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Sample records for acid gaba type

  1. Neuronal gamma-aminobutyric acid (GABA) type A receptors undergo cognate ligand chaperoning in the endoplasmic reticulum by endogenous GABA

    PubMed Central

    Wang, Ping; Eshaq, Randa S.; Meshul, Charles K.; Moore, Cynthia; Hood, Rebecca L.; Leidenheimer, Nancy J.

    2015-01-01

    GABAA receptors mediate fast inhibitory neurotransmission in the brain. Dysfunction of these receptors is associated with various psychiatric/neurological disorders and drugs targeting this receptor are widely used therapeutic agents. Both the efficacy and plasticity of GABAA receptor-mediated neurotransmission depends on the number of surface GABAA receptors. An understudied aspect of receptor cell surface expression is the post-translational regulation of receptor biogenesis within the endoplasmic reticulum (ER). We have previously shown that exogenous GABA can act as a ligand chaperone of recombinant GABAA receptors in the early secretory pathway leading us to now investigate whether endogenous GABA facilitates the biogenesis of GABAA receptors in primary cerebral cortical cultures. In immunofluorescence labeling experiments, we have determined that neurons expressing surface GABAA receptors contain both GABA and its degradative enzyme GABA transaminase (GABA-T). Treatment of neurons with GABA-T inhibitors, a treatment known to increase intracellular GABA levels, decreases the interaction of the receptor with the ER quality control protein calnexin, concomittantly increasing receptor forward-trafficking and plasma membrane insertion. The effect of GABA-T inhibition on the receptor/calnexin interaction is not due to the activation of surface GABAA or GABAB receptors. Consistent with our hypothesis that GABA acts as a cognate ligand chaperone in the ER, immunogold-labeling of rodent brain slices reveals the presence of GABA within the rough ER. The density of this labeling is similar to that present in mitochondria, the organelle in which GABA is degraded. Lastly, the effect of GABA-T inhibition on the receptor/calnexin interaction was prevented by pretreatment with a GABA transporter inhibitor. Together, these data indicate that endogenous GABA acts in the rough ER as a cognate ligand chaperone to facilitate the biogenesis of neuronal GABAA receptors. PMID

  2. Positive feedback regulation between gamma-aminobutyric acid type A (GABA(A)) receptor signaling and brain-derived neurotrophic factor (BDNF) release in developing neurons.

    PubMed

    Porcher, Christophe; Hatchett, Caroline; Longbottom, Rebecca E; McAinch, Kristina; Sihra, Talvinder S; Moss, Stephen J; Thomson, Alex M; Jovanovic, Jasmina N

    2011-06-17

    During the early development of the nervous system, γ-aminobutyric acid (GABA) type A receptor (GABA(A)R)-mediated signaling parallels the neurotrophin/tropomyosin-related kinase (Trk)-dependent signaling in controlling a number of processes from cell proliferation and migration, via dendritic and axonal outgrowth, to synapse formation and plasticity. Here we present the first evidence that these two signaling systems regulate each other through a complex positive feedback mechanism. We first demonstrate that GABA(A)R activation leads to an increase in the cell surface expression of these receptors in cultured embryonic cerebrocortical neurons, specifically at the stage when this activity causes depolarization of the plasma membrane and Ca(2+) influx through L-type voltage-gated Ca(2+) channels. We further demonstrate that GABA(A)R activity triggers release of the brain-derived neurotrophic factor (BDNF), which, in turn by activating TrkB receptors, mediates the observed increase in cell surface expression of GABA(A)Rs. This BDNF/TrkB-dependent increase in surface levels of GABA(A)Rs requires the activity of phosphoinositide 3-kinase (PI3K) and protein kinase C (PKC) and does not involve the extracellular signal-regulated kinase (ERK) 1/2 activity. The increase in GABA(A)R surface levels occurs due to an inhibition of the receptor endocytosis by BDNF, whereas the receptor reinsertion into the plasma membrane remains unaltered. Thus, GABA(A)R activity is a potent regulator of the BDNF release during neuronal development, and at the same time, it is strongly enhanced by the activity of the BDNF/TrkB/PI3K/PKC signaling pathway.

  3. Suppression of γ-aminobutyric acid (GABA) transaminases induces prominent GABA accumulation, dwarfism and infertility in the tomato (Solanum lycopersicum L.).

    PubMed

    Koike, Satoshi; Matsukura, Chiaki; Takayama, Mariko; Asamizu, Erika; Ezura, Hiroshi

    2013-05-01

    Tomatoes accumulate γ-aminobutyric acid (GABA) at high levels in the immature fruits. GABA is rapidly converted to succinate during fruit ripening through the activities of GABA transaminase (GABA-T) and succinate semialdehyde dehydrogenase (SSADH). Although three genes encoding GABA-T and both pyruvate- and α-ketoglutarate-dependent GABA-T activities have been detected in tomato fruits, the mechanism underlying the GABA-T-mediated conversion of GABA has not been fully understood. In this work, we conducted loss-of-function analyses utilizing RNA interference (RNAi) transgenic plants with suppressed pyruvate- and glyoxylate-dependent GABA-T gene expression to clarify which GABA-T isoforms are essential for its function. The RNAi plants with suppressed SlGABA-T gene expression, particularly SlGABA-T1, showed severe dwarfism and infertility. SlGABA-T1 expression was inversely associated with GABA levels in the fruit at the red ripe stage. The GABA contents in 35S::SlGABA-T1(RNAi) lines were 1.3-2.0 times and 6.8-9.2 times higher in mature green and red ripe fruits, respectively, than the contents in wild-type fruits. In addition, SlGABA-T1 expression was strongly suppressed in the GABA-accumulating lines. These results indicate that pyruvate- and glyoxylate-dependent GABA-T is the essential isoform for GABA metabolism in tomato plants and that GABA-T1 primarily contributes to GABA reduction in the ripening fruits.

  4. Production of gaba (γ - Aminobutyric acid) by microorganisms: a review.

    PubMed

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

    2012-10-01

    GABA (γ-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.

  5. Release and effect of gamma-aminobutyric acid (GABA) on rat pineal melatonin production in vitro.

    PubMed

    Rosenstein, R E; Chuluyan, H E; Pereyra, E N; Cardinali, D P

    1989-06-01

    1. 3H-gamma-Aminobutyric acid (GABA) release elicited by a depolarizing K+ stimulus or by noradrenergic transmitter was examined in rat pineals in vitro. 2. The release of 3H-GABA was detectable at a 20 mM K+ concentration in medium and increased steadily up to 80 mM K+. 3. In a Ca2+-free medium 3H-GABA release elicited by 30 mM K+, but not that elicited by 50 mM K+, became blunted. 4. Norepinephrine (NE; 10(-6)-10(-4) M) stimulated 3H-GABA release from rat pineal explants in a dose-dependent manner. 5. The activity of 10(-5) M NE on pineal GABA release was suppressed by equimolecular amounts of prazosin or phentolamine (alpha 1- and alpha 1/alpha 2-adrenoceptor blockers, respectively) and was unaffected by propranolol (beta-adrenoceptor blocker). 6. The alpha 1-adrenoceptor agonist phenylephrine (10(-7)-10(-5) M) and the beta-adrenoceptor agonist isoproterenol (10(-5) M) mimicked the GABA releasing activity of NE, while 10(-7) M isoproterenol failed to affect it; the alpha 2-adrenoceptor agonist clonidine (10(-7)-10(-5) M) did not modify 3H-GABA release. 7. The addition of 10(-4) M GABA or of the GABA transaminase inhibitor gamma-acetylenic GABA or aminooxyacetic acid inhibited the melatonin content and/or release to the medium in rat pineal organotypic cultures. 8. GABA at concentrations of 10(-5) M or greater partially inhibited the NE-induced increase in melatonin production by pineal explants. 9. The depressant effect of GABA on melatonin production was inhibited by the GABA type A receptor antagonist bicuculline; bicuculline alone increased the pineal melatonin content. Baclofen, a GABA type B receptor agonist, did not affect the pineal melatonin content or release. 10. The decrease in serotonin (5-HT) content of rat pineal explants brought about by NE was not modified by GABA; GABA by itself increased 5-HT levels. 11. These results indicate that (a) GABA is released from rat pineals by a depolarizing stimulus of K+ through a mechanism which is partially Ca2

  6. Synaptic GABA release prevents GABA transporter type-1 reversal during excessive network activity

    PubMed Central

    Savtchenko, Leonid; Megalogeni, Maria; Rusakov, Dmitri A.; Walker, Matthew C.; Pavlov, Ivan

    2015-01-01

    GABA transporters control extracellular GABA, which regulates the key aspects of neuronal and network behaviour. A prevailing view is that modest neuronal depolarization results in GABA transporter type-1 (GAT-1) reversal causing non-vesicular GABA release into the extracellular space during intense network activity. This has important implications for GABA uptake-targeting therapies. Here we combined a realistic kinetic model of GAT-1 with experimental measurements of tonic GABAA receptor currents in ex vivo hippocampal slices to examine GAT-1 operation under varying network conditions. Our simulations predict that synaptic GABA release during network activity robustly prevents GAT-1 reversal. We test this in the 0 Mg2+ model of epileptiform discharges using slices from healthy and chronically epileptic rats and find that epileptiform activity is associated with increased synaptic GABA release and is not accompanied by GAT-1 reversal. We conclude that sustained efflux of GABA through GAT-1 is unlikely to occur during physiological or pathological network activity. PMID:25798861

  7. A tonoplast Glu/Asp/GABA exchanger that affects tomato fruit amino acid composition.

    PubMed

    Snowden, Christopher J; Thomas, Benjamin; Baxter, Charles J; Smith, J Andrew C; Sweetlove, Lee J

    2015-03-01

    Vacuolar accumulation of acidic metabolites is an important aspect of tomato fruit flavour and nutritional quality. The amino acids Asp and Glu accumulate to high concentrations during ripening, while γ-aminobutyrate (GABA) shows an approximately stoichiometric decline. Given that GABA can be catabolised to form Glu and subsequently Asp, and the requirement for the fruit to maintain osmotic homeostasis during ripening, we hypothesised the existence of a tonoplast transporter that exports GABA from the vacuole in exchange for import of either Asp or Glu. We show here that the tomato vacuolar membrane possesses such a transport property: transport of Glu across isolated tonoplast vesicle membranes was trans-stimulated in counterexchange mode by GABA, Glu and Asp. We identified SlCAT9 as a candidate protein for this exchanger using quantitative proteomics of a tonoplast-enriched membrane fraction. Transient expression of a SlCAT9-YFP fusion in tobacco confirmed a tonoplast localisation. The function of the protein was examined by overexpression of SlCAT9 in transgenic tomato plants. Tonoplast vesicles isolated from transgenic plants showed higher rates of Glu and GABA transport than wild-type (WT) only when assayed in counterexchange mode with Glu, Asp, or GABA. Moreover, there were substantial increases in the content of all three cognate amino acids in ripe fruit from the transgenic plants. We conclude that SlCAT9 is a tonoplast Glu/Asp/GABA exchanger that strongly influences the accumulation of these amino acids during fruit development.

  8. Biphasic effects of baclofen on phrenic motoneurons: possible involvement of two types of gamma-aminobutyric acid (GABA) receptors.

    PubMed

    Lalley, P M

    1983-08-01

    Intravenous injections of baclofen have two general dose-dependent effects on phrenic motoneurons in anesthetized cats. Small doses (0.5-1.5 mg/kg) increase the frequency of action potentials recorded from single motoneurons and from the phrenic nerve, whereas large doses (2-10 mg/kg) reduce or abolish action potentials. The increase in frequency produced by small doses is accompanied by membrane depolarization and, in most experiments, by increased input resistance. Large doses hyperpolarize phrenic motoneurons and produce greater increases in input resistance. Extracellular recording during microelectrophoretic application of baclofen reveals only one effect, depression of cell firing, at all effective current strengths. The low dose stimulatory effect of i.v. baclofen is attributed to disinhibition, whereas the depression by large doses is attributed to disfacilitation. During incomplete inhibition by baclofen, CO2 administration further depresses phrenic nerve activity. Bicuculline (100-600 micrograms/kg i.v.) and picrotoxin (900 micrograms/kg i.v.) restore firing depressed by baclofen, whereas strychnine (80-1280 micrograms/kg) does not. 3-Aminopropanesulfonic acid (5-75 mg/kg i.v.) an agonist at gamma-aminobutyric acid-A receptor sites, depresses phrenic nerve activity. It is suggested that the low dose stimulatory effects are related to actions at gamma-aminobutyric acid-B receptors, whereas the high dose depressant effects are related, at least in part, to activation of gamma-aminobutyric acid-A receptors.

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

    SciTech Connect

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

    1991-04-01

    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.

  10. Differences in cardiovascular responses to peripherally administered GABA as influenced by basal conditions and type of anaesthesia.

    PubMed

    Giuliani, S; Maggi, C A; Meli, A

    1986-07-01

    The cardiovascular (blood pressure, heart rate, cardiac contractility) effects of i.v. gamma-aminobutyric acid (GABA) were investigated in guinea-pigs anaesthetized with barbitone or urethane. GABA (0.1-10 mg kg-1) produced a transient 'depressive' effect on cardiovascular parameters which in barbitone-anaesthetized animals was followed by a transient 'excitatory' effect. Resting cardiovascular parameters were higher in urethane-as compared to barbitone-anaesthetized animals. Picrotoxin pretreatment (2 mg kg-1, i.v.) barely affected the cardiovascular changes produced by GABA in barbitone-anaesthetized animals. In picrotoxin pretreated animals anaesthetized with urethane, GABA produced an initial depression of cardiovascular parameters followed by an excitatory phase. Hexamethonium (20 mg kg-1, i.v.) suppressed or reduced markedly the GABA-induced cardiovascular changes both in barbitone- or urethane- anaesthetized animals. Reserpine pretreatment lowered resting cardiovascular parameters. In these animals, regardless of type of anaesthesia, the effects of i.v. GABA were of the 'excitatory' type only. Reserpine pretreated animals anaesthetized with barbitone were selected for further experiments. Various GABAA receptor agonists (homotaurine, muscimol, THIP, 5-aminovaleric acid) mimicked the 'excitatory' effect of GABA in reserpine pretreated animals anesthetized with barbitone and prevented the effects of subsequent GABA administration. On the other hand (+/-)-baclofen, a selective GABAB receptor agonist, had a slight depressant effect and did not prevent the 'excitatory' cardiovascular effects of GABA. Neither bicuculline nor picrotoxin pretreatment prevented the 'excitatory' cardiovascular effect of i.v. GABA in reserpine pretreated, guinea-pigs anaesthetized with barbitone. In adrenalectomized guinea-pigs or in preparations receiving i.v. phentolamine plus propranolol, GABA produced only a small 'depressant' effect on cardiovascular parameters. These findings

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

    SciTech Connect

    Vaccarino, F.; Guidotti, A.

    1987-05-01

    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.

  12. GABA (γ-Aminobutyric Acid) Uptake Via the GABA Permease GabP Represses Virulence Gene Expression in Pseudomonas syringae pv. tomato DC3000.

    PubMed

    McCraw, S L; Park, D H; Jones, R; Bentley, M A; Rico, A; Ratcliffe, R G; Kruger, N J; Collmer, A; Preston, G M

    2016-12-01

    The nonprotein amino acid γ-aminobutyric acid (GABA) is the most abundant amino acid in the tomato (Solanum lycopersicum) leaf apoplast and is synthesized by Arabidopsis thaliana in response to infection by the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (hereafter called DC3000). High levels of exogenous GABA have previously been shown to repress the expression of the type III secretion system (T3SS) in DC3000, resulting in reduced elicitation of the hypersensitive response (HR) in the nonhost plant tobacco (Nicotiana tabacum). This study demonstrates that the GABA permease GabP provides the primary mechanism for GABA uptake by DC3000 and that the gabP deletion mutant ΔgabP is insensitive to GABA-mediated repression of T3SS expression. ΔgabP displayed an enhanced ability to elicit the HR in young tobacco leaves and in tobacco plants engineered to produce increased levels of GABA, which supports the hypothesis that GABA uptake via GabP acts to regulate T3SS expression in planta. The observation that P. syringae can be rendered insensitive to GABA through loss of gabP but that gabP is retained by this bacterium suggests that GabP is important for DC3000 in a natural setting, either for nutrition or as a mechanism for regulating gene expression. [Formula: see text] Copyright © 2016 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

  13. The role of the GABA system in amphetamine-type stimulant use disorders

    PubMed Central

    Jiao, Dongliang; liu, Yao; Li, Xiaohong; liu, Jinggen; Zhao, Min

    2015-01-01

    Abuse of amphetamine-type stimulants (ATS) has become a global public health problem. ATS causes severe neurotoxicity, which could lead to addiction and could induce psychotic disorders or cognitive dysfunctions. However, until now, there has been a lack of effective medicines for treating ATS-related problems. Findings from recent studies indicate that in addition to the traditional dopamine-ergic system, the GABA (gamma-aminobutyric acid)-ergic system plays an important role in ATS abuse. However, the exact mechanisms of the GABA-ergic system in amphetamine-type stimulant use disorders are not fully understood. This review discusses the role of the GABA-ergic system in ATS use disorders, including ATS induced psychotic disorders and cognitive dysfunctions. We conclude that the GABA-ergic system are importantly involved in the development of ATS use disorders through multiple pathways, and that therapies or medicines that target specific members of the GABA-ergic system may be novel effective interventions for the treatment of ATS use disorders. PMID:25999814

  14. Production of gaba (γ – Aminobutyric acid) by microorganisms: a review

    PubMed Central

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

    2012-01-01

    GABA (γ-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. PMID:24031948

  15. Unsaturated phosphinic analogues of gamma-aminobutyric acid as GABA(C) receptor antagonists.

    PubMed

    Chebib, M; Vandenberg, R J; Froestl, W; Johnston, G A

    1997-06-25

    The phosphinic and methylphosphinic analogues of gamma-aminobutyric acid (GABA) are potent GABA(C) receptor antagonists but are even more potent as GABA(B) receptor agonists. Conformationally restricted unsaturated phosphinic and methylphosphinic analogues of GABA and some potent GABA(B) receptor phosphonoamino acid antagonists were tested on GABA(C) receptors in Xenopus oocytes expressing human retinal rho1 mRNA. 3-Aminopropyl-n-butyl-phosphinic acid (CGP36742), an orally active GABA(B) receptor antagonist, was found to be a moderately potent GABA(C) receptor antagonist (IC50 = 62 microM). The unsaturated methylphosphinic and phosphinic analogues of GABA were competitive antagonists of the GABA(C) receptors, the order of potency being [(E)-3-aminopropen-1-yl]methylphosphinic acid (CGP44530, IC50 = 5.53 microM) > [(E)-3-aminopropen-1-yl]phosphinic acid (CGP38593, IC50 = 7.68 microM) > [(Z)-3-aminopropen-1-yl]methylphosphinic acid (CGP70523, IC50 = 38.94 microM) > [(Z)-3-aminopropen-1-yl]phosphinic acid (CGP70522, IC50 > 100 microM). This order of potency differs from that reported for these compounds as GABA(B) receptor agonists, where the phosphinic acids are more potent than the corresponding methylphosphinic acids.

  16. Increased GABA concentrations in type 2 diabetes mellitus are related to lower cognitive functioning

    PubMed Central

    van Bussel, Frank C.G.; Backes, Walter H.; Hofman, Paul A.M.; Puts, Nicolaas A.J.; Edden, Richard A.E.; van Boxtel, Martin P.J.; Schram, Miranda T.; Stehouwer, Coen D.A.; Wildberger, Joachim E.; Jansen, Jacobus F.A.

    2016-01-01

    Abstract Type 2 diabetes mellitus is associated with accelerated cognitive decline. The underlying pathophysiological mechanisms still remain to be elucidated although it is known that insulin signaling modulates neurotransmitter activity, including inhibitory γ-aminobutyric acid (GABA) and excitatory glutamate (Glu) receptors. Therefore, we examined whether levels of GABA and Glu are related to diabetes status and cognitive performance. Forty-one participants with type 2 diabetes and 39 participants without type 2 diabetes underwent detailed cognitive assessments and 3-Tesla proton MR spectroscopy. The associations of neurotransmitters with type 2 diabetes and cognitive performance were examined using multivariate regression analyses controlling for age, sex, education, BMI, and percentage gray/white matter ratio in spectroscopic voxel. Analysis revealed higher GABA+ levels in participants with type 2 diabetes, in participants with higher fasting blood glucose levels and in participants with higher HbA1c levels, and higher GABA+ levels in participants with both high HbA1c levels and less cognitive performance. To conclude, participants with type 2 diabetes have alterations in the GABAergic neurotransmitter system, which are related to lower cognitive functioning, and hint at the involvement of an underlying metabolic mechanism. PMID:27603392

  17. Effect of centrally acting drugs on the uptake of γ-aminobutyric acid (GABA) by slices of rat cerebral cortex

    PubMed Central

    Harris, M.; Hopkin, Judy M.; Neal, M. J.

    1973-01-01

    1. The effects of centrally acting drugs on the uptake of 3H-γ-aminobutyric acid (GABA) by slices of rat cerebral cortex have been studied. 2. Many centrally acting drugs at concentrations of 0·1-1·0 mM significantly inhibited the uptake of 3H-GABA by cortical slices, but the only classes of drugs in which all members consistently produced inhibition of uptake were the phenothiazines, tricyclic antidepressants, and butyrophenones. 3. The receptor blocking drugs; phentolamine, propranolol, thymoxamine, mepyramine, and diphenhydramine at concentrations of 0·5-1 mM also significantly reduced the uptake of 3H-GABA. However, atropine, hexamethonium and (+)-tubocurarine had little effect on the uptake of 3H-GABA by cortical slices. 4. Centrally acting drugs, which did not significantly inhibit 3H-GABA uptake, included barbiturates, local anaesthetics, hallucinogens, monoamine oxidase inhibitors, anticonvulsants, and convulsants (except picrotoxin). 5. Chlorpromazine, prochlorperazine, L-2,4,diaminobutyric acid, desmethylimipramine, and iprindole inhibited the uptake of 3H-GABA by 50% (IC50) at concentrations of 30-100 μM. The most potent inhibitor of 3H-GABA uptake was p-chloromercuriphenylsulphonate (IC50 = 18 μM). 6. With the exception of L-2,4,diaminobutyric acid, an outstanding characteristic of these drugs was their complete lack of specificity. Thus at the IC50 for GABA, p-chloromercuriphenylsulphonate, chlorpromazine, prochlorperazine, iprindole, desmethylimipramine, apomorphine and diphenylhydramine also inhibited the uptake of radioactive glycine, alanine, noradrenaline, and 5-hydroxytryptamine. The uptake of the latter two compounds was often inhibited to a greater extent than GABA, glycine and alanine. 7. Kinetic analysis indicated that the inhibition of 3H-GABA by p-chloromercuriphenylsulphonate, chlorpromazine, and desmethylimipramine was noncompetitive. L-2,4,Diaminobutyric acid reduced the uptake of 3H-GABA by a `mixed' type of inhibition. 8. The

  18. 5-HT and GABA modulate intrinsic excitability of type I interneurons in Hermissenda.

    PubMed

    Jin, Nan Ge; Tian, Lian-Ming; Crow, Terry

    2009-11-01

    The sensory neurons (photoreceptors) in the visual system of Hermissenda are one site of plasticity produced by Pavlovian conditioning. A second site of plasticity produced by conditioning is the type I interneurons in the cerebropleural ganglia. Both photoreceptors and statocyst hair cells of the graviceptive system form monosynaptic connections with identified type I interneurons. Two proposed neurotransmitters in the graviceptive system, serotonin (5-HT) and gamma-aminobutyric acid (GABA), have been shown to modify synaptic strength and intrinsic neuronal excitability in identified photoreceptors. However, the potential role of 5-HT and GABA in plasticity of type I interneurons has not been investigated. Here we show that 5-HT increased the peak amplitude of light-evoked complex excitatory postsynaptic potentials (EPSPs), enhanced intrinsic excitability, and increased spike activity of identified type I(e(A)) interneurons. In contrast, 5-HT decreased spike activity and intrinsic excitability of type I(e(B)) interneurons. The classification of two categories of type I(e) interneurons was also supported by the observation that 5-HT produced opposite effects on whole cell steady-state outward currents in type I(e) interneurons. Serotonin produced a reduction in the amplitude of light-evoked complex inhibitory PSPs (IPSPs), increased spontaneous spike activity, decreased intrinsic excitability, and depolarized the resting membrane potential of identified type I(i) interneurons. In contrast to the effects of 5-HT, GABA produced inhibition in both types of I(e) interneurons and type I(i) interneurons. These results show that 5-HT and GABA can modulate the intrinsic excitability of type I interneurons independent of the presynaptic effects of the same transmitters on excitability and synaptic efficacy of photoreceptors.

  19. 5-HT and GABA Modulate Intrinsic Excitability of Type I Interneurons in Hermissenda

    PubMed Central

    Jin, Nan Ge; Tian, Lian-Ming

    2009-01-01

    The sensory neurons (photoreceptors) in the visual system of Hermissenda are one site of plasticity produced by Pavlovian conditioning. A second site of plasticity produced by conditioning is the type I interneurons in the cerebropleural ganglia. Both photoreceptors and statocyst hair cells of the graviceptive system form monosynaptic connections with identified type I interneurons. Two proposed neurotransmitters in the graviceptive system, serotonin (5-HT) and γ-aminobutyric acid (GABA), have been shown to modify synaptic strength and intrinsic neuronal excitability in identified photoreceptors. However, the potential role of 5-HT and GABA in plasticity of type I interneurons has not been investigated. Here we show that 5-HT increased the peak amplitude of light-evoked complex excitatory postsynaptic potentials (EPSPs), enhanced intrinsic excitability, and increased spike activity of identified type Ie(A) interneurons. In contrast, 5-HT decreased spike activity and intrinsic excitability of type Ie(B) interneurons. The classification of two categories of type Ie interneurons was also supported by the observation that 5-HT produced opposite effects on whole cell steady-state outward currents in type Ie interneurons. Serotonin produced a reduction in the amplitude of light-evoked complex inhibitory PSPs (IPSPs), increased spontaneous spike activity, decreased intrinsic excitability, and depolarized the resting membrane potential of identified type Ii interneurons. In contrast to the effects of 5-HT, GABA produced inhibition in both types of Ie interneurons and type Ii interneurons. These results show that 5-HT and GABA can modulate the intrinsic excitability of type I interneurons independent of the presynaptic effects of the same transmitters on excitability and synaptic efficacy of photoreceptors. PMID:19710377

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

    PubMed Central

    Goldberg, Joel S.

    2010-01-01

    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. PMID:20703328

  1. Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans.

    PubMed

    Abdou, Adham M; Higashiguchi, S; Horie, K; Kim, Mujo; Hatta, H; Yokogoshi, H

    2006-01-01

    The effect of orally administrated gamma-aminobutyric acid (GABA) on relaxation and immunity during stress has been investigated in humans. Two studies were conducted. The first evaluated the effect of GABA intake by 13 subjects on their brain waves. Electroencephalograms (EEG) were obtained after 3 tests on each volunteer as follows: intake only water, GABA, or L-theanine. After 60 minutes of administration, GABA significantly increases alpha waves and decreases beta waves compared to water or L-theanine. These findings denote that GABA not only induces relaxation but also reduces anxiety. The second study was conducted to see the role of relaxant and anxiolytic effects of GABA intake on immunity in stressed volunteers. Eight acrophobic subjects were divided into 2 groups (placebo and GABA). All subjects were crossing a suspended bridge as a stressful stimulus. Immunoglobulin A (IgA) levels in their saliva were monitored during bridge crossing. Placebo group showed marked decrease of their IgA levels, while GABA group showed significantly higher levels. In conclusion, GABA could work effectively as a natural relaxant and its effects could be seen within 1 hour of its administration to induce relaxation and diminish anxiety. Moreover, GABA administration could enhance immunity under stress conditions.

  2. Unsaturated Analogues of the Neurotransmitter GABA: trans-4-Aminocrotonic, cis-4-Aminocrotonic and 4-Aminotetrolic Acids.

    PubMed

    Johnston, Graham A R

    2016-03-01

    Analogues of the neurotransmitter GABA containing unsaturated bonds are restricted in the conformations they can attain. This review traces three such analogues from their synthesis to their use as neurochemicals. trans-4-Aminocrotonic acid was the first conformationally restricted analogue to be extensively studied. It acts like GABA across a range of macromolecules from receptors to transporters. It acts similarly to GABA on ionotropic receptors. cis-4-Aminocrotonic acid selectively activates bicuculline-insensitive GABAC receptors. 4-Aminotetrolic acid, containing a triple bond, activates bicuculline-sensitive GABAA receptors. These findings indicate that GABA activates GABAA receptors in extended conformations and GABAC receptors in folded conformations. These and related analogues are important for the molecular modelling of ionotropic GABA receptors and to the development of new agents acting selectively on these receptors.

  3. A functional role for both γ-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

    Kersanté, Flavie; Rowley, Samuel C S; Pavlov, Ivan; Gutièrrez-Mecinas, María; Semyanov, Alexey; Reul, Johannes M H M; Walker, Matthew C; Linthorst, Astrid C E

    2013-01-01

    Tonic γ-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. PMID:23381899

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

    PubMed

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

    2014-03-01

    The current study investigated the γ-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 β-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. β-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 β-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 β-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 β-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 β-cypermethrin contributed to increased GABA levels in the mouse brain. The downregulated GABAA receptors mRNA expression is most likely a downstream event.

  5. In vivo blockade of thalamic GABA(B) receptors increases excitatory amino-acid levels.

    PubMed

    Nyitrai, G; Emri, Z; Crunelli, V; Kékesi, K A; Dobolyi, A; Juhász, G

    1996-12-30

    The effect of intrathalamic application of GABA(B) receptor antagonists on the basal excitatory amino-acid levels was studied using microdialysis probes implanted in the dorsal lateral geniculate nucleus and in the ventrobasal complex. In both nuclei, continuous perfusion of the GABA(B) receptor antagonist 3-aminopropyl-(diethoxymethyl)-phosphinic acid (CGP 35348) produced an increase in the extracellular concentration of aspartate and (to a lesser extent) glutamate, but no change was observed in the level of taurine, the main amino acid involved in the regulation of brain osmolarity processes. In contrast, 3-amino-2-hydroxy-2-(4-chlorophenyl)-propanesulphonic acid (2-hydroxy-saclofen), another GABA(B) receptor antagonist, failed to affect the extracellular concentration of aspartate, glutamate and taurine. Thus, the basal level of excitatory amino acids in the thalamus in vivo is under the control of CGP 35348-sensitive GABA(B) receptors.

  6. Excitatory action of gamma-aminobutyric acid (GABA) on crustacean neurosecretory cells.

    PubMed

    García, U; Onetti, C; Valdiosera, R; Aréchiga, H

    1994-02-01

    1. Intracellular and voltage-clamp recordings were obtained from a selected population of neurosecretory (ns) cells in the X organ of the crayfish isolated eyestalk. Pulses of gamma-aminobutyric acid (GABA) elicited depolarizing responses and bursts of action potentials in a dose-dependent manner. These effects were blocked by picrotoxin (50 microM) but not by bicuculline. Picrotoxin also suppressed spontaneous synaptic activity. 2. The responses to GABA were abolished by severing the neurite of X organ cells, at about 150 microns from the cell body. Responses were larger when the application was made at the neuropil level. 3. Topical application of Cd2+ (2 mM), while suppressing synaptic activity, was incapable of affecting the responses to GABA. 4. Under whole-cell voltage-clamp, GABA elicited an inward current with a reversal potential dependent on the chloride equilibrium potential. The GABA effect was accompanied by an input resistance reduction up to 33% at a -50 mV holding potential. No effect of GABA was detected on potassium, calcium, and sodium currents present in X organ cells. 5. The effect of GABA on steady-state currents was dependent on the intracellular calcium concentration. At 10(-6) M [Ca2+]i, GABA (50 microM) increased the membrane conductance more than threefold and shifted the zero-current potential from -25 to -10 mV. At 10(-9) M [Ca2+]i, GABA induced only a 1.3-fold increase in membrane conductance, without shifting the zero-current potential. 6. These results support the notion that in the population of X organ cells sampled in this study, GABA acts as an excitatory neurotransmitter, opening chloride channels.

  7. Characterization of the type of calcium channel primarily regulating GABA exocytosis from brain nerve endings.

    PubMed

    Sitges, M; Chiu, L M

    1995-09-01

    In an attempt to further characterize the type of Ca2+ channels primarily regulating GABA exocytosis, the effects of increasing concentrations of omega CTx MVIIC,-omega-Aga IVA and other Ca2+ channel blockers (nitrendipine, Cd2+ and Ni2+), commonly used for pharmacologically discerning among the various types of Ca2+ channels, were tested on the dissected Ca2+ dependent fraction of the depolarization evoked release of GABA from mouse brain synaptosomes. Our results show that omega-CTx MVIIC inhibits GABA exocytosis with a calculated IC50 of 3 microM and omega-Aga IVA with a calculated IC50 of 50 nM. The divalent cation Cd2+ only diminishes GABA exocytosis at 70 microM, but does not modify this response at lower concentrations (i.e. 1 and 10 microM). Neither nitrendipine (10 microM) nor Ni2+ (100 microM and 500 microM) modified GABA exocytosis. The failure of nitrendipine at a high concentration to inhibit GABA exocytosis discards L-type Ca2+ channels as the main regulators of this response; likewise that of Ni2+ discards Ca2+ channels of the N-type, and the failure of nM concentrations of omega-CTx MVIIC or 500 microM Ni2+, also discards alpha 1A/Q-type Ca2+ channels as the main regulators of the GABA response. On the basis of these results and in particular of the higher potency of omega-Aga IVA than omega-CTx MVIIC, it is concluded that the type of Ca2+ channels that primarily determine the exocytosis of GABA belong to a P-like type of Ca2+ channels.

  8. Contents of Neo-flavored Tea (GABA Kintaro) Containing γ-Aminobutyric Acid

    NASA Astrophysics Data System (ADS)

    Shiraki, Yoshiya

    The contents of γ-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.

  9. (3-Aminocyclopentyl)methylphosphinic acids: novel GABA(C) receptor antagonists.

    PubMed

    Chebib, Mary; Hanrahan, Jane R; Kumar, Rohan J; Mewett, Kenneth N; Morriss, Gwendolyn; Wooller, Soraya; Johnston, Graham A R

    2007-03-01

    Our understanding of the role GABA(C) receptors play in the central nervous system is limited due to a lack of specific ligands. Here we describe the pharmacological effects of (+/-)-cis-3- and (+/-)-trans-3-(aminocyclopentyl)methylphosphinic acids ((+/-)-cis- and (+/-)-trans-3-ACPMPA) as novel ligands for the GABA(C) receptor showing little activity at GABA(A) or GABA(B) receptors. (+/-)-cis-3-ACPMPA has similar potency to (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) at human recombinant rho1 (K(B)=1.0+/-0.2microM) and rat rho3 (K(B)=5.4+/-0.8microM) but is 15 times more potent than TPMPA on human recombinant rho2 (K(B)=1.0+/-0.3microM) GABA(C) receptors expressed in Xenopus oocytes. (+/-)-cis- and (+/-)-trans-3-ACPMPA are novel lead compounds for developing into more potent and selective GABA(C) receptor antagonists with increased lipophilicity for in vivo studies.

  10. GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis.

    PubMed

    Gallardo, W G; Hagiwara, A; Hara, K; Soyano, K; Snell, T W

    2000-11-01

    gamma-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids.

  11. Metabolic pathways regulated by γ-aminobutyric acid (GABA) contributing to heat tolerance in creeping bentgrass (Agrostis stolonifera)

    PubMed Central

    Li, Zhou; Yu, Jingjin; Peng, Yan; Huang, Bingru

    2016-01-01

    γ-Aminobutyric acid is a non-protein amino acid involved in various metabolic processes. The objectives of this study were to examine whether increased GABA could improve heat tolerance in cool-season creeping bentgrass through physiological analysis, and to determine major metabolic pathways regulated by GABA through metabolic profiling. Plants were pretreated with 0.5 mM GABA or water before exposed to non-stressed condition (21/19 °C) or heat stress (35/30 °C) in controlled growth chambers for 35 d. The growth and physiological analysis demonstrated that exogenous GABA application significantly improved heat tolerance of creeping bentgrass. Metabolic profiling found that exogenous application of GABA led to increases in accumulations of amino acids (glutamic acid, aspartic acid, alanine, threonine, serine, and valine), organic acids (aconitic acid, malic acid, succinic acid, oxalic acid, and threonic acid), sugars (sucrose, fructose, glucose, galactose, and maltose), and sugar alcohols (mannitol and myo-inositol). These findings suggest that GABA-induced heat tolerance in creeping bentgrass could involve the enhancement of photosynthesis and ascorbate-glutathione cycle, the maintenance of osmotic adjustment, and the increase in GABA shunt. The increased GABA shunt could be the supply of intermediates to feed the tricarboxylic acid cycle of respiration metabolism during a long-term heat stress, thereby maintaining metabolic homeostasis. PMID:27455877

  12. Metabolic pathways regulated by γ-aminobutyric acid (GABA) contributing to heat tolerance in creeping bentgrass (Agrostis stolonifera).

    PubMed

    Li, Zhou; Yu, Jingjin; Peng, Yan; Huang, Bingru

    2016-07-26

    γ-Aminobutyric acid is a non-protein amino acid involved in various metabolic processes. The objectives of this study were to examine whether increased GABA could improve heat tolerance in cool-season creeping bentgrass through physiological analysis, and to determine major metabolic pathways regulated by GABA through metabolic profiling. Plants were pretreated with 0.5 mM GABA or water before exposed to non-stressed condition (21/19 °C) or heat stress (35/30 °C) in controlled growth chambers for 35 d. The growth and physiological analysis demonstrated that exogenous GABA application significantly improved heat tolerance of creeping bentgrass. Metabolic profiling found that exogenous application of GABA led to increases in accumulations of amino acids (glutamic acid, aspartic acid, alanine, threonine, serine, and valine), organic acids (aconitic acid, malic acid, succinic acid, oxalic acid, and threonic acid), sugars (sucrose, fructose, glucose, galactose, and maltose), and sugar alcohols (mannitol and myo-inositol). These findings suggest that GABA-induced heat tolerance in creeping bentgrass could involve the enhancement of photosynthesis and ascorbate-glutathione cycle, the maintenance of osmotic adjustment, and the increase in GABA shunt. The increased GABA shunt could be the supply of intermediates to feed the tricarboxylic acid cycle of respiration metabolism during a long-term heat stress, thereby maintaining metabolic homeostasis.

  13. γ-Aminobutyric acid (GABA) administration improves action selection processes: a randomised controlled trial

    PubMed Central

    Steenbergen, Laura; Sellaro, Roberta; Stock, Ann-Kathrin; Beste, Christian; Colzato, Lorenza S.

    2015-01-01

    In order to accomplish a task goal, real-life environments require us to develop different action control strategies in order to rapidly react to fast-moving visual and auditory stimuli. When engaging in complex scenarios, it is essential to prioritise and cascade different actions. Recent studies have pointed to an important role of the gamma-aminobutyric acid (GABA)-ergic system in the neuromodulation of action cascading. In this study we assessed the specific causal role of the GABA-ergic system in modulating the efficiency of action cascading by administering 800 mg of synthetic GABA or 800 mg oral of microcrystalline cellulose (placebo). In a double-blind, randomised, between-group design, 30 healthy adults performed a stop-change paradigm. Results showed that the administration of GABA, compared to placebo, increased action selection when an interruption (stop) and a change towards an alternative response were required simultaneously, and when such a change had to occur after the completion of the stop process. These findings, involving the systemic administration of synthetic GABA, provide the first evidence for a possible causal role of the GABA-ergic system in modulating performance in action cascading. PMID:26227783

  14. Determination of theanine, GABA, and other amino acids in green, oolong, black, and Pu-erh teas with dabsylation and high-performance liquid chromatography.

    PubMed

    Syu, Kai-Yang; Lin, Chih-Li; Huang, Hsiu-Chen; Lin, Jen-Kun

    2008-09-10

    Dabsyl chloride (dimethylaminoazobenzene sulfonyl chloride), a useful chromophoric labeling reagent for amino acids and amines, was developed in this laboratory in 1975. Although several methods have been developed to determine various types of amino acids, a quick and easy method of determining theanine, GABA, and other amino acids has not been developed in one HPLC system. In this paper are analyzed the free amino acid contents of theanine and GABA in different teas (green tea, black tea, oolong tea, Pu-erh tea, and GABA tea) with a dabsylation and reverse phase high-performance liquid chromatography (HPLC) system coupled with a detector at 425 nm absorbance. Two reverse phase columns, Hypersil GOLD and Zorbax ODS, were used and gave different resolutions of dabsyl amino acids in the gradient elution program. The data suggest that the tea source or the steps of tea-making may contribute to the theanine contents variations. High theanine contents of high-mountain tea were observed in both green tea and oolong tea. Furthermore, the raw (natural fermented) Pu-erh tea contained more theanine than ripe (wet fermented) Pu-erh tea, and the GABA contents in normal teas were generally lower than that in GABA tea.

  15. Activity-dependent transport of GABA analogues into specific cell types demonstrated at high resolution using a novel immunocytochemical strategy.

    PubMed

    Pow, D V; Baldridge, W; Crook, D K

    1996-08-01

    We have raised antisera against the GABA analogues gamma-vinyl GABA, diaminobutyric acid and gabaculine. These analogues are thought to be substrates for high-affinity GABA transporters. Retinae were exposed to micromolar concentrations of these analogues in the presence or absence of uptake inhibitors and then fixed and processed for immunocytochemistry at the light and electron microscopic levels. Immunolabelling for gamma-vinyl GABA revealed specific labelling of GABAergic amacrine cells and displaced amacrine cells in retinae of rabbits, cats, chickens, fish and a monkey. GABA-containing horizontal cells of cat and monkey retinae failed to exhibit labelling for gamma-vinyl GABA, suggesting that they lacked an uptake system for this molecule. In light-adapted fish, gamma-vinyl GABA was readily detected in H1 horizontal cells; similar labelling was also observed in light-adapted chicken retinae. The pattern of labelling in the fish and chicken retinae was modified by dark adaptation, when labelling was greatly reduced in the horizontal cells, indicating the activity dependence of GABA (analogue) transport. Intraperitoneal injection of gamma-vinyl GABA into rats resulted in its transport across the blood-brain barrier and subsequent uptake into populations of GABAergic neurons. The other analogues investigated in this study exhibited different patterns of transport; gabaculine was taken up into glial cells, whilst diaminobutyric acid was taken up into neurons, glial cells and retinal pigment epithelia. Thus, these analogues are probably substrates for different GABA transporters. We conclude that immunocytochemical detection of the high-affinity uptake of gamma-vinyl GABA permits the identification of GABAergic neurons which are actively transporting GABA, and suggest that this novel methodology will be a useful tool in rapidly assessing the recent activity of GABAergic neurons at the cellular level.

  16. Conversion into GABA (gamma-aminobutyric acid) may reduce the capacity of L-glutamine as an insulin secretagogue.

    PubMed Central

    Fernández-Pascual, Sergio; Mukala-Nsengu-Tshibangu, André; Martín Del Río, Rafael; Tamarit-Rodríguez, Jorge

    2004-01-01

    We have carried out a detailed examination of L-glutamine metabolism in rat islets in order to elucidate the paradoxical failure of L-glutamine to stimulate insulin secretion. L-Glutamine was converted by isolated islets into GABA (gamma-aminobutyric acid), L-aspartate and L-glutamate. Saturation of the intracellular concentrations of all of these amino acids occurred at approx. 10 mmol/l L-glutamine, and their half-maximal values were attained at progressively increasing concentrations of L-glutamine (0.3 mmol/l for GABA; 0.5 and 1.0 mmol/l for Asp and Glu respectively). GABA accumulation accounted for most of the 14CO2 produced at various L-[U-14C]glutamine concentrations. Potentiation by L-glutamine of L-leucine-induced insulin secretion in perifused islets was suppressed by malonic acid dimethyl ester, was accompanied by a significant decrease in islet GABA accumulation, and was not modified in the presence of GABA receptor antagonists [50 micromol/l saclofen or 10 micromol/l (+)-bicuculline]. L-Leucine activated islet glutamate dehydrogenase activity, but had no effect on either glutamate decarboxylase or GABA transaminase activity, in islet homogenates. We conclude that (i) L-glutamine is metabolized preferentially to GABA and L-aspartate, which accumulate in islets, thus preventing its complete oxidation in the Krebs cycle, which accounts for its failure to stimulate insulin secretion; (ii) potentiation by L-glutamine of L-leucine-induced insulin secretion involves increased metabolism of L-glutamate and GABA via the Krebs cycle (glutamate dehydrogenase activation) and the GABA shunt (2-oxoglutarate availability for GABA transaminase) respectively, and (iii) islet release of GABA does not seem to play an important role in the modulation of the islet secretory response to the combination of L-leucine and L-glutamine. PMID:14763900

  17. Conversion into GABA (gamma-aminobutyric acid) may reduce the capacity of L-glutamine as an insulin secretagogue.

    PubMed

    Fernández-Pascual, Sergio; Mukala-Nsengu-Tshibangu, André; Martín Del Río, Rafael; Tamarit-Rodríguez, Jorge

    2004-05-01

    We have carried out a detailed examination of L-glutamine metabolism in rat islets in order to elucidate the paradoxical failure of L-glutamine to stimulate insulin secretion. L-Glutamine was converted by isolated islets into GABA (gamma-aminobutyric acid), L-aspartate and L-glutamate. Saturation of the intracellular concentrations of all of these amino acids occurred at approx. 10 mmol/l L-glutamine, and their half-maximal values were attained at progressively increasing concentrations of L-glutamine (0.3 mmol/l for GABA; 0.5 and 1.0 mmol/l for Asp and Glu respectively). GABA accumulation accounted for most of the 14CO2 produced at various L-[U-14C]glutamine concentrations. Potentiation by L-glutamine of L-leucine-induced insulin secretion in perifused islets was suppressed by malonic acid dimethyl ester, was accompanied by a significant decrease in islet GABA accumulation, and was not modified in the presence of GABA receptor antagonists [50 micromol/l saclofen or 10 micromol/l (+)-bicuculline]. L-Leucine activated islet glutamate dehydrogenase activity, but had no effect on either glutamate decarboxylase or GABA transaminase activity, in islet homogenates. We conclude that (i) L-glutamine is metabolized preferentially to GABA and L-aspartate, which accumulate in islets, thus preventing its complete oxidation in the Krebs cycle, which accounts for its failure to stimulate insulin secretion; (ii) potentiation by L-glutamine of L-leucine-induced insulin secretion involves increased metabolism of L-glutamate and GABA via the Krebs cycle (glutamate dehydrogenase activation) and the GABA shunt (2-oxoglutarate availability for GABA transaminase) respectively, and (iii) islet release of GABA does not seem to play an important role in the modulation of the islet secretory response to the combination of L-leucine and L-glutamine.

  18. Abnormal relationship between GABA, neurophysiology and impulsive behavior in neurofibromatosis type 1.

    PubMed

    Ribeiro, Maria J; Violante, Inês R; Bernardino, Inês; Edden, Richard A E; Castelo-Branco, Miguel

    2015-03-01

    Neurofibromatosis type 1 (NF1) is a neurodevelopmental disorder characterized by a broad spectrum of cognitive deficits. In particular, executive dysfunction is recognized as a core deficit of NF1, including impairments in executive attention and inhibitory control. Yet, the neural mechanisms behind these important deficits are still unknown. Here, we studied inhibitory control in a visual go/no-go task in children and adolescents with NF1 and age- and gender-matched controls (n = 16 per group). We applied a multimodal approach using high-density electroencephalography (EEG), to study the evoked brain responses, and magnetic resonance spectroscopy (MRS) to measure the levels of GABA and glutamate + glutamine in the medial frontal cortex, a brain region that plays a pivotal role in inhibitory control, and also in a control region, the occipital cortex. Finally, we run correlation analyses to identify the relationship between inhibitory control, levels of neurotransmitters, and EEG markers of neural function. Individuals with NF1 showed impaired impulse control and reduced EEG correlates of early visual processing (parieto-occipital P1) and inhibitory control (frontal P3). MRS data revealed a reduction in medial frontal GABA+/tCr (total Creatine) levels in the NF1 group, in parallel with the already reported reduced occipital GABA levels. In contrast, glutamate + glutamine/tCr levels were normal, suggesting the existence of abnormal inhibition/excitation balance in this disorder. Notably, medial frontal but not occipital GABA levels correlated with general intellectual abilities (IQ) in NF1, and inhibitory control in both groups. Surprisingly, the relationship between inhibitory control and medial frontal GABA was reversed in NF1: higher GABA was associated with a faster response style whereas in controls it was related to a cautious strategy. Abnormal GABAergic physiology appears, thus, as an important factor underlying impaired cognition in NF1, in a level and

  19. Evidence for GABA-Induced Systemic GABA Accumulation in Arabidopsis upon Wounding

    PubMed Central

    Scholz, Sandra S.; Malabarba, Jaiana; Reichelt, Michael; Heyer, Monika; Ludewig, Frank; Mithöfer, Axel

    2017-01-01

    The non-proteinogenic amino acid γ-aminobutyric acid (GABA) is present in all plant species analyzed so far. Its synthesis is stimulated by either acidic conditions occurring after tissue disruption or higher cytosolic calcium level. In mammals, GABA acts as inhibitory neurotransmitter but its function in plants is still not well understood. Besides its involvement in abiotic stress resistance, GABA has a role in the jasmonate-independent defense against invertebrate pests. While the biochemical basis for GABA accumulation in wounded leaves is obvious, the underlying mechanisms for wounding-induced GABA accumulation in systemic leaves remained unclear. Here, the Arabidopsis thaliana knock-out mutant lines pop2-5, unable to degrade GABA, and tpc1-2, lacking a wounding-induced systemic cytosolic calcium elevation, were employed for a comprehensive investigation of systemic GABA accumulation. A wounding-induced systemic GABA accumulation was detected in tpc1-2 plants demonstrating that an increased calcium level was not involved. Similarly, after both mechanical wounding and Spodoptera littoralis feeding, GABA accumulation in pop2-5 plants was significantly higher in local and systemic leaves, compared to wild-type plants. Consequently, larvae feeding on these GABA-enriched mutant plants grew significantly less. Upon exogenous application of a D2-labeled GABA to wounded leaves of pop2-5 plants, its uptake but no translocation to unwounded leaves was detected. In contrast, an accumulation of endogenous GABA was observed in vascular connected systemic leaves. These results suggest that the systemic accumulation of GABA upon wounding does not depend on the translocation of GABA or on an increase in cytosolic calcium. PMID:28382046

  20. Gas release-based prescreening combined with reversed-phase HPLC quantitation for efficient selection of high-γ-aminobutyric acid (GABA)-producing lactic acid bacteria.

    PubMed

    Wu, Qinglong; Shah, Nagendra P

    2015-02-01

    High γ-aminobutyric acid (GABA)-producing lactobacilli are promising for the manufacture of GABA-rich foods and to synthesize GRAS (generally recognized as safe)-grade GABA. However, common chromatography-based screening is time-consuming and inefficient. In the present study, Korean kimchi was used as a model of lactic acid-based fermented foods, and a gas release-based prescreening of potential GABA producers was developed. The ability to produce GABA by potential GABA producers in de Man, Rogosa, and Sharpe medium supplemented with or without monosodium glutamate was further determined by HPLC. Based on the results, 9 isolates were regarded as high GABA producers, and were further genetically identified as Lactobacillus brevis based on the sequences of 16S rRNA gene. Gas release-based prescreening combined with reversed-phase HPLC confirmation was an efficient and cost-effective method to identify high-GABA-producing LAB, which could be good candidates for probiotics. The GABA that is naturally produced by these high-GABA-producing LAB could be used as a food additive.

  1. Calcium dependent release of gamma-aminobutyric acid (GABA) from human cerebral cortex.

    PubMed

    Haugstad, T S; Hegstad, E; Langmoen, I A

    1992-07-06

    The release of the amino acids GABA, taurine, glycine, glutamine and leucine from human neocortex was investigated in vitro by utilizing brain tissue removed during 8 standard temporal lobectomies for epilepsy or tumor. Slices (0.5 mm thick) were cut from each biopsy and randomly placed in three different chambers. After 90 min preincubation, the three sets of slices were incubated for 60 s in wells containing, respectively, (A) regular ACSF (control), (B) ACSF with 50 mM K+ (to depolarize the cell membrane) and (C) ACSF with 50 mM K+, 0 mM Ca2+ and 4 mM Mg2+ (depolarization during blocked synaptic transmission). The content of amino acids in the wells was determined by high-performance liquid chromatography after pre-column derivatization of the amino acids with o-phthalaldehyde. Membrane depolarization (well B) increased the GABA release to 650% (620 pmol/mg) of control (well A, 95 pmol/mg). Blocking synaptic transmission (well C) reduced the evoked release by 50% (360 pmol/mg). The release of glycine, taurine, glutamine and leucine during membrane depolarization was not significantly different from the control values. The data provide evidence for a Ca(2+)-dependent release of GABA, supporting a possible role of this amino acid as a neurotransmitter in human neocortex.

  2. GABA deficiency in NF1

    PubMed Central

    Patricio, Miguel; Bernardino, Inês; Rebola, José; Abrunhosa, Antero J.; Ferreira, Nuno; Castelo-Branco, Miguel

    2016-01-01

    Objective: To provide a comprehensive investigation of the γ-aminobutyric acid (GABA) system in patients with neurofibromatosis type 1 (NF1) that allows understanding the nature of the GABA imbalance in humans at pre- and postsynaptic levels. Methods: In this cross-sectional study, we employed multimodal imaging and spectroscopy measures to investigate GABA type A (GABAA) receptor binding, using [11C]-flumazenil PET, and GABA concentration, using magnetic resonance spectroscopy (MRS). Fourteen adult patients with NF1 and 13 matched controls were included in the study. MRS was performed in the occipital cortex and in a frontal region centered in the functionally localized frontal eye fields. PET and MRS acquisitions were performed in the same day. Results: Patients with NF1 have reduced concentration of GABA+ in the occipital cortex (p = 0.004) and frontal eye fields (p = 0.026). PET results showed decreased binding of GABAA receptors in patients in the parieto-occipital cortex, midbrain, and thalamus, which are not explained by decreased gray matter levels. Conclusions: Abnormalities in the GABA system in NF1 involve both GABA concentration and GABAA receptor density suggestive of neurodevelopmental synaptopathy with both pre- and postsynaptic involvement. PMID:27473134

  3. Interactions of pyrethroid insecticides with GABA sub A and peripheral-type benzodiazepine receptors

    SciTech Connect

    Devaud, L.L.

    1988-01-01

    Pyrethroid insecticides are potent proconvulsants in the rat. All pyrethroids evincing proconvulsant activity elicited a similar 25-30% maximal reduction of seizure threshold. The Type II pyrethroids were the most potent proconvulsants with 1R{alpha}S, cis cypermethrin having an ED{sub 50} value of 6.3 nmol/kg. The proconvulsant activity of both Type I and Type II pyrenthroids was blocked by pretreatment with PK 11195, the peripheral-type benzodiazepine receptor (PTBR) antagonist. In contrast, phenytoin did not antagonize the proconvulsant activity of either deltamethrin or permethrin. Pyrethroids displaced the specific binding of ({sup 3}H)Ro5-4864 to rat brain membranes with a significant correlation between the log EC{sub 50} values for their activities as proconvulsants and the log IC{sub 50} values for their inhibition of ({sup 3}H)Ro5-4864 binding. Both Ro5-4864 and pyrethroid insecticides were found to influence specific ({sup 35}S)TBPS binding in a GABA-dependent manner. PK 11195 and the Type II pyrethroid, deltamethrin antagonized the Ro5-4864-induced modulation of ({sup 35}S)TBPS binding. Pyrethroid insecticides, Ro5-4864 and veratridine influenced GABA-gated {sup 36}Chloride influx. Moreover, the Type II pyrethroids elicited an increase in {sup 36}chloride influx in the absence of GABA-stimulation. Both of these actions were antagonized by PK 11195 and tetrodotoxin.

  4. Guanidino acids act as rho1 GABA(C) receptor antagonists.

    PubMed

    Chebib, Mary; Gavande, Navnath; Wong, Kit Yee; Park, Anna; Premoli, Isabella; Mewett, Kenneth N; Allan, Robin D; Duke, Rujee K; Johnston, Graham A R; Hanrahan, Jane R

    2009-10-01

    GABA(C) receptors play a role in myopia, memory-related disorders and circadian rhythms signifying a need to develop potent and selective agents for this class of receptors. Guanidino analogs related to glycine, beta-alanine and taurine were evaluated at human rho(1)GABA(C) receptors expressed in Xenopus oocytes using 2-electrode voltage clamp methods. Of the 12 analogs tested, 8 analogs were active as antagonists and the remaining were inactive. (S)-2-guanidinopropionic acid (IC(50) = 2.2 microM) and guanidinoacetic acid (IC(50) = 5.4 microM; K (B) = 7.75 microM [pK (B) = 5.11 +/- 0.06]) were the most potent being competitive antagonists at this receptor. In contrast, the beta-alanine and GABA guanidino analogs showed reduced activity, indicating the distance between the carboxyl carbon and terminal nitrogen of the guanidino group is critical for activity. Substituting the C2-position of guanidinoacetic acid with various alkyl groups reduced activity indicating that steric effects may impact on activity. The results of this study contribute to the structure-activity-relationship profile required in developing novel therapeutic agents.

  5. Stimulation of [3H] GABA and beta-[3H] alanine release from rat brain slices by cis-4-aminocrotonic acid.

    PubMed

    Chebib, M; Johnston, G A

    1997-02-01

    cis-4-Aminocrotonic acid (CACA; 100 microM), an analogue of GABA in a folded conformation, stimulated the passive release of [3H] GABA from slices of rat cerebellum, cerebral cortex, retina, and spinal cord and of beta-[3H]alanine from slices of cerebellum and spinal cord without influencing potassium-evoked release. In contrast, CACA (100 microM) did not stimulate the passive release of [3H]taurine from slices of cerebellum and spinal cord or of D-[3H]aspartate from slices of cerebellum and did not influence potassium-evoked release of [3H]-taurine from the cerebellum and spinal cord and D-[3H]-aspartate from the cerebellum. These results suggest that the effects of CACA on GABA and beta-alanine release are due to CACA acting as a substrate for a beta-alanine-sensitive GABA transport system, consistent with CACA inhibiting the uptake of beta-[3H]alanine into slices of rat cerebellum and cerebral cortex. The observed Ki for CACA against beta-[3H]alanine uptake in the cerebellum was 750 +/- 60 microM. CACA appears to be 10-fold weaker as a substrate for the transporter system than as an agonist for the GABAc receptor. The effects of CACA on GABA and beta-alanine release provide indirect evidence for a GABA transporter in cerebellum, cerebral cortex, retina, and spinal cord that transports GABA, beta-alanine, CACA, and nipecotic acid that has a similar pharmacological profile to that of the GABA transporter, GAT-3, cloned from rat CNS. The structural similarities of GABA, beta-alanine, CACA, and nipecotic acid are demonstrated by computer-aided molecular modeling, providing information on the possible conformations of these substances being transported by a common carrier protein.

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

    PubMed

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

    2001-01-01

    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.

  7. The effect of experimental ischaemia and excitatory amino acid agonists on the GABA and serotonin immunoreactivities in the rabbit retina.

    PubMed

    Osborne, N N; Herrera, A J

    1994-04-01

    The aim of the described experiments was to use immunohistochemistry to visualize the release of GABA from specific retinal amacrine cells following ischaemia and to establish the involvement of defined glutamatergic receptors. In initial experiments, rabbit retinas were exposed in vitro to excitatory amino acid agonists alone or in combination with a putative antagonist, or in physiological solution lacking oxygen and glucose, or in solution containing potassium cyanide for 45 min at 37 degrees C. The nature of the GABA immunoreactivity was then examined by immunohistochemistry. In other in vitro experiments, retinas were first allowed to accumulate exogenous serotonin before exposing the tissues to the combinations as described. These tissues were then processed immunohistochemically for the localization of serotonin. In yet other experiments, the intraocular pressure of a rabbit's eye was raised to about 110 mmHg for 60 min and a reperfusion time of 45 min allowed before dissecting the retina and processing for the localization of GABA immunoreactivity. The other eye served as a control. Of the excitatory amino acid agonists tested, only N-methyl-D-aspartate, kainate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid caused a change in the GABA immunoreactivity. The N-methyl-D-aspartate effect was specifically antagonized by dizocilpine maleate, dextromethorphan and memantine, and was characterized by a reduction in the number of GABA-immunoreactive perikarya. The GABA "staining" in the inner plexiform layer also appeared as four clear bands. The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid- and kainate-induced effects were both antagonized by 6-cyano-2,3-dihydroxy-7-nitroquinoxaline-2,3-dione and partially by kynurenic acid at the concentrations used. Here, the amount of GABA-positive perikarya was greatly reduced and three immunoreactive bands appeared in the inner plexiform layer. However, for low concentrations of alpha-amino-3-hydroxy

  8. Efficient production of gamma-aminobutyric acid using Escherichia coli by co-localization of glutamate synthase, glutamate decarboxylase, and GABA transporter.

    PubMed

    Dung Pham, Van; Somasundaram, Sivachandiran; Lee, Seung Hwan; Park, Si Jae; Hong, Soon Ho

    2016-01-01

    Gamma-aminobutyric acid (GABA) is an important bio-product, which is used in pharmaceutical formulations, nutritional supplements, and biopolymer monomer. The traditional GABA process involves the decarboxylation of glutamate. However, the direct production of GABA from glucose is a more efficient process. To construct the recombinant strains of Escherichia coli, a novel synthetic scaffold was introduced. By carrying out the co-localization of glutamate synthase, glutamate decarboxylase, and GABA transporter, we redirected the TCA cycle flux to GABA pathway. The genetically engineered E. coli strain produced 1.08 g/L of GABA from 10 g/L of initial glucose. Thus, with the introduction of a synthetic scaffold, we increased GABA production by 2.2-fold. The final GABA concentration was increased by 21.8% by inactivating competing pathways.

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

    PubMed

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

    2013-06-01

    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.

  10. Neurons accumulating [3H]gamma-aminobutyric acid (GABA) in supragranular layers of cat primary auditory cortex (AI)

    PubMed

    Winer, J A

    1986-11-01

    The classes of neurons accumulating exogenously injected, tritiated gamma-aminobutyric acid [( 3H]GABA) were studied in the supragranular layers in the primary auditory field of the adult cat. The size, laminar locus, and somatodendritic profiles of labeled neurons were studied light microscopically in frozen- or Vibratome-sectioned, 30 micron thick material, and in semithin, 1-2 micron thick, plastic-embedded high-resolution autoradiographic preparations. The chief goals of the study were to determine which types of cells could be identified as accumulating [3H]GABA in layers I, II and III, and to establish possible relationships between these cells and neurons described in Golgi studies of these layers, and the neurons found, in parallel investigations of the connections of the primary auditory field, to participate as ipsilateral corticocortical and commissural cells of origin. The principal findings are: that neurons in every layer in the primary auditory field take up tritiated gamma-aminobutyric acid; that their Nissl-counterstained somata have a smaller average area, and a smaller range of areas, than do the unlabeled cells; that more than one type of labeled neuron-as defined by somatic size and shape, height:width ratios, and nuclear membrane morphology-could be identified in each layer; that none of the labeled neurons had a soma with a pyramidal configuration; that the labeled cells are comparable in size, shape, and laminar distribution to some populations of non-pyramidal ipsilateral corticocortical cells of origin in layers II and III, and perhaps to certain classes of commissurally projecting, layer III non-pyramidal neurons; and finally, that only a rather small proportion-perhaps 10% or less, except in layer I-of the supragranular cells appear to accumulate labeled material. With regard to the identity of particular classes of neurons accumulating silver grains above background in the individual layers, in layer I, 2 of the 4 types of neurons

  11. Effects of NaCl Replacement with Gamma-Aminobutyric acid (GABA) on the Quality Characteristics and Sensorial Properties of Model Meat Products

    PubMed Central

    Chun, Ji-Yeon; Cho, Hyung-Yong; Min, Sang-Gi

    2014-01-01

    This study investigated the effects of γ-aminobutylic acid (GABA) on the quality and sensorial properties of both the GABA/NaCl complex and model meat products. GABA/NaCl complex was prepared by spray-drying, and the surface dimensions, morphology, rheology, and saltiness were characterized. For model meat products, pork patties were prepared by replacing NaCl with GABA. For characteristics of the complex, increasing GABA concentration increased the surface dimensions of the complex. However, GABA did not affect the rheological properties of solutions containing the complex. The addition of 2% GABA exhibited significantly higher saltiness than the control (no GABA treatment). In the case of pork patties, sensory testing indicated that the addition of GABA decreased the saltiness intensity. Both the intensity of juiciness and tenderness of patties containing GABA also scored lower than the control, based on the NaCl reduction. These results were consistent with the quality characteristics (cooking loss and texture profile analysis). Nevertheless, overall acceptability of the pork patties showed that up to 1.5%, patties containing GABA did not significantly differ from the control. Consequently, the results indicated that GABA has a potential application in meat products, but also manifested a deterioration of quality by the NaCl reduction, which warrants further exploration. PMID:26761294

  12. Oxo-4-methylpentanoic acid directs the metabolism of GABA into the Krebs cycle in rat pancreatic islets.

    PubMed

    Hernández-Fisac, Inés; Fernández-Pascual, Sergio; Ortsäter, Henrik; Pizarro-Delgado, Javier; Martín del Río, Rafael; Bergsten, Peter; Tamarit-Rodriguez, Jorge

    2006-11-15

    OMP (oxo-4-methylpentanoic acid) stimulates by itself a biphasic secretion of insulin whereas L-leucine requires the presence of L-glutamine. L-Glutamine is predominantly converted into GABA (gamma-aminobutyric acid) in rat islets and L-leucine seems to promote its metabolism in the 'GABA shunt' [Fernández-Pascual, Mukala-Nsengu-Tshibangu, Martín del Río and Tamarit-Rodríguez (2004) Biochem. J. 379, 721-729]. In the present study, we have investigated how 10 mM OMP affects L-glutamine metabolism to uncover possible differences with L-leucine that might help to elucidate whether they share a common mechanism of stimulation of insulin secretion. In contrast with L-leucine, OMP alone stimulated a biphasic insulin secretion in rat perifused islets and decreased the islet content of GABA without modifying its extracellular release irrespective of the concentration of L-glutamine in the medium. GABA was transaminated to L-leucine whose intracellular concentration did not change because it was efficiently transported out of the islet cells. The L-[U-14C]-Glutamine (at 0.5 and 10.0 mM) conversion to 14CO2 was enhanced by 10 mM OMP within 30% and 70% respectively. Gabaculine (250 microM), a GABA transaminase inhibitor, suppressed OMP-induced oxygen consumption but not L-leucine- or glucose-stimulated respiration. It also suppressed the OMP-induced decrease in islet GABA content and the OMP-induced increase in insulin release. These results support the view that OMP promotes islet metabolism in the 'GABA shunt' generating 2-oxo-glutarate, in the branched-chain alpha-amino acid transaminase reaction, which would in turn trigger GABA deamination by GABA transaminase. OMP, but not L-leucine, suppressed islet semialdehyde succinic acid reductase activity and this might shift the metabolic flux of the 'GABA shunt' from gamma-hydroxybutyrate to succinic acid production.

  13. Effect of GABA on oxidative stress in the skeletal muscles and plasma free amino acids in mice fed high-fat diet.

    PubMed

    Xie, Z X; Xia, S F; Qiao, Y; Shi, Y H; Le, G W

    2015-06-01

    Increased levels of plasma free amino acids (pFAAs) can disturb the blood glucose levels in patients with obesity, diabetes mellitus and metabolic syndrome (MS) and are associated with enhanced protein oxidation. Oxidation of proteins, especially in the muscles, can promote protein degradation and elevate the levels of pFAAs. Gamma-aminobutyric acid (GABA), a food additive, can reduce high-fat diet (HFD)-induced hyperglycaemia; however, the mechanisms remain unclear. The aim of this study was to evaluate the effects of GABA on protein oxidation and pFAAs changes. One hundred male C57BL/6 mice were randomly divided into five groups that were fed with control diet, HFD and HFD supplied with 0.2%, 0.12% and 0.06% GABA in drinking water for 20 weeks respectively. HFD feeding led to muscular oxidative stress, protein oxidation, pFAA disorders, hyperglycaemia and augmented plasma GABA levels. Treatment with GABA restored normally fasting blood glucose level and dose-dependently inhibited body weight gains, muscular oxidation and protein degradation. While medium and low doses of GABA mitigated HFD-induced pFAA disorders, the high dose of GABA deteriorated the pFAA disorders. Medium dose of GABA increased the levels of GABA, but high dose of GABA reduced the levels of plasma GABA and increased the activity of succinic semialdehyde dehydrogenase in the liver. Therefore, treatment with GABA mitigated HFD-induced hyperglycaemia probably by repairing HFD-induced muscular oxidative stress and pFAA disorders in mice. Our data also suggest that an optimal dose of GABA is crucial for the prevention of excess GABA-related decrease in the levels of pFAA and GABA as well as obesity.

  14. Reproducibility and effect of tissue composition on cerebellar γ-aminobutyric acid (GABA) MRS in an elderly population.

    PubMed

    Long, Zaiyang; Dyke, Jonathan P; Ma, Ruoyun; Huang, Chaorui C; Louis, Elan D; Dydak, Ulrike

    2015-10-01

    MRS provides a valuable tool for the non-invasive detection of brain γ-aminobutyric acid (GABA) in vivo. GABAergic dysfunction has been observed in the aging cerebellum. The study of cerebellar GABA changes is of considerable interest in understanding certain age-related motor disorders. However, little is known about the reproducibility of GABA MRS in an aged population. Therefore, this study aimed to explore the feasibility and reproducibility of GABA MRS in the aged cerebellum at 3.0 T and to examine the effect of differing tissue composition on GABA measurements. MRI and (1)H MRS examinations were performed on 10 healthy elderly volunteers (mean age, 75.2 ± 6.5 years) using a 3.0-T Siemens Tim Trio scanner. Among them, five subjects were scanned twice to assess the short-term reproducibility. The MEGA-PRESS (Mescher-Garwood point-resolved spectroscopy) J-editing sequence was used for GABA detection in two volumes of interest (VOIs) in the left and right cerebellar dentate. MRS data processing and quantification were performed with LCModel 6.3-0L using two separate basis sets, generated from density matrix simulations using published values for chemical shifts and J couplings. Raw metabolite levels from LCModel outputs were corrected for cerebrospinal fluid contamination and relaxation. GABA-edited spectra yielded robust and stable GABA measurements with averaged intra-individual coefficients of variation for corrected GABA+ between 4.0 ± 2.8% and 13.4 ± 6.3%, and inter-individual coefficients of variation between 12.6% and 24.2%. In addition, there was a significant correlation between GABA+ obtained with the two LCModel basis sets. Overall, our results demonstrated the feasibility and reproducibility of cerebellar GABA-edited MRS at 3.0 T in an elderly population. This information might be helpful for studies using this technique to study GABA changes in normal or diseased aging brain, e.g. for power calculations and the interpretation of longitudinal

  15. Bacterial endotoxin inhibits LHRH secretion following the increased release of hypothalamic GABA levels. Different effects on amino acid neurotransmitter release.

