to cortical dysfunction in schizophrenia and related psychiatric disorders.

Volman, Vladislav; Behrens, M. Margarita; Sejnowski, Terrence J.



Defects in GABA metabolism affect selective autophagy pathways and are alleviated by mTOR inhibition  

PubMed Central

In addition to key roles in embryonic neurogenesis and myelinogenesis, ?-aminobutyric acid (GABA) serves as the primary inhibitory mammalian neurotransmitter. In yeast, we have identified a new role for GABA that augments activity of the pivotal kinase, Tor1. GABA inhibits the selective autophagy pathways, mitophagy and pexophagy, through Sch9, the homolog of the mammalian kinase, S6K1, leading to oxidative stress, all of which can be mitigated by the Tor1 inhibitor, rapamycin. To confirm these processes in mammals, we examined the succinic semialdehyde dehydrogenase (SSADH)-deficient mouse model that accumulates supraphysiological GABA in the central nervous system and other tissues. Mutant mice displayed increased mitochondrial numbers in the brain and liver, expected with a defect in mitophagy, and morphologically abnormal mitochondria. Administration of rapamycin to these mice reduced mTOR activity, reduced the elevated mitochondrial numbers, and normalized aberrant antioxidant levels. These results confirm a novel role for GABA in cell signaling and highlight potential pathomechanisms and treatments in various human pathologies, including SSADH deficiency, as well as other diseases characterized by elevated levels of GABA.

Lakhani, Ronak; Vogel, Kara R; Till, Andreas; Liu, Jingjing; Burnett, Sarah F; Gibson, K Michael; Subramani, Suresh



Effects of anticonvulsant drug gabapentin on the enzymes in metabolic pathways of glutamate and GABA  

Microsoft Academic Search

Gabapentin is a novel anticonvulsant drug. The anticonvulsant mechanism of gabapentin is not known. Based on the amino acid structure of gabapentin we explored its possible effects on glutamate and ?-aminobutyric acid (GABA) metabolism in brain as they may relate to its anticonvulsant mechanisms of action. Gabapentin was tested for its effects on seven enzymes in the metabolic pathways of

Arie Goldlust; Ti-Zhi Su; Devin F. Welty; Charles P. Taylor; Dale L. Oxender



Properties of GABA(A) receptors in cultured rat oligodendrocyte progenitor cells.  


We have studied the properties of GABA responses in oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells derived from primary cultures of the neonatal rat brain. In whole cell voltage clamp recordings, rapid application of 1-10 mM GABA elicited current responses in > 85% of the cells examined. The dose-response relationship pooled from nine progenitor cells was best fit by a logistic function of EC50=113 microM and Hill coefficient=0.9. In contrast to the rate of current deactivation, the rate of current activation exhibited marked concentration-dependence. Pharmacologically, GABA, muscimol and ZAPA ((Z)-3[(aminiiminomethyl)thio]prop-2-enoic acid sulphate) produced responses with ligand-specific kinetics, whereas glycine and the GABA(C) receptor agonist CACA were without effect; bicuculline methochloride acted as a competitive antagonist. Neither the amplitude nor the kinetics of currents produced by 100 microM GABA were affected by the benzodiazepine flunitrazepam (1 microM). Similarly the benzodiazepine receptor inverse agonist DMCM (1 microM) was also without effect. GABA-activated currents reversed polarity within 2 mV of the calculated Cl- equilibrium potential. With brief agonist pulses deactivation was monoexponential, however, unlike neurones the rate of deactivation was voltage-independent. Desensitisation of responses to 10 mM GABA was bi-exponential and accelerated at depolarised membrane potentials. Increasing the amount of GABA(A) receptor desensitisation (by increasing the duration of the agonist exposure) consistently produced a slowing of deactivation. PMID:9776382

Williamson, A V; Mellor, J R; Grant, A L; Randall, A D



Selective depression of GABA-mediated IPSPs by somatostatin in area CA1 of rabbit hippocampal slices.  


In area CA1 of hippocampus, a subpopulation of gamma-aminobutyric acid (GABA)-containing interneurons that make synaptic contacts on pyramidal cells also contains the neuropeptide, somatostatin. The effects of GABA and somatostatin on hippocampal pyramidal cells have been investigated separately, but it is not known whether an interaction occurs between these co-localized substances. We demonstrate that somatostatin has a potent inhibitory effect on GABA-mediated synaptic potentials which hyperpolarize pyramidal cells. This effect may be relevant to the well-documented epileptogenicity of the hippocampus, as well as the phenomenon of long-term potentiation, which is a well-studied example of synaptic plasticity. PMID:2569913

Scharfman, H E; Schwartzkroin, P A



{gamma}-aminobutyric acid{sub A} (GABA{sub A}) receptor regulates ERK1/2 phosphorylation in rat hippocampus in high doses of Methyl Tert-Butyl Ether (MTBE)-induced impairment of spatial memory  

SciTech Connect

Experimental and occupational exposure to Methyl Tert-Butyl Ether (MTBE) has been reported to induce neurotoxicological and neurobehavioral effects, such as headache, nausea, dizziness, and disorientation, etc. However, the molecular mechanisms involved in MTBE-induced neurotoxicity are still not well understood. In the present study, we investigated the effects of MTBE on spatial memory and the expression and function of GABA{sub A} receptor in the hippocampus. Our results demonstrated that intraventricular injection of MTBE impaired the performance of the rats in a Morris water maze task, and significantly increased the expression of GABA{sub A} receptor {alpha}1 subunit in the hippocampus. The phosphorylation of ERK1/2 decreased after the MTBE injection. Furthermore, the decreased ability of learning and the reduction of phosphorylated ERK1/2 level of the MTBE-treated rats was partly reversed by bicuculline injected 30 min before the training. These results suggested that MTBE exposure could result in impaired spatial memory. GABA{sub A} receptor may play an important role in the MTBE-induced impairment of learning and memory by regulating the phosphorylation of ERK in the hippocampus.

Zheng Gang; Zhang Wenbin [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China); Zhang Yun [465 Hospital, Jilin Medical College, Jilin 132001 (China); Chen Yaoming; Liu Mingchao; Yao Ting; Yang Yanxia; Zhao Fang [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China); Li Jingxia; Huang Chuanshu [Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987 (United States); Luo Wenjing [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China)], E-mail:; Chen Jingyuan [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China)], E-mail:



BL1020, a novel antipsychotic candidate with GABA-enhancing effects: D 2 receptor occupancy study in humans  

Microsoft Academic Search

BL-1020 is a potentially novel antipsychotic, which comprises the typical antipsychotic perphenazine linked by an ester bound to ?-aminobutyric acid (GABA), intending a simultaneous dopamine-2 (D2) receptor blockade and GABA facilitation in the brain. This positron emission tomography (PET) study, using [11C]raclopride, assessed the extent and duration of D2 receptor occupancy (D2 RO) and safety for single doses of BL-1020

Lieuwe Appel; Yona Geffen; Kerstin Heurling; Catarina Eriksson; Gunnar Antoni; Shitij Kapur



Neurotensin modulation of acetylcholine, GABA, and aspartate release from rat prefrontal cortex studied in vivo with microdialysis  

Microsoft Academic Search

The effects of the peptide transmitter neurotensin (NT) on the release of acetylcholine (ACh), ?-aminobutyric acid (GABA), glutamate (Glu), aspartate (Asp), and taurine from the prefrontal cortex (PFC) of freely moving rats were studied by transversal microdialysis. Neurotensin (0.2 and 1?M) administered locally in the PFC produced a concentration-dependent increase in the extracellular levels of ACh, GABA, and Asp, but

Polina Petkova-Kirova; Angelina Rakovska; Laura Della Corte; Galina Zaekova; Radomir Radomirov; Aliz Mayer



Profiling gamma-aminobutyric acid (GABA(A)) receptor subunit mRNA expression in postnatal gonadotropin-releasing hormone (GnRH) neurons of the male mouse with single cell RT-PCR.  


The present investigation has examined which subunits of the GABA(A) receptor are expressed by gonadotropin-releasing hormone (GnRH) neurons in the juvenile and adult male mouse. Cells of defined morphology, located in the medial septum (MS) and rostral preoptic area (POA), were patch-clamped in the acute brain slice preparation and their cell contents extracted. A reverse transcriptase polymerase chain reaction (RT-PCR) procedure using nested primers was used to establish individual GnRH mRNA-expressing cells which were then evaluated for eleven GABA(A) receptor (alpha1-5, beta1-3, gamma1-3) subunit transcripts. Single and multiple GABA(A) receptor subunit mRNAs were detected in approximately 70% of all GnRH neurons. A range of different subunit mRNAs (alpha1, alpha2, alpha5, beta1, beta2, beta3, gamma2) were found in juvenile GnRH neurons, with the alpha1gamma2 and alpha5gamma2 combinations encountered most frequently within individual cells. The expression profile in adult GnRH neurons was more extensive than that detected in juveniles with alpha1, alpha2, alpha3, alpha5, beta1, beta2, beta3, gamma1 and gamma2 subunits all being detected. The major difference in subunit profile between GnRH neurons located in the MS and POA involved the beta subunits. The principal postnatal developmental change was one of increasing overall subunit heterogeneity in maturing POA GnRH neurons. The profile of GABA(A) receptor subunit mRNAs detected in male GnRH neurons was quite different to that reported by us for female GnRH neurons in the mouse using the same RT-PCR approach. Together, these findings indicate that postnatal GnRH neurons are likely to express a range of GABA(A) receptor subunit mRNAs in a sexually dimorphic and developmentally-regulated manner. PMID:11694762

Pape, J R; Skynner, M J; Sim, J A; Herbison, A E



Time-course of SKF-81297-induced increase in glutamic acid decarboxylase 65 and 67 mRNA levels in striatonigral neurons and decrease in GABA(A) receptor alpha1 subunit mRNA levels in the substantia nigra, pars reticulata, in adult rats with a unilateral 6-hydroxydopamine lesion.  


Striatal projection neurons use GABA as their neurotransmitter and express the rate-limiting synthesizing enzyme glutamic acid decarboxylase (GAD) and the vesicular GABA transporter vGAT. The chronic systemic administration of an agonist of dopamine D1/D5-preferring receptors is known to alter GAD mRNA levels in striatonigral neurons in intact and dopamine-depleted rats. In the present study, the effects of a single or subchronic systemic administration of the dopamine D1/D5-preferring receptor agonist SKF-81297 on GAD65, GAD67, PPD and vGAT mRNA levels in the striatum and GABA(A) receptor alpha1 subunit mRNA levels in the substantia nigra, pars reticulata, were measured in rats with a unilateral 6-hydroxydopamine (6-OHDA) lesion. After a single injection of SKF-81297, striatal GAD65 mRNA levels were significantly increased at 3 but not 72 h. In contrast, striatal GAD67 mRNA levels were increased and nigral alpha1 mRNA levels were decreased at 72 but not 3 h. Single cell analysis on double-labeled sections indicated that increased GAD or vGAT mRNA levels after acute SKF-81297 occurred in striatonigral neurons identified by their lack of preproenkephalin expression. Subchronic SKF-81297 induced significant increases in striatal GAD67, GAD65, preprodynorphin and vGAT mRNA levels and decreases in nigral alpha1 mRNA levels. In the striatum contralateral to the 6-OHDA lesion, subchronic but not acute SKF-81297 induced a significant increase in GAD65 mRNA levels. The other mRNA levels were not significantly altered. Finally, striatal GAD67 mRNA levels were negatively correlated with nigral alpha1 mRNA levels in the dopamine-depleted but not dopamine-intact side. The results suggest that different signaling pathways are involved in the modulation by dopamine D1/D5 receptors of GAD65 and GAD67 mRNA levels in striatonigral neurons. They also suggest that the down-regulation of nigral GABA(A) receptors is linked to the increase in striatal GAD67 mRNA levels in the dopamine-depleted striatum. PMID:18495353

Yamamoto, N; Soghomonian, J-J



VTA GABA neurons modulate specific learning behaviors through the control of dopamine and cholinergic systems.  


The mesolimbic reward system is primarily comprised of the ventral tegmental area (VTA) and the nucleus accumbens (NAc) as well as their afferent and efferent connections. This circuitry is essential for learning about stimuli associated with motivationally-relevant outcomes. Moreover, addictive drugs affect and remodel this system, which may underlie their addictive properties. In addition to dopamine (DA) neurons, the VTA also contains approximately 30% ?-aminobutyric acid (GABA) neurons. The task of signaling both rewarding and aversive events from the VTA to the NAc has mostly been ascribed to DA neurons and the role of GABA neurons has been largely neglected until recently. GABA neurons provide local inhibition of DA neurons and also long-range inhibition of projection regions, including the NAc. Here we review studies using a combination of in vivo and ex vivo electrophysiology, pharmacogenetic and optogenetic manipulations that have characterized the functional neuroanatomy of inhibitory circuits in the mesolimbic system, and describe how GABA neurons of the VTA regulate reward and aversion-related learning. We also discuss pharmacogenetic manipulation of this system with benzodiazepines (BDZs), a class of addictive drugs, which act directly on GABAA receptors located on GABA neurons of the VTA. The results gathered with each of these approaches suggest that VTA GABA neurons bi-directionally modulate activity of local DA neurons, underlying reward or aversion at the behavioral level. Conversely, long-range GABA projections from the VTA to the NAc selectively target cholinergic interneurons (CINs) to pause their firing and temporarily reduce cholinergic tone in the NAc, which modulates associative learning. Further characterization of inhibitory circuit function within and beyond the VTA is needed in order to fully understand the function of the mesolimbic system under normal and pathological conditions. PMID:24478655

Creed, Meaghan C; Ntamati, Niels R; Tan, Kelly R



GABA(A) receptor beta 2 Tyr97 and Leu99 line the GABA-binding site. Insights into mechanisms of agonist and antagonist actions.  


The identification of residues that line neurotransmitter-binding sites and catalyze allosteric transitions that result in channel gating is crucial for understanding ligand-gated ion channel function. In this study, we used the substituted cysteine accessibility method and two-electrode voltage clamp to identify novel gamma-aminobutyric acid (GABA)-binding site residues and to elucidate the secondary structure of the Trp(92)-Asp(101) region of the beta(2) subunit. Each residue was mutated individually to cysteine and expressed with wild-type alpha(1) subunits in Xenopus oocytes. GABA-gated currents (I(GABA)) were measured before and after exposure to the sulfhydryl reagent, N-biotinylaminoethyl methanethiosulfonate (MTS). V93C, D95C, Y97C, and L99C are accessible to derivatization. This pattern of accessibility is consistent with beta(2)Val(93)-Leu(99) adopting a beta-strand conformation. Both GABA and SR95531 protect Y97C and L99C from modification, indicating that these two residues line the GABA-binding site. In D95C-containing receptors, application of MTS in the presence of SR95531 causes a greater effect on I(GABA) than MTS alone, suggesting that binding of a competitive antagonist can cause movements in the binding site. In addition, we present evidence that beta(2)L99C homomers form spontaneously open channels. Thus, mutation of a binding site residue can alter channel gating, which implies that Leu(99) may be important for coupling agonist binding to channel gating. PMID:11711541

Boileau, Andrew J; Newell, J Glen; Czajkowski, Cynthia



Effects of Yoga Versus Walking on Mood, Anxiety, and Brain GABA Levels: A Randomized Controlled MRS Study  

PubMed Central

Abstract Objectives Yoga and exercise have beneficial effects on mood and anxiety. ?-Aminobutyric acid (GABA)-ergic activity is reduced in mood and anxiety disorders. The practice of yoga postures is associated with increased brain GABA levels. This study addresses the question of whether changes in mood, anxiety, and GABA levels are specific to yoga or related to physical activity. Methods Healthy subjects with no significant medical/psychiatric disorders were randomized to yoga or a metabolically matched walking intervention for 60 minutes 3 times a week for 12 weeks. Mood and anxiety scales were taken at weeks 0, 4, 8, 12, and before each magnetic resonance spectroscopy scan. Scan 1 was at baseline. Scan 2, obtained after the 12-week intervention, was followed by a 60-minute yoga or walking intervention, which was immediately followed by Scan 3. Results The yoga subjects (n?=?19) reported greater improvement in mood and greater decreases in anxiety than the walking group (n?=?15). There were positive correlations between improved mood and decreased anxiety and thalamic GABA levels. The yoga group had positive correlations between changes in mood scales and changes in GABA levels. Conclusions The 12-week yoga intervention was associated with greater improvements in mood and anxiety than a metabolically matched walking exercise. This is the first study to demonstrate that increased thalamic GABA levels are associated with improved mood and decreased anxiety. It is also the first time that a behavioral intervention (i.e., yoga postures) has been associated with a positive correlation between acute increases in thalamic GABA levels and improvements in mood and anxiety scales. Given that pharmacologic agents that increase the activity of the GABA system are prescribed to improve mood and decrease anxiety, the reported correlations are in the expected direction. The possible role of GABA in mediating the beneficial effects of yoga on mood and anxiety warrants further study.

Whitfield, Theodore H.; Owen, Liz; Rein, Tasha; Karri, Surya K.; Yakhkind, Aleksandra; Perlmutter, Ruth; Prescot, Andrew; Renshaw, Perry F.; Ciraulo, Domenic A.; Jensen, J. Eric



Phenotypic characterization of orofacial movement topography in mutants with disruption of amino acid mechanisms: glutamate N2A/B/D [GluR?1/2/4] subtypes and the GABA synthesizing enzyme GAD65.  


To investigate the role of glutamate receptor subtypes and GABA in orofacial function, six individual topographies of orofacial movement, both spontaneous and induced by the dopamine D1-like receptor agonist [R/S]-3-methyl-6-chloro-7,8-dihydroxy-1-[3-methyl-phenyl]-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF 83959), were quantified in mutant mice with deletion of (a) GluN2A, B or D receptors, and (b) the GABA synthesizing enzyme, 65-kD isoform of glutamate decarboxylase (GAD65). In GluN2A mutants, habituation of head movements was disrupted and vibrissae movements were reduced, with an overall increase in locomotion; responsivity to SKF 83959 was unaltered. In GluN2B mutants, vertical and horizontal jaw movements and incisor chattering were increased, with an overall decrease in locomotion; under challenge with SKF 83959, head and vibrissae movements were reduced. In GluN2D mutants, horizontal jaw movements, incisor chattering and vibrissae movements were increased, with reduced tongue protrusions and no overall change in locomotion; under challenge with SKF 83959, horizontal jaw movements were increased. In GAD65 mutants, vertical jaw movements were increased, with disruption to habituation of locomotion; under challenge with SKF 83959, vertical and horizontal jaw movements and incisor chattering were decreased. Effects on orofacial movements differed from their effects on regulation of overall locomotor behavior. These findings (a) indicate novel, differential roles for GluN2A, B and D receptors and for GAD65-mediated GABA in the regulation of individual topographies of orofacial movement and (b) reveal how these roles differ from and/or interact with the established role of D1-like receptors in pattern generators and effectors for such movements. PMID:23892010

Tomiyama, K; Kato, R; Hara, Y; Kobayashi, M; Mishina, M; Yanagawa, Y; Kinsella, A; Koshikawa, N; Waddington, J L



Differential expression of GABA A receptor ? subunit in cultured rat alveolar epithelial cells  

Microsoft Academic Search

Although type A ?-aminobutyric acid (GABA) receptors (ligand-gated Cl? channels) have been extensively studied in the central nervous system, no information is available on this receptor in lung cells. We have examined the expression of GABAA receptor ?-subunit (GABRP) during the trans-differentiation between rat alveolar epithelial type II cells and type I cells. Rat alveolar type II cells, when cultured

Nili Jin; Telugu Narasaraju; Narasaiah Kolliputi; Jiwang Chen; Lin Liu



Reversal or reduction of glutamate and GABA transport in CNS pathology and therapy  

Microsoft Academic Search

A dysfunction of amino acid neurotransmitter transporters occurs in a number of central nervous system disorders, including stroke, epilepsy, cerebral palsy and amyotrophic lateral sclerosis. This dysfunction can comprise a reversal of transport direction, leading to the release of neurotransmitter into the extracellular space, or an alteration in transporter expression level. This review analyses the role of glutamate and GABA

Nicola J. Allen; Ragnhildur Káradóttir; David Attwell



Chronic Administration of Antipanic Drugs Alters Rat Brainstem GABA A Receptor Subunit mRNA Levels  

Microsoft Academic Search

Mental illnesses, such as panic disorder and depression, display comorbidity as well as common therapeutic treatments. These features point toward a common etiology and\\/or therapeutic pathway. There is evidence to suggest that some antipanic agents may mediate their effects by altering ?-aminobutyric acid (GABA) levels or by modulating the activity of the GABAA receptor. Chronic stimulation of GABAA receptors by




Sodium Channels, GABA, Receptors, and Glutamate Receptors Develop Sequentially on Embryonic Rat Spinal Cord Cells  

Microsoft Academic Search

ability- in dissociated embryonic rat spinal cord cells. We studied the expression of responses to veratridine, a sodium channel activator; muscimol, a GABA, receptor agonist; and kainic acid, an agonist at a class of glutamate receptors. Responses were consistently detectable in a percentage of cells dissociated from the earliest age examined, embryonic day 13, and increased progressively in later ages.

M. K. Walton; A. E. Schaffner; J. L. Barker



Glutamate and GABA in the medial amygdala induce selective central sympathetic/parasympathetic cardiovascular responses.  


