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![Model for dual role of the GABA transporter. Under normal conditions ( A ) the GABA transporter works in the forward direction to clear the extracellular space of GABA. During high frequency firing and seizures ( B ) [K ϩ ] o and [Na ϩ ] i both rise, and the cells depolarize. This would induce a reversal of the GABA transporter, maintaining GABAer- gic inhibition at a time that vesicular release decreases. The source of GABA release (neurons or glia) is not known at present.](profile/Yuanming-Wu/publication/12027169/figure/fig4/AS:282284184883230@1444313202941/Model-for-dual-role-of-the-GABA-transporter-Under-normal-conditions-A-the-GABA.png)
Model for dual role of the GABA transporter. Under normal conditions ( A ) the GABA transporter works in the forward direction to clear the extracellular space of GABA. During high frequency firing and seizures ( B ) [K ϩ ] o and [Na ϩ ] i both rise, and the cells depolarize. This would induce a reversal of the GABA transporter, maintaining GABAer- gic inhibition at a time that vesicular release decreases. The source of GABA release (neurons or glia) is not known at present.
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The GABA transporter can reverse with depolarization, causing nonvesicular GABA release. However, this is thought to occur only under pathological conditions. Patch-clamp recordings were made from rat hippocampal neurons in primary cell cultures. Inhibition of GABA transaminase with the anticonvulsant gamma-vinyl GABA (vigabatrin; 0.05-100 microm)...
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... to 6 m M , or an increase in the cytosolic [GABA], was enough to alter the equilibrium so that GABA efflux oc- curred. It will be important to explain these observations in terms of the molecular mechanisms of transporter function. The tradi- tional view of the GABA transporter is that it is electrogenic, with a fixed stoichiometry of two sodium ions and one chloride ion transported per GABA molecule (Larsson et al., 1980; Guastella et al., 1990; Borden et al., 1992; Kavanaugh et al., 1992; Mager et al., 1993). However, measurements of current flow through arti- ficially expressed GAT-1 suggest that the stoichiometry actually is not fixed. For example, Na ϩ or Cl Ϫ can be transported alone in the absence of GABA (Cammack et al., 1994). Because “uncou- pled” Na ϩ flux can occur without GABA flux, it is possible that uncoupled GABA flux also could occur in the absence of Na ϩ or Cl Ϫ flux. Because GABA is uncharged, uncoupled GABA flux would not be detected by recordings of transporter current. This could explain how the direction of GABA transport could be so sensitive to cytosolic [GABA]. As cytosolic [GABA] increases sufficiently high, there may be significant “slippage” of the trans- porter, with uncoupled GABA efflux occurring without NaCl efflux. However, an alternative possibility is that GABA flux is coupled with Na ϩ and Cl Ϫ under physiological conditions but that Na ϩ is driven against its gradient when GABA efflux is induced by an increase in cytosolic [GABA]. Rather than simply acting as a sponge for reuptake of GABA after vesicular release, the GABA transporter apparently main- tains an equilibrium between intracellular and extracellular neu- rotransmitter levels. The setpoint for this equilibrium depends on membrane potential and on the GABA, sodium, and chloride concentration gradients. The large increase in extracellular [GABA] after the fusion of synaptic vesicles would be expected to drive reuptake, but when extracellular [GABA] is low, nonvesicu- lar GABA efflux commonly may occur at relatively low firing rates. Previous studies also have suggested that nonvesicular GABA efflux can be functionally important under some condi- tions (Schwartz, 1987; Taylor and Gordon-Weeks, 1991; During et al., 1995; Drew et al., 1997). Reversal is not unique to the GABA transporter (Nicholls and Attwell, 1990; Levi and Raiteri, 1993), but it is possible that the threshold for reversal of the GABA transporter is lower than for other transporters (Attwell et al., 1993). A low threshold for reversal may be related to the inhibitory role of the GABAergic system. As neuronal activity increases, nonvesicular GABA re- lease would help to brake excessive excitation. This negative feedback would be resistant to energy deprivation, because a