    PubMed

    Feleder, C; Refojo, D; Jarry, H; Wuttke, W; Moguilevsky, J A

    1996-01-01

    Immune system disorders are often accompanied by alterations in the reproductive axis. The bacterial endotoxin (lipopolysaccharide, LPS) has inflammatory effects and activates cytokine release in the pituitary and hypothalamus. LPS inhibition of luteinizing-hormone-releasing hormone (LHRH) release at the hypothalamic level appears to be associated with modifications in the inhibitory GABAergic neurotransmitter system. Then, knowing that gamma-aminobutyric acid (GABA) mediates other neurotransmitter effects in the central nervous system, the possibility arises that this amino acid might mediate the effect of LPS on LHRH release by modifying amino acid neurotransmitter release at the hypothalamic level. Therefore, the present study was designed to investigate a possible mediatory function of the GABAergic system in the LPS-induced inhibition of LHRH secretion. To this end, the modifications in the excitatory (glutamate, Glu) and inhibitory (taurine, Tau, and GABA) amino acid neurotransmitter release after the application of GABA-A and GABA-B antagonists, respectively, were studied and the effects of LPS on their release determined. Male rats were decapitated at 9.00 h, and the preoptic/mediobasal hypothalamic area (POA/MBH) was dissected and superfused with Earle's balanced salt solution. Superfusate fractions were collected at 15-min intervals after a 60-min stabilization superfusion period. LPS (100 ng/ml) was then added to the superfusion medium over 1 h in three different experimental designs: (1) LPS only (2) LPS simultaneously with bicuculline (GABA-A antagonist) or with phaclofen (GABA-B antagonist), and (3) LPS and subsequently bicuculline or phaclofen, performed in different experiments. This was followed by a wash-out period. The POA/MBH fragments were then subjected to a 56-mM K+ stimulus. Control POA/MBH fragments were continuously superfused with Earle's solution. As expected, LHRH release was significantly reduced (p < 0.05) during and following

  16. Manganese accumulation in membrane fractions of primary astrocytes is associated with decreased γ-aminobutyric acid (GABA) uptake, and is exacerbated by oleic acid and palmitate.

    PubMed

    Fordahl, Steve C; Erikson, Keith M

    2014-05-01

    Manganese (Mn) exposure interferes with GABA uptake; however, the effects of Mn on GABA transport proteins (GATs) have not been identified. We sought to characterize how Mn impairs GAT function in primary rat astrocytes. Astrocytes exposed to Mn (500 μM) had significantly reduced (3)H-GABA uptake despite no change in membrane or cytosolic GAT3 protein levels. Co-treatment with 100 μM oleic or palmitic acids (both known to be elevated in Mn neurotoxicity), exacerbated the Mn-induced decline in (3)H-GABA uptake. Mn accumulation in the membrane fraction of astrocytes was enhanced with fatty acid administration, and was negatively correlated with (3)H-GABA uptake. Furthermore, control cells exposed to Mn only during the experimental uptake had significantly reduced (3)H-GABA uptake, and the addition of GABA (50 μM) blunted cytosolic Mn accumulation. These data indicate that reduced GAT function in astrocytes is influenced by Mn and fatty acids accumulating at or interacting with the plasma membrane.

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

    PubMed

    Yang, Runqiang; Guo, Qianghui; Gu, Zhenxin

    2013-01-01

    GABA shunt and polyamine degradation pathway on γ-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.

  18. Exogenous γ-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

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

    2014-01-01

    γ-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. PMID:24799560

  19. Exogenous γ-aminobutyric Acid (GABA) Application Improved Early Growth, Net Photosynthesis, and Associated Physio-Biochemical Events in Maize

    PubMed Central

    Li, Wu; Liu, Jianhua; Ashraf, Umair; Li, Gaoke; Li, Yuliang; Lu, Wenjia; Gao, Lei; Han, Fuguang; Hu, Jianguang

    2016-01-01

    γ-aminobutyric acid (GABA) is an endogenous signaling molecule and involved in growth regulations and plant development, however, a little information is available on the consequences of exogenous GABA application on growth, development, and associated physio-biochemical processes in maize. The present study examined the GABA-induced regulations in early growth, net photosynthetic rate, gas exchange, osmoregulation, and enzymatic activities in three maize cultivars, i.e., Yuecainuo 6, Zhengtian 68, and Yuecainuo 2. Two levels of GABA, i.e., 0 mg L-1 and 50 mg L-1, in solution form, with total application volume of 100 ml per pot containing 15 maize seedlings were exogenously applied. Results revealed that exogenous GABA application improved seedling growth in terms of seedling length and biomass accumulation in all maize cultivars at both 3 and 7 days after treatment (DAT). It also promoted net photosynthesis and variably affected gas exchange attributes, i.e., stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr), as well as leaves SPAD value. Furthermore, lipid peroxidation [in terms of malondialdehyde (MDA)] under GABA treated maize seedlings were also remained variable; however, osmolyte accumulation (protein and proline) and activities of anti-oxidants enzymes, i.e., super-oxide dismutase and peroxidase were also affected differently at both 3 and 7 DAT in all maize cultivars. Furthermore, enzymes involved in nitrogen metabolism, e.g., nitrate reductase and glutamine synthetase were improved. These results suggest the involvement of GABA in various physio-metablical mechanisms which might lead to improvement in morphological growth of maize. In future, research is still needed at molecular and genetic levels to unravel the involvement of GABA-mediated regulations in growth and its associated physio-biochemical mechanisms. PMID:27446149

  20. Quantification of γ-aminobutyric acid (GABA) in (1) H MRS volumes composed heterogeneously of grey and white matter.

    PubMed

    Mikkelsen, Mark; Singh, Krish D; Brealy, Jennifer A; Linden, David E J; Evans, C John

    2016-11-01

    The quantification of γ-aminobutyric acid (GABA) concentration using localised MRS suffers from partial volume effects related to differences in the intrinsic concentration of GABA in grey (GM) and white (WM) matter. These differences can be represented as a ratio between intrinsic GABA in GM and WM: rM . Individual differences in GM tissue volume can therefore potentially drive apparent concentration differences. Here, a quantification method that corrects for these effects is formulated and empirically validated. Quantification using tissue water as an internal concentration reference has been described previously. Partial volume effects attributed to rM can be accounted for by incorporating into this established method an additional multiplicative correction factor based on measured or literature values of rM weighted by the proportion of GM and WM within tissue-segmented MRS volumes. Simulations were performed to test the sensitivity of this correction using different assumptions of rM taken from previous studies. The tissue correction method was then validated by applying it to an independent dataset of in vivo GABA measurements using an empirically measured value of rM . It was shown that incorrect assumptions of rM can lead to overcorrection and inflation of GABA concentration measurements quantified in volumes composed predominantly of WM. For the independent dataset, GABA concentration was linearly related to GM tissue volume when only the water signal was corrected for partial volume effects. Performing a full correction that additionally accounts for partial volume effects ascribed to rM successfully removed this dependence. With an appropriate assumption of the ratio of intrinsic GABA concentration in GM and WM, GABA measurements can be corrected for partial volume effects, potentially leading to a reduction in between-participant variance, increased power in statistical tests and better discriminability of true effects.

  1. Exogenous γ-aminobutyric Acid (GABA) Application Improved Early Growth, Net Photosynthesis, and Associated Physio-Biochemical Events in Maize.

    PubMed

    Li, Wu; Liu, Jianhua; Ashraf, Umair; Li, Gaoke; Li, Yuliang; Lu, Wenjia; Gao, Lei; Han, Fuguang; Hu, Jianguang

    2016-01-01

    γ-aminobutyric acid (GABA) is an endogenous signaling molecule and involved in growth regulations and plant development, however, a little information is available on the consequences of exogenous GABA application on growth, development, and associated physio-biochemical processes in maize. The present study examined the GABA-induced regulations in early growth, net photosynthetic rate, gas exchange, osmoregulation, and enzymatic activities in three maize cultivars, i.e., Yuecainuo 6, Zhengtian 68, and Yuecainuo 2. Two levels of GABA, i.e., 0 mg L(-1) and 50 mg L(-1), in solution form, with total application volume of 100 ml per pot containing 15 maize seedlings were exogenously applied. Results revealed that exogenous GABA application improved seedling growth in terms of seedling length and biomass accumulation in all maize cultivars at both 3 and 7 days after treatment (DAT). It also promoted net photosynthesis and variably affected gas exchange attributes, i.e., stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr), as well as leaves SPAD value. Furthermore, lipid peroxidation [in terms of malondialdehyde (MDA)] under GABA treated maize seedlings were also remained variable; however, osmolyte accumulation (protein and proline) and activities of anti-oxidants enzymes, i.e., super-oxide dismutase and peroxidase were also affected differently at both 3 and 7 DAT in all maize cultivars. Furthermore, enzymes involved in nitrogen metabolism, e.g., nitrate reductase and glutamine synthetase were improved. These results suggest the involvement of GABA in various physio-metablical mechanisms which might lead to improvement in morphological growth of maize. In future, research is still needed at molecular and genetic levels to unravel the involvement of GABA-mediated regulations in growth and its associated physio-biochemical mechanisms.

  2. Artificial Autopolyploidization Modifies the Tricarboxylic Acid Cycle and GABA Shunt in Arabidopsis thaliana Col-0

    NASA Astrophysics Data System (ADS)

    Vergara, Fredd; Kikuchi, Jun; Breuer, Christian

    2016-05-01

    Autopolyploidy is a process whereby the chromosome set is multiplied and it is a common phenomenon in angiosperms. Autopolyploidy is thought to be an important evolutionary force that has led to the formation of new plant species. Despite its relevance, the consequences of autopolyploidy in plant metabolism are poorly understood. This study compares the metabolic profiles of natural diploids and artificial autotetraploids of Arabidopsis thaliana Col-0. Different physiological parameters are compared between diploids and autotetraploids using nuclear magnetic resonance (NMR), elemental analysis (carbon:nitrogen balance) and quantitative real-time PCR (qRT-PCR). The main difference between diploid and autotetraploid A. thaliana Col-0 is observed in the concentration of metabolites related to the tricarboxylic acid cycle (TCA) and γ-amino butyric acid (GABA) shunt, as shown by multivariate statistical analysis of NMR spectra. qRT-PCR shows that genes related to the TCA and GABA shunt are also differentially expressed between diploids and autotetraploids following similar trends as their corresponding metabolites. Solid evidence is presented to demonstrate that autopolyploidy influences core plant metabolic processes.

  3. p-Coumaric acid activates the GABA-A receptor in vitro and is orally anxiolytic in vivo.

    PubMed

    Scheepens, Arjan; Bisson, Jean-Francois; Skinner, Margot

    2014-02-01

    The increasing prevalence and social burden of subclinical anxiety in the western world represents a significant psychosocial and financial cost. Consumers are favouring a more natural and nonpharmacological approach for alleviating the effects of everyday stress and anxiety. The gamma-aminobutyric acid (GABA) receptor is the primary mediator of central inhibitory neurotransmission, and GABA-receptor agonists are well known to convey anxiolytic effects. Using an in vitro screening approach to identify naturally occurring phytochemical GABA agonists, we discovered the plant secondary metabolite p-coumaric acid to have significant GABAergic activity, an effect that could be blocked by co-administration of the specific GABA-receptor antagonist, picrotoxin. Oral administration of p-coumaric acid to rodents induced a significant anxiolytic effect in vivo as measured using the elevated plus paradigm, in line with the effects of oral diazepam. Given that p-coumaric acid is reasonably well absorbed following oral consumption in man and is relatively nontoxic, it may be suitable for the formulation of a safe and effective anxiolytic functional food.

  4. Impact of Precooling and Controlled-Atmosphere Storage on γ-Aminobutyric Acid (GABA) Accumulation in Longan (Dimocarpus longan Lour.) Fruit.

    PubMed

    Zhou, Molin; Ndeurumio, Kessy H; Zhao, Lei; Hu, Zhuoyan

    2016-08-24

    Longan (Dimocarpus longan Lour.) fruit cultivars 'Chuliang' and 'Shixia' were analyzed for γ-aminobutyric acid (GABA) accumulation after precooling and in controlled-atmosphere storage. Fruit were exposed to 5% O2 plus 3%, 5%, or 10% CO2 at 4 °C, and GABA and associated enzymes, aril firmness, and pericarp color were measured. Aril softening and pericarp browning were delayed by 5% CO2 + 5% O2. GABA concentrations and glutamate decarboxylase (GAD; EC 4.1.1.15) activities declined during storage at the higher-CO2 treatments. However, GABA aminotransferase (GABA-T; EC 2.6.1.19) activities in elevated CO2-treated fruit fluctuated during storage. GABA concentrations increased after precooling treatments. GAD activity and GABA-T activity were different between cultivars after precooling. GABA concentrations in fruit increased after 3 days of 10% CO2 + 5% O2 treatment and then declined as storage time increased. GABA accumulation was associated with stimulation of GAD activity rather than inhibition of GABA-T activity.

  5. Effect of androgens on sexual differentiation of pituitary gamma-aminobutyric acid receptor subunit GABA(B) expression.

    PubMed

    Bianchi, María S; Catalano, Paolo N; Bonaventura, María M; Silveyra, Patricia; Bettler, Bernhard; Libertun, Carlos; Lux-Lantos, Victoria A R

    2004-01-01

    Previous work demonstrated a sexually dimorphic ontogenic expression of gamma-aminobutyric acid receptors (GABA(B)R) in rat pituitary. As sex steroids determine sex-specific expression patterns, we now studied the effect of sex hormones on pituitary GABA(B)R expression. GABA(B)R subunits, measured by Western blot and by semi-quantitative RT-PCR and luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone measured by RIA were determined in two experimental designs: First experimental design: 8- and 15-day-old females (8F, 15F); 8F and 15F treated with 100 mug testosterone propionate (TP) on day 1 of life (8F100TP, 15F100TP), 8- and 15-day-old males (8M, 15M) and 8M and 15M castrated on day 1 (8MC, 15MC). Second experimental design: 8-day-old female and male animals: 8F, 8F100TP, 8F treated with 1 mug/day TP on days 1-4 (8F1TP), 8F treated with the androgen antagonist Flutamide (Flut: 2.5 mg/100 g BW of pregnant mother on days E17-E23) (8F-Flut), 8M, 8MC, 8M treated with Flut as above (8M-Flut) and 8MC-Flut. In these animals, in addition, GABA, glutamate, aspartate and taurine were measured by HPLC in hypothalami and cortex. In the first set of experiments, GABA(B1)R mRNA/protein expression was higher in 8F than in 15F, 8M or 15M. In 8F100TP, GABA(B1)R mRNA/protein decreased to male levels. TP treatment did not alter GABA(B1)R expression in 15F. There was no difference in GABA(B1)R expression between 8M and 15M and neonatal castration did not modify its expression. In the second set of experiments, TP (1 mug) or Flut did not modify GABA(B1)R in 8F, while 100 microg TP continued to decrease GABA(B1)R expression. In 8M, Flut, alone or with castration, increased GABA(B1)R mRNA/protein expression to 8F. Hypothalamic GABA content followed the same pattern as pituitary GABA(B)R expression in 8-day-old animals, suggesting a cross-regulation. With regard to hormonal levels, 100 microg, but not 1 microg TP altered gonadotropins at 8 days, although both

  6. Inhibition of GABA-gated chloride channels by 12,14-dichlorodehydroabietic acid in mammalian brain

    PubMed Central

    Nicholson, Russell A; Lees, George; Zheng, Jian; Verdon, Bernard

    1999-01-01

    12,14-dichlorodehydroabietic acid (12,14-Cl2DHA) reduced GABA-stimulated uptake of 36Cl− into mouse brain synaptoneurosomes suggesting inhibition of mammalian GABAA receptor function. 12,14-Cl2DHA did not affect the binding of [3H]-muscimol to brain membranes but displaced specifically bound [3H]-EBOB. The inhibitory effect on [3H]-EBOB binding was not reversible. 12,14-Cl2DHA reduced the availability of [3H]-EBOB binding sites (Bmax) without changing the KD of the radioligand for remaining sites. 12,14-Cl2DHA did not affect the rate of association of [3H]-EBOB with its chloride channel receptor, but increased the initial rate of [3H]-EBOB dissociation. 12,14-Cl2DHA enhanced the incidence of EPSCs when rapidly applied to cultured rat cortical neurones. Longer exposures produced block of IPSCs with marked increases in the frequency of EPSCs and min EPSCs. 12,14-Cl2DHA also irreversibly suppressed chloride currents evoked by pulses of exogenous GABA in these cells. Ultimately, 12,14-Cl2DHA inhibited all synaptic traffic and action currents in current clamped cells indicating that, in contrast to picrotoxinin (which causes paroxysmal bursting), it is not fully selective for the GABAA receptor-chloride channel complex. The depolarizing block seen with 12,14-Cl2DHA in amphotericin-perforated preparations implicates loss of Ca2+ buffering in the polarity change and this may account for inhibition of spontaneous action potentials. Our investigation demonstrates that 12,14-Cl2DHA blocks GABA-dependent chloride entry in mammalian brain and operates as a non-competitive insurmountable GABAA antagonist. The mechanism likely involves either irreversible binding of 12,14-Cl2DHA to the trioxabicyclooctane recognition site or a site that is allosterically coupled to it. We cannot exclude, however, the possibility that 12,14-Cl2DHA causes localized proteolysis or more extensive conformational change within a critical subunit of the chloride channel. PMID:10204999

  7. Decreased GABA(A) benzodiazepine binding site densities in postmortem brains of Cloninger type 1 and 2 alcoholics.

    PubMed

    Laukkanen, Virpi; Storvik, Markus; Häkkinen, Merja; Akamine, Yumiko; Tupala, Erkki; Virkkunen, Matti; Tiihonen, Jari

    2013-03-01

    Ethanol modulates the GABA(A) receptor to cause sedative, anxiolytic and hypnotic effects that are qualitatively similar to benzodiazepines and barbiturates. The aim of this study was to explore if GABA(A) receptor density is altered in post-mortem brains of anxiety-prone Cloninger type 1 and socially hostile type 2 alcoholic subtypes when compared to controls. The GABA(A) binding site density was measured by whole-hemisphere autoradiography with tritium labeled flunitrazepam ([(3)H]flunitrazepam) from 17 alcoholic (nine type 1, eight type 2) and 10 non-alcoholic post-mortem brains, using cold flumazepam as a competitive ligand. A total of eight specific brain areas were examined. Alcoholics displayed a significantly (p < 0.001, bootstrap type generalizing estimating equations model) reduced [(3)H]flunitrazepam binding site density when compared to controls. When localized, type 2 alcoholics displayed a significantly (p ≤ 0.05) reduced [(3)H]flunitrazepam binding site density in the internal globus pallidus, the gyrus dentatus and the hippocampus, whereas type 1 alcoholics differed from controls in the internal globus pallidus and the hippocampus. While previous reports have demonstrated significant alterations in dopaminergic and serotonergic receptors between type 1 and type 2 alcoholics among these same subjects, we observed no statistically significant difference in [(3)H]flunitrazepam binding site densities between the Cloninger type 1 and type 2 alcoholics.

  8. Synthesis and characterization of N,N-dichlorinated amino acids: taurine, homotaurine, GABA and L-leucine.

    PubMed

    van Gelder, N M; Bowers, R J

    2001-06-01

    Epilepsy, trauma and other circumstances leading to hyperexcitable conditions in the CNS tend neurochemically to be associated with excessive stimulated release of glutamic acid and/or a failure of GABA modulated inhibition. Somewhat to a lesser extent, taurine and its homologue homotaurine, have also been shown to antagonize the excitatory actions of glutamic acid. Here we report the successful synthesis and isolation in pure form of N,N-dichlorinated GABA, taurine, homotaurine and leucine. These compounds are much more lipophilic than their parent compounds and may therefore more readily penetrate the blood-brain barrier systems into the neural tissue, where they can be easily dechlorinated. Very preliminary biological testing shows that this may indeed occur. The synthesis and purification methodology will likely also be applicable to a number of other amino acids as well as certain peptides or selected proteins.

  9. α4βδ GABA(A) receptors are high-affinity targets for γ-hydroxybutyric acid (GHB).

    PubMed

    Absalom, Nathan; Eghorn, Laura F; Villumsen, Inge S; Karim, Nasiara; Bay, Tina; Olsen, Jesper V; Knudsen, Gitte M; Bräuner-Osborne, Hans; Frølund, Bente; Clausen, Rasmus P; Chebib, Mary; Wellendorph, Petrine

    2012-08-14

    γ-Hydroxybutyric acid (GHB) binding to brain-specific high-affinity sites is well-established and proposed to explain both physiological and pharmacological actions. However, the mechanistic links between these lines of data are unknown. To identify molecular targets for specific GHB high-affinity binding, we undertook photolinking studies combined with proteomic analyses and identified several GABA(A) receptor subunits as possible candidates. A subsequent functional screening of various recombinant GABA(A) receptors in Xenopus laevis oocytes using the two-electrode voltage clamp technique showed GHB to be a partial agonist at αβδ- but not αβγ-receptors, proving that the δ-subunit is essential for potency and efficacy. GHB showed preference for α4 over α(1,2,6)-subunits and preferably activated α4β1δ (EC(50) = 140 nM) over α4β(2/3)δ (EC(50) = 8.41/1.03 mM). Introduction of a mutation, α4F71L, in α4β1(δ)-receptors completely abolished GHB but not GABA function, indicating nonidentical binding sites. Radioligand binding studies using the specific GHB radioligand [(3)H](E,RS)-(6,7,8,9-tetrahydro-5-hydroxy-5H-benzocyclohept-6-ylidene)acetic acid showed a 39% reduction (P = 0.0056) in the number of binding sites in α4 KO brain tissue compared with WT controls, corroborating the direct involvement of the α4-subunit in high-affinity GHB binding. Our data link specific GHB forebrain binding sites with α4-containing GABA(A) receptors and postulate a role for extrasynaptic α4δ-containing GABA(A) receptors in GHB pharmacology and physiology. This finding will aid in elucidating the molecular mechanisms behind the proposed function of GHB as a neurotransmitter and its unique therapeutic effects in narcolepsy and alcoholism.

  10. Guinea Pig Horizontal Cells Express GABA, the GABA-Synthesizing Enzyme GAD65, and the GABA Vesicular Transporter

    PubMed Central

    Guo, Chenying; Hirano, Arlene A.; Stella, Salvatore L.; Bitzer, Michaela; Brecha, Nicholas C.

    2013-01-01

    γ-Aminobutyric acid (GABA) is likely expressed in horizontal cells of all species, although conflicting physiological findings have led to considerable controversy regarding its role as a transmitter in the outer retina. This study has evaluated key components of the GABA system in the outer retina of guinea pig, an emerging retinal model system. The presence of GABA, its rate-limiting synthetic enzyme glutamic acid decarboxylase (GAD65 and GAD67 isoforms), the plasma membrane GABA transporters (GAT-1 and GAT-3), and the vesicular GABA transporter (VGAT) was evaluated by using immunohistochemistry with well-characterized antibodies. The presence of GAD65 mRNA was also evaluated by using laser capture microdissection and reverse transcriptase-polymerase chain reaction. Specific GABA, GAD65, and VGAT immunostaining was localized to horizontal cell bodies, as well as to their processes and tips in the outer plexiform layer. Furthermore, immunostaining of retinal whole mounts and acutely dissociated retinas showed GAD65 and VGAT immunoreactivity in both A-type and B-type horizontal cells. However, these cells did not contain GAD67, GAT-1, or GAT-3 immunoreactivity. GAD65 mRNA was detected in horizontal cells, and sequencing of the amplified GAD65 fragment showed approximately 85% identity with other mammalian GAD65 mRNAs. These studies demonstrate the presence of GABA, GAD65, and VGAT in horizontal cells of the guinea pig retina, and support the idea that GABA is synthesized from GAD65, taken up into synaptic vesicles by VGAT, and likely released by a vesicular mechanism from horizontal cells. PMID:20235161

  11. Modes and nodes explain the mechanism of action of vortioxetine, a multimodal agent (MMA): modifying serotonin's downstream effects on glutamate and GABA (gamma amino butyric acid) release.

    PubMed

    Stahl, Stephen M

    2015-08-01

    Vortioxetine is an antidepressant with multiple pharmacologic modes of action at targets where serotonin neurons connect with other neurons. These actions modify the release of both glutamate and GABA (gamma amino butyric acid) within various brain circuits.

  12. Expression of the γ-Aminobutyric Acid (GABA) Plasma Membrane Transporter-1 in Monkey and Human Retina

    PubMed Central

    Casini, Giovanni; Rickman, Dennis W.; Brecha, Nicholas C.

    2010-01-01

    Purpose To determine the expression pattern of the predominant γ-aminobutyric acid (GABA) plasma membrane transporter GAT-1 in Old World monkey (Macaca mulatta) and human retina. Methods GAT-1 was localized in retinal sections by using immunohistochemical techniques with fluorescence and confocal microscopy. Double-labeling studies were performed with the GAT-1 antibody using antibodies to GABA, vasoactive intestinal polypeptide (VIP), tyrosine hydroxylase (TH), and the bipolar cell marker Mab115A10. Results The pattern of GAT-1 immunostaining was similar in human and monkey retinas. Numerous small immunoreactive somata were in the inner nuclear layer (INL) and were present rarely in the inner plexiform layer (IPL) of all retinal regions. Medium GAT-1 somata were in the ganglion cell layer in the parafoveal and peripheral retinal regions. GAT-1 fibers were densely distributed throughout the IPL. Varicose processes, originating from both the IPL and somata in the INL, arborized in the outer plexiform layer (OPL), forming a sparse network in all retinal regions, except the fovea. Sparsely occurring GAT-1 processes were in the nerve fiber layer in parafoveal regions and near the optic nerve head but not in the optic nerve. In the INL, 99% of the GAT-1 somata contained GABA, and 66% of the GABA immunoreactive somata expressed GAT-1. GAT-1 immunoreactivity was in all VIP-containing cells, but it was absent in TH-immunoreactive amacrine cells and in Mab115A10 immunoreactive bipolar cells. Conclusions GAT-1 in primate retinas is expressed by amacrine and displaced amacrine cells. The predominant expression of GAT-1 in the inner retina is consistent with the idea that GABA transporters influence neurotransmission and thus participate in visual information processing in the retina. PMID:16565409

  13. Verification of γ-Amino-Butyric Acid (GABA) Signaling System Components in Periodontal Ligament Cells In Vivo and In Vitro.

    PubMed

    Konermann, Anna; Kantarci, Alpdogan; Wilbert, Steven; Van Dyke, Thomas; Jäger, Andreas

    2016-11-01

    CNS key neurotransmitter γ-amino-butyric acid (GABA) and its signaling components are likewise detectable in non-neuronal tissues displaying inter alia immunomodulatory functions. This study aimed at identifying potential glutamate decarboxylase (GAD)65 and GABA receptor expression in periodontal ligament (PDL) cells in vivo and in vitro, with particular regard to inflammation and mechanical loading. Gene expression was analyzed in human PDL cells at rest or in response to IL-1ß (5 ng/ml) or TNFα (5 ng/ml) challenge via qRT-PCR. Western blot determined constitutive receptor expression, and confocal laser scanning fluorescence microscopy visualized expression changes induced by inflammation. ELISA quantified GAD65 release. Immunocytochemistry was performed for GABA component detection in vitro on mechanically loaded PDL cells, and in vivo on rat upper jaw biopsies with mechanically induced root resorptions. Statistical significance was set at p < 0.05. GABAB1, GABAB2, GABAA1, and GABAA3 were ubiquitously expressed both on gene and protein level. GABAA2 and GAD65 were undetectable in resting cells, but induced by inflammation. GABAB1 exhibited the highest basal gene expression (6.97 % ± 0.16). IL-1ß markedly increased GABAB2 on a transcriptional (57.28-fold ± 12.40) and protein level seen via fluorescence microscopy. TNFα-stimulated PDL cells released GAD65 (3.68 pg/ml ± 0.17 after 24 h, 5.77 pg/ml ± 0.65 after 48 h). Immunocytochemistry revealed GAD65 expression in mechanically loaded PDL cells. In vivo, GABA components were varyingly expressed in an inflammatory periodontal environment. PDL cells differentially express GABA signaling components and secrete GAD65. Inflammation and mechanical loading regulate these neurotransmitter molecules, which are also detectable in vivo and are potentially involved in periodontal pathophysiology.

  14. Central- and peripheral-type benzodiazepine receptors: similar regulation by stress and GABA receptor agonists.

    PubMed

    Rägo, L; Kiivet, R A; Harro, J; Pŏld, M

    1989-04-01

    Central- and peripheral-type benzodiazepine (BD) receptors were labelled either by 3H-flunitrazepam or 3H-Ro 5-4864 in vitro after stress and in vivo administration of GABAA and GABAB agonists. A significant increase in the density of cerebral cortex and kidney BD binding sites was observed in rats after forced swimming stress. Similar changes in both type of BD receptors were also followed when naive (stressed) and handling-habituated (unstressed) rats were used. Stress in both models was unable to change the affinity of BD receptors in cerebral cortex, but significantly lowered it in kidneys. Acute treatment of rats with muscimol (1.5 mg/kg) or (-)baclofen (5 mg/kg) resulted in marked increase in the affinity of BD binding not only in cerebral cortex but also in kidneys. After (-)baclofen treatment the number of BD binding sites was lowered in the structures studied. In a separate study mice selected according to their behavioral response to (-)baclofen (1 mg/kg) were studied. Two weeks after the selection it appeared that baclofen responders were behaviorally more "anxious" than baclofen nonresponders. The number of BD binding sites was reduced in cerebral cortex, cerebellum, heart and kidneys in baclofen responders as compared to baclofen nonresponders. In several cases the changes in peripheral BD binding sites were even more pronounced than those in central ones. The data presented here evidence that peripheral- and central-type BD receptors are regulated similarly by GABA and some models of stress. The physiological mechanisms involved in similar regulation of central- and peripheral-type BD receptors are yet unknown.

  15. Dual effects of slightly acidic electrolyzed water (SAEW) treatment on the accumulation of γ-aminobutyric acid (GABA) and rutin in germinated buckwheat.

    PubMed

    Hao, Jianxiong; Wu, Tongjiao; Li, Huiying; Wang, Wei; Liu, Haijie

    2016-06-15

    In the present study, the dual effects of slightly acidic electrolyzed water (SAEW) treatment on γ-aminobutyric acid (GABA) and rutin accumulation of germinated buckwheat were evaluated during germination. The results showed that SAEW treatment (pH 5.83, ACC of 20.3 mg/L) could promote the accumulation of GABA and rutin in germinated buckwheat. The GABA and rutin contents of SAEW-germinated buckwheat reached 143.20 and 739.9 mg/100 g respectively, which is significantly higher than those of control (P<0.05). Moreover, SAEW treatment could increase the activity of glutamic acid decarboxylase (GAD) and phenylalanine ammonialyase (PAL) and thus result in the GABA and rutin accumulation of germinated buckwheat. The results suggested that SAEW treatment could promote the rutin accumulation of germinated buckwheat by influencing phenylpropanoid secondary metabolic pathway instead of the inhibition of rutin degrading enzyme (RDE) activity. In addition, SAEW treatment had no adverse impact on the sprouts growth and could reduce the microbial populations of germinated buckwheat during germination.

  16. Distinct activities of GABA agonists at synaptic- and extrasynaptic-type GABAA receptors

    PubMed Central

    Mortensen, Martin; Ebert, Bjarke; Wafford, Keith; Smart, Trevor G

    2010-01-01

    The activation characteristics of synaptic and extrasynaptic GABAA receptors are important for shaping the profile of phasic and tonic inhibition in the central nervous system, which will critically impact on the activity of neuronal networks. Here, we study in isolation the activity of three agonists, GABA, muscimol and 4,5,6,7-tetrahydoisoxazolo[5,4-c]pyridin-3(2H)-one (THIP), to further understand the activation profiles of α1β3γ2, α4β3γ2 and α4β3δ receptors that typify synaptic- and extrasynaptic-type receptors expressed in the hippocampus and thalamus. The agonists display an order of potency that is invariant between the three receptors, which is reliant mostly on the agonist dissociation constant. At δ subunit-containing extrasynaptic-type GABAA receptors, both THIP and muscimol additionally exhibited, to different degrees, superagonist behaviour. By comparing whole-cell and single channel currents induced by the agonists, we provide a molecular explanation for their different activation profiles. For THIP at high concentrations, the unusual superagonist behaviour on α4β3δ receptors is a consequence of its ability to increase the duration of longer channel openings and their frequency, resulting in longer burst durations. By contrast, for muscimol, moderate superagonist behaviour was caused by reduced desensitisation of the extrasynaptic-type receptors. The ability to specifically increase the efficacy of receptor activation, by selected exogenous agonists over that obtained with the natural transmitter, may prove to be of therapeutic benefit under circumstances when synaptic inhibition is compromised or dysfunctional. PMID:20176630

  17. Systematic analysis of γ-aminobutyric acid (GABA) metabolism and function in the social amoeba Dictyostelium discoideum.

    PubMed

    Wu, Yuantai; Janetopoulos, Chris

    2013-05-24

    While GABA has been suggested to regulate spore encapsulation in the social amoeba Dictyostelium discoideum, the metabolic profile and other potential functions of GABA during development remain unclear. In this study, we investigated the homeostasis of GABA metabolism by disrupting genes related to GABA metabolism and signaling. Extracellular levels of GABA are tightly regulated during early development, and GABA is generated by the glutamate decarboxylase, GadB, during growth and in early development. However, overexpression of the prespore-specific homologue, GadA, in the presence of GadB reduces production of extracellular GABA. Perturbation of extracellular GABA levels delays the process of aggregation. Cytosolic GABA is degraded by the GABA transaminase, GabT, in the mitochondria. Disruption of a putative vesicular GABA transporter (vGAT) homologue DdvGAT reduces secreted GABA. We identified the GABAB receptor-like family member GrlB as the major GABA receptor during early development, and either disruption or overexpression of GrlB delays aggregation. This delay is likely the result of an abolished pre-starvation response and late expression of several "early" developmental genes. Distinct genes are employed for GABA generation during sporulation. During sporulation, GadA alone is required for generating GABA and DdvGAT is likely responsible for GABA secretion. GrlE but not GrlB is the GABA receptor during late development.

  18. Design, synthesis and SAR studies of GABA uptake inhibitors derived from 2-substituted pyrrolidine-2-yl-acetic acids.

    PubMed

    Steffan, Tobias; Renukappa-Gutke, Thejavathi; Höfner, Georg; Wanner, Klaus T

    2015-03-15

    In this paper, we disclose the design and synthesis of a series of 2-substituted pyrrolidine-2-yl-acetic acid as core structures and the N-arylalkyl derivatives thereof as potential GABA transport inhibitors. The 2-position in the side chain of pyrrolidine-2-yl-acetic acid derivatives was substituted with alkyl, hydroxy and amino groups to modulate the activity and selectivity to mGAT1 and mGAT4 proteins. SAR studies of the compounds performed for the four mouse GABA transporter proteins (mGAT1-mGAT4) implied significant potencies and subtype selectivities for 2-hydroxy-2-pyrrolidine-2-yl-acetic acid derivatives. The racemate rac-(u)-13c exhibited the highest potency (pIC50 5.67) at and selectivity for mGAT1 in GABA uptake assays. In fact, the potency of rac-(u)-13c at hGAT-1 (pIC50 6.14) was even higher than its potency at mGAT1. These uptake results for rac-(u)-13c are in line with the binding affinities to the aforesaid proteins mGAT1 (pKi 6.99) and hGAT-1 (pKi 7.18) determined by MS Binding Assay based on NO711 as marker quantified by LC-ESI-MS-MS analysis. Interestingly, the 2-hydroxy-2-pyrrolidine-2-yl-acetic acid rac-(u)-13d containing 2-{[tris(4-methoxyphenyl)]methoxy} ethyl group at the nitrogen atom of the pyrrolidine ring showed high potency at mGAT4 and a comparatively better selectivity for this protein (>15 against mGAT3) than the well known mGAT4 uptake inhibitor (S)-SNAP-5114.

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

    PubMed

    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

    2011-08-01

    In plants, γ-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.

  20. Disorders of GABA metabolism: SSADH and GABA-transaminase deficiencies.

    PubMed

    Parviz, Mahsa; Vogel, Kara; Gibson, K Michael; Pearl, Phillip L

    2014-11-25

    Clinical disorders known to affect inherited gamma-amino butyric acid (GABA) metabolism are autosomal recessively inherited succinic semialdehyde dehydrogenase and GABA-transaminase deficiency. The clinical presentation of succinic semialdehyde dehydrogenase deficiency includes intellectual disability, ataxia, obsessive-compulsive disorder and epilepsy with a nonprogressive course in typical cases, although a progressive form in early childhood as well as deterioration in adulthood with worsening epilepsy are reported. GABA-transaminase deficiency is associated with a severe neonatal-infantile epileptic encephalopathy.

  1. The effects of agonists of ionotropic GABA(A) and metabotropic GABA(B) receptors on learning.

    PubMed

    Zyablitseva, Evgeniya A; Kositsyn, Nikolay S; Shul'gina, Galina I

    2009-05-01

    The research described here investigates the role played by inhibitory processes in the discriminations made by the nervous system of humans and animals between familiar and unfamiliar and significant and nonsignificant events. This research compared the effects of two inhibitory mediators of gamma-aminobutyric acid (GABA): 1) phenibut, a nonselective agonist of ionotropic GABA(A) and metabotropic GABA(B) receptors and 2) gaboxadol a selective agonist of ionotropic GABA(A) receptors on the process of developing active defensive and inhibitory conditioned reflexes in alert non-immobilized rabbits. It was found that phenibut, but not gaboxadol, accelerates the development of defensive reflexes at an early stage of conditioning. Both phenibut and gaboxadol facilitate the development of conditioned inhibition, but the effect of gaboxadol occurs at later stages of conditioning and is less stable than that of phenibut. The earlier and more stable effects of phenibut, as compared to gaboxadol, on storage in memory of the inhibitory significance of a stimulus may occur because GABA(B) receptors play the dominant role in the development of internal inhibition during an early stage of conditioning. On the other hand this may occur because the participation of both GABA(A) and GABA(B) receptors are essential to the process. We discuss the polyfunctionality of GABA receptors as a function of their structure and the positions of the relevant neurons in the brain as this factor can affect regulation of various types of psychological processes.

  2. GABA-A and GABA-B receptors in the cuneate nucleus of the rat in vivo.

    PubMed

    Orviz, P; Cecchini, B G; Andrés-Trelles, F

    1986-09-01

    Electric stimulation of the rat forepaw evokes a negative potential (N-wave) at the ipsilateral cuneate nucleus. The responses of the N-wave to microiontophoretically applied GABA agonists and antagonists have been studied. Applications of GABA-A agonists (3-amino-propanesulfonic acid and muscimol) reduce the amplitude of the N-wave. This effect decreases during prolonged application, suggesting a desensitization of GABA-A receptors. In addition the effect of muscimol is reduced by (-)-bicuculline methiodide. Baclofen (a GABA-B agonist) also depresses the N-wave but its action lasts longer, is less reversible, shows no desensitization and is not blocked by (-)-bicuculline methiodide. The different responses of the N-wave to GABA-A and GABA-B agonists are compatible with the existence of different types of functional receptors for them in the cuneate nucleus of the rat. The receptors activated by muscimol (GABA-A) are clearly not the same as the ones activated by baclofen (conceivably GABA-B).

  3. Stable isotope dilution HILIC-MS/MS method for accurate quantification of glutamic acid, glutamine, pyroglutamic acid, GABA and theanine in mouse brain tissues.

    PubMed

    Inoue, Koichi; Miyazaki, Yasuto; Unno, Keiko; Min, Jun Zhe; Todoroki, Kenichiro; Toyo'oka, Toshimasa

    2016-01-01

    In this study, we developed the stable isotope dilution hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC-MS/MS) technique for the accurate, reasonable and simultaneous quantification of glutamic acid (Glu), glutamine (Gln), pyroglutamic acid (pGlu), γ-aminobutyric acid (GABA) and theanine in mouse brain tissues. The quantification of these analytes was accomplished using stable isotope internal standards and the HILIC separating mode to fully correct the intramolecular cyclization during the electrospray ionization. It was shown that linear calibrations were available with high coefficients of correlation (r(2)  > 0.999, range from 10 pmol/mL to 50 mol/mL). For application of the theanine intake, the determination of Glu, Gln, pGlu, GABA and theanine in the hippocampus and central cortex tissues was performed based on our developed method. In the region of the hippocampus, the concentration levels of Glu and pGlu were significantly reduced during reality-based theanine intake. Conversely, the concentration level of GABA increased. This result showed that transited theanine has an effect on the metabolic balance of Glu analogs in the hippocampus.

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

    SciTech Connect

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

    1989-01-01

    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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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. The corn rootworm, Diabrotica virgifera virgifera, is a damaging pest of cultivated corn that was partially controlled by ...

  6. Simulated GABA synaptic input and L-type calcium channels form functional microdomains in hypothalamic gonadotropin-releasing hormone neurons.

    PubMed

    Hemond, Peter J; O'Boyle, Michael P; Roberts, Carson B; Delgado-Reyes, Alfonso; Hemond, Zoe; Suter, Kelly J

    2012-06-27

    Hypothalamic gonadotropin-releasing hormone (GnRH) neurons integrate the multiple internal and external cues that regulate sexual reproduction. In contrast to other neurons that exhibit extensive dendritic arbors, GnRH neurons usually have a single dendrite with relatively little branching. This largely precludes the integration strategy in which a single dendritic branch serves as a unit of integration. In the present study, we identify a gradient in L-type calcium channels in dendrites of mouse GnRH neurons and its interaction with GABAergic and glutamatergic inputs. Higher levels of L-type calcium channels are in somata/proximal dendrites (i.e., 0-26 μm) and distal dendrites (∼130 μm dendrite length), but intervening midlengths of dendrite (∼27-130 μm) have reduced L-type calcium channels. Using uncaging of GABA, there is a decreasing GABAergic influence along the dendrite and the impact of GABA(A) receptors is dependent on activation of L-type calcium channels. This results in amplification of proximal GABAergic signals and attenuation of distal dendritic signals. Most interestingly, the intervening dendritic regions create a filter through which only relatively high-amplitude, low-frequency GABAergic signaling to dendrites elicits action potentials. The findings of the present study suggest that GnRH dendrites adopt an integration strategy whereby segments of single nonbranching GnRH dendrites create functional microdomains and thus serve as units of integration.

  7. 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.

    PubMed

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

    2009-01-01

    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.

  8. Enhancing Contents of γ-Aminobutyric Acid (GABA) and Other Micronutrients in Dehulled Rice during Germination under Normoxic and Hypoxic Conditions.

    PubMed

    Ding, Junzhou; Yang, Tewu; Feng, Hao; Dong, Mengyi; Slavin, Margaret; Xiong, Shanbai; Zhao, Siming

    2016-02-10

    Biofortification of staple grains with high contents of essential micronutrients is an important strategy to overcome micronutrient malnutrition. However, few attempts have targeted at γ-aminobutyric acid (GABA), a functional nutrient for aging populations. In this study, two rice cultivars, Heinuo and Xianhui 207, were used to investigate changes in GABA and other nutritional compounds of dehulled rice after germination under normoxic and hypoxic conditions. Forty-one metabolites were identified in both cultivars treated by normoxic germination, whereas the germinated dehulled rice of Heinuo and Xianhui 207 under hypoxic treatment had 43 and 41 metabolites identified, respectively. GABA increased in dehulled rice after germination, especially under hypoxia. Meanwhile, a number of other health-beneficial and/or flavor-related compounds such as lysine and d-mannose increased after the hypoxic treatment. The accumulation of GABA exhibited genotype-specific modes in both normoxic and hypoxic treatments. With regard to GABA production, Xianhui 207 was more responsive to the germination process than Heinuo, whereas Heinuo was more responsive to hypoxia than Xianhui 207. This study provides a promising approach to biofortify dehulled rice with increased GABA and other nutrients through metabolomic-based regulation.

  9. Natural and Synthetic Variants of the Tricarboxylic Acid Cycle in Cyanobacteria: Introduction of the GABA Shunt into Synechococcus sp. PCC 7002

    PubMed Central

    Zhang, Shuyi; Qian, Xiao; Chang, Shannon; Dismukes, G. C.; Bryant, Donald A.

    2016-01-01

    For nearly half a century, it was believed that cyanobacteria had an incomplete tricarboxylic acid (TCA) cycle, because 2-oxoglutarate dehydrogenase (2-OGDH) was missing. Recently, a bypass route via succinic semialdehyde (SSA), which utilizes 2-oxoglutarate decarboxylase (OgdA) and succinic semialdehyde dehydrogenase (SsaD) to convert 2-oxoglutarate (2-OG) into succinate, was identified, thus completing the TCA cycle in most cyanobacteria. In addition to the recently characterized glyoxylate shunt that occurs in a few of cyanobacteria, the existence of a third variant of the TCA cycle connecting these metabolites, the γ-aminobutyric acid (GABA) shunt, was considered to be ambiguous because the GABA aminotransferase is missing in many cyanobacteria. In this study we isolated and biochemically characterized the enzymes of the GABA shunt. We show that N-acetylornithine aminotransferase (ArgD) can function as a GABA aminotransferase and that, together with glutamate decarboxylase (GadA), it can complete a functional GABA shunt. To prove the connectivity between the OgdA/SsaD bypass and the GABA shunt, the gadA gene from Synechocystis sp. PCC 6803 was heterologously expressed in Synechococcus sp. PCC 7002, which naturally lacks this enzyme. Metabolite profiling of seven Synechococcus sp. PCC 7002 mutant strains related to these two routes to succinate were investigated and proved the functional connectivity. Metabolite profiling also indicated that, compared to the OgdA/SsaD shunt, the GABA shunt was less efficient in converting 2-OG to SSA in Synechococcus sp. PCC 7002. The metabolic profiling study of these two TCA cycle variants provides new insights into carbon metabolism as well as evolution of the TCA cycle in cyanobacteria. PMID:28018308

  10. 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.

    PubMed

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

    2013-09-05

    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.

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

    PubMed

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

    2014-03-01

    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.

  12. Modulatory action of taurine on the release of GABA in cerebellar slices of the guinea pig.

    PubMed

    Namima, M; Okamoto, K; Sakai, Y

    1983-01-01

    For the purpose of demonstrating the action of taurine as a neuromodulator in addition to its suggested neurotransmitter function, the effects of taurine and muscimol on the depolarization-induced Ca-dependent release of [3H] gamma-aminobutyric acid ([3H]GABA) and L-[3H]glutamate in cerebellar slices from guinea pigs were investigated. The release of [3H]GABA was found to be greatly decreased by a GABA agonist, muscimol, and by taurine, but not by glycine. The release of L-[3H]glutamate was little affected by taurine. The release of [3H]GABA, was enhanced by bicuculline and strychnine, but not by picrotoxin, and the suppressive action of muscimol on the GABA release was antagonized by bicuculline, picrotoxin, and strychnine, suggesting the possible existence of presynaptic autoreceptors for GABA in the cerebellum. The suppressive action of taurine on the release of [3H]GABA, on the other hand, was blocked only by bicuculline. These results suggest that taurine reduced the release of [3H]GABA from cerebellar slices by acting on the GABA autoreceptors or, more likely, on other types of receptors that are sensitive to bicuculline. As a possible mechanism for this modulatory action of taurine, the blockade by this amino acid of the influx of Ca2+ into cerebellar tissues was tentatively suggested.

  13. Synaptic-type α1β2γ2L GABAA receptors produce large persistent currents in the presence of ambient GABA and anesthetic drugs.

    PubMed

    Li, Ping; Akk, Gustav

    2015-05-01

    Synaptic GABAA receptors respond to synaptically released GABA and are considered to be unaffected by the low levels of ambient transmitter in the brain. We show that synaptic-type α1β2γ2L GABAA receptors expressed in HEK293 cells respond with large steady-state currents to combinations of a low concentration (0.5 μM) of GABA and clinically used GABAergic modulators propofol, etomidate, or pentobarbital or the steroid alphaxalone. At a maximally effective concentration of modulator, the current levels at the end of 2-minute applications of drug combinations were >10% of the peak response to saturating GABA. In the absence of modulators, 0.5 μM GABA generated a steady-state response of 1% of the peak response to saturating GABA. The concentration-response curves for enhancement of steady-state currents by propofol, etomidate, pentobarbital, or alphaxalone were at similar or lower drug concentrations compared with concentration-response relationships for enhancement of peak responses. We propose that modulation of tonically activated synaptic-type GABAA receptors contributes to the clinical actions of sedative drugs.

  14. Alternate cadmium exposure differentially affects the content of gamma-aminobutyric acid (GABA) and taurine within the hypothalamus, median eminence, striatum and prefrontal cortex of male rats.

    PubMed

    Esquifino, A I; Seara, R; Fernández-Rey, E; Lafuente, A

    2001-05-01

    This work examines changes of gamma aminobutyric acid (GABA) and taurine contents in the hypothalamus, striatum and prefrontal cortex of the rat after an alternate schedule of cadmium administration. Age-associated changes were also evaluated, of those before puberty and after adult age. In control rats GABA content decreased with age in the median eminence and in anterior, mediobasal and posterior hypothalamus, prefrontal cortex and the striatum. Taurine content showed similar results with the exception of mediobasal hypothalamus and striatum, where no changes were detected. In pubertal rats treated with cadmium from 30 to 60 days of life, GABA content significantly decreased in all brain regions except in the striatum. When cadmium was administered from day 60 to 90 of life, GABA content was significantly changed in prefrontal cortex only compared with the age matched controls. Taurine content showed similar results in pubertal rats, with the exception of the median eminence and the mediobasal hypothalamus, neither of which showed a change. However, when cadmium was administered to rats from day 60 to 90 of life, taurine content only changed in prefrontal cortex compared with the age matched controls. These results suggest that cadmium differentially affects GABA and taurine contents within the hypothalamus, median eminence, striatum and prefrontal cortex as a function of age.

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

    PubMed Central

    Lee, Hyesung; Chang, Moon-Jeong

    2010-01-01

    Poly-gamma-glutamic acid (γ-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 γ-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% γ-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. γ-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 γ-PGA supplemented groups both in rats fed the normal and high fat diets than in the no γ-PGA controls. GABA concentrations showed the same tendency. The results indicated that γ-PGA intake increased GABA concentrations in the serum and brain. However, the effects were not shown in obese rats. PMID:20198205

  16. Relative vulnerability of dopamine and GABA neurons in mesencephalic culture to inhibition of succinate dehydrogenase by malonate and 3-nitropropionic acid and protection by NMDA receptor blockade.

    PubMed

    Zeevalk, G D; Derr-Yellin, E; Nicklas, W J

    1995-12-01

    The effects of different severities of metabolic stress on dopamine (DA) and gamma-aminobutyric acid (GABA) cell loss were examined in rat mesencephalic culture. Partial metabolic inhibition was induced in 12-day-old cultures by a 24-hr treatment with various concentrations of 3-nitropropionic acid(3-NPA, 0.1-0.5 mM) or malonate (10-50 mM), irreversible and reversible inhibitors of the Krebs cycle enzyme, succinate dehydrogenase. Cell damage to the DA and GABA populations was assessed after a 48-hr recovery period by simultaneous measurement of high affinity uptake for 3H-DA and 14C-GABA. 3-NPA or malonate caused a dose-dependent loss of DA uptake (EC50 0.21 or 42 mM, respectively). 3-NPA treatment was equally detrimental to the GABA population, whereas malonate exposure did not cause any significant loss of GABA uptake. The presence of the NMDA antagonist, MK-801 (1 microM), during 24 hr of 3-NPA or malonate treatment fully protected against DA and GABA loss with 50 mM malonate or 0.25 mM 3-NPA and partially protected versus 0.5 mM 3-NPA. To determine the degree of metabolic stress imposed by 3-NPA and malonate, 12-day-old cultures were treated with 0.5 mM 3-NPA or 50 mM malonate for 3 hr and the rate of lactate formation was measured. lactate was increased nearly 2-fold at 3 hr of treatment with 3-NPA, but was not significantly elevated above basal with malonate treatment. SDH activity was decreased by 48 or 58% after 3 hr of treatment with 0.25 and 0.5 mM 3-NPA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and gamma-vinyl-gamma-aminobutyric acid (gamma-vinyl GABA) alter neurotransmitter concentrations in the nervous tissue of the goldfish (Carassius auratus) but not the cockroach (Periplaneta americana).

    PubMed

    Sloley, B D; McKenna, K F

    1993-02-01

    1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-methyl-4-phenylpyridinium iodide (MPP+) and gamma-vinyl-gamma-aminobutyric acid (gamma-vinyl GABA) are drugs demonstrated to alter catecholamine or gamma-aminobutyric acid (GABA) concentrations in vertebrate nervous tissue. MPTP and MPP+, which are potent and selective vertebrate neurotoxins, are effective in depleting noradrenaline and dopamine concentrations in goldfish. However, only MPP+ depletes dopamine in the central nervous tissues of the cockroach, and only when injected directly into the nervous tissue. Systemic injection of gamma-vinyl GABA, a selective GABA transaminase inhibitor in vertebrates, increases GABA concentrations in goldfish but not cockroach nervous tissue. Incubations of both goldfish hypothalamus and cockroach nervous tissue demonstrated the presence of GABA transaminase activity in vitro. However, the GABA transaminase activity obtained from goldfish tissues was much more sensitive to inhibition by gamma-vinyl GABA than that obtained from cockroach nervous tissue. These results demonstrate that MPTP, MPP+ and gamma-vinyl GABA are useful pharmacological tools which can alter neurotransmitter concentrations in a lower vertebrate. Unfortunately, they possess limited effectiveness in the cockroach.

  18. An Electrostatic Funnel in the GABA-Binding Pathway

    PubMed Central

    Lightstone, Felice C.

    2016-01-01

    The γ-aminobutyric acid type A receptor (GABAA-R) is a major inhibitory neuroreceptor that is activated by the binding of GABA. The structure of the GABAA-R is well characterized, and many of the binding site residues have been identified. However, most of these residues are obscured behind the C-loop that acts as a cover to the binding site. Thus, the mechanism by which the GABA molecule recognizes the binding site, and the pathway it takes to enter the binding site are both unclear. Through the completion and detailed analysis of 100 short, unbiased, independent molecular dynamics simulations, we have investigated this phenomenon of GABA entering the binding site. In each system, GABA was placed quasi-randomly near the binding site of a GABAA-R homology model, and atomistic simulations were carried out to observe the behavior of the GABA molecules. GABA fully entered the binding site in 19 of the 100 simulations. The pathway taken by these molecules was consistent and non-random; the GABA molecules approach the binding site from below, before passing up behind the C-loop and into the binding site. This binding pathway is driven by long-range electrostatic interactions, whereby the electrostatic field acts as a ‘funnel’ that sweeps the GABA molecules towards the binding site, at which point more specific atomic interactions take over. These findings define a nuanced mechanism whereby the GABAA-R uses the general zwitterionic features of the GABA molecule to identify a potential ligand some 2 nm away from the binding site. PMID:27119953

  19. Cytoskeletal rearrangement and Src and PI-3K-dependent Akt activation control GABA(B)R-mediated chemotaxis.

    PubMed

    Barati, Michelle T; Lukenbill, Janice; Wu, Rui; Rane, Madhavi J; Klein, Jon B

    2015-06-01

    The γ-amino butyric acid (GABA) type B receptors (GABA(B)R) function as chemoattractant receptors in response to GABA(B)R agonists in human neutrophils. The goal of this study was to define signaling mechanisms regulating GABA(B)R-mediated chemotaxis and cytoskeletal rearrangement. In a proteomic study we identified serine/threonine kinase Akt, tyrosine kinases Src and Pyk2, microtubule regulator kinesin and microtubule affinity-regulating kinase (MARK) co-immunoprecipitating with GABA(B)R. To define the contributions of these candidate signaling events in GABA(B)R-mediated chemotaxis, we used rat basophilic leukemic cells (RBL-2H3 cells) stably transfected with human GABA(B1b) and GABA(B2) receptors. The GABA(B)R agonist baclofen induced Akt phosphorylation and chemotaxis by binding to its specific GABA(B)R since pretreatment of cells with CGP52432, a GABA(B)R antagonist, blocked such effects. Moreover, baclofen induced Akt phosphorylation was shown to be dependent upon PI-3K and Src kinases. Baclofen failed to stimulate actin polymerization in suspended RBL cells unless exposed to a baclofen gradient. However, baclofen stimulated both actin and tubulin polymerization in adherent RBL-GABA(B)R cells. Blockade of actin and tubulin polymerization by treatment of cells with cytochalasin D or nocodazole respectively, abolished baclofen-mediated chemotaxis. Furthermore, baclofen stimulated Pyk2 and STAT3 phosphorylation, both known regulators of cell migration. In conclusion, GABA(B)R stimulation promotes chemotaxis in RBL cells which is dependent on signaling via PI3-K/Akt, Src kinases and on rearrangement of both microtubules and actin cytoskeleton. These data define mechanisms of GABA(B)R-mediated chemotaxis which may potentially be used to therapeutically regulate cellular response to injury and disease.

  20. Synthesis and evaluation of novel heteroaromatic substrates of GABA aminotransferase

    PubMed Central

    Hawker, Dustin D.; Silverman, Richard B.

    2012-01-01

    Two principal neurotransmitters are involved in the regulation of mammalian neuronal activity, namely, γ-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. PMID:22944334

  1. Inhibition of recombinant N-type and native high voltage-gated neuronal Ca{sup 2+} channels by AdGABA: Mechanism of action studies

    SciTech Connect

    Martinez-Hernandez, Elizabeth; Sandoval, Alejandro; Gonzalez-Ramirez, Ricardo; Zoidis, Grigoris; Felix, Ricardo

    2011-02-01

    High-voltage activated Ca{sup 2+} (Ca{sub V}) channels play a key role in the regulation of numerous physiological events by causing transient changes in the intracellular Ca{sup 2+} concentration. These channels consist of a pore-forming Ca{sub V}{alpha}{sub 1} protein and three auxiliary subunits (Ca{sub V}{beta}, Ca{sub V}{alpha}{sub 2}{delta} and Ca{sub V}{gamma}). Ca{sub V}{alpha}{sub 2}{delta} is an important component of Ca{sub V} channels in many tissues and of great interest as a drug target. It is well known that anticonvulsant agent gabapentin (GBP) binds to Ca{sub V}{alpha}{sub 2}{delta} and reduces Ca{sup 2+} currents by modulating the expression and/or function of the Ca{sub V}{alpha}{sub 1} subunit. Recently, we showed that an adamantane derivative of GABA, AdGABA, has also inhibitory effects on Ca{sub V} channels. However, the importance of the interaction of AdGABA with the Ca{sub V}{alpha}{sub 2}{delta} subunit has not been conclusively demonstrated and the mechanism of action of the drug has yet to be elucidated. Here, we describe studies on the mechanism of action of AdGABA. Using a combined approach of patch-clamp recordings and molecular biology we show that AdGABA inhibits Ca{sup 2+} currents acting on Ca{sub V}{alpha}{sub 2}{delta} only when applied chronically, both in a heterologous expression system and in dorsal root-ganglion neurons. AdGABA seems to require uptake and be acting intracellularly given that its effects are prevented by an inhibitor of the L-amino acid transport system. Interestingly, a mutation in the Ca{sub V}{alpha}{sub 2}{delta} that abolishes GBP binding did not affect AdGABA actions, revealing that its mechanism of action is similar but not identical to that of GBP. These results indicate that AdGABA is an important Ca{sub V}{alpha}{sub 2}{delta} ligand that regulates Ca{sub V} channels.

  2. Involvement of glutamate and gamma-aminobutyric acid (GABA)-ergic systems in thyrotropin-releasing hormone-induced rat cerebellar cGMP formation.

    PubMed

    Nakayama, T; Hashimoto, T; Nagai, Y

    1996-12-05

    The increase in cyclic guanosine 3',5'-monophosphate (cGMP) caused by subcutaneous injection of thyrotropin-releasing hormone (TRH) tartrate was observed in a region-specific manner in the rat cerebellum. TRH tartrate (TRH-T) (2.8, 7.0 and 17 mg/kg as free TRH, s.c.) produced dose-dependent increases in cGMP levels markedly in the cerebellar superior and inferior vermis, and a smaller but still significant increase in the cerebellar hemispheres and brainstem but no significant increases in other brain regions. The TRH-induced increase in the cGMP level in the cerebellum was suppressed by pretreatment with muscimol, THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3(2H)-one) or MK-801 (dizocilpine maleate) and partially suppressed by atropine but was not suppressed by chlordiazepoxide, oxazepam, phentolamine, propranolol, cyproheptadine, haloperidol, baclofen or DNQX (6,7-dinitroquinoxaline-2,3-dione), suggesting the possible involvement of GABA (gamma-aminobutyric acid)(A)-ergic, N-methyl-D-aspartate (NMDA)-type glutamatergic and cholinergic systems. These results suggest that excitatory amino acids may be involved in the cGMP formation caused by TRH in the cerebellar areas, and that cGMP formation is inhibited by enhancement of GABAA receptor function.

  3. trans-4-Amino-2-methylbut-2-enoic acid (2-MeTACA) and (+/-)-trans-2-aminomethylcyclopropanecarboxylic acid ((+/-)-TAMP) can differentiate rat rho3 from human rho1 and rho2 recombinant GABA(C) receptors.

    PubMed

    Vien, Jimmy; Duke, Rujee K; Mewett, Kenneth N; Johnston, Graham A R; Shingai, Ryuzo; Chebib, Mary

    2002-02-01

    1. This study investigated the effects of a number of GABA analogues on rat rho3 GABA(C) receptors expressed in Xenopus oocytes using 2-electrode voltage clamp methods. 2. The potency order of agonists was muscimol (EC(50)=1.9 +/- 0.1 microM) (+)-trans-3-aminocyclopentanecarboxylic acids ((+)-TACP; EC(50)=2.7 +/- 0.9 microM) trans-4-aminocrotonic acid (TACA; EC(50)=3.8 +/-0.3 microM) GABA (EC(50)=4.0 +/- 0.3 microM) > thiomuscimol (EC(50)=24.8 +/- 2.6 microM) > (+/-)-cis-2-aminomethylcyclopropane-carboxylic acid ((+/-)-CAMP; EC(50)=52.6 +/-8.7 microM) > cis-4-aminocrotonic acid (CACA; EC(50)=139.4 +/- 5.2 microM). 3. The potency order of antagonists was (+/-)-trans-2-aminomethylcyclopropanecarboxylic acid ((+/-)-TAMP; K(B)=4.8+/-1.8 microM) (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA; K(B)=4.8 +/-0.8 microM) > (piperidin-4-yl)methylphosphinic acid (P4MPA; K(B)=10.2+/-2.3 microM) 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP; K(B)=10.2+/-0.3 microM) imidazole-4-acetic acid (I4AA; K(B)=12.6+/-2.7 microM) > 3-aminopropylphosphonic acid (3-APA; K(B)=35.8+/-13.5 microM). 4. trans-4-Amino-2-methylbut-2-enoic acid (2-MeTACA; 300 microM) had no effect as an agonist or an antagonist indicating that the C2 methyl substituent is sterically interacting with the ligand-binding site of rat rho3 GABA(C) receptors. 5. 2-MeTACA affects rho1 and rho2 but not rho3 GABA(C) receptors. In contrast, (plus minus)-TAMP is a partial agonist at rho1 and rho2 GABA(C) receptors, while at rat rho3 GABA(C) receptors it is an antagonist. Thus, 2-MeTACA and (+/-)-TAMP could be important pharmacological tools because they may functionally differentiate between rho1, rho2 and rho3 GABA(C) receptors in vitro.

  4. Stoichiometry of expressed alpha(4)beta(2)delta gamma-aminobutyric acid type A receptors depends on the ratio of subunit cDNA transfected.

    PubMed

    Wagoner, Kelly R; Czajkowski, Cynthia

    2010-05-07

    The gamma-aminobutyric acid type A receptor (GABA(A)R) is the target of many depressants, including benzodiazepines, anesthetics, and alcohol. Although the highly prevalent alphabetagamma GABA(A)R subtype mediates the majority of fast synaptic inhibition in the brain, receptors containing delta subunits also play a key role, mediating tonic inhibition and the actions of endogenous neurosteroids and alcohol. However, the fundamental properties of delta-containing GABA(A)Rs, such as subunit stoichiometry, are not well established. To determine subunit stoichiometry of expressed delta-containing GABA(A)Rs, we inserted the alpha-bungarotoxin binding site tag in the alpha(4), beta(2), and delta subunit N termini. An enhanced green fluorescent protein tag was also inserted into the beta(2) subunit to shift its molecular weight, allowing us to separate subunits using SDS-PAGE. Tagged alpha(4)beta(2)delta GABA(A)Rs were expressed in HEK293T cells using various ratios of subunit cDNA, and receptor subunit stoichiometry was determined by quantitating fluorescent alpha-bungarotoxin bound to each subunit on Western blots of surface immunopurified tagged GABA(A)Rs. The results demonstrate that the subunit stoichiometry of alpha(4)beta(2)delta GABA(A)Rs is regulated by the ratio of subunit cDNAs transfected. Increasing the ratio of delta subunit cDNA transfected increased delta subunit incorporation into surface receptors with a concomitant decrease in beta(2) subunit incorporation. Because receptor subunit stoichiometry can directly influence GABA(A)R pharmacological and functional properties, considering how the transfection protocols used affect subunit stoichiometry is essential when studying heterologously expressed alpha(4)beta(2)delta GABA(A)Rs. Successful bungarotoxin binding site tagging of GABA(A)R subunits is a novel tool with which to accurately quantitate subunit stoichiometry and will be useful for monitoring GABA(A)R trafficking in live cells.

  5. Enhancement of GABA release through endogenous activation of axonal GABA(A) receptors in juvenile cerebellum.

    PubMed

    Trigo, Federico F; Chat, Mireille; Marty, Alain

    2007-11-14

    Recent evidence indicates the presence of presynaptic GABA(A) receptors (GABA(A)Rs) in the axon domain of several classes of central neurons, including cerebellar basket and stellate cells. Here, we investigate the possibility that these receptors could be activated in the absence of electrical or chemical stimulation. We find that low concentrations of GABA increase the frequency of miniature GABAergic synaptic currents. Submaximal concentrations of a GABA(A)R blocker, gabazine, decrease both the miniature current frequency and the probability of evoked GABA release. Zolpidem, an agonist of the benzodiazepine binding site, and NO-711 (1-[2-[[(diphenylmethylene)imino]oxy]ethyl]-1,2,5,6-tetrahydro-3-pyridinecarboxylic acid hydrochloride), a blocker of GABA uptake, both increase the frequency of miniature currents. These effects occur up to postnatal day 14, but not later. Immunohistochemistry indicates the presence of alpha1-containing GABA(A)Rs in interneuron presynaptic terminals with a similar age dependence. We conclude that, under resting conditions, axonal GABA(A)Rs are significantly activated, that this activation results in enhanced GABA release, and that it can be augmented by increasing the affinity of GABA(A)Rs or reducing GABA uptake. Our findings suggest the existence of a positive-feedback mechanism involving presynaptic GABA(A)Rs that maintains a high release rate and a high local GABA concentration in the immature cerebellar network.

  6. Blockade of GABA, type A, receptors in the rat pontine reticular formation induces rapid eye movement sleep that is dependent upon the cholinergic system.

    PubMed

    Marks, G A; Sachs, O W; Birabil, C G

    2008-09-22

    The brainstem reticular formation is an area important to the control of rapid eye movement (REM) sleep. The antagonist of GABA-type A (GABA(A)) receptors, bicuculline methiodide (BMI), injected into the rat nucleus pontis oralis (PnO) of the reticular formation resulted in a long-lasting increase in REM sleep. Thus, one factor controlling REM sleep appears to be the number of functional GABA(A) receptors in the PnO. The long-lasting effect produced by BMI may result from secondary influences on other neurotransmitter systems known to have long-lasting effects. To study this question, rats were surgically prepared for chronic sleep recording and additionally implanted with guide cannulas aimed at sites in the PnO. Multiple, 60 nl, unilateral injections were made either singly or in combination. GABA(A) receptor antagonists, BMI and gabazine (GBZ), produced dose-dependent increases in REM sleep with GBZ being approximately 35 times more potent than BMI. GBZ and the cholinergic agonist, carbachol, produced very similar results, both increasing REM sleep for about 8 h, mainly through increased period frequency, with little reduction in REM latency. Pre-injection of the muscarinic antagonist, atropine, completely blocked the REM sleep-increase by GBZ. GABAergic control of REM sleep in the PnO requires the cholinergic system and may be acting through presynaptic modulation of acetylcholine release.

  7. Basic aspects of GABA-transmission in alcoholism, with particular reference to GABA-transaminase.

    PubMed

    Sherif, F M; Tawati, A M; Ahmed, S S; Sharif, S I

    1997-02-01

    Neuronal dysfunction is the neurobiological basis for alcoholic behaviour, and ethanol craving seems related to hypofunction of the GABA-ergic activity. Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system (CNS). In several studies, GABA has been shown to be an important target of ethanol in the CNS, partly, as a consequence of damage to membrane-bound enzymes and receptors. GABA is involved in mediating pre- and post-synaptic inhibition of neuronal activity. It is speculated that the initial excitatory effects of ethanol may be due to inhibition of GABA-ergic activity whereas the sedative effects of the higher doses may be mediated by the activation of this inhibitory system. In the CNS, GABA is synthesised from glutamic acid by the enzyme glutamate decarboxylase (GAD) and catabolized into succinic semialdehyde by the enzyme GABA-transaminase (GABA-T), which are pyridoxal phosphate (PLP) dependent enzymes. Platelet GABA-T was characterized as being similar to central GABA-T. Inhibition of GABA-T with certain potent and selective compounds markedly increases the levels of brain GABA. Experimentally, acute ethanol treatment does not alter GABA-T activity whereas chronic treatment produces an increase in the activity, though, with some reservations since a bimodal effect has been found in chronically ethanol-treated rats. Thus, as it will be discussed below, it may be suggested that GABA-T inhibitors (e.g. vigabatrin) could have a potential role in the treatment of alcoholism and in some of the problems of ethanol withdrawal and of other drugs of abuse. Related studies on metabolism and concentrations of GABA are also promising and show a greater increase in our understanding of the aetiology and treatment of ethanol dependence and withdrawal. In general, this article also reviews both the animal and clinical observations in the field of alcoholism with regard to the GABA system.