Glutamate and ?-aminobutyric acid (GABA) participate in central cardiovascular control, and are found in the rat posterodorsal medial amygdala (MePD), an area of the forebrain that modulates emotional/social behaviors. Here we tested whether these neurotransmitters in the MePD could change the basal activity, chemoreflex, and baroreflex cardiovascular responses in awake rats. Power spectral analysis and symbolic analysis were used to evaluate these responses. Microinjections of saline, glutamate (2 µg), or GABA (61 ng or 100 µg; n = 5-7 rats per group) did not affect basal parameters or chemoreflex responses. However, baroreflex responses showed marked changes. Glutamate increased power spectral and symbolic sympathetic indexes related to both cardiac and vascular modulations (P < 0.05). In turn, the displacement of the baroreflex half-maximal heart rate (HR) response was associated with a GABA (61 ng) mediated decrease in the upper plateau (P < 0.05). Administration of GABA (61 ng, but not 100 µg) also increased HR variability (P < 0.05), in association with parasympathetic activation. These data add novel evidence that the MePD can promote selective responses in the central regulation of the cardiovascular system, i.e., glutamate in the MePD evoked activation of a central sympathetic reflex adjustment, whereas GABA activated a central parasympathetic one. PMID:22512449

Neckel, Helinton; Quagliotto, Edson; Casali, Karina R; Montano, Nicola; Dal Lago, Pedro; Rasia-Filho, Alberto A



SDF and GABA interact to regulate axophilic migration of GnRH neurons  

PubMed Central

Summary Stromal derived growth factor (SDF-1) and gamma-aminobutyric acid (GABA) are two extracellular cues that regulate the rate of neuronal migration during development and may act synergistically. The molecular mechanisms of this interaction are still unclear. Gonadotropin releasing hormone-1 (GnRH) neurons are essential for vertebrate reproduction. During development, these neurons emerge from the nasal placode and migrate through the cribriform plate into the brain. Both SDF-1 and GABA have been shown to regulate the rate of GnRH neuronal migration by accelerating and slowing migration, respectively. As such, this system was used to explore the mechanism by which these molecules act to produce coordinated cell movement during development. In the present study, GABA and SDF-1 are shown to exert opposite effects on the speed of cell movement by activating depolarizing or hyperpolarizing signaling pathways, GABA via changes in chloride and SDF-1 via changes in potassium. GABA and SDF-1 were also found to act synergistically to promote linear rather than random movement. The simultaneous activation of these signaling pathways, therefore, results in tight control of cellular speed and improved directionality along the migratory pathway of GnRH neurons.

Casoni, Filippo; Ian Hutchins, B.; Donohue, Duncan; Fornaro, Michele; Condie, Brian G.; Wray, Susan




PubMed Central

The neural substrate of brain stimulation reward (BSR) has eluded identification since its discovery more than a half-century ago. Notwithstanding the difficulties in identifying the neuronal integrator of BSR, the mesocorticolimbic dopamine (DA) system originating in the ventral tegmental area (VTA) of the midbrain has been implicated. We have previously demonstrated that the firing rate of a subpopulation of ?–aminobutyric acid (GABA) neurons in the VTA increases in anticipation of BSR. We show here that GABA neurons in the VTA, midbrain, hypothalamus and thalamus of rats express connexin-36 (Cx36) gap junctions (GJs) and couple electrically upon DA application or by stimulation of the internal capsule (IC), which also supports self-stimulation. The threshold for responding for IC self-stimulation was the threshold for electrical coupling between GABA neurons, the degree of responding for IC self-stimulation was proportional to the magnitude of electrical coupling between GABA neurons, and GJ blockers increased the threshold for IC self-stimulation without affecting performance. Thus, a network of electrically-coupled GABA neurons in the ventral brain may form the elusive neural integrator of BSR.

Lassen, Matthew B.; Brown, J. Elliott; Stobbs, Sarah H.; Gunderson, Seth H.; Maes, Levi; Valenzuela, C Fernando; Ray, Andrew P.; Henriksen, Steven J.; Steffensen, Scott C.



GABA/benzodiazepine receptor complex in long-sleep and short-sleep mice  

SciTech Connect

LS mice are more sensitive to benzodiazepine-induced anesthesia; however, the two lines do not differ in their hypothermic response to flurazepam. SS mice are more resistant to 3-mercaptopropionic acid-induced seizures and more sensitive to the anticonvulsant effects of benzodiazepines. The various correlates of GABA and benzodiazepine actions probably are the results of different mechanisms of action and/or differential regional control. Bicuculline competition for /sup 3/H-GABA binding sites is greater in SS cerebellar tissue and /sup 3/H-flunitrazepam binding is greater in the mid-brain region of LS mice. GABA enhancement of /sup 3/H-flunitrazepma binding is greater in SS mice. Ethanol also enhances /sup 3/H-flunitrazepam binding and increases the levels of /sup 3/H-flunitrazepam binding above those observed for GABA. Using correlational techniques on data from LS and SS mice and several inbred mouse strains, it was demonstrated that a positive relationship exists between the degree of receptor coupling within the GABA receptor complex and the degree of resistance to seizures.

Marley, R.J.



The vigilance promoting drug modafinil decreases GABA release in the medial preoptic area and in the posterior hypothalamus of the awake rat: possible involvement of the serotonergic 5HT 3 receptor  

Microsoft Academic Search

The effect of modafinil on endogenous ?-aminobutyric acid (GABA) release in the medial preoptic area (MPA) and posterior hypothalamus (PH) and the role of local 5-HT3 receptors in this effect was investigated in the awake rat using in vivo microdialysis. Modafinil (30–100 mg\\/kg i.p.) dose-dependently decreased GABA release from the MPA, while only the 100 mg\\/kg dose markedly reduced GABA

Luca Ferraro; Sergio Tanganelli; William Thomas O'Connor; Tiziana Antonelli; Francis Rambert; Kjell Fuxe



Genetic differences in the ethanol sensitivity of GABA sub A receptors expressed in Xenopus oocytes  

SciTech Connect

Animal lines selected for differences in drug sensitivity can be used to help determine the molecular basis of drug action. Long-sleep (LS) and short-sleep (SS) mice differ markedly in their genetic sensitivity to ethanol. To investigate the molecular basis for this difference, mRNA from brains of LS and SS mice was expressed in Xenopus oocytes and the ethanol sensitivity of gamma-aminobutyric acid A (GABA{sub A})- and N-methyl D-aspartate (NMDA) - activated ion channels was tested. Ethanol facilitated GABA responses in oocytes injected with mRNA from LS mice but antagonized responses in oocytes injected with mRNA from SS animals. Ethanol inhibited NMDA responses equally in the two lines. Thus, genes coding for the GABA{sub A} receptor or associated proteins may be critical determinants of individual differences in ethanol sensitivity.

Wafford, K.A.; Burnett, D.M.; Dunwiddie, T.V.; Harris, R.A. (Univ. of Colorado Health Sciences Center, Denver (USA))



Acute increases in synaptic GABA detectable in the living human brain: A [(11)C]Ro15-4513 PET study.  


The inhibitory ?-aminobutyric acid (GABA) neurotransmitter system is associated with the regulation of normal cognitive functions and dysregulation has been reported in a number of neuropsychiatric disorders including anxiety disorders, schizophrenia and addictions. Investigating the role of GABA in both health and disease has been constrained by difficulties in measuring acute changes in synaptic GABA using neurochemical imaging. The aim of this study was to investigate whether acute increases in synaptic GABA are detectable in the living human brain using the inverse agonist GABA-benzodiazepine receptor (GABA-BZR) positron emission tomography (PET) tracer, [(11)C]Ro15-4513. We examined the effect of 15mg oral tiagabine, which increases synaptic GABA by inhibiting the GAT1 GABA uptake transporter, on [(11)C]Ro15-4513 binding in 12 male participants using a paired, double blind, placebo-controlled protocol. Spectral analysis was used to examine synaptic ?1 and extrasynaptic ?5 GABA-BZR subtype availability in brain regions with high levels of [(11)C]Ro15-4513 binding. We also examined the test-retest reliability of ?1 and a5-specific [(11)C]Ro15-4513 binding in a separate cohort of 4 participants using the same spectral analysis protocol. Tiagabine administration produced significant reductions in hippocampal, parahippocampal, amygdala and anterior cingulate synaptic ?1 [(11)C]Ro15-4513 binding, and a trend significance reduction in the nucleus accumbens. These reductions were greater than test-retest reliability, indicating that they are not the result of chance observations. Our results suggest that acute increases in endogenous synaptic GABA are detectable in the living human brain using [(11)C]Ro15-4513 PET. These findings have potentially major implications for the investigation of GABA function in brain disorders and in the development of new treatments targeting this neurotransmitter system. PMID:24844747

Stokes, Paul R A; Myers, Jim F; Kalk, Nicola J; Watson, Ben J; Erritzoe, David; Wilson, Sue J; Cunningham, Vincent J; Barros, Daniela Riano; Hammers, Alexander; Turkheimer, Federico E; Nutt, David J; Lingford-Hughes, Anne R



Effects of benzodiazepines and non-benzodiazepine compounds on the GABA-induced response in frog isolated sensory neurones.  


1. The effects of benzodiazepines and non-benzodiazepine compounds on the gamma-aminobutyric acid (GABA)-induced chloride current (ICl) were studied in frog isolated sensory neurones by use of a concentration-jump (termed 'concentration-clamp') technique, under single-electrode voltage-clamp conditions. The drugs used were classified into four categories as follows: full benzodiazepine receptor agonists (diazepam, clonazepam, nitrazepam, midazolam, clotiazepam and etizolam), partial agonists (CL 218,872, Ro 16-6028, Ro 17-1812 and Ro 23-0364), inverse agonists (Ro 15-3505, FG 7142 and beta-CCE) and a benzodiazepine receptor antagonist, Ro 15-1788 (flumazenil). 2. All full agonists at concentrations of 3 x 10(-6) M or less increased dose-dependently the peak amplitude of ICl elicited by 3 x 10(-6) M GABA to twice to three times larger than the control. However, no further augmentation of the GABA response was observed at concentrations of 1 x 10(-5) M or higher. Partial agonists also showed a dose-dependent augmentation of the GABA response at concentrations ranging from 3 x 10(-8) M to 3 x 10(-5) M, but their efficacies of augmentation of the GABA response were only about half or less of those of full agonists. Of the inverse agonists, beta-CCE had a unique dose-dependent effect on the GABA response. Beta-CCE reduced dose-dependently the GABA response at concentrations of less than 3 x 10(-6) M, but augmented it at concentrations of 3 x 10(-5) M and 6 x 10(-5) M. The inverse agonists reduced dose-dependently the GABA response. The benzodiazepine antagonist, flumazenil, slightly augmented the GABA response at concentrations between 3 x 10 7M and 3 x 10 5 M. 3. These results show clear differences in the effects on the GABA response between these four categories of compounds known to affect the benzodiazepine recognition site of the GABA/ benzodiazepine receptor-chloride channel complex. Our experimental system of frog isolated sensory neurones and a 'concentration-clamp' technique appears to be useful for evaluating efficacy of compounds on responses mediated by the GABA/benzodiazepine receptor-chloride channel complex. PMID:2574062

Yakushiji, T; Fukuda, T; Oyama, Y; Akaike, N



5-HT potentiation of the GABA(A) response in the rat sacral dorsal commissural neurones.  


1. The modulatory effect of 5-hydroxytryptamine (5-HT) on the gamma-aminobutyric acid(A) (GABA(A)) response was investigated in the neurones freshly dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under the voltage-clamp conditions. 2. 5-HT potentiated GABA-induced Cl- current (IGABA) without affecting the reversal potential of IGABA and the apparent affinity of GABA to its receptor. 3. Alpha-Methyl-5-HT mimicked the potentiation effect of 5-HT on IGABA while ketanserine blocked it. 1-Oleoyl-2-acetyl-glycerol (OAG) potentiated IGABA, and the effect of 5-HT on IGABA was occluded by OAG pretreatment. In the presence of chelerythrine, 5-HT failed to potentiate IGABA, suggesting that protein kinase C (PKC) is involved in the pathway through which the activation of the 5-HT2 receptor potentiates the IGABA. 4. The facilitatory effect of 5-HT on IGABA remained in the presence of BAPTA-AM. LiCl also had no effect on 5-HT-induced potentiation of IGABA. 5. H-89, genistein, okadaic acid and pervanadate all had no effects on 5-HT potentiation of IGABA. Pertussis toxin treatment for 6-8 h did not block the facilitatory effect of 5-HT on IGABA. 6. The present results show that GABA(A) receptor in the rat SDCN could be modulated in situ by 5-HT, one of the major transmitters involved in the supraspinal control of nociception, and that the phosphorylation of GABA(A) receptor by PKC may be sufficient to support such modulation. The results also strongly support the hypothesis that the cotransmission by 5-HT and GABA has an important role in the spinal cord. PMID:9690871

Xu, T L; Pang, Z P; Li, J S; Akaike, N



Synthesis of biobased N-methylpyrrolidone by one-pot cyclization and methylation of c-aminobutyric acid  

Microsoft Academic Search

N-Methylpyrrolidone (NMP) is an industrial solvent that is currently based on fossil resources. In order to prepare it in a biobased way, the possibility to synthesize NMP from -aminobutyric acid (GABA) was investigated, since GABA can be obtained from glutamic acid, an amino acid that is present in many plant proteins. Cyclization of GABA to 2-pyrrolidone and subsequent methylation of

Tijs M. Lammens; Maurice C. R. Franssen; Elinor L. Scott; Johan P. M. Sanders



Inhibition of GABA synthesis in the prefrontal cortex increases locomotor activity but does not affect attention in the 5-choice serial reaction time task  

PubMed Central

Attention deficits are a core cognitive symptom of schizophrenia; the neuropathology underlying these deficits is not known. Attention is regulated, at least in part, by the prefrontal cortex (PFC), a brain area in which pathology of ?-aminobutyric acid (GABA) neurons has been consistently observed in post-mortem analysis of the brains of people with schizophrenia. Specifically, expression of the 67-kD isoform of the GABA synthesis enzyme glutamic acid decarboxylase (GAD67) is reduced in parvalbumin-containing fast-spiking GABA interneurons. Thus it is hypothesized that reduced cortical GABA synthesis and release may contribute to the attention deficits in schizophrenia. Here the effect of reducing cortical GABA synthesis with L-allylglycine (LAG) on attention was tested using three different versions of the 5-choice serial reaction time task (5CSRTT). Because 5CSRTT performance can be affected by locomotor activity, we also measured this behavior in an open field. Finally, the expression of Fos protein was used as an indirect measure of reduced GABA synthesis. Intra-cortical LAG (10 ?g/0.5 ?l/side) infusions increased Fos expression and resulted in hyperactivity in the open field. Intra-cortical LAG infusions did not affect attention in any version of the 5CSRTT. These results suggest that a general decrease in GABA synthesis is not sufficient to cause attention deficits. It remains to be tested whether a selective decrease in GABA synthesis in parvalbumin-containing GABA neurons could cause attention deficits. Decreased cortical GABA synthesis did increase locomotor activity; this may reflect the positive symptoms of schizophrenia.

Asinof, Samuel K.; Paine, Tracie A.



Vibrational Spectra of ?-Aminobutyric Acid  

NASA Astrophysics Data System (ADS)

The NIR-FT Raman, FT-IR spectral analysis of ?-Aminobutyric acid (GABA) a simple amino acid is carried out by density functional computations. The vibrational spectra confirm the existence of NH3+ in GABA. Hydroxyl groups H-bonded to the different extents are analysed, supported by computed results.

Suresh, D. M.; Sajan, D.; Laladas, K. P.; Joe, I. Hubert; Jayakumar, V. S.



Responses to GABA recorded from identified rat visual cortical neurons.  


Responses to GABA were recorded from 87 neurons of rat visual cortical slices. Pyramidal and nonpyramidal cells were identified by intracellular dye injection, and their responses were compared. All identified pyramidal and nonpyramidal cells, as well as unstained cells, responded to GABA ejected from a pipette that was positioned within 300 micron of the soma. Their responses were similar, regardless of their morphology. In addition, GABA responses of visual cortical neurons could not be distinguished from those of other areas of the neocortex, or pyramidal cells in area CA1 of hippocampus. Depending on the site of application, there appeared to be two types of GABA responses that were present in all cells. The first was generated by application of GABA to the soma (GABAs response; mean reversal potential = -71.7 mV). The second occurred when GABA was applied on dendrites (GABAD response; mean reversal potential = -49.3 mV). When GABA was ejected on proximal dendritic regions, both responses could be observed in combination. Both GABAs and GABAD responses were accompanied by extremely large increases in conductance. In some cells, a third type of GABA response was elicited following somatic or dendritic GABA application. This response was a relatively small-amplitude, long-lasting hyperpolarization which followed a GABAS and GABAD response (late hyperpolarization, mean reversal potential = -79.8 mV). PMID:3437972

Scharfman, H E; Sarvey, J M



GABA-ergic neurons in the leach central nervous system  

SciTech Connect

GABA is a candidate for an inhibitory neurotransmitter in the leech central nervous system because of the well-documented inhibitory action of GABA in other invertebrates. To demonstrate that GABA meets the criteria used to identify a substance as a neurotransmitter, the author examined GABA metabolism and synaptic interactions of inhibitory motor neurons in two leech species, Hirudo medicinalis and Haementeria ghilianii. Segmental ganglia of the leech ventral nerve cord and identified inhibitors have the capacity to synthesize GABA when incubated in the presence of the precursor glutamate. Application of GABA to cell bodies of excitatory motor neurons or muscle fibers innervated by the inhibitors hyperpolarizes the membrane potential of the target cell and activates a chloride ion conductance channel, similar to the inhibitory membrane response following intracellular stimulation of the inhibitor. Bicuculline methiodide (5 x 10/sup -5/M), GABA receptor antagonist, blocks reversibly the response to applied GABA and the inhibitory synaptic inputs onto the postsynaptic neurons or muscle fibers without interfering with their excitatory inputs. Furthermore, the inhibitors are included among approximately 25 neurons per segmental ganglion that take up GABA by a high affinity uptake system, as revealed by /sup 3/H-GABA-autoradiography. The development of the capacities to synthesize and to take up GABA were examined in leech embryos. The embryos are able to synthesize GABA at early stages of the development of the nervous system, before any neurons have extended neutrites.

Cline, H.T.



The Role of Gamma-Aminobutyric Acid in the Inhibitory Mechanism of Mammalian Central Nervous System.  

National Technical Information Service (NTIS)

Since nerve cells of large sizes were isolated from various nuclei of cat brain stem; for each isolated nerve cell, its gamma aminobutyric acid (GABA) content was measured and the GABA concentration calculated. In two cats, cerebellar vermis was removed, ...

M. Otsuka



Astrocytic Control of Biosynthesis and Turnover of the Neurotransmitters Glutamate and GABA  

PubMed Central

Glutamate and GABA are the quantitatively major neurotransmitters in the brain mediating excitatory and inhibitory signaling, respectively. These amino acids are metabolically interrelated and at the same time they are tightly coupled to the intermediary metabolism including energy homeostasis. Astrocytes play a pivotal role in the maintenance of the neurotransmitter pools of glutamate and GABA since only these cells express pyruvate carboxylase, the enzyme required for de novo synthesis of the two amino acids. Such de novo synthesis is obligatory to compensate for catabolism of glutamate and GABA related to oxidative metabolism when the amino acids are used as energy substrates. This, in turn, is influenced by the extent to which the cycling of the amino acids between neurons and astrocytes may occur. This cycling is brought about by the glutamate/GABA – glutamine cycle the operation of which involves the enzymes glutamine synthetase (GS) and phosphate-activated glutaminase together with the plasma membrane transporters for glutamate, GABA, and glutamine. The distribution of these proteins between neurons and astrocytes determines the efficacy of the cycle and it is of particular importance that GS is exclusively expressed in astrocytes. It should be kept in mind that the operation of the cycle is associated with movement of ammonia nitrogen between the two cell types and different mechanisms which can mediate this have been proposed. This review is intended to delineate the above mentioned processes and to discuss quantitatively their relative importance in the homeostatic mechanisms responsible for the maintenance of optimal conditions for the respective neurotransmission processes to operate.

Schousboe, Arne; Bak, Lasse K.; Waagepetersen, Helle S.



Opioid-induced GABA potentiation after chronic morphine attenuates the rewarding effects of opioids in the ventral tegmental area  

PubMed Central

Gamma-aminobutyric acid (GABA) transmission in the ventral tegmental area (VTA) is critical for fine tuning the activity of dopamine neurons in response to opioids. However, the precise mechanism by which GABA input shapes opioid reward is poorly understood. One day after chronic morphine treatment, we observed a reduction of conditioned place preference (CPP) for low doses of the opioid [D-Ala2, N-MePhe4, Gly5-ol]-enkephalin (DAMGO) and a switch in the functional effects of mu-opioid receptor modulation of GABA postsynaptic currents in the mouse VTA. Specifically, while in naïve mice DAMGO inhibits GABA post-synaptic currents, after chronic morphine treatment, GABAergic currents are instead potentiated by DAMGO. Importantly, pre-treatment with the 3’–5’-cyclic-adenosine monophosphate (cAMP) signaling inhibitor (R)-Adenosine, cyclic 3',5'-(hydrogenphosphorothioate) triethylammonium (rp-cAMPS), both restored DAMGO reward and reversed the DAMGO mediated potentiation, thereby re-establishing the inhibitory effects of opioids on GABA currents. Thus, a paradoxical bidirectionality in mu-receptor mediated control of GABA transmission following chronic morphine treatment is a critical mechanism that determines the expression of opioid reward in the VTA.