decrease in ATP stores would enhance nonvesicular release by depolarizing cells and increasing [Na ϩ ] . In contrast, if the glu- tamate transporter had such a low threshold for reversal, it might induce excitotoxicity under normal conditions (Nicholls and At- twell, 1990). The results presented here suggest that an increase in nonvesicu- lar GABA release contributes to the anticonvulsant effect of vigabatrin. After an intraperitoneal injection of vigabatrin in vivo , the GABA pool associated with nerve terminals does not peak until 60 hr (Gale and Iadarola, 1980). It is the level of GABA in this nerve terminal pool that correlates with anticonvulsant ac- tivity and not total GABA, which peaks in Ͻ 36 hr (Gale and Iadarola, 1980). The slow increase in nonvesicular GABA efflux observed here in cultured cells mimics the time course of the anticonvulsant effect in vivo , suggesting that enhancement of nonvesicular GABA release contributes to the anticonvulsant effect. Because the bath solution did not contain vigabatrin at the time the recordings were made, the nonvesicular GABA release induced by vigabatrin was not a result of direct, reversible GABAergic actions of the drug (Jolkkonen et al., 1992; Jung and Palfreyman, 1995; Jackson et al., 2000). Low concentrations of vigabatrin induced spontaneous nonve- sicular GABA release and tonic inhibition of neighboring neu- rons, which might be assumed to be detrimental to brain function. However, tonic vesicular release of GABA occurs under physio- logical conditions in untreated tissue and has been proposed to be important for the regulation of neuronal excitability (Otis et al., 1991). Thus, tonic nonvesicular GABA release induced by ther- apeutic levels of vigabatrin simply may contribute to this back- ground inhibitory tone and help to regulate neuronal firing. Higher doses of vigabatrin could result in excessive tonic inhibi- tion or alternatively could result in desensitization of a population of GABA A receptors, leading to a decrease in inhibition. When neuronal firing rates become excessive, vesicular GABA release decreases because of the depletion of energy stores and limitation of the maximum rate of recycling of vesicles (Fig. 10). Under these same conditions, nonvesicular GABA release would be stimulated. Vigabatrin thus would enhance a form of GABA release that is most important at high firing rates. This activity- dependent mechanism would explain why vigabatrin prevents seizures with relatively little effect on normal cognition. A low incidence of cognitive side effects is a property shared with the anticonvulsant gabapentin, which shares the final common path- way of enhancement of nonvesicular GABA release (Kocsis and Honmou, 1994; Honmou et al., 1995; Taylor et al., 1998; Rho and Sankar, 1999). Factors other than depolarization and cytosolic [GABA] can alter the function of the GABA transporter and thus may reduce or enhance its role during seizures. Dynamic insertion of GABA transporters into the plasma membrane has been demonstrated to occur in response to an increase in extracellular [GABA] (Bern- stein and Quick, 1999). An increased number of GABA trans- porters in the plasma membrane would increase the flux of GABA under the force of a constant [GABA] gradient. Con- versely, within the seizure focus of human temporal lobe epilepsy patients there is evidence for a decrease in the number of func- tional GABA transporters (During et al., 1995), which could contribute to seizure generation or spread. It is likely that a variety of other factors could modulate GABA transporter num- ber or alter the function of those transporters that are present. We propose that nonvesicular GABA release is an important form of inhibition that complements vesicular GABA release. A variety of pathological processes, physiological modulators, and pharmacological agents may alter the balance between GABA reuptake and carrier-mediated GABA release and thus influence neuronal excitability and seizure ...
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... Reports indicate that the degradation of intracellular GABA by GABA-T or SSADH reduces tonic inhibition in the brain. Vigabatrin, a GABA-T inhibitor, blocks GABA degradation and increases GABA tone 93,94 . Similarly, genetic knockout of Ssadh (also known as Aldh5a1) results in increased tonic inhibition in the cortex 95 and thalamic ventrobasal nucleus 96 . ...
γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter released at GABAergic synapses, mediating fast-acting phasic inhibition. Emerging lines of evidence unequivocally indicate that a small amount of extracellular GABA — GABA tone — exists in the brain and induces a tonic GABA current that controls neuronal activity on a slow timescale relative to that of phasic inhibition. Surprisingly, studies indicate that glial cells that synthesize GABA, such as astrocytes, release GABA through non-vesicular mechanisms, such as channel-mediated release, and thereby act as the source of GABA tone in the brain. In this Review, we first provide an overview of major advances in our understanding of the cell-specific molecular and cellular mechanisms of GABA synthesis, release and clearance that regulate GABA tone in various brain regions. We next examine the diverse ways in which the tonic GABA current regulates synaptic transmission and synaptic plasticity through extrasynaptic GABAA-receptor-mediated mechanisms. Last, we discuss the physiological mechanisms through which tonic inhibition modulates cognitive function on a slow timescale. In this Review, we emphasize that the cognitive functions of tonic GABA current extend beyond mere inhibition, laying a foundation for future research on the physiological and pathophysiological roles of GABA tone regulation in normal and abnormal psychiatric conditions.
... For GAT1, a number of interesting results have been described. The reported ratio between the forward and the reverse transport mode is tuned by membrane potential, if no specific conditions are applied to intra-and extra-cellular substrates concentrations: at negative potentials, forward transport is favored, while the equilibrium is shifted towards reverse transport with membrane depolarization (Wu et al., 2001). This observation has biological relevance as the membrane potential reaches a positive value when the neuron is firing at an action potential. ...
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system (CNS). Its homeostasis is maintained by neuronal and glial GABA transporters (GATs). The four GATs identified in humans are GAT1 (SLC6A1), GAT2 (SLC6A13), GAT3 (SLC6A11), and betaine/GABA transporter-1 BGT-1 (SLC6A12) which are all members of the solute carrier 6 (SLC6) family of sodium-dependent transporters. While GAT1 has been investigated extensively, the other GABA transporters are less studied and their role in CNS is not clearly defined. Altered GABAergic neurotransmission is involved in different diseases, but the importance of the different transporters remained understudied and limits drug targeting. In this review, the well-studied GABA transporter GAT1 is compared with the less-studied BGT-1 with the aim to leverage the knowledge on GAT1 to shed new light on the open questions concerning BGT-1. The most recent knowledge on transporter structure, functions, expression, and localization is discussed along with their specific role as drug targets for neurological and neurodegenerative disorders. We review and discuss data on the binding sites for Na ⁺ , Cl ⁻ , substrates, and inhibitors by building on the recent cryo-EM structure of GAT1 to highlight specific molecular determinants of transporter functions. The role of the two proteins in GABA homeostasis is investigated by looking at the transport coupling mechanism, as well as structural and kinetic transport models. Furthermore, we review information on selective inhibitors together with the pharmacophore hypothesis of transporter substrates.
... To manipulate pruning in this area, we first examined a potential mechanism, an atypical GABA A receptor (GABAR), α4βδ 24 , which expresses on dendritic spines at puberty as well as along the dendritic shaft and on the soma in some CNS regions to inhibit synaptic input. In contrast to typical GABARs, which express post-synaptically to GABAergic interneurons, α4βδ GABARs express away from GABAergic synapse, have a high sensitivity to ambient GABA, which is maintained by GABA transporters 25 , and display little desensitization 26 . ...
Anxiety is increasingly reported, especially in adolescent females. The etiology is largely unknown, which limits effective treatment. Layer 5 prelimbic cortex (L5PL) increases anxiety responses but undergoes adolescent synaptic pruning, raising the question of the impact of pruning on anxiety. Here we show that preventing L5PL pruning increases anxiety in response to an aversive event in adolescent and adult female mice. Spine density of Golgi-stained neurons decreased ~ 63% from puberty (~ PND35, vaginal opening) to post-puberty (PND56, P < 0.0001). Expression of α4βδ GABA A receptors (GABARs) transiently increased tenfold in L5PL at puberty (P < 0.00001), but decreased post-pubertally. Both global and local knockdown of these receptors during puberty prevented pruning, increasing spine density post-pubertally (P < 0.0001), an effect reversed by blocking NMDA receptors (NMDARs). Pubertal expression of the NMDAR-dependent spine protein kalirin7 decreased (50%, P < 0.0001), an effect prevented by α4 knock-out, suggesting that α4βδ-induced reductions in kalirin7 underlie pruning. Increased spine density due to local α4 knockdown at puberty decreased open arm time on the elevated plus maze post-pubertally (62%, P < 0.0001) in response to an aversive stimulus, suggesting that increases in L5PL synapses increase anxiety responses. These findings suggest that prelimbic synaptic pruning is necessary to limit anxiety in adulthood and may suggest novel therapies.