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

    PubMed

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

    2002-04-01

    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

  9. Closing the loop on the GABA shunt in plants: are GABA metabolism and signaling entwined?

    PubMed Central

    Michaeli, Simon; Fromm, Hillel

    2015-01-01

    γ-Aminobutyric acid (GABA) is a non-proteinogenic amino acid that is found in uni- and multi-cellular organisms and is involved in many aspects of plant life cycle. GABA metabolism occurs by the action of evolutionary conserved enzymes that constitute the GABA shunt, bypassing two steps of the TCA cycle. The central position of GABA in the interface between plant carbon and nitrogen metabolism is well established. In parallel, there is evidence to support a role for GABA as a signaling molecule in plants. Here we cover some of the recent findings on GABA metabolism and signaling in plants and further suggest that the metabolic and signaling aspects of GABA may actually be inseparable. PMID:26106401

  10. Drug interactions at GABA(A) receptors.

    PubMed

    Korpi, Esa R; Gründer, Gerhard; Lüddens, Hartmut

    2002-06-01

    Neurotransmitter receptor systems have been the focus of intensive pharmacological research for more than 20 years for basic and applied scientific reasons, but only recently has there been a better understanding of their key features. One of these systems includes the type A receptor for the gamma-aminobutyric acid (GABA), which forms an integral anion channel from a pentameric subunit assembly and mediates most of the fast inhibitory neurotransmission in the adult vertebrate central nervous system. Up to now, depending on the definition, 16-19 mammalian subunits have been cloned and localized on different genes. Their assembly into proteins in a poorly defined stoichiometry forms the basis of functional and pharmacological GABA(A) receptor diversity, i.e. the receptor subtypes. The latter has been well documented in autoradiographic studies using ligands that label some of the receptors' various binding sites, corroborated by recombinant expression studies using the same tools. Significantly less heterogeneity has been found at the physiological level in native receptors, where the subunit combinations have been difficult to dissect. This review focuses on the characteristics, use and usefulness of various ligands and their binding sites to probe GABA(A) receptor properties and to gain insight into the biological function from fish to man and into evolutionary conserved GABA(A) receptor heterogeneity. We also summarize the properties of the novel mouse models created for the study of various brain functions and review the state-of-the-art imaging of brain GABA(A) receptors in various human neuropsychiatric conditions. The data indicate that the present ligands are only partly satisfactory tools and further ligands with subtype-selective properties are needed for imaging purposes and for confirming the behavioral and functional results of the studies presently carried out in gene-targeted mice with other species, including man.

  11. Dodecyl Maltopyranoside Enabled Purification of Active Human GABA Type A Receptors for Deep and Direct Proteomic Sequencing*

    PubMed Central

    Zhang, Xi; Miller, Keith W.

    2015-01-01

    The challenge in high-quality membrane proteomics is all about sample preparation prior to HPLC, and the cell-to-protein step poses a long-standing bottleneck. Traditional protein extraction methods apply ionic or poly-disperse detergents, harsh denaturation, and repeated protein/peptide precipitation/resolubilization afterward, but suffer low yield, low reproducibility, and low sequence coverage. Contrary to attempts to subdue, we resolved this challenge by providing proteins nature-and-activity-promoting conditions throughout preparation. Using 285-kDa hetero-pentameric human GABA type A receptor overexpressed in HEK293 as a model, we describe a n-dodecyl-β-d-maltopyranoside/cholesteryl hemisuccinate (DDM/CHS)-based affinity purification method, that produced active receptors, supported protease activity, and allowed high performance with both in-gel and direct gel-free proteomic analyses—without detergent removal. Unlike conventional belief that detergents must be removed before HPLC MS, the high-purity low-dose nonionic detergent DDM did not interfere with peptides, and obviated removal or desalting. Sonication or dropwise addition of detergent robustly solubilized over 90% of membrane pellets. The purification conditions were comparable to those applied in successful crystallizations of most membrane proteins. These results enabled streamlined proteomics of human synaptic membrane proteins, and more importantly, allowed directly coupling proteomics with crystallography to characterize both static and dynamic structures of membrane proteins in crystallization pipelines. PMID:25473089

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

    PubMed

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

    2010-02-28

    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.

  13. Glutamate and GABA-metabolizing enzymes in post-mortem cerebellum in Alzheimer's disease: phosphate-activated glutaminase and glutamic acid decarboxylase.

    PubMed

    Burbaeva, G Sh; Boksha, I S; Tereshkina, E B; Savushkina, O K; Prokhorova, T A; Vorobyeva, E A

    2014-10-01

    Enzymes of glutamate and GABA metabolism in postmortem cerebellum from patients with Alzheimer's disease (AD) have not been comprehensively studied. The present work reports results of original comparative study on levels of phosphate-activated glutaminase (PAG) and glutamic acid decarboxylase isoenzymes (GAD65/67) in autopsied cerebellum samples from AD patients and matched controls (13 cases in each group) as well as summarizes published evidence for altered levels of PAG and GAD65/67 in AD brain. Altered (decreased) levels of these enzymes and changes in links between amounts of these enzymes and other glutamate-metabolizing enzymes (such as glutamate dehydrogenase and glutamine synthetase-like protein) in AD cerebella suggest significantly impaired glutamate and GABA metabolism in this brain region, which was previously regarded as not substantially involved in AD pathogenesis.

  14. GABA is the principal fast-acting excitatory transmitter in the neonatal brain.

    PubMed

    Leinekugel, X; Khalilov, I; McLean, H; Caillard, O; Gaiarsa, J L; Ben-Ari, Y; Khazipov, R

    1999-01-01

    gamma-aminobutyric acid (GABA) is the principal neurotransmitter of inhibition in the adult mammalian brain. However, at early stages of development, including the embryonic period and first week of postnatal life, GABA plays the role of main neurotransmitter of excitation. The paradoxical excitatory effect of GABA is caused by an inverted chloride gradient and, therefore, a depolarizing direction of GABA type A (GABAA) receptor mediated responses. In addition, another type of GABAergic inhibition mediated by postsynaptic GABA type B (GABAB) receptors is not functional at early stage of life. In the neonatal rat hippocampus, GABA, acting via GABAA receptors, activates voltage-gated sodium and calcium channels and potentiates the activity of N-methyl-D-aspartate (NMDA) receptors by reducing their voltage-dependent Mg2+ block. The temporal window when GABA exerts excitatory actions coincides with a particular pattern of activity of hippocampal neuronal network that is characterized by periodical giant depolarizing potentials (GDPs) reminiscent of interictal-like epileptiform discharges. Recent studies have shown that GDPs result from the synchronous discharge of GABAergic interneurons and principal glutamatergic pyramidal cells, and they are mediated by the synergistic excitatory actions of GABAA and glutamate receptors. GDPs provide synchronous intracellular Ca2+ oscillations and may, therefore, be implicated in hebbian modulation of developing synapses and activity-dependent formation of the hippocampal network.

  15. Multiple motifs regulate the trafficking of GABA(B) receptors at distinct checkpoints within the secretory pathway.

    PubMed

    Restituito, Sophie; Couve, Andrés; Bawagan, Hinayana; Jourdain, Sabine; Pangalos, Menelas N; Calver, Andrew R; Freeman, Katie B; Moss, Stephen J

    2005-04-01

    gamma-Aminobutyric acid type B receptors (GABA(B)) are G-protein-coupled receptors that mediate GABAergic inhibition in the brain. Their functional expression is dependent upon the formation of heterodimers between GABA(B)R1 and GABA(B)R2 subunits, a process that occurs within the endoplasmic reticulum (ER). However, the mechanisms that regulate receptor surface expression remain largely unknown. Here, we demonstrate that access to the cell surface for GABA(B)R1 is sequentially controlled by an RSR(R) motif and a LL motif within its cytoplasmic domain. In addition, we reveal that msec7-1, a guanine-nucleotide-exchange factor (GEF) for the ADP-ribosylation factor (ARF) family of GTPases, critical regulators of vesicular membrane trafficking, interacts with GABA(B)R1 via the LL motif in this subunit. Finally, we establish that msec7-1 modulates the cell surface expression of GABA(B) receptors, a process that is dependent upon the integrity of the LL motif in GABA(B)R1. Together, our results demonstrate that the cell surface expression of the GABA(B)R1 subunit is regulated by multiple motifs, which act at distinct checkpoints in the secretory pathway, and also suggest a novel role for msec7-1 in regulating the membrane trafficking of GABA(B)R1 subunits.

  16. GABA interaction with lipids in organic medium

    SciTech Connect

    Beltramo, D.; Kivatinitz, S.; Lassaga, E.; Arce, A.

    1987-08-10

    The interaction of TH-GABA and UC-glutamate with lipids in an aqueous organic partition system was studied. With this partition system TH-GABA and UC-glutamate were able to interact with sphingomyelin, sulfatide, phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine and phosphatidic acid but not with cholesterol or ceramide. In an homogeneous aqueous medium the authors could not demonstrate any interaction between TH-GABA-lipids. The apparent dissociation constants (K/sub d/) for TH-GABA-lipids or UC-glutamate-lipids interactions inorganic medium were in the millimolar range and maximal charge between 3 and 7 moles of GABA or glutamate by mole of lipid. Amino acids such as glutamic acid, US -alanine and glycine displaced TH-GABA with the same potency as GABA itself; thus these results show that the interaction lacks pharmacological specificity. To detect this interaction lipid concentrations higher than 2 M were required and in the partition system TH-GABA and lipid phosphorus were both concentrated at the interface. Therefore, lipids tested with a biphasic partition system do not fulfill the classical criteria for a neurotransmitter receptor at least not for GABA and glutamate. 15 references, 1 figure, 3 tables.

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

    SciTech Connect

    Kamei, Yuka; Tamura, Takayuki; Yoshida, Ryo; Ohta, Shinji; Fukusaki, Eiichiro; Mukai, Yukio

    2011-04-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  19. Low nanomolar GABA effects at extrasynaptic α4β1/β3δ GABA(A) receptor subtypes indicate a different binding mode for GABA at these receptors.

    PubMed

    Karim, Nasiara; Wellendorph, Petrine; Absalom, Nathan; Bang, Line Haunstrup; Jensen, Marianne Lerbech; Hansen, Maja Michelle; Lee, Ho Joon; Johnston, Graham A R; Hanrahan, Jane R; Chebib, Mary

    2012-08-15

    Ionotropic GABA(A) receptors are a highly heterogenous population of receptors assembled from a combination of multiple subunits. The aims of this study were to characterize the potency of GABA at human recombinant δ-containing extrasynaptic GABA(A) receptors expressed in Xenopus oocytes using the two-electrode voltage clamp technique, and to investigate, using site-directed mutagenesis, the molecular determinants for GABA potency at α4β3δ GABA(A) receptors. α4/δ-Containing GABA(A) receptors displayed high sensitivity to GABA, with mid-nanomolar concentrations activating α4β1δ (EC₅₀=24 nM) and α4β3δ (EC₅₀=12 nM) receptors. In the majority of oocytes expressing α4β3δ subtypes, GABA produced a biphasic concentration-response curve, and activated the receptor with low and high concentrations (EC₅₀(1)=16 nM; EC₅₀(2)=1.2 μM). At α4β2δ, GABA had low micromolar activity (EC₅₀=1 μM). An analysis of 10 N-terminal singly mutated α4β3δ receptors shows that GABA interacts with amino acids different to those reported for α1β2γ2 GABA(A) receptors. Residues Y205 and R207 of the β3-subunit significantly affected GABA potency, while the residue F71 of the α4- and the residue Y97 of the β3-subunit did not significantly affect GABA potency. Mutating the residue R218 of the δ-subunit, equivalent to the GABA binding residue R207 of the β2-subunit, reduced the potency of GABA by 670-fold, suggesting a novel GABA binding site at the δ-subunit interface. Taken together, GABA may have different binding modes for extrasynaptic δ-containing GABA(A) receptors compared to their synaptic counterparts.

  20. L-DOPA Reverses the Increased Free Amino Acids Tissue Levels Induced by Dopamine Depletion and Rises GABA and Tyrosine in the Striatum.

    PubMed

    Solís, Oscar; García-Sanz, Patricia; Herranz, Antonio S; Asensio, María-José; Moratalla, Rosario

    2016-07-01

    Perturbations in the cerebral levels of various amino acids are associated with neurological disorders, and previous studies have suggested that such alterations have a role in the motor and non-motor symptoms of Parkinson's disease. However, the direct effects of chronic L-DOPA treatment, that produces dyskinesia, on neural tissue amino acid concentrations have not been explored in detail. To evaluate whether striatal amino acid concentrations are altered in peak dose dyskinesia, 6-hydroxydopamine (6-OHDA)-lesioned hemiparkinsonian mice were treated chronically with L-DOPA and tissue amino acid concentrations were assessed by HPLC analysis. These experiments revealed that neither 6-OHDA nor L-DOPA treatment are able to alter glutamate in the striatum. However, glutamine increases after 6-OHDA and returns back to normal levels with L-DOPA treatment, suggesting increased striatal glutamatergic transmission with lack of dopamine. In addition, glycine and taurine levels are increased following dopamine denervation and restored to normal levels by L-DOPA. Interestingly, dyskinetic animals showed increased levels of GABA and tyrosine, while aspartate striatal tissue levels are not altered. Overall, our results indicate that chronic L-DOPA treatment, besides normalizing the altered levels of some amino acids after 6-OHDA, robustly increases striatal GABA and tyrosine levels which may in turn contribute to the development of L-DOPA-induced dyskinesia.

  1. GABA(B2) is essential for g-protein coupling of the GABA(B) receptor heterodimer.

    PubMed

    Robbins, M J; Calver, A R; Filippov, A K; Hirst, W D; Russell, R B; Wood, M D; Nasir, S; Couve, A; Brown, D A; Moss, S J; Pangalos, M N

    2001-10-15

    GABA(B) receptors are unique among G-protein-coupled receptors (GPCRs) in their requirement for heterodimerization between two homologous subunits, GABA(B1) and GABA(B2), for functional expression. Whereas GABA(B1) is capable of binding receptor agonists and antagonists, the role of each GABA(B) subunit in receptor signaling is unknown. Here we identified amino acid residues within the second intracellular domain of GABA(B2) that are critical for the coupling of GABA(B) receptor heterodimers to their downstream effector systems. Our results provide strong evidence for a functional role of the GABA(B2) subunit in G-protein coupling of the GABA(B) receptor heterodimer. In addition, they provide evidence for a novel "sequential" GPCR signaling mechanism in which ligand binding to one heterodimer subunit can induce signal transduction through the second partner of a heteromeric complex.

  2. Activation of NPY type 5 receptors induces a long-lasting increase in spontaneous GABA release from cerebellar inhibitory interneurons

    PubMed Central

    Dubois, C. J.; Ramamoorthy, P.; Whim, M. D.

    2012-01-01

    Neuropeptide Y (NPY), a widely distributed neuropeptide in the central nervous system, can transiently suppress inhibitory synaptic transmission and alter membrane excitability via Y2 and Y1 receptors (Y2rs and Y1rs), respectively. Although many GABAergic neurons express Y5rs, the functional role of these receptors in inhibitory neurons is not known. Here, we investigated whether activation of Y5rs can modulate inhibitory transmission in cerebellar slices. Unexpectedly, application of NPY triggered a long-lasting increase in the frequency of miniature inhibitory postsynaptic currents in stellate cells. NPY also induced a sustained increase in spontaneous GABA release in cultured cerebellar neurons. When cerebellar cultures were examined for Y5r immunoreactivity, the staining colocalized with that of VGAT, a presynaptic marker for GABAergic cells, suggesting that Y5rs are located in the presynaptic terminals of inhibitory neurons. RT-PCR experiments confirmed the presence of Y5r mRNA in the cerebellum. The NPY-induced potentiation of GABA release was blocked by Y5r antagonists and mimicked by application of a selective peptide agonist for Y5r. Thus Y5r activation is necessary and sufficient to trigger an increase in GABA release. Finally, the potentiation of inhibitory transmission could not be reversed by a Y5r antagonist once it was initiated, consistent with the development of a long-term potentiation. These results indicate that activation of presynaptic Y5rs induces a sustained increase in spontaneous GABA release from inhibitory neurons in contrast to the transient suppression of inhibitory transmission that is characteristic of Y1r and Y2r activation. Our findings thus reveal a novel role of presynaptic Y5rs in inhibitory interneurons in regulating GABA release and suggest that these receptors could play a role in shaping neuronal network activity in the cerebellum. PMID:22190627

  3. γ-Aminobutyric Acid (GABA) Production and Angiotensin-I Converting Enzyme (ACE) Inhibitory Activity of Fermented Soybean Containing Sea Tangle by the Co-Culture of Lactobacillus brevis with Aspergillus oryzae.

    PubMed

    Jang, Eun Kyeong; Kim, Nam Yeun; Ahn, Hyung Jin; Ji, Geun Eog

    2015-08-01

    To enhance the γ-aminobutyric acid (GABA) content, the optimized fermentation of soybean with added sea tangle extract was evaluated at 30°C and pH 5.0. The medium was first inoculated with Aspergillus oryzae strain FMB S46471 and fermented for 3 days, followed by the subsequent inoculation with Lactobacillus brevis GABA 100. After fermentation for 7 days, the fermented soybean showed approximately 1.9 g/kg GABA and exhibited higher ACE inhibitory activity than the traditional soybean product. Furthermore, several peptides in the fraction containing the highest ACE inhibitory activity were identified. The novel fermented soybean enriched with GABA and ACE inhibitory components has great pharmaceutical and functional food values.

  4. Kinetic studies on the inhibition of GABA-T by gamma-vinyl GABA and taurine.

    PubMed

    Sulaiman, Saba A J; Suliman, Fakhr Eldin O; Barghouthi, Samira

    2003-08-01

    Gamma-aminobutyric acid transaminase (GABA-T, EC 2.6.1.19) is a pyridoxal phosphate (PLP) dependent enzyme that catalyzes the degradation of gamma-aminobutyric acid. The kinetics of this reaction are studied in vitro, both in the absence, and in the presence of two inhibitors: gamma-vinyl GABA (4-aminohex-5-enoic acid), and a natural product, taurine (ethylamine-2-sulfonic acid). A kinetic model that describes the transamination process is proposed. GABA-T from Pseudomonas fluorescens is inhibited by gamma-vinyl GABA and taurine at concentrations of 51.0 and 78.5 mM. Both inhibitors show competitive inhibition behavior when GABA is the substrate and the inhibition constant (Ki) values for gamma-vinyl GABA and taurine were found to be 26 +/- 3 mM and 68 +/- 7 mM respectively. The transamination process of alpha-ketoglutarate was not affected by the presence of gamma-vinyl GABA, whereas, taurine was a noncompetitive inhibitor of GABA-T when alpha-ketoglutarate was the substrate. The inhibition dissociation constant (Kii) for this system was found to be 96 +/- 10 mM. The Michaelis-Menten constant (Km) in the absence of inhibition, was found to be 0.79 +/- 0.11 mM, and 0.47 +/- 0.10 mM for GABA and alpha-ketoglutarate respectively.

  5. [GABA-ergic system in defense against excitatory kynurenines].

    PubMed

    Lapin, I P

    1997-01-01

    Protection against the excitatory action of L-kynurenine and quinolinic acid in mice is related to the activation of GABA-B and dopamine receptors of the brain and to much lesser degree to the activation of GABA-A receptors. It is hardly believable that the anticonvulsant effect of phenibut (beta-phenyl-GABA), baclofen (CL-phenibut), sodium hydroxybutyrate and taurine against seizures induced by these two kynurenines is determined by alterations in metabolism of GABA.

  6. Prevention of GABA reduction during dough fermentation using a baker's yeast dal81 mutant.

    PubMed

    Ando, Akira; Nakamura, Toshihide

    2016-10-01

    γ-Aminobutyric acid (GABA) is consumed by yeasts during fermentation. To prevent GABA reduction in bread dough, a baker's yeast mutant AY77 deficient in GABA assimilation was characterized and utilized for wheat dough fermentation. An amber mutation in the DAL81 gene, which codes for a positive regulator of multiple nitrogen degradation pathways, was found in the AY77 strain. The qPCR analyses of genes involved in nitrogen utilization showed that transcriptional levels of the UGA1 and DUR3 genes encoding GABA transaminase and urea transporter, respectively, are severely decreased in the AY77 cells. The AY77 strain cultivated by fed-batch culture using cane molasses exhibited inferior gas production during dough fermentation compared to that of wild-type strain AY13. However, when fed with molasses containing 0.5% ammonium sulfate, the mutant strain exhibited gas production comparable to that of the AY13 strain. In contrast to the AY13 strain, which completely consumed GABA in dough within 5 h, the AY77 strain consumed no GABA under either culture condition. Dough fermentation with the dal81 mutant strain should be useful for suppression of GABA reduction in breads.

  7. Neuronal GABA release and GABA inhibition of ACh release in guinea pig urinary bladder.

    PubMed

    Kusunoki, M; Taniyama, K; Tanaka, C

    1984-04-01

    gamma-Aminobutyric acid (GABA) and glutamate decarboxylase (GAD) are present in the urinary bladder of guinea pigs, and the possible correlation in regional distribution between GABA, GAD, and the number of vesical ganglion cells was studied. Electrical stimulation of the bladder strips produced an increase in the calcium-dependent and tetrodotoxin-sensitive [3H]GABA release and contractions in the strips preloaded with [3H]GABA. Nicotine, acetylcholine chloride (ACh), and hexamethonium did not significantly alter the release of [3H]GABA. Bicuculline significantly enhanced [3H]ACh release and cholinergic components of contractions evoked by electrical stimulation of the bladder strips preloaded with [3H]choline, thereby suggesting that this compound antagonizes the effect of endogenous GABA released during stimulation. GABA and muscimol but not baclofen reduced both the [3H]ACh release and contractions evoked by nicotine. These effects of GABA were antagonized by bicuculline and furosemide but not by alpha- and beta-adrenergic blockers. These findings suggest that GABA may be a noncholinergic nonadrenergic inhibitory neurotransmitter in the urinary bladder. The motility of the urinary bladder is thus inhibited by reducing the release of ACh from the postganglionic cholinergic neurons through bicuculline-sensitive GABA receptors probably associated with the chloride ion channel.

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

    PubMed

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

    2013-10-01

    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.

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

    ERIC Educational Resources Information Center

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

    2009-01-01

    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…

  10. GABA: a pioneer transmitter that excites immature neurons and generates primitive oscillations.

    PubMed

    Ben-Ari, Yehezkel; Gaiarsa, Jean-Luc; Tyzio, Roman; Khazipov, Rustem

    2007-10-01

    Developing networks follow common rules to shift from silent cells to coactive networks that operate via thousands of synapses. This review deals with some of these rules and in particular those concerning the crucial role of the neurotransmitter gamma-aminobuytric acid (GABA), which operates primarily via chloride-permeable GABA(A) receptor channels. In all developing animal species and brain structures investigated, neurons have a higher intracellular chloride concentration at an early stage leading to an efflux of chloride and excitatory actions of GABA in immature neurons. This triggers sodium spikes, activates voltage-gated calcium channels, and acts in synergy with NMDA channels by removing the voltage-dependent magnesium block. GABA signaling is also established before glutamatergic transmission, suggesting that GABA is the principal excitatory transmitter during early development. In fact, even before synapse formation, GABA signaling can modulate the cell cycle and migration. The consequence of these rules is that developing networks generate primitive patterns of network activity, notably the giant depolarizing potentials (GDPs), largely through the excitatory actions of GABA and its synergistic interactions with glutamate signaling. These early types of network activity are likely required for neurons to fire together and thus to "wire together" so that functional units within cortical networks are formed. In addition, depolarizing GABA has a strong impact on synaptic plasticity and pathological insults, notably seizures of the immature brain. In conclusion, it is suggested that an evolutionary preserved role for excitatory GABA in immature cells provides an important mechanism in the formation of synapses and activity in neuronal networks.

  11. Differential effects of phosphonic analogues of GABA on GABA(B) autoreceptors in rat neocortical slices.

    PubMed

    Ong, J; Marino, V; Parker, D A; Kerr, D I

    1998-04-01

    The effects of five phosphonic derivatives of GABA on the release of [3H]-GABA from rat neocortical slices, preloaded with [3H]-GABA, were investigated. Phaclofen and 4-aminobutylphosphonic acid (4-ABPA) increased the overflow of [3H] evoked by electrical stimulation (2 Hz) in a concentration-dependent manner, with similar potencies (phaclofen EC50=0.3 mmol/l, 4-ABPA EC50=0.4 mmol/l). At 3 mmol/l, phaclofen increased the release of [3H]-GABA by 82.6+/-8.6%, and 4-ABPA increased the release by 81.3+/-9.0%. 2-Amino-ethylphosphonic acid (2-AEPA) increased the overflow of [3H] by 46.8+/-10.9% at the highest concentration tested (3 mmol/l). In contrast, the lower phosphonic homologue 3-aminopropylphosphonic acid (3-APPA), and 2-amino-2-(p-chlorophenyl)-ethylphosphonic acid (2-CPEPA), a baclofen analogue, did not modify the stimulated overflow. These results suggest that phaclofen, 4-ABPA and 2-AEPA are antagonists at GABA(B) autoreceptors, the latter being the weakest antagonist, whilst neither 3-APPA nor 2-CPEPA are active at these receptors. Since phaclofen, 4-ABPA and 2-CPEPA are antagonists and 3-APPA a partial agonist/antagonist on GABA(B) heteroreceptors, the lack of effect of 3-APPA and 2-CPEPA on [3H]-GABA release in this study suggests that GABA(B) autoreceptors may be pharmacologically distinct from the heteroreceptors.

  12. Phosphatase inhibitors remove the run-down of γ-aminobutyric acid type A receptors in the human epileptic brain

    PubMed Central

    Palma, E.; Ragozzino, D. A.; Di Angelantonio, S.; Spinelli, G.; Trettel, F.; Martinez-Torres, A.; Torchia, G.; Arcella, A.; Di Gennaro, G.; Quarato, P. P.; Esposito, V.; Cantore, G.; Miledi, R.; Eusebi, F.

    2004-01-01

    The properties of γ-aminobutyric acid (GABA) type A receptors (GABAA receptors) microtransplanted from the human epileptic brain to the plasma membrane of Xenopus oocytes were compared with those recorded directly from neurons, or glial cells, in human brains slices. Cell membranes isolated from brain specimens, surgically obtained from six patients afflicted with drug-resistant temporal lobe epilepsy (TLE) were injected into frog oocytes. Within a few hours, these oocytes acquired GABAA receptors that generated GABA currents with an unusual run-down, which was inhibited by orthovanadate and okadaic acid. In contrast, receptors derived from membranes of a nonepileptic hippocampal uncus, membranes from mouse brain, or recombinant rat α1β2γ2-GABA receptors exhibited a much less pronounced GABA-current run-down. Moreover, the GABAA receptors of pyramidal neurons in temporal neocortex slices from the same six epileptic patients exhibited a stronger run-down than the receptors of rat pyramidal neurons. Interestingly, the GABAA receptors of neighboring glial cells remained substantially stable after repetitive activation. Therefore, the excessive GABA-current run-down observed in the membrane-injected oocytes recapitulates essentially what occurs in neurons, rather than in glial cells. Quantitative RT-PCR analyses from the same TLE neocortex specimens revealed that GABAA-receptor β1, β2, β3, and γ2 subunit mRNAs were significantly overexpressed (8- to 33-fold) compared with control autopsy tissues. Our results suggest that an abnormal GABA-receptor subunit transcription in the TLE brain leads to the expression of run-down-enhanced GABAA receptors. Blockage of phosphatases stabilizes the TLE GABAA receptors and strengthens GABAergic inhibition. It may be that this process can be targeted to develop new treatments for intractable epilepsy. PMID:15218107

  13. Influence of GABA and GABA-producing Lactobacillus brevis DPC 6108 on the development of diabetes in a streptozotocin rat model.

    PubMed

    Marques, T M; Patterson, E; Wall, R; O'Sullivan, O; Fitzgerald, G F; Cotter, P D; Dinan, T G; Cryan, J F; Ross, R P; Stanton, C

    2016-06-01

    The aim of this study was to investigate if dietary administration of γ-aminobutyric acid (GABA)-producing Lactobacillus brevis DPC 6108 and pure GABA exert protective effects against the development of diabetes in streptozotocin (STZ)-induced diabetic Sprague Dawley rats. In a first experiment, healthy rats were divided in 3 groups (n=10/group) receiving placebo, 2.6 mg/kg body weight (bw) pure GABA or L. brevis DPC 6108 (~10(9)microorganisms). In a second experiment, rats (n=15/group) were randomised to five groups and four of these received an injection of STZ to induce type 1 diabetes. Diabetic and non-diabetic controls received placebo [4% (w/v) yeast extract in dH2O], while the other three diabetic groups received one of the following dietary supplements: 2.6 mg/kg bw GABA (low GABA), 200 mg/kg bw GABA (high GABA) or ~10(9) L. brevis DPC 6108. L. brevis DPC 6108 supplementation was associated with increased serum insulin levels (P<0.05), but did not alter other metabolic markers in healthy rats. Diabetes induced by STZ injection decreased body weight (P<0.05), increased intestinal length (P<0.05) and stimulated water and food intake. Insulin was decreased (P<0.05), whereas glucose was increased (P<0.001) in all diabetic groups, compared with non-diabetic controls. A decrease (P<0.01) in glucose levels was observed in diabetic rats receiving L. brevis DPC 6108, compared with diabetic-controls. Both the composition and diversity of the intestinal microbiota were affected by diabetes. Microbial diversity in diabetic rats supplemented with low GABA was not reduced (P>0.05), compared with non-diabetic controls while all other diabetic groups displayed reduced diversity (P<0.05). L. brevis DPC 6108 attenuated hyperglycaemia induced by diabetes but additional studies are needed to understand the mechanisms involved in this reduction.

  14. Comparison of γ-Aminobutyric Acid and Biogenic Amine Content of Different types of Ewe’s Milk Cheese Produced in Sardinia, Italy

    PubMed Central

    Porcu, Arianna; Ru, Antonio; Salaris, Margherita; Franco, Mario A.; De Santis, Enrico P.L.

    2015-01-01

    The bioactive compounds γ-aminobutyric acid (GABA) and biogenic amines (BA), together with protein-free amino acids, were measured by high-performance liquid chromatography in ewe’s milk cheeses produced in Sardinia with different technological traits. The study included three types of cheese: Pecorino Sardo PDO, Pecorino and Casu Marzu. Farmhouse Casu Marzu and Pecorino showed GABA content (maximum levels: 1001.3 and 378.1 mg 100 g–1 respectively) that had never been found so high in cheese before, suggesting that these types of cheese present ideal conditions to produce GABA. These two types of cheese also showed high levels of BA (their total maximum levels were 1035.7 and 288.0 mg 100 g–1 respectively). Pearson correlation analysis detected significant correlation between GABA and the main BA present in the cheeses (tyramine, cadaverine and putrescine), suggesting that the factors affecting the production of GABA are the same as those influencing BA formation. PMID:27800396

  15. Role of gamma-aminobutyric acid (GABA) and metabotropic glutamate receptors in nicotine reinforcement: potential pharmacotherapies for smoking cessation.

    PubMed

    Markou, Athina; Paterson, Neil E; Semenova, Svetlana

    2004-10-01

    Previous work indicated a role for GABA and glutamate in the reinforcing effects of drugs of abuse. The present studies assessed the effects of GABAergic and glutamatergic manipulations on the reinforcing effects of nicotine as assessed by intravenous nicotine self-administration. Male Wistar rats were allowed to self-administer either of two nicotine doses under a fixed ratio or a progressive ratio schedule of reinforcement. The effects of a glutamatergic compound on nicotine self-administration in male DBA/2J mice were also explored. Finally, to assess for nonspecific effects of the drug manipulations, the effects of all test compounds on responding maintained by a food reinforcer were investigated. The pharmacological manipulations used were: gamma-vinyl-GABA (vigabatrin or GVG), an irreversible inhibitor of GABA transaminase, the GABAB receptor agonists (-)baclofen and CGP44532, and the metabotropic glutamate receptor 5 (mGluR5) antagonist MPEP. GVG, CGP44532, and (-)baclofen dose-dependently decreased nicotine self-administration on the fixed-ratio schedule, but also decreased food-maintained responding. Furthermore, CGP44532 decreased breakpoints for nicotine and food at identical doses under the progressive-ratio schedule. MPEP dose-dependently decreased nicotine self-administration with no effect on food-maintained responding in rats. MPEP also decreased nicotine self-administration in the mice. These results demonstrate that activation of GABAB receptors or blockade of mGluR5 decreased nicotine self-administration. Although there was some selectivity for the effects of the GABAergic manipulations, there was clear selectivity of the effects of MPEP on nicotine- versus food-maintained responding. Thus, compounds that increase GABAergic neurotransmission and antagonists at mGluR5 have potential as anti-smoking medications for humans.

  16. Activation of A-type gamma-aminobutyric acid receptors excites gonadotropin-releasing hormone neurons.

    PubMed

    DeFazio, R Anthony; Heger, Sabine; Ojeda, Sergio R; Moenter, Suzanne M

    2002-12-01

    Gamma-aminobutyric acid (GABA), acting through GABA(A) receptors (GABA(A)R), is hypothesized to suppress reproduction by inhibiting GnRH secretion, but GABA actions directly on GnRH neurons are not well established. In green fluorescent protein-identified adult mouse GnRH neurons in brain slices, gramicidin-perforated-patch-clamp experiments revealed the reversal potential (E(GABA)) for current through GABA(A)Rs was depolarized relative to the resting potential. Furthermore, rapid GABA application elicited action potentials in GnRH neurons but not controls. The consequence of GABA(A)R activation depends on intracellular chloride levels, which are maintained by homeostatic mechanisms. Membrane proteins that typically extrude chloride (KCC-2 cotransporter, CLC-2 channel) were absent from the GT1-7 immortalized GnRH cell line and GnRH neurons in situ or were not localized to the proper cell compartment for function. In contrast, GT1-7 cells and some GnRH neurons expressed the chloride-accumulating cotransporter, NKCC-1. Patch-clamp experiments showed that blockade of NKCC hyperpolarized E(GABA) by lowering intracellular chloride. Regardless of reproductive state, rapid GABA application excited GnRH neurons. In contrast, bath application of the GABA(A)R agonist muscimol transiently increased then suppressed firing; suppression persisted 4-15 min. Rapid activation of GABA(A)R thus excites GnRH neurons whereas prolonged activation reduces excitability, suggesting the physiological consequence of synaptic activation of GABA(A)R in GnRH neurons is excitation.

  17. Muscimol as an ionotropic GABA receptor agonist.

    PubMed

    Johnston, Graham A R

    2014-10-01

    Muscimol, a psychoactive isoxazole from Amanita muscaria and related mushrooms, has proved to be a remarkably selective agonist at ionotropic receptors for the inhibitory neurotransmitter GABA. This historic overview highlights the discovery and development of muscimol and related compounds as a GABA agonist by Danish and Australian neurochemists. Muscimol is widely used as a ligand to probe GABA receptors and was the lead compound in the development of a range of GABAergic agents including nipecotic acid, tiagabine, 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol, (Gaboxadol(®)) and 4-PIOL.

  18. Ionotropic GABA Receptors and Distal Retinal ON and OFF Responses

    PubMed Central

    Popova, E.

    2014-01-01

    In the vertebrate retina, visual signals are segregated into parallel ON and OFF pathways, which provide information for light increments and decrements. The segregation is first evident at the level of the ON and OFF bipolar cells in distal retina. The activity of large populations of ON and OFF bipolar cells is reflected in the b- and d-waves of the diffuse electroretinogram (ERG). The role of gamma-aminobutyric acid (GABA), acting through ionotropic GABA receptors in shaping the ON and OFF responses in distal retina, is a matter of debate. This review summarized current knowledge about the types of the GABAergic neurons and ionotropic GABA receptors in the retina as well as the effects of GABA and specific GABAA and GABAC receptor antagonists on the activity of the ON and OFF bipolar cells in both nonmammalian and mammalian retina. Special emphasis is put on the effects on b- and d-waves of the ERG as a useful tool for assessment of the overall function of distal retinal ON and OFF channels. The role of GABAergic system in establishing the ON-OFF asymmetry concerning the time course and absolute and relative sensitivity of the ERG responses under different conditions of light adaptation in amphibian retina is also discussed. PMID:25143858

  19. Inorganic Nitrate Mimics Exercise-Stimulated Muscular Fiber-Type Switching and Myokine and γ-Aminobutyric Acid Release.

    PubMed

    Roberts, Lee D; Ashmore, Tom; McNally, Ben D; Murfitt, Steven A; Fernandez, Bernadette O; Feelisch, Martin; Lindsay, Ross; Siervo, Mario; Williams, Elizabeth A; Murray, Andrew J; Griffin, Julian L

    2017-03-01

    Exercise is an effective intervention for the prevention and treatment of type 2 diabetes. Skeletal muscle combines multiple signals that contribute to the beneficial effects of exercise on cardiometabolic health. Inorganic nitrate increases exercise efficiency, tolerance, and performance. The transcriptional regulator peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) coordinates the exercise-stimulated skeletal muscle fiber-type switch from glycolytic fast-twitch (type IIb) to oxidative slow-twitch (type I) and intermediate (type IIa) fibers, an effect reversed in insulin resistance and diabetes. We found that nitrate induces PGC1α expression and a switch toward type I and IIa fibers in rat muscle and myotubes in vitro. Nitrate induces the release of exercise/PGC1α-dependent myokine FNDC5/irisin and β-aminoisobutyric acid from myotubes and muscle in rats and humans. Both exercise and nitrate stimulated PGC1α-mediated γ-aminobutyric acid (GABA) secretion from muscle. Circulating GABA concentrations were increased in exercising mice and nitrate-treated rats and humans; thus, GABA may function as an exercise/PGC1α-mediated myokine-like small molecule. Moreover, nitrate increased circulating growth hormone levels in humans and rodents. Nitrate induces physiological responses that mimic exercise training and may underlie the beneficial effects of this metabolite on exercise and cardiometabolic health.

  20. Library screening by means of mass spectrometry (MS) binding assays-exemplarily demonstrated for a pseudostatic library addressing γ-aminobutyric acid (GABA) transporter 1 (GAT1).

    PubMed

    Sindelar, Miriam; Wanner, Klaus T

    2012-09-01

    In the present study, the application of mass spectrometry (MS) binding assays as a tool for library screening is reported. For library generation, dynamic combinatorial chemistry (DCC) was used. These libraries can be screened by means of MS binding assays when appropriate measures are taken to render the libraries pseudostatic. That way, the efficiency of MS binding assays to determine ligand binding in compound screening with the ease of library generation by DCC is combined. The feasibility of this approach is shown for γ-aminobutyric acid (GABA) transporter 1 (GAT1) as a target, representing the most important subtype of the GABA transporters. For the screening, hydrazone libraries were employed that were generated in the presence of the target by reacting various sets of aldehydes with a hydrazine derivative that is delineated from piperidine-3-carboxylic acid (nipecotic acid), a common fragment of known GAT1 inhibitors. To ensure that the library generated is pseudostatic, a large excess of the nipecotic acid derivative is employed. As the library is generated in a buffer system suitable for binding and the target is already present, the mixtures can be directly analyzed by MS binding assays-the process of library generation and screening thus becoming simple to perform. The binding affinities of the hits identified by deconvolution were confirmed in conventional competitive MS binding assays performed with single compounds obtained by separate synthesis. In this way, two nipecotic acid derivatives exhibiting a biaryl moiety, 1-{2-[2'-(1,1'-biphenyl-2-ylmethylidene)hydrazine]ethyl}piperidine-3-carboxylic acid and 1-(2-{2'-[1-(2-thiophenylphenyl)methylidene]hydrazine}ethyl)piperidine-3-carboxylic acid, were found to be potent GAT1 ligands exhibiting pK(i) values of 6.186 ± 0.028 and 6.229 ± 0.039, respectively. This method enables screening of libraries, whether generated by conventional chemistry or DCC, and is applicable to all kinds of targets including

  1. How and why does tomato accumulate a large amount of GABA in the fruit?

    PubMed Central

    Takayama, Mariko; Ezura, Hiroshi

    2015-01-01

    Gamma-aminobutyric acid (GABA) has received much attention as a health-promoting functional compound, and several GABA-enriched foods have been commercialized. In higher plants, GABA is primarily metabolized via a short pathway called the GABA shunt. The GABA shunt bypasses two steps (the oxidation of α-ketoglutarate to succinate) of the tricarboxylic acid (TCA) cycle via reactions catalyzed by three enzymes: glutamate decarboxylase, GABA transaminase, and succinic semialdehyde dehydrogenase. The GABA shunt plays a major role in primary carbon and nitrogen metabolism and is an integral part of the TCA cycle under stress and non-stress conditions. Tomato is one of the major crops that accumulate a relatively high level of GABA in its fruits. The GABA levels in tomato fruits dramatically change during fruit development; the GABA levels increase from flowering to the mature green stage and then rapidly decrease during the ripening stage. Although GABA constitutes up to 50% of the free amino acids at the mature green stage, the molecular mechanism of GABA accumulation and the physiological function of GABA during tomato fruit development remain unclear. In this review, we summarize recent studies of GABA accumulation in tomato fruits and discuss the potential biological roles of GABA in tomato fruit development. PMID:26322056

  2. Design and Mechanism of Tetrahydrothiophene-based GABA Aminotransferase Inactivators

    PubMed Central

    Le, Hoang V.; Hawker, Dustin D.; Wu, Rui; Doud, Emma; Widom, Julia; Sanishvili, Ruslan; Liu, Dali; Kelleher, Neil L.; Silverman, Richard B.

    2015-01-01

    Low levels of γ-aminobutyric acid (GABA), one of two major neurotransmitters that regulate brain neuronal activity, are associated with many neurological disorders, such as epilepsy, Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, and cocaine addiction. One of the main methods to raise the GABA level in human brain is to use small molecules that cross the blood-brain barrier and inhibit the activity of γ-aminobutyric acid aminotransferase (GABA-AT), the enzyme that degrades GABA. We have designed a series of conformationally-restricted, tetrahydrothiophene-based GABA analogs with a properly-positioned leaving group that could facilitate a ring-opening mechanism, leading to inactivation of GABA-AT. One compound in the series is eight times more efficient an inactivator of GABA-AT than vigabatrin, the only FDA-approved inactivator of GABA-AT. Our mechanistic studies show that the compound inactivates GABA-AT by a new mechanism. The metabolite resulting from inactivation does not covalently bind to amino acid residues of GABA-AT but stays in the active site via H-bond interactions with Arg-192, a π-π interaction with Phe-189, and a weak nonbonded S···O=C interaction with Glu-270, thereby inactivating the enzyme. PMID:25781189

  3. GABA and glycine actions on spinal motoneurons.

    PubMed

    Krnjević, K; Puil, E; Werman, R

    1977-06-01

    Applied microiontophoretically in the spinal cord of cats, glycine is consistently more powerful than gamma-aminobutyric acid (GABA) in raising the membrane conductance of lumbosacral motoneurons (mean ratio of equipotent iontophoretic currents tested on same cells is 5.6:1). This is the reverse of the situation in cerebral cortex. The effect of glycine is well maintained during applications lasting about 1 min, but that of GABA, after an early peak, drops to a much lower plateau (mean plateau-over-peak ratio is 0.23). The reversal potentials for the action of GABA and glycine are initially similar but they behave differently during a prolonged application; that for glycine usually remains constant or becomes more negative whereas that for GABA tends to shift in the positive direction. Various explanations of these phenomena are considered. It is suggested that a single process, electrogenic uptake of GABA, may account for both desensitization (by removing GABA from its site of action) and the positive shift in GABA reversal potential (became uptake is probably associated with an influx of Na+).

  4. Impact of exogenous GABA treatments on endogenous GABA metabolism in anthurium cut flowers in response to postharvest chilling temperature.

    PubMed

    Aghdam, Morteza Soleimani; Naderi, Roohangiz; Jannatizadeh, Abbasali; Babalar, Mesbah; Sarcheshmeh, Mohammad Ali Askari; Faradonbe, Mojtaba Zamani

    2016-09-01

    Anthurium flowers are susceptible to chilling injury, and the optimum storage temperature is 12.5-20 °C. The γ-aminobutyric acid (GABA) shunt pathway may alleviate chilling stress in horticultural commodities by providing energy (ATP), reducing molecules (NADH), and minimizing accumulation of reactive oxygen species (ROS). In this experiment, the impact of a preharvest spray treatment with 1 mM GABA and postharvest treatment of 5 mM GABA stem-end dipping on GABA shunt pathway activity of anthurium cut flowers (cv. Sirion) in response to cold storage (4 °C for 21 days) was investigated. GABA treatments resulted in lower glutamate decarboxylase (GAD) and higher GABA transaminase (GABA-T) activities in flowers during cold storage, which was associated with lower GABA content and coincided with higher ATP content. GABA treatments also enhanced accumulation of endogenous glycine betaine (GB) in flowers during cold storage, as well as higher spathe relative water content (RWC). These findings suggest that GABA treatments may alleviate chilling injury of anthurium cut flowers by enhancing GABA shunt pathway activity leading to provide sufficient ATP and promoting endogenous GB accumulation.

  5. Effects of prenatal exposure to 2,4-D/2,4,5-T mixture on postnatal changes in rat brain glutamate, GABA protein, and nucleic acid levels

    SciTech Connect

    Mohammad, F.K.; Omer, V.E.V.

    1988-02-01

    The opportunity of maternal exposure to various chemicals in the work place and the general environments have increased, and the fetus and neonate may be at greater risk than the adult. However, the embryotoxic and teratogenic effects of the chlorinated phenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), the main chemicals in Agent Orange, are well documented only in laboratory animals. The brain of the developing fetus is vulnerable to the toxic effects of the phenoxy herbicides which readily cross the placental barrier and distribute into fetal tissues, including brain. Although the neurochemical basis for the behavioral teratogenicity of the phenoxy herbicides is not know, it was recently reported that non-teratogenic doses of a 1:1 mixture of 2,4-D and 2,4,5-T delayed the ontogeny of dopamine and serotonin in the brain of the developing rate. This communication provides further descriptive information about the ontogeny of rat brain nucleic acid, protein, glutamate and ..gamma..-aminobutyrate (GABA) following in utero exposure to non-teratogenic levels of a 1:1 mixture of 2,4-D/2,4,5-T.

  6. Putative TRP channel antagonists, SKF 96365, flufenamic acid and 2-APB, are non-competitive antagonists at recombinant human α1β2γ2 GABA(A) receptors.

    PubMed

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

    2012-05-01

    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 α1β2γ2 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 μM) and FF (1-100 μM) significantly inhibited GABA responses of recombinant human α1β2γ2 GABA(A) receptor stably expressed in HEK293 cells with IC(50) values of 13.4 ± 5.1 and 1.9 ± 1.4 μM, 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 μM) also inhibited responses to GABA at all concentrations used with an IC(50) value of 16.7 ± 5.4 μM (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.

  7. Novel GABA receptor pesticide targets.

    PubMed

    Casida, John E; Durkin, Kathleen A

    2015-06-01

    The γ-aminobutyric acid (GABA) receptor has four distinct but overlapping and coupled targets of pesticide action importantly associated with little or no cross-resistance. The target sites are differentiated by binding assays with specific radioligands, resistant strains, site-directed mutagenesis and molecular modeling. Three of the targets are for non-competitive antagonists (NCAs) or channel blockers of widely varied chemotypes. The target of the first generation (20th century) NCAs differs between the larger or elongated compounds (NCA-IA) including many important insecticides of the past (cyclodienes and polychlorocycloalkanes) or present (fiproles) and the smaller or compact compounds (NCA-IB) highly toxic to mammals and known as cage convulsants, rodenticides or chemical threat agents. The target of greatest current interest is designated NCA-II for the second generation (21st century) of NCAs consisting for now of isoxazolines and meta-diamides. This new and uniquely different NCA-II site apparently differs enough between insects and mammals to confer selective toxicity. The fourth target is the avermectin site (AVE) for allosteric modulators of the chloride channel. NCA pesticides vary in molecular surface area and solvent accessible volume relative to avermectin with NCA-IBs at 20-22%, NCA-IAs at 40-45% and NCA-IIs at 57-60%. The same type of relationship relative to ligand-docked length is 27-43% for NCA-IBs, 63-71% for NCA-IAs and 85-105% for NCA-IIs. The four targets are compared by molecular modeling for the Drosophila melanogaster GABA-R. The principal sites of interaction are proposed to be: pore V1' and A2' for NCA-IB compounds; pore A2', L6' and T9' for NCA-IA compounds; pore T9' to S15' in proximity to M1/M3 subunit interface (or alternatively an interstitial site) for NCA-II compounds; and M1/M3, M2 interfaces for AVE. Understanding the relationships of these four binding sites is important in resistance management and in the discovery and use

  8. Pharmacologically novel GABA receptor in human dorsal root ganglion neurons.

    PubMed

    Valeyev, A Y; Hackman, J C; Wood, P M; Davidoff, R A

    1996-11-01

    1. Whole cell voltage-clamp studies of gamma-aminobutyric acid (GABA) receptors were performed on large (> 80 microns) cultured human dorsal root ganglion (DRG) neurons. 2. GABA and pentobarbital sodium when applied in micromolar concentrations evoked inward Cl- currents in DRG neurons voltage clamped at negative membrane potentials. 3. Diazepam (10 microM) and pentobarbital (10 microM) upmodulated the GABA current by approximately 149 and 168%, respectively. 4. The GABA currents in human DRG cells were unaffected by the classical GABA antagonists picrotoxin and bicuclline (100 microM). In contrast, the GABA responses evoked in adult rat DRG cells cultured in an identical manner were inhibited by both antagonists. The glycine receptor antagonist strychnine (100 microM) did not alter GABA currents in human DRG cells. 5. Human DRG cells did not respond to glycine (10-100 microM) or taurine (10-100 microM). The GABAB agonist baclofen had no effect on the holding current when patch pipettes were filled with 130 mM KCl. The GABAB antagonists saclofen applied either alone or with GABA was without effect. 6. The differences between the GABA receptors described here and GABA receptors in other species may reflect the presence of receptor subunits unique to human DRG cells.

  9. GABA and GABA receptors alterations in the primary visual cortex of concave lens-induced myopic model.

    PubMed

    Zhao, Wen; Bi, Ai-Ling; Xu, Chao-Li; Ye, Xiang; Chen, Mei-Qing; Wang, Xin-Ting; Zhang, Xiao-Yan; Guo, Jun-Guo; Jiang, Wen-Jun; Zhang, Jin; Bi, Hong-Sheng

    2017-02-02

    Until recently most researches on myopia mechanisms have mainly been focused on the eye ball and few investigations were explored on the upper visual pathway, such as the visual cortex. The roles of gamma-aminobutyric acid (GABA) in the retinal and in the upper visual pathway are inter-correlated. As the retinal glutamate decarboxylase (GAD), GABA, and the mRNA levels of GABA receptors increased during the concave lens induced myopia formation, however, whether GABA alterations also occurred in the visual cortex during the concave lens induction is still unknown. In the present study, using HPLC, Enzyme-Linked Immunosorbent Assay (ELISA) and Real-Time Quantitative-PCR (RT-PCR) methods, we observed the changing trends of GABA, glutamate decarboxylase (GAD), and GABA receptors in the visual cortex of concave lens-induced myopic guinea pigs. Similar to the changing patterns of retinal GABA, the concentrations of GAD, GABA and the mRNA levels of GABA receptors in the visual cortex also increased. These results indicate that the exploration on myopia mechanisms should possibly be investigated on the whole visual pathway and the detailed significance of cortical GABA alterations needs further investigation.

  10. Treatment of Huntington disease with gamma-acetylenic GABA an irreversible inhibitor of GABA-transaminase: increased CSF GABA and homocarnosine without clinical amelioration.

    PubMed

    Tell, G; Böhlen, P; Schechter, P J; Koch-Weser, J; Agid, Y; Bonnet, A M; Coquillat, G; Chazot, G; Fischer, C

    1981-02-01

    gamma-Acetylenic GABA (GAG, RMI 71.645), a potent irreversible inhibitor of gamma-aminobutyric acid transaminase, was given orally in various dosage schedules to 14 patients with Huntington disease. The biochemical effects of the drug on cerebrospinal fluid (CSF) concentrations of gamma-aminobutyric acid (GABA) and the GABA-containing dipeptide, homocarnosine, were measured in 10 of 14 patients. Treatment with GAG increased CSF concentrations of GABA and homocarnosine as compared to pretreatment values, suggesting that the drug increased brain GABA concentration. Despite this neurochemical effect, the clinical state was not improved. Except for single seizure episodes in five patients, GAG therapy was well tolerated. These results do not exclude the possibility that agents that augment CNS GABAergic function may prove useful in therapy of Huntington disease.

  11. Attenuation of malonate toxicity in primary mesencephalic cultures using the GABA transport blocker, NO-711.

    PubMed

    Stokes, A H; Bernard, L P; Nicklas, W J; Zeevalk, G D

    2001-04-01

    Cultured rat mesencephalic neurons were used to assess the effects of gamma-aminobutyric acid (GABA) transport blockers on toxicity caused by malonate, a reversible, competitive inhibitor of succinate dehydrogenase. Previous studies utilizing an ex vivo chick retinal preparation have shown that GABA release and cell swelling are early consequences of acute energy impairment and that GABA transport blockers attenuate this toxicity. The present results demonstrate that the nonsubstrate GABA transport blocker, NO-711 (1 nM-1 microM), dose-dependently protected cultured mesencephalic dopamine (DA) and GABA neurons from malonate-induced toxicity. Similar protection was demonstrated with nipecotic acid (1 mM) and SKF89976A (100 nM), substrate and nonsubstrate GABA transport blockers, respectively. These compounds by themselves produced no signs of toxicity, although nipecotic acid caused a long-term decrease in GABA uptake not associated with toxicity. Compounds which decrease intracellular reactive oxygen species (ROS) are protective in this model, but NO-711 did not prevent the rise in intracellular ROS induced by malonate, indicating its protective effects were downstream of ROS production. Supplementation of malonate treated cultures with the GABA(A) agonist, muscimol (10 microM), increased the toxicity toward the DA and GABA neuron populations. Antagonists at the GABA(A) and glycine receptors provided partial protection to both the GABA and DA neurons. These findings suggest that the GABA transporter, GABA(A), and/or glycine channels contribute to cell damage associated with energy impairment in this model.

  12. Lack of functional GABA(B) receptors alters GnRH physiology and sexual dimorphic expression of GnRH and GAD-67 in the brain.

    PubMed

    Catalano, Paolo N; Di Giorgio, Noelia; Bonaventura, María M; Bettler, Bernhard; Libertun, Carlos; Lux-Lantos, Victoria A

    2010-03-01

    GABA, the main inhibitory neurotransmitter, acts through GABA(A/C) and GABA(B) receptors (GABA(B)Rs); it is critical for gonadotropin regulation. We studied whether the lack of functional GABA(B)Rs in GABA(B1) knockout (GABA(B1)KO) mice affected the gonadotropin axis physiology. Adult male and female GABA(B1)KO and wild-type (WT) mice were killed to collect blood and tissue samples. Gonadotropin-releasing hormone (GnRH) content in whole hypothalami (HT), olfactory bulbs (OB), and frontoparietal cortexes (CT) were determined (RIA). GnRH expression by quantitative real-time PCR (qRT-PCR) was evaluated in preoptic area-anterior hypothalamus (POA-AH), medial basal-posterior hypothalamus (MBH-PH), OB, and CT. Pulsatile GnRH secretion from hypothalamic explants was measured by RIA. GABA, glutamate, and taurine contents in HT and CT were determined by HPLC. Glutamic acid decarboxylase-67 (GAD-67) mRNA was measured by qRT-PCR in POA-AH, MBH-PH, and CT. Gonadotropin content, serum levels, and secretion from adenohypophyseal cell cultures (ACC) were measured by RIA. GnRH mRNA expression was increased in POA-AH of WT males compared with females; this pattern of expression was inversed in GABA(B1)KO mice. MBH-PH, OB, and CT did not follow this pattern. In GABA(B1)KO females, GnRH pulse frequency was increased and GABA and glutamate contents were augmented. POA-AH GAD-67 mRNA showed the same expression pattern as GnRH mRNA in this area. Gonadotropin pituitary contents and serum levels showed no differences between genotypes. Increased basal LH secretion and decreased GnRH-stimulated gonadotropin response were observed in GABA(B1)KO female ACCs. These results support the hypothesis that the absence of functional GABA(B)Rs alters GnRH physiology and critically affects sexual dimorphic expression of GnRH and GAD-67 in POA-AH.

  13. Immunocytochemical localization of the GABA transporter in rat brain.

    PubMed

    Radian, R; Ottersen, O P; Storm-Mathisen, J; Castel, M; Kanner, B I

    1990-04-01

    Polyclonal antibodies were raised against the GABA transporter (GABA-Tp) purified from rat brain tissue (Radian et al., 1986) and used for immunocytochemical localization of the antigen in several rat brain areas, including the cerebellum, hippocampus, substantia nigra, and cerebral cortex. Light microscopic studies with the peroxidase-antiperoxidase and biotin-avidin-peroxidase techniques suggested that GABA-Tp is localized in the same types of axons and terminals that contain endogenous GABA, as judged by comparison with parallel sections incubated with antibodies against glutaraldehyde-conjugated GABA. However, as expected from biochemical results, different neurons differed in their relative contents of GABA-Tp and GABA; thus, GABA-Tp was relatively low in striatonigral and Purkinje axon terminals and relatively high in nerve plexus around the bases of cerebellar Purkinje cells and hippocampal pyramidal and granule cells. The GABA-Tp antiserum did not produce detectable labeling of nerve cell bodies. Electron microscopic studies supported the light microscopic observations and provided direct evidence of cellular co-localization of GABA-Tp and GABA (as visualized by the peroxidase-antiperoxidase technique and postembedding immunogold labeling, respectively). The ultrastructural studies indicated the presence of GABA-Tp also in glial processes but not in glial cell bodies. The relative intensity of the neuronal and glial staining varied among regions: glial staining predominated over neuronal staining in the substantia nigra, whereas the converse was true in the cerebellum and hippocampus. The present immunocytochemical data demonstrate directly what has previously been inferred from biochemical and autoradiographic evidence: that the mechanisms for high-affinity GABA uptake is selectively and differentially localized in GABAergic neurons and in glial cells.

  14. Anion transport and GABA signaling

    PubMed Central

    Hübner, Christian A.; Holthoff, Knut

    2013-01-01

    Whereas activation of GABAA receptors by GABA usually results in a hyperpolarizing influx of chloride into the neuron, the reversed chloride driving force in the immature nervous system results in a depolarizing efflux of chloride. This GABAergic depolarization is deemed to be important for the maturation of the neuronal network. The concept of a developmental GABA switch has mainly been derived from in vitro experiments and reliable in vivo evidence is still missing. As GABAA receptors are permeable for both chloride and bicarbonate, the net effect of GABA also critically depends on the distribution of bicarbonate. Whereas chloride can either mediate depolarizing or hyperpolarizing currents, bicarbonate invariably mediates a depolarizing current under physiological conditions. Intracellular bicarbonate is quickly replenished by cytosolic carbonic anhydrases. Intracellular bicarbonate levels also depend on different bicarbonate transporters expressed by neurons. The expression of these proteins is not only developmentally regulated but also differs between cell types and even subcellular regions. In this review we will summarize current knowledge about the role of some of these transporters for brain development and brain function. PMID:24187533

  15. GABA signalling modulates plant growth by directly regulating the activity of plant-specific anion transporters.

    PubMed

    Ramesh, Sunita A; Tyerman, Stephen D; Xu, Bo; Bose, Jayakumar; Kaur, Satwinder; Conn, Vanessa; Domingos, Patricia; Ullah, Sana; Wege, Stefanie; Shabala, Sergey; Feijó, José A; Ryan, Peter R; Gilliham, Matthew; Gillham, Matthew

    2015-07-29

    The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.

  16. Type 2 Diabetes and Uric Acid Nephrolithiasis

    NASA Astrophysics Data System (ADS)

    Maalouf, Naim M.

    2008-09-01

    Type 2 diabetes is associated with an increased propensity for uric acid nephrolithiasis. In individuals with diabetes, this increased risk is due to a lower urine pH that results from obesity, dietary factors, and impaired renal ammoniagenesis. The epidemiology and pathogenesis of uric acid stone disease in patients with diabetes are hereby reviewed, and potential molecular mechanisms are proposed.

  17. The regulation of alpha-MSH release by GABA is mediated by a chloride-dependent [Ca2+]c increase in frog melanotrope cells.

    PubMed

    Desrues, Laurence; Castel, Hélène; Malagon, Maria M; Vaudry, Hubert; Tonon, Marie-Christine

    2005-10-01

    In frog melanotrope cells, gamma-aminobutyric acid (GABA) induces a biphasic effect, i.e. a transient stimulation followed by a more sustained inhibition of alpha-MSH release, and both phases of the GABA effect are mediated by GABAA receptors. We have previously shown that the stimulatory phase evoked by GABAA receptor agonists can be accounted for by calcium entry. In the present study, we have investigated the involvement of the chloride flux on GABA-induced [Ca2+]c increase and alpha-MSH release. We show that GABA evokes a concentration-dependent [Ca2+]c rise through specific activation of the GABAA receptor. The GABA-induced [Ca2+]c increase results from opening of voltage-activated L- and N-type calcium channels, and sodium channels. Variations of the extracellular Cl- concentration revealed that GABA-induced [Ca2+]c rise and alpha-MSH release both depend on the Cl- flux direction and driving force. These observations suggest for the first time that GABA-gated Cl- efflux provokes an increase in [Ca2+]c increase that is responsible for hormone secretion.

  18. Distribution of 3H-GABA uptake sites in the nematode Ascaris

    SciTech Connect

    Guastella, J.; Stretton, A.O. )

    1991-05-22

    The distribution of uptake sites for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the nematode Ascaris suum was examined by autoradiography of 3H-GABA uptake. Single neural processes in both the ventral and dorsal nerve cords were labeled with 3H-GABA. Serial section analysis identified the cells of origin of these processes as the RMEV-like and RMED-like neurons. These cells belong to a set of four neurons in the nerve ring, all of which are labeled by 3H-GABA. 3H-GABA labeling of at least two other sets of cephalic neurons was seen. One of these pairs consists of medium-sized lateral ganglia neurons, located at the level of the amphid commissure bundle. A second pair is located in the lateral ganglia at the level of the deirid commissure bundle. The position and size of these lateral ganglia cells suggest that they are the GABA-immunoreactive lateral ganglia cells frequently seen in whole-mount immunocytochemical preparations. Four neuronal cell bodies located in the retrovesicular ganglion were also labeled with 3H-GABA. These cells, which are probably cholinergic excitatory motor neurons, do not contain detectable GABA-like immunoreactivity. Heavy labeling of muscle cells was also observed. The ventral and dorsal nerve cord inhibitory motor neurons, which are known to contain GABA-like immunoreactivity, were not labeled above background with 3H-GABA. Together with the experiments reported previously, these results define three classes of GABA-associated neurons in Ascaris: (1) neurons that contain endogenous GABA and possess a GABA uptake system; (2) neurons that contain endogenous GABA, but that either lack a GABA uptake system or possess a GABA uptake system of low activity; (3) neurons that possess a GABA uptake system, but that lack endogenous GABA.

  19. Cloning and expression of a rat brain GABA transporter

    SciTech Connect

    Guastella, J.; Czyzyk, L.; Davidson, N.; Lester, H.A. ); Nelson, N.; Nelson, H.; Miedel, M.C. ); Keynan, S.; Kanner, B.I. )

    1990-09-14

    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 ({sup 3}H)GABA to levels above control values. The transporter encoded by GAT-1 has a high affinity for GABA, is sodium- and chloride-dependent, and is pharmacologically similar to neuronal GABA transporters. The GAT-1 protein shares antigenic determinants with a native rat brain GABA transporter. The nucleotide sequence of GAT-1 predicts a protein of 599 amino acids with a molecular weight of 67 kilodaltons. Hydropathy analysis of the deduced protein suggests multiple transmembrane regions, a feature shared by several cloned transporters; however, database searches indicate that GAT-1 is not homologous to any previously identified proteins. Therefore, GAT-1 appears to be a member of a previously uncharacterized family of transport molecules.

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

    PubMed

    Linets'ka, M V; Storchak, L H; Himmelreĭch, N H

    2002-01-01

    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

  1. Catabolism of GABA, succinic semialdehyde or gamma-hydroxybutyrate through the GABA shunt impair mitochondrial substrate-level phosphorylation.

    PubMed

    Ravasz, Dora; Kacso, Gergely; Fodor, Viktoria; Horvath, Kata; Adam-Vizi, Vera; Chinopoulos, Christos

    2017-03-11

    GABA is catabolized in the mitochondrial matrix through the GABA shunt, encompassing transamination to succinic semialdehyde followed by oxidation to succinate by the concerted actions of GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH), respectively. Gamma-hydroxybutyrate (GHB) is a neurotransmitter and a psychoactive drug that could enter the citric acid cycle through transhydrogenation with α-ketoglutarate to succinic semialdehyde and d-hydroxyglutarate, a reaction catalyzed by hydroxyacid-oxoacid transhydrogenase (HOT). Here, we tested the hypothesis that the elevation in matrix succinate concentration caused by exogenous addition of GABA, succinic semialdehyde or GHB shifts the equilibrium of the reversible reaction catalyzed by succinate-CoA ligase towards ATP (or GTP) hydrolysis, effectively negating substrate-level phosphorylation (SLP). Mitochondrial SLP was addressed by interrogating the directionality of the adenine nucleotide translocase during anoxia in isolated mouse brain and liver mitochondria. GABA eliminated SLP, and this was rescued by the GABA-T inhibitors vigabatrin and aminooxyacetic acid. Succinic semialdehyde was an extremely efficient substrate energizing mitochondria during normoxia but mimicked GABA in abolishing SLP in anoxia, in a manner refractory to vigabatrin and aminooxyacetic acid. GHB could moderately energize liver but not brain mitochondria consistent with the scarcity of HOT expression in the latter. In line with these results, GHB abolished SLP in liver but not brain mitochondria during anoxia and this was unaffected by either vigabatrin or aminooxyacetic acid. It is concluded that when mitochondria catabolize GABA or succinic semialdehyde or GHB through the GABA shunt, their ability to perform SLP is impaired.

  2. Investigating GABA and its function in platelets as compared to neurons.

    PubMed

    Kaneez, Fatima Shad; Saeed, Sheikh Arshad

    2009-08-01

    We have recently suggested that platelets could be used as a model for neuronal receptors. In this paper we have investigated gamma-aminobutyric acid (GABA) metabolism and GABA receptors in platelets and in cultured neurons to see whether platelets' GABA mimics neuronal GABA receptor activities. We used the ELISA technique for detecting the GABA concentration in platelet rich plasma and cultured neurons. The functional effects of GABA and its receptor ligands on platelets were determined using an aggregometer. We found that the GABA concentration is 30% lower in platelets than in neurons and in both preparations GABA was metabolized by GABA transaminase (GABA-T). GABA potentiated calcium dependent platelet aggregation with a higher value in washed platelets suspension (WPS) then in platelet rich plasma (PRP). This effect was inhibited by benzodiazepines, calcium channel blockers and the selective phosphoinositide 3-kinase antagonist Wortmannin. GABA neurotransmission is involved in most aspects of normal brain function and can be perturbed in many neuropathologic conditions. We concluded that platelets could be further developed to be used as a peripheral model to study neuronal GABAergic function and its abnormality in diseases such as epilepsy and schizophrenia. Furthermore our results indicated that PI3-kinase is involved in calcium dependent GABA induced platelet aggregation as this synergistic effect is inhibited by Wortmannin in dose dependent manner.

  3. Agonist pharmacology of two Drosophila GABA receptor splice variants.

    PubMed Central

    Hosie, A. M.; Sattelle, D. B.

    1996-01-01

    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

  4. Neurotoxins from Snake Venoms and α-Conotoxin ImI Inhibit Functionally Active Ionotropic γ-Aminobutyric Acid (GABA) Receptors*

    PubMed Central

    Kudryavtsev, Denis S.; Shelukhina, Irina V.; Son, Lina V.; Ojomoko, Lucy O.; Kryukova, Elena V.; Lyukmanova, Ekaterina N.; Zhmak, Maxim N.; Dolgikh, Dmitry A.; Ivanov, Igor A.; Kasheverov, Igor E.; Starkov, Vladislav G.; Ramerstorfer, Joachim; Sieghart, Werner; Tsetlin, Victor I.; Utkin, Yuri N.

    2015-01-01

    Ionotropic receptors of γ-aminobutyric acid (GABAAR) regulate neuronal inhibition and are targeted by benzodiazepines and general anesthetics. We show that a fluorescent derivative of α-cobratoxin (α-Ctx), belonging to the family of three-finger toxins from snake venoms, specifically stained the α1β3γ2 receptor; and at 10 μm α-Ctx completely blocked GABA-induced currents in this receptor expressed in Xenopus oocytes (IC50 = 236 nm) and less potently inhibited α1β2γ2 ≈ α2β2γ2 > α5β2γ2 > α2β3γ2 and α1β3δ GABAARs. The α1β3γ2 receptor was also inhibited by some other three-finger toxins, long α-neurotoxin Ls III and nonconventional toxin WTX. α-Conotoxin ImI displayed inhibitory activity as well. Electrophysiology experiments showed mixed competitive and noncompetitive α-Ctx action. Fluorescent α-Ctx, however, could be displaced by muscimol indicating that most of the α-Ctx-binding sites overlap with the orthosteric sites at the β/α subunit interface. Modeling and molecular dynamic studies indicated that α-Ctx or α-bungarotoxin seem to interact with GABAAR in a way similar to their interaction with the acetylcholine-binding protein or the ligand-binding domain of nicotinic receptors. This was supported by mutagenesis studies and experiments with α-conotoxin ImI and a chimeric Naja oxiana α-neurotoxin indicating that the major role in α-Ctx binding to GABAAR is played by the tip of its central loop II accommodating under loop C of the receptors. PMID:26221036

  5. Glutamate and GABA in Appetite Regulation

    PubMed Central

    Delgado, Teresa C.