Madhavan, Anuradha; Bonci, Antonello; Whistler, Jennifer L.



Effects of benzodiazepines and non-benzodiazepine compounds on the GABA-induced response in frog isolated sensory neurones.  

PubMed Central

1. The effects of benzodiazepines and non-benzodiazepine compounds on the gamma-aminobutyric acid (GABA)-induced chloride current (ICl) were studied in frog isolated sensory neurones by use of a concentration-jump (termed 'concentration-clamp') technique, under single-electrode voltage-clamp conditions. The drugs used were classified into four categories as follows: full benzodiazepine receptor agonists (diazepam, clonazepam, nitrazepam, midazolam, clotiazepam and etizolam), partial agonists (CL 218,872, Ro 16-6028, Ro 17-1812 and Ro 23-0364), inverse agonists (Ro 15-3505, FG 7142 and beta-CCE) and a benzodiazepine receptor antagonist, Ro 15-1788 (flumazenil). 2. All full agonists at concentrations of 3 x 10(-6) M or less increased dose-dependently the peak amplitude of ICl elicited by 3 x 10(-6) M GABA to twice to three times larger than the control. However, no further augmentation of the GABA response was observed at concentrations of 1 x 10(-5) M or higher. Partial agonists also showed a dose-dependent augmentation of the GABA response at concentrations ranging from 3 x 10(-8) M to 3 x 10(-5) M, but their efficacies of augmentation of the GABA response were only about half or less of those of full agonists. Of the inverse agonists, beta-CCE had a unique dose-dependent effect on the GABA response. Beta-CCE reduced dose-dependently the GABA response at concentrations of less than 3 x 10(-6) M, but augmented it at concentrations of 3 x 10(-5) M and 6 x 10(-5) M. The inverse agonists reduced dose-dependently the GABA response.(ABSTRACT TRUNCATED AT 250 WORDS)

Yakushiji, T.; Fukuda, T.; Oyama, Y.; Akaike, N.



In Vivo Measurement of Brain GABA Concentrations by Magnetic Resonance Spectroscopy in Smelters Occupationally Exposed to Manganese  

PubMed Central

Background Exposure to excessive levels of manganese (Mn) is known to induce psychiatric and motor disorders, including parkinsonian symptoms. Therefore, finding a reliable means for early detection of Mn neurotoxicity is desirable. Objectives Our goal was to determine whether in vivo brain levels of ?-aminobutyric acid (GABA), N-acetylaspartate (NAA), and other brain metabolites in male smelters were altered as a consequence of Mn exposure. Methods We used T1-weighted magnetic resonance imaging (MRI) to visualize Mn deposition in the brain. Magnetic resonance spectroscopy (MRS) was used to quantify concentrations of NAA, glutamate, and other brain metabolites in globus pallidus, putamen, thalamus, and frontal cortex from a well-established cohort of 10 male Mn-exposed smelters and 10 male age-matched control subjects. We used the MEGA-PRESS MRS sequence to determine GABA levels in a region encompassing the thalamus and adjacent parts of the basal ganglia [GABA-VOI (volume of interest)]. Results Seven of 10 exposed subjects showed clear T1-hyperintense signals in the globus pallidus indicating Mn accumulation. We found a significant increase (82%; p = 0.014) in the ratio of GABA to total creatine (GABA/tCr) in the GABA-VOI of Mn-exposed subjects, as well as a distinct decrease (9%; p = 0.04) of NAA/tCr in frontal cortex that strongly correlated with cumulative Mn exposure (R = ?0.93; p < 0.001). Conclusions We demonstrated elevated GABA levels in the thalamus and adjacent basal ganglia and decreased NAA levels in the frontal cortex, indicating neuronal dysfunction in a brain area not primarily targeted by Mn. Therefore, the noninvasive in vivo MRS measurement of GABA and NAA may prove to be a powerful tool for detecting presymptomatic effects of Mn neurotoxicity.

Dydak, Ulrike; Jiang, Yue-Ming; Long, Li-Ling; Zhu, He; Chen, Jian; Li, Wen-Mei; Edden, Richard A.E.; Hu, Shuguang; Fu, Xue; Long, Zaiyang; Mo, Xue-An; Meier, Dieter; Harezlak, Jaroslaw; Aschner, Michael; Murdoch, James B.; Zheng, Wei



Contingent and non-contingent effects of heroin on mu-opioid receptor-containing ventral tegmental area GABA neurons.  


Opiate activation of mu-opioid receptors (muORs) in the ventral tegmental area (VTA) modulates gamma-aminobutyric acid (GABA) neurotransmission within the mesocorticolimbic dopamine (DA) reward system. We combined in vivo extracellular electrophysiological recordings in anesthetized and freely behaving rats with intracellular Neurobiotin filling and immunocytochemistry to characterize the effects of opiates on VTA GABA neurons, evaluate their discharge activity during opiate self-administration, and identify the cellular sites for opiate activation. We identified a subpopulation of VTA GABA neurons that was characterized by location, spike discharge profile, activation by microelectrophoretic DA, and response to internal capsule (IC) stimulation. Systemic administration of heroin or microelectrophoretic application of the selective muOR agonist [d-Ala2, N-Me-Phe4, Gly-ol]-Enkephalin (DAMGO) reduced VTA GABA neuron firing rate (heroin IC(50) = 0.35 mg/kg) and was blocked by the muOR antagonist naloxone. Heroin also reduced IC-evoked post-stimulus spike discharges, a manifestation of gap-junction-mediated electrical coupling between VTA GABA neurons. The baseline firing rate of VTA GABA neurons significantly increased (239%) following the acquisition of heroin self-administration behavior and transiently increased during each response for heroin (105%), but decreased (49%) following heroin, similar to non-contingent heroin. Electrophysiologically characterized VTA GABA neurons were filled with Neurobiotin and labeled dendrites contained plasmalemmal muOR immunoreactivity. Dually labeled muOR dendrites contained dendrodendritic appositions characteristic of gap junctions. These findings indicate that inhibition of this population of GABAergic neurons by opiates acting on dendritic muORs has implications for modulation of electrical coupling between VTA GABA neurons and dopamine (DA) neurotransmission in the VTA and terminal field regions. PMID:16814775

Steffensen, Scott C; Stobbs, Sarah H; Colago, Eric E O; Lee, Rong-Sheng; Koob, George F; Gallegos, Roger A; Henriksen, Steven J



Selective distribution of GABA(A) receptor subtypes in mouse spinal dorsal horn neurons and primary afferents.  


In the spinal cord dorsal horn, presynaptic GABA(A) receptors (GABA(A)Rs) in the terminals of nociceptors as well as postsynaptic receptors in spinal neurons regulate the transmission of nociceptive and somatosensory signals from the periphery. GABA(A)Rs are heterogeneous and distinguished functionally and pharmacologically by the type of ? subunit variant they contain. This heterogeneity raises the possibility that GABA(A)R subtypes differentially regulate specific pain modalities. Here, we characterized the subcellular distribution of GABA(A)R subtypes in nociceptive circuits by using immunohistochemistry with subunit-specific antibodies combined with markers of primary afferents and dorsal horn neurons. Confocal laser scanning microscopy analysis revealed a distinct, partially overlapping laminar distribution of ?1-3 and ?5 subunit immunoreactivity in laminae I-V. Likewise, a layer-specific pattern was evident for their distribution among glutamatergic, ?-aminobutyric acid (GABA)ergic, and glycinergic neurons (detected in transgenic mice expressing vesicular glutamate transporter 2-enhanced green fluorescent protein [vGluT2-eGFP], glutamic acid decarboxylase [GAD]67-eGFP, and glycine transporter 2 (GlyT2)-eGFP, respectively). Finally, all four subunits could be detected within primary afferent terminals. C-fibers predominantly contained either ?2 or ?3 subunit immunoreactivity; terminals from myelinated (A?/A?) fibers were colabeled in roughly equal proportion with each subunit. The presence of axoaxonic GABAergic synapses was determined by costaining with gephyrin and vesicular inhibitory amino acid transporter to label GABAergic postsynaptic densities and terminals, respectively. Colocalization of the ?2 or ?3 subunit with these markers was observed in a subset of C-fiber synapses. Furthermore, gephyrin mRNA and protein expression was detected in dorsal root ganglia. Collectively, these results show that differential GABA(A)R distribution in primary afferent terminals and dorsal horn neurons allows for multiple, circuit-specific modes of regulation of nociceptive circuits. PMID:22522945

Paul, Jolly; Zeilhofer, Hanns Ulrich; Fritschy, Jean-Marc



Ventral tegmental area GABA projections pause accumbal cholinergic interneurons to enhance associative learning.  


The ventral tegmental area (VTA) and nucleus accumbens (NAc) are essential for learning about environmental stimuli associated with motivationally relevant outcomes. The task of signalling such events, both rewarding and aversive, from the VTA to the NAc has largely been ascribed to dopamine neurons. The VTA also contains GABA (?-aminobutyric acid)-releasing neurons, which provide local inhibition and also project to the NAc. However, the cellular targets and functional importance of this long-range inhibitory projection have not been ascertained. Here we show that GABA-releasing neurons of the VTA that project to the NAc (VTA GABA projection neurons) inhibit accumbal cholinergic interneurons (CINs) to enhance stimulus-outcome learning. Combining optogenetics with structural imaging and electrophysiology, we found that VTA GABA projection neurons selectively target NAc CINs, forming multiple symmetrical synaptic contacts that generated inhibitory postsynaptic currents. This is remarkable considering that CINs represent a very small population of all accumbal neurons, and provide the primary source of cholinergic tone in the NAc. Brief activation of this projection was sufficient to halt the spontaneous activity of NAc CINs, resembling the pause recorded in animals learning stimulus-outcome associations. Indeed, we found that forcing CINs to pause in behaving mice enhanced discrimination of a motivationally important stimulus that had been associated with an aversive outcome. Our results demonstrate that VTA GABA projection neurons, through their selective targeting of accumbal CINs, provide a novel route through which the VTA communicates saliency to the NAc. VTA GABA projection neurons thus emerge as orchestrators of dopaminergic and cholinergic modulation in the NAc. PMID:23178810

Brown, Matthew T C; Tan, Kelly R; O'Connor, Eoin C; Nikonenko, Irina; Muller, Dominique; Lüscher, Christian



Hydroxylated biphenyl derivatives are positive modulators of human GABA(A) receptors.  


A series of 7 hydroxylated biphenyl derivatives (1-7) were prepared to evaluate their ability to modulate the function of several ligand gated ion channel (LGIC) recombinant receptors expressed in Xenopus laevis oocytes. Compounds 1, 3, 4, 6 and 7 are natural occurring compounds whereas the synthesis of compounds 2 and 5 was previously reported (Delogu et al., 2004; Fabbri et al., 2007). None of the compounds tested were able to modify, the activity of the strychnine-sensitive glycine receptor, or the activity of nicotinic receptor. The function of the 5HT(3A) receptor was partially inhibited by all compounds tested, however this inhibition occurred at relatively high concentrations (100 ?M). All compounds, with the exception of compound 6, potentiate the action of gamma-aminobutyric acid (GABA)-evoked Cl(-) currents in Xenopus laevis oocytes expressing recombinant human ?(1)?(2)?(2L) GABA(A) receptors. Compounds 1, 2, 5 and 7 enhance the function of the GABA(A) receptor at concentrations higher than 3-10 ?M. Compound 4 was the most efficacious. However, compound 3 was the most potent (EC(50) 0.8 ?M). The potency of compound 3 in modulating the function of the GABA(A) receptor was comparable to that of diazepam, propofol or allopregnanolone. The enhancement of the GABA evoked Cl(-) currents by compound 3 was not affected by flumazenil. Compound 3 did not induce loss of the righting reflex in rats suggesting that it is not an anesthetic agent, however, its ability in protecting the animals from seizures induced by picrotoxin confirm that its action occurs through the GABA(A) receptor. PMID:22959356

Paola Mascia, Maria; Fabbri, Davide; Antonietta Dettori, Maria; Ledda, Giovanni; Delogu, Giovanna; Biggio, Giovanni



The benzodiazepine site of the GABA A receptor: an old target with new potential?  

Microsoft Academic Search

The gamma-aminobutyric acid-A (GABAA) receptors is the target for the most widely prescribed sleep medicines. It is a ligand-gated ion channel, activated by the amino acid neurotransmitter GABA, which normally results in hyperpolarization of neurons leading to reduced action potential firing, and thereby a reduction in neuronal activity. It has a rich pharmacology with a number of separate modulator binding

Alan N Bateson



Measurement of GABA using J-difference edited 1H-MRS following modulation of synaptic GABA concentration with tiagabine.  


Though GABA is the major inhibitory neurotransmitter in the brain, involved in a wide variety of brain functions and many neuropsychiatric disorders, its intracellular and metabolic presence provides uncertainty in the interpretation of the GABA signal measured by (1)H-MRS. Previous studies demonstrating the sensitivity of this technique to pharmacological manipulations of GABA have used nonspecific challenges that make it difficult to infer the exact source of the changes. In this study, the synaptic GABA reuptake inhibitor tiagabine, which selectively blocks GAT1, was used to test the sensitivity of J-difference edited (1)H-MRS to changes in extracellular GABA concentrations. MEGA-PRESS was used to obtain GABA-edited spectra in 10 male individuals, before and after a 15-mg oral dose of tiagabine. In the three voxels measured, no significant changes were found in GABA+ concentration after the challenge compared to baseline. This dose of tiagabine is known to modulate synaptic GABA and neurotransmission through studies using other imaging modalities, and significant increases in self-reported sleepiness scales were observed. Therefore, it is concluded that recompartmentalization of GABA through transport block does not have a significant impact on total GABA concentration. Furthermore, it is likely that the majority of the magnetic resonance spectroscopy (MRS)-derived GABA signal is intracellular. It should be considered, in individual interpretation of GABA MRS studies, whether it is appropriate to attribute observed effects to changes in neurotransmission. PMID:24756906

Myers, James F M; Evans, C John; Kalk, Nicola J; Edden, Richard A E; Lingford-Hughes, Anne R



Metabolic compartmentation in cortical synaptosomes: influence of glucose and preferential incorporation of endogenous glutamate into GABA.  


Metabolism of glutamine was determined under a variety of conditions to study compartmentation in cortical synaptosomes. The combined intracellular and extracellular amounts of [U-13C] GABA, [U-13C]glutamate and [U-13C]glutamine were the same in synaptosomes incubated with U-13C]glutamine in the presence and absence of glucose. However, the concentration of these amino acids was decreased in the latter group, demonstrating the requirement for glucose to maintain the size of neurotransmitter pools. In hypoglycemic synaptosomes more [U-13C]glutamine was converted to [U-13C]aspartate, and less glutamate was re-synthesized from the tricarboxylic acid (TCA) cycle, suggesting use of the partial TCA cycle from alpha-ketoglutarate to oxaloacetate for energy. Compartmentation was studied in synaptosomes incubated with glucose plus labeled and unlabeled glutamine and glutamate. Incubation with [U-13C]glutamine plus unlabeled glutamate gave rise to [U-13C]GABA but not labeled aspartate; however, incubation with [U-13C]glutamate plus unlabeled glutamine gave rise to [U-13C]aspartate, but not labeled GABA. Thus the endogenous glutamate formed via glutaminase in synaptic terminals is preferentially used for GABA synthesis, and is metabolized differently than glutamate taken up from the extracellular milieu. PMID:11926275

Sonnewald, Ursula; McKenna, Mary



Immunoreactivity for GABA, GAD65, GAD67 and Bestrophin-1 in the Meninges and the Choroid Plexus: Implications for Non-Neuronal Sources for GABA in the Developing Mouse Brain  

PubMed Central

Neural progenitors in the developing neocortex, neuroepithelial cells and radial glial cells, have a bipolar shape with a basal process contacting the basal membrane of the meninge and an apical plasma membrane facing the lateral ventricle, which the cerebrospinal fluid is filled with. Recent studies revealed that the meninges and the cerebrospinal fluid have certain roles to regulate brain development. ?-aminobutyric acid (GABA) is a neurotransmitter which appears first during development and works as a diffusible factor to regulate the properties of neural progenitors. In this study, we examined whether GABA can be released from the meninges and the choroid plexus in the developing mouse brain. Immunohistochemical analyses showed that glutamic acid decarboxylase 65 and 67 (GAD65 and GAD67), both of which are GABA-synthesizing enzymes, are expressed in the meninges. The epithelial cells in the choroid plexus express GAD65. GABA immunoreactivity could be observed beneath the basal membrane of the meninge and in the epithelial cells of the choroid plexus. Expression analyses on Bestrophin-1, which is known as a GABA-permeable channel in differentiated glial cells, suggested that the cells in the meninges and the epithelial cells in the choroid plexus have the channels able to permeate non-synaptic GABA into the extracellular space. Further studies showed that GAD65/67-expressing meningeal cells appear in a manner with rostral to caudal and lateral to dorsal gradient to cover the entire neocortex by E14.5 during development, while the cells in the choroid plexus in the lateral ventricle start to express GAD65 on E11–E12, the time when the choroid plexus starts to develop in the developing brain. These results totally suggest that the meninges and the choroid plexus can work as non-neuronal sources for ambient GABA which can modulate the properties of neural progenitors during neocortical development.

Tochitani, Shiro; Kondo, Shigeaki



Frontal GABA levels change during working memory.  


Functional neuroimaging metrics are thought to reflect changes in neurotransmitter flux, but changes in neurotransmitter levels have not been demonstrated in humans during a cognitive task, and the relationship between neurotransmitter dynamics and hemodynamic activity during cognition has not yet been established. We evaluate the concentration of the major inhibitory (GABA) and excitatory (glutamate + glutamine: Glx) neurotransmitters and the cerebral perfusion at rest and during a prolonged delayed match-to-sample working memory task. Resting GABA levels in the dorsolateral prefrontal cortex correlated positively with the resting perfusion and inversely with the change in perfusion during the task. Further, only GABA increased significantly during the first working memory run and then decreased continuously across subsequent task runs. The decrease of GABA over time was paralleled by a trend towards decreased reaction times and higher task accuracy. These results demonstrate a link between neurotransmitter dynamics and hemodynamic activity during working memory, indicating that functional neuroimaging metrics depend on the balance of excitation and inhibition required for cognitive processing. PMID:22485128

Michels, Lars; Martin, Ernst; Klaver, Peter; Edden, Richard; Zelaya, Fernando; Lythgoe, David J; Lüchinger, Rafael; Brandeis, Daniel; O'Gorman, Ruth L



Frontal GABA Levels Change during Working Memory  

PubMed Central

Functional neuroimaging metrics are thought to reflect changes in neurotransmitter flux, but changes in neurotransmitter levels have not been demonstrated in humans during a cognitive task, and the relationship between neurotransmitter dynamics and hemodynamic activity during cognition has not yet been established. We evaluate the concentration of the major inhibitory (GABA) and excitatory (glutamate + glutamine: Glx) neurotransmitters and the cerebral perfusion at rest and during a prolonged delayed match-to-sample working memory task. Resting GABA levels in the dorsolateral prefrontal cortex correlated positively with the resting perfusion and inversely with the change in perfusion during the task. Further, only GABA increased significantly during the first working memory run and then decreased continuously across subsequent task runs. The decrease of GABA over time was paralleled by a trend towards decreased reaction times and higher task accuracy. These results demonstrate a link between neurotransmitter dynamics and hemodynamic activity during working memory, indicating that functional neuroimaging metrics depend on the balance of excitation and inhibition required for cognitive processing.

Martin, Ernst; Klaver, Peter; Edden, Richard; Zelaya, Fernando; Lythgoe, David J.; Luchinger, Rafael; Brandeis, Daniel



Acoustic Immunosensor for Detecting Neurotransmitter GABA.  

National Technical Information Service (NTIS)

Acoustic impedance immunosensors are disclosed that are capable of real-time measurement of GABA in a buffer solution. Several embodiments include a bio-specific recognition layer on a quartz crystal surface, where the bio-recognition layer is formed by m...

A. Zhou J. Muthuswamy



GABA binding to an insect GABA receptor: a molecular dynamics and mutagenesis study.  