... Under baseline conditions, GATs operate near equilibrium [43]. Therefore, upon moderate depolarization evoked by a short series of action potentials, transporter reversal occurs [45,46]. However, during excessive network activity and enhanced synaptic GABA release, elevated levels of extracellular GABA favor GABA uptake by GATs [47]. ...
GABA is the main inhibitory neurotransmitter in the CNS acting at two distinct types of receptor: ligand-gated ionotropic GABA A receptors and G protein-coupled metabotropic GABA B receptors, thus mediating fast and slow inhibition of excitability at central synapses. GABAergic signal transmission has been intensively studied in neurons in contrast to oligodendrocytes and their precursors (OPCs), although the latter express both types of GABA receptor. Recent studies focusing on interneuron myelination and interneuron-OPC synapses have shed light on the importance of GABA signaling in the oligodendrocyte lineage. In this review, we start with a short summary on GABA itself and neuronal GABAergic signaling. Then, we elaborate on the physiological role of GABA receptors within the oligodendrocyte lineage and conclude with a description of these receptors as putative targets in treatments of CNS diseases.
... Four GABA transporter types (GAT1-3 and BGT1), all showing potassium-and voltage-dependent kinetics, are expressed in both neurons and glial cells [44][45][46] . Intense excitatory activity, for instance during epileptiform bursts, can increase extracellular [K + ] to 12-15 mM 47,48 and could, in principle, reverse GABA transport, thus generating GABA efflux 49 . As this type of condition is compatible with the present experimental settings, GABA transporters could potentially be a source of extracellular GABA coming from both neurons and glia. ...
The cellular and circuit mechanisms that trigger and maintain epileptiform discharges remain the subject of intense debate. We have earlier reported a bell-shape dependence of spiking activity of interneuronal populations on tonic GABAA receptor conductance (Gtonic), suggesting an innate mechanism to enable slow self-sustained network oscillations. In the brain, Gtonic is controlled by the slow changes of the extracellular GABA concentration ([GABA]e), which in turn depends on spiking activity of interneurons. Here, we employ outside-out patch-clamp recordings of GABAA receptor and fluorescence imaging of a GABA sensor to show that periodic epileptiform discharges are preceded by [GABA]e rises. Computer simulations of spiking interneuronal networks reveal that incorporating extrasynaptic waves of [GABA]e readily enables periodic occurrences of synchronised interneuronal spiking, which are in phase with rises in Gtonic and can trigger short bursts of principal cell spiking. Simultaneous recording from multiple neurons and selective optogenetic stimulation of parvalbumin-positive (PV+) interneurons confirmed the modelling predictions, consistent with a causal relationship between synchronisation of interneuronal activity, inhibitory synaptic input, Gtonic, and interictal events. Our findings suggest a key role of [GABA]e dynamics in enabling and pacing regenerative rhythmic activity of brain networks.
... 85 GAT1 reversal is observed in response to membrane depolarization in hippocampal cultures. 86 Interestingly, an increase in GAT1 immunoreactivity has been observed in the hippocampus of rats following 4-AP and kainic acid-induced epileptiform activity 87,88 and recent studies show that the antiseizure medications gabapentin and vigabatrin enhance GAT1-mediated GABA release, 86,89 with vigabatrin potently increasing ambient [GABA] e and inducing tonic inhibition of neurons. 90 Additionally, tiagabine, a selective GAT1 inhibitor-commonly prescribed as an add-on therapeutic option for epileptics with complex partial seizures 91 -has been demonstrated to elevate the pentylenetetrazole (PTZ)evoked seizure threshold and reduce generalized seizures in amygdala kindled rats. ...