    2013-01-01

    Appetite is regulated by a coordinated interplay between gut, adipose tissue, and brain. A primary site for the regulation of appetite is the hypothalamus where interaction between orexigenic neurons, expressing Neuropeptide Y/Agouti-related protein, and anorexigenic neurons, expressing Pro-opiomelanocortin cocaine/Amphetamine-related transcript, controls energy homeostasis. Within the hypothalamus, several peripheral signals have been shown to modulate the activity of these neurons, including the orexigenic peptide ghrelin and the anorexigenic hormones insulin and leptin. In addition to the accumulated knowledge on neuropeptide signaling, presence and function of amino acid neurotransmitters in key hypothalamic neurons brought a new light into appetite regulation. Therefore, the principal aim of this review will be to describe the current knowledge of the role of amino acid neurotransmitters in the mechanism of neuronal activation during appetite regulation and the associated neuronal-astrocytic metabolic coupling mechanisms. Glutamate and GABA dominate synaptic transmission in the hypothalamus and administration of their receptors agonists into hypothalamic nuclei stimulates feeding. By using 13C High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy based analysis, the Cerdán group has shown that increased neuronal firing in mice hypothalamus, as triggered by appetite during the feeding-fasting paradigm, may stimulate the use of lactate as neuronal fuel leading to increased astrocytic glucose consumption and glycolysis. Moreover, fasted mice showed increased hypothalamic [2-13C]GABA content, which may be explained by the existence of GABAergic neurons in key appetite regulation hypothalamic nuclei. Interestingly, increased [2-13C]GABA concentration in the hypothalamus of fasted animals appears to result mainly from reduction in GABA metabolizing pathways, rather than increased GABA synthesis by augmented activity of the glutamate-glutamine-GABA

  6. Glutamate and GABA in Appetite Regulation.

    PubMed

    Delgado, Teresa C

    2013-01-01

    Appetite is regulated by a coordinated interplay between gut, adipose tissue, and brain. A primary site for the regulation of appetite is the hypothalamus where interaction between orexigenic neurons, expressing Neuropeptide Y/Agouti-related protein, and anorexigenic neurons, expressing Pro-opiomelanocortin cocaine/Amphetamine-related transcript, controls energy homeostasis. Within the hypothalamus, several peripheral signals have been shown to modulate the activity of these neurons, including the orexigenic peptide ghrelin and the anorexigenic hormones insulin and leptin. In addition to the accumulated knowledge on neuropeptide signaling, presence and function of amino acid neurotransmitters in key hypothalamic neurons brought a new light into appetite regulation. Therefore, the principal aim of this review will be to describe the current knowledge of the role of amino acid neurotransmitters in the mechanism of neuronal activation during appetite regulation and the associated neuronal-astrocytic metabolic coupling mechanisms. Glutamate and GABA dominate synaptic transmission in the hypothalamus and administration of their receptors agonists into hypothalamic nuclei stimulates feeding. By using (13)C High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy based analysis, the Cerdán group has shown that increased neuronal firing in mice hypothalamus, as triggered by appetite during the feeding-fasting paradigm, may stimulate the use of lactate as neuronal fuel leading to increased astrocytic glucose consumption and glycolysis. Moreover, fasted mice showed increased hypothalamic [2-(13)C]GABA content, which may be explained by the existence of GABAergic neurons in key appetite regulation hypothalamic nuclei. Interestingly, increased [2-(13)C]GABA concentration in the hypothalamus of fasted animals appears to result mainly from reduction in GABA metabolizing pathways, rather than increased GABA synthesis by augmented activity of the glutamate-glutamine-GABA

  7. Genetics Home Reference: congenital bile acid synthesis defect type 1

    MedlinePlus

    ... bile acid synthesis defect type 1 congenital bile acid synthesis defect type 1 Enable Javascript to view ... PDF Open All Close All Description Congenital bile acid synthesis defect type 1 is a disorder characterized ...

  8. Genetics Home Reference: congenital bile acid synthesis defect type 2

    MedlinePlus

    ... bile acid synthesis defect type 2 congenital bile acid synthesis defect type 2 Enable Javascript to view ... PDF Open All Close All Description Congenital bile acid synthesis defect type 2 is a disorder characterized ...

  9. Renal Denervation Improves the Baroreflex and GABA System in Chronic Kidney Disease-induced Hypertension

    PubMed Central

    Chen, Hsin-Hung; Cheng, Pei-Wen; Ho, Wen-Yu; Lu, Pei-Jung; Lai, Chi-Cheng; Tseng, Yang-Ming; Fang, Hua-Chang; Sun, Gwo-Ching; Hsiao, Michael; Liu, Chun-Peng; Tseng, Ching-Jiunn

    2016-01-01

    Hypertensive rats with chronic kidney disease (CKD) exhibit enhanced gamma-aminobutyric acid (GABA)B receptor function and regulation within the nucleus tractus solitarii (NTS). For CKD with hypertension, renal denervation (RD) interrupts the afferent renal sympathetic nerves, which are connecting to the NTS. The objective of the present study was to investigate how RD improves CKD-induced hypertension. Rats underwent 5/6 nephrectomy for 8 weeks, which induced CKD and hypertension. RD was induced by applying phenol to surround the renal artery in CKD. RD improved blood pressure (BP) by lowering sympathetic nerve activity and markedly restored the baroreflex response in CKD. The GABAB receptor expression was increased in the NTS of CKD; moreover, the central GABA levels were reduced in the cerebrospinal fluid, and the peripheral GABA levels were increased in the serum. RD restored the glutamic acid decarboxylase activity in the NTS in CKD, similar to the effect observed for central treatment with baclofen, and the systemic administration of gabapentin reduced BP. RD slightly improved renal function and cardiac load in CKD. RD may improve CKD-induced hypertension by modulating the baroreflex response, improving GABA system dysfunction and preventing the development and reducing the severity of cardiorenal syndrome type 4 in CKD rats. PMID:27917928

  10. GABA type B receptor signaling in proopiomelanocortin neurons protects against obesity, insulin resistance, and hypothalamic inflammation in male mice on a high-fat diet.

    PubMed

    Ito, Yoshihiro; Banno, Ryoichi; Shibata, Miyuki; Adachi, Koichi; Hagimoto, Shigeru; Hagiwara, Daisuke; Ozawa, Yoshiharu; Goto, Motomitsu; Suga, Hidetaka; Sugimura, Yoshihisa; Bettler, Bernhard; Oiso, Yutaka; Arima, Hiroshi

    2013-10-23

    There is evidence suggesting that the GABA system in the arcuate nucleus, where orexigenic neuropeptide Y and agouti-related peptide as well as anorexigenic proopiomelanocortin (POMC) are expressed, plays an important role in energy balance. In this study, we generated POMC-specific GABAB receptor-deficient [knock-out (KO)] mice. Male KO mice on a high-fat diet (HFD) showed mild increases in body weight (BW) at the age of 9 weeks compared to wild-type (WT) mice, and the differences remained significant until 16 weeks old. However, there was no difference in BW in females between genotypes. While food intake was similar between genotypes, oxygen consumption was significantly decreased in the male KO mice. The insulin tolerance test revealed that the male KO mice were less insulin sensitive compared to WT mice at the age of 8 weeks, when there was no significant difference in BW between genotypes. Despite increased BW, POMC mRNA expression in the arcuate nucleus was significantly decreased in the KO mice compared to WT mice at the age of 16 weeks. Furthermore, the expression of TNFα as well as IL-6, proinflammatory markers in the hypothalamus, was significantly increased in the KO mice on a HFD compared to WT mice. This demonstrates that the deletion of GABAB receptors in POMC neurons in the male mice on a HFD results in obesity, insulin resistance, and hypothalamic inflammation. Furthermore, the decreased POMC expression in the obese KO mice suggests that the regulation of POMC expression through GABAB receptors is essential for proper energy balance.

  11. Localization and expression of GABA transporters in the suprachiasmatic nucleus

    PubMed Central

    Moldavan, Michael; Cravetchi, Olga; Williams, Melissa; Irwin, Robert P.; Aicher, Sue A.; Allen, Charles N.

    2015-01-01

    GABA is a principal neurotransmitter in the suprachiasmatic hypothalamic nucleus (SCN), the master circadian clock. Despite the importance of GABA and GABA uptake for functioning of the circadian pacemaker, the localization and expression of GABA transporters (GATs) in the SCN has not been investigated. The present studies used Western blot analysis, immunohistochemistry, and electron microscopy to demonstrate the presence of GABA transporter 1 (GAT1) and GABA transporter 3 (GAT3) in the SCN. By light microscopy, GAT1 and GAT3 were co-localized throughout the SCN, but were not expressed in the perikarya of arginine vasopressin- or vasoactive intestinal peptide-immunoreactive (−ir) neurons of adult rats, nor in the neuronal processes labeled with the Neurofilament Heavy Chain. By electron microscopy, GAT1- and GAT3-ir was found in glial processes surrounding unlabeled neuronal perikarya, axons, dendrites, and enveloped symmetric and asymmetric axo-dendritic synapses. Glial Fibrillary Acidic Protein-ir astrocytes grown in cell culture were immunopositive for GAT1 and GAT3 – and both GATs could be observed in the same glial cell. These data demonstrate that synapses in the SCN function as “tripartite” synapses consisting of presynaptic axon terminals, postsynaptic membranes, and astrocytes that contain GABA transporters. This model suggests that astrocytes expressing both GATs may regulate the extracellular GABA, and thereby modulate the activity of neuronal networks in the SCN. PMID:26390912

  12. Function of taurine transporter (Slc6a6/TauT) as a GABA transporting protein and its relevance to GABA transport in rat retinal capillary endothelial cells.

    PubMed

    Tomi, Masatoshi; Tajima, Ayumi; Tachikawa, Masanori; Hosoya, Ken-ichi

    2008-10-01

    The purpose of this study was to identify the uptake mechanism of gamma-aminobutyric acid (GABA) via taurine transporter (Slc6a6/TauT) and its relationship with GABA transport at the inner BRB. Rat Slc6a6/TauT-transfected HeLa cells exhibited Na(+)-, Cl(-)-, and concentration-dependent [3H]GABA uptake with a Km of 1.5 mM. Taurine, beta-alanine, and GABA markedly inhibited Slc6a6/TauT-mediated uptake of [3H]GABA. The uptake of [3H]GABA by a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) was Na(+)-, Cl(-)-, and concentration-dependent with a Km of 2.0 mM. This process was more potently inhibited by substrates of Slc6a6/TauT, taurine and beta-alanine, than those of GABA transporters, GABA and betaine. In the presence of taurine, there was competitive inhibition with a Ki of 74 microM. [3H]Taurine also exhibited competitive inhibition with a Ki of 1.8 mM in the presence of GABA. In conclusion, rat Slc6a6/TauT has the ability to use GABA as a substrate and Slc6a6/TauT-mediated GABA transport appears to be present at the inner BRB.

  13. Endogenous synthesis of taurine and GABA in rat ocular tissues.

    PubMed

    Heinämäki, A A

    1988-01-01

    The endogenous production of taurine and gamma-aminobutyric acid (GABA) in rat ocular tissues was investigated. The activities of taurine-producing enzyme, cysteine sulfinic acid decarboxylase (CSAD), and GABA-synthesizing enzyme, glutamic acid decarboxylase (GAD), were observed in the retina, lens, iris-ciliary body and cornea. The highest specific activity of CSAD was in the cornea and that of GAD in the retina. The discrepancy between CSAD activity and taurine content within the ocular tissues indicates that intra- or extraocular transport processes may regulate the concentration of taurine in the rat eye. The GAD activity and the content of GABA were distributed in parallel within the rat ocular tissues. The quantitative results suggest that the GAD/GABA system has functional significance only in the retina of the rat eye.

  14. Edited magnetic resonance spectroscopy detects an age-related decline in brain GABA levels.

    PubMed

    Gao, Fei; Edden, Richard A E; Li, Muwei; Puts, Nicolaas A J; Wang, Guangbin; Liu, Cheng; Zhao, Bin; Wang, Huiquan; Bai, Xue; Zhao, Chen; Wang, Xin; Barker, Peter B

    2013-09-01

    Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the brain. Although measurements of GABA levels in vivo in the human brain using edited proton magnetic resonance spectroscopy ((1)H-MRS) have been established for some time, it is has not been established how regional GABA levels vary with age in the normal human brain. In this study, 49 healthy men and 51 healthy women aged between 20 and 76 years were recruited and J-difference edited spectra were recorded at 3T to determine the effect of age on GABA levels, and to investigate whether there are regional and gender differences in GABA in mesial frontal and parietal regions. Because the signal detected at 3.02 ppm using these experimental parameters is also expected to contain contributions from both macromolecules (MM) and homocarnosine, in this study the signal is labeled GABA+ rather than GABA. Significant negative correlations were observed between age and GABA+ in both regions studied (GABA+/Cr: frontal region, r=-0.68, p<0.001, parietal region, r=-0.54, p<0.001; GABA+/NAA: frontal region, r=-0.58, p<0.001, parietal region, r=-0.49, p<0.001). The decrease in GABA+ with age in the frontal region was more rapid in women than men. Evidence of a measureable decline in GABA is important in considering the neurochemical basis of the cognitive decline that is associated with normal aging.

  15. Comparative Mapping of GABA-Immunoreactive Neurons in the Buccal Ganglia of Nudipleura Molluscs.

    PubMed

    Gunaratne, Charuni A; Katz, Paul S

    2016-04-15

    Phylogenetic comparisons of neurotransmitter distribution are important for understanding the ground plan organization of nervous systems. This study describes the γ-aminobutyric acid (GABA)-immunoreactive (GABA-ir) neurons in the buccal ganglia of six sea slug species (Mollusca, Gastropoda, Euthyneura, Nudipleura). In the nudibranch species, Hermissenda crassicornis, Tritonia diomedea, Tochuina tetraquetra, and Dendronotus iris, the number of GABA-ir neurons was highly consistent. Another nudibranch, Melibe leonina, however, contained approximately half the number of GABA-ir neurons. This may relate to its loss of a radula and its unique feeding behavior. The GABA immunoreactivity in a sister group to the nudibranchs, Pleurobranchaea californica, differed drastically from that of the nudibranchs. Not only did it have significantly more GABA-ir neurons but it also had a unique GABA distribution pattern. Furthermore, unlike the nudibranchs, the Pleurobranchaea GABA distribution was also different from that of other, more distantly related, euopisthobranch and panpulmonate snails and slugs. This suggests that the Pleurobranchaea GABA distribution may be a derived feature, unique to this lineage. The majority of GABA-ir axons and neuropil in the Nudipleura were restricted to the buccal ganglia, commissures, and connectives. However, in Tritonia and Pleurobranchaea, we detected a few GABA-ir fibers in buccal nerves that innervate feeding muscles. Although the specific functions of the GABA-ir neurons in the species in this study are not known, the innervation pattern suggests these neurons may play an integrative or regulatory role in bilaterally coordinated behaviors in the Nudipleura.

  16. The action of GABA receptor agonists and antagonists on muscle membrane conductance in Schistocerca gregaria.

    PubMed Central

    Murphy, V. F.; Wann, K. T.

    1988-01-01

    1. The properties of postsynaptic gamma-aminobutyric acid (GABA) receptors in the extensor tibiae muscle of Schistocerca gregaria were studied by conventional electrophysiological recording techniques. 2. GABA and other active GABA receptor agonists produced rapid, dose-dependent, reversible increases in membrane conductance. 3. In two microelectrode experiments the ED50 for GABA was approximately 1 mM. In three microelectrode experiments (assuming short cable theory conditions) the ED50 for GABA was 2.3 mM. The Hill coefficient for GABA estimated from the latter experiments was 1.4. 4. The relative potency of muscimol/GABA at the ED50 for GABA was 1.36. 3-Aminopropane sulphonic acid (3-APS) and isonipecotic acid were weakly active, baclofen and piperidine-4-sulphonic acid (P4S) were inactive. Isoguvacine produced depolarizations and increases in conductance in preparations which hyperpolarized in response to GABA. These depolarizations were enhanced by both picrotoxin and pitrazepin although the increases in input conductance were depressed. 5. Picrotoxin (20 microM), (+)-bicuculline (20-100 microM) and pitrazepin (1-10 microM) all reversibly antagonized GABA-induced responses. Such antagonism was not competitive in the case of picrotoxin and (+)-bicuculline but was competitive for pitrazepin. Schild plot analysis gave an average pA2 value of 5.5 for pitrazepin. 6. The significance of these results is briefly discussed. PMID:2850061

  17. Distribution and ultrastructure of neurons in opossum piriform cortex displaying immunoreactivity to GABA and GAD and high-affinity tritiated GABA uptake

    SciTech Connect

    Haberly, L.B.; Hansen, D.J.; Feig, S.L.; Presto, S.

    1987-12-08

    GABAergic neurons have been identified in the piriform cortex of the opossum at light and electron microscopic levels by immunocytochemical localization of GABA and the GABA-synthesizing enzyme glutamic acid decarboxylase and by autoradiographic visualization of high-affinity /sup 3/H-GABA uptake. Four major neuron populations have been distinguished on the basis of soma size, shape, and segregation at specific depths and locations: large horizontal cells in layer Ia of the anterior piriform cortex, small globular cells with thin dendrites concentrated in layers Ib and II of the posterior piriform cortex, and multipolar and fusiform cells concentrated in the deep part of layer III in anterior and posterior parts of the piriform cortex and the subjacent endopiriform nucleus. All four populations were well visualized with both antisera, but the large layer Ia horizontal cells displayed only very light /sup 3/H-GABA uptake, thus suggesting a lack of local axon collaterals or lack of high-affinity GABA uptake sites. The large, ultrastructurally distinctive somata of layer Ia horizontal cells receive a very small number of symmetrical synapses; the thin, axonlike dendrites of small globular cells are exclusively postsynaptic and receive large numbers of both symmetrical and asymmetrical synapses, in contrast to somata which receive a small number of both types; and the deep multipolar and fusiform cells receive a highly variable number of symmetrical and asymmetrical synapses on somata and proximal dendrites. Labeled puncta of axon terminal dimensions were found in large numbers in the neuropil surrounding pyramidal cell somata in layer II and in the endopiriform nucleus. Moderately large numbers of labeled puncta were found in layer I at the depth of pyramidal cell apical dendrites with greater numbers in layer Ia at the depth of distal apical segments than in layer Ib.

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

    SciTech Connect

    Chen Ligong; Xue Ling; Giacomini, Kathleen M.; Casida, John E.

    2011-02-01

    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

  19. Thiocolchicoside inhibits the activity of various subtypes of recombinant GABA(A) receptors expressed in Xenopus laevis oocytes.

    PubMed

    Mascia, Maria Paola; Bachis, Elisabetta; Obili, Nicola; Maciocco, Elisabetta; Cocco, Giovanni Antonio; Sechi, Gian Pietro; Biggio, Giovanni

    2007-03-08

    Thiocolchicoside is a myorelaxant drug with anti-inflammatory and analgesic properties as well as pronounced convulsant activity. To characterize the mechanisms of action of this drug at the molecular level, we examined its effects on the function of various recombinant neurotransmitter receptors expressed in Xenopus oocytes. Electrophysiological recordings from recombinant human gamma-aminobutyric acid type A (GABA(A)) receptors consisting of alpha1beta1gamma2L, alpha1beta2gamma2L, or alpha2beta2gamma2L subunit combinations revealed that thiocolchicoside inhibited GABA-evoked Cl(-) currents with similar potencies (median inhibitory concentrations of 0.13 to 0.2 microM) and in a competitive manner. Consistent with previous observations, thiocolchicoside also inhibited the binding of GABA to rat cerebral cortical membranes. Thiocolchicoside inhibited the function of recombinant human strychnine-sensitive glycine receptors composed of the alpha1 subunit with a potency (median inhibitory concentration of 47 microM) lower than that apparent with recombinant GABA(A) receptors. It also inhibited the function of human nicotinic acetylcholine receptors composed of the alpha4 and beta2 subunits, but this effect was only partial and apparent at high concentrations. In contrast, thiocolchicoside had no effect on the function of 5-HT(3A) serotonin receptors. Our results thus provide molecular evidence that the epileptogenic activity of thiocolchicoside might be due to inhibition of the function of inhibitory receptors in the central nervous system, especially that of GABA(A) receptors.

  20. Effect of experimental diabetes on GABA-mediated inhibition of neurally induced contractions in rat isolated trachea.

    PubMed

    Ozdem, S S; Sadan, G; Usta, C; Taşatargil, A

    2000-04-01

    1. In the present study, we investigated the effect of GABA and selective GABA agonists and antagonists on neurally induced tracheal contractions in streptozotocin (STZ) diabetic rats. 2. Contractile responses to electrical field stimulation (EFS) in rat tracheal rings were completely abolished by atropine and tetrodotoxin, but were unaffected by the ganglion blocker hexamethonium, indicating that they were mediated via neuronal release of acetylcholine (ACh). 3. Contractions induced by EFS, but not by exogenous ACh, were inhibited by GABA and the selective GABA(B) receptor agonist baclofen, but not by the selective GABA(A) receptor agonist 3-aminopropane sulphonic acid. The inhibitory effects of GABA or baclofen were not affected by the GABA(A) antagonist bicuculline, but were significantly reversed by the GABA(B) antagonist phaclofen. 4. The inhibitory effects of both GABA and baclofen were found to be significantly greater in trachea from control rats compared with tissues from diabetic rats. 5. Non-adrenergic, non-cholinergic relaxation responses elicited by EFS in precontracted tracheal rings from diabetic and control rats were similar in magnitude and were unaffected by GABA or GABA analogues. 6. These results suggest that GABA decreases the response to EFS by directly inhibiting the evoked release of ACh through GABA(B) receptors in rat trachea and that STZ-induced diabetes causes an impairment in the inhibitory effect of GABA on neurally induced contractions in this tissue.

  1. GABA-A receptors regulate neocortical neuronal migration in vitro and in vivo.

    PubMed

    Heck, Nicolas; Kilb, Werner; Reiprich, Petra; Kubota, Hisahiko; Furukawa, Tomonori; Fukuda, Atsuo; Luhmann, Heiko J

    2007-01-01

    The cortical migration process depends on a number of trophic factors and on the activation of different voltage- and ligand-gated channels. We investigated the role of gamma-aminobutyric acid (GABA) type A receptors in the neuronal migration process of the newborn rat parietal cortex in vivo and in vitro. Local in vivo application of the GABA-A antagonist bicuculline methiodide (BMI) or the agonist muscimol via cortical surface Elvax implants induced prominent alterations in the cortical architecture when compared with untreated or sham-operated controls. BMI- and muscimol-treated animals revealed heterotopic cell clusters in the upper layers and a complete loss of the cortical lamination in the region underlying the Elvax implant. Immunocytochemical staining for glial fibrillary acidic protein, N-methyl-D-aspartate receptors, and GABA demonstrated that heterotopia was not provoked by glial proliferation and confirmed the presence of both glutamatergic and GABAergic neurons. In organotypic neocortical slices from embryonic day 18-19 embryos, application of BMI and to a lesser extent also muscimol induced an increase in the migration speed and an accumulation of neurons in the upper cortical layers. Spontaneous intracellular calcium ([Ca2+]i) oscillations in neocortical slices from newborn rats were abolished by BMI (5 and 20 microM) and muscimol (1 and 10 microM), indicating that both compounds interfere with [Ca2+]i signaling required for normal neuronal migration. Electrophysiological recordings from migrating neurons in newborn rat neocortical slices indicate that long-term application of muscimol causes a pronounced reduction (1 microM muscimol) or blockade (10 microM) in the responsiveness of postsynaptic GABA-A receptors due to a pronounced receptor desensitization. Our results indicate that modulation of GABA-A receptors by compounds acting as agonists or antagonists may profoundly influence the neuronal migration process in the developing cerebral cortex.

  2. Local GABA Concentration Predicts Perceptual Improvements After Repetitive Sensory Stimulation in Humans.

    PubMed

    Heba, Stefanie; Puts, Nicolaas A J; Kalisch, Tobias; Glaubitz, Benjamin; Haag, Lauren M; Lenz, Melanie; Dinse, Hubert R; Edden, Richard A E; Tegenthoff, Martin; Schmidt-Wilcke, Tobias

    2016-03-01

    Learning mechanisms are based on synaptic plasticity processes. Numerous studies on synaptic plasticity suggest that the regulation of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) plays a central role maintaining the delicate balance of inhibition and excitation. However, in humans, a link between learning outcome and GABA levels has not been shown so far. Using magnetic resonance spectroscopy of GABA prior to and after repetitive tactile stimulation, we show here that baseline GABA+ levels predict changes in perceptual outcome. Although no net changes in GABA+ are observed, the GABA+ concentration prior to intervention explains almost 60% of the variance in learning outcome. Our data suggest that behavioral effects can be predicted by baseline GABA+ levels, which provide new insights into the role of inhibitory mechanisms during perceptual learning.

  3. Photorelease of GABA with Visible Light Using an Inorganic Caging Group

    PubMed Central

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

    2008-01-01

    We describe the selective photorelease of γ-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. PMID:18946542

  4. 3H-GABA uptake selectively labels identifiable neurons in the leech central nervous system

    SciTech Connect

    Cline, H.T.

    1983-04-10

    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.

  5. The role of GABA in the regulation of GnRH neurons

    PubMed Central

    Watanabe, Miho; Fukuda, Atsuo; Nabekura, Junichi

    2014-01-01

    Gonadotropin-releasing hormone (GnRH) neurons form the final common pathway for the central regulation of reproduction. Gamma-amino butyric acid (GABA) has long been implicated as one of the major players in the regulation of GnRH neurons. Although GABA is typically an inhibitory neurotransmitter in the mature adult central nervous system, most mature GnRH neurons show the unusual characteristic of being excited by GABA. While many reports have provided much insight into the contribution of GABA to the activity of GnRH neurons, the precise physiological role of the excitatory action of GABA on GnRH neurons remains elusive. This brief review presents the current knowledge of the role of GABA signaling in GnRH neuronal activity. We also discuss the modulation of GABA signaling by neurotransmitters and neuromodulators and the functional consequence of GABAergic inputs to GnRH neurons in both the physiology and pathology of reproduction. PMID:25506316

  6. A Gut Feeling about GABA: Focus on GABAB Receptors

    PubMed Central

    Hyland, Niall P.; Cryan, John F.

    2010-01-01

    γ-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. PMID:21833169

  7. Receptor subtype-dependent positive and negative modulation of GABA(A) receptor function by niflumic acid, a nonsteroidal anti-inflammatory drug.

    PubMed

    Sinkkonen, Saku T; Mansikkamäki, Salla; Möykkynen, Tommi; Lüddens, Hartmut; Uusi-Oukari, Mikko; Korpi, Esa R

    2003-09-01

    In addition to blocking cyclooxygenases, members of the fenamate group of nonsteroidal anti-inflammatory drugs have been proposed to affect brain GABAA receptors. Using quantitative autoradiography with GABAA receptor-associated ionophore ligand [35S]t-butylbicyclophosphorothionate (TBPS) on rat brain sections, one of the fenamates, niflumate, at micromolar concentration was found to potentiate GABA actions in most brain areas, whereas being in the cerebellar granule cell layer an efficient antagonist similar to furosemide. With recombinant GABAA receptors expressed in Xenopus laevis oocytes, we found that niflumate potentiated 3 microM GABA responses up to 160% and shifted the GABA concentration-response curve to the left in alpha1beta2gamma2 receptors, the predominant GABAA receptor subtype in the brain. This effect needed the gamma2 subunit, because on alpha1beta2 receptors, niflumate exhibited solely an antagonistic effect at high concentrations. The potentiation was not abolished by the specific benzodiazepine site antagonist flumazenil. Niflumate acted as a potent antagonist of alpha6beta2 receptors (with or without gamma2 subunit) and of alphaXbeta2gamma2 receptors containing a chimeric alpha1 to alpha6 subunit, which suggests that niflumate antagonism is dependent on the same transmembrane domain 1- and 2-including fragment of the alpha6 subunit as furosemide antagonism. This antagonism was noncompetitive because the maximal GABA response, but not the potency, was reduced by niflumate. These data show receptor subtype-dependent positive and negative modulatory actions of niflumate on GABAA receptors at clinically relevant concentrations, and they suggest the existence of a novel positive modulatory site on alpha1beta2gamma2 receptors that is dependent on the gamma2 subunit but not associated with the benzodiazepine binding site.

  8. Study of GABA in Healthy Volunteers: Pharmacokinetics and Pharmacodynamics

    PubMed Central

    Li, Junfeng; Zhang, Zhaoyun; Liu, Xiaoxia; Wang, Yi; Mao, Fei; Mao, Junjun; Lu, Xiaolan; Jiang, Dongdong; Wan, Yun; Lv, Jia-Ying; Cao, Guoying; Zhang, Jing; Zhao, Naiqing; Atkinson, Mark; Greiner, Dale L.; Prud'homme, Gerald J.; Jiao, Zheng; Li, Yiming; Wang, Qinghua

    2015-01-01

    Preclinical studies show that GABA exerts anti-diabetic effects in rodent models of type 1 diabetes. Because little is known about its absorption and effects in humans, we investigated the pharmacokinetics and pharmacodynamics of GABA in healthy volunteers. Twelve subjects were subjected to an open-labeled, three-period trial involving sequential oral administration of placebo, 2 g GABA once, and 2 g GABA three times/day for 7 days, with a 7-day washout between each period. GABA was rapidly absorbed (Tmax: 0.5 ~ 1 h) with the half-life (t1/2) of 5 h. No accumulation was observed after repeated oral GABA administration for 7 days. Remarkably, GABA significantly increased circulating insulin levels in the subjects under either fasting (1.6-fold, single dose; 2.0-fold, repeated dose; p < 0.01) or fed conditions (1.4-fold, single dose; 1.6-fold, repeated dose; p < 0.01). GABA also increased glucagon levels only under fasting conditions (1.3-fold, single dose, p < 0.05; 1.5-fold, repeated dose, p < 0.01). However, there were no significant differences in the insulin-to-glucagon ratio and no significant change in glucose levels in these healthy subjects during the study period. Importantly, GABA significantly decreased glycated albumin levels in the repeated dosing period. Subjects with repeated dosing showed an elevated incidence of minor adverse events in comparison to placebo or the single dosing period, most notably transient discomforts such as dizziness and sore throat. However, there were no serious adverse events observed throughout the study. Our data show that GABA is rapidly absorbed and tolerated in human beings; its endocrine effects, exemplified by increasing islet hormonal secretion, suggest potential therapeutic benefits for diabetes. PMID:26617516

  9. The organophosphate sarin, at low concentrations, inhibits the evoked release of GABA in rat hippocampal slices.

    PubMed

    Chebabo, S R; Santos, M D; Albuquerque, E X

    1999-12-01

    In the present study, the whole-cell mode of the patch-clamp technique was applied to neurons of the CA1 pyramidal layer of rat hippocampal slices to investigate the effects of the organophosphate (OP) sarin on field stimulation-evoked and on tetrodotoxin (TTX)-insensitive postsynaptic currents (PSCs) mediated by activation of type A gamma-aminobutyric acid (GABA) receptors or AMPA-type glutamate receptors. At 0.3-1 nM, sarin reduced the amplitude of GABA-mediated PSCs and had no effect on the amplitude of glutamatergic PSCs evoked by field stimulation of neurons synaptically connected to the neuron under study. The effect of sarin on evoked GABAergic PSCs was unrelated to cholinesterase inhibition, was partially reversed upon washing of the neurons with sarin-free external solution, and was mediated by a direct interaction of the OP with muscarinic acetylcholine receptors present on presynaptic GABAergic neurons. Sarin had no effect on the amplitude or kinetics of GABA- or glutamate-mediated miniature postsynaptic currents (MPSCs) recorded in the presence of the Na+-channel blocker TTX (300 nM), indicating that the OP does not interact with GABA(A) or glutamate receptors. Further, sarin did not alter the frequency of GABAergic or glutamatergic MPSCs, a finding that led to the conclusion that this OP does not affect the TTX-insensitive release of neurotransmitters. A selective reduction by sarin of the action potential-dependent release of GABA in the hippocampus can account for the occurrence of seizures in intoxicated subjects.

  10. Benzodiazepines do not potentiate GABA responses in neonatal hippocampal neurons.

    PubMed

    Rovira, C; Ben-Ari, Y

    1991-09-16

    Benzodiazepines (midazolam; flunitrazepam) and pentobarbital increase the response to exogenous gamma-aminobutyric acid (GABA) in adult hippocampal cells. We report in this paper that in contrast pentobarbital but not benzodiazepine potentiate the effects of exogenous (GABA) in neurons recorded from slices of less than two weeks old. This finding suggests that the functional association of benzodiazepine and GABAA receptors is changed during early postnatal life.

  11. Expression of functional receptors by the human gamma-aminobutyric acid A gamma 2 subunit.

    PubMed

    Martínez-Torres, Ataúlfo; Miledi, Ricardo

    2004-03-02

    gamma-Aminobutyric acid A (GABA(A)) receptors are heteromeric membrane proteins formed mainly by various combinations of alpha, beta, and gamma subunits; and it is commonly thought that the gamma 2 subunit alone does not form functional receptors. In contrast, we found that cDNA encoding the gamma 2L subunit of the human GABA(A) receptor, injected alone into Xenopus oocytes, expressed functional GABA receptors whose properties were investigated by using the two-microelectrode voltage-clamp technique. GABA elicited desensitizing membrane currents that recovered after a few minutes' wash. Repetitive applications of GABA induced a "run-up" of GABA currents that nearly doubled the amplitude of the first response. The GABA currents inverted direction at about -30 mV, indicating that they are carried mainly by Cl(-) ions. The homomeric gamma 2L receptors were also activated by beta-alanine > taurine > glycine, and, like some types of heteromeric GABA(A) receptors, the gamma 2L receptors were blocked by bicuculline and were potentiated by pentobarbital and flunitrazepam. These results indicate that the human gamma 2L subunit is capable of forming fully functional GABA receptors by itself in Xenopus oocytes and suggest that the roles proposed for the various subunits that make up the heteromeric GABA(A) receptors in situ require further clarification.

  12. NSAIDs modulate GABA-activated currents via Ca2+-activated Cl− channels in rat dorsal root ganglion neurons

    PubMed Central

    ZHAO, LEI; LI, LI; MA, KE-TAO; WANG, YANG; LI, JING; SHI, WEN-YAN; ZHU, HE; ZHANG, ZHONG-SHUANG; SI, JUN-QIANG

    2016-01-01

    The ability of non-steroidal anti-inflammatory drugs (NSAIDs) to modulate γ-aminobutyrate (GABA)-activated currents via Ca2+-activated Cl− channels in rat dorsal root ganglion neurons (DRG), was examined in the present study. During the preparation of DRG neurons harvested from Sprague-Dawley rats, the whole-cell recording technique was used to record the effect of NSAIDs on GABA-activated inward currents, and the expression levels of the TMEM16A and TMEM16B subunits were revealed. In the event that DRG neurons were pre-incubated for 20 sec with niflumic acid (NFA) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) prior to the administration of GABA, the GABA-induced inward currents were diminished markedly in the majority of neurons examined (96.3%). The inward currents induced by 100 µmol/l GABA were attenuated by (0±0.09%; neurons = 4), (5.32±3.51%; neurons = 6), (21.3±4.00%; neurons = 5), (33.8±5.20%; neurons = 17), (52.2±5.10%; neurons = 4) and (61.1±4.12%; neurons = 12) by 0.1, 1, 3, 10, 30 and 100 µmol/l NFA, respectively. The inward currents induced by 100 µmol/l GABA were attenuated by (13.8±6%; neurons = 6), (23.2±14.7%; neurons = 6) and (29.7±9.1%; neurons = 9) by 3, 10 and 30 µmol/l NPPB, respectively. NFA and NPPB dose-dependently inhibited GABA-activated currents with half maximal inhibitory concentration (IC50) values of 6.7 and 11 µmol/l, respectively. The inhibitory effect of 100 µmol/l NFA on the GABA-evoked inward current were also strongly inhibited by nitrendipine (NTDP; an L-type calcium channel blocker), 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis (a highly selective calcium chelating reagent), caffeine (a widely available Ca2+ consuming drug) and calcium-free extracellular fluid, in a concentration-dependent manner. Immunofluorescent staining indicated that TMEM16A and TMEM16B expression was widely distributed in DRG neurons. The results suggest that NSAIDs may be able to regulate Ca2

  13. Influence of cold stress on contents of soluble sugars, vitamin C and free amino acids including gamma-aminobutyric acid (GABA) in spinach (Spinacia oleracea).

    PubMed

    Yoon, Young-Eun; Kuppusamy, Saranya; Cho, Kye Man; Kim, Pil Joo; Kwack, Yong-Bum; Lee, Yong Bok

    2017-01-15

    The contents of soluble sugars (sucrose, fructose, glucose, maltose and raffinose), vitamin C and free amino acids (34 compounds, essential and non-essential) were quantified in open-field and greenhouse-grown spinaches in response to cold stress using liquid chromatography. In general, greenhouse cultivation produced nutritionally high value spinach in a shorter growing period, where the soluble sugars, vitamin C and total amino acids concentrations, including essential were in larger amounts compared to those grown in open-field scenarios. Further, low temperature exposure of spinach during a shorter growth period resulted in the production of spinach with high sucrose, ascorbate, proline, gamma-aminobutyric acid, valine and leucine content, and these constitute the most important energy/nutrient sources. In conclusion, cultivation of spinach in greenhouse at a low temperature (4-7°C) and exposure for a shorter period (7-21days) before harvest is recommended. This strategy will produce a high quality product that people can eat.

  14. The activation of cannabinoid receptors in striatonigral GABAergic neurons inhibited GABA uptake.

    PubMed

    Romero, J; de Miguel, R; Ramos, J A; Fernández-Ruiz, J J

    1998-01-01

    Cannabinoid receptors (CNRs) in basal ganglia are located on striatal efferent neurons which are gamma-aminobutiric acid (GABA)-containing neurons. Recently, we have demonstrated that CN-induced motor inhibition is reversed by GABA-B, but not GABA-A, receptor antagonists, presumably indicating that the activation of CNRs in striatal outflow nuclei, mainly in the substantia nigra, should be followed by an increase of GABA concentrations into the synaptic cleft of GABA-B receptor synapses. The present study was designed to examine whether this was originated by increasing GABA synthesis and/or release or by decreasing GABA uptake. We analyzed: (i) GABA synthesis, by measuring the activity of glutamic acid decarboxylase (GAD) and GABA contents in brain regions that contain striatonigral GABAergic neurons, after in vivo administration of CNs and/or the CNR antagonist SR141716; (ii) [3H]GABA release in vitro in the presence or the absence of a synthetic CN agonist, HU-210, by using perifusion of small fragments of substantia nigra; and (iii) [3H]GABA uptake in vitro in the presence or the absence of WIN-55,212-2, by using synaptosomes obtained from either globus pallidus or substantia nigra. Results were as follows. Delta9-tetrahydrocannabinol (delta9-THC) and HU-210, did not alter neither GAD activity nor GABA contents in both the striatum and the ventral midbrain at any of the two times tested, thus suggesting that CNs apparently failed to change GABA synthesis in striatonigral GABAergic neurons. A similar lack of effect of HU-210 on in vitro [3H]GABA release, both basal and K+-evoked, was seen when this CN was added to perifused substantia nigra fragments, also suggesting no changes at the level of GABA release. However, when synaptosome preparations obtained from the substantia nigra were incubated in the presence of WIN-55,212-2, a decrease in [3H]GABA uptake could be measured. This lowering effect was specific of striatonigral GABAergic neurons since it was not

  15. Different transporter systems regulate extracellular GABA from vesicular and non-vesicular sources

    PubMed Central

    Song, Inseon; Volynski, Kirill; Brenner, Tanja; Ushkaryov, Yuri; Walker, Matthew; Semyanov, Alexey

    2013-01-01

    Tonic GABA type A (GABAA) conductance is a key factor regulating neuronal excitability and computation in neuronal networks. The magnitude of the tonic GABAA conductance depends on the concentration of ambient GABA originating from vesicular and non-vesicular sources and is tightly regulated by GABA uptake. Here we show that the transport system regulating ambient GABA responsible for tonic GABAA conductances in hippocampal CA1 interneurons depends on its source. In mice, GABA from vesicular sources is regulated by mouse GABA transporter 1 (mGAT1), while that from non-vesicular sources by mouse GABA transporters 3/4 (mGAT3/4). This finding suggests that the two transporter systems do not just provide backup for each other, but regulate distinct signaling pathways. This allows individual tuning of the two signaling systems and indicates that drugs designed to act at specific transporters will have distinct therapeutic actions. PMID:23494150

  16. Gamma-aminobutyric acid and related molecules in the sea fan Eunicella cavolini (Cnidaria: Octocorallia): a biochemical and immunohistochemical approach.

    PubMed

    Girosi, Laura; Ferrando, Sara; Beltrame, Francesco; Ciarcia, Gaetano; Diaspro, Alberto; Fato, Marco; Magnone, Mirko; Raiteri, Luca; Ramoino, Paola; Tagliafierro, Grazia

    2007-07-01

    The aim of this study has been the biochemical demonstration of the presence of gamma-aminobutyric acid (GABA) in the Mediterranean sea fan Eunicella cavolini by means of high-performance liquid chromatography, and the description of the distribution pattern of GABA and its related molecules, glutamic acid decarboxylase (GAD), vesicular GABA transporter (VGAT) and one of the GABA receptors (GABA(B) R) by immunohistochemical methods. The interrelationships of GABA, GAD and GABA receptor immunoreactivity have been established by using double-immunohistochemical methods and confocal microscopy. The immunodetection of monoclonal and/or polyclonal antibodies has revealed GABA immunoreactivity throughout the polyp tissue, both in neuronal and non-neuronal elements. GAD immunoreactivity has been mostly localized in the neuronal compartment, contacting epithelial and muscular elements. GABA(B) R immunoreactivity appears particularly intense in the nematocytes and in the oocyte envelope; its presence in GAD-immunoreactive neurons in the tentacles suggests an autocrine type of regulation. Western blot analysis has confirmed that a GABA(B) R, with a molecular weight of 142 kDa, similar to that of rat brain, is present in E. cavolini polyp tissue. The identification of the sites of the synthesis, vesicular transport, storage and reception of GABA strongly suggests the presence of an almost complete set of GABA-related molecules for the functioning of the GABAergic system in this simple nervous system. The distribution of these different immunoreactivities has allowed us to hypothesize GABA involvement in nematocyst discharge, in body wall and enteric muscular contraction, in neuronal integration and in male gametocyte differentiation.

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

    PubMed Central

    1995-01-01

    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

  18. Hypertonicity enhances GABA uptake by cultured rat retinal capillary endothelial cells.

    PubMed

    Yahara, Tohru; Tachikawa, Masanori; Akanuma, Shin-ichi; Hosoya, Ken-ichi

    2010-01-01

    We have reported previously that taurine transporter (TauT) mediates γ-aminobutyric acid (GABA) as a substrate in a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells). This study investigates how TauT-mediated GABA transport is regulated in TR-iBRB2 cells under hypertonic conditions. [³H]GABA uptake by TR-iBRB2 cells exposed to 12 h- to 24 h-hypertonic culture medium was significantly greater than that of isotonic culture medium. [³H]GABA uptake by TR-iBRB2 cells was Na(+)-, Cl(-)-, and concentration-dependent with a Michaelis-Menten (K(m)) constant of 3.5 mM under isotonic conditions and K(m) of 0.324 and 5.48 mM under hypertonic conditions. Under hypertonic conditions, [³H]GABA uptake by TR-iBRB2 cells was more potently inhibited by substrates of TauT, such as taurine and β-alanine, than those of GABA transporters such as GABA, nipecotic acid, and betaine. These results suggest that an unknown high-affinity GABA transport process and TauT-mediated GABA transport are enhanced under hypertonic conditions. In conclusion, hypertonicity enhances GABA uptake by cultured rat retinal capillary endothelial cells.

  19. GABA A/Bz receptor subtypes as targets for selective drugs.

    PubMed

    Da Settimo, F; Taliani, S; Trincavelli, M L; Montali, M; Martini, C

    2007-01-01

    The gamma-aminobutyric acid type A (GABA(A)) receptors are the major inhibitory neuronal receptors in the mammalian brain. Their activation by GABA opens the intrinsic ion channel, enabling chloride flux into the cell with subsequent hyperpolarization. Several GABA(A) receptor subunit isoforms have been cloned, the major isoform containing alpha, beta, and gamma subunits, and a regional heterogeneity associated with distinct physiological effects has been suggested. As a variety of allosteric ligands can modulate GABA-gated conductance changes through binding to distinct sites, the development of subtype-selective ligands may lead to the selective treatment of GABA system-associated pathology. In particular, the best characterized binding site is the benzodiazepine site (BzR), localized at the alpha/gamma subunit interface, in which the alpha subunit is the main determinant of BzR ligand action selectivity. The alpha1-containing BzR have been proposed to be responsible for the sedative action; the alpha2 and/or the alpha3 subtypes have been suggested to mediate the anxiolytic activity and the myorelaxation effects, and the alpha5 subtype has been associated with cognition processes. The discovery of alpha-selective subtype ligands may help in the specific treatment of anxiety, sleep disorders, convulsions and memory deficits with fewer side effects. Selectivity may be achieved by two approaches: selective affinity or selective efficacy. Selective affinity needs a compound to bind with a higher affinity to one receptor subtype compared with another, whereas subtype-selective efficacy relies on a compound binding to all subtypes, but having different efficacies at various subtypes. The status of BzR ligands, subdivided on the basis of their main chemical structural features, is reviewed in relation to structure-activity relationships which determine their affinity or efficacy selectivity for a certain BzR subtype.

  20. Mechanisms of carbacholine and GABA action on resting membrane potential and Na+/K+-ATPase of Lumbricus terrestris body wall muscles.

    PubMed

    Volkov, Eugeny M; Nurullin, Leniz F; Volkov, Michael E; Nikolsky, Eugeny E; Vyskočil, Frantisek

    2011-04-01

    This work was aimed to identify the action of several ion channel and pump inhibitors as well as nicotinic, GABAergic, purinergic and serotoninergic drugs on the resting membrane potential (RMP) and assess the role of cholinergic and GABAergic sensitivity in earthworm muscle electrogenesis. The nicotinic agonists acetylcholine (ACh), carbacholine (CCh) and nicotine depolarize the RMP at concentrations of 5 μM and higher. The nicotinic antagonists (+)tubocurarine, α-bungarotoxin, muscarinic antagonists atropine and hexamethonium do not remove or prevent the CCh-induced depolarization. Verapamil, tetrodotoxin, removal of Cl(-) and Ca(2+) from the solution also cannot prevent the depolarization by CCh. In a Na(+)-free medium, however, CCh lost this depolarization ability and this indicates that the drug opens the sodium permeable pathway. Serotonin, glutamate, glycine, adenosine triphosphate (ATP) and cis-4-aminocrotonic acid (GABA(C) receptor antagonist) had no effect on the RMP. On the other hand, isoguvacin, γ-aminobutyric acid (GABA) and baclofen (GABA(B) receptor agonist) hyperpolarized the RMP. Ouabain, bicucullin (GABA(A) antagonist) and phaclofen (GABA(B) antagonist), as well as the removal of Cl(-), suppressed the effect of GABA and baclofen. CCh did not enhance the depolarization generated by ouabain but, on the other hand, hindered the hyperpolarizing activity of baclofen both in the absence and presence of atropine and (+)tubocurarine. The long-term application of CCh depolarizes the RMP primarily by inhibiting the Na(+)/K(+)-ATPase. The muscle membrane also contains A and B type GABA binding sites, the activation of which increases the RMP at the expense of increasing the action of ouabain- and Cl(-) -sensitive electrogenic pumps.

  1. Prejunctional GABA-B inhibition of cholinergic, neurally-mediated airway contractions in guinea-pigs.

    PubMed

    Chapman, R W; Danko, G; Rizzo, C; Egan, R W; Mauser, P J; Kreutner, W

    1991-01-01

    GABA is a known inhibitory neurotransmitter in the CNS. Recent studies have also demonstrated the presence of GABA in peripheral tissue, including lung. To delineate a role for GABA in lung, the effect of GABA and selective GABA agonists and antagonists on neuronally-induced airway contractions in guinea pigs were studied. In vitro, tracheal contractions induced by electrical field stimulation (EFS) were inhibited by tetrodotoxin and atropine indicating that the contractions were mediated by neuronal release of acetylcholine. The contractions caused by EFS, but not those by exogenous acetylcholine, were inhibited by GABA (EC50 = 4.5 microM) and the selective GABA-B agonist baclofen (EC50 = 9 microM), but not by the GABA-A agonist, muscimol. The inhibitory effect of baclofen was not affected by the GABA-A antagonist, bicuculline, but was significantly reversed with the GABA-B antagonists, 3-aminopropylphosphonic acid (3-APPA) (pA2 = 4.5) and 2-hydroxysaclofen (pA2 = 4.1). In vivo, vagal nerve stimulation (5 V, 20 Hz, 0.5 ms, 5 s) in anesthetized, mechanically ventilated guinea-pigs caused cholinergic-dependent bronchospasms that were inhibited by intravenous GABA (3 and 10 mg/kg) and baclofen (1-10 mg/kg), but not by muscimol. The inhibitory effects of GABA and baclofen against vagal bronchospasm were blocked by 3-APPA (5 mg/kg, i.v.), but not by bicuculline. Responses to the GABA-B agonists were unaltered after the treatment of animals with phentolamine or propranolol to block alpha-adrenergic and beta-adrenergic receptors, respectively. Bronchospasm due to intravenous methacholine was also unchanged by GABA and baclofen.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Evidence for a Revised Ion/Substrate Coupling Stoichiometry of GABA Transporters.

    PubMed

    Willford, Samantha L; Anderson, Cynthia M; Spencer, Shelly R; Eskandari, Sepehr

    2015-08-01

    Plasma membrane γ-aminobutyric acid (GABA) transporters (GATs) are electrogenic transport proteins that couple the cotranslocation of Na(+), Cl(-), and GABA across the plasma membrane of neurons and glia. A fundamental property of the transporter that determines its ability to concentrate GABA in cells and, hence, regulate synaptic and extra-synaptic GABA concentrations, is the ion/substrate coupling stoichiometry. Here, we scrutinized the currently accepted 2 Na(+):1 Cl(-):1 GABA stoichiometry because it is inconsistent with the measured net charge translocated per co-substrate (Na(+), Cl(-), and GABA). We expressed GAT1 and GAT3 in Xenopus laevis oocytes and utilized thermodynamic and uptake under voltage-clamp measurements to determine the stoichiometry of the GABA transporters. Voltage-clamped GAT1-expressing oocytes were internally loaded with GABA, and the reversal potential (V rev) of the transporter-mediated current was recorded at different external concentrations of Na(+), Cl(-), or GABA. The shifts in V rev for a tenfold change in the external Na(+), Cl(-), and GABA concentration were 84 ± 4, 30 ± 1, and 29 ± 1 mV, respectively. To determine the net charge translocated per Na(+), Cl(-), and GABA, we measured substrate fluxes under voltage clamp in cells expressing GAT1 or GAT3. Charge flux to substrate flux ratios were 0.7 ± 0.1 charge/Na(+), 2.0 ± 0.2 charges/Cl(-), and 2.1 ± 0.1 charges/GABA. Altogether, our results strongly suggest a 3 Na(+):1 Cl(-):1 GABA coupling stoichiometry for the GABA transporters. The revised stoichiometry has important implications for understanding the contribution of GATs to GABAergic signaling in health and disease.

  3. gamma-Aminobutyric acid (GABA): a fast excitatory transmitter which may regulate the development of hippocampal neurones in early postnatal life.

    PubMed

    Ben-Ari, Y; Tseeb, V; Raggozzino, D; Khazipov, R; Gaiarsa, J L

    1994-01-01

    The properties of neonatal GABAergic synapses were investigated in neurones of the hippocampal CA3 region. GABA, acting on GABAA receptors, provides most of the excitatory drive on immature CA3 pyramidal neurones at an early stage of development, whereas glutamatergic synapses (in particular, those mediated by AMPA receptors) are mostly quiescent. Thus, during the first postnatal week of life, bicuculline fully blocked spontaneous and evoked depolarising potentials, and GABAA receptor agonists depolarised CA3 pyramidal neurones. GABAA mediated currents also had a reduced sensitivity to benzodiazepines. In the presence of bicuculline, between P0 and P4, increasing the stimulus strength reveals an excitatory postsynaptic potential which is mostly mediated by NMDA receptors. During the same developmental period, pre- (but not post) synaptic GABAB inhibition is present. Intracellular injections of biocytin showed that the axonal network of the GABAergic interneurones is well developed at birth, whereas the pyramidal recurrent collaterals are only beginning to develop. Finally, chronic bicuculline treatment of hippocampal neurones in culture reduced the extent of neuritic arborisation, suggesting that GABA acts as a trophic factor in that period. In conclusion, it is suggested that during the first postnatal week of life, when excitatory inputs are still poorly developed, GABAA receptors provide the excitatory drive necessary for pyramidal cell outgrowth. Starting from the end of the first postnatal week of life, when excitatory inputs are well developed, GABA (acting on both GABAA and GABAB receptors) will hyperpolarise the CA3 pyramidal neurones and, as in the adult, will prevent excessive neuronal discharges. Our electrophysiological and morphological studies have shown that hippocampal GABAergic interneurones are in a unique position to modulate the development of CA3 pyramidal neurones. Developing neurones require a certain degree of membrane depolarisation, and a

  4. Dopamine-dependent hyperactivity in the rat following manipulation of GABA mechanisms in the region of the nucleus accumbens.

    PubMed

    Pycock, C J; Horton, R W

    1979-01-01

    The effect of manipulation of GABA mechanisms in the region of the nucleus accumbens on dopamine-dependent locomotor hyperactivity in the rat has been studied. Two models of hyperactivity were used: (1) the injection of dopamine into the region of the nucleus accumbens in nialamide-pretreated animals and (2) the systemic administration of d-amphetamine. Both GABA and the GABA agonist 3-aminopropane sulphonic acid (3-APS) depressed hyperactivity in a dose-related manner. High concentrations of GABA (greater than 100 micrograms) were required to produce a significant effect and the response was short-lived possibly reflecting the efficient GABA inactivating mechanisms. 3-APS proved to be approximately 10 times more potent as compared to GABA in the dopamine-accumbens hyperactivity model. Conversely GABA receptor antagonism with low doses of either picrotoxin or bicuculline enhanced the mild locomotor response induced by a low dose of dopamine injected into the nucleus accumbens. However such results were difficult to evaluate fairly as higher doses of the GABA antagonists resulted in varying degrees of generalized seizures. Blockade of GABA uptake systems with cis-1, 3-aminocyclohexane carboxylic acid (ACHC), nipecotic acid or beta-alanine within the region of the nucleus accumbens produced dose-related depression of dopamine-dependent hyperactivity in both models. GABA uptake blockade (nipecotic acid) significantly enhanced the GABA-mediated depression of hyperactivity induced by bilateral injection of dopamine into the nucleus accumbens. The results demonstrate an inhibitory action of GABA and drugs facilitating GABA-ergic transmission on dopamine-dependent hyperactivity in the rat. Although open to criticisms of not being able to distinguish between true GABA effects and the results of non-specific neuronal depression the hyperactivity model underlines the potency of the GABA uptake blocking compounds and their possible potential for future clinical use.

  5. Pressure-Dependent Changes in the Release of GABA by Cerebrocortical Synaptosomes

    DTIC Science & Technology

    1989-01-01

    DTICL9? Undersea Biomedical Research, Vol. 16, No. 3. 1989 N V918f, NOV09198 B U Pressure-dependent changes in the release of GABA 1 by...Center, Bothesda. Maryland 20814-5055 Gilman SC, Colton JS, Dutka AJ. Pressure-dependent changes in the release of GABA by cerebrocortical synaptosomes...evoked [3H]--aminobutyric acid ( GABA ) release from isolated presynaptic terminals (synaptosomes) (15, 16). The current study was designed to evaluate

  6. GABA Signaling and Neuroactive Steroids in Adrenal Medullary Chromaffin Cells

    PubMed Central

    Harada, Keita; Matsuoka, Hidetada; Fujihara, Hiroaki; Ueta, Yoichi; Yanagawa, Yuchio; Inoue, Masumi

    2016-01-01

    Gamma-aminobutyric acid (GABA) is produced not only in the brain, but also in endocrine cells by the two isoforms of glutamic acid decarboxylase (GAD), GAD65 and GAD67. In rat adrenal medullary chromaffin cells only GAD67 is expressed, and GABA is stored in large dense core vesicles (LDCVs), but not synaptic-like microvesicles (SLMVs). The α3β2/3γ2 complex represents the majority of GABAA receptors expressed in rat and guinea pig chromaffin cells, whereas PC12 cells, an immortalized rat chromaffin cell line, express the α1 subunit as well as the α3. The expression of α3, but not α1, in PC12 cells is enhanced by glucocorticoid activity, which may be mediated by both the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). GABA has two actions mediated by GABAA receptors in chromaffin cells: it induces catecholamine secretion by itself and produces an inhibition of synaptically evoked secretion by a shunt effect. Allopregnanolone, a neuroactive steroid which is secreted from the adrenal cortex, produces a marked facilitation of GABAA receptor channel activity. Since there are no GABAergic nerve fibers in the adrenal medulla, GABA may function as a para/autocrine factor in the chromaffin cells. This function of GABA may be facilitated by expression of the immature isoforms of GAD and GABAA receptors and the lack of expression of plasma membrane GABA transporters (GATs). In this review, we will consider how the para/autocrine function of GABA is achieved, focusing on the structural and molecular mechanisms for GABA signaling. PMID:27147972

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

    PubMed Central

    De Ita-Pérez, Dalia; Vázquez-Martínez, Olivia; Villalobos-Leal, Mónica

    2014-01-01

    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. γ-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. PMID:24809054

  8. Cross-talk between P2X4 and gamma-aminobutyric acid, type A receptors determines synaptic efficacy at a central synapse.

    PubMed

    Jo, Young-Hwan; Donier, Emmanuelle; Martinez, Audrey; Garret, Maurice; Toulmé, Estelle; Boué-Grabot, Eric

    2011-06-03

    The essence of neuronal function is to generate outputs in response to synaptic potentials. Synaptic integration at postsynaptic sites determines neuronal outputs in the CNS. Using immunohistochemical and electrophysiological approaches, we first reveal that steroidogenic factor 1 (SF-1) green fluorescent protein (GFP)-positive neurons in the ventromedial nucleus of the hypothalamus express P2X4 subunits that are activated by exogenous ATP. Increased membrane expression of P2X4 channels by using a peptide competing with P2X4 intracellular endocytosis motif enhances neuronal excitability of SF-1 GFP-positive neurons. This increased excitability is inhibited by a P2X receptor antagonist. Furthermore, increased surface P2X4 receptor expression significantly decreases the frequency and the amplitude of GABAergic postsynaptic currents of SF-1 GFP-positive neurons. Co-immunopurification and pulldown assays reveal that P2X4 receptors complex with aminobutyric acid, type A (GABA(A)) receptors and demonstrate that two amino acids in the carboxyl tail of the P2X4 subunit are crucial for its physical association with GABA(A) receptors. Mutation of these two residues prevents the physical association, thereby blocking cross-inhibition between P2X4 and GABA(A) receptors. Moreover, disruption of the physical coupling using competitive peptides containing the identified motif abolishes current inhibition between P2X4 and GABA(A) receptors in recombinant system and P2X4 receptor-mediated GABAergic depression in SF-1 GFP-positive neurons. Our present work thus provides evidence for cross-talk between excitatory and inhibitory receptors that appears to be crucial in determining GABAergic synaptic strength at a central synapse.

  9. Parkinson's Disease and Neurodegeneration: GABA-Collapse Hypothesis

    PubMed Central

    Błaszczyk, Janusz W.

    2016-01-01

    Neurodegenerative diseases constitute a heterogeneous group of age-related disorders that are characterized by a slow but irreversible deterioration of brain functions. Evidence accumulated over more than two decades has implicated calcium-related homeostatic mechanisms, giving rise to the Ca2+ hypothesis of brain aging and, ultimately, cell death. Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter within the central (CNS), peripheral and enteric nervous systems. It appears to be involved in a wide variety of physiological functions within and outside the nervous system, that are maintained through a complex interaction between GABA and calcium-dependent neurotransmission and cellular metabolic functions. Within CNS the Ca2+/GABA mechanism stabilizes neuronal activity both at cellular and systemic levels. Decline in the Ca2+/GABA control initiates several cascading processes leading to both weakened protective barriers (in particular the blood-brain barrier) and accumulations of intracellular deposits of calcium and Lewy bodies. Linking such a vital mechanism of synaptic transmission with metabolism (both at cellular and tissue level) by means of a common reciprocal Ca2+/GABA inhibition results in a fragile balance, which is prone to destabilization and auto-destruction. The GABA decline etiology proposed here appears to apply to all human neurodegenerative processes initiated by abnormal intracellular calcium levels. Therefore, the original description of Parkinson's disease (PD) as due to the selective damage of dopaminergic neurons in the mesencephalon should be updated into the concept of a severe multisystemic neurodegenerative disorder of the nervous system, whose clinical symptoms reflect the localization and progression of the most advanced GABA pathology. A future and more complete therapeutic approach to PD should be aimed first at slowing (or stopping) the progression of Ca2+/GABA functional decline. PMID:27375426

  10. Effect of antioxidant treatment on spinal GABA neurons in a neuropathic pain model in the mouse.

    PubMed

    Yowtak, June; Wang, Jigong; Kim, Hee Young; Lu, Ying; Chung, Kyungsoon; Chung, Jin Mo

    2013-11-01

    One feature of neuropathic pain is a reduced spinal gamma-aminobutyric acid (GABA)-ergic inhibitory function. However, the mechanisms behind this attenuation remain to be elucidated. This study investigated the involvement of reactive oxygen species in the spinal GABA neuron loss and reduced GABA neuron excitability in spinal nerve ligation (SNL) model of neuropathic pain in mice. The importance of spinal GABAergic inhibition in neuropathic pain was tested by examining the effects of intrathecally administered GABA receptor agonists and antagonists in SNL and naïve mice, respectively. The effects of SNL and antioxidant treatment on GABA neuron loss and functional changes were examined in transgenic GAD67-enhanced green fluorescent protein positive (EGFP+) mice. GABA receptor agonists transiently reversed mechanical hypersensitivity of the hind paw in SNL mice. On the other hand, GABA receptor antagonists made naïve mice mechanically hypersensitive. Stereological analysis showed that the numbers of enhanced green fluorescent protein positive (EGFP+) GABA neurons were significantly decreased in the lateral superficial laminae (I-II) on the ipsilateral L5 spinal cord after SNL. Repeated antioxidant treatments significantly reduced the pain behaviors and prevented the reduction in EGFP+ GABA neurons. The response rate of the tonic firing GABA neurons recorded from SNL mice increased with antioxidant treatment, whereas no change was seen in those recorded from naïve mice, which suggested that oxidative stress impaired some spinal GABA neuron activity in the neuropathic pain condition. Together the data suggest that neuropathic pain, at least partially, is attributed to oxidative stress, which induces both a GABA neuron loss and dysfunction of surviving GABA neurons.

  11. α-Thujone (the active component of absinthe): γ-Aminobutyric acid type A receptor modulation and metabolic detoxification

    PubMed Central

    Höld, Karin M.; Sirisoma, Nilantha S.; Ikeda, Tomoko; Narahashi, Toshio; Casida, John E.

    2000-01-01

    α-Thujone is the toxic agent in absinthe, a liqueur popular in the 19th and early 20th centuries that has adverse health effects. It is also the active ingredient of wormwood oil and some other herbal medicines and is reported to have antinociceptive, insecticidal, and anthelmintic activity. This study elucidates the mechanism of α-thujone neurotoxicity and identifies its major metabolites and their role in the poisoning process. Four observations establish that α-thujone is a modulator of the γ-aminobutyric acid (GABA) type A receptor. First, the poisoning signs (and their alleviation by diazepam and phenobarbital) in mice are similar to those of the classical antagonist picrotoxinin. Second, a strain of Drosophila specifically resistant to chloride channel blockers is also tolerant to α-thujone. Third, α-thujone is a competitive inhibitor of [3H]ethynylbicycloorthobenzoate binding to mouse brain membranes. Most definitively, GABA-induced peak currents in rat dorsal root ganglion neurons are suppressed by α-thujone with complete reversal after washout. α-Thujone is quickly metabolized in vitro by mouse liver microsomes with NADPH (cytochrome P450) forming 7-hydroxy-α-thujone as the major product plus five minor ones (4-hydroxy-α-thujone, 4-hydroxy-β-thujone, two other hydroxythujones, and 7,8-dehydro-α-thujone), several of which also are detected in the brain of mice treated i.p. with α-thujone. The major 7-hydroxy metabolite attains much higher brain levels than α-thujone but is less toxic to mice and Drosophila and less potent in the binding assay. The other metabolites assayed are also detoxification products. Thus, α-thujone in absinthe and herbal medicines is a rapid-acting and readily detoxified modulator of the GABA-gated chloride channel. PMID:10725394

  12. Conformationally sensitive proximity of extracellular loops 2 and 4 of the γ-aminobutyric acid (GABA) transporter GAT-1 inferred from paired cysteine mutagenesis.

    PubMed

    Hilwi, Maram; Dayan, Oshrat; Kanner, Baruch I

    2014-12-05

    The sodium- and chloride-coupled GABA transporter GAT-1 is a member of the neurotransmitter:sodium:symporters, which are crucial for synaptic transmission. Structural work on the bacterial homologue LeuT suggests that extracellular loop 4 closes the extracellular solvent pathway when the transporter becomes inward-facing. To test whether this model can be extrapolated to GAT-1, cysteine residues were introduced at positions 359 and 448 of extracellular loop 4 and transmembrane helix 10, respectively. Treatment of HeLa cells, expressing the double cysteine mutant S359C/K448C with the oxidizing reagent copper(II)(1,10-phenantroline)3, resulted in a significant inhibition of [(3)H]GABA transport. However, transport by the single cysteine mutant S359C was also inhibited by the oxidant, whereas its activity was almost 4-fold stimulated by dithiothreitol. Both effects were attenuated when the conserved cysteine residues, Cys-164 and/or Cys-173, were replaced by serine. These cysteines are located in extracellular loop 2, the role of which in the structure and function of the eukaryotic neurotransmitter:sodium:symporters remains unknown. The inhibition of transport of S359C by the oxidant was markedly reduced under conditions expected to increase the proportion of inward-facing transporters, whereas the reactivity of the mutants to a membrane-impermeant sulfhydryl reagent was not conformationally sensitive. Our data suggest that extracellular loops 2 and 4 come into close proximity to each other in the outward-facing conformation of GAT-1.

  13. A study on quality components and sleep-promoting effects of GABA black tea.

    PubMed

    Zhao, Wenfang; Li, Yun; Ma, William; Ge, Yazhong; Huang, Yahui

    2015-10-01

    The aims of this study were to analyze the changes in quality components of gamma (γ)-aminobutyric acid (GABA) black tea during processing, and to investigate the effect of three dosages of GABA black tea on sleep improvement. The results showed that the GABA content was increased significantly up to 2.70 mg g(-1) after vacuum anaerobic and aerobic treatment. In addition, the content of GABA after drying reached 2.34 mg g(-1), which achieved the standard of GABA tea. During the entire processing of GABA black tea, the contents of tea polyphenols, caffeine and total catechins displayed a gradually descending trend, while the contents of free amino acids and GABA were firstly increased, and then reduced. The GABA black tea had significant effects on prolonging the sleeping time with sodium pentobarbital (P < 0.05) and significantly enhancing the sleeping rate induced by sodium pentobarbital at a sub-threshold dose (P < 0.05). But its effect on shortening the sleeping latency period induced by sodium barbital was not significant (P > 0.05). It had no effect on directly inducing sleep and the mouse body weight. The extract of GABA black tea improved the sleeping quality of mice to extend with an optimal effect being found in the high dose-treated mice.

  14. Pharmacological characterisation of a cell line expressing GABA B1b and GABA B2 receptor subunits.

    PubMed

    Hirst, Warren D; Babbs, Adam J; Green, Andrew; Minton, Jayne A L; Shaw, Tracy E; Wise, Alan; Rice, Simon Q; Pangalos, Menelas N; Price, Gary W

    2003-04-01

    The gamma-aminobutyric acid (GABA(B)) receptor has been shown to be a heterodimer consisting of two receptor subunits, GABA(B1) and GABA(B2). We have stably co-expressed these two subunits in a CHO cell line, characterised its pharmacology and compared it to the native receptor in rat brain membranes. Radioligand binding using [3H]CGP54626A demonstrated a similar rank order of potency between recombinant and native receptors: CGP62349>CGP54626A>SCH 50911>3-aminopropylphosphinicacid(3-APPA)>GABA>baclofen>saclofen>phaclofen. However, differences were observed in the affinity of agonists, which were higher at the native receptor, suggesting that in the recombinant system a large number of the receptors were in the low agonist affinity state. In contrast, [35S]GTPgammaS binding studies did not show any differences between recombinant and native receptors with the full agonists GABA and 3-APPA. Measurement of cAMP accumulation in the cells revealed a degree of endogenous coupling of the receptors to G-proteins. This is most likely to be due to the high expression levels of receptors (B(max)=22.5+/-2.5pmol/mg protein) in this experimental system. There was no evidence of GABA(B2) receptors, when expressed alone, binding [3H]CGP54626A, [3H]GABA, [3H]3-APPA nor of GABA having any effect on basal [35S]GTPgammaS binding or cAMP levels.

  15. Structural requirements for eszopiclone and zolpidem binding to the gamma-aminobutyric acid type-A (GABAA) receptor are different.

    PubMed

    Hanson, Susan M; Morlock, Elaine V; Satyshur, Kenneth A; Czajkowski, Cynthia

    2008-11-27

    The sleep-aids zolpidem and eszopiclone exert their effects by binding to and modulating gamma-aminobutyric acid type-A receptors (GABA(A)Rs), but little is known about the structural requirements for their actions. We made 24 cysteine mutations in the benzodiazepine (BZD) binding site of alpha(1)beta(2)gamma(2) GABA(A)Rs and measured zolpidem, eszopiclone, and BZD-site antagonist binding. Mutations in gamma(2)loop D and alpha(1)loops A and B altered the affinity of all ligands tested, indicating that these loops are important for BZD pocket structural integrity. In contrast, gamma(2)loop E and alpha(1)loop C mutations differentially affected ligand affinity, suggesting that these loops are important for ligand selectivity. In agreement with our mutagenesis data, eszopiclone docking yielded a single model stabilized by several hydrogen bonds. Zolpidem docking yielded three equally populated orientations with few polar interactions, suggesting that unlike eszopiclone, zolpidem relies more on shape recognition of the binding pocket than on specific residue interactions and may explain why zolpidem is highly alpha(1)- and gamma(2)-subunit selective.