RDL receptors are GABA-activated inhibitory Cys-loop receptors found throughout the insect CNS. They are a key target for insecticides. Here, we characterize the GABA binding site in RDL receptors using computational and electrophysiological techniques. A homology model of the extracellular domain of RDL was generated and GABA docked into the binding site. Molecular dynamics simulations predicted critical GABA binding interactions with aromatic residues F206, Y254, and Y109 and hydrophilic residues E204, S176, R111, R166, S176, and T251. These residues were mutated, expressed in Xenopus oocytes, and their functions assessed using electrophysiology. The data support the binding mechanism provided by the simulations, which predict that GABA forms many interactions with binding site residues, the most significant of which are cation-? interactions with F206 and Y254, H-bonds with E204, S205, R111, S176, T251, and ionic interactions with R111 and E204. These findings clarify the roles of a range of residues in binding GABA in the RDL receptor, and also show that molecular dynamics simulations are a useful tool to identify specific interactions in Cys-loop receptors. PMID:23200041

Ashby, Jamie A; McGonigle, Ian V; Price, Kerry L; Cohen, Netta; Comitani, Federico; Dougherty, Dennis A; Molteni, Carla; Lummis, Sarah C R



Activation of VTA GABA neurons disrupts reward consumption  

PubMed Central

The activity of Ventral Tegmental Area (VTA) dopamine (DA) neurons promotes behavioral responses to rewards and environmental stimuli that predict them. VTA GABA inputs synapse directly onto DA neurons and may regulate DA neuronal activity to alter reward-related behaviors, however, the functional consequences of selective activation of VTA GABA neurons remains unknown. Here, we show that in vivo optogenetic activation of VTA GABA neurons disrupts reward consummatory behavior, but not conditioned anticipatory behavior in response to reward-predictive cues. In addition, direct activation of VTA GABA projections to the nucleus accumbens (NAc) resulted in detectable GABA release, but did not alter reward consumption. Furthermore, optogenetic stimulation of VTA GABA neurons directly suppressed the activity and excitability of neighboring DA neurons, as well as the release of DA in the NAc, suggesting that the dynamic interplay between VTA DA and GABA neurons can control the initiation and termination of reward-related behaviors.

van Zessen, Ruud; Phillips, Jana L.; Budygin, Evgeny A.; Stuber, Garret D.



GABA{sub A} receptor open-state conformation determines non-competitive antagonist binding  

SciTech Connect

The {gamma}-aminobutyric acid (GABA) type A receptor (GABA{sub A}R) is one of the most important targets for insecticide action. The human recombinant {beta}3 homomer is the best available model for this binding site and 4-n-[{sup 3}H]propyl-4'-ethynylbicycloorthobenzoate ([{sup 3}H]EBOB) is the preferred non-competitive antagonist (NCA) radioligand. The uniquely high sensitivity of the {beta}3 homomer relative to the much-less-active but structurally very-similar {beta}1 homomer provides an ideal comparison to elucidate structural and functional features important for NCA binding. The {beta}1 and {beta}3 subunits were compared using chimeragenesis and mutagenesis and various combinations with the {alpha}1 subunit and modulators. Chimera {beta}3/{beta}1 with the {beta}3 subunit extracellular domain and the {beta}1 subunit transmembrane helices retained the high [{sup 3}H]EBOB binding level of the {beta}3 homomer while chimera {beta}1/{beta}3 with the {beta}1 subunit extracellular domain and the {beta}3 subunit transmembrane helices had low binding activity similar to the {beta}1 homomer. GABA at 3 {mu}M stimulated heteromers {alpha}1{beta}1 and {alpha}1{beta}3 binding levels more than 2-fold by increasing the open probability of the channel. Addition of the {alpha}1 subunit rescued the inactive {beta}1/{beta}3 chimera close to wildtype {alpha}1{beta}1 activity. EBOB binding was significantly altered by mutations {beta}1S15'N and {beta}3N15'S compared with wildtype {beta}1 and {beta}3, respectively. However, the binding activity of {alpha}1{beta}1S15'N was insensitive to GABA and {alpha}1{beta}3N15'S was stimulated much less than wildtype {alpha}1{beta}3 by GABA. The inhibitory effect of etomidate on NCA binding was reduced more than 5-fold by the mutation {beta}3N15'S. Therefore, the NCA binding site is tightly regulated by the open-state conformation that largely determines GABA{sub A} receptor sensitivity. - Graphical Abstract: Display Omitted Research Highlights: > The {beta}1 and {beta}3 subunits were compared by chimeragenesis, mutagenesis and modulators. > Low {beta}1 NCA binding was rescued by replacing its transmembrane helices with those of {beta}3. > GABA at 3 {mu}M stimulated heteromers {alpha}1{beta}1 and {alpha}1{beta}3 binding levels more than 2-fold. > Mutation at 15' position in TM2 reduced GABA stimulation of NCA binding. > The open-state conformation largely determines GABAA receptor sensitivity to NCAs.

Chen Ligong [Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720 (United States); Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158 (United States); Xue Ling [Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720 (United States); Giacomini, Kathleen M. [Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158 (United States); Casida, John E., E-mail: [Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720 (United States)



Taurine-like GABA aminotransferase inhibitors prevent rabbit brain slices against oxygen-glucose deprivation-induced damage.  


The activation of the GABAergic system has been shown to protect brain tissues against the damage that occurs after cerebral ischaemia. On the other hand, the taurine analogues (±)Piperidine-3-sulphonic- (PSA), 2-aminoethane phosphonic- (AEP), 2-(N-acetylamino) cyclohexane sulfonic-acids (ATAHS) and 2-aminobenzene sulfonate-acids (ANSA) have been reported to block GABA metabolism by inhibiting rabbit brain GABA aminotransferase and to increase GABA content in rabbit brain slices. The present investigation explored the neuroprotection provided by GABA, Vigabatrin (VIGA) and taurine analogues in the course of oxygen-glucose deprivation and reperfusion induced damage of rabbit brain slices. Tissue damage was assessed by measuring the release of glutamate and lactate dehydrogenase (LDH) during reperfusion and by determining final tissue water gain, measured as the index of cell swelling. GABA (30-300 ?M) and VIGA (30-300 ?M) significantly antagonised LDH and glutamate release, as well as tissue water gain caused by oxygen-glucose deprivation and reperfusion. Lower (1-10 ?M) or higher concentrations (up to 3,000 ?M) were ineffective. ANSA, PSA and ATAHS significantly reduced glutamate and LDH release and tissue water gain in a range of concentrations between 30 and 300 ?M. Lower (0-10 ?M) or higher (up to 3,000 ?M) concentrations were ineffective. Both mechanisms suggest hormetic ("U-shaped") effects. These results indicate that the GABAergic system activation performed directly by GABA or indirectly through GABA aminotransferase inhibition is a promising approach for protecting the brain against ischemia and reperfusion-induced damage. PMID:21667265

Ricci, Lorenzo; Valoti, Massimo; Sgaragli, Giampietro; Frosini, Maria



Agonist- and antagonist-induced conformational changes of loop F and their contributions to the rho1 GABA receptor function.  


Binding of gamma-aminobutyric acid (GABA) to its receptor initiates a conformational change to open the channel, but the mechanism of the channel activation is not well understood. To this end, we scanned loop F (K210-F227) in the N-terminal domain of the rho1 GABA receptor expressed in Xenopus oocytes using a site-specific fluorescence technique. We detected GABA-induced fluorescence changes at six positions (K210, K211, L216, K217, T218 and I222). At these positions the fluorescence changes were dose dependent and highly correlated to the current dose-response, but with lower Hill coefficients. The competitive antagonist 3-aminopropyl(methyl)phosphinic acid (3-APMPA) induced fluorescence changes in the same direction at the four middle or lower positions. The non-competitive antagonist picrotoxin blocked nearly 50% of GABA-induced fluorescence changes at T218 and I222, but only <20% at K210 and K217 and 0% at K211 and L216 positions. Interestingly, the picrotoxin-blocked fraction of the GABA-induced fluorescence changes was highly correlated to the Hill coefficient of the GABA-induced dose-dependent fluorescence change. The PTX-insensitive mutant L216C exhibited the lowest Hill coefficient, similar to that in binding. Thus, the PTX-sensitive fraction reflects the conformational change related to channel gating, whereas the PTX-insensitive fraction represents a binding effect. The binding effect is further supported by the picrotoxin resistance of a competitive antagonist-induced fluorescence change. A cysteine accessibility test further confirmed that L216C and K217C partially line the binding pocket, and I222C became more exposed by GABA. Our results are consistent with a mechanism that an outward movement of the lower part of loop F is coupled to the channel activation. PMID:19015197

Zhang, Jianliang; Xue, Fenqin; Chang, Yongchang



[Effect of synaptosomal cytosolic [3H]GABA pool depletion on secretory ability of alpha-latrotoxin].  


alpha-Latrotoxin, a presynaptic neurotoxin from the venom of Latrodectus mactans tredecimguttatus, induces massive [3H]GABA release from rat brain synaptosomes as a result of interaction with either Ca(2+)-dependent (neurexin 1 alpha or Ca(2+)-independent (latrophilin) membrane receptor. The main aim of the study was to elucidate whether the binding of alpha-latrotoxin to different types of receptors led to [3H]GABA secretion from one pool or in each case the source of neurotransmitter differs: in the presence of Ca2+ exocytosis is induced, while in the absence of Ca(2+)--outflow by mobile membrane GABA transporter from cytoplasm. We examined the effect of the depletion of cytosolic [3H]GABA pool by competitive inhibitors of the GABA transporter (nipecotic acid and 2,4-diaminobutyric acid) on the alpha-latrotoxin-stimulated neurotransmitter release. We also compared the influence of these agents on neurosecretion, evoked by depolarization with that evoked by alpha-latrotoxin. Depolarization was stimulated by 4-aminopyridine in the Ca(2+)-containing saline and high KCl in Ca(2+)-free medium. In synaptosomes treated with nipecotic acid unstimulated [3H]GABA release was significantly augmented and high KCl-evoked Ca(2+)-independent [3H]GABA release was essentially inhibited. But under the same conditions neurosecretion stimulated by alpha-latrotoxin greatly raised with respect to the control response. The similar results were obtained with the synaptosomes treated with 2,4-diaminobutyric acid. Another way to determine which of GABA pool is the target of alpha-latrotoxin action lay in analysis of the toxin effects on the preliminary depolarized synaptosomes. alpha-Latrotoxin influence was diminished by the preceding depolarization by 4-aminopyridine in Ca2+ presence. But after the high KCl stimulation effect of alpha-latrotoxin didn't change. These data suggest that alpha-latrotoxin triggers neurotransmitter release from synaptic vesicles via exocytosis. We suppose that the type of membrane receptor does not determine the mechanism of GABA release evoked by the toxin. PMID:12916239

Linets'ka, M V; Storchak, L H; Himmelre?ch, N H



Isothiouronium compounds as gamma-aminobutyric acid agonists.  


Analogues of gamma-aminobutyric acid (GABA) incorporating an isothiouronium salt as a replacement for a protonated amino functional group have been investigated for activity on: GABA receptors in the guinea-pig ileum; [3H]-GABA and [3H]-diazepam binding to rat brain membranes; and GABA uptake and transamination. For the homologous series of omega-isothiouronium alkanoic acids, maximum GABA-mimetic activity was found at 3-[(aminoiminomethyl)thio]propanoic acid. Introduction of unsaturation into this compound gave two isomeric conformationally restricted analogues. The trans isomer was inactive at GABA receptors while the cis compound ((Z)-3-[(aminoiminomethyl)thio]prop-2-enoic acid (ZAPA)) was more potent than muscimol and GABA as a GABA agonist with respect to low affinity GABA receptor sites. Both isomers were moderately potent at inhibiting the uptake of [3H]-GABA into rat brain slices. Comparison of possible conformations of the two unsaturated isomers by interactive computer graphics modelling and comparison with muscimol has led to a plausible active conformation of ZAPA, which may be a selective and potent agonist for low affinity GABA binding sites. PMID:3015310

Allan, R D; Dickenson, H W; Hiern, B P; Johnston, G A; Kazlauskas, R



In vitro changes in gamma-aminobutyric acid output from the cerebral cortex induced by inhibitors of gamma-aminobutyric acid uptake and metabolism.  


The effects of inhibitors of gamma-aminobutyric acid (GABA) metabolism or uptake on GABA output from the cerebral cortex was studied by means of a collecting cup placed on the exposed cortex of rats anaesthetized with urethane. GABA was identified and quantified by a mass-fragmentographic method. Ethanolamine-O-sulphate (10(-2) M) applied directly on the cerebral cortex caused a long-lasting twofold increase in GABA output, whereas DL-2,4-diaminobutyric acid (5 X 10(-3) M) caused a sevenfold increase and beta-alanine was active. The results indicate that glial uptake has little effect on GABA inactivation in the cerebral cortex. The inhibition of neuronal uptake seems a more effective tool to increase GABA concentration in the synaptic cleft, and consequently also in GABA output, than the inhibition of GABA metabolism. PMID:7086436

Moroni, F; Mulas, A; Moneti, G; Pepeu, G



Neuroprotection of ethanol against ischemia\\/reperfusion-induced brain injury through decreasing c-Jun N-terminal kinase 3 (JNK3) activation by enhancing GABA release  

Microsoft Academic Search

Our latest study indicated that ethanol could attenuate cerebral ischemia\\/reperfusion-induced brain injury through activating Ionotropic glutamate receptors Kainate Family (Gluk1)–kainate (KA) receptors and gamma-aminobutyric acid (GABA) receptors. However, the possible mechanism of the neuroprotective effects of ethanol remains unclear. In this study we report that ethanol shows neuroprotective effects against ischemic brain injury through enhancing GABA release and then decreasing

S.-H. Qi; Y. Liu; L.-Y. Hao; Q.-H. Guan; Y.-H. Gu; J. Zhang; H. Yan; M. Wang; G.-Y. Zhang



Huntington's disease. Cerebrospinal fluid GABA levels in at-risk individuals.  


Gamma-aminobutyric acid (GABA) was measured by the ion-exchange fluorometric method in CSF from 22 individuals at risk for Huntington's disease (HD), six individuals with HD, and five neurologically normal controls. The mean (+/- SD) GABA level in the specimens from patients with HD was 142 +/- 27 pmoles/ml, whereas that of the normal control specimens was 297 +/- 87 pmoles/ml. The mean GABA level of the specimens from the individuals at risk for HD was 209 +/- 79 pmoles/ml; however, nine of these were in the normal range with a mean value of 281 +/- 72 pmoles/ml, while the other 13 were below the normal range with a mean value of 159 +/- 27 pmoles/ml. The data indicate that low GABA levels in CSF are evident prior to the onset of symptoms of HD but a predictive value can only be determined by continued observation of the clinical course of these at-risk individuals. PMID:152621

Manyam, N V; Hare, T A; Katz, L; Glaeser, B S



Role of ACh-GABA cotransmission in detecting image motion and motion direction.  


Starburst amacrine cells (SACs) process complex visual signals in the retina using both acetylcholine (ACh) and gamma-aminobutyric acid (GABA), but the synaptic organization and function of ACh-GABA corelease remain unclear. Here, we show that SACs make cholinergic synapses onto On-Off direction-selective ganglion cells (DSGCs) from all directions but make GABAergic synapses onto DSGCs only from the null direction. ACh and GABA were released differentially in a Ca(2+) level-specific manner, suggesting the two transmitters were released from different vesicle populations. Despite the symmetric cholinergic connection, the light-evoked cholinergic input to a DSGC, detected at both light onset and offset, was motion- and direction-sensitive. This input was facilitated by two-spot apparent motion in the preferred direction but supressed in the null direction, presumably by a GABAergic mechanism. The results revealed a high level of synaptic intricacy in the starburst circuit and suggested differential, yet synergistic, roles of ACh-GABA cotransmission in motion sensitivity and direction selectivity. PMID:21172616

Lee, Seunghoon; Kim, Kyongmin; Zhou, Z Jimmy



Glutamic Acid Decarboxylase and Gamma-aminobutyric Acid in Mammalian Kidney  

Microsoft Academic Search

THE discovery of glutamic acid decarboxylase (GAD) in mammalian brain was first reported in 19501,2. The product of this enzyme reaction is gamma-aminobutyric acid (GABA), an important neuroinhibitor3. Because GABA occurs in large amounts in the central nervous system, subsequent interest in GAD emphasized its importance in brain to the exclusion of other tissues. But GABA is also present in

Donald T. Whelan; Charles R. Scriver; Fazl Mohyuddin



Regulation of GABA Receptor Activity by Neurosteroids and Phosphorylation  

NSDL National Science Digital Library

These two animations show two models for how neurosteroids regulate the flow of chloride ions (Cl-) through ionotropic gamma-aminobutyric acid (GABA) receptors. In the first model, binding of the neurosteroid allows a protein kinase C (PKC) phosphorylation site to become accessible. Phosphorylation of the channel increases flux through the channel. In the second model, phosphorylation by PKC allows the neurosteroid to bind and increase flux through the channel. The animations have two parts: (i) a diagrammatic representation of the sequence of events at the channel in the membrane and (ii) a representative current trace of data obtained using electrophysiological techniques. These animations would be useful in teaching how allosteric modulators (neurosteroids) and covalent modulators (kinases) can work together as regulators of protein activity.

Jeffrey Tasker (Tulane University;Department of Cell and Molecular Biology REV)



Prebiotic syntheses of vitamin coenzymes: II. Pantoic acid, pantothenic acid, and the composition of coenzyme A  

NASA Technical Reports Server (NTRS)

Pantoic acid can by synthesized in good prebiotic yield from isobutyraldehyde or alpha-ketoisovaleric acid + H2CO + HCN. Isobutyraldehyde is the Strecker precursor to valine and alpha-ketoisovaleric acid is the valine transamination product. Mg2+ and Ca2+ as well as several transition metals are catalysts for the alpha-ketoisovaleric acid reaction. Pantothenic acid is produced from pantoyl lactone (easily formed from pantoic acid) and the relatively high concentrations of beta-alanine that would be formed on drying prebiotic amino acid mixtures. There is no selectivity for this reaction over glycine, alanine, or gamma-amino butyric acid. The components of coenzyme A are discussed in terms of ease of prebiotic formation and stability and are shown to be plausible choices, but many other compounds are possible. The gamma-OH of pantoic acid needs to be capped to prevent decomposition of pantothenic acid. These results suggest that coenzyme A function was important in the earliest metabolic pathways and that the coenzyme A precursor contained most of the components of the present coenzyme.

Miller, S. L.; Schlesinger, G.



When and why amino acids?  

PubMed Central

This article reviews especially the early history of glutamate and GABA as neurotransmitters in vertebrates. The proposal that some amino acids could mediate synaptic transmission in the CNS initially met with much resistance. Both GABA and its parent glutamate are abundant in the brain; but, unlike glutamate, GABA had no obvious metabolic function. By the late 1950s, the switch of interest from electrical to chemical transmission invigorated the search for central transmitters. Its identification with Factor I, a brain extract that inhibited crustacean muscle, focused interest on GABA as a possible inhibitory transmitter. In the first microiontophoretic tests, though GABA strongly inhibited spinal neurons, these effects were considered ‘non-specific’. Strong excitation by glutamate (and other acidic amino acids) led to the same conclusion. However, their great potency and rapid actions on cortical neurons convinced other authors that these endogenous amino acids are probably synaptic transmitters. This was partly confirmed by showing that both IPSPs and GABA greatly increased Cl? conductance, their effects having similar reversal potentials. Many anticonvulsants proving to be GABA antagonists, by the 1970s GABA became widely accepted as a mediator of IPSPs. Progress was much slower for glutamate. Being generated on distant dendrites, EPSPs could not be easily compared with glutamate-induced excitation, and the search for specific antagonists was long hampered by the lack of blockers and the variety of glutamate receptors. These difficulties were gradually overcome by the application of powerful techniques, such as single channel recording, cloning receptors, as well as new pharmacological tools.

Krnjevic, Kresimir



Mutants of GABA Transaminase (POP2) Suppress the Severe Phenotype of succinic semialdehyde dehydrogenase (ssadh) Mutants in Arabidopsis  

PubMed Central

Background The ?-aminubutyrate (GABA) shunt bypasses two steps of the tricarboxylic acid cycle, and is present in both prokaryotes and eukaryotes. In plants, the pathway is composed of the calcium/calmodulin-regulated cytosolic enzyme glutamate decarboxylase (GAD), the mitochondrial enzymes GABA transaminase (GABA-T; POP2) and succinic semialdehyde dehydrogenase (SSADH). We have previously shown that compromising the function of the GABA-shunt, by disrupting the SSADH gene of Arabidopsis, causes enhanced accumulation of reactive oxygen intermediates (ROIs) and cell death in response to light and heat stress. However, to date, genetic investigations of the relationships between enzymes of the GABA shunt have not been reported. Principal Findings To elucidate the role of succinic semialdehyde (SSA), ?-hydroxybutyrate (GHB) and GABA in the accumulation of ROIs, we combined two genetic approaches to suppress the severe phenotype of ssadh mutants. Analysis of double pop2 ssadh mutants revealed that pop2 is epistatic to ssadh. Moreover, we isolated EMS-generated mutants suppressing the phenotype of ssadh revealing two new pop2 alleles. By measuring thermoluminescence at high temperature, the peroxide contents of ssadh and pop2 mutants were evaluated, showing that only ssadh plants accumulate peroxides. In addition, pop2 ssadh seedlings are more sensitive to exogenous SSA or GHB relative to wild type, because GHB and/or SSA accumulate in these plants. Significance We conclude that the lack of supply of succinate and NADH to the TCA cycle is not responsible for the oxidative stress and growth retardations of ssadh mutants. Rather, we suggest that the accumulation of SSA, GHB, or both, produced downstream of the GABA-T transamination step, is toxic to the plants, resulting in high ROI levels and impaired development.

Fromm, Hillel; Beauclair, Linda; Bouche, Nicolas



GABA(B)-mediated inhibition of multiple modes of glutamate release in the nucleus of the solitary tract.  