... 85 GAT1 reversal is observed in response to membrane depolarization in hippocampal cultures. 86 Interestingly, an increase in GAT1 immunoreactivity has been observed in the hippocampus of rats following 4-AP and kainic acid-induced epileptiform activity 87,88 and recent studies show that the antiseizure medications gabapentin and vigabatrin enhance GAT1-mediated GABA release, 86,89 with vigabatrin potently increasing ambient [GABA] e and inducing tonic inhibition of neurons. 90 Additionally, tiagabine, a selective GAT1 inhibitor-commonly prescribed as an add-on therapeutic option for epileptics with complex partial seizures 91 -has been demonstrated to elevate the pentylenetetrazole (PTZ)evoked seizure threshold and reduce generalized seizures in amygdala kindled rats. ...
An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance-as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer's disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)-leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.
... EKP was synthesized and gifted to us from Dr Peter A. M. de Witte and his laboratory (KU Leuven, Leuven, Belgium). Vigabatrin (vinyl-γ-aminobutyric acid) (V8261, Sigma-Aldrich, St Louis, MO, USA) is a selective, irreversible inhibitor of GABA transaminase (GABA-T; ABAT), the major enzyme that synthesizes the first step in the metabolic degradation of GABA (Ben-Menachem, 2011;Qume and Fowler, 1997;Sloley et al., 1994;Wu et al., 2001). N,N-diethylaminobenzaldehyde (DEAB) (D86256, Sigma-Aldrich) is a selective inhibitor of aldehyde dehydrogenase isoenzymes (Koppaka et al., 2012;Morgan et al., 2015). ...
In most vertebrates, a lack of oxygen quickly leads to irreparable damages to vital organs, such as the brain and heart. However, there are some vertebrates that have evolved mechanisms to survive periods of no oxygen (anoxia). The annual killifish ( Austrofundulus limnaeus ) survives in ephemeral ponds in the coastal deserts of Venezuela and their embryos have the remarkable ability to tolerate anoxia for months. When exposed to anoxia, embryos of A. limnaeus respond by producing significant amounts of γ-aminobutyric acid (GABA). This study aims to understand the role of GABA in supporting the metabolic response to anoxia. To explore this, we investigated four developmentally distinct stages of A. limnaeus embryos that vary in their anoxia tolerance. We measured GABA and lactate concentrations across development in response to anoxia and aerobic recovery. We then inhibited enzymes responsible for the production and degradation of GABA and observed GABA and lactate concentrations, as well as embryo mortality. Here, we show for the first time that GABA metabolism affects anoxia tolerance in A. limnaeus embryos. Inhibition of enzymes responsible for GABA production (glutamate decarboxylase) and degradation (GABA-transaminase and succinic acid semialdehyde dehydrogenase) led to decreased mortality, supporting a role for GABA as an intermediate product and not a metabolic end product. We propose multiple roles for GABA during anoxia and aerobic recovery in A. limnaeus embryos, serving as a neurotransmitter, an energy source, and an antioxidant.
... Long range excitatory and inhibitory interactions between functionally connected brain regions are well established (91)(92)(93). The strong coupling between glutamatergic neurotransmission and total GABA level is supported by a large body of in vitro and in vivo evidence [e.g., (16,75,(94)(95)(96)(97)(98)(99)(100)]. A large number of neuroimaging studies have also shown that total glutamate or Glx concentration is significantly correlated with neural activity or glutamatergic neurotransmission [e.g., (28,(101)(102)(103)]. Correlations of total glutamate and total GABA levels locally and among regions functionally connected in a specific neural network have also been reported [e.g., (15)(16)(17)19)]. ...
Magnetic resonance spectroscopy (MRS) studies have found significant correlations among neurometabolites (e.g., between glutamate and GABA) across individual subjects and altered correlations in neuropsychiatric disorders. In this article, we discuss neurochemical associations among several major neurometabolites which underpin these observations by MRS. We also illustrate the role of spectral editing in eliminating unwanted correlations caused by spectral overlapping. Finally, we describe the prospects of mapping macroscopic neurochemical associations across the brain and characterizing excitation–inhibition balance of neural networks using glutamate- and GABA-editing MRS imaging.