  16. Downregulation of GABA[Subscript A] Receptor Protein Subunits a6, ß2, d, e, ?2, ?, and ?2 in Superior Frontal Cortex of Subjects with Autism

    ERIC Educational Resources Information Center

    Fatemi, S. Hossein; Reutiman, Teri J.; Folsom, Timothy D.; Rustan, Oyvind G.; Rooney, Robert J.; Thuras, Paul D.

    2014-01-01

    We measured protein and mRNA levels for nine gamma-aminobutyric acid A (GABA[subscript A]) receptor subunits in three brain regions (cerebellum, superior frontal cortex, and parietal cortex) in subjects with autism versus matched controls. We observed changes in mRNA for a number of GABA[subscript A] and GABA[subscript B] subunits and overall…

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

    PubMed

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

    2001-09-01

    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.

  18. Differential properties of type I and type II benzodiazepine receptors in mammalian CNS neurones.

    PubMed Central

    Yakushiji, T.; Shirasaki, T.; Munakata, M.; Hirata, A.; Akaike, N.

    1993-01-01

    1. The effects of benzodiazepine receptor (BZR) partial agonists, Y-23684 and CL218,872, were compared with its full agonist, diazepam, on gamma-aminobutyric acid (GABA)-induced Cl- current (ICl) in acutely dissociated rat cerebral cortex (CTX), cerebellar Purkinje (CPJ) and spinal ventral horn (SVH) neurones, by the whole-cell mode patch-clamp technique. 2. The GABA-induced responses were essentially the same in both SVH and CPJ neurones, but the KD value of the GABA response in CTX neurone was lower than those in the other two brain regions. 3. Enhancement of the GABA response by the two partial agonists was about one-third of that by diazepam in the SVH neurones (where type II subtype of BZR, BZ2, is predominant), whereas these partial agonists potentiated the GABA response as much as diazepam in CPJ neurones (where the type I subtype of BZR, BZ1, is predominant). In CTX neurones where both type I and II variants are expressed, the augmentation ratio of the GABA response by diazepam was between the values in CPJ and SVH neurones. 4. In concentration-response relationships of BZR partial agonists, the threshold concentrations, KD values and maximal augmentation ratio of the GABA response were similar in all CTX, CPJ and SVH neurones. Also, in all preparations, the threshold concentration and KD values of diazepam action were 10 fold less than those induced by partial agonists. 5. All BZR agonists shifted the concentration-response relationship for GABA to the left without changing the maximum current amplitude, indicating that activation of both BZ1 and BZ2 increase the affinity of the GABAA receptor for GABA.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8395299

  19. Differential properties of type I and type II benzodiazepine receptors in mammalian CNS neurones.

    PubMed

    Yakushiji, T; Shirasaki, T; Munakata, M; Hirata, A; Akaike, N

    1993-07-01

    1. The effects of benzodiazepine receptor (BZR) partial agonists, Y-23684 and CL218,872, were compared with its full agonist, diazepam, on gamma-aminobutyric acid (GABA)-induced Cl- current (ICl) in acutely dissociated rat cerebral cortex (CTX), cerebellar Purkinje (CPJ) and spinal ventral horn (SVH) neurones, by the whole-cell mode patch-clamp technique. 2. The GABA-induced responses were essentially the same in both SVH and CPJ neurones, but the KD value of the GABA response in CTX neurone was lower than those in the other two brain regions. 3. Enhancement of the GABA response by the two partial agonists was about one-third of that by diazepam in the SVH neurones (where type II subtype of BZR, BZ2, is predominant), whereas these partial agonists potentiated the GABA response as much as diazepam in CPJ neurones (where the type I subtype of BZR, BZ1, is predominant). In CTX neurones where both type I and II variants are expressed, the augmentation ratio of the GABA response by diazepam was between the values in CPJ and SVH neurones. 4. In concentration-response relationships of BZR partial agonists, the threshold concentrations, KD values and maximal augmentation ratio of the GABA response were similar in all CTX, CPJ and SVH neurones. Also, in all preparations, the threshold concentration and KD values of diazepam action were 10 fold less than those induced by partial agonists. 5. All BZR agonists shifted the concentration-response relationship for GABA to the left without changing the maximum current amplitude, indicating that activation of both BZ1 and BZ2 increase the affinity of the GABAA receptor for GABA. 6. The results are important in clarifying the mechanism of anxiety and might explain the anxioselectivity of BZR partial agonists.

  20. Subunit-specific coupling between gamma-aminobutyric acid type A and P2X2 receptor channels.

    PubMed

    Boué-Grabot, Eric; Toulmé, Estelle; Emerit, Michel B; Garret, Maurice

    2004-12-10

    ATP and gamma-aminobutyric acid (GABA) are two fast neurotransmitters co-released at central synapses, where they co-activate excitatory P2X and inhibitory GABAA (GABA type A) receptors. We report here that co-activation of P2X2 and various GABAA receptors, co-expressed in Xenopus oocytes, leads to a functional cross-inhibition dependent on GABAA subunit composition. Sequential applications of GABA and ATP revealed that alphabeta- or alphabetagamma-containing GABAA receptors inhibited P2X2 channels, whereas P2X2 channels failed to inhibit gamma-containing GABAA receptors. This functional cross-talk is independent of membrane potential, changes in current direction, and calcium. Non-additive responses observed between cation-selective GABAA and P2X2 receptors further indicate the chloride independence of this process. Overexpression of minigenes encoding either the C-terminal fragment of P2X2 or the intracellular loop of the beta3 subunit disrupted the functional cross-inhibition. We previously demonstrated functional and physical cross-talk between rho1 and P2X2 receptors, which induced a retargeting of rho1 channels to surface clusters when co-expressed in hippocampal neurons (Boue-Grabot, E., Emerit, M. B., Toulme, E., Seguela, P., and Garret, M. (2004) J. Biol. Chem. 279, 6967-6975). Co-expression of P2X2 and chimeric rho1 receptors with the C-terminal sequences of alpha2, beta3, or gamma2 subunits indicated that only rho1-beta3 and P2X2 channels exhibit both functional cross-inhibition in Xenopus oocytes and co-clustering/retargeting in hippocampal neurons. Therefore, the C-terminal domain of P2X2 and the intracellular loop of beta GABAA subunits are required for the functional interaction between ATP- and GABA-gated channels. This gamma subunit-dependent cross-talk may contribute to the regulation of synaptic activity.

  1. Edited Magnetic Resonance Spectroscopy Detects an Age-Related Decline in Nonhuman Primate Brain GABA Levels

    PubMed Central

    Killiany, Ronald J.

    2016-01-01

    Recent research had shown a correlation between aging and decreasing Gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain. However, how GABA level varies with age in the medial portion of the brain has not yet been studied. The purpose of this study was to investigate the GABA level variation with age focusing on the posterior cingulate cortex, which is the “core hub” of the default mode network. In this study, 14 monkeys between 4 and 21 years were recruited, and MEGA-PRESS MRS was performed to measure GABA levels, in order to explore a potential link between aging and GABA. Our results showed that a correlation between age and GABA+/Creatine ratio was at the edge of significance (r = −0.523, p = 0.081). There was also a near-significant trend between gray matter/white matter ratio and the GABA+/Creatine ratio (r = −0.518, p = 0.0848). Meanwhile, the correlation between age and grey matter showed no significance (r = −0.028, p = 0.93). Therefore, age and gray matter/white matter ratio account for different part of R-squared (adjusted R-squared = 0.5187) as independent variables for predicting GABA levels. Adjusted R-squared is about 0.5 for two independent variables. These findings suggest that there is internal neurochemical variation of GABA levels in the nonhuman primates associated with normal aging and structural brain decline. PMID:27660760

  2. Neurotransmitters as food supplements: the effects of GABA on brain and behavior.

    PubMed

    Boonstra, Evert; de Kleijn, Roy; Colzato, Lorenza S; Alkemade, Anneke; Forstmann, Birte U; Nieuwenhuis, Sander

    2015-01-01

    Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the human cortex. The food supplement version of GABA is widely available online. Although many consumers claim that they experience benefits from the use of these products, it is unclear whether these supplements confer benefits beyond a placebo effect. Currently, the mechanism of action behind these products is unknown. It has long been thought that GABA is unable to cross the blood-brain barrier (BBB), but the studies that have assessed this issue are often contradictory and range widely in their employed methods. Accordingly, future research needs to establish the effects of oral GABA administration on GABA levels in the human brain, for example using magnetic resonance spectroscopy. There is some evidence in favor of a calming effect of GABA food supplements, but most of this evidence was reported by researchers with a potential conflict of interest. We suggest that any veridical effects of GABA food supplements on brain and cognition might be exerted through BBB passage or, more indirectly, via an effect on the enteric nervous system. We conclude that the mechanism of action of GABA food supplements is far from clear, and that further work is needed to establish the behavioral effects of GABA.

  3. Excitatory actions of GABA in the intact neonatal rodent hippocampus in vitro

    PubMed Central

    Valeeva, Guzel; Valiullina, Fliza; Khazipov, Roustem

    2013-01-01

    The excitatory action of gamma-aminobutyric acid (GABA) is considered to be a hallmark of the developing nervous system. However, in immature brain slices, excitatory GABA actions may be secondary to neuronal injury during slice preparation. Here, we explored GABA actions in the rodent intact hippocampal preparations and at different depths of hippocampal slices during the early post-natal period [post-natal days (P) 1–7]. We found that in the intact hippocampus at P1–3: (i) GABA exerts depolarizing action as seen in cell-attached single GABA(A) channel recordings; (ii) GABA(A) receptor (GABA(A)-R) agonist isoguvacine and synaptic activation of the GABA(A)-Rs increase the frequency of multiple unit activity and the frequency of the network-driven giant depolarizing potentials (GDPs); and that (iii) Na+–K+–2Cl- cotransporter (NKCC1) antagonist bumetanide suppresses GDPs and the excitatory actions of isoguvacine. In the hippocampal slices at P2–5, isoguvacine and synaptic activation of GABA(A)-Rs-evoked excitatory responses at all slice depths, including surface and core. Thus, GABA exerts excitatory actions in the intact hippocampus (P1–3) and at all depths of hippocampal slices (P2–5). Therefore, the excitatory actions of GABA in hippocampal slices during the first post-natal days are not due to neuronal injury during slice preparation, and the trauma-related excitatory GABA actions at the slice surface are a fundamentally different phenomenon observed during the second post-natal week. PMID:23467988

  4. Amiloride and GMQ Allosteric Modulation of the GABA-A ρ1 Receptor: Influences of the Intersubunit Site

    PubMed Central

    Snell, Heather D.

    2015-01-01

    Amiloride, a diuretic used in the treatment of hypertension and congestive heart failure, and 2-guanidine-4-methylquinazoline (GMQ) are guanidine compounds that modulate acid-sensing ion channels. Both compounds have demonstrated affinity for a variety of membrane proteins, including members of the Cys-loop family of ligand-gated ion channels, such as the heteromeric GABA-A αβγ receptors. The actions of these guanidine compounds on the homomeric GABA-A ρ1 receptor remains unclear, especially in light of how many GABA-A αβγ receptor modulators have different effects in the GABA-A ρ1 receptors. We sought to characterize the influence of amiloride and GMQ on the human GABA-A ρ1 receptors using whole-cell patch-clamp electrophysiology. The diuretic amiloride potentiated the human GABA-A ρ1 GABA-mediated current, whereas GMQ antagonized the receptor. Furthermore, a GABA-A second transmembrane domain site, the intersubunit site, responsible for allosteric modulation in the heteromeric GABA-A receptors mediated amiloride’s positive allosteric actions. In contrast, the mutation did not remove GMQ antagonism but only changed the guanidine compound’s potency within the human GABA-A ρ1 receptor. Through modeling and introduction of point mutations, we propose that the GABA-A ρ1 intersubunit site plays a role in mediating the allosteric effects of amiloride and GMQ. PMID:25829529

  5. Amiloride and GMQ Allosteric Modulation of the GABA-A ρ1 Receptor: Influences of the Intersubunit Site.

    PubMed

    Snell, Heather D; Gonzales, Eric B

    2015-06-01

    Amiloride, a diuretic used in the treatment of hypertension and congestive heart failure, and 2-guanidine-4-methylquinazoline (GMQ) are guanidine compounds that modulate acid-sensing ion channels. Both compounds have demonstrated affinity for a variety of membrane proteins, including members of the Cys-loop family of ligand-gated ion channels, such as the heteromeric GABA-A αβγ receptors. The actions of these guanidine compounds on the homomeric GABA-A ρ1 receptor remains unclear, especially in light of how many GABA-A αβγ receptor modulators have different effects in the GABA-A ρ1 receptors. We sought to characterize the influence of amiloride and GMQ on the human GABA-A ρ1 receptors using whole-cell patch-clamp electrophysiology. The diuretic amiloride potentiated the human GABA-A ρ1 GABA-mediated current, whereas GMQ antagonized the receptor. Furthermore, a GABA-A second transmembrane domain site, the intersubunit site, responsible for allosteric modulation in the heteromeric GABA-A receptors mediated amiloride's positive allosteric actions. In contrast, the mutation did not remove GMQ antagonism but only changed the guanidine compound's potency within the human GABA-A ρ1 receptor. Through modeling and introduction of point mutations, we propose that the GABA-A ρ1 intersubunit site plays a role in mediating the allosteric effects of amiloride and GMQ.

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

    PubMed

    Raccuglia, Davide; Mueller, Uli

    2013-07-16

    Throughout the animal kingdom, the inhibitory neurotransmitter γ-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.

  7. Immature Responses to GABA in Fragile X Neurons Derived from Human Embryonic Stem Cells

    PubMed Central

    Telias, Michael; Segal, Menahem; Ben-Yosef, Dalit

    2016-01-01

    Fragile X Syndrome (FXS) is the most common form of inherited cognitive disability. However, functional deficiencies in FX neurons have been described so far almost exclusively in animal models. In a recent study we found several functional deficits in FX neurons differentiated in-vitro from human embryonic stem cells (hESCs), including their inability to fire repetitive action potentials, and their lack of synaptic activity. Here, we investigated the responses of such neurons to pulse application of the neurotransmitter GABA. We found two distinct types of responses to GABA and sensitivity to the GABA-A receptor antagonist bicuculline; type 1 (mature) characterized by non-desensitized responses to GABA as well as a high sensitivity to bicuculline, and type 2 (immature) which are desensitized to GABA and insensitive to bicuculline. Type 1 responses were age-dependent and dominant in mature WT neurons. In contrast, FX neurons expressed primarily type 2 phenotype. Expression analysis of GABA-A receptor subunits demonstrated that this bias in human FX neurons was associated with a significant alteration in the expression pattern of the GABA-A receptor subunits α2 and β2. Our results indicate that FMRP may play a role in the development of the GABAergic synapse during neurogenesis. This is the first demonstration of the lack of a mature response to GABA in human FX neurons and may explain the inappropriate synaptic functions in FXS. PMID:27242433

  8. Potentiation of the ionotropic GABA receptor response by whiskey fragrance.

    PubMed

    Hossain, Sheikh Julfikar; Aoshima, Hitoshi; Koda, Hirofumi; Kiso, Yoshinobu

    2002-11-06

    It is well-known that the target of most mood-defining compounds is an ionotropic gamma-aminobutyric acid receptor (GABA(A) receptor). The potentiation of the response of these inhibitory neurotransmitter receptors induces anxiolytic, sedative, and anesthetic activity in the human brain. To study the effects of whiskey fragrance on the GABA(A) receptor-mediated response, GABA(A) receptors were expressed in Xenopus oocyte by injecting rat whole brain mRNA or cRNA prepared from the cloned cDNA for the alpha(1) and beta(1) subunits of the bovine receptors. Most whiskey components such as phenol, ethoxy, and lactone derivatives potentiated the electrical responses of GABA(A) receptors, especially ethyl phenylpropanoate (EPP), which strongly potentiated the response. When this compound was applied to mice through respiration, the convulsions induced by pentetrazole were delayed, suggesting that EPP was absorbed by the brain, where it could potentiate the GABA(A) receptor responses. The extract of other alcoholic drinks such as wine, sake, brandy, and shochu also potentiated the responses to varying degrees. Although these fragrant components are present in alcoholic drinks at low concentrations (extremely small quantities compared with ethanol), they may also modulate the mood or consciousness of the human through the potentiation of the GABA(A) receptor response after absorption into the brain, because these hydrophobic fragrant compounds are easily absorbed into the brain through the blood-brain barrier and are several thousands times as potent as ethanol in the potentiation of the GABA(A) receptor-mediated response.

  9. Manganese exposure alters extracellular GABA, GABA receptor and transporter protein and mRNA levels in the developing rat brain.

    PubMed

    Anderson, Joel G; Fordahl, Steve C; Cooney, Paula T; Weaver, Tara L; Colyer, Christa L; Erikson, Keith M

    2008-11-01

    Unlike other essential trace elements (e.g., zinc and iron) it is the toxicity of manganese (Mn) that is more common in human populations than its deficiency. Data suggest alterations in dopamine biology may drive the effects associated with Mn neurotoxicity, though recently gamma-aminobutyric acid (GABA) has been implicated. In addition, iron deficiency (ID), a common nutritional problem, may cause disturbances in neurochemistry by facilitating accumulation of Mn in the brain. Previous data from our lab have shown decreased brain tissue levels of GABA as well as decreased (3)H-GABA uptake in synaptosomes as a result of Mn exposure and ID. These results indicate a possible increase in the concentration of extracellular GABA due to alterations in expression of GABA transport and receptor proteins. In this study weanling-male Sprague-Dawley rats were randomly placed into one of four dietary treatment groups: control (CN; 35mg Fe/kg diet), iron-deficient (ID; 6mg Fe/kg diet), CN with Mn supplementation (via the drinking water; 1g Mn/l) (CNMn), and ID with Mn supplementation (IDMn). Using in vivo microdialysis, an increase in extracellular GABA concentrations in the striatum was observed in response to Mn exposure and ID although correlational analysis reveals that extracellular GABA is related more to extracellular iron levels and not Mn. A diverse effect of Mn exposure and ID was observed in the regions examined via Western blot and RT-PCR analysis, with effects on mRNA and protein expression of GAT-1, GABA(A), and GABA(B) differing between and within the regions examined. For example, Mn exposure reduced GAT-1 protein expression by approximately 50% in the substantia nigra, while increasing mRNA expression approximately four-fold, while in the caudate putamen mRNA expression was decreased with no effect on protein expression. These data suggest that Mn exposure results in an increase in extracellular GABA concentrations via altered expression of transport and

  10. Localization of two major GABA(A) receptor subunits in the dentate gyrus of the rat and cell type-specific up-regulation following entorhinal cortex lesion.

    PubMed

    Simbürger, E; Plaschke, M; Fritschy, J M; Nitsch, R

    2001-01-01

    GABA(A) receptor subunits show a specific regional distribution in the CNS during development and in the adult animal. In the hippocampal formation, individual subsets of GABAergic interneurons are highly immunoreactive for the alpha1-subunit, whereas granule and pyramidal cells show a strong expression of the alpha2-subunit. Using confocal microscopy and digital image analysis, we demonstrate that in the dentate gyrus the alpha1-subunit immunolabeling appears in differently sized clusters. The large clusters, which are confined to dendrites of interneurons, show no alpha2 labeling, whereas the smaller ones coincide with alpha2-subunit-positive clusters. In the molecular layer, the clusters of both alpha-subunits co-localize with the anchoring protein gephyrin. In the granule cell layer and hilus, we found alpha1- and alpha2-subunit-positive clusters which were devoid of gephyrin labeling. Lesions of the medial entorhinal cortex led to the deafferentation of dendrites in the middle molecular layer of the dentate gyrus. This resulted in a significantly increased concentration of alpha2-subunit-positive clusters. We also observed an increase of alpha1-subunit immunolabeling in the deafferented area. We found no change in the co-localization between alpha1 and alpha2, and no significant change in the number of large alpha1-positive clusters along individual dendritic segments of interneurons. In a previous study, we demonstrated that calbindin-immunoreactive dendrites of granule cells revealed a significant increase in gephyrin immunoreactivity following lesion, whereas parvalbumin-positive dendrites showed no such alterations. The predominant localization of small gephyrin clusters in dendrites of granule cells, which was also described in this study, leads to the conclusion that the increase of the alpha2-subunit-positive clusters, demonstrated in the present study, indicates that, following entorhinal cortex lesion, new GABAergic synapses may be formed and that

  11. Gamma-aminobutyric acid depletion affects stomata closure and drought tolerance of Arabidopsis thaliana.

    PubMed

    Mekonnen, Dereje Worku; Flügge, Ulf-Ingo; Ludewig, Frank

    2016-04-01

    A rapid accumulation of γ-aminobutyric acid (GABA) during biotic and abiotic stresses is well documented. However, the specificity of the response and the primary role of GABA under such stress conditions are hardly understood. To address these questions, we investigated the response of the GABA-depleted gad1/2 mutant to drought stress. GABA is primarily synthesized from the decarboxylation of glutamate by glutamate decarboxylase (GAD) which exists in five copies in the genome of Arabidopsis thaliana. However, only GAD1 and GAD2 are abundantly expressed, and knockout of these two copies dramatically reduced the GABA content. Phenotypic analysis revealed a reduced shoot growth of the gad1/2 mutant. Furthermore, the gad1/2 mutant was wilted earlier than the wild type following a prolonged drought stress treatment. The early-wilting phenotype was due to an increase in stomata aperture and a defect in stomata closure. The increase in stomata aperture contributed to higher stomatal conductance. The drought oversensitive phenotype of the gad1/2 mutant was reversed by functional complementation that increases GABA level in leaves. The functionally complemented gad1/2 x pop2 triple mutant contained more GABA than the wild type. Our findings suggest that GABA accumulation during drought is a stress-specific response and its accumulation induces the regulation of stomatal opening thereby prevents loss of water.

  12. Role of proline and GABA in sexual reproduction of angiosperms

    PubMed Central

    Biancucci, Marco; Mattioli, Roberto; Forlani, Giuseppe; Funck, Dietmar; Costantino, Paolo; Trovato, Maurizio

    2015-01-01

    Two glutamate derivatives, proline and γ-aminobutyric acid (GABA), appear to play pivotal roles in different aspects of sexual reproduction in angiosperms, although their precise function in plant reproduction and the molecular basis of their action are not yet fully understood. Proline and GABA have long been regarded as pivotal amino acids in pollen vitality and fertility. Proline may constitute up to 70% of the free amino acid pool in pollen grains and it has been recently shown that Arabidopsis mutants affected in the first and rate-limiting step in proline synthesis produce aberrant and infertile pollen grains, indicating that proline synthesis is required for pollen development and fertility. Concerning GABA, a large body of evidence points to this glutamate derivative as a key determinant of post-pollination fertilization. Intriguingly, proline has also been associated with pollination, another aspect of sexual reproduction, since honeybees were reported to show a strong preference for proline-enriched nectars. In this review, we survey current knowledge on the roles of proline and GABA in plant fertility, and discuss future perspectives potentially capable to improve our understanding on the functions of these amino acids in pollen development, pollination, and pollen tube guidance. PMID:26388884

  13. gamma-Hydroxybutyrate (GHB) induces GABA(B) receptor independent intracellular Ca2+ transients in astrocytes, but has no effect on GHB or GABA(B) receptors of medium spiny neurons in the nucleus accumbens.

    PubMed

    Molnár, T; Antal, K; Nyitrai, G; Emri, Z

    2009-08-18

    We report on cellular actions of the illicit recreational drug gamma-hydroxybutyrate (GHB) in the brain reward area nucleus accumbens. First, we compared the effects of GHB and the GABA(B) receptor agonist baclofen. Neither of them affected the membrane currents of medium spiny neurons in rat nucleus accumbens slices. GABAergic and glutamatergic synaptic potentials of medium spiny neurons, however, were reduced by baclofen but not GHB. These results indicate the lack of GHB as well as postsynaptic GABA(B) receptors, and the presence of GHB insensitive presynaptic GABA(B) receptors in medium spiny neurons. In astrocytes GHB induced intracellular Ca(2+) transients, preserved in slices from GABA(B) receptor type 1 subunit knockout mice. The effects of tetrodotoxin, zero added Ca(2+) with/without intracellular Ca(2+) store depletor cyclopiazonic acid or vacuolar H-ATPase inhibitor bafilomycin A1 indicate that GHB-evoked Ca(2+) transients depend on external Ca(2+) and intracellular Ca(2+) stores, but not on vesicular transmitter release. GHB-induced astrocytic Ca(2+) transients were not affected by the GHB receptor-specific antagonist NCS-382, suggesting the presence of a novel NCS-382-insensitive target for GHB in astrocytes. The activation of astrocytes by GHB implies their involvement in physiological actions of GHB. Our findings disclose a novel profile of GHB action in the nucleus accumbens. Here, unlike in other brain areas, GHB does not act on GABA(B) receptors, but activates an NCS-382 insensitive GHB-specific target in a subpopulation of astrocytes. The lack of either post- or presynaptic effects on medium spiny neurons in the nucleus accumbens distinguishes GHB from many drugs and natural rewards with addictive properties and might explain why GHB has only a weak reinforcing capacity.

  14. Inhibition of GABA uptake potentiates the conductance increase produced by GABA-mimetic compounds on single neurones in isolated olfactory cortex slices of the guinea-pig.

    PubMed

    Brown, D A; Scholfield, C N

    1984-09-01

    Membrane potential and input conductance were recorded in single neurones in slices of guinea-pig olfactory cortex in vitro. gamma-Aminobutyric acid (GABA) and GABA-mimetic compounds were applied by bath-perfusion. Potency was measured as the concentration required to double the input conductance. The potency of GABA was increased (i.e. the equi-effective concentrations were reduced) by 15.5 +/- 2.3 times (mean +/- s.e. mean) on reducing external [Na+] from 144 to 20 mmol l-1, by replacement with Mg2+. Corresponding potency changes for other agonists were + 10.8 +/- 2.5 for 3-aminopropanesulphonic acid (3-APS); 3.25 +/- 1.06 for isoguvacine and 2.43 +/- 0.69 for muscimol. Nipecotic acid (0.5 mM) produced the following increases in potency: GABA 2.68 +/- 0.02; 3-aminopropanesulphonic acid, 3.11 +/- 0.07; isoguvacine, 1.92 +/- 0.34; muscimol, 2.24 +/- 0.17. The concentration of GABA in the bathing fluid necessary to double input conductance increased with increasing depth of the recording site from the cut surface. The apparent potency fell 10 times for each 60 micron depth increment up to 150 micron. The recording depth also affected the apparent potency of muscimol and 3-APS but to a lesser extent. Reduction of external [Na+] reduced the depth-dependence of both GABA and 3-APS potency. No clear change in the duration of the recurrent inhibitory postsynaptic conductance could be detected in the presence of 0.5 mmol l-1 nipecotic acid. 6 It is suggested that agonist uptake by a Na+-dependent, nipecotic acid-sensitive mechanism severely attenuates the responses of olfactory neurones to exogenous GABA and to its analogues 3-APS, muscimol and isoguvacine, but has little immediate influence on the duration of the GABA-mediated inhibitory postsynaptic conductance.

  15. Hyperpolarizing inhibition develops without trophic support by GABA in cultured rat midbrain neurons.

    PubMed

    Titz, Stefan; Hans, Michael; Kelsch, Wolfgang; Lewen, Andrea; Swandulla, Dieter; Misgeld, Ulrich

    2003-08-01

    During a limited period of early neuronal development, GABA is depolarizing and elevates [Ca2+]i, which mediates the trophic action of GABA in neuronal maturation. We tested the attractive hypothesis that GABA itself promotes the developmental change of its response from depolarizing to hyperpolarizing (Ganguly et al. 2001). In cultured midbrain neurons we found that the GABA response changed from depolarizing to hyperpolarizing, although GABAA receptors had been blocked throughout development. In immature neurons prolonged exposure of the cells to nanomolar concentrations of GABA or brief repetitive applications of GABA strongly diminished the elevation of [Ca+]i by GABA. As revealed by gramicidin perforated-patch recording, reduced [Ca2+]i responses were due to a diminished driving force for Cl-. This suggests that immature neurons do not have an efficient inward transport that can compensate the loss of cytosolic Cl-resulting from sustained GABAA receptor activation by ambient GABA. Transient increases in external K+, which can induce voltage-dependent Cl- entry, restored GABA-induced [Ca2+]i elevations. In mature neurons, GABA reduced [Ca2+]i provided that background [Ca2+]i was elevated by the application of an L-type Ca2+ channel agonist. This was probably due to a hyperpolarization of the membrane by Cl- currents. K(+)-Cl- cotransport maintained the gradient for hyperpolarizing Cl-currents. We conclude that in immature midbrain neurons an inward Cl- transport is not effective although the GABA response is depolarizing. Further, GABA itself is not required for the developmental switch of GABAergic responses from depolarizing to hyperpolarizing in cultured midbrain neurons.

  16. Hyperpolarizing Inhibition Develops without Trophic support by GABA in Cultured Rat Midbrain Neurons

    PubMed Central

    Titz, Stefan; Hans, Michael; Kelsch, Wolfgang; Lewen, Andrea; Swandulla, Dieter; Misgeld, Ulrich

    2003-01-01

    During a limited period of early neuronal development, GABA is depolarizing and elevates [Ca2+]i, which mediates the trophic action of GABA in neuronal maturation. We tested the attractive hypothesis that GABA itself promotes the developmental change of its response from depolarizing to hyperpolarizing (Ganguly et al. 2001). In cultured midbrain neurons we found that the GABA response changed from depolarizing to hyperpolarizing, although GABAA receptors had been blocked throughout development. In immature neurons prolonged exposure of the cells to nanomolar concentrations of GABA or brief repetitive applications of GABA strongly diminished the elevation of [Ca2+]i by GABA. As revealed by gramicidin perforated-patch recording, reduced [Ca2+]i responses were due to a diminished driving force for Cl−. This suggests that immature neurons do not have an efficient inward transport that can compensate the loss of cytosolic Cl− resulting from sustained GABAA receptor activation by ambient GABA. Transient increases in external K+, which can induce voltage-dependent Cl− entry, restored GABA-induced [Ca2+]i elevations. In mature neurons, GABA reduced [Ca2+]i provided that background [Ca2+]i was elevated by the application of an L-type Ca2+ channel agonist. This was probably due to a hyperpolarization of the membrane by Cl− currents. K+-Cl− cotransport maintained the gradient for hyperpolarizing Cl− currents. We conclude that in immature midbrain neurons an inward Cl− transport is not effective although the GABA response is depolarizing. Further, GABA itself is not required for the developmental switch of GABAergic responses from depolarizing to hyperpolarizing in cultured midbrain neurons. PMID:12938674

  17. [GABA--the basic mediator of excitation in the early stages of hippocampal development].

    PubMed

    Khazipov, R N; Zefirov, A L; Ben-Ari, E

    1998-01-01

    GABA is the principal neurotransmitter of inhibition in the adult mammalian brain. However, at early stages of development, including embryonic period and first week of postnatal life, GABA plays the role of main neurotransmitter of excitation. The paradoxical excitatory effect of GABA is due to an inversed chloride gradient and therefore a depolarizing direction of GABA-A receptor mediated responses. In addition, another type of GABAergic inhibition mediated by postsynaptic GABA-B receptors is not functional at early stage of life. In the neonatal rat hippocampus, GABA, acting via GABA-A receptors, activates voltage gated sodium and calcium channels and potentiates the activity of NMDA receptors by reducing their voltage dependent Mg2+ block. The temporal window when GABA exerts excitatory actions coincides with a particular pattern of activity of hippocampal neuronal network that is characterized by periodical giant depolarizing potentials (GDPs) reminiscent of interictal-like epileptiform discharges. Recent studies have shown that GDPs result from the synchronous discharge of GABAergic interneurons and principal glutamatergic pyramidal cells and are mediated by the synergistic excitatory actions of GABA-A and glutamate receptors. GDPs provide synchronous intracellular Ca2+ oscillations and may therefore be implicated in hebbian modulation of developing synapses and activity-dependent formation of the hippocampal network.

  18. Actions of insecticides on the insect GABA receptor complex

    SciTech Connect

    Bermudez, I.; Hawkins, C.A.; Taylor, A.M.; Beadle, D.J. )

    1991-01-01

    The actions of insecticides on the insect gamma-aminobutyric acid (GABA) receptor were investigated using (35S)t-butylbicyclophosphorothionate (( 35S)TBPS) binding and voltage-clamp techniques. Specific binding of (35S)TBPS to a membrane homogenate derived from the brain of Locusta migratoria locusts is characterised by a Kd value of 79.3 {plus minus} 2.9 nM and a Bmax value of 1770 {plus minus} 40 fmol/mg protein. (35S)TBPS binding is inhibited by mM concentrations of barbiturates and benzodiazepines. In contrast dieldrin, ivermectin, lindane, picrotoxin and TBPS are inhibitors of (35S)TBPS binding at the nanomolar range. Bicuculline, baclofen and pyrethroid insecticides have no effect on (35S)TBPS binding. These results are similar to those obtained in electrophysiological studies of the current elicited by GABA in both Locusta and Periplaneta americana central neurones. Noise analysis of the effects of lindane, TBPS, dieldrin and picrotoxin on the cockroach GABA responses reveals that these compounds decrease the variance of the GABA-induced current but have no effect on its mean open time. All these compounds, with the exception of dieldrin, significantly decrease the conductance of GABA-evoked single current.

  19. Oncosecretomics coupled to bioenergetics identifies α-amino adipic acid, isoleucine and GABA as potential biomarkers of cancer: Differential expression of c-Myc, Oct1 and KLF4 coordinates metabolic changes.

    PubMed

    Bellance, Nadège; Pabst, Lisa; Allen, Genevara; Rossignol, Rodrigue; Nagrath, Deepak

    2012-11-01

    Bioenergetic profiling of tumors is a new challenge of cancer research and medicine as therapies are currently being developed. Meanwhile, methodological means must be proposed to gather information on tumor metabolism in order to adapt these potential therapies to the bioenergetic specificities of tumors. Studies performed on tumors and cancer cell lines have shown that cancer cells bioenergetics is highly variable. This profile changes with microenvironmental conditions (eg. substrate availability), the oncogenes activated (and the tumor suppressors inactivated) and the interaction with the stroma (i.e. reverse Warburg effect). Here, we assessed the power of metabolic footprinting (MFP) to unravel the bioenergetics and associated anabolic changes induced by three oncogenes, c-Myc, KLF4 and Oct1. The MFP approach provides a quantitative analysis of the metabolites secreted and consumed by cancer cells. We used ultra performance liquid chromatography for quantifying the amino acid uptake and secretion. To investigate the potential oncogene-mediated alterations in mitochondrial metabolism, we measured oxygen consumption rate and ATP production as well as the glucose uptake and lactate release. Our findings show that c-Myc deficiency initiates the Warburg effect along with a reduction of mitochondrial respiration. KLF4 deficiency also stimulated glycolysis, albeit without cellular respiration impairment. In contrast, Oct1 deficiency reduced glycolysis and enhanced oxidative phosphorylation efficiency. MFP revealed that c-Myc, KLF4 and Oct1 altered amino acid metabolism with specific patterns. We identified isoleucine, α-aminoadipic acid and GABA (γ-aminoisobutyric acid) as biomarkers related. Our findings establish the impact of Oct1, KLF4 and c-Myc on cancer bioenergetics and evidence a link between oncosecretomics and cellular bioenergetics profile.

  20. Daily changes of GABA and taurine concentrations in various hypothalamic areas are affected by chronic hyperprolactinemia.

    PubMed

    Duvilanski, Beatriz H; Alvarez, M Pilar; Castrillón, Patricia O; Cano, Pilar; Esquifino, Ana I

    2003-03-01

    This study was designed to characterize, in anterior, mediobasal, and posterior hypothalamic and median eminence, the 24h changes of gamma aminobutyric acid (GABA) and taurine (TAU) contents in adult male rats and to analyze whether chronic hyperprolactinemia may affect these patterns. Rats were turned hyperprolactinemic by a pituitary graft. Plasma prolactin (PRL) levels increased after pituitary grafting at all time points examined. A disruption of the circadian rhythm was observed in pituitary-grafted rats, whereas GABA and TAU content followed daily rhythms in all areas studied in controls. In the mediobasal hypothalamus, two peaks for each amino acid were found at midnight and midday. In the anterior hypothalamus, GABA and TAU showed only one peak of concentration at midnight. In the posterior hypothalamus, the values of both GABA and TAU were higher during the light as compared to the dark phase of the photoperiod. In the median eminence GABA content peaked at 20:00h, the time when TAU exhibited the lowest values. Hyperprolactinemia abolished the 24h changes of GABA in the mediobasal hypothalamus and reduced its content as compared to controls. Hyperprolactinemia advanced the diurnal peak of TAU to 12:00h in the mediobasal hypothalamus and did not modify the 24:00h peak. In the anterior hypothalamus, hyperprolactinemia increased GABA and TAU contents during the light phase while it decreased them during the dark phase of the photoperiod. In the posterior hypothalamus hyperprolactinemia did not modify GABA or TAU patterns as compared to controls. In the median eminence hyperprolactinemia increased the 20:00h peak of GABA and shift advanced the decrease in TAU content at 20:00h and its maximum at 24:00h as compared to controls. These data show that GABA and TAU content exhibit specific daily patterns in each hypothalamic region studied. PRL differentially affects the daily pattern of these amino acids in each hypothalamic region analyzed.

  1. Insect Herbivory-Elicited GABA Accumulation in Plants is a Wound-Induced, Direct, Systemic, and Jasmonate-Independent Defense Response

    PubMed Central

    Scholz, Sandra S.; Reichelt, Michael; Mekonnen, Dereje W.; Ludewig, Frank; Mithöfer, Axel

    2015-01-01

    The non-proteinogenic amino acid γ-aminobutyric acid (GABA) is present in all organisms analyzed so far. In invertebrates GABA acts as a neurotransmitter; in plants different functions are under discussion. Among others, its involvement in abiotic stress reactions and as a defensive compound against feeding insects is suggested. GABA is synthesized from glutamate by glutamate decarboxylases and degraded by GABA-transaminases. Here, in Arabidopsis thaliana, gad1/2 double mutants showing reduced GABA concentrations as well as GABA-enriched triple mutants (gad1/2 x pop2-5) were generated and employed for a systematic study of GABA induction, accumulation and related effects in Arabidopsis leaves upon herbivory. The results demonstrate that GABA accumulation is stimulated by insect feeding-like wounding by a robotic caterpillar, MecWorm, as well as by real insect (Spodoptera littoralis) herbivory. Higher GABA levels in both plant tissue and artificial dietary supplements in turn affect the performance of feeding larvae. GABA enrichment occurs not only in the challenged but also in adjacent leaf. This induced response is neither dependent on herbivore defense-related phytohormones, jasmonates, nor is jasmonate induction dependent on the presence of GABA. Thus, in Arabidopsis the rapid accumulation of GABA very likely represents a general, direct and systemic defense reaction against insect herbivores. PMID:26734035

  2. Excitatory Synaptic Responses Mediated by GABA_A Receptors in the Hippocampus

    NASA Astrophysics Data System (ADS)

    Michelson, Hillary B.; Wong, Robert K. S.

    1991-09-01

    Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the cortex. Activation of postsynaptic GABA_A receptors hyperpolarizes cells and inhibits neuronal activity. Synaptic responses mediated by GABA_A receptors also strongly excited hippocampal neurons. This excitatory response was recorded in morphologically identified interneurons in the presence of 4-aminopyridine or after elevation of extracellular potassium concentrations. The synaptic excitation sustained by GABA_A receptors synchronized the activity of inhibitory interneurons. This synchronized discharge of interneurons in turn elicited large-amplitude inhibitory postsynaptic potentials in pyramidal and granule cells. Excitatory synaptic responses mediated by GABA_A receptors may thus provide a mechanism for the recruitment of GABAergic interneurons through their recurrent connections.

  3. On the origin of extracellular GABA collected by brain microdialysis and assayed by a simplified on-line method.

    PubMed

    Westerink, B H; de Vries, J B

    1989-06-01

    The present study describes a simplified on-line system for determination of GABA in brain dialysates. GABA was determined with an isocratic HPLC method after derivatization with o-phthaldialdehyde. One peristaltic pump was sufficient to transport both the perfusion fluid and the derivatizing reagent. The basal release of GABA was stimulated by infusion with either elevated K+ or the GABA uptake inhibitor (-)-nipecotic acid. Basal as well as stimulated GABA release were investigated for possible calcium-dependency by infusing submmolar amounts of the potent calcium antagonist cadmium. Infusion of cadmium did not modify the dialysate concentrations of GABA. In addition basal as well as nipecotic acid enhanced release of GABA dialysate concentrations were investigated for nerve-impulse dependency by infusing mumolar amounts of tetrodotoxin. No change in the GABA output was observed during infusion of TTX. From these results it is concluded that the basal as well as the nipecotic acid induced release of GABA did not fulfill the criteria for classic exocytotic release. Possible explanations for these unexpected findings are discussed.

  4. Inhibitory effect of GABA on sympathetic neurotransmission in rabbit ear artery.

    PubMed

    Manzini, S; Maggi, C A; Meli, A

    1985-01-01

    GABA 100 microM inhibited neurogenic vasoconstrictor responses elicited in rabbit ear artery by field stimulation at various frequencies. GABA was ineffective both on resting tone and on noradrenaline (0.05-5 microM)- and high-K+ (24-54 mM)-induced tonic contraction. GABA effectiveness against field stimulation-induced vasoconstriction was inversely related to the frequency of stimulation. This action of GABA was mimicked by a selective GABAB agonist, such as baclofen (100 microM), but not by selective GABAA agonists as muscimol (100 microM) and homotaurine (100 microM). The selective GABAB antagonists 5-aminovaleric acid (1 mM) and homotaurine (100 microM) completely suppressed the inhibitory effect of GABA on field stimulation-induced vasoconstrictions. GABA action was partially reversed also by the selective GABAA antagonist picrotoxin (100 microM); however, this drug "per se" determined an increase in amplitude of field stimulation-induced contractions which in turn could have determined the minor effect of GABA. As a whole these data suggest that GABA can inhibit sympathetic neurotransmission in rabbit ear artery through the stimulation of a prejunctional receptor of the GABAB subtype.

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

    PubMed Central

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

    2013-01-01

    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

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

    SciTech Connect

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

    1987-07-27

    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.

  7. Cyclic AMP-dependent protein kinase phosphorylation facilitates GABA(B) receptor-effector coupling.

    PubMed

    Couve, A; Thomas, P; Calver, A R; Hirst, W D; Pangalos, M N; Walsh, F S; Smart, T G; Moss, S J

    2002-05-01

    GABA (gamma-aminobutyric acid)(B) receptors are heterodimeric G protein-coupled receptors that mediate slow synaptic inhibition in the central nervous system. Here we show that the functional coupling of GABA(B)R1/GABA(B)R2 receptors to inwardly rectifying K(+) channels rapidly desensitizes. This effect is alleviated after direct phosphorylation of a single serine residue (Ser892) in the cytoplasmic tail of GABA(B)R2 by cyclic AMP (cAMP)-dependent protein kinase (PKA). Basal phosphorylation of this residue is evident in rat brain membranes and in cultured neurons. Phosphorylation of Ser892 is modulated positively by pathways that elevate cAMP concentration, such as those involving forskolin and beta-adrenergic receptors. GABA(B) receptor agonists reduce receptor phosphorylation, which is consistent with PKA functioning in the control of GABA(B)-activated currents. Mechanistically, phosphorylation of Ser892 specifically enhances the membrane stability of GABA(B) receptors. We conclude that signaling pathways that activate PKA may have profound effects on GABA(B) receptor-mediated synaptic inhibition. These results also challenge the accepted view that phosphorylation is a universal negative modulator of G protein-coupled receptors.

  8. A molecular characterization of the agonist binding site of a nematode cys-loop GABA receptor

    PubMed Central

    Kaji, Mark D; Kwaka, Ariel; Callanan, Micah K; Nusrat, Humza; Desaulniers, Jean-Paul; Forrester, Sean G

    2015-01-01

    Background and Purpose Cys-loop GABA receptors represent important targets for human chemotherapeutics and insecticides and are potential targets for novel anthelmintics (nematicides). However, compared with insect and mammalian receptors, little is known regarding the pharmacological characteristics of nematode Cys-loop GABA receptors. Here we have investigated the agonist binding site of the Cys-loop GABA receptor UNC-49 (Hco-UNC-49) from the parasitic nematode Haemonchus contortus. Experimental Approach We used two-electrode voltage-clamp electrophysiology to measure channel activation by classical GABA receptor agonists on Hco-UNC-49 expressed in Xenopus laevis oocytes, along with site-directed mutagenesis and in silico homology modelling. Key Results The sulphonated molecules P4S and taurine had no effect on Hco-UNC-49. Other classical Cys-loop GABAA receptor agonists tested on the Hco-UNC-49B/C heteromeric channel had a rank order efficacy of GABA > trans-4-aminocrotonic acid > isoguvacine > imidazole-4-acetic acid (IMA) > (R)-(−)-4-amino-3-hydroxybutyric acid [R(−)-GABOB] > (S)-(+)-4-amino-3-hydroxybutyric acid [S(+)-GABOB] > guanidinoacetic acid > isonipecotic acid > 5-aminovaleric acid (DAVA) (partial agonist) > β-alanine (partial agonist). In silico ligand docking revealed some variation in binding between agonists. Mutagenesis of a key serine residue in binding loop C to threonine had minimal effects on GABA and IMA but significantly increased the maximal response to DAVA and decreased twofold the EC50 for R(−)- and S(+)-GABOB. Conclusions and Implications The pharmacological profile of Hco-UNC-49 differed from that of vertebrate Cys-loop GABA receptors and insect resistance to dieldrin receptors, suggesting differences in the agonist binding pocket. These findings could be exploited to develop new drugs that specifically target GABA receptors of parasitic nematodes. PMID:25850584

  9. The GABA agonist THIP a muscimol analogue, does not interfere with the benzodiazepine binding site on rats cortical membranes.

    PubMed

    Maurer, R

    1979-04-01

    THIP, a cyclic analogue of muscimol, is a powerful GABA agonist. It is as active as GABA in displacing [3H]muscimol from its binding site to cerebellar membranes (IC50 = 31.5 +/- 2.5 mM). However, unlike muscimol or GABA, it is devoid of any modulatory interaction with the benzodiazepine binding site on rat's cortical membranes. Homotaurine, isoguvacine and imidazole acetic acid are less active than muscimol and GABA for increasing the affinity of [3H]diazepam to cortical membrane preparations.

  10. GABA application to hippocampal CA3 or CA1 stratum lacunosum-moleculare excites an interneuron network.

    PubMed

    Perkins, Katherine L

    2002-03-01

    Whole cell voltage-clamp recording and focal application of the neurotransmitter gamma-aminobutyric acid (GABA) were used to investigate the ability of exogenous GABA applied to different locations within the guinea pig hippocampal slice to trigger a giant GABA-mediated postsynaptic current (GPSC) in pyramidal cells. A GPSC reflects the synchronous release of GABA from a group of interneurons. Recordings were done in the presence of 4-aminopyridine (4-AP) and blockers of ionotropic glutamatergic synaptic transmission. Spontaneous GPSCs occurred rhythmically in pyramidal cells under these conditions. Brief focal pressure application of GABA (500 microM; 30-200 ms) to CA3 stratum lacunosum-moleculare (SLM) or to the border between CA3 s. radiatum (SR) and SLM triggered an "all-or-none" GPSC in CA3 and CA1 pyramidal cells that looked like the spontaneous GPSCs. During the refractory period following a spontaneous GPSC, application of GABA could not trigger a GPSC. Both spontaneous GPSCs and GPSCs triggered by exogenous GABA were blocked by suppressing synaptic transmission with high Mg(2+)/low Ca(2+) bath solution. On the other hand, focal application of GABA to CA3 s. oriens (SO) or to proximal SR did not trigger a GPSC in the CA3 pyramidal cell; instead it produced a graded response. Focal application of GABA to regions other than CA3 was also tested. Focal application of GABA to CA1 SLM always triggered a GPSC in the CA3 pyramidal cell. Focal application of GABA within the outer two-thirds of the dentate molecular layer often elicited a GPSC in the CA3 pyramidal cell. In contrast, focal application of GABA to CA1 SO, to CA1 SR, or to the hilus elicited no current response in the CA3 pyramidal cell. These data indicate that the GPSC recorded in pyramidal cells that was triggered by focal GABA application resulted from the synchronous synaptic release of GABA from activated interneurons rather than from the binding of exogenous GABA to receptors on the pyramidal cell

  11. GABA Production in Lactococcus lactis Is Enhanced by Arginine and Co-addition of Malate

    PubMed Central

    Laroute, Valérie; Yasaro, Chonthicha; Narin, Waranya; Mazzoli, Roberto; Pessione, Enrica; Cocaign-Bousquet, Muriel; Loubière, Pascal

    2016-01-01

    Lactococcus lactis NCDO 2118 was previously selected for its ability to decarboxylate glutamate to γ-aminobutyric acid (GABA), an interesting nutritional supplement able to improve mood and relaxation. Amino acid decarboxylation is generally considered as among the biochemical systems allowing lactic acid bacteria to counteracting acidic stress and obtaining metabolic energy. These strategies also include arginine deiminase pathway and malolactic fermentation but little is known about their possible interactions of with GABA production. In the present study, the effects of glutamate, arginine, and malate (i.e., the substrates of these acid-resistance pathways) on L. lactis NCDO 2118 growth and GABA production performances were analyzed. Both malate and arginine supplementation resulted in an efficient reduction of acidity and improvement of bacterial biomass compared to glutamate supplementation. Glutamate decarboxylation was limited to narrow environmental conditions (pH < 5.1) and physiological state (stationary phase). However, some conditions were able to improve GABA production or activate glutamate decarboxylation system even outside of this compass. Arginine clearly stimulated glutamate decarboxylation: the highest GABA production (8.6 mM) was observed in cultures supplemented with both arginine and glutamate. The simultaneous addition of arginine, malate, and glutamate enabled earlier GABA production (i.e., during exponential growth) at relatively high pH (6.5). As far as we know, no previous study has reported GABA production in such conditions. Although further studies are needed to understand the molecular basis of these phenomena, these results represent important keys suitable of application in GABA production processes. PMID:27458444

  12. Amino acid residues involved in the substrate specificity of TauT/SLC6A6 for taurine and γ-aminobutyric acid.

    PubMed

    Yahara, Tohru; Tachikawa, Masanori; Akanuma, Shin-ichi; Kubo, Yoshiyuki; Hosoya, Ken-ichi

    2014-01-01

    Taurine transporter (TauT/SLC6A6) is an "honorary" γ-aminobutyric acid (GABA) transporter because of its low affinity for GABA. The sequence analysis of TauT implied the role of Gly57, Phe58, Leu306 and Glu406 in the substrate recognition of TauT, and amino acid-substitutions were performed. Immunocytochemistry supported no marked effect of mutations on the expression of TauT. TauT-expressing oocytes showed a reduction in [(3)H]taurine uptake by G57E, F58I, L306Q and E406C, and change in [(3)H]GABA uptake by G57E and E406C, suggesting their significant roles in the function of TauT. G57E lost the activity of [(3)H]taurine and [(3)H]GABA uptake, suggesting that Gly57 is involved in the determination of substrate pocket volume and in the interaction with substrates. E406C exhibited a decrease and an increase in the affinity for taurine and GABA, respectively, suggesting the involvement of Glu406 in the substrate specificity of TauT. The inhibition study supported the role of Glu406 in the substrate specificity since [(3)H]taurine and [(3)H]GABA uptake by E406C was less sensitive to taurine and β-alanine, and more sensitive to GABA and nipecotic acid than was the case with wild type of TauT. F58I had an increased affinity for GABA, suggesting the involvement of Phe58 in the substrate accessibility. The kinetic parameters showed the decreased and increased affinities of L306Q for taurine and GABA, respectively, supporting that substrate recognition of TauT is conformationally regulated by the branched-side chain of Leu306. In conclusion, the present results suggest that these residues play important roles in the transport function and substrate specificity of TauT.

  13. Modulation of GABA-A receptors of astrocytes and STC-1 cells by taurine structural analogs.

    PubMed

    Reyes-Haro, Daniel; Cabrera-Ruíz, Elizabeth; Estrada-Mondragón, Argel; Miledi, Ricardo; Martínez-Torres, Ataúlfo

    2014-11-01

    Taurine activates and modulates GABA receptors in vivo as well as those expressed in heterologous systems. This study aimed to determine whether the structural analogs of taurine: homotaurine and hypotaurine, have the ability to activate GABA-A receptors that include GABAρ subunits. The expression of GABA-A receptors containing GABAρ has been reported in the STC-1 cells and astrocytes. In both cell types, taurine, homo-, and hypotaurine gated with low efficiency a picrotoxin-sensitive GABA-A receptor. The known bimodal modulatory effect of taurine on GABAρ receptors was not observed; however, differences between the activation and deactivation rates were detected when they were perfused together with GABA. In silico docking simulations suggested that taurine, hypo-, and homotaurine do not form a cation-π interaction such as that generated by GABA in the agonist-binding site of GABAρ. This observation complements the electrophysiological data suggesting that taurine and its analogs act as partial agonists of GABA-A receptors. All the observations above suggest that the structural analogs of taurine are partial agonists of GABA-A receptors that occupy the agonist-binding site, but their structures do not allow the proper interaction with the receptor to fully gate its Cl(-) channel.

  14. Cadmium exposure disrupts GABA and taurine regulation of prolactin secretion in adult male rats.

    PubMed

    Caride, A; Fernández-Pérez, B; Cabaleiro, T; Esquifino, A I; Lafuente, A

    2009-03-28

    This work was undertaken to evaluate the possible effects of cadmium exposure on 24 h changes of gamma-aminobutyric acid (GABA) and taurine median eminence and pituitary contents. Also the possible alterations of the regulatory mechanisms of GABA and taurine on prolactin secretion were evaluated. Adult male rats were given cadmium at a dose of 25 mg/l of cadmium chloride in the drinking water for 30 days. Control age-matched rats received cadmium free water. Metal exposure induced the appearance of a maximal value of prolactin at 08:00 h. In median eminence, cadmium abolished the GABA and taurine maximal values and decreased GABA and taurine mean levels. In the anterior pituitary, cadmium treatment phase advanced 12 h the peak observed in controls at 00:00 h for both amino acids. There was a positive correlation between GABA and taurine contents in median eminence and the anterior pituitary in both control and cadmium-exposed animals. However, the correlation between GABA or/and taurine with prolactin levels disappeared in cadmium-exposed animals. These results suggest that cadmium exposure affects GABA and taurine daily pattern in the median eminence and anterior pituitary, and those changes explain, at least in part, the modification in the regulatory pattern of prolactin secretion.

  15. GABA production and structure of gadB/gadC genes in Lactobacillus and Bifidobacterium strains from human microbiota.

    PubMed

    Yunes, R A; Poluektova, E U; Dyachkova, M S; Klimina, K M; Kovtun, A S; Averina, O V; Orlova, V S; Danilenko, V N

    2016-12-01

    Gamma-amino butyric acid (GABA) is an active biogenic substance synthesized in plants, fungi, vertebrate animals and bacteria. Lactic acid bacteria are considered the main producers of GABA among bacteria. GABA-producing lactobacilli are isolated from food products such as cheese, yogurt, sourdough, etc. and are the source of bioactive properties assigned to those foods. The ability of human-derived lactobacilli and bifidobacteria to synthesize GABA remains poorly characterized. In this paper, we screened our collection of 135 human-derived Lactobacillus and Bifidobacterium strains for their ability to produce GABA from its precursor monosodium glutamate. Fifty eight strains were able to produce GABA. The most efficient GABA-producers were Bifidobacterium strains (up to 6 g/L). Time profiles of cell growth and GABA production as well as the influence of pyridoxal phosphate on GABA production were studied for L. plantarum 90sk, L. brevis 15f, B. adolescentis 150 and B. angulatum GT102. DNA of these strains was sequenced; the gadB and gadC genes were identified. The presence of these genes was analyzed in 14 metagenomes of healthy individuals. The genes were found in the following genera of bacteria: Bacteroidetes (Bacteroides, Parabacteroides, Alistipes, Odoribacter, Prevotella), Proteobacterium (Esherichia), Firmicutes (Enterococcus), Actinobacteria (Bifidobacterium). These data indicate that gad genes as well as the ability to produce GABA are widely distributed among lactobacilli and bifidobacteria (mainly in L. plantarum, L. brevis, B. adolescentis, B. angulatum, B. dentium) and other gut-derived bacterial species. Perhaps, GABA is involved in the interaction of gut microbiota with the macroorganism and the ability to synthesize GABA may be an important feature in the selection of bacterial strains - psychobiotics.

  16. Actions of picrodendrin antagonists on dieldrin-sensitive and -resistant Drosophila GABA receptors.

    PubMed Central

    Hosie, A. M.; Ozoe, Y.; Koike, K.; Ohmoto, T.; Nikaido, T.; Sattelle, D. B.

    1996-01-01

    1. A series of terpenoid compounds, recently isolated from Picrodendron baccatum, share a picrotoxane skeleton with picrotoxinin, an antagonist of ionotropic GABA receptors. Referred to as picrodendrins, they inhibit the binding of [35S]-tert-butylbicyclophosphorothionate (TBPS) to rat GABAA receptors. Hitherto, their effects on GABA receptors have not been investigated electrophysiologically. Under two-electrode voltage-clamp, the actions of picrodendrins and related terpenoids have been assayed on homooligomeric GABA receptors formed by the expression of a Drosophila GABA receptor subunit (RDLac) in Xenopus oocytes. 2. All the terpenoids tested, dose-dependently antagonized currents induced by 30 microM (EC50) GABA. 3. Tutin and its analogues (dihydrotutin and isohyenanchin) differ in the structure of their axial C4 substituents. Of these compounds, tutin, which bears an isopropenyl group at this carbon atom, was the most potent antagonist of RDLac homo-oligomers, whereas isohyenanchin, which bears a hydroxyisopropyl group, was the least potent antagonist tested. 4. Picrodendrins differ mainly in the structure of their C9 substituents. The IC50s of picrodendrins ranged from 17 +/- 1.3 nM (picrodendrin-Q) to 1006 +/- 1.3 nM (picrodendrin-O). As such, the most potent picrodendrins (Q, A and B) were approximately equipotent with picrotoxinin as antagonists of RDLac homo-oligomers. 5. Certain picrodendrin compounds effected a use-dependent blockade of RDLac homo-oligomers. Such a biphasic block was not observed with tutin analogues. 6. Picrotoxin-resistant RDLacA3025 homo-oligomers, which have a single amino acid substitution (A302S) in the 2nd transmembrane region, were markedly less sensitive to picrodendrin-O than the wild-type, dieldrin-sensitive, homo-oligomers. 7. The relative potency of tutin analogues demonstrates that the structure-activity relationship of the C4 substituent of picrotoxane-based compounds is conserved in vertebrates and insects. However, the

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

    ERIC Educational Resources Information Center

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

    2007-01-01

    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…

  18. Focal Uncaging of GABA Reveals a Temporally Defined Role for GABAergic Inhibition during Appetitive Associative Olfactory Conditioning in Honeybees

    ERIC Educational Resources Information Center

    Raccuglia, Davide; Mueller, Uli

    2013-01-01

    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…

  19. Elevated levels of GABA+ in migraine detected using (1) H-MRS.

    PubMed

    Aguila, Maria-Eliza R; Lagopoulos, Jim; Leaver, Andrew M; Rebbeck, Trudy; Hübscher, Markus; Brennan, Patrick C; Refshauge, Kathryn M

    2015-07-01

    γ-Aminobutyric acid (GABA) has been implicated in several pain conditions, yet no study has systematically evaluated GABA levels in migraine using (1) H-MRS. The accurate detection, separation and quantification of GABA in individuals with migraine could elucidate the role of this neurotransmitter in migraine pathophysiology. Such information may eventually be useful in the diagnosis and development of more effective treatments for migraine. The aims of this study were therefore to compare the concentration of GABA+ in individuals with migraine with that in asymptomatic individuals, and to determine the diagnostic potential of GABA+ in the classification of those with or without migraine. In this case-control study, GABA+ levels in the brain were determined in 19 participants with migraine and 19 matched controls by (1) H-MRS using Mescher-Garwood point-resolved spectroscopy (MEGA-PRESS) sequence. The diagnostic accuracy of GABA+ for the detection of migraine and the optimal cut-off value were determined by receiver operating characteristic analysis. GABA+ levels were significantly higher (p = 0.002) in those with migraine [median, 1.41 institutional units (IU); interquartile range, 1.31-1.50 IU] than in controls (median, 1.18 IU; interquartile range, 1.12-1.35 IU). The GABA+ concentration appears to have good accuracy for the classification of individuals with or without migraine [area under the curve (95% confidence interval), 0.837 (0.71-0.96); p < 0.001]. The optimal GABA+ cut-off value for migraine was 1.30 IU, with a sensitivity of 84.2%, specificity of 68.4% and positive likelihood ratio of +2.67. The outcomes of this study suggest altered GABA metabolism in migraine. These results add to the scarce evidence on the putative role of GABA in migraine and provide a basis to further explore the causal relationship between GABA+ and the pathophysiology of migraine. This study also demonstrates that GABA+ concentration has good diagnostic accuracy for migraine

  20. Common Distribution of gad Operon in Lactobacillus brevis and its GadA Contributes to Efficient GABA Synthesis toward Cytosolic Near-Neutral pH

    PubMed Central

    Wu, Qinglong; Tun, Hein Min; Law, Yee-Song; Khafipour, Ehsan; Shah, Nagendra P.

    2017-01-01

    Many strains of lactic acid bacteria (LAB) and bifidobacteria have exhibited strain-specific capacity to produce γ-aminobutyric acid (GABA) via their glutamic acid decarboxylase (GAD) system, which is one of amino acid-dependent acid resistance (AR) systems in bacteria. However, the linkage between bacterial AR and GABA production capacity has not been well established. Meanwhile, limited evidence has been provided to the global diversity of GABA-producing LAB and bifidobacteria, and their mechanisms of efficient GABA synthesis. In this study, genomic survey identified common distribution of gad operon-encoded GAD system in Lactobacillus brevis for its GABA production among varying species of LAB and bifidobacteria. Importantly, among four commonly distributed amino acid-dependent AR systems in Lb. brevis, its GAD system was a major contributor to maintain cytosolic pH homeostasis by consuming protons via GABA synthesis. This highlights that Lb. brevis applies GAD system as the main strategy against extracellular and intracellular acidification demonstrating its high capacity of GABA production. In addition, the abundant GadA retained its activity toward near-neutral pH (pH 5.5–6.5) of cytosolic acidity thus contributing to efficient GABA synthesis in Lb. brevis. This is the first global report illustrating species-specific characteristic and mechanism of efficient GABA synthesis in Lb. brevis. PMID:28261168

  1. Common Distribution of gad Operon in Lactobacillus brevis and its GadA Contributes to Efficient GABA Synthesis toward Cytosolic Near-Neutral pH.

    PubMed

    Wu, Qinglong; Tun, Hein Min; Law, Yee-Song; Khafipour, Ehsan; Shah, Nagendra P

    2017-01-01

    Many strains of lactic acid bacteria (LAB) and bifidobacteria have exhibited strain-specific capacity to produce γ-aminobutyric acid (GABA) via their glutamic acid decarboxylase (GAD) system, which is one of amino acid-dependent acid resistance (AR) systems in bacteria. However, the linkage between bacterial AR and GABA production capacity has not been well established. Meanwhile, limited evidence has been provided to the global diversity of GABA-producing LAB and bifidobacteria, and their mechanisms of efficient GABA synthesis. In this study, genomic survey identified common distribution of gad operon-encoded GAD system in Lactobacillus brevis for its GABA production among varying species of LAB and bifidobacteria. Importantly, among four commonly distributed amino acid-dependent AR systems in Lb. brevis, its GAD system was a major contributor to maintain cytosolic pH homeostasis by consuming protons via GABA synthesis. This highlights that Lb. brevis applies GAD system as the main strategy against extracellular and intracellular acidification demonstrating its high capacity of GABA production. In addition, the abundant GadA retained its activity toward near-neutral pH (pH 5.5-6.5) of cytosolic acidity thus contributing to efficient GABA synthesis in Lb. brevis. This is the first global report illustrating species-specific characteristic and mechanism of efficient GABA synthesis in Lb. brevis.

  2. A study on the involvement of GABA-transaminase in MCT induced pulmonary hypertension.

    PubMed

    Lingeshwar, Poorella; Kaur, Gurpreet; Singh, Neetu; Singh, Seema; Mishra, Akanksha; Shukla, Shubha; Ramakrishna, Rachumallu; Laxman, Tulsankar Sachin; Bhatta, Rabi Sankar; Siddiqui, Hefazat H; Hanif, Kashif

    2016-02-01

    Increased sympathetic nervous system (SNS) activity is associated with cardiovascular diseases but its role has not been completely explored in pulmonary hypertension (PH). Increased SNS activity is distinguished by elevated level of norepinephrine (NE) and activity of γ-Amino butyric acid Transminase (GABA-T) which degrades GABA, an inhibitory neurotransmitter within the central and peripheral nervous system. Therefore, we hypothesized that GABA-T may contribute in pathophysiology of PH by modulating level of GABA and NE. The effect of daily oral administration of GABA-T inhibitor, Vigabatrin (GVG, 50 and 75 mg/kg/day, 35 days) was studied following a single subcutaneous administration of monocrotaline (MCT, 60 mg/kg) in male SD rats. The pressure and hypertrophy of right ventricle (RV), oxidative stress, inflammation, pulmonary vascular remodelling were assessed after 35 days in MCT treated rats. The expression of GABA-T and HIF-1α was studied in lung tissue. The levels of plasma NE (by High performance liquid chromatography coupled with electrochemical detector; HPLC-ECD) and lung GABA (by liquid chromatography-mass spectrometry) were also estimated. GVG at both doses significantly attenuated increased in pressure (35.82 ± 4.80 mm Hg, p < 0.001; 28.37 ± 3.32 mm Hg, p < 0.001 respectively) and hypertrophy of RV, pulmonary vascular remodelling, oxidative stress and inflammation in lungs of MCT exposed rats. GVG also reduced the expression of GABA-T and HIF-1α in MCT treated rats. Increased NE level and decreased GABA level was also reversed by GVG in MCT exposed rats. GABA-T plays an important role in PH by modulating SNS activity and may be considered as a therapeutic target in PH.

  3. GABA System in Schizophrenia and Mood Disorders: A Mini Review on Third-Generation Imaging Studies

    PubMed Central

    Chiapponi, Chiara; Piras, Federica; Piras, Fabrizio; Caltagirone, Carlo; Spalletta, Gianfranco

    2016-01-01

    Third-generation neuroimaging research has been enriched by advances in magnetic resonance spectroscopy (MRS) measuring the concentration of important neurotrasmitters, such as the inhibitory amino acid GABA. Here, we performed a systematic mini-review on brain MRS studies measuring GABA concentration in patients affected by schizophrenia (SZ), bipolar disorder (BD), and major depressive disorder (MDD). We wondered whether multimodal investigations could overcome intrinsic technical limits of MRS giving a broader view of mental disorders pathogenesis. In SZ, unimodal studies gave mixed results, as increased, decreased, or unaltered GABA levels were reported depending on region, disease phase, and treatment. Conversely, multimodal results showed reduced level of glutamate, but not of GABA, in patients mirrored by in vitro biochemical findings revealing hippocampal reduction in glutamate signaling in SZ, and no deficits in GABA synthesis. Moreover, a mouse model confirmed the unique pathological characteristic of glutamate function in SZ. Unimodal studies in BD revealed again, inconsistent results, while no multimodal investigations including MRS on GABA exist. In MDD, unimodal studies could not differentiate patients from controls nor characterize high-risk subjects and remitted patients. However, a multimodal study combining functional magnetic resonance imaging and MRS revealed that cingulate cortex activity is related to glutamate, N-acetylaspartate levels and anhedonia in patients, and to GABA concentration in healthy subjects, improving the distinction between MDD and physiology. Overall, our results show that unimodal studies do not indicate GABA as a biomarker for the psychiatric disorders considered. Conversely, multimodal studies can widen the understanding of the link between psychopathology, genetics, neuroanatomy, and functional–biochemical brain activity in mental disorders. Although scarce, multimodal approaches seem promising for moving from GABA

  4. GABA excitation in mouse hilar neuropeptide Y neurons

    PubMed Central

    Fu, Li-Ying; van den Pol, Anthony N

    2007-01-01

    Neuropeptide Y-containing interneurons in the dentate hilar area play an important role in inhibiting the activity of hippocampal circuitry. Hilar cells are often among the first lost in hippocampal epilepsy. As many types of neurons are found in the hilus, we used a new transgenic mouse expressing green fluorescent protein (GFP) in a subset of neurons that colocalized neuropeptide Y (NPY), somatostatin (SST), and GABA for whole-cell, perforated, and cell-attached recording in 240 neurons. As these neurons have not previously been identifiable in live slices, they have not been the focus of physiological analysis. Hilar NPY neurons showed modest spike frequency adaptation, a large 15.6 ± 1.0 mV afterhyperpolarization, a mean input resistance of 335 ± 26 mΩ, and were capable of fast-firing. Muscimol-mediated excitatory actions were found in a nominally Ca2+-free/high-Mg2+ bath solution using cell-attached recording. GABAA receptor antagonists inhibited half the recorded neurons and blocked burst firing. Gramicidin perforated-patch recording revealed a GABA reversal potential positive to both the resting membrane potential and spike threshold. Together, these data suggest GABA is excitatory to many NPY cells. NPY and SST consistently hyperpolarized and reduced spike frequency in these neurons. No hyperpolarization of NPY on membrane potential was detected in the presence of tetrodotoxin, AP5, CNQX and bicuculline, supporting an indirect effect. Under similar conditions, SST hyperpolarized the cells, suggesting a direct postsynaptic action. Depolarizing actions of GABA and GABA-dependent burst-firing may synchronize a rapid release of GABA, NPY, and SST, leading to pre- and postsynaptic inhibition of excitatory hippocampal circuits. PMID:17204505

  5. Maternal oxytocin triggers a transient inhibitory switch in GABA signaling in the fetal brain during delivery.

    PubMed

    Tyzio, Roman; Cossart, Rosa; Khalilov, Ilgam; Minlebaev, Marat; Hübner, Christian A; Represa, Alfonso; Ben-Ari, Yehezkel; Khazipov, Rustem

    2006-12-15

    We report a signaling mechanism in rats between mother and fetus aimed at preparing fetal neurons for delivery. In immature neurons, gamma-aminobutyric acid (GABA) is the primary excitatory neurotransmitter. We found that, shortly before delivery, there is a transient reduction in the intracellular chloride concentration and an excitatory-to-inhibitory switch of GABA actions. These events were triggered by oxytocin, an essential maternal hormone for labor. In vivo administration of an oxytocin receptor antagonist before delivery prevented the switch of GABA actions in fetal neurons and aggravated the severity of anoxic episodes. Thus, maternal oxytocin inhibits fetal neurons and increases their resistance to insults during delivery.