In the caudal portions of the solitary tract (ST) nucleus, primary sensory afferents fall into two broad classes based on the expression of transient receptor potential vanilloid type 1 (TRPV1) receptors. Both afferent classes (TRPV1+/-) have indistinguishable glutamate release mechanisms for ST-evoked excitatory postsynaptic currents (EPSCs). However, TRPV1+ terminals release additional glutamate from a unique, TRPV1-operated vesicle pool that is temperature sensitive and facilitated by ST activity to generate asynchronous EPSCs. This study tested whether presynaptic ?-aminobutyric acid (GABA)(B) receptors inhibit both the evoked and TRPV1-operated release mechanisms on second-order ST nucleus neurons. In horizontal slices, shocks activated single ST axons and evoked the time-invariant (latency jitter <200 ?s), glutamatergic EPSCs, which identified second-order neurons. Gabazine eliminated GABA(A) responses in all recordings. The GABA(B) agonist baclofen inhibited the amplitude of ST-EPSCs from both TRPV1+ and TRPV1- afferents with a similar EC(50) (?1.2 ?M). In TTX, GABA(B) activation decreased miniature EPSC (mEPSC) rates but not amplitudes, suggesting presynaptic actions downstream from terminal excitability. With calcium entry through voltage-activated calcium channels blocked by cadmium, baclofen reduced mEPSC frequency, indicating that GABA(B) reduced vesicle release by TRPV1-dependent calcium entry. GABA(B) activation also reduced temperature-evoked increases in mEPSC frequency, which relies on TRPV1. Our studies indicate that GABA(B) G protein-coupled receptors are uniformly distributed across all ST primary afferent terminals and act at multiple stages of the excitation-release cascades to suppress both action potential-triggered and TRPV1-coupled glutamate transmission pathways. Moreover, the segregated release cascades within TRPV1+ ST primary afferents represent independent, potential targets for differential modulation. PMID:21734101

Fawley, Jessica A; Peters, James H; Andresen, Michael C



P2Y1 receptor inhibits GABA transport through a calcium signalling-dependent mechanism in rat cortical astrocytes.  


Astrocytes express a variety of purinergic (P2) receptors, involved in astrocytic communication through fast increases in [Ca(2+) ]i . Of these, the metabotropic ATP receptors (P2Y) regulate cytoplasmic Ca(2+) levels through the PLC-PKC pathway. GABA transporters are a substrate for a number of Ca(2+) -related kinases, raising the possibility that calcium signalling in astrocytes impact the control of extracellular levels of the major inhibitory transmitter in the brain. To access this possibility we tested the influence of P2Y receptors upon GABA transport into astrocytes. Mature primary cortical astroglial-enriched cultures expressed functional P2Y receptors, as evaluated through Ca(2+) imaging, being P2Y1 the predominant P2Y receptor subtype. ATP (100 ?M, for 1 min) caused an inhibition of GABA transport through either GAT-1 or GAT-3 transporters, decreasing the Vmax kinetic constant. ATP-induced inhibition of GATs activity was still evident in the presence of adenosine deaminase, precluding an adenosine-mediated effect. This, was mimicked by a specific agonist for the P2Y1,12,13 receptor (2-MeSADP). The effect of 2-MeSADP on GABA transport was blocked by the P2 (PPADS) and P2Y1 selective (MRS2179) receptor antagonists, as well as by the PLC inhibitor (U73122). 2-MeSADP failed to inhibit GABA transport in astrocytes where intracellular calcium had been chelated (BAPTA-AM) or where calcium stores were depleted (?-cyclopiazonic acid, CPA). In conclusion, P2Y1 receptors in astrocytes inhibit GABA transport through a mechanism dependent of P2Y1 -mediated calcium signalling, suggesting that astrocytic calcium signalling, which occurs as a consequence of neuronal firing, may operate a negative feedback loop to enhance extracellular levels of GABA. GLIA 2014;62:1211-1226. PMID:24733747

Jacob, Pedro F; Vaz, Sandra H; Ribeiro, Joaquim A; Sebastião, Ana M



Pathophysiology and Pharmacology of GABA A Receptors  

Microsoft Academic Search

By controlling spike timing and sculpting neuronal rhythms, inhibitory interneurons play a key role in brain function. GABAergic\\u000a interneurons are highly diverse. The respective GABAA receptor subtypes, therefore, provide new opportunities not only for understanding GABA-dependent pathophysiologies but also\\u000a for targeting of selective neuronal circuits by drugs. The pharmacological relevance of GABAA receptor subtypes is increasingly being recognized. A new

H. Möhler; J.-M. Fritschy; K. Vogt; F. Crestani; U. Rudolph


Cocaine disinhibits dopamine neurons in the ventral tegmental area via use-dependent blockade of GABA neuron voltage-sensitive sodium channels  

PubMed Central

The aim of this study was to evaluate the effects of cocaine on ?-aminobutyric acid (GABA) and dopamine (DA) neurons in the ventral tegmental area (VTA). Utilizing single-unit recordings in vivo, microelectrophoretic administration of DA enhanced the firing rate of VTA GABA neurons via D2/D3 DA receptor activation. Lower doses of intravenous cocaine (0.25–0.5 mg/kg), or the DA transporter (DAT) blocker methamphetamine, enhanced VTA GABA neuron firing rate via D2/D3 receptor activation. Higher doses of cocaine (1.0–2.0 mg/kg) inhibited their firing rate, which was not sensitive to the D2/D3 antagonist eticlopride. The voltage-sensitive sodium channel (VSSC) blocker lidocaine inhibited the firing rate of VTA GABA neurons at all doses tested (0.25–2.0 mg/kg). Cocaine or lidocaine reduced VTA GABA neuron spike discharges induced by stimulation of the internal capsule (ICPSDs) at dose levels 0.25–2 mg/kg (IC50 1.2 mg/kg). There was no effect of DA or methamphetamine on ICPSDs, or of DA antagonists on cocaine inhibition of ICPSDs. In VTA GABA neurons in vitro, cocaine reduced (IC50 13 ?m) current-evoked spikes and TTX-sensitive sodium currents in a use-dependent manner. In VTA DA neurons, cocaine reduced IPSCs (IC50 13 ?m), increased IPSC paired-pulse facilitation and decreased spontaneous IPSC frequency, without affecting miniature IPSC frequency or amplitude. These findings suggest that cocaine acts on GABA neurons to reduce activity-dependent GABA release on DA neurons in the VTA, and that cocaine's use-dependent blockade of VTA GABA neuron VSSCs may synergize with its DAT inhibiting properties to enhance mesolimbic DA transmission implicated in cocaine reinforcement.

Steffensen, Scott C.; Taylor, Seth R.; Horton, Malia L.; Barber, Elise N.; Lyle, Laura T.; Stobbs, Sarah H.; Allison, David W.



Molecular and pharmacological evidence for a facilitatory functional role of pre-synaptic GLUK2/3 kainate receptors on GABA release in rat trigeminal caudal nucleus  

PubMed Central

Background Gamma-aminobutyric acid (GABA) and glutamate (GLU) are involved in nociceptive signals processing in the trigeminal system. In this study, we investigated the influence of excitatory transmission on GABA release in nerve terminals isolated from the rat trigeminal caudal nucleus (TCN). Methods We utilize biochemical (superfused synaptosomes loaded with [3H]GABA) and morphological (immunofluorescence experiments with specific antibody) techniques. Results Our results show that GLU potentiates the release of [3H]GABA evoked by 9, 15 and 30 mM [K+]e; 15 mM [K+]e-evoked [3H]GABA release was also reinforced by domoate and kainate (KA), two naturally occurring GLU-receptor agonists. The enhancement of 15 mM [K+]e-evoked [3H]GABA release produced by 100 ?M KA was abolished by NBQX, a mixed AMPA/KA receptor antagonist, but was not affected by GYKI52466, a selective AMPA receptor antagonist. ATPA, a selective agonist for KA receptors containing the GLUK1 subunit, had no effect on depolarization-induced [3H]GABA release, and UBP310, which selectively antagonizes these same receptors, failed to reverse the KA-induced potentiation of 15 mM [K+]e-evoked [3H]GABA release. The KA-induced potentiation was also unaffected by concanavalin A (10 ?M), a positive allosteric modulator of GLUK1- and GLUK2-containing KA receptors. Immunofluorescence experiments revealed that GABAergic nerve terminals in the TCN differentially expressed GLUK subunits, with GLUK2/3-positive terminals being twice more abundant than GLUK1-containing synaptosomes. Conclusions These findings indicate that pre-synaptic KA receptors facilitating GABA release from TCN nerve terminals mainly express GLUK2/GLUK3 subunits, supporting the notion that different types of KA receptors are involved in the various stages of pain transmission.

Samengo, I; Curro, D; Navarra, P; Barrese, V; Taglialatela, M; Martire, M



Antisense oligonucleotide to GABA A receptor ?2 subunit induces loss of neurones in rat hippocampus  

Microsoft Academic Search

The binding site for 1,4-benzodiazepines in the brain is part of the hetero-oligomeric ?-aminobutyric acid (GABA)A receptor complex which regulates a chloride ion channel. The presence of the ?2 subunit in the complex is necessary for the binding of benzodiazepines to their binding site. This study demonstrates a reduction of benzodiazepine receptor radioligand binding by 43% compared to control following

Jesper Karle; Michael-Robin Witt; Mogens Nielsen



Generation of recombinant guinea pig antibody fragments to the human GABA C receptor  

Microsoft Academic Search

To generate monoclonal antibodies to the human ?1 GABAC receptor, a ligand-gated chloride ion channel that is activated by the neurotransmitter ?-aminobutyric acid (GABA), we recovered the immunoglobulin variable heavy chain (VH) and light chain (VL) regions of a guinea pig immunized with a 14-mer peptide segment of the N-terminal extracellular domain of the ?1 subunit. Oligonucleotide primers were designed

Adnan Memic; Veronica V. Volgina; Hélène A. Gussin; David R. Pepperberg; Brian K. Kay



The Depolarizing Action of GABA Controls Early Network Activity in the Developing Hippocampus  

Microsoft Academic Search

Early in postnatal life ?-aminobutyric acid (GABA), the primary inhibitory transmitter in adults, excites targeted neurons\\u000a by an outwardly directed flux of chloride which results from the unbalance between the cation–chloride cotransporters NKCC1\\u000a and KCC2, involved in chloride uptake and extrusion, respectively. This effect contributes to generate synchronized network\\u000a activity or giant depolarizing potentials (GDPs) in the developing hippocampus. Here,

Enrico Cherubini; Marilena Griguoli; Victoria Safiulina; Laura Lagostena



GABA(A) receptor chloride channels are involved in the neuroprotective role of GABA following oxygen and glucose deprivation in the rat cerebral cortex but not in the hippocampus.  


Assays on "ex vivo" sections of rat hippocampus and rat cerebral cortex, subjected to oxygen and glucose deprivation (OGD) and a three-hour reperfusion-like (RL) recovery, were performed in the presence of either GABA or the GABA(A) receptor binding site antagonist, bicuculline. Lactate dehydrogenase (LDH) and propidium iodide were used to quantify cell mortality. We also measured, using real-time quantitative polymerase chain reaction (qPCR), the early transcriptional response of a number of genes of the glutamatergic and GABAergic systems. Specifically, glial pre- and post-synaptic glutamatergic transporters (namely GLAST1a, EAAC-1, GLT-1 and VGLUT1), three GABAA receptor subunits (?1, ?2 and ?2), and the GABAergic presynaptic marker, glutamic acid decarboxylase (GAD65), were studied. Mortality assays revealed that GABAA receptor chloride channels play an important role in the neuroprotective effect of GABA in the cerebral cortex, but have a much smaller effect in the hippocampus. We also found that GABA reverses the OGD-dependent decrease in GABA(A) receptor transcript levels, as well as mRNA levels of the membrane and vesicular glutamate transporter genes. Based on the markers used, we conclude that OGD results in differential responses in the GABAergic presynaptic and postsynaptic systems. PMID:23969196

Llorente, Irene L; Perez-Rodriguez, Diego; Martínez-Villayandre, Beatriz; Dos-Anjos, Severiano; Darlison, Mark G; Poole, Amy V; Fernández-López, Arsenio



Conserved Regional Patterns of GABA-Related Transcript Expression in the Neocortex of Subjects With Schizophrenia  

PubMed Central

Objective Individuals with schizophrenia exhibit disturbances in a number of cognitive, affective, sensory, and motor functions that depend on the circuitry of different cortical areas. The cognitive deficits associated with dysfunction of the dorsolateral prefrontal cortex result, at least in part, from abnormalities in GABA neurotransmission, as reflected in a specific pattern of altered expression of GABA-related genes. Consequently, the authors sought to determine whether this pattern of altered gene expression is restricted to the dorsolateral prefrontal cortex or could also contribute to the dysfunction of other cortical areas in subjects with schizophrenia. Method Real-time quantitative polymerase chain reaction was used to assess the levels of eight GABA-related transcripts in four cortical areas (dorsolateral prefrontal cortex, anterior cingulate cortex, and primary motor and primary visual cortices) of subjects (N=12) with schizophrenia and matched normal comparison subjects. Results Expression levels of seven transcripts were lower in subjects with schizophrenia, with the magnitude of reduction for each transcript comparable across the four areas. The largest reductions were detected for mRNA encoding somatostatin and parvalbumin, followed by moderate decreases in mRNA expression for the 67-kilodalton isoform of glutamic acid decarboxylase, the GABA membrane transporter GAT-1, and the ?1 and ? subunits of GABAA receptors. In contrast, the expression of calretinin mRNA did not differ between the subject groups in any of the four areas. Conclusions Because the areas examined represent the major functional domains (e.g., association, limbic, motor, and sensory) of the cerebral cortex, our findings suggest that a conserved set of molecular alterations affecting GABA neurotransmission contribute to the pathophysiology of different clinical features of schizophrenia.

Hashimoto, Takanori; Bazmi, H. Holly; Mirnics, Karoly; Wu, Qiang; Sampson, Allan R.; Lewis, David A.



Two-photon uncaging of ?-aminobutyric acid in intact brain tissue  

PubMed Central

We have synthesized a photosensitive (or caged) 4-carboxymethoxy-5,7-dinitroindolinyl (CDNI) derivative of ?-aminobutyric acid (GABA). Two-photon excitation of CDNI-GABA produced rapid activation of GABAergic currents in neurons in brain slices with an axial resolution of approximately 2 micrometers, and enabled high-resolution functional mapping of GABA-A receptors. Two-photon uncaging of GABA, the major inhibitory neurotransmitter, should allow detailed studies of receptor function and synaptic integration with subcellular precision.

Hayama, Tatsuya; Kasai, Haruo



The muscle relaxant thiocolchicoside is an antagonist of GABA A receptor function in the central nervous system  

Microsoft Academic Search

Thiocolchicoside (TCC) is used clinically for its muscle relaxant, anti-inflammatory, and analgesic properties, and it has been shown to interact with ?-aminobutyric acid (GABA) type A receptors (GABAARs) and strychnine-sensitive glycine receptors in the rat central nervous system. In contrast to a proposed agonistic action at these two types of inhibitory receptors, pharmacological evidence has shown that, under certain conditions,

Mario Carta; Luca Murru; Paolo Botta; Giuseppe Talani; GianPietro Sechi; PierLuigi De Riu; Enrico Sanna; Giovanni Biggio



Quantitative Effects of GABA and Bicuculline Meth on Receptive Field Properties of Neurons in Real and Simulated Whisker Barrels  

Microsoft Academic Search

simulated neurons, they also possess GABAB receptors, which are unaffected by BMI. 1. Carbon fiber multibarrel glass microelectrodes were used to 8. We conclude that the inhibitory receptive field properties of record extracellular single-unit activity during microiontophoretic barrel neurons can be explained by intrabarrel inhibition and that application of y-aminobutyric acid (GABA) or bicuculline methio- the expansion of receptive field



Histamine H 1 receptor activation stimulates [ 3H]GABA release from human astrocytoma U373 MG cells  

Microsoft Academic Search

In U373 MG cells, a line derived from a human astrocytoma, histamine stimulated the release of [3H]?-aminobutyric acid ([3H]GABA) in a concentration-dependent manner (286±23% of basal release at 1 mM histamine). Neither Ca2+ removal nor Cd2+ (100 ?M) affected [3H]GABA release evoked by 100 ?M histamine but the response was significantly reduced by 10 ?M U-73122 ({1-[6-((17?-3-methoxyestra-1,3,5(10)-trien-17-yl)-amino)-hexyl]-1H-pyrrole-2,5-dione}), an inhibitor of

Luis-Enrique Soria-Jasso; José-Antonio Arias-Montaño



Effects of valproate and other antiepileptic drugs on brain glutamate, glutamine, and GABA in patients with refractory complex partial seizures.  


Preclinical studies suggested valproate increased brain gamma-aminobutyric acid (GABA) with no major effects on brain glutamate or glutamine. Valproate increased human cerebrospinal fluid GABA and glutamine in some studies; others reported no effect. In vivo measurements of glutamate, glutamine, and GABA were made of a 14 cm3volume in the occipital cortex using a1H spectroscopy with a 2.1 Tesla magnetic resonance spectrometer and an 8 cm surface coil. Ten control subjects and 14 patients with refractory complex partial seizures were examined. Brain glutamine concentrations were above normal in three of five patients taking valproate and two of nine taking carbamazepine or phenytoin. Mean glutamine levels of patients taking valproate were higher than control subjects and patients taking carbamazepine or phenytoin. Brain glutamate concentrations were above normal in four of nine patients taking phenytoin or carbamazepine and two of five taking valproate. Brain GABA levels were below normal in four of nine patients taking carbamazepine or phenytoin and one of five taking valproate. Above normal glutamate or below normal GABA was present in nine of 14 patients and may contribute to their refractory epilepsy. Increased brain glutamine associated with valproate therapy may reflect mild hyperammonemia. PMID:10222306

Petroff, O A; Rothman, D L; Behar, K L; Hyder, F; Mattson, R H



Diazepam fails to potentiate GABA-induced chloride uptake and to produce anxiolytic-like action in aged rats.  


The pharmacological response to benzodiazepines has been demonstrated to be different in aged individuals in comparison to adults. We studied the age-dependent changes in some of the in vitro and behavioral effects of diazepam in aged (24 months old) rats, comparing them to adults (3 months old). We evaluated the in vitro gamma-aminobutyric acid (GABA)-induced 36Cl- uptake and the diazepam potentiation of GABA-stimulated 36Cl- uptake in microsacs from cerebral cortex of both groups of animals. We found no differences in the GABA-stimulated 36Cl- uptake between adult and aged animals, and diazepam failed to potentiate GABA-induced 36Cl- flux in the aged cortical microsacs. We also examined the effect of 0.03-10 mg of diazepam on locomotor activity in an open-field test and the anxiolytic-like action of diazepam in doses ranging from 0.03 to 1 in a dark-light transition test. We observed no anxiolytic-like action of the drug in the dark-light transition test in the aged rats, while there was a shift to the left in the diminution of locomotor activity evaluated by the open-field test. We conclude that the pharmacodynamic changes observed in cortical GABA(A) receptors in aged rats could partially explain the lack of anxiolytic-like action but not the oversedation evidenced in this group of animals. PMID:11526969

Wikinski, S I; Acosta, G B; Gravielle, M C; Bonavita, C D; Bisagno, V; Fiszer de Plazas, S; Rubio, M C



Release of (3H)GABA formed from (3H)glutamate in rat hippocampal slices: comparison with endogenous and exogenous labeled GABA  

SciTech Connect

To compare the storage and release of endogenous GABA, of (/sup 3/H)GABA formed endogenously from glutamate, and of exogenous (/sup 14/C)GABA, hippocampal slices were incubated with 5 microCi/ml (3,4-/sup 3/H)1-glutamate and 0.5 microCi/ml (U-/sup 14/C)GABA and then were superfused in the presence or absence of Ca/sup +/ with either 50 mM K/sup +/ or 50 microM veratridine. Exogenous (/sup 14/C)GABA content of the slices declined spontaneously while endogenous GABA and endogenously formed (/sup 3/H)GABA stayed constant over a 48 min period. In the presence of Ca/sup +/ 50 mM K/sup +/ and in the presence or absence of Ca2/sup +/ veratridine released exogenous (/sup 14/C)GABA more rapidly than endogenous or endogenously formed (/sup 3/H)GABA, the release of the latter two occurring always in parallel. The initial specific activity of released exogenous (/sup 14/C)GABA was three times, while that of endogenously formed (/sup 3/H)GABA was only 50% higher than that in the slices. The observation that endogenous GABA and (/sup 3/H)GABA formed endogenously from glutamate are stored and released in parallel but differently from exogenous labelled GABA, suggests that exogenous (/sup 3/H) glutamate can enter a glutamate pool that normally serves as precursor of GABA.

Szerb, J.C.



Conformation of the neurotransmitter ?-aminobutyric acid in liquid water.  