... Vigabatrin is an irreversible GABA transaminase inhibitor used as adjunctive therapy for focal seizures and monotherapy for infantile spasms. It is thought to alleviate seizures by increasing tonic, or persistent, GABAergic inhibitory currents (Wu et al., 2001(Wu et al., , 2003. Therefore, it may be anticipated that vigabatrin would be useful in patients with GABRB3 variants that have a reduction in the number or a functional impairment of b3-containing GABA A receptors. ...
... Vigabatrin is an irreversible inhibitor of GABA transaminase that blocks intracellular GABA degradation at the presynaptic terminal. The increased intracellular GABA concentrations reverse the direction of GABA transport, leading to non-vesicular release of GABA into the extracellular space (Wu et al., 2001(Wu et al., , 2003 (Fig. 6E). In hippocampal cultures, 4 days of vigabatrin exposure To measure the rate of desensitization, the recording apparatus was configured to remove dead volume and GABA was applied for 120 s, and the deactivation rates in the presence of GABA were fitted to an exponential decay function, with the deactivation constant determined for different GABA concentrations against WT and double mutant receptors. ...
Variants in the GABRB3 gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with GABRB3 variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A GABRB3 variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of de novo variants in GABRB3 (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the GABRB3 p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the GABRB3 variant. The mRNA of these constructs was injected into Xenopus oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the GABRB3 p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of GABRB3 variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function GABRB3 variants.
... γ-aminobutyric acid transaminase (GABA-T) is formed by the Abat gene, which can decompose GABA into glutamic acid and succinic semialdehyde, and then convert it into succinic acid to enter the tricarboxylic acid cycle for metabolism [20]. The anticonvulsant γ-vinyl GABA (vigabatrin) is an irreversible antagonist of GABA-T that induces an increase in GABA levels in rat, mice and human brains [21][22][23][24]. These results all indicate that GABA-T functions directly in GABA metabolism in the central nervous system. ...
This study explored the role of γ-aminobutyric acid transaminase (GABA-T) in the puberty and reproductive performance of female rats. Immunofluorescence technique, quantitative real-time PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect the distribution of GABA-T and the expression of genes and hormones in female rats, respectively. The results showed that GABA-T was mainly distributed in the arcuate nucleus (ARC), paraventricular nucleus (PVN) and periventricular nucleus (PeN) of the hypothalamus, and in the adenohypophysis, ovarian granulosa cells and oocytes. Abat mRNA level at 28 d was lowest in the hypothalamus and the pituitary; at puberty, it was lowest in the ovary. Abat mRNA level was highest in adults in the hypothalamus; at infancy and puberty, it was highest in the pituitary; and at 21 d it was highest in the ovary. After vigabatrin (GABA-T irreversible inhibitor) was added to hypothalamus cells, the levels of Abat mRNA and Rfrp-3 mRNA were significantly reduced, but Gnrh mRNA increased at the dose of 25 and 50 μg/mL; Kiss1 mRNA was significantly increased but Gabbr1 mRNA was reduced at the 50 μg/mL dose. In prepubertal rats injected with vigabatrin, puberty onset was delayed. Abat mRNA, Kiss1 mRNA and Gnrh mRNA levels were significantly reduced, but Rfrp-3 mRNA level increased in the hypothalamus. Vigabatrin reduced the concentrations of GABA-T, luteinizing hormone (LH) and progesterone (P4), and the ovarian index. Lactation performance was reduced in adult rats with vigabatrin treatment. Four hours after vigabatrin injection, the concentrations of GABA-T and LH were significantly reduced in adult and 25 d rats, but follicle-stimulating hormone (FSH) increased in 25 d rats. In conclusion, GABA-T affects the reproductive function of female rats by regulating the levels of Gnrh, Kiss1 and Rfrp-3 in the hypothalamus as well as the concentrations of LH and P4.