  6. Efficient Modulation of γ-Aminobutyric Acid Type A Receptors by Piperine Derivatives

    PubMed Central

    2014-01-01

    Piperine activates TRPV1 (transient receptor potential vanilloid type 1 receptor) receptors and modulates γ-aminobutyric acid type A receptors (GABAAR). We have synthesized a library of 76 piperine analogues and analyzed their effects on GABAAR by means of a two-microelectrode voltage-clamp technique. GABAAR were expressed in Xenopus laevis oocytes. Structure–activity relationships (SARs) were established to identify structural elements essential for efficiency and potency. Efficiency of piperine derivatives was significantly increased by exchanging the piperidine moiety with either N,N-dipropyl, N,N-diisopropyl, N,N-dibutyl, p-methylpiperidine, or N,N-bis(trifluoroethyl) groups. Potency was enhanced by replacing the piperidine moiety by N,N-dibutyl, N,N-diisobutyl, or N,N-bistrifluoroethyl groups. Linker modifications did not substantially enhance the effect on GABAAR. Compound 23 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dipropyl-2,4-pentadienamide] induced the strongest modulation of GABAA (maximal GABA-induced chloride current modulation (IGABA-max = 1673% ± 146%, EC50 = 51.7 ± 9.5 μM), while 25 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dibutyl-2,4-pentadienamide] displayed the highest potency (EC50 = 13.8 ± 1.8 μM, IGABA-max = 760% ± 47%). Compound 23 induced significantly stronger anxiolysis in mice than piperine and thus may serve as a starting point for developing novel GABAAR modulators. PMID:24905252

  7. Differentiating enantioselective actions of GABOB: a possible role for threonine 244 in the binding site of GABA(C) ρ(1) receptors.

    PubMed

    Yamamoto, Izumi; Absalom, Nathan; Carland, Jane E; Doddareddy, Munikumar R; Gavande, Navnath; Johnston, Graham A R; Hanrahan, Jane R; Chebib, Mary

    2012-09-19

    Designing potent and subtype-selective ligands with therapeutic value requires knowledge about how endogenous ligands interact with their binding site. 4-Amino-3-hydroxybutanoic acid (GABOB) is an endogenous ligand found in the central nervous system in mammals. It is a metabolic product of GABA, the major inhibitory neurotransmitter. Homology modeling of the GABA(C) ρ(1) receptor revealed a potential H-bond interaction between the hydroxyl group of GABOB and threonine 244 (T244) located on loop C of the ligand binding site of the ρ(1) subunit. Using site-directed mutagenesis, we examined the effect of mutating T244 on the efficacy and pharmacology of GABOB and various ligands. It was found that mutating T244 to amino acids that lacked a hydroxyl group in their side chains produced GABA insensitive receptors. Only by mutating ρ(1)T244 to serine (ρ(1)T244S) produced a GABA responsive receptor, albeit 39-fold less sensitive to GABA than ρ(1)wild-type. We also observed changes in the activities of the GABA(C) receptor partial agonists, muscimol and imidazole-4-acetic acid (I4AA). At the concentrations we tested, the partial agonists antagonized GABA-induced currents at ρ(1)T244S mutant receptors (Muscimol: ρ(1)wild-type, EC(50) = 1.4 μM; ρ(1)T244S, IC(50) = 32.8 μM. I4AA: ρ(1)wild-type, EC(50) = 8.6 μM; ρ(1)T244S, IC(50) = 21.4 μM). This indicates that T244 is predominantly involved in channel gating. R-(-)-GABOB and S-(+)-GABOB are full agonists at ρ(1)wild-type receptors. In contrast, R-(-)-GABOB was a weak partial agonist at ρ(1)T244S (1 mM activates 26% of the current produced by GABA EC(50) versus ρ(1)wild-type, EC(50) = 19 μM; I(max) 100%), and S-(+)-GABOB was a competitive antagonist at ρ(1)T244S receptors (ρ(1)wild-type, EC(50) = 45 μM versus ρ(1)T244S, IC(50) = 417.4 μM, K(B) = 204 μM). This highlights that the interaction of GABOB with T244 is enantioselective. In contrast, the potencies of a range of antagonists tested, 3-aminopropyl

  8. Repression of gamma-aminobutyric acid type A receptor alpha1 polypeptide biosynthesis requires chronic agonist exposure.

    PubMed

    Miranda, J D; Barnes, E M

    1997-06-27

    Although it is well established that the number of gamma-aminobutyric acid type A (GABAA) receptors declines in cortical neurons exposed to GABAA receptor agonists, the mechanisms responsible for this use-dependent down-regulation remain unclear. Two hypotheses have been proposed: (i) agonist-evoked sequestration and degradation of surface GABAA receptors and (ii) repression of receptor subunit biosynthesis. We have addressed this problem using [35S]Met/Cys pulse-chase labeling of chick cortical neurons in culture and immunoprecipitation and immunoblotting with an antibody (RP4) directed against a GABAA receptor alpha1-(331-381) fusion protein. Exposure of the cells to GABA or isoguvacine for 2 h to 4 days had no effect on the initial rate of 35S incorporation into the GABAA receptor 51-kDa alpha1 polypeptide, but this rate declined by 33% after a 7-day treatment. This is consistent with a previous report (Baumgartner, B. J., Harvey, R. J., Darlison, M. G., and Barnes, E. M. (1994) Mol. Brain Res. 26, 9-17) that a 7-day GABA treatment of this preparation produced a 45% reduction in the alpha1 subunit mRNA level, while a 4-day exposure had no detectable effect. On the other hand, after a 4-day exposure to these agonists, a 30% reduction in the level of the alpha1 polypeptide was observed on immunoblots, similar to that found previously for down-regulation of GABAA receptor ligand-binding sites. Thus, the de novo synthesis of GABAA receptor alpha1 subunits is subject to a delayed use-dependent repression that was observed after, rather than before, the decline in neuronal levels of the polypeptide. Pulse-chase experiments showed a monophasic degradation of the GABAA receptor 35S-alpha1 subunit with a t1/2 = 7.7 h, a process that was unaffected by the addition of GABA to neurons during the chase period. These nascent 35S-labeled polypeptides are presumably diluted into the neuronal pool of unlabeled unassembled alpha1 subunits, which was found to exceed by a 4:1 molar

  9. Neurosteroids and GABA-A Receptor Function

    PubMed Central

    Wang, Mingde

    2011-01-01

    Neurosteroids represent a class of endogenous steroids that are synthesized in the brain, the adrenals, and the gonads and have potent and selective effects on the GABAA-receptor. 3α-hydroxy A-ring reduced metabolites of progesterone, deoxycorticosterone, and testosterone are positive modulators of GABAA-receptor in a non-genomic manner. Allopregnanolone (3α-OH-5α-pregnan-20-one), 5α-androstane-3α, 17α-diol (Adiol), and 3α5α-tetrahydrodeoxycorticosterone (3α5α-THDOC) enhance the GABA-mediated Cl- currents acting on a site (or sites) distinct from the GABA, benzodiazepine, barbiturate, and picrotoxin binding sites. 3α5α-P and 3α5α-THDOC potentiate synaptic GABAA-receptor function and activate δ-subunit containing extrasynaptic receptors that mediate tonic currents. On the contrary, 3β-OH pregnane steroids and pregnenolone sulfate (PS) are GABAA-receptor antagonists and induce activation-dependent inhibition of the receptor. The activities of neurosteroid are dependent on brain regions and types of neurons. In addition to the slow genomic action of the parent steroids, the non-genomic, and rapid actions of neurosteroids play a significant role in the GABAA-receptor function and shift in mood and memory function. This review describes molecular mechanisms underlying neurosteroid action on the GABAA-receptor, mood changes, and cognitive functions. PMID:22654809

  10. Extracellular gamma-aminobutyric acid levels in the rat caudate-putamen: monitoring the neuronal and glial contribution by intracerebral microdialysis.

    PubMed

    Campbell, K; Kalén, P; Lundberg, C; Wictorin, K; Rosengren, E; Björklund, A

    1993-06-18

    Intracerebral microdialysis with high pressure liquid chromatography (HPLC) coupled to electrochemical detection was employed to characterize gamma-aminobutyric acid (GABA) release and the effects induced by a preceding neuron-depleting ibotenic acid (IBO) lesion in the rat caudate-putamen (CPu). Extracellular GABA overflow was monitored in the intact and excitotoxically lesioned CPu, either 7-10 days (acute) or more than 3 months post-lesioning (chronic), using loop type dialysis probes perfused at a rate of 2 microliters/min. In the intact CPuu, basal GABA levels were 0.97 pmol/30 microliters of dialysate in the awake animals and 0.76 pmol/30 microliters under halothane anaesthesia. In both the acute and chronic IBO lesioned CPu the extracellular GABA levels were reduced by 80% and 67%, respectively, under halothane anaesthesia. KCl added to the perfusion fluid at a concentration of 100 mM resulted in dramatic increases in GABA overflow from baseline levels in the intact CPu (60- to 70-fold), which were almost totally abolished (> 95%) in the excitotoxically lesioned CPu. Veratridine administered at 75 microM, produced a 45-fold increase in GABA overflow in the intact CPu, but failed to produce any effect in the lesioned CPu. The addition of nipecotic acid (0.5 mM), a GABA uptake blocker, increased basal extracellular GABA levels 6-15-fold in the intact CPu, while GABA overflow in either the acute or chronic lesioned CPu was not significantly altered. Although Ca(2+)-free conditions (with 20 mM Mg2+ added) or tetrodotoxin (TTX, 1 microM) did not alter the basal GABA overflow in the intact CPU under halothane anaesthesia, the omission of Ca2+ resulted in a 47% reduction in basal extracellular GABA levels in awake, freely moving animals. Nipecotic acid-induced GABA overflow was reduced by 22% under Ca(2+)-free conditions, and by 33% in the presence of 1 microM TTX. Moreover, KCl-evoked GABA overflow was reduced by 86% in Ca(2+)-free conditions and by 40% when

  11. Comparing GABA-dependent physiological measures of inhibition with proton magnetic resonance spectroscopy measurement of GABA using ultra-high-field MRI.

    PubMed

    Dyke, Katherine; Pépés, Sophia E; Chen, Chen; Kim, Soyoung; Sigurdsson, Hilmar P; Draper, Amelia; Husain, Masud; Nachev, Parashkev; Gowland, Penelope A; Morris, Peter G; Jackson, Stephen R

    2017-03-09

    Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networks are thought to underlie many brain and mental health disorders, and for this reason there is considerable interest in investigating how individual variability in localised concentrations of these molecules relate to brain disorders. Magnetic resonance spectroscopy (MRS) provides a reliable means of measuring, in vivo, concentrations of neurometabolites such as GABA, glutamate and glutamine that can be correlated with brain function and dysfunction. However, an issue of much debate is whether the GABA observed and measured using MRS represents the entire pool of GABA available for measurement (i.e., metabolic, intracellular, and extracellular) or is instead limited to only some portion of it. GABA function can also be investigated indirectly in humans through the use of non-invasive transcranial magnetic stimulation (TMS) techniques that can be used to measure cortical excitability and GABA-mediated physiological inhibition. To investigate this issue further we collected in a single session both types of measurement, i.e., TMS measures of cortical excitability and physiological inhibition and ultra-high-field (7 T) MRS measures of GABA, glutamate and glutamine, from the left sensorimotor cortex of the same group of right-handed individuals. We found that TMS and MRS measures were largely uncorrelated with one another, save for the plateau of the TMS IO curve that was negatively correlated with MRS-Glutamate (Glu) and intra-cortical facilitation (10ms ISI) that was positively associated with MRS-Glutamate concentration. These findings are consistent with the view that the GABA concentrations measured using the MRS largely represent pools of GABA that are linked to tonic rather than phasic inhibition and thus contribute to the inhibitory tone of a brain area rather than GABAergic synaptic transmission.

  12. Vibrational circular dichroism (VCD) chiral assignment of atropisomers: application to γ-aminobutyric acid (GABA) modulators designed as potential anxiolytic drugs.

    PubMed

    Pivonka, Don E; Wesolowski, Steven S

    2013-04-01

    Atropisomers exist when axial chirality is present as a result of conformationally restricted rotation around a single bond. The interconversion rate of the individual atropisomers is critical to the assessment of chiral stability of a drug throughout scale-up, development, production, and storage as well as in vivo pharmacokinetics. We describe the application of vibrational circular dichroism spectroscopy coupled with quantum mechanics simulations to assign the absolute axial chirality and measure the racemization half-life of a series of potential anxiolytic drugs that act as γ-aminobutyric acid modulators.

  13. Novel functions of GABA signaling in adult neurogenesis

    PubMed Central

    PONTES, Adalto; ZHANG, Yonggang; HU, Wenhui

    2013-01-01

    Neurotransmitter gamma-aminobutiric acid (GABA) through ionotropic GABAA and metabotropic GABAB receptors plays key roles in modulating the development, plasticity and function of neuronal networks. GABA is inhibitory in mature neurons but excitatory in immature neurons, neuroblasts and neural stem/progenitor cells (NSCs/NPCs). The switch from excitatory to inhibitory occurs following the development of glutamatergic synaptic input and results from the dynamic changes in the expression of Na+/K+/2Cl− co-transporter NKCC1 driving Cl− influx and neuron-specific K+/Cl− co-transporter KCC2 driving Cl− efflux. The developmental transition of KCC2 expression is regulated by Disrupted-in-Schizophrenia 1 (DISC1) and brain-derived neurotrophic factor (BDNF) signaling. The excitatory GABA signaling during early neurogenesis is important to the activity/experience-induced regulation of NSC quiescence, NPC proliferation, neuroblast migration and newborn neuronal maturation/functional integration. The inhibitory GABA signaling allows for the sparse and static functional networking essential for learning/memory development and maintenance. PMID:24285940

  14. Glutamate and GABA modulate dopamine in the pedunculopontine tegmental nucleus.

    PubMed

    Steiniger, Björn; Kretschmer, Beate D

    2003-04-01

    The pedunculopontine tegmental nucleus (PPTg) has an important anatomical position connecting basal ganglia and limbic systems with motor execution structures in the pons and spinal cord. It receives glutamatergic and GABAergic input and has additional reciprocal connections with mesencephalic dopaminergic neurons, suggesting that the PPTg plays a key role in frontostriatal information processing. In vivo microdialysis in freely moving rats, in combination with behavioral analysis, was used in this study to investigate whether the dopaminergic input can be modulated at the level of the PPTg via N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) or GABA(B) receptors. Stimulation of the GABA(B) receptor decreased dopamine release in the PPTg while that of the AMPA and NMDA receptors increased it. A time-related comparison of the effects of NMDA (0.75 and 1 mM) and AMPA (50 and 25 microM) revealed a more long-lasting effect after AMPA stimulation than after NMDA. However, only the infusion of the GABA(B) receptor agonist baclofen (100 and 200 microM) stimulated stereotyped behavior (e.g. sniffing, digging or head movements) and contralateral circling. This study clearly demonstrates that GABAergic as well as glutamatergic terminals in the PPTg are critically involved in the modulation of the dopamine system. Moreover, a decrease in PPTg dopamine via GABA(B) receptor stimulation seems to be behaviorally relevant.

  15. Action of tremorgenic mycotoxins on GABA/sub A/ receptor

    SciTech Connect

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

    1987-11-09

    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.

  16. Cocaine inhibition of GABA(A) current: role of dephosphorylation.

    PubMed

    Ye, Jiang-Hong; Ren, Jun

    2006-01-01

    Acute cocaine toxicity is frequently associated with seizures. The mechanisms underlying the convulsant effect of cocaine are not well understood. Previously, we have shown that cocaine depresses whole-cell current evoked by gamma-aminobutyric acid (GABA) in hippocampal neurons freshly isolated from rats. Cocaine's effect was voltage-independent and concentration-dependent. In the present study, using whole-cell patch-clamp recording on rat neurons freshly isolated from hippocampus, we examined the intracellular mechanisms involved in cocaine's action. Increasing intracellular Ca(2+) concentration ([Ca]i) from 0.01 to 5 microM strongly increased the depressant effect of cocaine. By contrast, 1-[N, O-bis (5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62), a specific antagonist of Ca/calmodulin-dependent protein kinase (CaMKII), attenuated or enhanced cocaine's action in different neurons: in three out of nine neurons dialysed with 5 microM KN-62,1 mM cocaine depressed GABA current by only 33%, but in another three out of nine neurons, cocaine depressed GABA current by as much as 83%. Chelerythrine (a specific CaCa(2+)/phospholipid-dependent protein kinase C [PKC] antagonist) had minimal effect on cocaine's action. We suggest that cocaine induces an increase in [Ca]i, which stimulates phosphatase activity and thus leads to dephosphorylation of GABA receptors. This dephosphorylation-mediated disinhibitory action may play a role in cocaine-induced convulsant states.

  17. Methamphetamine-evoked depression of GABA(B) receptor signaling in GABA neurons of the VTA.

    PubMed

    Padgett, Claire L; Lalive, Arnaud L; Tan, Kelly R; Terunuma, Miho; Munoz, Michaelanne B; Pangalos, Menelas N; Martínez-Hernández, José; Watanabe, Masahiko; Moss, Stephen J; Luján, Rafael; Lüscher, Christian; Slesinger, Paul A

    2012-03-08

    Psychostimulants induce neuroadaptations in excitatory and fast inhibitory transmission in the ventral tegmental area (VTA). Mechanisms underlying drug-evoked synaptic plasticity of slow inhibitory transmission mediated by GABA(B) receptors and G protein-gated inwardly rectifying potassium (GIRK/Kir(3)) channels, however, are poorly understood. Here, we show that 1 day after methamphetamine (METH) or cocaine exposure both synaptically evoked and baclofen-activated GABA(B)R-GIRK currents were significantly depressed in VTA GABA neurons and remained depressed for 7 days. Presynaptic inhibition mediated by GABA(B)Rs on GABA terminals was also weakened. Quantitative immunoelectron microscopy revealed internalization of GABA(B1) and GIRK2, which occurred coincident with dephosphorylation of serine 783 (S783) in GABA(B2), a site implicated in regulating GABA(B)R surface expression. Inhibition of protein phosphatases recovered GABA(B)R-GIRK currents in VTA GABA neurons of METH-injected mice. This psychostimulant-evoked impairment in GABA(B)R signaling removes an intrinsic brake on GABA neuron spiking, which may augment GABA transmission in the mesocorticolimbic system.

  18. Comparative density of CCK- and PV-GABA cells within the cortex and hippocampus

    PubMed Central

    Whissell, Paul D.; Cajanding, Janine D.; Fogel, Nicole; Kim, Jun Chul

    2015-01-01

    Cholecystokinin (CCK)- and parvalbumin (PV)-expressing neurons constitute the two major populations of perisomatic GABAergic neurons in the cortex and the hippocampus. As CCK- and PV-GABA neurons differ in an array of morphological, biochemical and electrophysiological features, it has been proposed that they form distinct inhibitory ensembles which differentially contribute to network oscillations and behavior. However, the relationship and balance between CCK- and PV-GABA neurons in the inhibitory networks of the brain is currently unclear as the distribution of these cells has never been compared on a large scale. Here, we systemically investigated the distribution of CCK- and PV-GABA cells across a wide number of discrete forebrain regions using an intersectional genetic approach. Our analysis revealed several novel trends in the distribution of these cells. While PV-GABA cells were more abundant overall, CCK-GABA cells outnumbered PV-GABA cells in several subregions of the hippocampus, medial prefrontal cortex and ventrolateral temporal cortex. Interestingly, CCK-GABA cells were relatively more abundant in secondary/association areas of the cortex (V2, S2, M2, and AudD/AudV) than they were in corresponding primary areas (V1, S1, M1, and Aud1). The reverse trend was observed for PV-GABA cells. Our findings suggest that the balance between CCK- and PV-GABA cells in a given cortical region is related to the type of processing that area performs; inhibitory networks in the secondary cortex tend to favor the inclusion of CCK-GABA cells more than networks in the primary cortex. The intersectional genetic labeling approach employed in the current study expands upon the ability to study molecularly defined subsets of GABAergic neurons. This technique can be applied to the investigation of neuropathologies which involve disruptions to the GABAergic system, including schizophrenia, stress, maternal immune activation and autism. PMID:26441554

  19. Roles for gamma-aminobutyric acid in the development of the paraventricular nucleus of the hypothalamus.

    PubMed

    McClellan, Kristy M; Stratton, Matthew S; Tobet, Stuart A

    2010-07-15

    The development of the hypothalamic paraventricular nucleus (PVN) involves several factors that work together to establish a cell group that regulates neuroendocrine functions and behaviors. Several molecular markers were noted within the developing PVN, including estrogen receptors (ER), neuronal nitric oxide synthase (nNOS), and brain-derived neurotrophic factor (BDNF). By contrast, immunoreactive gamma-aminobutyric acid (GABA) was found in cells and fibers surrounding the PVN. Two animal models were used to test the hypothesis that GABA works through GABA(A) and GABA(B) receptors to influence the development of the PVN. Treatment with bicuculline to decrease GABA(A) receptor signaling from embryonic day (E) 10 to E17 resulted in fewer cells containing immunoreactive (ir) ERalpha in the region of the PVN vs. control. GABA(B)R1 receptor subunit knockout mice were used to examine the PVN at P0 without GABA(B) signaling. In female but not male GABA(B)R1 subunit knockout mice, the positions of cells containing ir ERalpha shifted from medial to lateral compared with wild-type controls, whereas the total number of ir ERalpha-containing cells was unchanged. In E17 knockout mice, ir nNOS cells and fibers were spread over a greater area. There was also a significant decrease in ir BDNF in the knockout mice in a region-dependent manner. Changes in cell position and protein expression subsequent to disruption of GABA signaling may be due, in part, to changes in nNOS and BDNF signaling. Based on the current study, the PVN can be added as another site where GABA exerts morphogenetic actions in development.

  20. GABA uptake into astrocytes is not associated with significant metabolic cost: implications for brain imaging of inhibitory transmission.

    PubMed

    Chatton, Jean-Yves; Pellerin, Luc; Magistretti, Pierre J

    2003-10-14

    Synaptically released glutamate has been identified as a signal coupling excitatory neuronal activity to increased glucose utilization. The proposed mechanism of this coupling involves glutamate uptake into astrocytes resulting in increased intracellular Na+ (Nai+) and activation of the Na+/K+-ATPase. Increased metabolic demand linked to disruption of Nai+ homeostasis activates glucose uptake and glycolysis in astrocytes. Here, we have examined whether a similar neurometabolic coupling could operate for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), also taken up by Na+-dependent transporters into astrocytes. Thus, we have compared the Nai+ response to GABA and glutamate in mouse astrocytes by microspectrofluorimetry. The Nai+ response to GABA consisted of a rapid rise of 4-6 mM followed by a plateau that did not, however, significantly activate the pump. Indeed, the GABA transporter-evoked Na+ influxes are transient in nature, almost totally shutting off within approximately 30 sec of GABA application. The metabolic consequences of the GABA-induced Nai+ response were evaluated by monitoring cellular ATP changes indirectly in single cells and measuring 2-deoxyglucose uptake in astrocyte populations. Both approaches showed that, whereas glutamate induced a robust metabolic response in astrocytes (decreased ATP levels and glucose uptake stimulation), GABA did not cause any measurable metabolic response, consistent with the Nai+ measurements. Results indicate that GABA does not couple inhibitory neuronal activity with glucose utilization, as does glutamate for excitatory neurotransmission, and suggest that GABA-mediated synaptic transmission does not contribute directly to brain imaging signals based on deoxyglucose.

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

    SciTech Connect

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

    1988-12-01

    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.

  2. Differential effects of GABA in modulating nociceptive vs. non-nociceptive synapses.

    PubMed

    Wang, Y; Summers, T; Peterson, W; Miiller, E; Burrell, B D

    2015-07-09

    GABA (γ-amino-butyric acid) -mediated signaling is normally associated with synaptic inhibition due to ionotropic GABA receptors that gate an inward Cl(-) current, hyperpolarizing the membrane potential. However, there are also situations where ionotropic GABA receptors trigger a Cl(-) efflux that results in depolarization. The well-characterized central nervous system of the medicinal leech was used to study the functional significance of opposing effects of GABA at the synaptic circuit level. Specifically, we focused on synapses made by the nociceptive N cell and the non-nociceptive P (pressure) cell that converge onto a common postsynaptic target. It is already known that GABA hyperpolarizes the P cell, but depolarizes the N cell and that inhibition of ionotropic GABA receptors by bicuculline (BIC) has opposing effects on the synapses made by these two inputs; enhancing P cell synaptic transmission, but depressing N cell synapses. The goal of the present study was to determine whether the opposing effects of GABA were due to differences in Cl(-) homeostasis between the two presynaptic neurons. VU 0240551 (VU), an inhibitor of the Cl(-) exporter K-Cl co-transporter isoform 2 (KCC2), attenuated GABA-mediated hyperpolarization of the non-nociceptive afferent while bumetanide (BUM), an inhibitor of the Cl(-) importer Na-K-Cl co-transporter isoform 1 (NKCC1), reduced GABA-mediated depolarization of the nociceptive neuron. VU treatment also enhanced P cell synaptic signaling, similar to the previously observed effects of BIC and consistent with the idea that GABA inhibits synaptic signaling at the presynaptic level. BUM treatment depressed N cell synapses, again similar to what is observed following BIC treatment and suggests that GABA has an excitatory effect on these synapses. The opposing effects of GABA could also be observed at the behavioral level with BIC and VU increasing responsiveness to non-nociceptive stimulation while BIC and BUM decreased responsiveness

  3. Sleep-promoting effects of the GABA/5-HTP mixture in vertebrate models.

    PubMed

    Hong, Ki-Bae; Park, Yooheon; Suh, Hyung Joo

    2016-09-01

    The aim of this study was to investigate the sleep-promoting effect of combined γ-aminobutyric acid (GABA) and 5-hydroxytryptophan (5-HTP) on sleep quality and quantity in vertebrate models. Pentobarbital-induced sleep test and electroencephalogram (EEG) analysis were applied to investigate sleep latency, duration, total sleeping time and sleep quality of two amino acids and GABA/5-HTP mixture. In addition, real-time PCR and HPLC analysis were applied to analyze the signaling pathway. The GABA/5-HTP mixture significantly regulated the sleep latency, duration (p<0.005), and also increased the sleep quality than single administration of the amino acids (p<0.000). Long-term administration increased the transcript levels of GABAA receptor (1.37-fold, p<0.000) and also increased the GABA content compared with the control group 12h after administration (1.43-fold, p<0.000). Our available evidence suggests that the GABA/5-HTP mixture modulates both GABAergic and serotonergic signaling. Moreover, the sleep architecture can be controlled by the regulation of GABAA receptor and GABA content with 5-HTP.

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

    PubMed

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

    2013-04-24

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    SciTech Connect

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

    1987-06-08

    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.

  7. γ-Aminobutyric acid-ρ expression in ependymal glial cells of the mouse cerebellum.

    PubMed

    Reyes-Haro, Daniel; González-González, María Alejandra; Pétriz, Adriana; Rosas-Arellano, Abraham; Kettenmann, Helmut; Miledi, Ricardo; Martínez-Torres, Ataulfo

    2013-04-01

    The ependymal glial cells (EGCs) from the periventricular zone of the cerebellum were studied to determine their distribution and the functional properties of their γ-aminobutyric acid type A (GABA(A) ) receptors. EGCs were identified by the presence of ciliated structures on their ventricular surface and their expression of glial fibrillary acidic protein (GFAP). Interestingly, diverse cell types, including neurons, astrocytes, and other types of glia, were identified in the subventricular zone by their current profiles. Electron microscopy showed ciliated cells and myelinated axons in this zone, but we found no collateral connections to suggest the presence of functional synapses. GABA-mediated currents were recorded from EGCs in cerebellar slices from postnatal days 13 to 35 (PN13-PN35). These currents were blocked by TPMPA (a highly specific GABA(A) ρ subunit antagonist) and bicuculline (a selective antagonist for classic GABA(A) receptors). Pentobarbital failed to modulate GABA(A)-mediated currents despite the expression of GABAα1 and GABAγ2 subunits. In situ hybridization, RT-PCR, and immunofluorescence studies confirmed GABAρ1 expression in EGCs of the cerebellum. We conclude that cerebellar EGCs express GABAρ1, which is functionally involved in GABA(A) receptor-mediated responses that are unique among glial cells of the brain.

  8. GABA and Muscimol as Reversible Inactivation Tools in Learning and Memory

    PubMed Central

    Majchrzak, M.; Di Scala, G.

    2000-01-01

    Reversible inactivation of brain areas is a useful method for inferring brain-behavior relationships. Infusion of GABA or of the GABA receptor agonist muscimol is considered one interesting reversible inactivation method because it may not affect fibers of passage and may therefore be compared to axon-sparing types of lesions. This article reviews the data obtained with this method in learning and memory experiments. A critical analysis of data, collected in collaboration with Simon Brailowsky, with chronic GABA infusion is presented, together with an illustration of data obtained with muscimol-induced inactivation. PMID:10709211

  9. GABA mediated excitation in immature rat CA3 hippocampal neurons.

    PubMed

    Cherubini, E; Rovira, C; Gaiarsa, J L; Corradetti, R; Ben Ari, Y

    1990-01-01

    Intracellular recordings from rat hippocampal neurons in vitro during the first postnatal week revealed the presence of spontaneous giant depolarizing potentials (GDPs). These were generated by the synchronous discharge of a population of neurons. GDPs reversed polarity at -27 and -51 mV when recorded with KCl or K-methylsulphate filled electrodes, respectively. GDPs were blocked by the GABAA receptor antagonist bicuculline (10 microM). Iontophoretic or bath applications of GABA (10-300 microM) in the presence of tetrodotoxin (1 microM), induced a membrane depolarization or in voltage clamp experiments an inward current which reversed polarity at the same potential as GDPs. The response to GABA was blocked in a non-competitive manner by bicuculline (10 microM) and did not desensitize. GABA mediated GDPs were presynaptically modulated by N-methyl-D-aspartate (NMDA) and non-NMDA receptors. Their frequency was reduced or blocked by NMDA receptor antagonists and by the rather specific non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). The frequency of GDPs was enhanced by glycine and D-serine (10-30 microM) in a strychnine insensitive manner. This effect was blocked by AP-5, suggesting that it was mediated by the allosteric modulatory site of the NMDA receptor. These observations suggest that most of the 'excitatory' drive in immature neurons is mediated by GABA acting on GABAA receptors; furthermore excitatory amino acids modulate the release of GABA by a presynaptic action on GABAergic interneurons.

  10. Magnetic resonance spectroscopy reveals oral Lactobacillus promotion of increases in brain GABA, N-acetyl aspartate and glutamate.

    PubMed

    Janik, Rafal; Thomason, Lynsie A M; Stanisz, Andrew M; Forsythe, Paul; Bienenstock, John; Stanisz, Greg J

    2016-01-15

    The gut microbiome has been shown to regulate the development and functions of the enteric and central nervous systems. Its involvement in the regulation of behavior has attracted particular attention because of its potential translational importance in clinical disorders, however little is known about the pathways involved. We previously have demonstrated that administration of Lactobacillus rhamnosus (JB-1) to healthy male BALB/c mice, promotes consistent changes in GABA-A and -B receptor sub-types in specific brain regions, accompanied by reductions in anxiety and depression-related behaviors. In the present study, using magnetic resonance spectroscopy (MRS), we quantitatively assessed two clinically validated biomarkers of brain activity and function, glutamate+glutamine (Glx) and total N-acetyl aspartate+N-acetyl aspartyl glutamic acid (tNAA), as well as GABA, the chief brain inhibitory neurotransmitter. Mice received 1×10(9) cfu of JB-1 per day for 4weeks and were subjected to MRS weekly and again 4weeks after cessation of treatment to ascertain temporal changes in these neurometabolites. Baseline concentrations for Glx, tNAA and GABA were equal to 10.4±0.3mM, 8.7±0.1mM, and 1.2±0.1mM, respectively. Delayed increases were first seen for Glx (~10%) and NAA (~37%) at 2weeks which persisted only to the end of treatment. However, Glx was still elevated 4weeks after treatment had ceased. Significantly elevated GABA (~25%) was only seen at 4weeks. These results suggest specific metabolic pathways in our pursuit of mechanisms of action of psychoactive bacteria. They also offer through application of standard clinical neurodiagnostic techniques, translational opportunities to assess biomarkers accompanying behavioral changes induced by alterations in the gut microbiome.

  11. Spinal GABA-B receptor modulates neutrophil recruitment to the knee joint in zymosan-induced arthritis.

    PubMed

    Bassi, Gabriel S; do C Malvar, David; Cunha, Thiago M; Cunha, Fernando Q; Kanashiro, Alexandre

    2016-08-01

    Recent studies have demonstrated that the central nervous system controls inflammatory responses by activating complex efferent neuroimmune pathways. The present study was designed to evaluate the role that central gamma-aminobutyric acid type B (GABA-B) receptor plays in neutrophil migration in a murine model of zymosan-induced arthritis by using different pharmacological tools. We observed that intrathecal administration of baclofen, a selective GABA-B agonist, exacerbated the inflammatory response in the knee after zymosan administration characterized by an increase in the neutrophil recruitment and knee joint edema, whereas saclofen, a GABA-B antagonist, exerted the opposite effect. Intrathecal pretreatment of the animals with SB203580 (an inhibitor of p38 mitogen-activated protein kinase) blocked the pro-inflammatory effect of baclofen. On the other hand, systemic administration of guanethidine, a sympatholytic drug that inhibits catecholamine release, and nadolol, a beta-adrenergic receptor antagonist, reversed the effect of saclofen. Moreover, saclofen suppressed the release of the pro-inflammatory cytokines into the knee joint (ELISA) and pain-related behaviors (open field test). Since the anti-inflammatory effect of saclofen depends on the sympathetic nervous system integrity, we observed that isoproterenol, a beta-adrenergic receptor agonist, mimics the central GABA-B blockade decreasing knee joint neutrophil recruitment. Together, these results demonstrate that the pharmacological manipulation of spinal GABAergic transmission aids control of neutrophil migration to the inflamed joint by modulating the activation of the knee joint-innervating sympathetic terminal fibers through a mechanism dependent on peripheral beta-adrenergic receptors and central components, such as p38 MAPK.

  12. GABA A receptor abnormalities in Prader-Willi syndrome assessed with positron emission tomography and [11C]flumazenil.

    PubMed

    Lucignani, Giovanni; Panzacchi, Andrea; Bosio, Laura; Moresco, Rosa Maria; Ravasi, Laura; Coppa, Isabella; Chiumello, Giuseppe; Frey, Kirk; Koeppe, Robert; Fazio, Ferruccio

    2004-05-01

    Prader-Willi syndrome (PWS) is a multi-system disorder characterized clinically by abnormal mental and physical development. PWS patients have a deletion in an imprinted region on paternal chromosome 15 (15q11-13), maternal disomy for this segment, or rarely, a chromosomal imprinting center deletion that gives rise to suppression of the equivalent paternal genes. Within the affected segment of chromosome 15 are genes encoding the alpha(5), beta(3) and gamma(3) subunits of the gamma-aminobutyric acid type-A (GABA(A)) receptor. Therefore, altered neurobehavioral function could arise in PWS due directly to altered GABA(A) receptor composition and expression, or alternatively, from brain developmental and maturational effects of these or other genes in the imprinted region. The aim of the present study was to assess cerebral GABA(A) receptors in PWS with the use of positron emission tomography of the benzodiazepine binding site employing [11C]flumazenil ([11C]FMZ). A reduction in [11C]FMZ binding was found predominantly in the cingulate, frontal and temporal neocortices and insula in six adult PWS patients compared to nine normal subjects. A possible role for the deleted beta(3) subunit gene in PWS is supported in part by the wide cortical distribution of its mRNA expression and the effects of experimental knockouts on benzodiazepine binding described in prior studies. Altered GABA(A) receptor composition or number in these cortical regions may account for neurobehavioral abnormalities in PWS including mild mental retardation, poor impulse control, and impaired responses to somatic pain.

  13. Arabidopsis aldehyde dehydrogenase 10 family members confer salt tolerance through putrescine-derived 4-aminobutyrate (GABA) production

    PubMed Central

    Zarei, Adel; Trobacher, Christopher P.; Shelp, Barry J.

    2016-01-01

    Polyamines represent a potential source of 4-aminobutyrate (GABA) in plants exposed to abiotic stress. Terminal catabolism of putrescine in Arabidopsis thaliana involves amine oxidase and the production of 4-aminobutanal, which is a substrate for NAD+-dependent aminoaldehyde dehydrogenase (AMADH). Here, two AMADH homologs were chosen (AtALDH10A8 and AtALDH10A9) as candidates for encoding 4-aminobutanal dehydrogenase activity for GABA synthesis. The two genes were cloned and soluble recombinant proteins were produced in Escherichia coli. The pH optima for activity and catalytic efficiency of recombinant AtALDH10A8 with 3-aminopropanal as substrate was 10.5 and 8.5, respectively, whereas the optima for AtALDH10A9 were approximately 9.5. Maximal activity and catalytic efficiency were obtained with NAD+ and 3-aminopropanal, followed by 4-aminobutanal; negligible activity was obtained with betaine aldehyde. NAD+ reduction was accompanied by the production of GABA and β-alanine, respectively, with 4-aminobutanal and 3-aminopropanal as substrates. Transient co-expression systems using Arabidopsis cell suspension protoplasts or onion epidermal cells and several organelle markers revealed that AtALDH10A9 was peroxisomal, but AtALDH10A8 was cytosolic, although the N-terminal 140 amino acid sequence of AtALDH10A8 localized to the plastid. Root growth of single loss-of-function mutants was more sensitive to salinity than wild-type plants, and this was accompanied by reduced GABA accumulation. PMID:27725774

  14. An investigation of the origin of extracellular GABA in rat nucleus accumbens measured in vivo by microdialysis.

    PubMed

    Smith, S E; Sharp, T

    1994-01-01

    GABA transmission in the nucleus accumbens is believed to play a central role in motivational processes and the expression of psychostimulant drug action. Here we report measurements of extracellular GABA in nucleus accumbens of the rat and investigate its origin. Extracellular GABA was detected using microdialysis in combination with a novel HPLC-based assay. In the awake rat, GABA in the microdialysates (1) increased 10-fold following perfusion with 0.5 mM nipecotic acid, a GABA releasing agent and uptake blocker, (2) increased 7-fold following local perfusion with 50 mM KCl, (3) decreased 50% following perfusion with tetrodotoxin, (4) decreased 50% following perfusion with a Ca(2+(-free medium and (5) decreased 40% following perfusion with high (12.5 mM) MgCl. Finally, in the anaesthetized rat, GABA in the microdialysates decreased 50% following i.p. injection of 100 mg/kg 3-mercaptoproprionic acid, a GABA synthesis inhibitor. We conclude that GABA in microdialysates from nucleus accumbens of the rat (awake) responds appropriately to selected pharmacological agents and derives at least in part (50%) from neurones.

  15. Aging of whiskey increases the potentiation of GABA(A) receptor response.

    PubMed

    Koda, Hirofumi; Hossain, Sheikh Julfikar; Kiso, Yoshinobu; Aoshima, Hitoshi

    2003-08-27

    It is known that the target of most mood-defining compounds such as ethanol is an ionotropic gamma-aminobutyric acid receptor (GABA(A) receptor). The potentiation of the response of these inhibitory neurotransmitter receptors induces anxiolytic, sedative, and anesthetic activities in the human brain. Because both extracts of whiskey by pentane and fragrant components in whiskey potentiate the GABA(A) receptor-mediated response, GABA(A) receptors were expressed in Xenopus oocyte by injecting cRNAs prepared from the cloned cDNA for the alpha(1) and beta(1) subunits of the bovine receptors in order to study the effects of whiskey itself on the GABA(A) receptor-mediated response. Whiskey itself also potentiated the electrical responses of GABA(A) receptors generally more than ethanol at the same concentration as that of the whiskey. The potentiation of the GABA(A) receptor-mediated response increased with the aging period of the whiskey. Inhalation of whiskey to mice increased the sleeping time induced by pentobarbital more than that of the same concentration of ethanol as the whiskey. These results suggest that not only ethanol but also minor components in whiskey play an important role in the potentiation of GABA(A) receptor-mediated response and possibly the sedative effect of whiskey. Although the minor components are present in extremely small quantities compared with ethanol in alcoholic beverages, they may modulate the mood or consciousness of humans through the potentiation of the GABA(A) receptor response after absorption into the brain, because these hydrophobic compounds are easily absorbed into the brain across the blood-brain barrier and are several thousands times as potent as ethanol in the potentiation of the GABA(A) receptor-mediated response.

  16. Microtransplantation of cellular membranes from squid stellate ganglion reveals ionotropic GABA receptors.

    PubMed

    Conti, Luca; Limon, Agenor; Palma, Eleonora; Miledi, Ricardo

    2013-02-01

    The squid has been the most studied cephalopod, and it has served as a very useful model for investigating the events associated with nerve impulse generation and synaptic transmission. While the physiology of squid giant axons has been extensively studied, very little is known about the distribution and function of the neurotransmitters and receptors that mediate inhibitory transmission at the synapses. In this study we investigated whether γ-aminobutyric acid (GABA) activates neurotransmitter receptors in stellate ganglia membranes. To overcome the low abundance of GABA-like mRNAs in invertebrates and the low expression of GABA in cephalopods, we used a two-electrode voltage clamp technique to determine if Xenopus laevis oocytes injected with cell membranes from squid stellate ganglia responded to GABA. Using this method, membrane patches containing proteins and ion channels from the squid's stellate ganglion were incorporated into the surface of oocytes. We demonstrated that GABA activates membrane receptors in cellular membranes isolated from squid stellate ganglia. Using the same approach, we were able to record native glutamate-evoked currents. The squid's GABA receptors showed an EC(50) of 98 μmol l(-1) to GABA and were inhibited by zinc (IC(50) = 356 μmol l(-1)). Interestingly, GABA receptors from the squid were only partially blocked by bicuculline. These results indicate that the microtransplantation of native cell membranes is useful to identify and characterize scarce membrane proteins. Moreover, our data also support the role of GABA as an ionotropic neurotransmitter in cephalopods, acting through chloride-permeable membrane receptors.

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

    PubMed

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

    2011-06-01

    There are conflicting data regarding whether activation of γ-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.

  18. The GABA(B) antagonist CGP 52432 attenuates the stimulatory effect of the GABA(B) agonist SKF 97541 on luteinizing hormone secretion in the male sheep.

    PubMed

    Jackson, Gary L; Kuehl, David

    2002-05-01

    The objectives of this study were to determine if the gamma-aminobutyric acid (GABA)(B) agonist, 3-aminopropyl (methyl) phosphinic acid (SKF97541), would increase luteinizing hormone (LH) secretion when infused by microdialysis into the medial basal hypothalamus (MBH) of the castrated ram, and to determine if the action of SKF97541 would be attenuated by co-infusion of the GABA(B) antagonist CGP52432. Initial experiments established that infusion of SKF alone, at concentrations as low as 5 microM, increased mean LH, LH pulse amplitude, and in some cases, pulse interval. In the last experiment, animals were treated with artificial cerebrospinal fluid (CSF) alone, SKF alone (30 microM), 3-[[(3, 4-dichlorophenol) methyl] amino] propyl] diethoxymethyl) phosphinic acid (CGP) alone (500 microM), or SKF plus CGP. SKF increased both mean LH and LH pulse amplitude as compared with CSF. CGP alone had no significant effect on LH, but it attenuated the effect of SKF on mean LH. These observations indicate that the stimulatory effects of GABA(B) agonists on LH pulse patterns are mediated through GABA(B) receptors and provide further evidence that GABA(B) receptors located in the MBH can regulate pulsatile GnRH-LH release.

  19. GABA and GAD expression in the X-organ sinus gland system of the Procambarus clarkii crayfish: inhibition mediated by GABA between X-organ neurons.

    PubMed

    Pérez-Polanco, Paola; Garduño, Julieta; Cebada, Jorge; Zarco, Natanael; Segovia, José; Lamas, Mónica; García, Ubaldo

    2011-09-01

    In crustaceans, the X-organ-sinus gland (XO-SG) neurosecretory system is formed of distinct populations of neurons that produce two families of neuropeptides: crustacean hyperglycemic hormone and adipokinetic hormone/red pigment-concentrating hormone. On the basis of electrophysiological evidence, it has been proposed that γ-aminobutyric acid (GABA) regulates both electrical and secretory activity of the XO-SG system. In this work we observed that depolarizing current pulses to neurons located in the external rim of the X-organ induced repetitive firing that suppressed the spontaneous firing of previously active X-organ neurons. Picrotoxin reversibly blocked this inhibitory effect suggesting that the GABA released from the stimulated neuron inhibited neighboring cells. Immunoperoxidase in X-organ serial sections showed co-localization of GABA and glutamic acid decarboxylase (GAD) including the aforementioned neurons. Immunofluorescence in whole mount preparations showed that two subpopulations of crustacean hyperglycemic hormone-containing neurons colocalized with GABA. The expression of GAD mRNA was determined in crayfish tissue and X-organ single cells by RT-PCR. Bioinformatics analysis shows, within the amplified region, 90.4% consensus and 41.9% identity at the amino acid level compared with Drosophila melanogaster and Caenorhabditis elegans. We suggest that crustacean hyperglycemic hormone-GABA-containing neurons can regulate the excitability of other X-organ neurons that produce different neurohormones.

  20. GABA-mediated effects of some taurine derivatives injected i.c.v. on rabbit rectal temperature and gross motor behavior.

    PubMed

    Frosini, M; Ricci, L; Saponara, S; Palmi, M; Valoti, M; Sgaragli, G

    2006-05-01

    Some synthetic taurine analogues, namely ethanolamine-O-sulphate (EOS), N,N-dimethyltaurine (DMT), N,N,N-trimethyltaurine (TMT) and 2-aminoethylphosphonic acid (AEP) were shown to interact with rabbit brain GABA(A)- or GABA(B)-receptors, while (+/-)piperidine-3-sulfonic acid (PSA) inhibited the activity of rabbit brain 4-aminobutyrate transaminase. This suggests that they behave like direct/indirect GABA agonists or GABA antagonists and affect thermoregulation and gross motor behaviour (GMB) which are under GABA control. In the present study micromole (1.2-48) amounts of these compounds were i.c.v. injected in conscious, restrained rabbits while monitoring rectal temperature (RT), ear skin temperature (EST) and GMB. AEP, EOS, DMT and TMT induced a dose-related hyperthermia, ear vasoconstriction and excitation of GMB, while PSA induced a dose-related hypothermia, ear vasodilation and inhibition of GMB. EOS antagonized in a dose-related fashion hypothermia induced by 60 nmol THIP, a GABA(A) agonist, while AEP, DMT and TMT counteracted that induced by 8 nmol R(-)Baclofen, a GABA(B) agonist. In conclusion, EOS and AEP, DMT, TMT seem to act as GABA(A) and GABA(B) antagonists, respectively, while PSA behaves like an indirect GABA agonist, all affecting the central mechanisms which drive rabbit thermoregulation.

  1. GABA actions in hippocampal area CA3 during postnatal development: differential shift from depolarizing to hyperpolarizing in somatic and dendritic compartments.

    PubMed

    Romo-Parra, Héctor; Treviño, Mario; Heinemann, Uwe; Gutiérrez, Rafael

    2008-03-01

    Gamma-aminobutyric acid type A receptor (GABA(A)-R) activation leads to depolarization of pyramidal cells during the first postnatal week and produces hyperpolarization from the second week. However, immunohistochemical evidence has suggested that during the second and third postnatal weeks the NKCC1 cotransporter relocates from the soma to the dendrites of CA3 pyramidal cells. We hypothesized that this leads to depolarizing responses in apical dendrites. Here we show that the activation of GABA(A)-R in the distal dendrites of CA3 pyramidal cells at P15 by restricted application of muscimol or synaptic activation by stimulation of interneurons in stratum radiatum (SR) causes depolarizing postsynaptic potentials (PSPs), which are blocked by NKCC1 cotransporter antagonists. By contrast, activation of proximal GABA(A)-R by muscimol application or by stimulation of interneurons in s. oriens (SO) leads to hyperpolarizing PSPs. Activation of the dentate gyrus (DG) in the presence of glutamatergic blockers evokes hyperpolarizing responses during the second postnatal week; however, the reversal potential of the DG-evoked inhibitory (I)PSPs is more depolarized than that of IPSPs evoked by activation of SO interneurons. Despite the shift of GABA action from depolarizing to hyperpolarizing, DG-evoked field potentials (f-PSPs) recorded in s. lucidum/radiatum (SL/R) do not change in polarity until the third week. Current source density analysis yielded results consistent with depolarizing actions of GABA in the dendritic compartment. Our data suggest that GABAergic input to apical dendrites of pyramidal cells of CA3 evokes depolarizing PSPs long after synaptic inhibition has become hyperpolarizing in the somata, in the axon initial segments and in basal dendrites.

  2. Contribution of metabotropic GABA(B) receptors to neuronal network construction.

    PubMed

    Gaiarsa, Jean-Luc; Kuczewski, Nicola; Porcher, Christophe

    2011-11-01

    In the 1980s, Bowery and colleagues discovered the presence of a novel, bicuculline-resistant and baclofen-sensitive type of GABA receptor on peripheral nerve terminals, the GABA(B) receptor. Since this pioneering work, GABA(B) receptors have been identified in the Central Nervous System (CNS), where they provide an important inhibitory control of postsynaptic excitability and presynaptic transmitter release. GABA(B) receptors have been implicated in a number of important processes in the adult brain such as the regulation of synaptic plasticity and modulation of rhythmic activity. As a result of these studies, several potential therapeutic applications of GABA(B) receptor ligands have been identified. Recent advances have further shown that GABA(B) receptors play more than a classical inhibitory role in adult neurotransmission, and can in fact function as an important developmental signal early in life. Here we summarize current knowledge on the contribution of GABA(B) receptors to the construction and function of developing neuronal networks.

  3. GABA withdrawal syndrome: GABAA receptor, synapse, neurobiological implications and analogies with other abstinences.

    PubMed

    Calixto, E

    2016-01-28

    The sudden interruption of the increase of the concentration of the gamma-aminobutyric acid (GABA), determines an increase in neuronal activity. GABA withdrawal (GW) is a heuristic analogy, with withdrawal symptoms developed by other GABA receptor-agonists such as alcohol, benzodiazepines, and neurosteroids. GW comprises a model of neuronal excitability validated by electroencephalogram (EEG) in which high-frequency and high-amplitude spike-wave complexes appear. In brain slices, GW was identified by increased firing synchronization of pyramidal neurons and by changes in the active properties of the neuronal membrane. GW induces pre- and postsynaptic changes: a decrease in GABA synthesis/release, and the decrease in the expression and composition of GABAA receptors associated with increased calcium entry into the cell. GW is an excellent bioassay for studying partial epilepsy, epilepsy refractory to drug treatment, and a model to reverse or prevent the generation of abstinences from different drugs.

  4. "Brain MR spectroscopy in autism spectrum disorder-the GABA excitatory/inhibitory imbalance theory revisited".

    PubMed

    Brix, Maiken K; Ersland, Lars; Hugdahl, Kenneth; Grüner, Renate; Posserud, Maj-Britt; Hammar, Åsa; Craven, Alexander R; Noeske, Ralph; Evans, C John; Walker, Hanne B; Midtvedt, Tore; Beyer, Mona K

    2015-01-01

    Magnetic resonance spectroscopy (MRS) from voxels placed in the left anterior cingulate cortex (ACC) was measured from 14 boys with Autism Spectrum Disorder (ASD) and 24 gender and age-matched typically developing (TD) control group. Our main aims were to compare the concentration of γ-aminobutyric acid (GABA) between the two groups, and to investigate the relationship between brain metabolites and autism symptom severity in the ASD group. We did find a significant negative correlation in the ASD group between Autism Spectrum Screening Questionnaire (ASSQ) and GABA+/Cr, which may imply that severity of symptoms in ASD is associated with differences in the level of GABA in the brain, supporting the excitatory/inhibitory (E/I) imbalance theory. However we did not find a significant difference between the two groups in GABA levels.

  5. Excitatory actions of gaba during development: the nature of the nurture.

    PubMed

    Ben-Ari, Yehezkel

    2002-09-01

    In the immature brain, GABA (gamma-aminobutyric acid) is excitatory, and GABA-releasing synapses are formed before glutamatergic contacts in a wide range of species and structures. GABA becomes inhibitory by the delayed expression of a chloride exporter, leading to a negative shift in the reversal potential for choride ions. I propose that this mechanism provides a solution to the problem of how to excite developing neurons to promote growth and synapse formation while avoiding the potentially toxic effects of a mismatch between GABA-mediated inhibition and glutamatergic excitation. As key elements of this cascade are activity dependent, the formation of inhibition adds an element of nurture to the construction of cortical networks.

  6. Some dipeptides reverse the inhibitory effect of GABA on /sup 35/S-TBPS binding

    SciTech Connect

    Squires, R.F.; Saederup, E.

    1987-05-01

    All known GABA-A receptor blocker reverse the inhibitory effect of GABA on /sup 35/S-t-butylphosphorothionate (TBPS) binding to rat brain membranes in vitro. This system has already been used to identify several novel GABA antagonists. The authors now report that 12 out of 52 dipeptides tested (all containing L-amino acids), at 1 mM, significantly reverse the inhibitory effect of 1 ..mu..M GABA, which inhibits specific /sup 35/S-TBPS binding about 60%. Most of the active dipeptides contain an aromatic and a basic amino acid. Tryptophan usually conferred greater activity than phe or tyr, while arg usually conferred greater activity than lys or his. Several larger peptides containing the HFRW sequence found in ACTH were also GABA antagonists; ACTH(1-24), ACTH(1-18), ACTH(1-13), ACTH(4-10) and ..gamma..-MSH while ACTH(11-24) was inactive. The excitatory effects of these later peptides may be in part due to blockade of GABA-A receptors.

  7. Betulin binds to gamma-aminobutyric acid receptors and exerts anticonvulsant action in mice.

    PubMed

    Muceniece, Ruta; Saleniece, Kristine; Rumaks, Juris; Krigere, Liga; Dzirkale, Zane; Mezhapuke, Rudolfs; Zharkova, Olga; Klusa, Vija

    2008-10-01

    The lupane type pentacyclic triterpenes: lupeol, betulin, and betulinic acid are widely distributed natural compounds. Recently, pharmaceutical compositions from plant extracts (family Marcgraviaceae) containing betulinic acid, have been patented as anxiolytic remedies. To extend our knowledge of the CNS effects of the triterpenes, we suggest here that the chemically related lupeol, betulin and betulinic acid may interact with the brain neurotransmitter gamma-aminobutyric acid (GABA) receptors in vitro and in vivo. Using radioligand receptor-binding assay, we showed that only betulin bound to the GABA(A)-receptor sites in mice brain in vitro and antagonised the GABA(A)-receptor antagonist bicuculline-induced seizures in mice after intracisternal and intraperitoneal administration. Neither betulinic acid nor lupeol bound to GABA(A) receptor nor did they inhibit bicuculline-induced seizures in vivo. These findings demonstrate for the first time the CNS effects of betulin in vivo, and they also show distinct GABA(A)-receptor-related properties of lupane type triterpenes. These findings may open new avenues in understanding the central effects of betulin, and they also indicate possibilities for novel drug design on the basis of betulin structure.

  8. mRNA and Protein Levels for GABA[subscript A][alpha]4, [alpha]5, [beta]1 and GABA[subscript B]R1 Receptors are Altered in Brains from Subjects with Autism

    ERIC Educational Resources Information Center

    Fatemi, S. Hossein; Reutiman, Teri J.; Folsom, Timothy D.; Rooney, Robert J.; Patel, Diven H.; Thuras, Paul D.

    2010-01-01

    We have shown altered expression of gamma-aminobutyric acid A (GABA[subscript A]) and gamma-aminobutyric acid B (GABA[subscript B]) receptors in the brains of subjects with autism. In the current study, we sought to verify our western blotting data for GABBR1 via qRT-PCR and to expand our previous work to measure mRNA and protein levels of 3…

  9. Prefrontal Cortical GABA Abnormalities Are Associated With Reduced Hippocampal Volume In Major Depressive Disorder

    PubMed Central

    Abdallah, Chadi G.; Jackowski, Andrea; Sato, João R.; Mao, Xiangling; Kang, Guoxin; Cheema, Raminder; Coplan, Jeremy D.; Mathew, Sanjay J.; Shungu, Dikoma C.

    2015-01-01

    Hippocampal volume reduction has been related to treatment-resistant depression (TRD) and is hypothesized to reflect impaired amino-acid neurotransmission. To better understand the role of amino acid neurotransmission in hippocampal volume deficits, and subsequent resistance to treatment, this study investigated the relationship between hippocampal volumes and GABA levels in the anterior cingulate cortex (ACC), previously associated with TRD. Thirty-three medication-free major depressive disorder (MDD; 14 TRD and 19 non-TRD) and 26 healthy controls (HC) subjects were studied. Participants underwent high-resolution magnetic resonance imaging (MRI) to estimate hippocampal volume and proton MR spectroscopy (1H MRS) to measure ACC GABA levels. MDD patients, with known ACC GABA levels, were divided into two groups: MDD Low GABA and MDD High GABA. We found a significant reduction in hippocampal volume in the MDD Low GABA group compared to MDD High GABA (p < 0.001) and HC (p = 0.01). The relationship between hippocampal volume and cortical GABA was population (i.e. MDD group) and region specific (i.e. prefrontal cortex). Comparing TRD, non-TRD and HC groups, there was a main effect of group on hippocampal volume (p = 0.04), which post hoc analysis revealed as smaller hippocampal volume in TRD subjects than in non-TRD (p = 0.05) and HC groups (p = 0.03). No hippocampal volume differences between non-TRD and HC groups. The data provides insight into the role of prefrontal neurochemical deficits in the limbic structural abnormalities observed in MDD. In addition, it replicates the relationship between TRD and smaller hippocampal volumes. PMID:25983019

  10. Characterising the role of GABA and its metabolism in the wheat pathogen Stagonospora nodorum.

    PubMed

    Mead, Oliver; Thynne, Eli; Winterberg, Britta; Solomon, Peter S

    2013-01-01

    A reverse genetics approach was used to investigate the role of γ-aminobutyric acid metabolism in the wheat pathogenic fungus Stagonospora nodorum. The creation of mutants lacking Sdh1, the gene encoding succinic semialdehyde dehydrogenase, resulted in strains that grew poorly on γ-aminobutyric acid as a nitrogen source. The sdh1 mutants were more susceptible to reactive oxygen stress but were less affected by increased growth temperatures. Pathogenicity assays revealed that the metabolism of γ-aminobutyric acid is required for complete pathogenicity. Growth assays of the wild-type and mutant strains showed that the inclusion of γ-aminobutyric acid as a supplement in minimal media (i.e., not as a nitrogen or carbon source) resulted in restricted growth but increased sporulation. The addition of glutamate, the precursor to GABA, had no effect on either growth or sporulation. The γ-aminobutyric acid effect on sporulation was found to be dose dependent and not restricted to Stagonospora nodorum with a similar effect observed in the dothideomycete Botryosphaeria sp. The positive effect on sporulation was assayed using isomers of γ-aminobutyric acid and other metabolites known to influence asexual development in Stagonospora nodorum but no effect was observed. These data demonstrate that γ-aminobutyric acid plays an important role in Stagonospora nodorum in responding to environmental stresses while also having a positive effect on asexual development.

  11. Functional characterization of the 1,5-benzodiazepine clobazam and its major active metabolite N-desmethylclobazam at human GABA(A) receptors expressed in Xenopus laevis oocytes.

    PubMed

    Hammer, Harriet; Ebert, Bjarke; Jensen, Henrik Sindal; Jensen, Anders A

    2015-01-01

    The 1,5-benzodiazepine clobazam is indicated for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients 2 years of age or older in the United States, and for treatment of anxiety and various forms of epilepsy elsewhere. Clobazam has been reported to exhibit different in vivo adverse effects and addiction liability profile than the classic 1,4-benzodiazepines. In this study, it was investigated whether the in vitro pharmacological properties of clobazam and its major active metabolite N-desmethylclobazam could explain some of these clinical differences. The functional properties of the two 1,5-benzodiazepines were characterized at the human γ-aminobutyric acid type A receptor (GABA(A)R) subtypes α1β2γ(2S), α2β2γ(2S), α3β2γ(2S), α5β2γ(2S) and α6β2δ expressed in Xenopus laevis oocytes by use of two-electrode voltage-clamp electrophysiology and compared to those exhibited by the 1,4-benzodiazepine clonazepam. All three compounds potentiated GABA EC20-evoked responses through the α(1,2,3,5)β2γ(2S) GABA(A)Rs in a reversible and concentration-dependent manner, with each displaying similar EC50 values at the four subtypes. Furthermore, the degrees of potentiation of the GABA EC20 currents through the four receptors mediated by saturating modulator concentrations did not differ substantially for any of the three benzodiazepines. The three compounds were substantially less potent (200-3900 fold) as positive allosteric modulators at the α6β2δ GABA(A)R than at the α(1,2,3,5)β2γ(2S) receptors. Interestingly, however, clobazam and especially N-desmethylclobazam were highly efficacious potentiators of α6β2δ receptor signaling. Although this activity component is unlikely to contribute to the in vivo effects of clobazam/N-desmethylclobazam, the 1,5-benzodiazepine could constitute an interesting lead for novel modulators targeting this low-affinity binding site in GABAARs. In conclusion, the non-selective modulation

  12. Interaction of humic acids and humic-acid-like polymers with herpes simplex virus type 1

    NASA Astrophysics Data System (ADS)

    Klöcking, Renate; Helbig, Björn

    The study was performed in order to compare the antiviral activity against herpes simplex virus type 1 (HSV-1) of synthetic humic-acid-like polymers to that of their low-molecular-weight basic compounds and naturally occurring humic acids (HA) in vitro. HA from peat water showed a moderate antiviral activity at a minimum effective concentration (MEC) of 20 µg/ml. HA-like polymers, i.e. the oxidation products of caffeic acid (KOP), hydrocaffeic acid (HYKOP), chlorogenic acid (CHOP), 3,4-dihydroxyphenylacetic acid (3,4-DHPOP), nordihydroguaretic acid (NOROP), gentisinic acid (GENOP), pyrogallol (PYROP) and gallic acid (GALOP), generally inhibit virus multiplication, although with different potency and selectivity. Of the substances tested, GENOP, KOP, 3,4-DHPOP and HYKOP with MEC values in the range of 2 to 10 µg/ml, proved to be the most potent HSV-1 inhibitors. Despite its lower antiviral potency (MEC 40 µg/ml), CHOP has a remarkable selectivity due to the high concentration of this polymer that is tolerated by the host cells (>640 µg/ml). As a rule, the antiviral activity of the synthetic compounds was restricted to the polymers and was not preformed in the low-molecular-weight basic compounds. This finding speaks in favour of the formation of antivirally active structures during the oxidative polymerization of phenolic compounds and, indirectly, of corresponding structural parts in different HA-type substances.

  13. 5-(N, N-Hexamethylene) amiloride is a GABA-A ρ1 receptor positive allosteric modulator.

    PubMed

    Snell, Heather D; Gonzales, Eric B

    2016-11-01

    Guanidine compounds act as ion channel modulators. In the case of Cys-loop receptors, the guanidine compound amiloride antagonized the heteromeric GABA-A, glycine, and nicotinic acetylcholine receptors. However, amiloride exhibits characteristics consistent with a positive allosteric modulator for the human GABA-A (hGABA-A) ρ1 receptor. Site-directed mutagenesis revealed that the positive allosteric modulation was influenced by the GABA-A ρ1 second transmembrane domain 15' position, a site implicated in ligand allosteric modulation of Cys-loop receptors. There are a variety of amiloride derivatives that provide opportunities to assess the significance of amiloride functional groups (e.g., the guanidine group, the pyrazine ring, etc.) in the modulation of the GABA-A ρ1 receptor activity. We utilized 3 amiloride derivatives (benzamil, phenamil, and 5-(N, N-Hexamethylene) amiloride) to assess the contribution of these groups toward the potentiation of the GABA-A ρ1 receptor. Benzamil and phenamil failed to potentiate on the wild type GABA-A ρ1 GABA-mediated current while HMA demonstrated efficacy only at the highest concentration studied. The hGABA-A ρ1 (I15'N) mutant receptor activity was potentiated by lower HMA concentrations compared to the wild type receptor. Our findings suggest that an exposed guanidine group on amiloride and amiloride derivatives is critical for modulating the GABA-A ρ1 receptor. The present study provides a conceptual framework for predicting which amiloride derivatives will demonstrate positive allosteric modulation of the GABA-A ρ1 receptor.

  14. Structure, function, and plasticity of GABA transporters

    PubMed Central

    Scimemi, Annalisa

    2014-01-01

    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. PMID:24987330

  15. GABA localization in the nematode Ascaris

    SciTech Connect

    Guastella, J.

    1988-01-01

    A histochemical approach was used to examine the distribution of GABA-associated neurons in the nematode Ascaris, an organism whose small number of morphologically simple neurons make it an excellent preparation for analyzing neuronal phenotypes. Two GABAergic markers were examined: GABA-like immunoreactivity (GLIR), a marker for endogenous stores of GABA; and ({sup 3}H)-GABA uptake, a marker for GABA uptake sites. Strong GLIR was present in the cell bodies, neurites and commissures of dorsal and ventral inhibitory motorneurons present in this region. Strong GLIR was also present in the cell bodies and processes of the four RME neurons in the nerve ring and in several other ganglionic neurons. Staining was absent in excitatory motorneurons, in ventral cord interneurons and in muscle cells and hypodermis. GABA uptake sites were found in single neural processes in both the ventral and dorsal nerve cords. ({sup 3}H)-GABA labeling was also observed in the other two RME cells and several other cephalic neurons. Four putative cholinergic excitatory motorneurons in the retrovesicular ganglion (RVG) were heavily labeled. Ventral and dorsal nerve cord inhibitory motorneurons did not take up ({sup 3}H)-GABA. Labeling of the ventral cord excitatory motorneuron somata and cell bodies was at or slightly above background. Heavy labeling of muscle cells was also observed.

  16. Co-activation of VTA DA and GABA neurons mediates nicotine reinforcement.

    PubMed

    Tolu, S; Eddine, R; Marti, F; David, V; Graupner, M; Pons, S; Baudonnat, M; Husson, M; Besson, M; Reperant, C; Zemdegs, J; Pagès, C; Hay, Y A H; Lambolez, B; Caboche, J; Gutkin, B; Gardier, A M; Changeux, J-P; Faure, P; Maskos, U

    2013-03-01

    Smoking is the most important preventable cause of mortality and morbidity worldwide. This nicotine addiction is mediated through the nicotinic acetylcholine receptor (nAChR), expressed on most neurons, and also many other organs in the body. Even within the ventral tegmental area (VTA), the key brain area responsible for the reinforcing properties of all drugs of abuse, nicotine acts on several different cell types and afferents. Identifying the precise action of nicotine on this microcircuit, in vivo, is important to understand reinforcement, and finally to develop efficient smoking cessation treatments. We used a novel lentiviral system to re-express exclusively high-affinity nAChRs on either dopaminergic (DAergic) or γ-aminobutyric acid-releasing (GABAergic) neurons, or both, in the VTA. Using in vivo electrophysiology, we show that, contrary to widely accepted models, the activation of GABA neurons in the VTA plays a crucial role in the control of nicotine-elicited DAergic activity. Our results demonstrate that both positive and negative motivational values are transmitted through the dopamine (DA) neuron, but that the concerted activity of DA and GABA systems is necessary for the reinforcing actions of nicotine through burst firing of DA neurons. This work identifies the GABAergic interneuron as a potential target for smoking cessation drug development.

  17. GABA A receptor π subunit promotes apoptosis of HTR-8/SVneo trophoblastic cells: Implications in preeclampsia.

    PubMed

    Lu, Junjie; Zhang, Qian; Tan, Dongmei; Luo, Wenping; Zhao, Hai; Ma, Jing; Liang, Hao; Tan, Yi

    2016-07-01

    Gamma-aminobutyric acid (GABA) functions primarily as an inhibitory neurotransmitter through its receptors in the mature central nervous system. The GABA type A receptor π subunit (GABRP) has been identified in the tissues of the reproductive system, particularly in the uterus. In addition, we have previously detected GABRP expression in both human and mouse placentas. To examine the role of GABRP in trophoblastic cell invasion, we constructed a pIRES2-GABRP-EGFP plasmid which was used for the transfection of a human placental cell line derived from first trimester extravillous trophoblasts (HTR-8/SVneo). The number of invaded cells was decreased by GABRP overexpression. Notably, the decrease in the invasive cell number may be due to the increased apoptosis of the HTR-8/SVneo cells following GABRP transfection, which was further confirmed by flow cytometry, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Based on the increased apoptosis of trophoblastic cells in pregnancies complicated by preeclampsia (PE) and the fact that GABRP promotes the apoptosis of trophoblastic cells, we hypothesized that GABRP expression is increased in the placental tissues from patients with PE compared with that in the normal groups and this hypothesis was confirmed by RT-qPCR and immunohistochemical analysis. Taken together, these findings imply that GABRP plays an important role in placentation and this pathway may be a promising molecular target for the development of novel therapeutic strategies for PE.

  18. Extracellular glutamate increases in the lateral hypothalamus during meal initiation, and GABA peaks during satiation: microdialysis measurements every 30 s.

    PubMed

    Rada, Pedro; Mendialdua, Ainhoa; Hernandez, Luis; Hoebel, Bartley G

    2003-04-01

    Glutamate injected into the lateral hypothalamus can initiate eating, and gamma-aminobutyric acid (GABA) can stop it. This leads to the hypothesis that glutamate inputs are active at the beginning of a meal, and GABA is released at the end. To test this theory, the authors used microdialysis to sample glutamate and GABA simultaneously before, during, and after a meal. Food-deprived rats ate a meal of chow. Glutamate increased during the first third of the meal, then decreased to below baseline while the rats were still eating. GABA also increased at the start of the meal but continued rising and peaked during the last third of the meal. Glutamate may drive a hypothalamic system for eating, and GABA may oppose it.