We study the conformation and reorientation dynamics of the inhibitory neurotransmitter ?-aminobutyric acid (GABA) under neutral and acidic conditions using a combination of broadband dielectric relaxation spectroscopy and polarization-resolved femtosecond mid-infrared pump-probe spectroscopy. We find that both zwitterionic and cationic GABA adopt nearly linear conformations in aqueous solution, meaning that the two charged functional groups of the GABA zwitterion are hydrated separately. PMID:24770326

Ottosson, N; Pastorczak, M; van der Post, Sietse T; Bakker, Huib J



Co-release of acetylcholine and gamma-aminobutyric acid by a retinal neuron  

SciTech Connect

Rabbit retinas were vitally stained with 4',6-diamidino-2-phenylindole (DAPI), a fluorescent compound that selectively accumulates within the cholinergic amacrine cells. The retinas were then incubated in vitro in the presence of radioactive gamma-aminobutyric acid (GABA) and autoradiographed. The cells that accumulated DAPI were found to accumulate GABA, confirming immunohistochemical evidence that the cholinergic amacrine cells contain GABA. Incubation of retinas in the presence of elevated concentrations of K+ caused them to release acetylcholine and GABA, and autoradiography showed depletion of radioactive GABA from the cholinergic amacrine cells. This indicates that the cholinergic amacrine cells can secrete acetylcholine and GABA. Retinas were double-labeled with (14C)GABA and (3H)acetylcholine, allowing simultaneous measurement of their release. The release of (14C)GABA was found to be independent of extracellular Ca2+. Radioactive GABA synthesized endogenously from (14C)glutamate behaved the same way as radioactive GABA accumulated from the medium. In the same experiments the simultaneously measured release of (3H)acetylcholine was strongly Ca2+-dependent, indicating that the releases of acetylcholine and GABA are controlled by different mechanisms. Synaptic vesicles immunologically isolated from double-labeled retinas contained much (3H)acetylcholine and little or no (14C)GABA. These results suggest that the cholinergic amacrine cells release acetylcholine primarily by vesicle exocytosis and release GABA primarily by means of a carrier.

O'Malley, D.M.; Masland, R.H.



Medications acting on the GABA system in the treatment of alcoholic patients.  


Gamma aminobutyric acid (GABA) represents the major inhibitory neurotransmitter of the central nervous system. Ethanol as well as benzodiazepines (BDZs) and some anticonvulsant drugs directly affect GABAA receptors inducing similar anxiolytic, sedativehypnotic, and anticonvulsant effects. Since BDZs have proven their efficacy in ameliorating symptoms and in decreasing the risk of seizures and delirium tremens, they are the drugs of choice for the treatment of alcohol withdrawal syndrome (AWS). However, due to their addictive potential and lack of safety when combined with alcohol, BDZs are usually not recommended for the maintenance of alcohol abstinence. Other GABA-ergic medications represent potentially promising drugs useful in the treatment of AWS and in maintaining alcohol abstinence. Indeed, available studies have demonstrated that clomethiazole, gabapentin and gamma hydroxybutyrate (GHB) present a similar efficacy to BDZs in suppressing AWS. In addition, current evidence also indicates that gabapentin and GHB do not have significant interactions with ethanol that render them safe to use in maintaining alcohol abstinence. Moreover, gabapentin and valproic acid may be beneficial in maintaining alcohol abstinence in alcoholics with psychiatric co-morbidity. Pregabalin, neurosteroids, tiagabine, and vigabatrin need further clinical evidence of efficacy, safety and tolerability. Thus, given the importance of GABA-ergic mechanisms in the development and maintenance of alcohol dependence, and the very interesting results currently achieved, more research on GABAergic agents is warranted. PMID:20482512

Caputo, Fabio; Bernardi, Mauro



Release of GABA and activation of GABA(A) in the spinal cord mediates the effects of TENS in rats.  


Transcutaneous electrical nerve stimulation (TENS) is a commonly utilized non-pharmacological, non-invasive treatment for pain. GABA is a neurotransmitter in the dorsal horn of the spinal cord that mediates analgesia locally, and also through activation of supraspinal sites. TENS reduces hyperalgesia through activation of receptor-mediated pathways at the level of the spinal cord, and supraspinally. The current study tested the hypothesis that either high or low frequency TENS applied to the inflamed knee joint increases GABA in the spinal cord dorsal horn and activates GABA receptors spinally. We utilized microdialysis to sample the extracellular fluid before, during and after TENS and analyzed GABA in dialysates with high performance liquid chromatography. We analyzed the extracellular GABA concentrations in animals with and without knee joint inflammation induced by intra-articular injection of kaolin and carrageenan. We further tested if spinal blockade of GABA receptors prevents the antihyperalgesia produced by TENS in rats with joint inflammation. We show that high frequency TENS increases extracellular GABA concentrations in the spinal cord in animals with and without joint inflammation. The increases in GABA do not occur in response to low frequency TENS, and there are no increases in glycine in response to low or high frequency TENS. However, the reduction in primary hyperalgesia by both high and low frequency TENS is prevented by spinal blockade of GABA(A) receptors with bicuculline. Thus, high frequency TENS increases release of GABA in the deep dorsal horn of the spinal cord, and both high and low frequency TENS reduce primary hyperalgesia by activation of GABA(A) receptors spinally. PMID:17234163

Maeda, Y; Lisi, T L; Vance, C G T; Sluka, K A



Assignment of the human GABA transporter gene (GABATHG) locus to chromosome 3p24-p25  

SciTech Connect

An essential regulatory process of synaptic transmission is the inactivation of released neurotransmitters by the transmitter-specific uptake mechanism, {gamma}-Aminobutyric acid (GABA) is an inhibitory transmitter in the vertebrate central nervous system; its activity is terminated by a high-affinity Na{sup +} and Cl{sup -} -dependent specific GABA transporter (GAT), which carries the neurotransmitter to the presynaptic neuron and/or glial elements surrounding the synaptic cleft. Deficiency of the transporter may cause epilepsy and some other nervous diseases. The human GAT gene (GABATHG), approximately 25 kb in length, has been cloned and sequenced by our colleagues (7). Here the results of the in situ hybridization mapping with the gene are presented. 10 refs., 1 fig.

Huang, Fang; Fei, Jian; Guo, Li-He [Shanghai Institute of Cell Biology, Shanghai (China)] [and others] [Shanghai Institute of Cell Biology, Shanghai (China); and others



Iontophoretic studies on rat hippocampus with some novel GABA antagonists.  


Twelve substances which appear to be GABA antagonists, judging by their ability to reverse the inhibitory effect of GABA on 35S-TBPS binding to rat brain membranes, were tested iontophoretically on population spikes in the rat hippocampus. Eight of them, including seven which completely reversed the inhibitory action of GABA on 35S-TBPS binding, caused a marked enhancement of population spikes, with slow onset and long duration and they antagonized the inhibition of population spikes by GABA. These effects were similar to those produced by bicuculline. Electrophysiologically, the most potent of the "complete reversers" were bathophenanthroline disulfonate and brucine. In vitro, amoxapine and brucine most effectively reversed the inhibitory action of GABA on 35S-TBPS binding. Of the five substances which only partly reversed the inhibitory effect of GABA on 35S-TBPS binding, four depressed the population spikes and potentiated the inhibitory action of GABA. The fifth "partial reverser", pipazethate, potently increased the population spikes, like the "complete reversers". Although other interpretations are possible the results are consistent with the existence of several GABA-A receptor types in brain, only some of which are blocked by certain partial reversers. PMID:2874465

Dalkara, T; Saederup, E; Squires, R F; Krnjevic, K



Gonadal hormones alter hypothalamic GABA and glutamate levels  

Microsoft Academic Search

GABA and glutamate levels were measured in brain sites important for lordotic responding and in other hypothalamic sites after gonadal hormone treatments sufficient to activate lordosis. Estradiol increased GABA and glutamate in the ventromedial nucleus and the vertical diagonal bands. Progesterone administration to estradiol primed females led to a rapid decline of the transmitters in these areas. Results are discussed

Victoria N Luine; David R Grattan; Michael Selmanoff



Effect of green tea rich in ?-aminobutyric acid on blood pressure of Dahl salt-sensitive rats  

Microsoft Academic Search

?-Aminobutyric acid (GABA) is known to be involved in the regulation of blood pressure by modulating the neurotransmitter release in the central and peripheral sympathetic nervous systems. This study investigated the antihypertensive effect of green tea rich in GABA (GABA-rich tea) in young and old Dahl salt-sensitive (S) rats. GABA-rich tea was made by fermenting fresh green tea leaves under

Yasuhiko Abe; Satoshi Umemura; Koh-ichi Sugimoto; Nobuhito Hirawa; Yoshio Kato; Nobuyuki Yokoyama; Tomoko Yokoyama; Junichi Iwai; Masao Ishii



Participation of GABAA, GABA(B) receptors and neurosteroids in toluene-induced hypothermia: evidence of concentration-dependent differences in the mechanism of action.  


Toluene is a misused substance that modifies ?-aminobutyric acid (GABA) release and shares behavioral and molecular effects with GABA(A) and GABA(B) receptor agonists. GABAergic compounds are involved in thermoregulation processes and volatile substance users have reported that one of the reasons to inhale is to avoid feeling cold. At present, no studies have analyzed the effects of inhalants on body temperature and the mechanism of action involved. Thus, the main purpose of this study was to evaluate the effects of a (60 min) acute toluene inhalation (2000, 4000 and 6000 ppm) in core temperature. In addition, we tried to prevent the changes of temperature induced by toluene with the specific GABA(A) receptor blockers picrotoxin (0.01-0.1mg/kg), bicuculline (0.1-0.3mg/kg), and flumazenil (3-30 mg/kg); the GABA(B) receptor antagonist phaclofen (10-30 mg/kg) and the neurosteroid synthesis inhibitor finasteride (10-30 mg/kg). Results show that toluene reduced core temperature in mice in a concentration-dependent manner. The hypothermia produced by 4000 ppm toluene was prevented by picrotoxin, bicuculline, phaclofen and finasteride but not by flumazenil. In contrast none of these antagonists tested blocked the effects of 6000 ppm toluene. In conclusion, toluene decreases core temperature, GABA receptors and neurosteroids participate in toluene's action at 4000 ppm; but other mechanisms of action are involved in the hypothermic effects of 6000 ppm toluene. PMID:23085024

Paez-Martinez, Nayeli; Aldrete-Audiffred, Jorge; Gallardo-Tenorio, Alfredo; Castro-Garcia, Mario; Estrada-Camarena, Erika; Lopez-Rubalcava, Carolina



Neuroprotection of ethanol against ischemia/reperfusion-induced brain injury through decreasing c-Jun N-terminal kinase 3 (JNK3) activation by enhancing GABA release.  


Our latest study indicated that ethanol could attenuate cerebral ischemia/reperfusion-induced brain injury through activating Ionotropic glutamate receptors Kainate Family (Gluk1)-kainate (KA) receptors and gamma-aminobutyric acid (GABA) receptors. However, the possible mechanism of the neuroprotective effects of ethanol remains unclear. In this study we report that ethanol shows neuroprotective effects against ischemic brain injury through enhancing GABA release and then decreasing c-Jun N-terminal kinase 3 (JNK3) activation. Electrophysiologic recording indicated that ethanol enhances GABA release from presynaptic neurons and the released GABA subsequently inhibits the KA receptor-mediated whole-cell currents. Moreover, our data show that ethanol can inhibit the increased assembly of the Gluk2-PSD-95-MLK3 (postsynaptic density protein-95, PSD-95 and mixed-lineage kinase 3, MLK3) module induced by cerebral ischemia and the activation of the MLK3-MKK4/7-JNK (mitogen-activated protein kinase kinase 4/7, MKK4/7) cascade. Pretreatment of the GABA(A) receptor antagonist bicuculline and antagonist of VGCC (a broad-spectrum blocker of the voltage-gated calcium channel [VGCC]) Chromic (CdCl(2)) can demolish the neuroprotective effects of ethanol. The results suggest that during ischemia-reperfusion, ethanol may activate presynaptic Gluk1-KA and facilitate Ca(2+)-dependent GABA release. The released GABA activates postsynaptic GABA(A) receptors, which suppress the ischemic depolarization and decrease the association of signaling module Gluk2-PSD-95-MLK3 induced by the activation of postsynaptic Gluk2-KA receptors. There is a raised possibility that ethanol inhibiting the JNK3 apoptotic pathway (MLK3/MKK4/7/JNK3/c-Jun/Fas-L) performs a neuroprotective function against ischemic brain injury. PMID:20219637

Qi, S-H; Liu, Y; Hao, L-Y; Guan, Q-H; Gu, Y-H; Zhang, J; Yan, H; Wang, M; Zhang, G-Y



Allopregnanolone prevents dieldrin-induced NMDA receptor internalization and neurotoxicity by preserving GABA(A) receptor function.  


Dieldrin is an endocrine disruptor that accumulates in mammalian adipose tissue and brain. It induces convulsions due to its antagonism of the ?-aminobutyric acid A receptor (GABA(A)R). We have previously reported that long-term exposure to dieldrin causes the internalization of the N-methyl-D-aspartate receptor (NMDAR) as a result of persistent GABA(A)R inhibition. Because the neurosteroids 17?-estradiol (E2) and allopregnanolone are known to modulate the function and trafficking of GABA(A)R and NMDAR, we examined the effects of E2 and allopregnanolone on dieldrin-induced GABA(A)R inhibition, NMDAR internalization, and neuronal death in cortical neurons. We found that 1 nM E2 increased the membrane expression of NR1/NR2B receptors and postsynaptic density 95 but did not induce their physical association. In contrast, 10 nM E2 had no effect on these proteins but reduced NR2A membrane expression. We also found that exposure to 60 nM dieldrin for 6 d in vitro caused the internalization of NR1 and NR2B but not NR2A. Treatment with either 1 nM E2 or 10 ?M allopregnanolone prevented the dieldrin-induced reduction in membrane levels of the NR1/NR2B receptors. Furthermore, prolonged exposure to 200 nM dieldrin down-regulated the expression of NR2A; this was inhibited only by allopregnanolone. Although both hormones restored NMDAR function, as measured by the NMDA-induced rise in intracellular calcium, allopregnanolone (but not E2) reversed the inhibition of GABA(A)R and neuronal death caused by prolonged exposure to dieldrin. Our results indicate that allopregnanolone protects cortical neurons against the neurotoxicity caused by long-term exposure to dieldrin by maintaining GABA(A)R and NMDAR functionality. PMID:22166974

Briz, Víctor; Parkash, Jyoti; Sánchez-Redondo, Sara; Prevot, Vincent; Suñol, Cristina



Hypothalamic inhibition of neurones in the nucleus tractus solitarius of the cat is GABA mediated.  

PubMed Central

1. In pentobarbitone-anaesthetized cats extracellular activity of neurones in the vicinity of the nucleus tractus solitarius receiving inputs from the carotid sinus nerve (SN) and/or vagus nerve (VN) during stimulation of the hypothalamic defence area (HDA) and application of gamma-aminobutyric acid (GABA) and glycine and their antagonists have been studied. 2. A total of forty neurones have been tested, of which twenty-four only had an input from the SN, one only from the VN, twelve from both nerves and three had neither SN or VN inputs. 3. Short trains of stimuli to the HDA inhibited both the ongoing activity (if present) and evoked discharge in thirty-nine of the forty neurones tested. 4. In the forty cells tested ionophoretic application of GABA reduced (4) or totally inhibited (35) neuronal discharge whilst in the thirty-eight tested with glycine discharge was totally (25) or partially (12) suppressed. 5. Ionophoresis of bicuculline totally (14) or partially (6) antagonized the inhibitory actions of GABA in the twenty-five cells tested, and in eighteen of these the ongoing and/or evoked activity was simultaneously increased. In eighteen of the nineteen cells tested this level of bicuculline also antagonized the inhibitory actions of HDA stimuli whereas in none of the sixteen cells tested did it affect glycine-evoked inhibitions. 6. Ionophoretic application of strychnine antagonized the inhibitory effects of glycine in eight of nine cells tested but in these eight cells strychnine had no effect on ongoing or evoked discharges, GABA- or HDA-evoked inhibitions. 7. In a chloralose-anaesthetized cat five neurones receiving SN inputs (three also receiving VN inputs) were recorded. All could be inhibited by HDA stimuli and by application of GABA. In the three of four cells in which bicuculline antagonized GABA inhibitions, the effects of HDA stimuli were simultaneously antagonized whereas glycine-evoked inhibitions were unaffected. 8. In two neurones, in addition to inhibiting neuronal discharge HDA stimulation also evoked activity in the cells. In a further four neurones similar excitatory responses were uncovered when the HDA inhibitory effects were antagonized by bicuculline. 9. The importance of these observations in cardiovascular control and in the functioning of the baroreceptor reflex is discussed.

Jordan, D; Mifflin, S W; Spyer, K M



Inhibition of neuronal membrane GABAB receptor binding by GABA structural analogues.  


1. A number of compounds structurally related to GABA were tested as inhibitors of baclofen-sensitive GABAB receptor binding to membranes from mouse brain. 2. In addition to two known inhibitors--baclofen and 5-aminovaleric acid--two analogues were shown to possess inhibitory activity. These compounds were 4-aminobutyryl-DL-alanine hydrobromide (IC50 = 3 microM) and trans-2-(aminomethyl)cyclopropane carboxylic acid (IC50 = 90 microM). 3. Both drugs also exhibited affinity for GABAA binding sites. 4. Further experiments are needed to establish if these analogues exert agonist or antagonist action at the GABAB receptor. PMID:2832226

Tunnicliff, G; Rogier, C J; Youngs, T L



Morphological heterogeneity of the GABAergic network in the suprachiasmatic nucleus, the brain's circadian pacemaker  

PubMed Central

GABA (gamma-amino-butyric acid) is the predominant neurotransmitter in the mammalian suprachiasmatic nucleus (SCN), with a central role in circadian time-keeping. We therefore undertook an ultrastructural analysis of the GABA-containing innervation in the SCN of mice and rats using immunoperoxidase and immunogold procedures. GABA-immunoreactive (GABA-ir) neurons were identified by use of anti-GABA and anti-GAD (glutamic acid decarboxylase) antisera. The relationship between GABA-ir elements and the most prominent peptidergic neurons in the SCN, containing vasopressin-neurophysin (VP-NP) or vasoactive intestinal polypeptide (VIP), was also studied. Within any given field in the SCN, approximately 40–70% of the neuronal profiles were GABA-ir. In GABA-ir somata, immunogold particles were prominent over mitochondria, sparse over cytoplasm, and scattered as aggregates over nucleoplasm. In axonal boutons, gold particles were concentrated over electron-lucent synaptic vesicles (diameter 40–60 nm) and mitochondria, and in some instances over dense-cored vesicles (DCVs, diameter 90–110 nm). GABA-ir boutons formed either symmetric or asymmetric synaptic contacts with somata, dendritic shafts and spines, and occasionally with other terminals (axo-axonic). Homologous or autaptic connections (GABA on GABA, or GAD on GAD) were common. Although GABA appeared to predominate in most neuronal profiles, colocalisation of GABA within neurons that were predominantly neuropeptide-containing was also evident. About 66% of the VIP-containing boutons and 32% of the vasopressinergic boutons contained GABA. The dense and complex GABAergic network that pervades the SCN is therefore comprised of multiple neuronal phenotypes containing GABA, including a wide variety of axonal boutons that impinge on heterologous and homologous postsynaptic sites.




Competing pathways in the photo-Favorskii rearrangement and release of esters: Studies on fluorinated p-hydroxyphenacyl GABA and glutamate phototriggers  

PubMed Central

Three new trifluoromethylated p-hydroxyphenacyl (pHP) caged ?-aminobutyric acid (GABA) and glutamate (Glu) derivatives have been examined for their efficacy as photoremovable protecting groups in aqueous solution. By replacing hydrogen with fluorine, e.g., a m-trifluoromethyl or a m-trifluoromethoxy vs. m-methoxy substituents on the pHP chromophore, modest increases in the quantum yields for release of the amino acids GABA and glutamate were realized as well as improved lipophilicity. The pHP triplet undergoes a photo-Favorskii rearrangement with concomitant release of the amino acid substrate. Deprotonation competes with the rearrangement from the triplet excited state and yields the pHP conjugate base that, upon reprotonation, regenerate the starting ketoester, a chemically unproductive or “energy wasting” process. Employing picosecond pump–probe spectroscopy, GABA derivatives 2 – 5 are characterized by short triplet lifetimes, a manifestation of their rapid release of GABA. The bioavailability of released GABA at the GABAA receptor improved when the release took place from m-OCF3 (2) but decreased for m-CF3 (3) when compared with the parent pHP derivative. These studies demonstrate that pKa and lipophilicity exert significant but sometimes opposing influences on the photochemistry and biological activity of pHP phototriggers.

Stensrud, Kenneth; Noh, Jihyun; Kandler, Karl; Wirz, Jakob; Heger, Dominik



Modulation of 5-hydroxytryptamine-induced head-twitch response by drugs acting at GABA and related receptors.  

PubMed Central

The effects of drugs acting at the gamma-aminobutyric acid (GABA) receptors and other chloride ionophore-related sites have been studied for their ability to modulate the head-twitch induced by 1-5-hydroxytryptophan (5-HTP) in the mouse. The GABAa receptor agonists, muscimol, imidazoleacetic acid and 3-aminopropanesulphonic acid, produced a dose-related potentiation, while bicuculline inhibited the head-twitch. The GABAb receptor agonist, baclofen, produced dose-related inhibition. Diazepam potentiated the head-twitch while the 'inverse' benzodiazepine receptor agonist ethyl-beta-carboline-3-carboxylate inhibited the head-twitch. The antagonist Ro15-1788 also produced inhibition. Ro05-4864, a ligand for the benzodiazepine 'acceptor' site, potentiated the head-twitch. Pentobarbitone and pentylenetetrazol potentiated the 5-HTP-induced head-twitch at low doses, changing to inhibition as the dose was increased. Picrotoxin in subconvulsant doses, produced only potentiation. More than one site may be involved in the action of these substances. GABA, amino-oxyacetic acid and 1-2-4-diaminobutyric acid inhibited the head-twitch, while the GABA-depletor, 3-mercaptopropionic acid potentiated it. Of all the agents tested, only muscimol produced head-twitching when given alone. It was concluded that both GABAa and GABAb receptors modulate the head-twitch response to 5-HTP.