  19. A possible role of the non-GAT1 GABA transporters in transfer of GABA from GABAergic to glutamatergic neurons in mouse cerebellar neuronal cultures.

    PubMed

    Suñol, C; Babot, Z; Cristòfol, R; Sonnewald, U; Waagepetersen, H S; Schousboe, A

    2010-09-01

    Cultures of dissociated cerebellum from 7-day-old mice were used to investigate the mechanism involved in synthesis and cellular redistribution of GABA in these cultures consisting primarily of glutamatergic granule neurons and a smaller population of GABAergic Golgi and stellate neurons. The distribution of GAD, GABA and the vesicular glutamate transporter VGlut-1 was assessed using specific antibodies combined with immunofluorescence microscopy. Additionally, tiagabine, SKF 89976-A, betaine, beta-alanine, nipecotic acid and guvacine were used to inhibit the GAT1, betaine/GABA (BGT1), GAT2 and GAT3 transporters. Only a small population of cells were immuno-stained for GAD while many cells exhibited VGlut-1 like immuno-reactivity which, however, never co-localized with GAD positive neurons. This likely reflects the small number of GABAergic neurons compared to the glutamatergic granule neurons constituting the majority of the cells. GABA uptake exhibited the kinetics of high affinity transport and could be partly (20%) inhibited by betaine (IC(50) 142 microM), beta-alanine (30%) and almost fully (90%) inhibited by SKF 89976-A (IC(50) 0.8 microM) or nipecotic acid and guvacine at 1 mM concentrations (95%). Essentially all neurons showed GABA like immunostaining albeit with differences in intensity. The results indicate that GABA which is synthesized in a small population of GAD-positive neurons is redistributed to essentially all neurons including the glutamatergic granule cells. GAT1 is not likely involved in this redistribution since addition of 15 microM tiagabine (GAT1 inhibitor) to the culture medium had no effect on the overall GABA content of the cells. Likewise the BGT1 transporter cannot alone account for the redistribution since inclusion of 3 mM betaine in the culture medium had no effect on the overall GABA content. The inhibitory action of beta-alanine and high concentrations of nipecotic acid and guvacine on GABA transport strongly suggests that also

  20. Cortical GABA Levels in Primary Insomnia

    PubMed Central

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

    2012-01-01

    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. PMID:22654200

  1. Presynaptic modulating effects of GABA on depression, facilitation, and posttetanic potentiation of a cholinergic synapse in Aplysia californica.

    PubMed

    Tremblay, J P; Plourde, G

    1977-12-01

    The effects of gamma-aminobutyric acid (GABA) have been studied on the synaptic depression, frequency facilitation, and posttetanic potentiation (PTP) of a unitary, monosynaptic, and presumably cholinergic excitatory postsynaptic potential (EPSP). This EPSP, produced by minimal stimulation of the right visceropleural connective, was recorded in cell R 15 of Aplysia californica. Perfusion with GABA (10(-4)-10(-3) M) reduces the size of all EPSPs produced by a train of 100 stimuli at 1/s. It also reduced the synaptic depression and PTP, and increases the frequency facilitation seen during the train. GABA does not significantly effect the membrane resistance (mean 102%) but it slightly depolarizes (mean 6 mV) the postsynaptic cell. GABA does not reduce an acetylcholine iontophoretic potential produced on R15. The effects of GABA are reduction when chloride is replaced by acetate but they remain significant. Picrotoxin and bicuculline fail to antagonize GABA. Addition of sodium azide or dinitrophenol does not reduce the action of GABA and even prolongs it. The effects of GABA are attributed to two sites of action: a postsynaptic one, responsible for the small change in potential and partially responsible for the reduction of EPSP size; and a presynaptic one, responsible for a further reduction of EPSP size and the changes of depression, facilitation, and PTP.

  2. Interaction between taurine and GABA(A)/glycine receptors in neurons of the rat anteroventral cochlear nucleus.

    PubMed

    Song, Ning-Ying; Shi, Hai-Bo; Li, Chun-Yan; Yin, Shan-Kai

    2012-09-07

    Taurine, one of the most abundant endogenous amino acids in the mammalian central nervous system (CNS), is involved in neural development and many physiological functions. In this study, the interaction between taurine and GABA(A)/glycine receptors was investigated in young rat (P13-P15) anteroventral cochlear nucleus (AVCN) neurons using the whole-cell patch-clamp method. We found that taurine at low (0.1mM) and high (1mM) concentrations activated both GABA(A) and glycine receptors, but not AMPA and NMDA receptors. The reversal potentials of taurine-, GABA- or glycine-evoked currents were close to the expected chloride equilibrium potential, indicating that receptors activated by these agonists were mediating chloride conductance. Moreover, our results showed that the currents activated by co-application of GABA and glycine were cross-inhibitive. Sequential application of GABA and glycine or vice versa also reduced the glycine or GABA evoked currents. There was no cross-inhibition when taurine and GABA or taurine and glycine were applied simultaneously, but the response was larger than that evoked by GABA or glycine alone. These results suggest that taurine can serve as a neuromodulator to strengthen GABAergic and glycinergic neurotransmission in the rat AVCN.

  3. Characterization of GABA/sub A/ receptor-mediated /sup 36/chloride uptake in rat brain synaptoneurosomes

    SciTech Connect

    Luu, M.D.; Morrow, A.L.; Paul, S.M.; Schwartz, R.D.

    1987-09-07

    ..gamma..-Aminobutyric acid (GABA) receptor-mediated /sup 36/chloride (/sup 36/Cl/sup -/) uptake was measured in synaptoneurosomes from rat brain. GABA and GABA agonists stimulated /sup 36/Cl/sup -/ uptake in a concentration-dependent manner with the following order of potency: Muscimol>GABA>piperidine-4-sulfonic acid (P4S)>4,5,6,7-tetrahydroisoxazolo-(5,4-c)pyridin-3-ol (THIP)=3-aminopropanesulfonic acid (3APS)>>taurine. Both P4S and 3APS behaved as partial agonists, while the GABA/sub B/ agonist, baclofen, was ineffective. The response to muscimol was inhibited by bicuculline and picrotoxin in a mixed competitive/non-competitive manner. Other inhibitors of GABA receptor-opened channels or non-neuronal anion channels such as penicillin, picrate, furosemide and disulfonic acid stilbenes also inhibited the response to muscimol. A regional variation in muscimol-stimulated /sup 36/Cl/sup -/ uptake was observed; the largest responses were observed in the cerebral cortex, cerebellum and hippocampus, moderate responses were obtained in the striatum and hypothalamus and the smallest response was observed in the pons-medulla. GABA receptor-mediated /sup 36/Cl/sup -/ uptake was also dependent on the anion present in the media. The muscinol response varied in media containing the following anions: Br/sup -/>Cl/sup -/greater than or equal toNO/sub 3//sup -/>I/sup -/greater than or equal toSCN/sup -/>>C/sub 3/H/sub 5/OO/sup -/greater than or equal toClO/sub 4//sup -/>F/sup -/, consistent with the relative anion permeability through GABA receptor-gated anion channels and the enhancement of convulsant binding to the GABA receptor-gated Cl/sup -/ channel. 43 references, 4 figures, 3 tables.

  4. A Cysteine Substitution Probes β3H267 Interactions with Propofol and Other Potent Anesthetics in α1β3γ2L Gamma-Aminobutyric Acid Type A Receptors

    PubMed Central

    Stern, Alex T.; Forman, Stuart A.

    2015-01-01

    Background Anesthetic contact residues in γ-aminobutyric acid type A (GABAA) receptors have been identified using photolabels, including two propofol derivatives. O-propofol-diazirine labels H267 in β3 and α1β3 receptors, while m-azi-propofol labels other residues in intersubunit clefts of α1β3. Neither label has been studied in αβγ receptors, the most common isoform in mammalian brain. In αβγ receptors, other anesthetic derivatives photolabel m-azi-propofol labeled residues, but not βH267. Our structural homology model of α1β3γ2L receptors suggests that β3H267 may abut some of these sites. Methods Substituted cysteine modification-protection was used to test β3H267C interactions with four potent anesthetics: propofol, etomidate, alphaxalone, and R-5-allyl-1-methyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid (mTFD-MPAB). We expressed α1β3γ2L or α1β3H267Cγ2L GABAA receptors in Xenopus oocytes. We used voltage clamp electrophysiology to assess receptor sensitivity to GABA and anesthetics, and to compare para-chloromercuribenzenesulfonate (pCMBS) modification rates with GABA versus GABA plus anesthetics. Results Enhancement of GABA EC5 responses by equi-hypnotic concentrations of all four anesthetics was similar in α1β3γ2L and α1β3H267Cγ2L receptors (n ≥ 3). Direct activation of α1β3H267Cγ2L receptors, but not α1β3γ2L, by mTFD-MPAB and propofol was significantly greater than the other anesthetics. Modification of β3H267C by pCMBS (n ≥ 4) was rapid and accelerated by GABA. Only mTFD-MPAB slowed β3H267C modification (~2-fold; p = 0.011). Conclusions β3H267 in α1β3γ2L GABAA receptors contacts mTFD-MPAB, but not propofol. Our results suggest that β3H267 is near the periphery of one or both transmembrane inter-subunit (α+/β− and γ+/β−) pockets where both mTFD-MPAB and propofol bind. PMID:26569173

  5. Glutamate, GABA, glycine and taurine modulate serotonin synthesis and release in rostral and caudal rhombencephalic raphe cells in primary cultures.

    PubMed

    Becquet, D; Hery, M; Francois-Bellan, A M; Giraud, P; Deprez, P; Faudon, M; Fache, M P; Hery, F

    1993-09-01

    Control of serotonin release and synthesis by amino acid neurotransmitters was investigated in rat rostral and caudal rhombencephalic raphe cells in primary cultures respectively. Endogenous amounts of taurine, glycine, GABA and glutamate were measured in both types of cultures. These amino acids were spontaneously released to the incubating medium. Exogenous taurine (10(-4) M) inhibited release and synthesis of newly formed [3H]serotonin [3H]5-HT from [3H]-tryptophan only in rostral raphe cells. Glycine (10(-3) M) decreased [3H]5-HT release in both types of cells, synthesis being diminished only in rostral raphe cells. Glycine inhibitory effect was totally blocked by strychnine (5 x 10(-5) M). GABA (10(-4) M) reduced [3H]5-HT metabolism in rostral as well as caudal raphe cells. This effect was totally antagonized in caudal and partially in rostral raphe cells by bicuculline (5 x 10(-5) M) a GABAA receptor antagonist. Baclofen (5 x 10(-5) M), a GABAB receptor agonist, induced a decrease of 5-HT release in rostral raphe cells. These observations suggest that monoamine release was entirely mediated by GABAA receptors in caudal raphe cells although GABAA and GABAB receptors were involved in control of 5-HT metabolism in rostral raphe cells. L-glutamate (10(-4) M) stimulated 5-HT metabolism in both types of cells, effect totally blocked by PK26124 (10(-6) M). N-methyl-D-aspartate (10(-4) M) enhanced 5-HT metabolism and the induced-effect was antagonized by the selective N-methyl-D-aspartate receptor antagonist D,L-2 amino-5-phosphonovaleric acid. Quisqualate (10(-5) M) stimulated [3H]5-HT release only in caudal raphe cells. This effect was mimicked by (RS)-a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, a quisqualate "ionotropic" receptor agonist, this increase being blocked by 6,7-dinitroquinoxaline 2,3-dione. These observations suggest that the glutamate stimulating-induced effect on serotonin metabolism is entirely mediated by N-methyl-D-aspartate receptor-type

  6. GABA-ergic Cell Therapy for Epilepsy: Advances, Limitations and Challenges

    PubMed Central

    Shetty, Ashok K.; Upadhya, Dinesh

    2016-01-01

    Diminution in the number of gamma-amino butyric acid positive (GABA-ergic) interneurons and their axon terminals, and/or alterations in functional inhibition are conspicuous brain alterations believed to contribute to the persistence of seizures in acquired epilepsies such as temporal lobe epilepsy. This has steered a perception that replacement of lost GABA-ergic interneurons would improve inhibitory synaptic neurotransmission in the epileptic brain region and thereby reduce the occurrence of seizures. Indeed, studies using animal prototypes have reported that grafting of GABA-ergic progenitors derived from multiple sources into epileptic regions can reduce seizures. This review deliberates recent advances, limitations and challenges concerning the development of GABA-ergic cell therapy for epilepsy. The efficacy and limitations of grafts of primary GABA-ergic progenitors from the embryonic lateral ganglionic eminence and medial ganglionic eminence (MGE), neural stem/progenitor cells expanded from MGE, and MGE-like progenitors generated from human pluripotent stem cells for alleviating seizures and co-morbidities of epilepsy are conferred. Additional studies required for possible clinical application of GABA-ergic cell therapy for epilepsy are also summarized. PMID:26748379

  7. GABA induced changes in acetylcholine release from slices of guinea-pig brain.

    PubMed

    Bianchi, C; Tanganelli, S; Marzola, G; Beani, L

    1982-03-01

    The effect of GABA on acetylcholine (ACh) release was investigated on superfused slices of guinea-pig cerebral cortex (CC), caudate nucleus (CN), tuberculum olfactorium and brain stem. GABA (1--6 x 10(-3) mol/l) increased the spontaneous and KCl-evoked ACh overflow in CC and CN, reduced the electrically-evoked release in all areas tested (most evidently in CC and CN) and lowered the threshold of electric stimulation-induced ACh release in CC. These effects were also caused by 3-amino-1-propane sulphonic acid (1 x 10(-3) mol/l) and ethanolamine-O-sulphate (2 x 10(-3) mol/l), were reduced by bicuculline (1 x 10(-4) mol/l) and fully antagonized by picrotoxin (8 x 10(-5) mol/l), but they were not influenced by phentolamine, methysergide, spiroperidol or strychnine. Tetrodotoxin (TTX) (5 x 10(-7) mol/l) blocked the facilitation of spontaneous ACh release by GABA only when the slices were perfused with normal Krebs solution, but not when perfused with a KCl-enriched medium. These results suggest that GABA affects the cholinergic transmitter release through bicuculline- and picrotoxin-sensitive receptors, showing low affinity toward the agonist. Moreover GABA modulation of resting ACh release requires action potentials only in normal [K+]0, but not in high [K+]0, suggesting that GABA-receptive sites are located at cholinergic terminals.

  8. Extracellular GABA in the ventrolateral thalamus of rats exhibiting spontaneous absence epilepsy: a microdialysis study.

    PubMed

    Richards, D A; Lemos, T; Whitton, P S; Bowery, N G

    1995-10-01

    There is compelling evidence that excessive GABA-mediated inhibition may underlie the abnormal electrical activity, initiated in the thalamus, associated with epileptic absence seizures. In particular, the GABAB receptor subtype seems to play a critical role, because its antagonists are potent inhibitors of absence seizures, whereas its agonists exacerbate seizure activity. Using a validated rat model of absence epilepsy, we have previously found no evidence of abnormal GABAB receptor density or affinity in thalamic tissue. In the present study, we have used in vivo microdialysis to monitor changes in levels of extracellular GABA and other amino acids in this brain region. We have shown that basal extracellular levels of GABA and, to a lesser extent, taurine are increased when compared with values in nonepileptic controls. However, modifying GABAergic transmission with the GABAB agonist (-)-baclofen (2 mg/kg i.p.), the GABAB antagonist CGP-35348 (200 mg/kg i.p.), or the GABA uptake inhibitor tiagabine (100 microM) did not produce any further alteration in extracellular GABA levels, despite the ability of these compounds to increase (baclofen and tiagabine) or decrease (CGP-35348) seizure activity. These findings suggest that the increased basal GABA levels observed in this animal model are not simply a consequence of seizure activity but may contribute to the initiation of absence seizures.

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

    PubMed

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

    2014-08-17

    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 100 ppb 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.

  10. Treatment of GABA from Fermented Rice Germ Ameliorates Caffeine-Induced Sleep Disturbance in Mice

    PubMed Central

    Mabunga, Darine Froy N.; Gonzales, Edson Luck T.; Kim, Hee Jin; Choung, Se Young

    2015-01-01

    γ-Aminobutyric acid (GABA), a major inhibitory neurotransmitter in the mammalian central nervous system, is involved in sleep physiology. Caffeine is widely used psychoactive substance known to induce wakefulness and insomnia to its consumers. This study was performed to examine whether GABA extracts from fermented rice germ ameliorates caffeine-induced sleep disturbance in mice, without affecting spontaneous locomotor activity and motor coordination. Indeed, caffeine (10 mg/kg, i.p.) delayed sleep onset and reduced sleep duration of mice. Conversely, rice germ ferment extracts-GABA treatment (10, 30, or 100 mg/kg, p.o.), especially at 100 mg/kg, normalized the sleep disturbance induced by caffeine. In locomotor tests, rice germ ferment extracts-GABA slightly but not significantly reduced the caffeine-induced increase in locomotor activity without affecting motor coordination. Additionally, rice germ ferment extracts-GABA per se did not affect the spontaneous locomotor activity and motor coordination of mice. In conclusion, rice germ ferment extracts-GABA supplementation can counter the sleep disturbance induced by caffeine, without affecting the general locomotor activities of mice. PMID:25995826

  11. Wavelength-Selective One- and Two-Photon Uncaging of GABA

    PubMed Central

    2013-01-01

    We have synthesized photolabile 7-diethylamino coumarin (DEAC) derivatives of γ-aminobutyric acid (GABA). These caged neurotransmitters efficiently release GABA using linear or nonlinear excitation. We used a new DEAC-based caging chromophore that has a vinyl acrylate substituent at the 3-position that shifts the absorption maximum of DEAC to about 450 nm and thus is named “DEAC450”. DEAC450-caged GABA is photolyzed with a quantum yield of 0.39 and is highly soluble and stable in physiological buffer. We found that DEAC450-caged GABA is relatively inactive toward two-photon excitation at 720 nm, so when paired with a nitroaromatic caged glutamate that is efficiently excited at such wavelengths, we could photorelease glutamate and GABA around single spine heads on neurons in brain slices with excellent wavelength selectivity using two- and one-photon photolysis, respectively. Furthermore, we found that DEAC450-caged GABA could be effectively released using two-photon excitation at 900 nm with spatial resolution of about 3 μm. Taken together, our experiments show that the DEAC450 caging chromophore holds great promise for the development of new caged compounds that will enable wavelength-selective, two-color interrogation of neuronal signaling with excellent subcellular resolution. PMID:24304264

  12. Tolerance to allopregnanolone with focus on the GABA-A receptor

    PubMed Central

    Turkmen, Sahruh; Backstrom, Torbjorn; Wahlstrom, Goran; Andreen, Lotta; Johansson, Inga-Maj

    2011-01-01

    Many studies have suggested a relationship between stress, sex steroids, and negative mental and mood changes in humans. The progesterone metabolite allopregnanolone is a potent endogenous ligand of the γ-amino butyric acid –A (GABA-A) receptor, and the most discussed neuroactive steroid. Variations in the levels of neuroactive steroids that influence the activity of the GABA-A receptor cause a vulnerability to mental and emotional pathology. There are physiological conditions in which allopregnanolone production increases acutely (e.g. stress) or chronically (e.g. menstrual cycle, pregnancy), thus exposing the GABA-A receptor to high and continuous allopregnanolone concentrations. In such conditions, tolerance to allopregnanolone may develop. We have shown that both acute and chronic tolerances can develop to the effects of allopregnanolone. Following the development of acute allopregnanolone tolerance, there is a decrease in the abundance of the GABA-A receptor α4 subunit and the expression of the α4 subunit mRNA in the ventral-posteriomedial nucleus of the thalamus. Little is known about the mechanism behind allopregnanolone tolerance and its effects on assembly of the GABA-A receptor composition. The exact mechanism of the allopregnanolone tolerance phenomena remains unclear. The purpose of this review is to summarize certain aspects of current knowledge concerning allopregnanolone tolerance and changes in the GABA-A receptors. PMID:20883478

  13. Intestinal Microbiota-Derived GABA Mediates Interleukin-17 Expression during Enterotoxigenic Escherichia coli Infection.

    PubMed

    Ren, Wenkai; Yin, Jie; Xiao, Hao; Chen, Shuai; Liu, Gang; Tan, Bie; Li, Nengzhang; Peng, Yuanyi; Li, Tiejun; Zeng, Benhua; Li, Wenxia; Wei, Hong; Yin, Zhinan; Wu, Guoyao; Hardwidge, Philip R; Yin, Yulong

    2016-01-01

    Intestinal microbiota has critical importance in pathogenesis of intestinal infection; however, the role of intestinal microbiota in intestinal immunity during enterotoxigenic Escherichia coli (ETEC) infection is poorly understood. The present study tested the hypothesis that the intestinal microbiota is associated with intestinal interleukin-17 (IL-17) expression in response to ETEC infection. Here, we found ETEC infection induced expression of intestinal IL-17 and dysbiosis of intestinal microbiota, increasing abundance of γ-aminobutyric acid (GABA)-producing Lactococcus lactis subsp. lactis. Antibiotics treatment in mice lowered the expression of intestinal IL-17 during ETEC infection, while GABA or L. lactis subsp. lactis administration restored the expression of intestinal IL-17. L. lactis subsp. lactis administration also promoted expression of intestinal IL-17 in germ-free mice during ETEC infection. GABA enhanced intestinal IL-17 expression in the context of ETEC infection through activating mechanistic target of rapamycin complex 1 (mTORC1)-ribosomal protein S6 kinase 1 (S6K1) signaling. GABA-mTORC1 signaling also affected intestinal IL-17 expression in response to Citrobacter rodentium infection and in drug-induced model of intestinal inflammation. These findings highlight the importance of intestinal GABA signaling in intestinal IL-17 expression during intestinal infection and indicate the potential of intestinal microbiota-GABA signaling in IL-17-associated intestinal diseases.

  14. GABA regulates synaptic integration of newly generated neurons in the adult brain

    NASA Astrophysics Data System (ADS)

    Ge, Shaoyu; Goh, Eyleen L. K.; Sailor, Kurt A.; Kitabatake, Yasuji; Ming, Guo-Li; Song, Hongjun

    2006-02-01

    Adult neurogenesis, the birth and integration of new neurons from adult neural stem cells, is a striking form of structural plasticity and highlights the regenerative capacity of the adult mammalian brain. Accumulating evidence suggests that neuronal activity regulates adult neurogenesis and that new neurons contribute to specific brain functions. The mechanism that regulates the integration of newly generated neurons into the pre-existing functional circuitry in the adult brain is unknown. Here we show that newborn granule cells in the dentate gyrus of the adult hippocampus are tonically activated by ambient GABA (γ-aminobutyric acid) before being sequentially innervated by GABA- and glutamate-mediated synaptic inputs. GABA, the major inhibitory neurotransmitter in the adult brain, initially exerts an excitatory action on newborn neurons owing to their high cytoplasmic chloride ion content. Conversion of GABA-induced depolarization (excitation) into hyperpolarization (inhibition) in newborn neurons leads to marked defects in their synapse formation and dendritic development in vivo. Our study identifies an essential role for GABA in the synaptic integration of newly generated neurons in the adult brain, and suggests an unexpected mechanism for activity-dependent regulation of adult neurogenesis, in which newborn neurons may sense neuronal network activity through tonic and phasic GABA activation.

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

    PubMed Central

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

    2012-01-01

    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. PMID:22159125

  16. Pre-synaptic GABA receptors inhibit glutamate release through GIRK channels in rat cerebral cortex.

    PubMed

    Ladera, Carolina; del Carmen Godino, María; José Cabañero, María; Torres, Magdalena; Watanabe, Masahiko; Luján, Rafael; Sánchez-Prieto, José

    2008-12-01

    Neuronal G protein-gated inwardly rectifying potassium (GIRK) channels mediate the slow inhibitory effects of many neurotransmitters post-synaptically. However, no evidence exists that supports that GIRK channels play any role in the inhibition of glutamate release by GABA(B) receptors. In this study, we show for the first time that GABA(B) receptors operate through two mechanisms in nerve terminals from the cerebral cortex. As shown previously, GABA(B) receptors reduces glutamate release and the Ca(2+) influx mediated by N-type Ca(2+) channels in a mode insensitive to the GIRK channel blocker tertiapin-Q and consistent with direct inhibition of this voltage-gated Ca(2+) channel. However, by means of weak stimulation protocols, we reveal that GABA(B) receptors also reduce glutamate release mediated by P/Q-type Ca(2+) channels, and that these responses are reversed by the GIRK channel blocker tertiapin-Q. Consistent with the functional interaction between GABA(B) receptors and GIRK channels at nerve terminals we demonstrate by immunogold electron immunohistochemistry that pre-synaptic boutons of asymmetric synapses co-express GABA(B) receptors and GIRK channels, thus suggesting that the functional interaction of these two proteins, found at the post-synaptic level, also occurs at glutamatergic nerve terminals.

  17. {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

    Zheng Gang; Zhang Wenbin; Zhang Yun; Chen Yaoming; Liu Mingchao; Yao Ting; Yang Yanxia; Zhao Fang; Li Jingxia; Huang Chuanshu; Luo Wenjing Chen Jingyuan

    2009-04-15

    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.

  18. Taurine is a potent activator of extrasynaptic GABA(A) receptors in the thalamus.

    PubMed

    Jia, Fan; Yue, Minerva; Chandra, Dev; Keramidas, Angelo; Goldstein, Peter A; Homanics, Gregg E; Harrison, Neil L

    2008-01-02

    Taurine is one of the most abundant free amino acids in the brain. In a number of studies, taurine has been reported to activate glycine receptors (Gly-Rs) at moderate concentrations (> or = 100 microM), and to be a weak agonist at GABA(A) receptors (GABA(A)-Rs), which are usually activated at high concentrations (> or = 1 mM). In this study, we show that taurine reduced the excitability of thalamocortical relay neurons and activated both extrasynaptic GABA(A)-Rs and Gly-Rs in neurons in the mouse ventrobasal (VB) thalamus. Low concentrations of taurine (10-100 microM) decreased neuronal input resistance and firing frequency, and elicited a steady outward current under voltage clamp, but had no effects on fast inhibitory synaptic currents. Currents elicited by 50 microM taurine were abolished by gabazine, insensitive to midazolam, and partially blocked by 20 microM Zn2+, consistent with the pharmacological properties of extrasynaptic GABA(A)-Rs (alpha4beta2delta subtype) involved in tonic inhibition in the thalamus. Tonic inhibition was enhanced by an inhibitor of taurine transport, suggesting that taurine can act as an endogenous activator of these receptors. Taurine-evoked currents were absent in relay neurons from GABA(A)-R alpha4 subunit knock-out mice. The amplitude of the taurine current was larger in neurons from adult mice than juvenile mice. Taurine was a more potent agonist at recombinant alpha4beta2delta GABA(A)-Rs than at alpha1beta2gamma2 GABA(A)-Rs. We conclude that physiological concentrations of taurine can inhibit VB neurons via activation of extrasynaptic GABA(A)-Rs and that taurine may function as an endogenous regulator of excitability and network activity in the thalamus.

  19. GABA and glycine are protective to mature but toxic to immature rat cortical neurons under hypoxia.

    PubMed

    Zhao, Peng; Qian, Hong; Xia, Ying

    2005-07-01

    Although recent studies suggest that gamma-aminobutyric acid (GABA) and glycine may be 'inhibitory' to mature neurons, but 'excitatory' to immature neurons under normoxia, it is unknown whether inhibitory neurotransmitters are differentially involved in neuronal response to hypoxia in immature and mature neurons. In the present study, we exposed rat cortical neurons to hypoxia (1% O2) and examined the effects of three major inhibitory neurotransmitters (GABA, glycine and taurine) on the hypoxic neurons at different neuronal ages [days in vitro (DIV)4-20]. Our data showed that the cortical neurons expressed both GABA(A) and glycine receptors with differential developmental profiles. GABA (10-2000 microm) was neuroprotective to hypoxic neurons of DIV20, but enhanced hypoxic injury in neurons of GABA. However, higher concentrations of glycine (1000-2000 microm) for long-term exposure (48-72 h) displayed neuroprotection at all ages (DIV4-20). Taurine (10-2000 microm), unlike GABA and glycine, displayed protection only in DIV4 neurons, and was slightly toxic to neurons>DIV4. In comparison with delta-opioid receptor (DOR)-induced protection in DIV20 neurons exposed to 72 h of hypoxia, glycine-induced protection was weaker than that of DOR but stronger than that of GABA and taurine. These data suggest that the effects of the inhibitory neurotransmitters on hypoxic cortical neurons are age-dependent, with GABA and glycine being neurotoxic to immature neurons and neuroprotective to mature neurons.

  20. Actions of acetylcholine and GABA on spontaneous contractions of the filariid, Dipetalonema viteae.

    PubMed

    Christ, D; Goebel, M; Saz, H J

    1990-12-01

    1. Isotonic contractions were recorded from the filarial nematode, Dipetalonema viteae (Acanthocheilonema viteae), in an isolated tissue chamber. 2. Nicotine (10(-6) M) and pilocarpine (10(-5) M) increased the spontaneous contractions in the intact filariid, but acetylcholine (ACh, 10(-4) M) and muscarine (10(-5) M) were inactive. 3. When ACh was applied to an opened D. viteae, it was 10,000 times more potent. This indicates that the cuticle is an effective barrier to the penetration of ACh to the muscle cells. 4. The effects of ACh on the opened D. viteae were not affected by hexamethonium (10(-3) M) or atropine (10(-5) M) and were only partially reduced by (+)-tubocurarine (10(-4) M). 5. gamma-Aminobutyric acid (GABA, 10(-3) M) reduced the spontaneous activity of the intact D. viteae; however, the effect of GABA had a slow onset and recovery. Muscimol (10(-5) M) was more potent than GABA and had a more rapid onset and recovery. 6. GABA was 1,000 times more potent on the opened D. viteae than on the intact D. viteae. Baclofen (10(-3) M) was inactive on both preparations. 7. The effect of GABA was not antagonized by bicuculline (10(-4) M), picrotoxin (10(-5) M or penicillin G (10(-3) M). 8. It is concluded that the filariid cuticle acts like a lipid structure and blocks the penetration of polar substances, such as ACh and GABA. Also, due to the lack of efficacy of the ACh and GABA antagonists, it was concluded that the nematode receptors are somewhat different from the mammalian ACh and GABA receptors.

  1. Thalamic GABA Predicts Fine Motor Performance in Manganese-Exposed Smelter Workers

    PubMed Central

    Long, Zaiyang; Li, Xiang-Rong; Xu, Jun; Edden, Richard A. E.; Qin, Wei-Ping; Long, Li-Ling; Murdoch, James B.; Zheng, Wei; Jiang, Yue-Ming; Dydak, Ulrike

    2014-01-01

    Overexposure to manganese (Mn) may lead to parkinsonian symptoms including motor deficits. The main inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is known to play a pivotal role in the regulation and performance of movement. Therefore this study was aimed at testing the hypothesis that an alteration of GABA following Mn exposure may be associated with fine motor performance in occupationally exposed workers and may underlie the mechanism of Mn-induced motor deficits. A cohort of nine Mn-exposed male smelter workers from an Mn-iron alloy factory and 23 gender- and age-matched controls were recruited and underwent neurological exams, magnetic resonance spectroscopy (MRS) measurements, and Purdue pegboard motor testing. Short-echo-time MRS was used to measure N-Acetyl-aspartate (NAA) and myo-inositol (mI). GABA was detected with a MEGA-PRESS J-editing MRS sequence. The mean thalamic GABA level was significantly increased in smelter workers compared to controls (p = 0.009). Multiple linear regression analysis reveals (1) a significant association between the increase in GABA level and the duration of exposure (R2 = 0.660, p = 0.039), and (2) significant inverse associations between GABA levels and all Purdue pegboard test scores (for summation of all scores R2 = 0.902, p = 0.001) in the smelter workers. In addition, levels of mI were reduced significantly in the thalamus and PCC of smelter workers compared to controls (p = 0.030 and p = 0.009, respectively). In conclusion, our results show clear associations between thalamic GABA levels and fine motor performance. Thus in Mn-exposed subjects, increased thalamic GABA levels may serve as a biomarker for subtle deficits in motor control and may become valuable for early diagnosis of Mn poisoning. PMID:24505436

  2. Postnatal alterations of GABA receptor profiles in the rat superior colliculus.

    PubMed

    Clark, S E; Garret, M; Platt, B

    2001-01-01

    Midbrain sections taken from Sprague-Dawley rats of varying ages within the first four postnatal weeks were used to determine, immunocytochemically, putative changes of GABA(A) receptor beta2/3 subunits, GABA(B) receptor (R1a and R1b splice variants), and GABA(C) receptor rho1 subunit expression and distribution in the superficial, visual layers of the superior colliculus. Immunoreactivity for the GABA(A) receptor beta2/3 subunits was found in the superficial grey layer from birth. The labelling changed with age, with an overall continuous reduction in the number of cells labelled and a significant increase in the labelling intensity distribution (neuropil vs soma). Further analysis revealed an initial increase in the labelling intensity between postnatal days 0 and 7 in parallel with an overall reduction of labelled neurones. This was followed by a significant decrease in labelling intensity distribution between postnatal days 7 and 16, and a subsequent increase in intensity between postnatal days 16 and 28. The labelling profiles for GABA(B) receptors (R1a and R1b splice variants) and GABA(C) receptors (rho1 subunit) showed similar patterns. Both receptors could be found in the superficial layers of the superior colliculus from birth, and the intensity and distribution of labelling remained constant during the first postnatal month. However, the cell body count showed a significant decrease between postnatal days 7 and 16. These changes may be related to the time-point of eye opening, which occurred approximately two weeks after birth. For all three receptor types, the cell body count remained constant after postnatal day 16. By four weeks of age, there was no significant difference between the cell numbers obtained for the different receptors. Both GABA itself and neurofilament labelling were also obtained in the superficial superior colliculus at birth. Neurofilament, although found at birth, showed very little ordered arrangement until 16days after birth. When

  3. Effects of intraventricular taurine, homotaurine and GABA on serum prolactin and thyrotropin levels in female and in male rats.

    PubMed

    Mäkinen, M; Ahtee, L; Rosenqvist, K; Tuominen, R K; Männistö, P

    1993-01-01

    Serum prolactin and thyrotropin levels of conscious, unrestrained male and female rats were compared after intracerebroventricular (i.c.v.) administration of taurine, gamma-aminobutyric acid (GABA) and homotaurine. The amino acids studied had no clear effect on serum basal thyrotropin levels in male or female rats. All amino acids elevated serum prolactin levels in female rats at the dose of 5 mumol/rat; homotaurine by about 18-fold, taurine and GABA by 3-fold. Only homotaurine elevated serum prolactin of male rats at this dose, but its effect was less pronounced (p < 0.01) in male than in female rats. Although homotaurine was clearly more potent than the two other amino acids, at the dose of 10 mumol/rat taurine and GABA also elevated serum prolactin in male rats. These findings show that there are gender-related differences in the responses of serum prolactin levels to homotaurine, taurine and GABA in rats. The tuberoinfundibular dopaminergic pathway, which exerts tonic inhibitory influence on prolactin secretion, is sexually differentiated. Hence the gender-related differences in the effects of the amino acids on prolactin secretion suggest that they might inhibit dopamine release from the median eminence. In case of homotaurine, the gender effect was most pronounced. The less clear dependence of GABA's effect on the gender is in accordance with the suggestions that GABA influences the secretion of serum prolactin by more than one mechanism.

  4. Manganese exposure inhibits the clearance of extracellular GABA and influences taurine homeostasis in the striatum of developing rats.

    PubMed

    Fordahl, Steve C; Anderson, Joel G; Cooney, Paula T; Weaver, Tara L; Colyer, Christa L; Erikson, Keith M

    2010-12-01

    Manganese (Mn) accumulation in the brain has been shown to alter the neurochemistry of the basal ganglia. Mn-induced alterations in dopamine biology are fairly well understood, but recently more evidence has emerged characterizing the role of γ-aminobutyric acid (GABA) in this dysfunction. The purpose of this study was to determine if the previously observed Mn-induced increase in extracellular GABA (GABA(EC)) was due to altered GABA transporter (GAT) function, and whether Mn perturbs other amino acid neurotransmitters, namely taurine and glycine (known modulators of GABA). Extracellular GABA, taurine, and glycine concentrations were collected from the striatum of control (CN) or Mn-exposed Sprague-Dawley rats using in vivo microdialysis, and the GAT inhibitor nipecotic acid (NA) was used to probe GAT function. Tissue and extracellular Mn levels were significantly increased, and the Fe:Mn ratio was decreased 36-fold in the extracellular space due to Mn-exposure. NA led to a 2-fold increase in GABA(EC) of CNs, a response that was attenuated by Mn. Taurine responded inversely to GABA, and a novel 10-fold increase in taurine was observed after the removal of NA in CNs. Mn blunted this response and nearly abolished extracellular taurine throughout collection. Striatal taurine transporter (Slc6a6) mRNA levels were significantly increased with Mn-exposure, and Mn significantly increased (3)H-Taurine uptake after 3-min exposure in primary rat astrocytes. These data suggest that Mn increases GABA(EC) by inhibiting the function of GAT, and that perturbed taurine homeostasis potentially impacts neural function by jeopardizing the osmoregulatory and neuromodulatory functions of taurine in the brain.

  5. Phenibut (beta-phenyl-GABA): a tranquilizer and nootropic drug.

    PubMed

    Lapin, I

    2001-01-01

    Phenibut (beta-phenyl-gamma-aminobutyric acid HCl) is a neuropsychotropic drug that was discovered and introduced into clinical practice in Russia in the 1960s. It has anxiolytic and nootropic (cognition enhancing) effects. It acts as a GABA-mimetic, primarily at GABA(B) and, to some extent, at GABA(A) receptors. It also stimulates dopamine receptors and antagonizes beta-phenethylamine (PEA), a putative endogenous anxiogenic. The psychopharmacological activity of phenibut is similar to that of baclofen, a p-Cl-derivative of phenibut. This article reviews the structure-activity relationship of phenibut and its derivatives. Emphasis is placed on the importance of the position of the phenyl ring, the role of the carboxyl group, and the activity of optical isomers. Comparison of phenibut with piracetam and diazepam reveals similarities and differences in their pharmacological and clinical effects. Phenibut is widely used in Russia to relieve tension, anxiety, and fear, to improve sleep in psychosomatic or neurotic patients; as well as a pre- or post-operative medication. It is also used in the therapy of disorders characterized by asthenia and depression, as well as in post-traumatic stress, stuttering and vestibular disorders.

  6. The GABA transaminase, ABAT, is essential for mitochondrial nucleoside metabolism

    PubMed Central

    Besse, Arnaud; Wu, Ping; Bruni, Francesco; Donti, Taraka; Graham, Brett H.; Craigen, William J.; McFarland, Robert; Moretti, Paolo; Lalani, Seema; Scott, Kenneth L.; Taylor, Robert W.; Bonnen, Penelope E.

    2015-01-01

    Summary ABAT is a key enzyme responsible for catabolism of principal inhibitory neurotransmitter gamma-aminobutyric acid (GABA). We report an essential role for ABAT in a seemingly unrelated pathway, mitochondrial nucleoside salvage, and demonstrate that mutations in this enzyme cause an autosomal recessive neurometabolic disorder and mtDNA depletion syndrome (MDS). We describe a family with encephalomyopathic MDS caused by a homozygous missense mutation in ABAT that results in elevated GABA in subjects’ brains as well as decreased mtDNA levels in subjects’ fibroblasts. Nucleoside rescue and co-IP experiments pinpoint that ABAT functions in the mitochondrial nucleoside salvage pathway to facilitate conversion of dNDPs to dNTPs. Pharmacological inhibition of ABAT through the irreversible inhibitor Vigabatrin caused depletion of mtDNA in photoreceptor cells that was prevented through addition of dNTPs in cell culture media. This work reveals ABAT as a connection between GABA metabolism and nucleoside metabolism and defines a neurometabolic disorder that includes MDS. PMID:25738457

  7. GABA and Endocannabinoids Mediate Depotentiation of Schaffer Collateral Synapses Induced by Stimulation of Temperoammonic Inputs.

    PubMed

    Izumi, Yukitoshi; Zorumski, Charles F

    2016-01-01

    Long-term potentiation (LTP) of Schaffer collateral (SC) synapses in the hippocampus is thought to play a key role in episodic memory formation. Because the hippocampus is a shorter-term, limited capacity storage system, repeated bouts of learning and synaptic plasticity require that SC synapses reset to baseline at some point following LTP. We previously showed that repeated low frequency activation of temperoammonic (TA) inputs to the CA1 region depotentiates SC LTP without persistently altering basal transmission. This heterosynaptic depotentiation involves adenosine A1 receptors but not N-methyl-D-aspartate receptors, metabotropic glutamate receptors or L-type calcium channels. In the present study, we used rat hippocampal slices to explore other messengers contributing to TA-induced SC depotentiation, and provide evidence for the involvement of cannabinoid-1 and γ-aminobutyric acid (GABA) type-A receptors as more proximal signaling events leading to synaptic resetting, with A1 receptor activation serving as a downstream event. Surprisingly, we found that TA-induced SC depotentiation is independent of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate glutamate receptors. We also examined the involvement of mitogen-activated protein kinases (MAPKs), and found a role for extracellular-signal related kinase 1/2 and p38 MAPK, but not c-Jun-N-terminal kinase. These results indicate that low frequency stimulation of TA inputs to CA1 activates a complex signaling network that instructs SC synaptic resetting. The involvement of GABA and endocannabinoids suggest mechanisms that could contribute to cognitive dysfunction associated with substance abuse and neuropsychiatric disorders.

  8. GABA maintains the proliferation of progenitors in the developing chick ciliary marginal zone and non-pigmented ciliary epithelium.

    PubMed

    Ring, Henrik; Mendu, Suresh Kumar; Shirazi-Fard, Shahrzad; Birnir, Bryndis; Hallböök, Finn

    2012-01-01

    GABA is more than the main inhibitory neurotransmitter found in the adult CNS. Several studies have shown that GABA regulates the proliferation of progenitor and stem cells. This work examined the effects of the GABA(A) receptor system on the proliferation of retinal progenitors and non-pigmented ciliary epithelial (NPE) cells. qRT-PCR and whole-cell patch-clamp electrophysiology were used to characterize the GABA(A) receptor system. To quantify the effects on proliferation by GABA(A) receptor agonists and antagonists, incorporation of thymidine analogues was used. The results showed that the NPE cells express functional extrasynaptic GABA(A) receptors with tonic properties and that low concentration of GABA is required for a baseline level of proliferation. Antagonists of the GABA(A) receptors decreased the proliferation of dissociated E12 NPE cells. Bicuculline also had effects on progenitor cell proliferation in intact E8 and E12 developing retina. The NPE cells had low levels of the Cl-transporter KCC2 compared to the mature retina, suggesting a depolarising role for the GABA(A) receptors. Treatment with KCl, which is known to depolarise membranes, prevented some of the decreased proliferation caused by inhibition of the GABA(A) receptors. This supported the depolarising role for the GABA(A) receptors. Inhibition of L-type voltage-gated Ca(2+) channels (VGCCs) reduced the proliferation in the same way as inhibition of the GABA(A) receptors. Inhibition of the channels increased the expression of the cyclin-dependent kinase inhibitor p27(KIP1), along with the reduced proliferation. These results are consistent with that when the membrane potential indirectly regulates cell proliferation with hyperpolarisation of the membrane potential resulting in decreased cell division. The increased expression of p27(KIP1) after inhibition of either the GABA(A) receptors or the L-type VGCCs suggests a link between the GABA(A) receptors, membrane potential, and intracellular Ca

  9. Ionotropic GABA and Glutamate Receptor Mutations and Human Neurologic Diseases

    PubMed Central

    Yuan, Hongjie; Low, Chian-Ming; Moody, Olivia A.; Jenkins, Andrew

    2015-01-01

    The advent of whole exome/genome sequencing and the technology-driven reduction in the cost of next-generation sequencing as well as the introduction of diagnostic-targeted sequencing chips have resulted in an unprecedented volume of data directly linking patient genomic variability to disorders of the brain. This information has the potential to transform our understanding of neurologic disorders by improving diagnoses, illuminating the molecular heterogeneity underlying diseases, and identifying new targets for therapeutic treatment. There is a strong history of mutations in GABA receptor genes being involved in neurologic diseases, particularly the epilepsies. In addition, a substantial number of variants and mutations have been found in GABA receptor genes in patients with autism, schizophrenia, and addiction, suggesting potential links between the GABA receptors and these conditions. A new and unexpected outcome from sequencing efforts has been the surprising number of mutations found in glutamate receptor subunits, with the GRIN2A gene encoding the GluN2A N-methyl-d-aspartate receptor subunit being most often affected. These mutations are associated with multiple neurologic conditions, for which seizure disorders comprise the largest group. The GluN2A subunit appears to be a locus for epilepsy, which holds important therapeutic implications. Virtually all α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor mutations, most of which occur within GRIA3, are from patients with intellectual disabilities, suggesting a link to this condition. Similarly, the most common phenotype for kainate receptor variants is intellectual disability. Herein, we summarize the current understanding of disease-associated mutations in ionotropic GABA and glutamate receptor families, and discuss implications regarding the identification of human mutations and treatment of neurologic diseases. PMID:25904555

  10. Insula and anterior cingulate GABA levels in post-traumatic stress disorder: Preliminary findings using magnetic resonance spectroscopy

    PubMed Central

    Rosso, Isabelle M.; Weiner, Melissa R.; Crowley, Davidan J; Silveri, Marisa M.; Rauch, Scott L.; Jensen, J. Eric

    2013-01-01

    Background Increased reactivity of the insular cortex and decreased activity of the dorsal anterior cingulate (ACC) are seen in functional imaging studies of post-traumatic stress disorder (PTSD), and may partly explain the persistent fear- and anxiety-proneness that characterize the disorder. A possible neurochemical correlate is altered function of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). We report results from what we believe is the first study applying proton magnetic resonance spectroscopy (1H-MRS) to measure brain GABA in PTSD. Methods Thirteen adults with DSM-IV PTSD and 13 matched healthy control subjects underwent single voxel 1H-MRS at 4 Tesla. GABA was measured in the right anterior insula and dorsal anterior cingulate, using MEGAPRESS spectral editing. Subjects were interviewed with the Structured Clinical Interview for DSM-IV and the Clinician Administered PTSD Scale, and also completed the State and Trait Anxiety Inventory. Results Insula GABA was significantly lower in PTSD subjects than in controls, and dorsal ACC GABA did not differ significantly between the groups. Insula GABA was not significantly associated with severity of PTSD symptoms. However, lower insula GABA was associated with significantly higher state and trait anxiety in the subject sample as a whole. Conclusions PTSD is associated with reduced GABA in the right anterior insula. This preliminary evidence of the 1H-MRS GABA metabolite as a possible biomarker of PTSD encourages replication in larger samples and examination of relations with symptom dimensions. Future studies also should examine whether insula GABA is a marker of anxiety proneness, cutting across clinical diagnostic categories. PMID:23861191

  11. Hypoplasia of spiral and Scarpa's ganglion cells in GABA(A) receptor beta(3) subunit knockout mice.

    PubMed

    Koo, Ja-Won; Homanics, Gregg E; Balaban, Carey D

    2002-05-01

    This study documents morphologic alterations in the spiral ganglion and Scarpa's ganglion from gamma-aminobutyric acid A (GABA(A)) receptor beta(3) subunit null mutant mice. The ganglion cells of the mutant mice were hypoplastic in hematoylin&eosin-stained sections. Hypoplasia was observed at every location of the spiral ganglion and Scarpa's ganglion except the apical cochlear turn. Calretinin immunostaining demonstrated a selective hypoplasia of calretinin-negative cells at every location of spiral and Scarpa's ganglion cells, while the soma area of calretinin-positive cells was not affected by the gene deletion. Meanwhile, in the spiral ganglion of both wild type and knockout mice, there were apical to basal gradients in the soma size and the proportion of calretinin-positive cells. The absence of statistically significant hypoplasia in hematoylin&eosin sections through the apical turn of the cochlea can be explained by the relatively higher proportion of calretinin-positive ganglion cells, which were unaffected by the gene deletion. These findings suggest that GABA(A) receptor isoforms containing the beta(3) subunit may play an important role in the development and differentiation of non-calyceal terminals of Scarpa's ganglion cells and type II and smaller type I spiral ganglion cells.

  12. Characteristics of GABA-activated chloride channels in mammalian dorsal root ganglion neurones.

    PubMed

    Robertson, B

    1989-04-01

    1. The properties of gamma-aminobutyric acid (GABA)-activated chloride channels in dorsal root ganglion (DRG) neurones obtained from rats and cats were examined using the single-electrode voltage clamp in conjunction with suction-electrode techniques. 2. GABA-evoked currents showed voltage-sensitive kinetics. Time constants (tau D) were measured from voltage-jump relaxations and tau D became briefer with membrane hyperpolarization. tau D was 33 ms at -120 mV with 60 microM-GABA and changed e-fold for 188 mV. tau D decreased as GABA concentration was increased - the extrapolated tau D at 'zero' GABA concentration was approximately equal to 50 ms at -120 mV. 3. The steady-state current in GABA was curvilinear, rectifying at negative potentials. The instantaneous current was linear with symmetrical chloride concentrations (140 mM) on both sides of the cell membrane. 4. Muscimol was a more effective agonist than GABA, while piperidine-4-sulphonic acid and ethylenediamine monocarbamate were only weakly effective agonists. Taurine and glycine had no detectable agonist activity. 5. Ion substitution experiments revealed the permeability sequence I- greater than Br- greater than Cl- greater than F- greater than propionate (1.88 greater than 1.21 greater than 1.0 approximately equal to 0.1 approximately equal to 0.1). 6. The presence of iodide and bromide ions externally caused an increase in chloride efflux at membrane potentials more negative than -40 mV, and caused a prolongation of voltage-jump relaxations. Relaxations in fluoride and propionate solutions were faster than those seen in chloride.

  13. Hyperpolarization-independent maturation and refinement of GABA/glycinergic connections in the auditory brain stem

    PubMed Central

    Lee, Hanmi; Bach, Eva; Noh, Jihyun; Delpire, Eric

    2015-01-01

    During development GABA and glycine synapses are initially excitatory before they gradually become inhibitory. This transition is due to a developmental increase in the activity of neuronal potassium-chloride cotransporter 2 (KCC2), which shifts the chloride equilibrium potential (ECl) to values more negative than the resting membrane potential. While the role of early GABA and glycine depolarizations in neuronal development has become increasingly clear, the role of the transition to hyperpolarization in synapse maturation and circuit refinement has remained an open question. Here we investigated this question by examining the maturation and developmental refinement of GABA/glycinergic and glutamatergic synapses in the lateral superior olive (LSO), a binaural auditory brain stem nucleus, in KCC2-knockdown mice, in which GABA and glycine remain depolarizing. We found that many key events in the development of synaptic inputs to the LSO, such as changes in neurotransmitter phenotype, strengthening and elimination of GABA/glycinergic connection, and maturation of glutamatergic synapses, occur undisturbed in KCC2-knockdown mice compared with wild-type mice. These results indicate that maturation of inhibitory and excitatory synapses in the LSO is independent of the GABA and glycine depolarization-to-hyperpolarization transition. PMID:26655825

  14. GABA Australis, some reflections on the history of GABA receptor research in Australia.

    PubMed

    Johnston, Graham A R

    2017-02-01

    Research on GABA receptors has a long history in Australia dating from 1958 with David Curtis and his colleagues in Canberra. This review traces many of the advances made in Australia guided by highly cited publications and some obscure ones. It covers the discovery of key chemicals with which to investigate GABA receptor function including bicuculline, muscimol, phaclofen, THIP and (+)-CAMP. Also described are findings relevant to the involvement of mutant GABA receptors in inherited epilepsy. The modulation of GABA receptors by a bewildering range of chemicals, especially by flavonoids and terpenoids, is discussed.

  15. Inhibition of GABA release by presynaptic ionotropic GABA receptors in hippocampal CA3.

    PubMed

    Axmacher, Nikolai; Draguhn, Andreas

    2004-02-09

    Vesicular transmitter release can be regulated by transmitter-gated ion channels at presynaptic axon terminals. The central inhibitory transmitter GABA acts on such presynaptic ionotropic receptors in various cells, including inhibitory interneurons. Here we report that GABA-mediated postsynaptic inhibitory currents in CA3 pyramidal cells of rat hippocampal slices are suppressed by agonists of GABAA receptors. The effect is present for both stimulus-induced and miniature IPSCs, indicating a reduction in the probability of vesicular release by presynaptic, action-potential-independent mechanisms. We conclude that the release of GABA from hippocampal CA3 interneurons is regulated by a negative feedback via presynaptic ionotropic GABA autoreceptors.

  16. 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.

    PubMed

    Yamamoto, N; Soghomonian, J-J

    2008-06-26

    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

  17. Interactions between dopamine and GABA in the control of ambulatory activity.

    PubMed

    Agmo, A; Belzung, C; Giordano, M

    1996-01-01

    Ambulatory activity of male rats was quantified in an open field. The subjects were treated with DL-amphetamine and amfonelic acid alone or combined with the GABA transaminase inhibitors gamma-acetylen GABA (GAG) and sodium valproate as well as with the GABAA agonist THIP and the GABAB agonist baclofen. Subeffective doses of the GABAergic drugs did not modify the effects of moderate doses of the dopaminergic stimulants whereas effective doses continued to reduce ambulatory activity just as in the absence of dopaminergic activation. When DL-amphetamine or amfonelic acid were administered in doses that strongly enhanced ambulatory activity, doses of the GABAergic drugs that were inhibitory in the absence of dopaminergic stimulation were no longer effective. The mixed D1/D2 dopamine antagonist pimozide, the D1 antagonist SCH 23390 and the D2 antagonist sulpiride were then combined with subeffective doses of the GABA agonists. GAG, sodium valproate and baclofen were potentiated by pimozide and SCH 23390 but not by sulpiride. THIP was ineffective. These data show that GABAergic drugs had a reduced effect after stimulation of dopaminergic neurotransmission. On the other hand, when dopamine D1 receptors were blocked, nonselective GABA agonists and the GABAB agonist baclofen were potentiated. This was not the case for the GABAA agonist THIP, suggesting that the GABAA receptor is of slight importance for the interactions between GABA and dopamine in the control of ambulatory activity. No potentiation of GABAergic agonists was obtained after treatment with a dopamine D2 antagonist.

  18. Proteomic and systems biology analysis of monocytes exposed to securinine, a GABA(A) receptor antagonist and immune adjuvant.

    PubMed

    Shipman, Matt; Lubick, Kirk; Fouchard, David; Guram, Rajani; Grieco, Paul; Jutila, Mark; Dratz, Edward A

    2012-01-01

    Securinine, a GABA(A) receptor antagonist, has been reported to enhance monocyte cell killing of Coxiella burnetii without obvious adverse effects in vivo. We employed multiplex 2D gel electrophoresis using Zdyes, a new generation of covalently linked fluorescent differential protein detection dyes to analyze changes in the monocyte proteome in response to Securinine. Securinine antagonism of GABA(A) receptors triggers the activation of p38. We used the differential protein expression results to guide a search of the literature and network analysis software to construct a systems biology model of the effect of Securinine on monocytes. The model suggests that various metabolic modulators (fatty acid binding protein 5, inosine 5'-monophosphate dehydrogenase, and thioredoxin) are at least partially reshaping the metabolic landscape within the monocytes. The actin bundling protein L-plastin, and the Ca(2+) binding protein S100A4 also appear to have important roles in the immune response stimulated by Securinine. Fatty acid binding protein 5 (FABP5) may be involved in effecting lipid raft composition, inflammation, and hormonal regulation of monocytes, and the model suggests that FABP5 may be a central regulator of metabolism in activated monocytes. The model also suggests that the heat shock proteins have a significant impact on the monocyte immune response. The model provides a framework to guide future investigations into the mechanisms of Securinine action and with elaboration may help guide development of new types of immune adjuvants.

  19. GABA Not Only a Neurotransmitter: Osmotic Regulation by GABAAR Signaling

    PubMed Central

    Cesetti, Tiziana; Ciccolini, Francesca; Li, Yuting

    2012-01-01

    Mature macroglia and almost all neural progenitor types express γ-aminobutyric (GABA) A receptors (GABAARs), whose activation by ambient or synaptic GABA, leads to influx or efflux of chloride (Cl−) depending on its electro-chemical gradient (ECl). Since the flux of Cl− is indissolubly associated to that of osmotically obliged water, GABAARs regulate water movements by modulating ion gradients. In addition, since water movements also occur through specialized water channels and transporters, GABAAR signaling could affect the movement of water by regulating the function of the channels and transporters involved, thereby affecting not only the direction of the water fluxes but also their dynamics. We will here review recent observations indicating that in neural cells GABAAR-mediated osmotic regulation affects the cellular volume thereby activating multiple intracellular signaling mechanisms important for cell proliferation, maturation, and survival. In addition, we will discuss evidence that the osmotic regulation exerted by GABA may contribute to brain water homeostasis in physiological and in pathological conditions causing brain edema, in which the GABAergic transmission is often altered. PMID:22319472

  20. GABA tea prevents cardiac fibrosis by attenuating TNF-alpha and Fas/FasL-mediated apoptosis in streptozotocin-induced diabetic rats.

    PubMed

    Cherng, Shur-Hueih; Huang, Chih-Yang; Kuo, Wei-Wen; Lai, Shue-Er; Tseng, Chien-Yu; Lin, Yueh-Min; Tsai, Fuu-Jen; Wang, Hsueh-Fang

    2014-03-01

    GABA tea is a tea product that contains a high level of gamma-aminobutyric acid (GABA). This study investigated the effects of GABA tea on the heart in a diabetic rat model. Male Wistar rats were injected with 55mg/kg streptozotocin (STZ) to induce diabetes for 2weeks and then orally given dosages of 4.55 and 45.5mg/kg/day GABA tea extract for 6weeks. The results revealed that fasting blood glucose levels returned to normal levels in GABA tea-treated diabetic rats, but not in the untreated diabetic rats. Additionally, GABA tea effectively inhibited cardiac fibrosis induced by STZ. Further experiments showed that the STZ-induced protein levels of tumor necrosis factor-alpha (TNF-alpha), Fas, activated caspase-8 and caspase-3 were significantly inhibited by the GABA tea treatment. Therefore, our data suggest that the inhibiting effect of GABA tea on STZ-induced cardiac fibrosis in diabetic rats may be mediated by reducing blood glucose and further attenuating TNF-alpha expression and/or Fas/Fas ligand (FasL)-mediated apoptosis. These findings will provide implications for the potential anti-diabetic properties of GABA tea.

  1. Low expression of the ClC-2 chloride channel during postnatal development: a mechanism for the paradoxical depolarizing action of GABA and glycine in the hippocampus.

    PubMed Central

    Mladinić, M; Becchetti, A; Didelon, F; Bradbury, A; Cherubini, E

    1999-01-01

    In early postnatal development, during the period of synapse formation, gamma-aminobutyric acid (GABA) and glycine, the main inhibitory transmitters in the adult brain, paradoxically excite and depolarize neuronal membranes by an outward flux of chloride. The mechanisms of chloride homeostasis are not fully understood. It is known that in adult neurons intracellular chloride accumulation is prevented by a particular type of chloride channel, the ClC-2. This channel strongly rectifies in the inward direction at potentials negative to ECl thus ensuring chloride efflux. We have tested the hypothesis that in the developing hippocampus, a differential expression or regulation of ClC-2 channels may contribute to the depolarizing action of GABA and glycine. We have cloned a truncated form of ClC-2 (ClC-2nh) from the neonatal hippocampus which lacks the 157 bp corresponding to exon 2. In situ hybridization experiments show that ClC-2nh is the predominant form of ClC-2 mRNA in the neonatal brain. ClC-2nh mRNA is unable to encode a full-length protein due to a frameshift, consequently it does not induce any currents upon injection into Xenopus oocytes. Low expression of the full-length ClC-2 channel, could alter chloride homeostasis, lead to accumulation of [Cl-]i and thereby contribute to the depolarizing action of GABA and glycine during early development. PMID:10418163

  2. Early loss of interneurons and delayed subunit-specific changes in GABA(A)-receptor expression in a mouse model of mesial temporal lobe epilepsy.

    PubMed

    Bouilleret, V; Loup, F; Kiener, T; Marescaux, C; Fritschy, J M

    2000-01-01

    Unilateral injection of kainic acid (KA) into the dorsal hippocampus of adult mice induces spontaneous recurrent partial seizures and replicates histopathological changes observed in human mesial temporal lobe epilepsy (MTLE) (Bouilleret V et al., Neuroscience 1999; 89:717-729). Alterations in pre- and postsynaptic components of GABAergic neurotransmission were investigated immunohistochemically at different time points (1-120 days) in this mouse model of MTLE. Markers of GABAergic interneurons (parvalbumin, calbindin-D28k, and calretinin), the type-1 GABA transporter (GAT1), and major GABA(A)-receptor subunits expressed in the hippocampal formation were analyzed. Acutely, KA injection produced a profound loss of hilar cells but only limited damage to CA1 and CA3 pyramidal cells. In addition, parvalbumin and calbindin-D28k staining of interneurons disappeared irreversibly in CA1 and dentate gyrus (DG), whereas calretinin staining was spared. The prominent GABA(A)-receptor alpha1 subunit staining of interneurons also disappeared after KA treatment, suggesting acute degeneration of these cells. Likewise, GAT1 immunoreactivity revealed degenerating terminals at 24 h post-KA in CA1 and DC and subsided almost completely thereafter. Loss of CA1 and, to a lesser extent, CA3 neurons became evident at 7-15 days post-KA. It was more accentuated after 1 month, accompanied by a corresponding reduction of GABA(A)-receptor staining. In contrast, DC granule cells were markedly enlarged and dispersed in the molecular layer and exhibited a prominent increase in GABA(A)-receptor subunit staining. After 4 months, the dorsal CA1 area was lost almost entirely, CA3 was reduced, and the DG represented most of the remaining dorsal hippocampal formation. No significant morphological alterations were detected contralaterally. These results suggest that loss of hilar cells and GABAergic neurons contributes to epileptogenesis in this model of MTLE. In contrast, long-term degeneration of

  3. Toxic effects of cadmium on GABA and taurine content in different brain areas of adult male rats.

    PubMed

    Lafuente, A; González-Carracedo, A; Cabaleiro, T; Romero, A; Esquifino, A I

    2005-09-01

    This work assesses the possible changes in gamma amino butyric acid (GABA) and taurine content in the hypothalamus, the median eminence and striatum after the exposure to various doses of cadmium. Cadmium chloride (CdCl2) was administered in the drinking water at the doses of 5, 10, 25, 50 or 100 ppm to adult male rats for 1 month. In the anterior hypothalamus, taurine and GABA content decreased with the dose of 10 ppm of CdCl2 only. Cadmium exposure decreased both GABA and taurine content in mediobasal hypothalamus except for the 50 ppm dose. In posterior hypothalamus GABA and taurine content was not affected by cadmium treatment. As far as the median eminence, 5 or 10 ppm of CdCl2 increased taurine concentration, and at a dose of 5 ppm enhanced GABA content. A significant decrease of GABA and taurine concentration was seen in the striatum at any dose of cadmium used. The concentration of cadmium increased in the hypothalamus and in the striatum in animals receiving CdCl2 in the drinking water at doses of 25, 50 or 100 ppm. The results indicate that cadmium globally decreased GABA and taurine content in the brain areas studied through effects that were not dose dependent.

  4. Mechanisms of GABA- and glycine-induced increases of cytosolic Ca2+ concentrations in chick embryo ciliary ganglion cells.

    PubMed

    Sorimachi, M; Rhee, J S; Shimura, M; Akaike, N

    1997-08-01

    We used fura-2 microfluorometry and the gramicidin-perforated patch clamp technique in an attempt to clarify the mechanisms underlying the GABA- and glycine-induced increases in the cytosolic Ca2+ concentration ([Ca]in) in acutely isolated chick embryo ciliary ganglion neurons. GABA, glycine, and isoguvacine, but not baclofen, increased [Ca]in in a dose- and a Ca2+-dependent manner. The GABA-induced [Ca]in increase was inhibited by bicuculline and picrotoxin, and potentiated by pentobarbital, flunitrazepam, and alphaxalone, whereas the glycine-induced [Ca]in increase was inhibited by strychnine but not by bicuculline or picrotoxin. L- and N-type Ca2+ channel blockers inhibited the GABA- and glycine-induced [Ca]in increases, whereas Bay K-8644 potentiated these responses. These responses were also substantially potentiated by blockers of various K+ channels and by lowering the external Cl- concentrations. The high KCI- and nicotine-induced [Ca]in increases were substantially reduced during continuous stimulation with either 2 microM GABA or 1 mM glycine. Electrophysiological studies indicated that the reversal potential of the GABA-induced current exhibited a more depolarized value than the resting membrane potential in 17 of the 25 cells examined. Taken together, these results suggest that both GABA and glycine depolarize the membrane potentials by increasing Cl- conductance via respective receptors and thus increase the Ca2+ influxes through L- and N-type voltage-dependent Ca2+ channels.

  5. Isolation and pharmacological analysis of two ionic forms of the GABA sub A /benzodiazepine receptor from rat brain

    SciTech Connect

    Moffett, J.R.

    1988-01-01

    The objective of this dissertation research was to investigate the ionic characteristics of solubilized, partially purified GABA{sub A} receptors, and to determine if physical variability within this receptor population was associated with ligand binding heterogeneity at the GABA and BZ binding sites. Utilizing BZ affinity chromatography, the GABA{sub A} receptor was partially purified from Triton X-100 solubilized rat brain membrane preparations. Anion exchange high performance liquid chromatography was employed to isolate two distinct ionic forms of the receptor, which remained stable and did not interconvert. Equilibrium binding assays with {sup 3}H-flunitrazepam, a BZ binding site agonist, and {sup 3}H-muscimol, a GABA binding site agonist, revealed no significant binding differences between these two ionic forms of the GABA{sub A} receptor. Type I and Type II GABA{sub A} receptor-have been distinguished by virtue of the differential sensitivity of their BZ binding site to the trizolopyridazine, CL 218,872. Competition of 3H-flunitrazepam binding by CL 218,872 in assays of the separated ionic forms of the GABA{sub A} receptor indicate that both high and low affinity CL 218,872 binding sites were present in both forms.

  6. Ultrastructure of GABA- and Tachykinin-Immunoreactive Neurons in the Lower Division of the Central Body of the Desert Locust

    PubMed Central

    Homberg, Uwe; Müller, Monika

    2016-01-01

    The central complex, a group of neuropils spanning the midline of the insect brain, plays a key role in spatial orientation and navigation. In the desert locust and other species, many neurons of the central complex are sensitive to the oscillation plane of polarized light above the animal and are likely involved in the coding of compass directions derived from the polarization pattern of the sky. Polarized light signals enter the locust central complex primarily through two types of γ-aminobutyric acid (GABA)-immunoreactive tangential neurons, termed TL2 and TL3 that innervate specific layers of the lower division of the central body (CBL). Candidate postsynaptic partners are columnar neurons (CL1) connecting the CBL to the protocerebral bridge (PB). Subsets of CL1 neurons are immunoreactive to antisera against locustatachykinin (LomTK). To better understand the synaptic connectivities of tangential and columnar neurons in the CBL, we studied its ultrastructural organization in the desert locust, both with conventional electron microscopy and in preparations immunolabeled for GABA or LomTK. Neuronal profiles in the CBL were rich in mitochondria and vesicles. Three types of vesicles were distinguished: small clear vesicles with diameters of 20–40 nm, dark dense-core vesicles (diameter 70–120 nm), and granular dense-core vesicles (diameter 70–80 nm). Neurons were connected via divergent dyads and, less frequently, through convergent dyads. GABA-immunoreactive neurons contained small clear vesicles and small numbers of dark dense core vesicles. They had both pre- and postsynaptic contacts but output synapses were observed more frequently than input synapses. LomTK immunostaining was concentrated on large granular vesicles; neurons had pre- and postsynaptic connections often with neurons assumed to be GABAergic. The data suggest that GABA-immunoreactive tangential neurons provide signals to postsynaptic neurons in the CBL, including LomTK-immunolabeled CL1

  7. Glycine and GABA(A) ultra-sensitive ethanol receptors as novel tools for alcohol and brain research.

    PubMed

    Naito, Anna; Muchhala, Karan H; Asatryan, Liana; Trudell, James R; Homanics, Gregg E; Perkins, Daya I; Davies, Daryl L; Alkana, Ronald L

    2014-12-01

    A critical obstacle to developing effective medications to prevent and/or treat alcohol use disorders is the lack of specific knowledge regarding the plethora of molecular targets and mechanisms underlying alcohol (ethanol) action in the brain. To identify the role of individual receptor subunits in ethanol-induced behaviors, we developed a novel class of ultra-sensitive ethanol receptors (USERs) that allow activation of a single receptor subunit population sensitized to extremely low ethanol concentrations. USERs were created by mutating as few as four residues in the extracellular loop 2 region of glycine receptors (GlyRs) or γ-aminobutyric acid type A receptors (GABA(A)Rs), which are implicated in causing many behavioral effects linked to ethanol abuse. USERs, expressed in Xenopus oocytes and tested using two-electrode voltage clamp, demonstrated an increase in ethanol sensitivity of 100-fold over wild-type receptors by significantly decreasing the threshold and increasing the magnitude of ethanol response, without altering general receptor properties including sensitivity to the neurosteroid, allopregnanolone. These profound changes in ethanol sensitivity were observed across multiple subunits of GlyRs and GABA(A)Rs. Collectively, our studies set the stage for using USER technology in genetically engineered animals as a unique tool to increase understanding of the neurobiological basis of the behavioral effects of ethanol.