Handley, S. L.; Singh, L.



Basal expression and induction of glutamate decarboxylase and GABA in excitatory granule cells of the rat and monkey hippocampal dentate gyrus.  


The excitatory, glutamatergic granule cells of the hippocampal dentate gyrus are presumed to play central roles in normal learning and memory, and in the genesis of spontaneous seizure discharges that originate within the temporal lobe. In localizing the two GABA-producing forms of glutamate decarboxylase (GAD65 and GAD67) in the normal hippocampus as a prelude to experimental epilepsy studies, we unexpectedly discovered that, in addition to its presence in hippocampal nonprincipal cells, GAD67-like immunoreactivity (LI) was present in the excitatory axons (the mossy fibers) of normal dentate granule cells of rats, mice, and the monkey Macaca nemestrina. Using improved immunocytochemical methods, we were also able to detect GABA-LI in normal granule cell somata and processes. Conversely, GAD65-LI was undetectable in normal granule cells. Perforant pathway stimulation for 24 hours, which evoked population spikes and epileptiform discharges in both dentate granule cells and hippocampal pyramidal neurons, induced GAD65-, GAD67-, and GABA-LI only in granule cells. Despite prolonged excitation, normally GAD- and GABA-negative dentate hilar neurons and hippocampal pyramidal cells remained immunonegative. Induced granule cell GAD65-, GAD67-, and GABA-LI remained elevated above control immunoreactivity for at least 4 days after the end of stimulation. Pre-embedding immunocytochemical electron microscopy confirmed that GAD67- and GABA-LI were induced selectively within granule cells; granule cell layer glia and endothelial cells were GAD- and GABA-immunonegative. In situ hybridization after stimulation revealed a similarly selective induction of GAD65 and GAD67 mRNA in dentate granule cells. Neurochemical analysis of the microdissected dentate gyrus and area CA1 determined whether changes in GAD- and GABA-LI reflect changes in the concentrations of chemically identified GAD and GABA. Stimulation for 24 hours increased GAD67 and GABA concentrations sixfold in the dentate gyrus, and decreased the concentrations of the GABA precursors glutamate and glutamine. No significant change in GAD65 concentration was detected in the microdissected dentate gyrus despite the induction of GAD65-LI. The concentrations of GAD65, GAD67, GABA, glutamate and glutamine in area CA1 were not significantly different from control concentrations. These results indicate that dentate granule cells normally contain two "fast-acting" amino acid neurotransmitters, one excitatory and one inhibitory, and may therefore produce both excitatory and inhibitory effects. Although the physiological role of granule cell GABA is unknown, the discovery of both basal and activity-dependent GAD and GABA expression in glutamatergic dentate granule cells may have fundamental implications for physiological plasticity presumed to underlie normal learning and memory. Furthermore, the induction of granule cell GAD and GABA by afferent excitation may constitute a mechanism by which epileptic seizures trigger compensatory interictal network inhibition or GABA-mediated neurotrophic effects. PMID:8889946

Sloviter, R S; Dichter, M A; Rachinsky, T L; Dean, E; Goodman, J H; Sollas, A L; Martin, D L



Seed-specific expression of truncated OsGAD2 produces GABA-enriched rice grains that influence a decrease in blood pressure in spontaneously hypertensive rats  

Microsoft Academic Search

Gamma-aminobutyric acid (GABA) is a four-carbon amino acid that is commonly present in living organisms and functions as a\\u000a major inhibitory neurotransmitter in mammals. It is understood to have a potentially anti-hypertensive effect in mammals.\\u000a GABA is synthesized from glutamate by glutamate decarboxylase (GAD). In plants, GAD is regulated via its calmodulin-binding\\u000a domain (CaMBD) by Ca2+\\/CaM. We have previously reported

Kazuhito Akama; Junko Kanetou; Shunsuke Shimosaki; Kouhei Kawakami; Satoru Tsuchikura; Fumio Takaiwa



Beyond inhibition: GABA synapses tune the neuroendocrine stress axis.  


We recently described a novel form of stress-associated bidirectional plasticity at GABA synapses onto hypothalamic parvocellular neuroendocrine cells (PNCs), the apex of the hypothalamus-pituitary-adrenal axis. This plasticity may contribute to neuroendocrine adaptation. However, this GABA synapse plasticity likely does not translate into a simple more and less of inhibition because the ionic driving force for Cl(-) , the primary charge carrier for GABAA receptors, is dynamic. Specifically, stress impairs a Cl(-) extrusion mechanism in PNCs. This not only renders the steady-state GABA response less hyperpolarizing but also makes PNCs susceptible to the activity-dependent accumulation of Cl(-) . Accordingly, GABA synapse plasticity impacts both the robustness of GABA voltage response and dynamic Cl(-) loading, imposing nonlinear influences on PNC excitability during circuit activities. This theoretical consideration predicts roles for GABA transmission far more versatile than canonical inhibition. We propose potential impacts of GABA synapse plasticity on the experience-dependent fine-tuning of neuroendocrine stress responses. PMID:24648386

Inoue, Wataru; Bains, Jaideep S



Downregulation of tonic GABA currents following epileptogenic stimulation of rat hippocampal cultures  

PubMed Central

Deficits in GABAergic inhibitory transmission are a hallmark of temporal lobe epilepsy and have been replicated in animal and tissue culture models of epilepsy. GABAergic inhibition comprises phasic and tonic inhibition that is mediated by synaptic and extrasynaptic GABAA receptors, respectively. We have recently demonstrated that chronic stimulation with cyclothiazide (CTZ) or kainic acid (KA) induces robust epileptiform activity in hippocampal neurons both in vitro and in vivo. Here, we report a downregulation of tonic GABA inhibition after chronic epileptogenic stimulation of rat hippocampal cultures. Chronic pretreatment of hippocampal neurons with CTZ or KA resulted in a marked reduction in GABAergic inhibition, as shown by a significant decrease in whole-cell GABA currents and in the frequency of miniature inhibitory postsynaptic currents (mIPSCs). Interestingly, synaptically localized GABAA receptors remained relatively stable, as evidenced by the unaltered amplitude of mIPSCs, as well as the unchanged punctate immunoreactivity of ?2 subunit-containing postsynaptic GABAA receptors. In contrast, tonic GABA currents, assessed either by a GABAA receptor antagonist bicuculline or a selective extrasynaptic GABAA receptor agonist THIP, were significantly reduced following epileptogenic stimulation. These results reveal a novel form of neural plasticity, that epileptogenic stimulation can selectively downregulate extrasynaptic GABAA receptors while leaving synaptic GABAA receptors unchanged. Thus, in addition to synaptic alteration of GABAergic transmission, regulation of tonic inhibition may also play an important role during epileptogenesis.

Qi, Jin-shun; Yao, Jun; Fang, Cheng; Luscher, Bernhard; Chen, Gong



Immunocytochemical Localization of Amines and GABA in the Optic Lobe of the Butterfly, Papilio xuthus  

PubMed Central

Butterflies have sophisticated color vision. While the spectral organization of the compound eye has been well characterized in the Japanese yellow swallowtail butterfly, Papilio xuthus, neural mechanisms underlying its color vision are largely unexplored. Towards a better understanding of signal processing in the visual system of P. xuthus, we used immunocytochemical techniques to analyze the distribution of transmitter candidates, namely, histamine, serotonin, tyramine and ?-aminobutyric acid (GABA). Photoreceptor terminals in the lamina and medulla exhibited histamine immunoreactivity as demonstrated in other insects. The anti-histamine antiserum also labeled a few large medulla neurons. Medulla intrinsic neurons and centrifugal neurons projecting to the lamina showed serotonin immunoreactivity. Tyramine immunostaining was detected in a subset of large monopolar cells (LMCs) in the lamina, transmedullary neurons projecting to the lobula plate, and cell bodies surrounding the first optic chiasma. An anti-GABA antiserum labeled a subset of LMCs and populations of columnar and tangential neurons surrounding the medulla. Each of the four antisera also labeled a few centrifugal neurons that innervate the lobula complex from the central brain, suggesting that they have neuromodulatory roles. A distinctive feature we found in this study is the possibility that tyramine and GABA act as transmitters in LMCs of P. xuthus, which has not been reported in any other insects so far.

Hamanaka, Yoshitaka; Kinoshita, Michiyo; Homberg, Uwe; Arikawa, Kentaro



Effects of GABA receptor antagonist on trigeminal caudalis nociceptive neurons in normal and neonatally capsaicin-treated rats.  


We have recently demonstrated that significant increases in cutaneous mechanoreceptive field (RF) size and spontaneous activity occur in nociceptive neurons of trigeminal subnucleus caudalis (Vc, the medullary dorsal horn) of adult rats depleted of C-fiber afferents by neonatal treatment with capsaicin. These neuronal changes in capsaicin-treated (CAP) rats are suggestive of central neuroplasticity and involve N-methyl-D-aspartic acid (NMDA) receptor mechanisms. The present study examined whether the GABA(A) receptor antagonist bicuculline (BIC) or the GABA(B) receptor antagonist 2-hydroxysaclofen (SAC) can influence the RF properties and activity of Vc nociceptive neurons classified as either nociceptive-specific or wide-dynamic range in CAP adult rats or in neonatally vehicle-treated (CON) rats. C-fiber depletion was confirmed in the CAP rats by a significant decrease in plasma extravasation of Evans blue dye in a skin area receiving topical application of mustard oil, a small-fiber excitant and inflammatory irritant. As previously reported, marked increases in cutaneous RF size and spontaneous activity occurred in Vc nociceptive neurons of adult CAP rats, compared with CON rats. GABA(A) receptor blockade by BIC (i.t.) in CON rats produced a significant increase in spontaneous activity and in pinch RF size and tactile RF size (or appearance of a tactile area in the RF of nociceptive-specific neurons), as well as a significant lowering of the mechanical threshold and a significant enhancement of responses to pinch stimuli applied to the RF. In CAP rats, GABA(A) receptor blockade also produced significant changes similar to those documented in CON rats, except for a paradoxical and significant decrease in pinch RF size and no noticeable changes in responses to pinch stimuli. GABA(B) receptor blockade by SAC (i.t. ) did not produce any significant changes in Vc nociceptive neurons in either CON or CAP rats. These results suggest that GABA(A) receptor-mediated inhibition may be involved in maintaining the functional expression of Vc nociceptive neuronal properties in normal conditions, and that in animals depleted of their C-fiber afferents, some features of this GABA(A) receptor-mediated modulation may be disrupted such that a GABA(A) receptor-mediated excitation is manifested. PMID:10561395

Chiang, C Y; Kwan, C L; Hu, J W; Sessle, B J



Bioassay-guided fractionation of lemon balm (Melissa officinalis L.) using an in vitro measure of GABA transaminase activity.  


A novel pharmacological mechanism of action for the anxiolytic botanical Melissa officinalis L. (lemon balm) is reported. The methanol extract was identified as a potent in vitro inhibitor of rat brain GABA transaminase (GABA-T), an enzyme target in the therapy of anxiety, epilepsy and related neurological disorders. Bioassay-guided fractionation led to the identification and isolation of rosmarinic acid (RA) and the triterpenoids, ursolic acid (UA) and oleanolic acid (OA) as active principles. Phytochemical characterization of the crude extract determined RA as the major compound responsible for activity (40% inhibition at 100 microg/mL) since it represented approximately 1.5% of the dry mass of the leaves. Synergistic effects may also play a role. PMID:19165747

Awad, Rosalie; Muhammad, Asim; Durst, Tony; Trudeau, Vance L; Arnason, John T



Gamma Hydroxybutyric Acid (GHB) Intoxication  

Microsoft Academic Search

Gamma-aminobutyric acid (GABA) was discovered as the predominant inhibitory central nervous sys- tem (CNS) neurotransmitter in 1956. This prompted a search for a GABA analog that would cross the blood-brain barrier for possible therapeutic use. During this search, gamma-hydroxybutyric acid (GHB) was found in the brain and subsequently synthesized in the laboratory in 1964. 1,2 Since its discovery, GHB has

Phillip E. Mason; William P. Kerns II



5HT 7 receptors modulate synchronized network activity in rat hippocampus  

Microsoft Academic Search

In the CA3 region of rat hippocampal slices ?-amino-butyric acid (GABA)A\\/B receptor antagonists induce low frequency bursting activity that was either inhibited (in 21% of slices) or increased by the selective 5-HT receptor agonists 5-carboxy-tryptamine (0.1–1 ?M) and 8-hydroxydipropylaminotetralin (8-OH-DPAT). The selective 5-HT1A receptor antagonist N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexane carboxamide (WAY 100635) reversed the depression of bursting activity whereas the 5-HT7 receptor antagonist,

Catherine H. Gill; Ellen M. Soffin; Jim J. Hagan; Ceri H. Davies



Polycomblike protein PHF1b: a transcriptional sensor for GABA receptor activity  

PubMed Central

Background The ?-aminobutyric acid (GABA) type A receptor (GABAAR) contains the recognition sites for a variety of agents used in the treatment of brain disorders, including anxiety and epilepsy. A better understanding of how receptor expression is regulated in individual neurons may provide novel opportunities for therapeutic intervention. Towards this goal we have studied transcription of a GABAAR subunit gene (GABRB1) whose activity is autologously regulated by GABA via a 10 base pair initiator-like element (?1-INR). Methods By screening a human cDNA brain library with a yeast one-hybrid assay, the Polycomblike (PCL) gene product PHD finger protein transcript b (PHF1b) was identified as a ?1-INR associated protein. Promoter/reporter assays in primary rat cortical cells demonstrate that PHF1b is an activator at GABRB1, and chromatin immunoprecipitation assays reveal that presence of PHF1 at endogenous Gabrb1 is regulated by GABAAR activation. Results PCL is a member of the Polycomb group required for correct spatial expression of homeotic genes in Drosophila. We now show that PHF1b recognition of ?1-INR is dependent on a plant homeodomain, an adjacent helix-loop-helix, and short glycine rich motif. In neurons, it co-immunoprecipitates with SUZ12, a key component of the Polycomb Repressive Complex 2 (PRC2) that regulates a number of important cellular processes, including gene silencing via histone H3 lysine 27 trimethylation (H3K27me3). Conclusions The observation that chronic exposure to GABA reduces PHF1 binding and H3K27 monomethylation, which is associated with transcriptional activation, strongly suggests that PHF1b may be a molecular transducer of GABAAR function and thus GABA-mediated neurotransmission in the central nervous system.



Investigations on GABA B receptor-mediated autoinhibition of GABA release  

Microsoft Academic Search

In this study, we have investigated the effects of phaclofen on the [3H] overflow from [3H]GABA prelabelled rat cortical slices and its interaction with the effects of (-)-baclofen in dependence of the stimulation frequency. (-)-Baclofen strongly depressed the [3H] overflow in the frequency range of 0.125 to 4 Hz to a constant residual level (ICIn50 = 0.37 µmol\\/l at 0.125

P. A. Baumann; P. Wicki; C. Stierlin; P. C. Waldmeier



Analysis of Glutamate, GABA, Noradrenaline, Dopamine, Serotonin, and Metabolites Using Microbore UHPLC with Electrochemical Detection  

PubMed Central

The applicability of microbore ultrahigh performance liquid chromatography (UHPLC) with electrochemical detection for offline analysis of a number of well-known neurotransmitters in less than 10 ?L microdialysis fractions is described. Two methods are presented for the analysis of monoamine or amino acid neurotransmitters, using the same UHPLC instrument. Speed of analysis of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and the metabolites homovanillic acid (HVA), 5-hydroxyindole aceticacid (5-HIAA), and 3,4-dihydroxyphenylacetic acid (DOPAC) was predominated by the retention behavior of NA, the nonideal behavior of matrix components, and the loss in signal of 5-HT. This method was optimized to meet the requirements for detection sensitivity and minimizing the size of collected fractions, which determines temporal resolution in microdialysis. The amino acid neurotransmitters glutamate (Glu) and ?-aminobutyric acid (GABA) were analyzed after an automated derivatization procedure. Under optimized conditions, Glu was resolved from a number of early eluting system peaks, while the total runtime was decreased to 15 min by a 4-fold increase of the flow rate under UHPLC conditions. The detection limit for Glu and GABA was 10 nmol/L (15 fmol in 1.5 ?L); the monoamine neurotransmitters had a detection limit between 32 and 83 pmol/L (0.16–0.42 fmol in 5 ?L) in standard solutions. Using UHPLC, the analysis times varied from 15 min to less than 2 min depending on the complexity of the samples and the substances to be analyzed.



Dopaminergic neurons modulate GABA neuron migration in the embryonic midbrain  

PubMed Central

Neuronal migration, a key event during brain development, remains largely unexplored in the mesencephalon, where dopaminergic (DA) and GABA neurons constitute two major neuronal populations. Here we study the migrational trajectories of DA and GABA neurons and show that they occupy ventral mesencephalic territory in a temporally and spatially specific manner. Our results from the Pitx3-deficient aphakia mouse suggest that pre-existing DA neurons modulate GABA neuronal migration to their final destination, providing novel insights and fresh perspectives concerning neuronal migration and connectivity in the mesencephalon in normal as well as diseased brains.

Vasudevan, Anju; Won, Chungkil; Li, Suyan; Erdelyi, Ferenc; Szabo, Gabor; Kim, Kwang-Soo



Involvement of sialic acid in the regulation of ?--aminobutyric acid uptake activity of ?-aminobutyric acid transporter 1.  


The ?-aminobutyric acid (GABA) transporters (GATs) have long been recognized for their key role in the uptake of neurotransmitters. The GAT1 belongs to the family of Na(+)- and Cl(-)-coupled transport proteins, which possess 12 putative transmembrane (TM) domains and three N-glycosylation sites on the extracellular loop between TM domains 3 and 4. Previously, we demonstrated that terminal trimming of N-glycans is important for the GABA uptake activity of GAT1. In this work, we examined the effect of deficiency, removal or oxidation of surface sialic acid residues on GABA uptake activity to investigate their role in the GABA uptake of GAT1. We found that the reduced concentration of sialic acid on N-glycans was paralleled by a decreased GABA uptake activity of GAT1 in Chinese hamster ovary (CHO) Lec3 cells (mutant defective in sialic acid biosynthesis) in comparison to CHO cells. Likewise, either enzymatic removal or chemical oxidation of terminal sialic acids using sialidase or sodium periodate, respectively, resulted in a strong reduction in GAT1 activity. Kinetic analysis revealed that deficiency, removal or oxidation of terminal sialic acids did not affect the K(m) GABA values. However, deficiency and removal of terminal sialic acids of GAT1 reduced the V(max) GABA values with a reduced apparent affinity for extracellular Na(+). Oxidation of cell surface sialic acids also strongly reduced V(max) without affecting both affinities of GAT1 for GABA and Na(+), respectively. These results demonstrated for the first time that the terminal sialic acid of N-linked oligosaccharides of GAT1 plays a crucial role in the GABA transport process. PMID:21045010

Hu, Jing; Fei, Jian; Reutter, Werner; Fan, Hua



Inter- and intracellular relationship of substance P-containing neurons with serotonin and GABA in the dorsal raphe nucleus: combination of autoradiographic and immunocytochemical techniques  

SciTech Connect

Double-labeling experiments were performed at the electron microscopic level in the dorsal raphe nucleus of rat, in order to study the inter- and intracellular relationship of substance P with gamma-aminobutyric acid (GABA) and serotonin. Autoradiography for either (/sup 3/H)serotonin or (/sup 3/H)GABA was coupled, on the same tissue section, with peroxidase-antiperoxidase immunocytochemistry for substance P in colchicine-treated animals. Intercellular relationships were represented by synaptic contacts made by (/sup 3/H)serotonin-labeled terminals on substance P-containing somata and dendrites, and by substance P-containing terminals on (/sup 3/H)GABA-labeled cells. Intracellular relationships were suggested by the occurrence of the peptide within (/sup 3/H)serotonin-containing and (/sup 3/H)GABA-containing cell bodies and fibers. Doubly labeled varicosities of the two kinds were also observed in the supraependymal plexus adjacent to the dorsal raphe nucleus. The results demonstrated that, in addition to reciprocal synaptic interactions made by substance P with serotonin and GABA, the dorsal raphe nucleus is the site of intracellular relationships between the peptide and either the amine or the amino acid.

Magoul, R.; Onteniente, B.; Oblin, A.; Calas, A.



Experiment K-6-18. Study of muscarinic and gaba (benzodiazepine) receptors in the sensory-motor cortex, hippcampus and spinal code  

NASA Technical Reports Server (NTRS)

Frontal lobe samples of rat brains flown aboard Cosmos 1887 were processed for the study of muscarinic (cholinergic) and GABA (benzodiazepine) receptors and for immunocytochemical localization of the neurotransmitter gamma-aminobutyric acid (GABA) and glial fibrillary acidic protein (GFAP). Although radioactive labeling of both muscarinic cholinergic and GABA (benzodiazepine) receptors proved to be successful with the techniques employed, distinct receptor localization of individual laminae of the frontal neocortex was not possible since the sampling of the area was different in the various groups of animals. In spite of efforts made for proper orientation and regional identification of laminae, it was found that a densitometric (quantitation of autoradiograms) analysis of the tissue did not contribute to the final interpretation of the effects of weightlessness on these receptors. As to the immunocytochemical studies the use of both markers, GFAP and GABA antiserum, confirmed the suitability of the techniques for use in frozen material. However, similar problems to those encountered in the receptor studies prevented an adequate interpretation of the effects of micro-G exposure on the localization and distribution of GABA and GFAP. This study did, however, confirm the feasibility of investigating neurotransmitters and their receptors in future space flight experiments.

Daunton, N.; Damelio, F.; Krasnov, I.



Identification of GABA A receptor modulators in Kadsura longipedunculata and assignment of absolute configurations by quantum-chemical ECD calculations  

PubMed Central

A petroleum ether extract of Kadsura longipedunculata enhanced the GABA-induced chloride current (IGABA) by 122.5 ± 0.3% (n = 2) when tested at 100 ?g/ml in Xenopus laevis oocytes expressing GABA A receptors (?1?2?2S subtype) in two-microelectrode voltage clamp measurements. Thirteen compounds were subsequently identified by HPLC-based activity profiling as responsible for GABA A receptor activity and purified in preparative scale. 6-Cinnamoyl-6,7-dihydro-7-myrceneol and 5,6-dihydrocuparenic acid were thereby isolated for the first time. The determination of the absolute stereochemistry of these compounds was achieved by comparison of experimental and calculated ECD spectra. All but one of the 13 isolated compounds from K. longipedunculata potentiated IGABA through GABA A receptors composed of ?1?2?2S subunits in a concentration-dependent manner. Potencies ranged from 12.8 ± 3.1 to 135.6 ± 85.7 ?M, and efficiencies ranged from 129.7 ± 36.8% to 885.8 ± 291.2%. The phytochemical profiles of petroleum ether extracts of Kadsura japonica fruits (114.1 ± 2.6% potentiation of IGABA at 100 ?g/ml, n = 2), and Schisandra chinensis fruits (inactive at 100 ?g/ml) were compared by HPLC-PDA-ESIMS with that of K. longipedunculata.

Zaugg, Janine; Ebrahimi, Samad Nejad; Smiesko, Martin; Baburin, Igor; Hering, Steffen; Hamburger, Matthias



Neuroprotection of co-activation of GABA receptors by preventing caspase-3 denitrosylation in KA-induced seizures.  


Previous studies have demonstrated that kainic acid (KA)-induced seizures can cause the enhancement of excitation and lead to neuronal death in rat hippocampus. Co-activation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module induced by KA in epileptic rat hippocampal CA1 and CA3 regions. Caspase-3 is a cysteine protease located in both the cytoplasm and mitochondrial intermembrane space that is a central effector of many apoptotic pathways. We designed experiments to elucidate the underlying molecular mechanisms of procaspase-3 activation and neuroprotection of co-activation of GABA receptors against neuronal death induced by KA. In this study, we show that co-activation of GABA receptors can attenuate the Fas/FasL apoptotic signaling pathway and inhibit the increased of thioredoxin reductase activity induced by KA, subsequently inhibit the activation of procaspase-3 by diminishing the denitrosylation of its active-site thiol and decreasing the cleavage of the caspase-3 zymogen to its active subunits. These results indicate that co-activation of GABA receptors results in neuroprotection by preventing caspase-3 denitrosylation in KA-induced seizure of rats. PMID:22613773

Wei, Xue-Wen; Yan, Hui; Xu, Bo; Wu, Yong-Ping; Li, Chong; Zhang, Guang-Yi



Influence of processing on the generation of ? -aminobutyric acid in green coffee beans  

Microsoft Academic Search

A determination of the concentrations of free amino acids in differently processed green coffees indicated the nonprotein amino acid ?-aminobutyric acid (GABA), a well-known plant stress metabolite, to be present in raw coffee beans (Coffea arabica L.) in significantly varying amounts. The GABA content of unwashed Arabica beans (green coffee produced by the dry processing method) was always markedly higher

Gerhard Bytof; Sven-Erik Knopp; Peter Schieberle; Ingo Teutsch; Dirk Selmar



GABA Metabolism and Transport: Effects on Synaptic Efficacy  

PubMed Central

GABAergic inhibition is an important regulator of excitability in neuronal networks. In addition, inhibitory synaptic signals contribute crucially to the organization of spatiotemporal patterns of network activity, especially during coherent oscillations. In order to maintain stable network states, the release of GABA by interneurons must be plastic in timing and amount. This homeostatic regulation is achieved by several pre- and postsynaptic mechanisms and is triggered by various activity-dependent local signals such as excitatory input or ambient levels of neurotransmitters. Here, we review findings on the availability of GABA for release at presynaptic terminals of interneurons. Presynaptic GABA content seems to be an important determinant of inhibitory efficacy and can be differentially regulated by changing synthesis, transport, and degradation of GABA or related molecules. We will discuss the functional impact of such regulations on neuronal network patterns and, finally, point towards pharmacological approaches targeting these processes.

Roth, Fabian C.; Draguhn, Andreas



[Hepatoduodenal circulation and excretion of the new GABA derivative citrocard].  


Pharmacokinetic investigation of a new gamma-aminobutyric acid (GABA) derivative cirtocard showed that, upon the intravenous introduction, the drug is determined in high concentrations in organs of elimination--the liver and kidneys. The tissue accessibility amounts to 1.341 for the liver and 4.053 for the kidneys and the separation factor is 1.041 for the liver and 4.486 for the kidneys. The study of drug excretion showed that cirtocard is determined in the urine for 48 h, its nephritic clearance being 0.047 L/h and extra-nephritic clearance, 0.33 L/h. For the unchanged substance, a large significance ofhepatoduodenal circulation is low probable, since no more than 1 - 2% of the introduced dose was isolated with bile over entire experiment. It is established that the removal of the unchanged substance does not exceed 10% of the introduced dose. There is high probability of hepatoduodenal circulation and excretion of the preparation in the form of metabolites. PMID:23767103

Tiurenkov, I N; Perfilova, V N; Smirnova, L A; Riabukha, A F; Suchkov, E A; Lebedeva, S A



GAB(A) receptors present higher affinity and modified subunit composition in spinal motor neurons from a genetic model of amyotrophic lateral sclerosis.  


Amyotrophic lateral sclerosis is a neurodegenerative disease characterized by the selective degeneration of motor neurons in the spinal cord, brainstem and cerebral cortex. In this study we have analysed the electrophysiological properties of GABA(A) receptors and GABA(A) alpha1 and alpha2 subunits expression in spinal motor neurons in culture obtained from a genetic model of ALS (G93A) and compared with transgenic wild type SOD1 (SOD1) and their corresponding non transgenic litter mates (Control). Although excitotoxic motor neuron death has been extensively studied in relation to Ca(2+)-dependent processes, strong evidence indicates that excitotoxic cell death is also remarkably dependent on Cl(-) ions and on GABA(A) receptor activation. In this study we have analysed the electrophysiological properties of GABA(A) receptors and the expression of GABA(A)alpha(1) and alpha(2) subunits in cultured motor neurons obtained from a genetic model of amyotrophic lateral sclerosis (G93A) and compared them with transgenic wild-type Cu,Zn superoxide dismutase and their corresponding non-transgenic littermates (Control). In all tested motor neurons, the application of gamma-aminobutyric acid (GABA) (0.5-100 mum) evoked an inward current that was reversibly blocked by bicuculline (100 mum), thus indicating that it was mediated by the activation of GABA(A) receptors. Our results indicate that the current density at high GABA concentrations is similar in control, Cu,Zn superoxide dismutase and G93A motor neurons. However, the dose-response curve significantly shifted toward lower concentration values in G93A motor neurons and the extent of desensitization also increased in these neurons. Finally, multiplex single-cell real-time polymerase chain reaction and immunofluorescence revealed that the amount of GABA(A)alpha(1) subunit was significantly increased in G93A motor neurons, whereas the levels of alpha(2) subunit were unchanged. These data show that the functionality and expression of GABA(A) receptors are altered in G93A motor neurons inducing a higher Cl(-) influx into the cell with a possible consequent neuronal excitotoxicity acceleration. PMID:18973555

Carunchio, Irene; Mollinari, Cristiana; Pieri, Massimo; Merlo, Daniela; Zona, Cristina



Ketone Bodies and Brain Glutamate and GABA Metabolism  

Microsoft Academic Search

The effects of ketone bodies on brain metabolism of glutamate and GABA were studied in three different systems: synaptosomes, cultured astrocytes and the whole animal. In synaptosomes the addition of either acetoacetate or 3-OH-butyrate was associated with diminished consumption of glutamate via transamination to aspartate and increased formation of labelled GABA from either L-[2H5-2,3,3,4,4]glutamine or L-[15N]glutamine. There was no effect

Yevgeny Daikhin; Marc Yudkoff



GABA level, gamma oscillation, and working memory performance in schizophrenia  

PubMed Central

A relationship between working memory impairment, disordered neuronal oscillations, and abnormal prefrontal GABA function has been hypothesized in schizophrenia; however, in vivo GABA measurements and gamma band neural synchrony have not yet been compared in schizophrenia. This case–control pilot study (N = 24) compared baseline and working memory task-induced neuronal oscillations acquired with high-density electroencephalograms (EEGs) to GABA levels measured in vivo with magnetic resonance spectroscopy. Working memory performance, baseline GABA level in the left dorsolateral prefrontal cortex (DLPFC), and measures of gamma oscillations from EEGs at baseline and during a working memory task were obtained. A major limitation of this study is a relatively small sample size for several analyses due to the integration of diverse methodologies and participant compliance. Working memory performance was significantly lower for patients than for controls. During the working memory task, patients (n = 7) had significantly lower amplitudes in gamma oscillations than controls (n = 9). However, both at rest and across working memory stages, there were significant correlations between gamma oscillation amplitude and left DLPFC GABA level. Peak gamma frequency during the encoding stage of the working memory task (n = 16) significantly correlated with GABA level and working memory performance. Despite gamma band amplitude deficits in patients across working memory stages, both baseline and working memory-induced gamma oscillations showed strong dependence on baseline GABA levels in patients and controls. These findings suggest a critical role for GABA function in gamma band oscillations, even under conditions of system and cognitive impairments as seen in schizophrenia.

Chen, Chi-Ming A.; Stanford, Arielle D.; Mao, Xiangling; Abi-Dargham, Anissa; Shungu, Dikoma C.; Lisanby, Sarah H.; Schroeder, Charles E.; Kegeles, Lawrence S.



gamma-Aminobutyric-acid- and pentobarbitone-gated chloride currents in internally perfused frog sensory neurones.  


gamma-Aminobutyric-acid- (GABA) and pentobarbitone-induced Cl- currents (ICl) were studied in isolated frog sensory neurones after suppression of Na+, K+ and Ca2+ currents using a suction-pipette technique combining internal perfusion with voltage clamp. All GABA-sensitive neurones responded to pentobarbitone. Both GABA- and pentobarbitone-induced ICl reversed at the Cl- equilibrium potential (ECl). The dose-response curve for maxima of GABA-induced ICl was sigmoidal with a mean concentration producing a half-maximum response, Ka of 2 X 10(-5) M at a Hill coefficient of 1.8. In the presence of pentobarbitone, the GABA dose-response curve shifted to the left without affecting the saturating maximum current. At high concentrations, both GABA and pentobarbitone could also potentiate the pentobarbitone- and GABA-induced ICl respectively, while pre-treatment with one of the two markedly attenuated currents induced by the other, indicating a 'cross-desensitization'. In the presence of pentobarbitone, the augmented response was voltage dependent and this augmentation was much greater in the inward-current direction than outward. In producing ICl, pentobarbitone and its stereoisomers were potent in the order of (-) isomer greater than (+/-) racemic mixture greater than (+) isomer. A stereospecific facilitatory action of pentobarbitone on GABA responses was also found in the same order. Responses to GABA, homotaurine, taurine, beta-alanine, 5-aminovaleric acid, (+)- and (-)-gamma-amino-beta-hydroxybutyric acid and muscimol were equally enhanced by pentobarbitone, though its action on glycine-induced ICl was less effective. Picrotoxin inhibited the GABA- and pentobarbitone-induced ICl from either side of membrane, while internal application of GABA and pentobarbitone did not exert any effect. It was concluded that pentobarbitone binds to the 'barbiturate receptors' located close to the GABA receptor-Cl- channel complex, and directly affects the GABA-GABA receptor interactions rather than the ionic channels. PMID:2580971

Akaike, N; Hattori, K; Inomata, N; Oomura, Y



Indirect effects of amino-acids on sympathetic ganglion cells mediated through the release of gamma-aminobutyric acid from glial cells.  

PubMed Central

1 All experiments were performed on rat isolated desheathed superior cervical ganglia maintained in Krebs solution containing amino-oxyacetic acid (10 muM) at 25 degrees C. 2 Influx rates of gamma-amino-n-butyric acid (GABA) were measured by incubating ganglia in 0.5 muM [3H]-GABA for 30 minutes. Influx was inhibited by 50% on adding 14.3 muM unlabelled GABA, 59.2 muM beta-alanine (BALA) or 424 muM beta-amino-n-butyric acid (BABA). 3 Efflux of [3H]-GABA into non-radioactive solution superfused over ganglia previously incubated for 60 min in 1 muM [3H]-GABA was measured. The mean resting efflux rate coefficient (k) was 0.64 +/- 0.05 X 10(-3) min-1. Addition of high concentrations of unlabelled GABA, BABA or BALA to the superfusing solution increased k by (maximally) 3.6-4.3 times; half-maximal increases occurred at the following concentrations: GABA, 16 muM; BALA, 85 muM; BABA, 606 muM. Replacement of external Na+ with Li+ or TRIS increased the resting value of k and inhibited acceleration by external amino acids. Prior incubation in 1 muM [3H]-GABA with 1 mM unlabelled GABA increased resting k 1.5 times, but did not alter the peak rate coefficient produced by external amino acids. 4 Neuronal depolarization produced by the amino acids was measured with surface electrodes. Pre-incubation in 1 mM GABA for 60 min potentiated low-amplitude responses to BALA or BABA but not those to GABA or 3-aminopropanesulphonic acid (a potent agonist with low affinity for the GABA carrier). Omission of external Na+ reduced responses to BABA but increased those to GABA. 5 Incubation in 1 mM GABA for 60 min (as required to potentiate BABA or BALA actions) increased the amount of GABA in the tissue from 0.21 to 0.73 mmol/kg wet weight. Autoradiographs in which labelled GABA was used indicated that uptake into neuroglial cells was responsible for this accumulation. 6 It is suggested that: (i) BALA and BABA are substrates for the inward GABA carrier responsible for GABA entry into ganglionic glial cells; (ii) they accelerate efflux by inhibiting carrier-mediated reaccumulation of effluent GABA by the glial cells; (iii) interstitial GABA concentrations are thereby increased to a level capable of depolarizing adjacent neurones; and (iv) this, rather than direct GABA-receptor activation, accounts for the depolarization produced by low concentrations of BALA and BABA. Potentiation of their depolarizing action after pre-incubation in 1 mM GABA is suggested to result from the increased amount of intracellular GABA available for release, and is quantitatively compatible with this increase; inhibition in Na+-free solution is due to their inability to inhibit reaccumulation of GABA under these conditions. 7 A model for the action of carrier substrates is described in an Appendix. Calculations based thereon yield increments in interstitial GABA concentration in the presence of carrier substrates compatible with those determined experimentally (up to 1 muM at rest or 3.4 muM after pre-incubation in GABA). Images Figure 5

Bowery, N G; Brown, D A; Collins, G G; Galvan, M; Marsh, S; Yamini, G



GABA-independent GABAA Receptor Openings Maintain Tonic Currents  

PubMed Central

Activation of GABAA receptors (GABAARs) produces two forms of inhibition: ‘phasic’ inhibition generated by the rapid, transient activation of synaptic GABAARs by presynaptic GABA release, and tonic inhibition generated by the persistent activation of peri- or extrasynaptic GABAARs which can detect extracellular GABA. Such tonic GABAAR-mediated currents are particularly evident in dentate granule cells in which they play a major role in regulating cell excitability. Here we show that in rat dentate granule cells in ex-vivo hippocampal slices, tonic currents are predominantly generated by GABA-independent GABAA receptor openings. This tonic GABAAR conductance is resistant to the competitive GABAAR antagonist SR95531, which at high concentrations acts as a partial agonist, but can be blocked by an open channel blocker picrotoxin. When slices are perfused with 200 nM GABA, a concentration that is comparable to cerebrospinal fluid concentrations but is twice that measured by us in the hippocampus in vivo using zero-net-flux microdialysis, negligible GABA is detected by dentate granule cells. Spontaneously opening GABAARs, therefore, maintain dentate granule cell tonic currents in the face of low extracellular GABA concentrations.

Wlodarczyk, Agnieszka I.; Sylantyev, Sergiy; Herd, Murray B.; Kersante, Flavie; Lambert, Jeremy J.; Rusakov, Dmitri A.; Linthorst, Astrid C.E.; Semyanov, Alexey; Belelli, Delia; Pavlov, Ivan; Walker, Matthew C.



Regionally Specific Human GABA Concentration Correlates with Tactile Discrimination Thresholds  

PubMed Central

The neural mechanisms underlying variability in human sensory perception remain incompletely understood. In particular, few studies have attempted to investigate the relationship between in vivo measurements of neurochemistry and individuals’ behavioral performance. Our previous work found a relationship between GABA concentration in the visual cortex and orientation discrimination thresholds (Edden et al., 2009). In the present study, we used magnetic resonance spectroscopy of GABA and psychophysical testing of vibrotactile frequency thresholds to investigate whether individual differences in tactile frequency discrimination performance are correlated with GABA concentration in sensorimotor cortex. Behaviorally, individuals showed a wide range of discrimination thresholds ranging from 3 to 7.6 Hz around the 25 Hz standard. These frequency discrimination thresholds were significantly correlated with GABA concentration (r = ?0.58; p < 0.05) in individuals’ sensorimotor cortex, but not with GABA concentration in an occipital control region (r = ?0.04). These results demonstrate a link between GABA concentration and frequency discrimination in vivo, and support the hypothesis that GABAergic mechanisms have an important role to play in sensory discrimination.

Puts, Nicolaas A. J.; Edden, Richard A. E.; Evans, C. John; McGlone, Francis; McGonigle, David J.



Responses to gamma-aminobutyric acid applied to cell bodies and dendrites of rat visual cortical neurons.  


The effects of pressure-applied gamma-aminobutyric acid (GABA) on the soma and dendrites of pyramidal and non-pyramidal neurons of rat visual cortical slices were recorded intracellularly. When applied close to the soma, GABA produced hyperpolarizations and depolarizations, but when GABA was applied more than 250 microns from the soma only depolarizations were recorded. The results suggest that most visual cortical cells respond to GABA and that the responses of pyramidal and non-pyramidal cells to GABA are similar. PMID:4075128

Scharfman, H E; Sarvey, J M



Plasma and cerebrospinal fluid gamma-aminobutyric acid in neurological disorders.  

PubMed Central

In 49 patients with various neurological disorders plasma and CSF gamma-aminobutyric acid (GABA) concentrations were determined by radioreceptor assay. The CSF GABA concentration of 127 +/- 47 pmol/ml (range: 65-275; n = 52) was independent of the age, the sex and the intake of various drugs including benzodiazepines, baclofen and antidepressants. Patients with diverse neurological disorders such as multiple sclerosis, ischaemic strokes, intracranial tumour and polyneuropathies had similar CSF GABA levels. The mean plasma GABA concentration was 309 +/- 79 pmol/ml (range: 179-498; n = 44). The correlation between the GABA concentrations of CSF and plasma was very poor (r = 0.18; n = 44). Therefore plasma GABA is not a suitable indicator for CSF GABA.

Schmidt, D; Loscher, W



Correlation between GABA A receptor density and vagus nerve stimulation in individuals with drug-resistant partial epilepsy  

Microsoft Academic Search

Vagus nerve stimulation (VNS) is an important option for the treatment of drug-resistant epilepsy. Through delivery of a battery-supplied intermittent current, VNS protects against seizure development in a manner that correlates experimentally with electrophysiological modifications. However, the mechanism by which VNS inhibits seizures in humans remains unclear. The impairment of ?-aminobutyric acid (GABA)-mediated neuronal inhibition associated with epilepsy has suggested

Francesco Marrosu; Alessandra Serra; Alberto Maleci; Monica Puligheddu; Giovanni Biggio; Mario Piga



GABA A-receptor-mediated increase in intracellular Ca 2+ concentration in the regenerating retina of adult newt  

Microsoft Academic Search

We used optical recording with the Ca2+-sensitive dye, fura-2, in living slice preparations from the newt retina at different stages of regeneration. ?-Aminobutyric acid (GABA) induced pronounced [Ca2+]i rise in progenitor cells and differentiating ganglion cells in the ‘intermediate’ stage of retinal regeneration. This [Ca2+]i rise became less pronounced at the beginning of synapse formation in the late regenerating retina.

Motoko Ohmasa; Takehiko Saito