  8. Functional role of ambient GABA in refining neuronal circuits early in postnatal development

    PubMed Central

    Cellot, Giada; Cherubini, Enrico

    2013-01-01

    Early in development, γ-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the mature brain, depolarizes and excites targeted neurons by an outwardly directed flux of chloride, resulting from the peculiar balance between the cation-chloride importer NKCC1 and the extruder KCC2. The low expression of KCC2 at birth leads to accumulation of chloride inside the cell and to the equilibrium potential for chloride positive respect to the resting membrane potential. GABA exerts its action via synaptic and extrasynaptic GABAA receptors mediating phasic and tonic inhibition, respectively. Here, recent data on the contribution of “ambient” GABA to the refinement of neuronal circuits in the immature brain have been reviewed. In particular, we focus on the hippocampus, where, prior to the formation of conventional synapses, GABA released from growth cones and astrocytes in a calcium- and SNARE (soluble N-ethylmaleimide-sensitive-factor attachment protein receptor)-independent way, diffuses away to activate in a paracrine fashion extrasynaptic receptors localized on distal neurons. The transient increase in intracellular calcium following the depolarizing action of GABA leads to inhibition of DNA synthesis and cell proliferation. Tonic GABA exerts also a chemotropic action on cell migration. Later on, when synapses are formed, GABA spilled out from neighboring synapses, acting mainly on extrasynaptic α5, β2, β3, and γ containing GABAA receptor subunits, provides the membrane depolarization necessary for principal cells to reach the window where intrinsic bursts are generated. These are instrumental in triggering calcium transients associated with network-driven giant depolarizing potentials which act as coincident detector signals to enhance synaptic efficacy at emerging GABAergic and glutamatergic synapses. PMID:23964205

  9. GABA+ levels in postmenopausal women with mild-to-moderate depression

    PubMed Central

    Wang, Zhensong; Zhang, Aiying; Zhao, Bin; Gan, Jie; Wang, Guangbin; Gao, Fei; Liu, Bo; Gong, Tao; Liu, Wen; Edden, Richard A.E.

    2016-01-01

    Abstract Background: It is increasingly being recognized that alterations of the GABAergic system are implicated in the pathophysiology of depression. This study aimed to explore in vivo gamma-aminobutyric acid (GABA) levels in the anterior cingulate cortex/medial prefrontal cortex (ACC/mPFC) and posterior-cingulate cortex (PCC) of postmenopausal women with depression using magnetic resonance spectroscopy (1H-MRS). Methods: Nineteen postmenopausal women with depression and thirteen healthy controls were enrolled in the study. All subjects underwent 1H-MRS of the ACC/mPFC and PCC using the “MEGA Point Resolved Spectroscopy Sequence” (MEGA-PRESS) technique. The severity of depression was assessed by 17-item Hamilton Depression Scale (HAMD). Quantification of MRS data was performed using Gannet program. Differences of GABA+ levels from patients and controls were tested using one-way analysis of variance. Spearman correlation coefficients were used to evaluate the linear associations between GABA+ levels and HAMD scores, as well as estrogen levels. Results: Significantly lower GABA+ levels were detected in the ACC/mPFC of postmenopausal women with depression compared to healthy controls (P = 0.002). No significant correlations were found between 17-HAMD/14-HAMA and GABA+ levels, either in ACC/mPFC (P = 0.486; r = 0.170/P = 0.814; r = −0.058) or PCC (P = 0.887; r = 0.035/ P = 0.987; r = −0.004) in the patients; there is also no significant correlation between GABA+ levels and estrogen levels in patients group (ACC/mPFC: P = 0.629, r = −0.018; PCC: P = 0.861, r = 0.043). Conclusion: Significantly lower GABA+ levels were found in the ACC/mPFC of postmenopausal women with depression, suggesting that the dysfunction of the GABAergic system may also be involved in the pathogenesis of depression in postmenopausal women. PMID:27684829

  10. Expression of functional receptors by the human γ-aminobutyric acid A γ2 subunit

    PubMed Central

    Martínez-Torres, Ataúlfo; Miledi, Ricardo

    2004-01-01

    γ-Aminobutyric acid A (GABAA) receptors are heteromeric membrane proteins formed mainly by various combinations of α, β, and γ subunits; and it is commonly thought that the γ2 subunit alone does not form functional receptors. In contrast, we found that cDNA encoding the γ2L subunit of the human GABAA receptor, injected alone into Xenopus oocytes, expressed functional GABA receptors whose properties were investigated by using the two-microelectrode voltage-clamp technique. GABA elicited desensitizing membrane currents that recovered after a few minutes' wash. Repetitive applications of GABA induced a “run-up” of GABA currents that nearly doubled the amplitude of the first response. The GABA currents inverted direction at about -30 mV, indicating that they are carried mainly by Cl- ions. The homomeric γ2L receptors were also activated by β-alanine > taurine > glycine, and, like some types of heteromeric GABAA receptors, the γ2L receptors were blocked by bicuculline and were potentiated by pentobarbital and flunitrazepam. These results indicate that the human γ2L subunit is capable of forming fully functional GABA receptors by itself in Xenopus oocytes and suggest that the roles proposed for the various subunits that make up the heteromeric GABAA receptors in situ require further clarification. PMID:14981251

  11. Intestinal Microbiota-Derived GABA Mediates Interleukin-17 Expression during Enterotoxigenic Escherichia coli Infection

    PubMed Central

    Ren, Wenkai; Yin, Jie; Xiao, Hao; Chen, Shuai; Liu, Gang; Tan, Bie; Li, Nengzhang; Peng, Yuanyi; Li, Tiejun; Zeng, Benhua; Li, Wenxia; Wei, Hong; Yin, Zhinan; Wu, Guoyao; Hardwidge, Philip R.; Yin, Yulong

    2017-01-01

    Intestinal microbiota has critical importance in pathogenesis of intestinal infection; however, the role of intestinal microbiota in intestinal immunity during enterotoxigenic Escherichia coli (ETEC) infection is poorly understood. The present study tested the hypothesis that the intestinal microbiota is associated with intestinal interleukin-17 (IL-17) expression in response to ETEC infection. Here, we found ETEC infection induced expression of intestinal IL-17 and dysbiosis of intestinal microbiota, increasing abundance of γ-aminobutyric acid (GABA)-producing Lactococcus lactis subsp. lactis. Antibiotics treatment in mice lowered the expression of intestinal IL-17 during ETEC infection, while GABA or L. lactis subsp. lactis administration restored the expression of intestinal IL-17. L. lactis subsp. lactis administration also promoted expression of intestinal IL-17 in germ-free mice during ETEC infection. GABA enhanced intestinal IL-17 expression in the context of ETEC infection through activating mechanistic target of rapamycin complex 1 (mTORC1)-ribosomal protein S6 kinase 1 (S6K1) signaling. GABA–mTORC1 signaling also affected intestinal IL-17 expression in response to Citrobacter rodentium infection and in drug-induced model of intestinal inflammation. These findings highlight the importance of intestinal GABA signaling in intestinal IL-17 expression during intestinal infection and indicate the potential of intestinal microbiota-GABA signaling in IL-17-associated intestinal diseases. PMID:28138329

  12. Functional Maturation of GABA Synapses During Postnatal Development of the Monkey Dorsolateral Prefrontal Cortex.

    PubMed

    Gonzalez-Burgos, Guillermo; Miyamae, Takeaki; Pafundo, Diego E; Yoshino, Hiroki; Rotaru, Diana C; Hoftman, Gil; Datta, Dibyadeep; Zhang, Yun; Hammond, Mahjub; Sampson, Allan R; Fish, Kenneth N; Ermentrout, G Bard; Lewis, David A

    2015-11-01

    Development of inhibition onto pyramidal cells may be crucial for the emergence of cortical network activity, including gamma oscillations. In primate dorsolateral prefrontal cortex (DLPFC), inhibitory synaptogenesis starts in utero and inhibitory synapse density reaches adult levels before birth. However, in DLPFC, the expression levels of γ-aminobutyric acid (GABA) synapse-related gene products changes markedly during development until young adult age, suggesting a highly protracted maturation of GABA synapse function. Therefore, we examined the development of GABA synapses by recording GABAAR-mediated inhibitory postsynaptic currents (GABAAR-IPSCs) from pyramidal cells in the DLPFC of neonatal, prepubertal, peripubertal, and adult macaque monkeys. We found that the decay of GABAAR-IPSCs, possibly including those from parvalbumin-positive GABA neurons, shortened by prepubertal age, while their amplitude increased until the peripubertal period. Interestingly, both GABAAR-mediated quantal response size, estimated by miniature GABAAR-IPSCs, and the density of GABAAR synaptic appositions, measured with immunofluorescence microscopy, were stable with age. Simulations in a computational model network with constant GABA synapse density showed that the developmental changes in GABAAR-IPSC properties had a significant impact on oscillatory activity and predicted that, whereas DLPFC circuits can generate gamma frequency oscillations by prepubertal age, mature levels of gamma band power are attained at late stages of development.

  13. Measurement of GABA and glutamate in vivo levels with high sensitivity and frequency.

    PubMed

    Zhang, Shan; Takeda, Yoshimasa; Hagioka, Shingo; Takata, Ken; Aoe, Hisami; Nakatsuka, Hideki; Yokoyama, Masataka; Morita, Kiyoshi

    2005-02-01

    In the present protocol, we demonstrate a high-performance liquid chromatography (HPLC) system that enables detection of very low amounts of gamma-aminobutyric acid (GABA) (0.03 pmol) and glutamate (0.8 pmol). The HPLC system consists of two pumps, an electrochemical detector, a high-pressure six-way switching valve, a guard column, a microbore column, and a column oven. A microdialysis probe was implanted in the right parietal cortex in rats. Dialysates were collected every 5 min and were split into two equal aliquots for separate analysis of GABA and glutamate. After derivatization with o-phthalaldehyde (OPA), samples were isocratically separated and purified by the guard column. To make the peak of GABA or glutamate appear in an opportune place in a chromatogram, a six-way switching valve was used to control the eluate containing GABA or glutamate to be led to the microbore column and electrochemical detector. By the use of this system, decrease in extracellular concentration of GABA, which precedes the appearance of electrical discharge initiated by hyperbaric oxygen (HBO2) exposure, was detected by microdialysis at the time resolution of 5 min.

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

    SciTech Connect

    Marley, R.J.

    1987-01-01

    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.

  15. Effect of pressure on (/sup 3/H)GABA release by synaptosomes isolated from cerebral cortex

    SciTech Connect

    Gilman, S.C.; Colton, J.S.; Hallenbeck, J.M.

    1986-12-01

    High hydrostatic pressure has been shown to produce neurological changes in humans which manifest, in part, as tremor, myoclonic jerks, electroencephalographic changes, and convulsions. This clinical pattern has been termed high-pressure nervous syndrome (HPNS). These symptoms may represent an alteration in synaptic transmission in the central nervous system with the inhibitory neural pathways being affected in particular. Since gamma-aminobutyric acid (GABA) transmission has been implicated in other seizure disorders, it was of interest to study GABAergic function at high pressure. Isolated synaptosomes were used to follow GABA release at 67.7 ATA of pressure. The major observation was a 33% depression in total (/sup 3/H)GABA efflux from depolarized cerebrocortical synaptosomes at 67.7 ATA. The Ca2+-dependent component of release was found to be completely blocked during the 1st min of (/sup 3/H)GABA efflux with a slow rise over the subsequent 3 min. These findings lead us to conclude that high pressure interferes with the intraterminal cascade for Ca2+-dependent release of GABA.

  16. Growth hormone response to the GABA-B agonist baclofen in 3-week abstinent alcoholics.

    PubMed

    Ozsoy, Saliha; Esel, Ertugrul; Turan, Tayfun; Kula, Mustafa

    2007-12-01

    Gamma-aminobutyric acid (GABA) dysfunction is a known feature of alcoholism. We investigated GABA-B receptor activity in 3-week abstinent alcoholics using the growth hormone (GH) response to baclofen, a GABA-B receptor agonist. The study aimed to investigate the relationship between GABA-B receptor activity and alcohol withdrawal. GH response to baclofen was measured in alcohol-dependent males without depression (n = 22) who were on day 21 of alcohol abstinence and in healthy control male subjects (n = 23). After 20mg baclofen was given orally to the subjects, blood samples for GH assay were obtained every 30 min for the subsequent 150 min. The patients were divided into two subgroups (continuing withdrawal and recovered withdrawal subgroups) according to their withdrawal symptom severity scores on day 21 of alcohol cessation. Baclofen administration significantly altered GH secretion in the controls, but not in the patients. When GH response to baclofen was assessed as DeltaGH, it was lower in the patients with continuing withdrawal symptoms than in the controls and in the recovered withdrawal group. Impaired GH response to baclofen in all patients mainly pertained to the patients whose withdrawal symptoms partly continued. Our results suggest that reduced GABA-B receptor activity might be associated with longer-term alcohol withdrawal symptoms in alcoholic patients.

  17. Early expression of GABA(A) receptor delta subunit in the neonatal rat hippocampus.

    PubMed

    Didelon, F; Mladinic', M; Cherubini, E; Bradbury, A

    2000-12-01

    The cDNA library screening strategy was used to identify the genes encoding for GABA(A) receptor subunits in the rat hippocampus during development. With this technique, genes encoding eleven GABA(A) receptor subunits were identified. The alpha5 subunit was by far the most highly expressed, followed by the gamma2, alpha2 and alpha4 subunits respectively. The expression of the beta2, alpha1, gamma1, beta1 and beta3 subunits was moderate, although that of the alpha3 and delta subunits was weak. In situ hybridization experiments, using digoxigenin-labeled cRNA probes, confirmed that the delta subunit was expressed in the neonatal as well as in the adult hippocampus, and is likely to form functional receptors in association with other subunits of the GABA(A) receptor. When the more sensitive RT-PCR approach was used, the gamma3 subunit was also detected, suggesting that this subunit is present in the hippocampus during development but at low levels of expression. The insertion of the delta subunit into functional GABA(A) receptors may enhance the efficacy of GABA in the immediate postnatal period when this amino acid is still exerting a depolarizing and excitatory action.

  18. Postsynaptic action of GABA in modulating sensory transmission in co-cultures of rat carotid body via GABAA receptors

    PubMed Central

    Zhang, Min; Clarke, Katherine; Zhong, Huijun; Vollmer, Cathy; Nurse, Colin A

    2009-01-01

    GABA is expressed in carotid body (CB) chemoreceptor type I cells and has previously been reported to modulate sensory transmission via presynaptic GABAB receptors. Because low doses of clinically important GABAA receptor (GABAAR) agonists, e.g. benzodiazepines, have been reported to depress afferent CB responses to hypoxia, we investigated the potential contribution of GABAAR in co-cultures of rat type I cells and sensory petrosal neurones (PNs). During gramicidin perforated-patch recordings (to preserve intracellular Cl−), GABA and/or the GABAA agonist muscimol (50 μm) induced a bicuculline-sensitive membrane depolarization in isolated PNs. GABA-induced whole-cell currents reversed at ∼−38 mV and had an EC50 of ∼10 μm (Hill coefficient =∼1) at −60 mV. During simultaneous PN and type I cell recordings at functional chemosensory units in co-culture, bicuculline reversibly potentiated the PN, but not type I cell, depolarizing response to hypoxia. Application of the CB excitatory neurotransmitter ATP (1 μm) over the soma of functional PN induced a spike discharge that was markedly suppressed during co-application with GABA (2 μm), even though GABA alone was excitatory. RT-PCR analysis detected expression of GABAergic markers including mRNA for α1, α2, β2, γ2S, γ2L and γ3 GABAAR subunits in petrosal ganglia extracts. Also, CB extracts contained mRNAs for GABA biosynthetic markers, i.e. glutamate decarboxylase (GAD) isoforms GAD 67A,E, and GABA transporter isoforms GAT 2,3 and BGT-1. In CB sections, sensory nerve endings apposed to type I cells were immunopositive for the GABAAR β subunit. These data suggest that GABA, released from the CB during hypoxia, inhibits sensory discharge postsynaptically via a shunting mechanism involving GABAA receptors. PMID:19029183

  19. Mutations in the GABA Transporter SLC6A1 Cause Epilepsy with Myoclonic-Atonic Seizures.

    PubMed

    Carvill, Gemma L; McMahon, Jacinta M; Schneider, Amy; Zemel, Matthew; Myers, Candace T; Saykally, Julia; Nguyen, John; Robbiano, Angela; Zara, Federico; Specchio, Nicola; Mecarelli, Oriano; Smith, Robert L; Leventer, Richard J; Møller, Rikke S; Nikanorova, Marina; Dimova, Petia; Jordanova, Albena; Petrou, Steven; Helbig, Ingo; Striano, Pasquale; Weckhuysen, Sarah; Berkovic, Samuel F; Scheffer, Ingrid E; Mefford, Heather C

    2015-05-07

    GAT-1, encoded by SLC6A1, is one of the major gamma-aminobutyric acid (GABA) transporters in the brain and is responsible for re-uptake of GABA from the synapse. In this study, targeted resequencing of 644 individuals with epileptic encephalopathies led to the identification of six SLC6A1 mutations in seven individuals, all of whom have epilepsy with myoclonic-atonic seizures (MAE). We describe two truncations and four missense alterations, all of which most likely lead to loss of function of GAT-1 and thus reduced GABA re-uptake from the synapse. These individuals share many of the electrophysiological properties of Gat1-deficient mice, including spontaneous spike-wave discharges. Overall, pathogenic mutations occurred in 6/160 individuals with MAE, accounting for ~4% of unsolved MAE cases.

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

    SciTech Connect

    Wafford, K.A.; Burnett, D.M.; Dunwiddie, T.V.; Harris, R.A. )

    1990-07-20

    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.

  1. Proton Magnetic Resonance Spectroscopy: Relevance of Glutamate and GABA to Neuropsychology.

    PubMed

    Ende, Gabriele

    2015-09-01

    Proton Magnetic Resonance Spectroscopy (MRS) has been widely used to study the healthy and diseased brain in vivo. The availability of whole body MR scanners with a field strength of 3 Tesla and above permit the quantification of many metabolites including the neurotransmitters glutamate (Glu) and γ-aminobutyric acid (GABA). The potential link between neurometabolites identified by MRS and cognition and behavior has been explored in numerous studies both in healthy subjects and in patient populations. Preliminary findings suggest direct or opposite associations between GABA or Glu with impulsivity, anxiety, and dexterity. This chapter is intended to provide an overview of basic principles of MRS and the literature reporting correlations between GABA or Glu and results of neuropsychological assessments.

  2. My close encounter with GABA(B) receptors.

    PubMed

    Nicoll, Roger A

    2004-10-15

    In this review, I summarize the sequence of events involved in characterizing the functional role of GABA(B) receptors in the CNS and their involvement in synaptic transmission. The story was launched with the realization that baclofen was a selective agonist of GABA(B) receptors. This lead to the discovery in the CNS that GABA(B) receptor activation could result in a presynaptic inhibition of transmitter release as well as a postsynaptic increase in potassium conductance. Based on this information, it was found that GABA also activated a potassium conductance. A role for GABA(B) receptors in synaptic transmission was suggested by the fact that activation of GABAergic interneurons could generate a slow IPSP mediated by an increase in potassium conductance. To link this slow IPSP to GABA(B) receptors required a selective GABA(B) antagonist. Phaclofen was the first antagonist developed and was found to antagonize the action of baclofen and the GABA(A) independent action of GABA. Most importantly, it blocked the slow IPSP. The properties of GABA(A) and GABA(B) IPSPs are remarkably different. GABA(A) IPSPs powerfully inhibit neurons and rapidly curtail excitatory inputs. This greatly enhances the precision of excitatory synaptic transmission. GABA(B) IPSPs are recruited with repetitive and synchronous activity and are postulated to modulate the rhythmic network activity of cortical tissue.

  3. Contribution of polyamines metabolism and GABA shunt to chilling tolerance induced by nitric oxide in cold-stored banana fruit.

    PubMed

    Wang, Yansheng; Luo, Zisheng; Mao, Linchun; Ying, Tiejin

    2016-04-15

    Effect of exogenous nitric oxide (NO) on polyamines (PAs) catabolism, γ-aminobutyric acid (GABA) shunt, proline accumulation and chilling injury of banana fruit under cold storage was investigated. Banana fruit treated with NO sustained lower chilling injury index than the control. Notably elevated nitric oxide synthetase activity and endogenous NO level were observed in NO-treated banana fruit. PAs contents in treated fruit were significantly higher than control fruit, due to the elevated activities of arginine decarboxylase and ornithine decarboxylase. NO treatment increased the activities of diamine oxidase, polyamine oxidase and glutamate decarboxylase, while reduced GABA transaminase activity to lower levels compared with control fruit, which resulted the accumulation of GABA. Besides, NO treatment upregulated proline content and significantly enhanced the ornithine aminotransferase activity. These results indicated that the chilling tolerance induced by NO treatment might be ascribed to the enhanced catabolism of PAs, GABA and proline.

  4. Effects of stress and tranylcypromine on amphetamine-induced locomotor activity and GABA(B) receptor function in rat brain.

    PubMed

    Sands, S A; Reisman, S A; Enna, S J

    2003-01-17

    Modification in gamma-aminobutyric acid-B (GABA(B)) receptors may contribute to the symptoms of some neurological and psychiatric disorders and to the clinical response to psychotherapeutics. The present study was undertaken to determine whether chronic administration of tranylcypromine (TCP), an antidepressant, and chronic stress influence GABA(B) receptor function in rat brain. The results indicate that TCP treatment, but not stress, increases GABA(B) receptor activity in the cerebral cortex, as measured by baclofen-stimulated GTPgammaS binding. In addition, chronic administration of TCP enhances significantly the locomotor response to a single dose of amphetamine, an effect that is abolished by restraint stress. These results indicate that although TCP administration modifies brain GABA(B) receptor activity, which may contribute to the antidepressant response to this agent, this effect is unrelated to the interaction of stress and TCP treatment on the locomotor response to amphetamine.

  5. “Brain MR spectroscopy in autism spectrum disorder—the GABA excitatory/inhibitory imbalance theory revisited”

    PubMed Central

    Brix, Maiken K.; Ersland, Lars; Hugdahl, Kenneth; Grüner, Renate; Posserud, Maj-Britt; Hammar, Åsa; Craven, Alexander R.; Noeske, Ralph; Evans, C. John; Walker, Hanne B.; Midtvedt, Tore; Beyer, Mona K.

    2015-01-01

    Magnetic resonance spectroscopy (MRS) from voxels placed in the left anterior cingulate cortex (ACC) was measured from 14 boys with Autism Spectrum Disorder (ASD) and 24 gender and age-matched typically developing (TD) control group. Our main aims were to compare the concentration of γ-aminobutyric acid (GABA) between the two groups, and to investigate the relationship between brain metabolites and autism symptom severity in the ASD group. We did find a significant negative correlation in the ASD group between Autism Spectrum Screening Questionnaire (ASSQ) and GABA+/Cr, which may imply that severity of symptoms in ASD is associated with differences in the level of GABA in the brain, supporting the excitatory/inhibitory (E/I) imbalance theory. However we did not find a significant difference between the two groups in GABA levels. PMID:26157380

  6. Coupling between agonist and chloride ionophore sites of the GABA(A) receptor: agonist/antagonist efficacy of 4-PIOL.

    PubMed

    Rabe, H; Picard, R; Uusi-Oukari, M; Hevers, W; Lüddens, H; Korpi, E R

    2000-12-15

    Eight gamma-aminobutyric acid (GABA) mimetics were tested on their ability to differentiate native GABA(A) receptor subtypes present in various rat brain regions. In rat brain cryostat sections, little regional variations by the agonistic actions of muscimol, thiomuscimol, 4,5,6,7-tetrahydroisoazolo(5,4-c)pyridin-3-ol, piperidine-4-sulphonic acid, taurine and beta-alanine on [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to GABA(A) receptor channels were found. They were very similar to those found for GABA itself and indicated no direct correlation with single subunit distributions for any of these compounds. Only the low-efficacy GABA mimetic 5-(4-piperidyl)isoxazol-3-ol (4-PIOL) acted like a weak partial agonist or antagonist depending on the brain area. As the cerebellar granule cell layer was relatively insensitive to both modes of action, we tested 4-PIOL in recombinant alpha1beta2gamma2 (widespread major subtype) and alpha6beta2gamma2 (cerebellar granule cell restricted) receptors where it had different effects on GABA-modulated [35S]TBPS binding and on electrophysiological responses. 4-PIOL may thus serve as a potential lead for receptor subtype selective compounds.

  7. Enhanced astroglial GABA uptake attenuates tonic GABAA inhibition of the presympathetic hypothalamic paraventricular nucleus neurons in heart failure.

    PubMed

    Pandit, Sudip; Jo, Ji Yoon; Lee, Sang Ung; Lee, Young Jae; Lee, So Yeong; Ryu, Pan Dong; Lee, Jung Un; Kim, Hyun-Woo; Jeon, Byeong Hwa; Park, Jin Bong

    2015-08-01

    γ-Aminobutyric acid (GABA) generates persistent tonic inhibitory currents (Itonic) and conventional inhibitory postsynaptic currents in the hypothalamic paraventricular nucleus (PVN) via activation of GABAA receptors (GABAARs). We investigated the pathophysiological significance of astroglial GABA uptake in the regulation of Itonic in the PVN neurons projecting to the rostral ventrolateral medulla (PVN-RVLM). The Itonic of PVN-RVLM neurons were significantly reduced in heart failure (HF) compared with sham-operated (SHAM) rats. Reduced Itonic sensitivity to THIP argued for the decreased function of GABAAR δ subunits in HF, whereas similar Itonic sensitivity to benzodiazepines argued against the difference of γ2 subunit-containing GABAARs in SHAM and HF rats. HF Itonic attenuation was reversed by a nonselective GABA transporter (GAT) blocker (nipecotic acid, NPA) and a GAT-3 selective blocker, but not by a GAT-1 blocker, suggesting that astroglial GABA clearance increased in HF. Similar and minimal Itonic responses to bestrophin-1 blockade in SHAM and HF neurons further argued against a role for astroglial GABA release in HF Itonic attenuation. Finally, the NPA-induced inhibition of spontaneous firing was greater in HF than in SHAM PVN-RVLM neurons, whereas diazepam induced less inhibition of spontaneous firing in HF than in SHAM neurons. Overall, our results showed that combined with reduced GABAARs function, the enhanced astroglial GABA uptake-induced attenuation of Itonic in HF PVN-RVLM neurons explains the deficit in tonic GABAergic inhibition and increased sympathetic outflow from the PVN during heart failure.

  8. Niflumic acid blocks native and recombinant T-type channels.

    PubMed

    Balderas, Enrique; Ateaga-Tlecuitl, Rogelio; Rivera, Manuel; Gomora, Juan C; Darszon, Alberto

    2012-06-01

    Voltage-dependent calcium channels are widely distributed in animal cells, including spermatozoa. Calcium is fundamental in many sperm functions such as: motility, capacitation, and the acrosome reaction (AR), all essential for fertilization. Pharmacological evidence has suggested T-type calcium channels participate in the AR. Niflumic acid (NA), a non-steroidal anti-inflammatory drug commonly used as chloride channel blocker, blocks T-currents in mouse spermatogenic cells and Cl(-) channels in testicular sperm. Here we examine the mechanism of NA blockade and explore if it can be used to separate the contribution of different Ca(V)3 members previously detected in these cells. Electrophysiological patch-clamp recordings were performed in isolated mouse spermatogenic cells and in HEK cells heterologously expressing Ca(V)3 channels. NA blocks mouse spermatogenic cell T-type currents with an IC(50) of 73.5 µM, without major voltage-dependent effects. The NA blockade is more potent in the open and in the inactivated state than in the closed state of the T-type channels. Interestingly, we found that heterologously expressed Ca(V)3.1 and Ca(V)3.3 channels were more sensitive to NA than Ca(V)3.2 channels, and this drug substantially slowed the recovery from inactivation of the three isoforms. Molecular docking modeling of drug-channel binding predicts that NA binds preferentially to the extracellular face of Ca(V)3.1 channels. The biophysical characteristics of mouse spermatogenic cell T-type currents more closely resemble those from heterologously expressed Ca(V)3.1 channels, including their sensitivity to NA. As Ca(V)3.1 null mice maintain their spermatogenic cell T-currents, it is likely that a novel Ca(V)3.2 isoform is responsible for them.

  9. NIFLUMIC ACID BLOCKS NATIVE AND RECOMBINANT T-TYPE CHANNELS

    PubMed Central

    Balderas, E; Arteaga-Tlecuitl, R; Rivera, M; Gomora, JC; Darszon, A

    2012-01-01

    Voltage-dependent calcium channels are widely distributed in animal cells, including spermatozoa. Calcium is fundamental in many sperm functions such as: motility, capacitation and the acrosome reaction, all essential for fertilization. Pharmacological evidence has suggested T-type calcium channels participate in the acrosome reaction. Niflumic acid (NA), a non-steroidal anti-inflammatory drug commonly used as chloride channel blocker, blocks T-currents in mouse spermatogenic cells and Cl− channels in testicular sperm. Here we examine the mechanism of NA blockade and explore if it can be used to separate the contribution of different CaV3 members previously detected in these cells. Electrophysiological patch-clamp recordings were performed in isolated mouse spermatogenic cells and in HEK cells heterologously expressing CaV3 channels. NA blocks mouse spermatogenic cell T-type currents with an IC50 of 73.5 µM, without major voltage-dependent effects. The NA blockade is more potent in the open and in the inactivated state than in the closed state of the T-type channels. Interestingly, we found that heterologously expressed CaV3.1 and CaV3.3 channels were more sensitive to NA than CaV3.2 channels, and this drug substantially slowed the recovery from inactivation of the three isoforms. Molecular docking modeling of drug-channel binding predicts that NA binds preferentially to the extracellular face of CaV3.1 channels. The biophysical characteristics of mouse spermatogenic cell T-type currents more closely resemble those from heterologously expressed CaV3.1 channels, including their sensitivity to NA. As CaV3.1 null mice maintain their spermatogenic cell T-currents, it is likely that a novel CaV3.2 isoform is responsible for them. PMID:21898399

  10. Effect of THIP and SL 76002, two clinically experimented GABA-mimetic compounds, on anterior pituitary GABA receptors and prolactin secretion in the rat

    SciTech Connect

    Apud, J.A.; Masotto, C.; Racagni, G.

    1987-03-02

    In the present study, the ability of three direct GABA agonists, muscimol, THIP and SL 76002 to displace /sup 3/H-GABA binding from anterior pituitary and medio-basal hypothalamus membranes was evaluated. Further, the effect of both THIP and SL 76002 on baseline prolactin levels or after stimulation of hormone release with haloperidol has been also studied. Either muscimol, THIP or SL 76002 have shown to posses 7-, 7- and 3-fold higher affinity, respectively, for the central nervous system than for the anterior pituitary /sup 3/H-GABA binding sites. Moreover, THIP and SL 76002 have demonstrated to be respectively, 25- and 1000- fold less potent than muscimol in inhibiting /sup 3/H- GABA binding at the level of the anterior pituitary and about 25- and 2700-fold less potent at the level of the medio-basal hypothalamus. Under basal conditions, either THIP or SL 76002 were ineffective to reduce prolactin release. However, after stimulation of prolactin secretion through blockade of the dopaminergic neurotransmission with haloperidol (0.1 mg/kg), both THIP (10 mg/kg) and SL 76002 (200 mg/kg) significantly counteracted the neuroleptic-induced prolactin rise with a potency which is in line with their ability to inhibit /sup 3/H-GABA binding in the anterior pituitary. The present results indicate that both compounds inhibit prolactin release under specific experimental situations probably through a GABAergic mechanism. In view of the endocrine effects of these GABA-mimetic compounds, the possibility arises for an application of these type of drugs in clinical neuroendocrinology. 35 references, 3 figures, 2 tables.

  11. GABA B receptor modulation of excitatory and inhibitory synaptic transmission onto rat CA3 hippocampal interneurons.

    PubMed

    Lei, Saobo; McBain, Chris J

    2003-01-15

    Hippocampal stratum radiatum inhibitory interneurons receive glutamatergic excitatory innervation via the recurrent collateral fibers of CA3 pyramidal neurons and GABAergic inhibition from other interneurons. We examined both presynaptic- and postsynaptic-GABA(B) receptor-mediated responses at both synapse types. Postsynaptic GABA(B) receptor-mediated responses were absent in recordings from young (P16-18) but present in recordings from older animals (> or =P30) suggesting developmental regulation. In young animals, the GABA(B) receptor agonist, baclofen, inhibited the amplitude of evoked EPSCs and IPSCs, an effect blocked by prior application of the selective antagonist CGP55845. Baclofen enhanced the paired-pulse ratio and coefficient of variation of evoked EPSCs and IPSCs, consistent with a presynaptic mechanism of regulation. In addition, baclofen reduced the frequency of miniature IPSCs but not mEPSCs. However, baclofen reduced the frequency of KCl-induced mEPSCs; an effect blocked by Cd(2+), implicating presynaptic voltage-gated Ca(2+) channels as a target for baclofen modulation. In contrast, although Cd(2+) prevented the KCl-induced increase in mIPSC frequency, it failed to block baclofen's reduction of mIPSC frequency. Whereas N- and P/Q-types of Ca(2+) channels contributed equally to GABA(B) receptor-mediated inhibition of EPSCs, more P/Q-type Ca(2+) channels were involved in GABA(B) receptor-mediated inhibition of IPSCs. Finally, baclofen blocked the frequency-dependent depression of EPSCs and IPSCs, but was less effective at blocking frequency-dependent facilitation of EPSCs. Our results demonstrate that presynaptic GABA(B) receptors are expressed on the terminals of both excitatory and inhibitory synapses onto CA3 interneurons and that their activation modulates essential components of the release process underlying transmission at these two synapse types.

  12. Protection of malonate-induced GABA but not dopamine loss by GABA transporter blockade in rat striatum.

    PubMed

    Zeevalk, Gail D; Manzino, Lawrence; Sonsalla, Patricia K

    2002-07-01

    Previous work has shown that overstimulation of GABA(A) receptors can potentiate neuronal cell damage during excitotoxic or metabolic stress in vitro and that GABA(A) antagonists or GABA transport blockers are neuroprotective under these situations. Malonate, a reversible succinate dehydrogenase/mitochondrial complex II inhibitor, is frequently used in animals to model cell loss in neurodegenerative diseases such as Parkinson's and Huntington's diseases. To determine if GABA transporter blockade during mitochondrial impairment can protect neurons in vivo as compared with in vitro studies, rats received a stereotaxic infusion of malonate (2 micromol) into the left striatum to induce a metabolic stress. The nonsubstrate GABA transport blocker, NO711 (20 nmol) was infused in some rats 30 min before and 3 h following malonate infusion. After 1 week, dopamine and GABA levels in the striata were measured. Malonate caused a significant loss of striatal dopamine and GABA. Blockade of the GABA transporter significantly attenuated GABA, but not dopamine loss. In contrast with several in vitro reports, GABA(A) receptors were not a downstream mediator of protection by NO711. Intrastriatal infusion of malonate (2 micromol) plus or minus the GABA(A) receptor agonist muscimol (1 micromol), the GABA(A) Cl- binding site antagonist picrotoxin (50 nmol) or the GABA(B) receptor antagonist saclofen (33 nmol) did not modify loss of striatal dopamine or GABA when examined 1 week following infusion. These data show that GABA transporter blockade during mitochondrial impairment in the striatum provides protection to GABAergic neurons. GABA transporter blockade, which is currently a pharmacological strategy for the treatment of epilepsy, may thus also be beneficial in the treatment of acute and chronic conditions involving energy inhibition such as stroke/ischemia or Huntington's disease. These findings also point to fundamental differences between immature and adult neurons in the

  13. Excitatory action of GABA on immature neurons is not due to absence of ketone bodies metabolites or other energy substrates.

    PubMed

    Ben-Ari, Yehezkel; Tyzio, Roman; Nehlig, Astrid

    2011-09-01

    Brain slices incubated with glucose have provided most of our knowledge on cellular, synaptic, and network driven mechanisms. It has been recently suggested that γ-aminobutyric acid (GABA) excites neonatal neurons in conventional glucose-perfused slices but not when ketone bodies metabolites, pyruvate, and/or lactate are added, suggesting that the excitatory actions of GABA are due to energy deprivation when glucose is the sole energy source. In this article, we review the vast number of studies that show that slices are not energy deprived in glucose-containing medium, and that addition of other energy substrates at physiologic concentrations does not alter the excitatory actions of GABA on neonatal neurons. In contrast, lactate, like other weak acids, can produce an intracellular acidification that will cause a reduction of intracellular chloride and a shift of GABA actions. The effects of high concentrations of lactate, and particularly of pyruvate (4-5 mm), as used are relevant primarily to pathologic conditions; these concentrations not being found in the brain in normal "control" conditions. Slices in glucose-containing medium may not be ideal, but additional energy substrates neither correspond to physiologic conditions nor alter GABA actions. In keeping with extensive observations in a wide range of animal species and brain structures, GABA depolarizes immature neurons and the reduction of the intracellular concentration of chloride ([Cl(-)](i)) is a basic property of brain maturation that has been preserved throughout evolution. In addition, this developmental sequence has important clinical implications, notably concerning the higher incidence of seizures early in life and their long-lasting deleterious sequels. Immature neurons have difficulties exporting chloride that accumulates during seizures, leading to permanent increase of [Cl(-)](i) that converts the inhibitory actions of GABA to excitatory and hampers the efficacy of GABA-acting antiepileptic

  14. Taurine activates GABA(A) but not GABA(B) receptors in rat hippocampal CA1 area.

    PubMed

    del Olmo, N; Bustamante, J; del Río, R M; Solís, J M

    2000-05-12

    We investigated if taurine, an endogenous GABA analog, could mimic both hyperpolarizing and depolarizing GABA(A)-mediated responses as well as pre- and postsynaptic GABA(B)-mediated actions in the CA1 region of rat hippocampal slices. Taurine (10 mM) perfusion induced changes in membrane potential and input resistance that are compatible with GABA(A) receptor activation. Local pressure application of taurine and GABA from a double barrel pipette positioned along the dendritic shaft of pyramidal cells revealed that taurine evoked a very small change of membrane potential and resistance compared with the large changes induced by GABA in these parameters. Moreover, in the presence of GABA(A) antagonists, local application of GABA on the dendrites evoked a GABA(B)-mediated hyperpolarization while taurine did not induce any change. Taurine neither mimicked baclofen inhibitory actions on presynaptic release of glutamate and GABA as judging by the lack of taurine effect on paired-pulse facilitation ratio and slow inhibitory postsynaptic potentials, respectively. These results show that taurine mainly activates GABA(A) receptors located on the cell body, indicating therefore that if taurine has any action on the dendrites it will not be mediated by either GABA(A) or GABA(B) receptors activation.

  15. Advantages of an antagonist: bicuculline and other GABA antagonists

    PubMed Central

    Johnston, Graham AR

    2013-01-01

    The convulsant alkaloid bicuculline continues to be investigated more than 40 years after the first publication of its action as an antagonist of receptors for the inhibitory neurotransmitter GABA. This historical perspective highlights key aspects of the discovery of bicuculline as a GABA antagonist and the sustained interest in this and other GABA antagonists. The exciting advances in the molecular biology, pharmacology and physiology of GABA receptors provide a continuing stimulus for the discovery of new antagonists with increasing selectivity for the myriad of GABA receptor subclasses. Interesting GABA antagonists not structurally related to bicuculline include gabazine, salicylidene salicylhydrazide, RU5135 and 4-(3-biphenyl-5-(4-piperidyl)-3-isoxazole. Bicuculline became the benchmark antagonist for what became known as GABAA receptors, but not all ionotropic GABA receptors are susceptible to bicuculline. In addition, not all GABAA receptor antagonists are convulsants. Thus there are still surprises in store as the study of GABA receptors evolves. PMID:23425285

  16. Type I and type II fatty acid biosynthesis in Eimeria tenella: enoyl reductase activity and structure.

    PubMed

    Lu, J Z; Muench, S P; Allary, M; Campbell, S; Roberts, C W; Mui, E; McLeod, R L; Rice, D W; Prigge, S T

    2007-12-01

    Apicomplexan parasites of the genus Eimeria are the major causative agent of avian coccidiosis, leading to high economic losses in the poultry industry. Recent results show that Eimeria tenella harbours an apicoplast organelle, and that a key biosynthetic enzyme, enoyl reductase, is located in this organelle. In related parasites, enoyl reductase is one component of a type II fatty acid synthase (FAS) and has proven to be an attractive target for antimicrobial compounds. We cloned and expressed the mature form of E. tenella enoyl reductase (EtENR) for biochemical and structural studies. Recombinant EtENR exhibits NADH-dependent enoyl reductase activity and is inhibited by triclosan with an IC50 value of 60 nm. The crystal structure of EtENR reveals overall similarity with other ENR enzymes; however, the active site of EtENR is unoccupied, a state rarely observed in other ENR structures. Furthermore, the position of the central beta-sheet appears to block NADH binding and would require significant movement to allow NADH binding, a feature not previously seen in the ENR family. We analysed the E. tenella genomic database for orthologues of well-characterized bacterial and apicomplexan FAS enzymes and identified 6 additional genes, suggesting that E. tenella contains a type II FAS capable of synthesizing saturated, but not unsaturated, fatty acids. Interestingly, we also identified sequences that appear to encode multifunctional type I FAS enzymes, a feature also observed in Toxoplasma gondii, highlighting the similarity between these apicomplexan parasites.

  17. Epileptiform activity in the CA1 region of the hippocampus becomes refractory to attenuation by cannabinoids in part because of endogenous γ-aminobutyric acid type B receptor activity.

    PubMed

    Messer, Ricka D; Levine, Eric S

    2012-07-01

    The anticonvulsant properties of marijuana have been known for centuries. The recently characterized endogenous cannabinoid system thus represents a promising target for novel anticonvulsant agents; however, administration of exogenous cannabinoids has shown mixed results in both human epilepsy and animal models. The ability of cannabinoids to attenuate release of both excitatory and inhibitory neurotransmitters may explain the variable effects of cannabinoids in different models of epilepsy, but this has not been well explored. Using acute mouse brain slices, we monitored field potentials in the CA1 region of the hippocampus to characterize systematically the effects of the cannabinoid agonist WIN55212-2 (WIN) on evoked basal and epileptiform activity. WIN, acting presynaptically, significantly reduced the amplitude and slope of basal field excitatory postsynaptic potentials as well as stimulus-evoked epileptiform responses induced by omission of magnesium from the extracellular solution. In contrast, the combination of omission of magnesium plus elevation of potassium induced an epileptiform response that was refractory to attenuation by WIN. The effect of WIN in this model was partially restored by blocking γ-aminobutyric acid type B (GABA(B) ), but not GABA(A) , receptors. Subtle differences in models of epileptiform activity can profoundly alter the efficacy of cannabinoids. Endogenous GABA(B) receptor activation played a role in the decreased cannabinoid sensitivity observed for epileptiform activity induced by omission of magnesium plus elevation of potassium. These results suggest that interplay between presynaptic G protein-coupled receptors with overlapping downstream targets may underlie the variable efficacy of cannabinoids in different models of epilepsy.

  18. Trophic actions of GABA on neuronal development.

    PubMed

    Represa, Alfonso; Ben-Ari, Yehezkel

    2005-06-01

    During brain development, transmitter-gated receptors are operative before synapse formation, suggesting that their action is not restricted to synaptic transmission. GABA, which is the principal excitatory transmitter in the developing brain, acts as an epigenetic factor to control processes including cell proliferation, neuroblast migration and dendritic maturation. These effects appear to be mediated through a paracrine, diffuse, non-synaptic mode of action that precedes the more focused, rapid mode of operation characteristic of synaptic connections. This sequential operation implies that GABA is used as an informative agent but in a unique context at an early developmental stage. This sequence also implies that by altering these effects, drugs acting on the GABA system could be pathogenic during pregnancy.

  19. An excitatory GABA loop operating in vivo

    PubMed Central

    Astorga, Guadalupe; Bao, Jin; Marty, Alain; Augustine, George J.; Franconville, Romain; Jalil, Abdelali; Bradley, Jonathan; Llano, Isabel

    2015-01-01

    While it has been proposed that the conventional inhibitory neurotransmitter GABA can be excitatory in the mammalian brain, much remains to be learned concerning the circumstances and the cellular mechanisms governing potential excitatory GABA action. Using a combination of optogenetics and two-photon calcium imaging in vivo, we find that activation of chloride-permeable GABAA receptors in parallel fibers (PFs) of the cerebellar molecular layer of adult mice causes parallel fiber excitation. Stimulation of PFs at submaximal stimulus intensities leads to GABA release from molecular layer interneurons (MLIs), thus creating a positive feedback loop that enhances excitation near the center of an activated PF bundle. Our results imply that elevated chloride concentration can occur in specific intracellular compartments of mature mammalian neurons and suggest an excitatory role for GABAA receptors in the cerebellar cortex of adult mice. PMID:26236197

  20. Homomeric RDL and heteromeric RDL/LCCH3 GABA receptors in the honeybee antennal lobes: two candidates for inhibitory transmission in olfactory processing.

    PubMed

    Dupuis, Julien Pierre; Bazelot, Michaël; Barbara, Guillaume Stéphane; Paute, Sandrine; Gauthier, Monique; Raymond-Delpech, Valérie

    2010-01-01

    gamma-Aminobutyric acid (GABA)-gated chloride channel receptors are abundant in the CNS, where their physiological role is to mediate fast inhibitory neurotransmission. In insects, this inhibitory transmission plays a crucial role in olfactory information processing. In an effort to understand the nature and properties of the ionotropic receptors involved in these processes in the honeybee Apis mellifera, we performed a pharmacological and molecular characterization of GABA-gated channels in the primary olfactory neuropile of the honeybee brain-the antennal lobe (AL)-using whole cell patch-clamp recordings coupled with single-cell RT-PCR. Application of GABA onto AL cells at -110 mV elicited fast inward currents, demonstrating the existence of ionotropic GABA-gated chloride channels. Molecular analysis of the GABA-responding cells revealed that both subunits RDL and LCCH3 were expressed out of the three orthologs of Drosophila melanogaster GABA-receptor subunits encoded within the honeybee genome (RDL, resistant to dieldrin; GRD, GABA/glycine-like receptor of Drosophila; LCCH3, ligand-gated chloride channel homologue 3), opening the door to possible homo- and/or heteromeric associations. The resulting receptors were activated by insect GABA-receptor agonists muscimol and CACA and blocked by antagonists fipronil, dieldrin, and picrotoxin, but not bicuculline, displaying a typical RDL-like pharmacology. Interestingly, increasing the intracellular calcium concentration potentiated GABA-elicited currents, suggesting a modulating effect of calcium on GABA receptors possibly through phosphorylation processes that remain to be determined. These results indicate that adult honeybee AL cells express typical RDL-like GABA receptors whose properties support a major role in synaptic inhibitory transmission during olfactory information processing.

  1. Excitatory actions of GABA in developing chick vestibular afferents: effects on resting electrical activity.

    PubMed

    Cortes, Celso; Galindo, Fabian; Galicia, Salvador; Cebada, Jorge; Flores, Amira

    2013-07-01

    The aim of this study was to characterize the effect of γ-aminobutyric acid (GABA) in the resting multiunit activity of the vestibular afferents during development using the isolated inner ear of embryonic and postnatal chickens (E15-E21 and P5). GABA (10(-3) to 10(-5) M; n = 133) and muscimol (10(-3) M) elicited an increase in the frequency of the basal discharge of the vestibular afferents. We found that GABA action was dose-dependent and inversely related to animal age. Thus, the largest effect was observed in embryonic ages such as E15 and E17 and decreases in E21 and P5. The GABAA receptor antagonists, bicuculline (10(-5) M; n = 10) and picrotoxin (10(-4) M; n = 10), significantly decreased the excitatory action of GABA and muscimol (10(-3) M). Additionally, CNQX 10(-6) M, MCPG 10(-5) M and 7ClKyn 10(-5) M (n = 5) were co-applied by bath substitution (n = 5). Both the basal discharge and the GABA action significantly decreased in these experimental conditions. The chloride channel blocker 9-AC 0.5 mM produced an important reduction in the effect of GABA 10(-3) (n = 5) and 10(-4) M (n = 5). Thus, our results suggest an excitatory role of GABA in the resting activity of the vestibular afferents that can be explained by changes in the gradient of concentration of Cl(-) during development. We show for the first time that the magnitude of this GABA effect decreases at later stages of embryonic and early postnatal development. Taking into account the results with glutamatergic antagonists, we conclude that GABA has a presynaptic action but is not the neurotransmitter in the vestibular afferent synapses, although it could act as a facilitator of the spontaneous activity and may regulate glutamate release.

  2. Toward amino acid typing for proteins in FFLUX.

    PubMed

    Fletcher, Timothy L; Popelier, Paul L A

    2017-03-05

    Continuing the development of the FFLUX, a multipolar polarizable force field driven by machine learning, we present a modern approach to atom-typing and building transferable models for predicting atomic properties in proteins. Amino acid atomic charges in a peptide chain respond to the substitution of a neighboring residue and this response can be categorized in a manner similar to atom-typing. Using a machine learning method called kriging, we are able to build predictive models for an atom that is defined, not only by its local environment, but also by its neighboring residues, for a minimal additional computational cost. We found that prediction errors were up to 11 times lower when using a model specific to the correct group of neighboring residues, with a mean prediction of ∼0.0015 au. This finding suggests that atoms in a force field should be defined by more than just their immediate atomic neighbors. When comparing an atom in a single alanine to an analogous atom in a deca-alanine helix, the mean difference in charge is 0.026 au. Meanwhile, the same difference between a trialanine and a deca-alanine helix is only 0.012 au. When compared to deca-alanine models, the transferable models are up to 20 times faster to train, and require significantly less ab initio calculation, providing a practical route to modeling large biological systems. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

  3. Embryonic and postnatal development of GABA, calbindin, calretinin, and parvalbumin in the mouse claustral complex.

    PubMed

    Dávila, José Carlos; Real, M Angeles; Olmos, Luis; Legaz, Isabel; Medina, Loreta; Guirado, Salvador

    2005-01-03

    We analyzed the development of immunoreactive expression patterns for the neurotransmitter gamma-aminobutyric acid (GABA) and the calcium-binding proteins calbindin, calretinin, and parvalbumin in the embryonic and postnatal mouse claustral complex. Each calcium-binding protein shows a different temporal and spatial pattern of development. Calbindin-positive cells start to be seen very early during embryogenesis and increase dramatically until birth, thus becoming the most abundant cell type during embryonic development, especially in the ventral pallial part of the claustrum. The distribution of calbindin neurons throughout the claustrum during embryonic development partly parallels that of GABA neurons, suggesting that at least part of the calbindin neurons of the claustral complex are GABAergic and originate in the subpallium. Parvalbumin cells, on the other hand, start to be seen only postnatally, and their number then increases while the density of calbindin neurons decreases. Based on calretinin expression in axons, the core/shell compartments of the dorsal claustrum start to be clearly seen at embryonic day 18.5 and may be related to the development of the thalamoclaustral input. Comparison with the expression of Cadherin 8, a marker of the developing dorsolateral claustrum, indicates that the core includes a central part of the dorsolateral claustrum, whereas the shell includes a peripheral area of the dorsolateral claustrum, plus the adjacent ventromedial claustrum. The present data on the spatiotemporal developmental patterns of several subtypes of GABAergic neurons in the claustral complex may help for future studies on temporal lobe epilepsies, which have been related to an alteration of the GABAergic activity.

  4. Ca2+ activity at GABAB receptors constitutively promotes metabotropic glutamate signaling in the absence of GABA

    PubMed Central

    Tabata, Toshihide; Araishi, Kenji; Hashimoto, Kouichi; Hashimotodani, Yuki; van der Putten, Herman; Bettler, Bernhard; Kano, Masanobu

    2004-01-01

    Type B γ-aminobutyric acid receptor (GABABR) is a G protein-coupled receptor that regulates neurotransmitter release and neuronal excitability throughout the brain. In various neurons, GABABRs are concentrated at excitatory synapses. Although these receptors are assumed to respond to GABA spillover from neighboring inhibitory synapses, their function is not fully understood. Here we show a previously undescribed function of GABABR exerted independent of GABA. In cerebellar Purkinje cells, interaction of GABABR with extracellular Ca2+ (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{Ca}}_{{\\mathrm{o}}}^{2+}\\end{equation*}\\end{document}) leads to a constitutive increase in the glutamate sensitivity of metabotropic glutamate receptor 1 (mGluR1). mGluR1 sensitization is clearly mediated by GABABR because it is absent in GABABR1 subunit-knockout cells. However, the mGluR1 sensitization does not require Gi/o proteins that mediate the GABABR's classical functions. Moreover, coimmunoprecipitation reveals complex formation between GABABR and mGluR1 in the cerebellum. These findings demonstrate that GABABR can act as \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{Ca}}_{{\\mathrm{o}}}^{2+}\\end{equation*}\\end{document}-dependent cofactors to enhance neuronal metabotropic glutamate signaling. PMID:15550547

  5. Effects of taurine, homotaurine and GABA on hypothalamic and striatal dopamine metabolism.

    PubMed

    Panula-Lehto, E; Mäkinen, M; Ahtee, L

    1992-07-01

    To elucidate the effects of taurine on hypothalamic and striatal dopaminergic neurotransmission we compared its effects to those of gamma-aminobutyric acid (GABA) and homotaurine (a GABAA-receptor agonist) on hypothalamic and striatal concentrations of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and, in the case of striatum, 3-methoxytyramine (3-MT) in rats. In addition, hypothalamic and striatal 5-hydroxytryptamine (5-HT) und 5-hydroxyindoleacetic acid, hypothalamic noradrenaline (NA) and 3-methoxy-4-hydroxyphenylglycol sulfate, and pituitary DA concentrations were also measured. The amino acids were injected into the lateral brain ventricles of conscious male rats in doses of 10 and 36 mumol/rat, and rat were sacrificed 15 and 60 min later, respectively. Homotaurine (by 11%) but not the other two amino acids elevated striatal DA, whereas hypothalamic DA was increased by both taurine (36%) and homotaurine (31%). All three amino acids at 36 mumol elevated striatal DOPAC, homotaurine (51%) more than taurine (31%) or GABA (30%), and hypothalamic DOPAC, both taurine (102%) and homotaurine (82%) clearly more than GABA (34%). Neither striatal nor hypothalamic HVA was altered by any of the amino acids. At 10 mumol the amino acids decreased striatal 3-MT by about 40%. At 36 mumol taurine and homotaurine reduced 3-MT by about 70%, whereas increasing the dose of GABA did not further reduce 3-MT. Both taurine and homotaurine at 36 mumol decreased hypothalamic NA content. Neither hypothalamic nor striatal 5-HT metabolism was altered. In the neurointermediate lobe of the pituitary gland taurine at 10 mumol but not at 36 mumol slightly (20%) increased DA.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Generation of a 3D model for human GABA transporter hGAT-1 using molecular modeling and investigation of the binding of GABA.

    PubMed

    Wein, Thomas; Wanner, Klaus T

    2010-01-01

    A three-dimensional model of the human Na(+)/Cl(-)-dependent gamma-aminobutyric acid (GABA) transporter hGAT-1 was developed by homology modeling and refined by subsequent molecular modeling using the crystal structure of a bacterial homologue leucine transporter from Aquifex aeolicus (LeuT(Aa)) as the template. Protein structure quality checks show that the resulting structure is particularly suited for the analysis of the substrate binding pocket and virtual screening experiments. Interactions of GABA and the substrate binding pocket were investigated using docking studies. The difference of 6 out of 13 substrate interacting side chains between hGAT-1 and LeuT(Aa) lead to the different substrate preference which can be explained using our three-dimensional model of hGAT-1. In particular the replacement of serine 256 and isoleucine 359 in LeuT(Aa) with glycine and threonine in hGAT-1 seems to facilitate the selection of GABA as the main substrate by changing the hydrogen bonding pattern in the active site to the amino group of the substrate. For a set of 12 compounds flexible docking experiments were performed using LigandFit in combination with the Jain scoring function. With few exceptions the obtained rank order of potency was in line with experimental data. Thus, the method can be assumed to give at least a rough estimate of the potency of the potential of GABA uptake inhibitors.

  7. Experiment K-7-21: Effect of Microgravity on 1: Metabolic Enzymes of Type 1 and Type 2 Muscle Fibers, and on 2: Metabolic Enzymes, Neurotransmitter Amino Acids, and Neurotransmitter Associated Enzymes in Selected Regions of the Central Nervous System. Part 2; The Distribution of Selected Enzymes and Amino Acids in the Hippocampal Formation

    NASA Technical Reports Server (NTRS)

    Lowry, O. H.; Krasnov, I.; Ilyina-Kakueva, E. I.; Nemeth, P. M.; McDougal, D. B., Jr.; Choksi, R.; Carter, J. G.; Chi, M. M. Y.; Manchester, J. K.; Pusateri, M. E.

    1994-01-01

    Six key metabolic enzymes plus glutaminase and glutamate decarboxylase, as well as glutamate, aspartate and GABA, were measured in 11 regions of the hippocampal formation of synchronous, flight and tail suspension rats. Major differences were observed in the normal distribution patterns of each enzyme and amino acid, but no substantive effects of either microgravity or tail suspension on these patterns were clearly demonstrated.

  8. GABA-related actions in isolated in vitro preparations of the rat small intestine.

    PubMed

    Krantis, A; Harding, R K

    1987-09-11

    Longitudinal organ bath preparations of the rat duodenum, jejunum and ileum were tested for their responsiveness to GABA-receptor agonists. The GABAA-receptor agonists, GABA and 3APS, induced non-adrenergic, non-cholinergic relaxations and/or contractions, although the magnitude and type of response varied depending upon the region tested. All regions relaxed to applied GABA or 3APS, however the jejunum and ileum also responded with cholinergic contractions. These relaxant and contractile actions were neurogenic and sensitive to blockade by the GABA antagonists bicuculline or picrotoxinin, and desensitization to either agonist. The GABAB-receptor agonist baclofen, caused a reduction in electrically evoked cholinergic contractions. These inhibitory actions of baclofen were insensitive to bicuculline or picrotoxinin. Taken together, these results show that GABA-ergic actions in the rat small intestine are mediated by two pharmacologically distinct neural receptor populations, the GABAA and GABAB sites, the distribution and sensitivity of which differ along the length of the small intestine.

  9. GABA-ergic neurons in the leach central nervous system

    SciTech Connect

    Cline, H.T.

    1985-01-01

    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.

  10. 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

    Asinof, Samuel K; Paine, Tracie A

    2013-02-01

    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 γ-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 μg/0.5 μl/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.

  11. Salicylic acid retention impairs aspirin reactivity in type 2 diabetes.

    PubMed

    Zhang, Haowen; Xie, Hao; Zheng, Xiao; Chai, Yingying; Tang, Zhiyuan; Chen, Hanyu; Li, Feiyan; Christoph, Heier; Chen, Jiandong; Sun, Weixin; Ye, Hui; Wang, Shiguang; Hao, Haiping; Chen, Xiaohu

    2017-01-05

    High on-aspirin platelet reactivity (HAPR) has been associated with compromised aspirin efficacy in patients with diabetes suffering from acute cardiovascular events, but the key mechanisms remain elusive. The objective of this study was to uncover the potential link between pathogenic accumulation of salicylic acid (SA), the major metabolite of aspirin, and HAPR in diabetic state. Aspirin failed to inhibit platelet CD62P expression and thromboxane (TX) B2/6-keto-prostaglandin(PG)F1α ratio in a type 2 diabetes mellitus (T2DM) mice model, particularly in the female, which were unanimously accompanied by significantly higher plasma SA concentrations. Pre-administration with SA increased both platelet CD62P expression and TXB2/6-keto-PGF1α ratio in female T2DM mice, while pretreatment with NaHCO3 caused the opposite effect. On the in vitro human umbilical vein endothelial cells (HUVECs)-platelet interaction assay, SA suppressed inflammation-induced cyclooxygenase-2 upregulation on HUVECs and attenuated their inhibitory effect on platelet aggregation in a dose-dependent manner. The prolonged retention of SA in diabetes may be partially explained by the downregulation of various SA efflux transporters in the kidney and the decreased urine pH. Importantly, in female aspirin non-responsive patients, the trough plasma concentration of SA are markedly increased with T2DM treated with long-term aspirin, and TXB2/6-keto-PGF1α ratio and uric acid level in plasma are positively correlated with SA concentration. Our findings support that the accumulation of SA represents an important factor in causing HAPR in diabetes, and that targeting impaired SA excretion may become a novel intervention strategy to diabetes-associated HAPR.

  12. γ-aminobutyric acid type A α4, β2, and δ subunits assemble to produce more than one functionally distinct receptor type.

    PubMed

    Eaton, Megan M; Bracamontes, John; Shu, Hong-Jin; Li, Ping; Mennerick, Steven; Steinbach, Joe Henry; Akk, Gustav

    2014-12-01

    Native γ-aminobutyric acid (GABA)A receptors consisting of α4, β1-3, and δ subunits mediate responses to the low, tonic concentration of GABA present in the extracellular milieu. Previous studies on heterologously expressed α4βδ receptors have shown a large degree of variability in functional properties, including sensitivity to the transmitter. We studied properties of α4β2δ receptors employing free subunits and concatemeric constructs, expressed in Xenopus oocytes, HEK 293 cells, and cultured hippocampal neurons. The expression system had a strong effect on the properties of receptors containing free subunits. The midpoint of GABA activation curve was 10 nM for receptors in oocytes versus 2300 nM in HEK cells. Receptors activated by the steroid alfaxalone had an estimated maximal open probability of 0.6 in oocytes and 0.01 in HEK cells. Irrespective of the expression system, receptors resulting from combining the tandem construct β2-δ and a free α4 subunit exhibited large steroid responses. We propose that free α4, β2, and δ subunits assemble in different configurations with distinct properties in oocytes and HEK cells, and that subunit linkage can overcome the expression system-dependent preferential assembly of free subunits. Hippocampal neurons transfected with α4 and the picrotoxin-resistant δ(T269Y) subunit showed large responses to alfaxalone in the presence of picrotoxin, suggesting that α4βδ receptors may assemble in a similar configuration in neurons and oocytes.

  13. Comparison of the action of baclofen with gamma-aminobutyric acid on rat hippocampal pyramidal cells in vitro.

    PubMed Central

    Newberry, N R; Nicoll, R A

    1985-01-01

    Intracellular recordings from CA1 pyramidal cells in the hippocampal slice preparation were used to compare the action of baclofen, a gamma-aminobutyric acid (GABA) analogue, with GABA. Ionophoretic application of GABA or baclofen into stratum (s.) pyramidale evoked hyperpolarizations associated with reductions in the input resistance of the cell. Baclofen responses were easier to elicit in the dendrites than in the cell body layer. Blockade of synaptic transmission, with tetrodotoxin or cadmium, did not reduce baclofen responses, indicating a direct post-synaptic action. (+)-Bicuculline (10 microM) and bicuculline methiodide (100 microM) had little effect on baclofen responses but strongly antagonized somatic GABA responses of equal amplitude. The bicuculline resistance of the baclofen response was not absolute, as higher concentrations of these compounds did reduce it. Pentobarbitone (100 microM) enhanced somatic GABA responses without affecting baclofen responses. (-)-Baclofen was approximately 200 times more potent than (+)-baclofen. The reversal potentials for the somatic GABA and baclofen responses were -70 mV and -85 mV respectively. When the membrane was depolarized, the baclofen response was reduced. This apparent voltage sensitivity was not seen with somatic GABA responses. Altering the chloride gradient across the cell membrane altered the reversal potential of the somatic GABA response but not that of the baclofen response. It was extrapolated that a tenfold shift in the extracellular potassium concentration would cause a 48 mV shift in the reversal potential of the baclofen response. Barium ions reduced the baclofen response, but not the GABA response. Orthodromic stimulation produced a fast inhibitory post-synaptic potential (i.p.s.p.) and a slow i.p.s.p. The properties of the fast and slow i.p.s.p.s were remarkably similar to those of the somatic GABA and baclofen responses, respectively. Application of GABA to the pyramidal cell dendrites evoked, in

  14. Taurine-induced attenuation of MPP+ neurotoxicity in vitro: a possible role for the GABA(A) subclass of GABA receptors.

    PubMed

    O'Byrne, M B; Tipton, K F

    2000-05-01

    Taurine is a sulphur-containing beta-amino acid found in high (millimolar) concentrations in excitable tissues such as brain and heart. Its suggested roles include osmoregulator, thermoregulator, neuromodulator, and potential neurotransmitter. This amino acid has also been shown to be released in large concentrations during ischaemia and excitotoxin-induced neuronal damage. Here we report a protective effect of taurine against MPP(+)-induced neurotoxicity in coronal slices from rat brain. Significant protective effects were observed at taurine concentrations of 20 and 1 mM, suggesting a potential role for taurine in cases of neuronal insult. Studies with the synthetic taurine analogues taurine phosphonate, guanidinoethane sulphonate, and trimethyltaurine suggested the observed effect to be mediated via an extracellular mechanism. The use of GABA receptor ligands muscimol and bicuculline indicated the effect to be mediated through activation of GABA(A) receptors.

  15. Effects of Blocking GABA Degradation on Corticotropin-Releasing Hormone Gene Expression in Selected Brain Regions

    PubMed Central

    Tran, Viet; Hatalski, Carolyn G.; Yan, Xiao-Xin; Baram, Tallie Z.

    2011-01-01

    Summary Purpose The γ-aminobutyric acid (GABA) degradation blocker γ-vinyl-GABA (VGB) is used clinically to treat seizures in both adult and immature individuals. The mechanism by which VGB controls developmental seizures is not fully understood. Specifically, whether the anticonvulsant properties of VGB arise only from its elevation of brain GABA levels and the resulting activation of GABA receptors, or also from associated mechanisms, remains unresolved. Corticotropin-releasing hormone (CRH), a neuropeptide present in many brain regions involved in developmental seizures, is a known convulsant in the immature brain and has been implicated in some developmental seizures. In certain brain regions, it has been suggested that CRH synthesis and release may be regulated by GABA. Therefore we tested the hypothesis that VGB decreases CRH gene expression in the immature rat brain, consistent with the notion that VGB may decrease seizures also by reducing the levels of the convulsant molecule, CRH. Methods VGB was administered to immature, 9-day-old rats in clinically relevant doses, whereas littermate controls received vehicle. Results In situ hybridization histochemistry demonstrated a downregulation of CRH mRNA levels in the hypothalamic paraventricular nucleus but not in other limbic regions of VGB-treated pups compared with controls. In addition, VGB-treated pups had increased CRH peptide levels in the anterior hypothalamus, as shown by radioimmunoassay. Conclusions These findings are consistent with a reduction of both CRH gene expression and secretion in the hypothalamus, but do not support an indirect anticonvulsant mechanism of VGB via downregulation of CRH levels in limbic structures. However, the data support a region-specific regulation of CRH gene expression by GABA. PMID:10487181

  16. Decreased auditory GABA+ concentrations in presbycusis demonstrated by edited magnetic resonance spectroscopy.

    PubMed

    Gao, Fei; Wang, Guangbin; Ma, Wen; Ren, Fuxin; Li, Muwei; Dong, Yuling; Liu, Cheng; Liu, Bo; Bai, Xue; Zhao, Bin; Edden, Richard A E

    2015-02-01

    Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the central auditory system. Altered GABAergic neurotransmission has been found in both the inferior colliculus and the auditory cortex in animal models of presbycusis. Edited magnetic resonance spectroscopy (MRS), using the MEGA-PRESS sequence, is the most widely used technique for detecting GABA in the human brain. However, to date there has been a paucity of studies exploring changes to the GABA concentrations in the auditory region of patients with presbycusis. In this study, sixteen patients with presbycusis (5 males/11 females, mean age 63.1 ± 2.6 years) and twenty healthy controls (6 males/14 females, mean age 62.5 ± 2.3 years) underwent audiological and MRS examinations. Pure tone audiometry from 0.125 to 8 kHz and tympanometry were used to assess the hearing abilities of all subjects. The pure tone average (PTA; the average of hearing thresholds at 0.5, 1, 2 and 4 kHz) was calculated. The MEGA-PRESS sequence was used to measure GABA+ concentrations in 4 × 3 × 3 cm(3) volumes centered on the left and right Heschl's gyri. GABA+ concentrations were significantly lower in the presbycusis group compared to the control group (left auditory regions: p = 0.002, right auditory regions: p = 0.008). Significant negative correlations were observed between PTA and GABA+ concentrations in the presbycusis group (r = -0.57, p = 0.02), while a similar trend was found in the control group (r = -0.40, p = 0.08). These results are consistent with a hypothesis of dysfunctional GABAergic neurotransmission in the central auditory system in presbycusis and suggest a potential treatment target for presbycusis.

  17. Locally infused taurine, GABA and homotaurine alter differently the striatal extracellular concentrations of dopamine and its metabolites in rats.

    PubMed

    Ruotsalainen, M; Majasaari, M; Salimäki, J; Ahtee, L

    1998-01-01

    We studied in vivo the effects of locally infused taurine (50, 150, and 450 mM) on the striatal dopamine and its metabolites in comparison with those of GABA and homotaurine, a GABAA receptor agonist, in freely moving rats. The extracellular dopamine concentration was elevated maximally 2.5-, 2- and 4-fold by taurine, GABA and homotaurine, respectively. At 150 mM concentration, at which the maximum effects occurred, homotaurine increased the extracellular dopamine more than taurine or GABA. When taurine and GABA were infused simultaneously with tetrodotoxin the output of dopamine did not differ from that in the presence of tetrodotoxin alone. In comparison, tetrodotoxin did not inhibit the increase in extracellular dopamine caused by homotaurine. Furthermore, omission of calcium from the perfusion fluid inhibited the increase of extracellular dopamine caused by GABA. However, it did not block the increase of dopamine caused by taurine or homotaurine. The present study suggests that the effects of intrastriatal taurine, GABA and homotaurine on the striatal extracellular dopamine differ. Thus, these amino acids seem to affect the striatal dopaminergic neurons via more than one mechanism.

  18. Decreased GABA receptor in the cerebral cortex of epileptic rats: effect of Bacopa monnieri and Bacoside-A

    PubMed Central

    2012-01-01

    Abstact Background Gamma amino butyric acid (GABA), the principal inhibitory neurotransmitter in the cerebral cortex, maintains the inhibitory tones that counter balances neuronal excitation. When this balance is perturbed, seizures may ensue. Methods In the present study, alterations of the general GABA, GABAA and GABAB receptors in the cerebral cortex of the epileptic rat and the therapeutic application of Bacopa monnieri were investigated. Results Scatchard analysis of [3H]GABA, [3H]bicuculline and [3H]baclofen in the cerebral cortex of the epileptic rat showed significant decrease in Bmax (P < 0.001) compared to control. Real Time PCR amplification of GABA receptor subunits such as GABAAά1, GABAAγ, GABAAδ, GABAB and GAD where down regulated (P < 0.001) in epileptic rats. GABAAά5 subunit and Cyclic AMP responsible element binding protein were up regulated. Confocal imaging study confirmed the decreased GABA receptors in epileptic rats. Epileptic rats have deficit in radial arm and Y maze performance. Conclusions Bacopa monnieri and Bacoside-A treatment reverses epilepsy associated changes to near control suggesting that decreased GABA receptors in the cerebral cortex have an important role in epileptic occurrence; Bacopa monnieri and Bacoside-A have therapeutic application in epilepsy management. PMID:22364254

  19. Frontal GABA levels change during working memory.

    PubMed

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

    2012-01-01

    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 hemody