GABA Transporter-1 (GAT1)-Deficient Mice: Differential Tonic Activation of GABAA Versus GABAB Receptors in the Hippocampus

After its release from interneurons in the CNS, the major inhibitory neurotransmitter GABA is taken up by GABA transporters (GATs). The predominant neuronal GABA transporter GAT1 is localized in GABAergic axons and nerve terminals, where it is thought to influence GABAergic synaptic transmission, but the details of this regulation are unclear. To address this issue, we have generated a strain of GAT1-deficient mice. We observed a large increase in a tonic postsynaptic hippocampal GABAA receptor-mediated conductance. There was little or no change in the waveform or amplitude of spontaneous inhibitory postsynaptic currents (IPSCs) or miniature IPSCs. In contrast, the frequency of quantal GABA release was one-third of wild type (WT), although the densities of GABAA receptors, GABAB receptors, glutamic acid decarboxylase 65 kDa, and vesicular GAT were unaltered. The GAT1-deficient mice lacked a presynaptic GABAB receptor tone, present in WT mice, which reduces the frequency of spontaneous IPSCs. We conclude that GAT1 deficiency leads to enhanced extracellular GABA levels resulting in an overactivation of GABAA receptors responsible for a postsynaptic tonic conductance. Chronically elevated GABA levels also downregulate phasic GABA release and reduce presynaptic signaling via GABAB receptors thus causing an enhanced tonic and a diminished phasic inhibition.

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

Journal of Central Nervous System Disease ◽

10.4137/jcnsd.s14012 ◽

2014 ◽

Vol 6 ◽

pp. JCNSD.S14012 ◽

Cited By ~ 10

Author(s):

Seok K. Kang ◽

Shin Tae Kim ◽

Michael V. Johnston ◽

Shilpa D. Kadam

Keyword(s):

Acid Decarboxylase ◽

Gaba Transporter ◽

Motor Disabilities ◽

Gaba Transporters ◽

Age Dependent ◽

Progressive Neurodegeneration ◽

Gabaergic Synapses ◽

Cell Densities ◽

Gaba Transporter 1 ◽

First Time

Rett syndrome (RTT), associated with mutations in methyl-CpG-binding protein 2 (Mecp2), is linked to diverse neurological symptoms such as seizures, motor disabilities, and cognitive impairments. An altered GABAergic system has been proposed as one of many underlying pathologies of progressive neurodegeneration in several RTT studies. This study for the first time investigated the temporal- and location-specific alterations in the expression of γ-amino butyric acid (GABA) transporter 1 (GAT-1), vesicular GABA transporter (vGAT), and glutamic acid decarboxylase 67kD (GAD67) in wild type (WT) and knockout (KO) mice in the Mecp2m1.1Bird/y mouse model of RTT. Immunohistochemistry (IHC) co-labeling of GAT-1 with vGAT identified GABAergic synapses that were quantitated for mid-sagittal sections in the frontal cortex (FC), hippocampal dentate gyrus (DG), and striatum (Str). An age-dependent increase in the expression of synaptic GABA transporters, GAT-1, and vGAT, was observed in the FC and DG in WT brains. Mecp2 KO mice showed a significant alteration in this temporal profile that was location-specific, only in the FC. GAD67-positive cell densities also showed an age-dependent increase in the FC, but a decrease in the DG in WT mice. However, these densities were not significantly altered in the KO mice in the regions examined in this study. Therefore, the significant location-specific downregulation of synaptic GABA transporters in Mecp2 KO brains with unaltered densities of GAD67-positive interneurons may highlight the location-specific synaptic pathophysiology in this model of RTT.

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Submicromolar copper (II) ions stimulate transretinal signaling in the isolated retina from wild type but not from Cav2.3-deficient mice

10.21203/rs.2.16907/v2 ◽

2020 ◽

Author(s):

Toni Schneider ◽

Jan Niklas Lüke ◽

Felix Neumaier ◽

Serdar Alpdogan ◽

Jürgen Hescheler ◽

...

Keyword(s):

Ganglion Cells ◽

Indirect Evidence ◽

Gaba Release ◽

Light Perception ◽

Wild Type ◽

Inhibitory Neurotransmitters ◽

Bovine Retina ◽

Isolated Retina ◽

Deficient Mice ◽

Stimulation Of

Abstract Background : So far, only indirect evidence exists for the pharmacoresistant R-type voltage-gated Ca 2+ channel (VGCC) to be involved in transretinal signaling by triggering GABA-release onto ON-bipolar neurons. This release of inhibitory neurotransmitters was deduced from the sensitivity of the b-wave to stimulation by Ni 2+ , Zn 2+ and Cu 2+ . To further confirm the interpretation of these findings, we compared the effects of Cu 2+ application and chelation (using kainic acid, KA) on the neural retina from wild type and Ca v 2.3-deficient mice. Furthermore, the immediately effect of KA on the ERG b-wave modulation was assessed. Methods : Transretinal signaling was recorded as an ERG from the superfused murine retina isolated from wildtype and Ca v 2.3-deficient mice Results : In mice, the stimulating effect of 100 nM CuCl 2 is absent in the retinae from Ca v 2.3-deficient mice, but prominent in Ca v 2.3-competent mice. Application of up to 3 mM tricine does not affect the murine b-wave in both genotypes, most likely because of chelating amino acids present in the murine nutrient solution. Application of 27 µM KA significantly increased the b-wave amplitude in wild type and Ca v 2.3 (-|-) mice. This effect can most likely be explained by the stimulation of endogenous KA-receptors described in horizontal, OFF-bipolar, amacrine or ganglion cells, which could not be fully blocked in the present study. Conclusion: Cu 2+ dependent modulation of transretinal signaling only occurs in the murine retina from Ca v 2.3 competent mice, supporting the ideas derived from previous work in the bovine retina that R-type Ca 2+ channels are involved in shaping transretinal responses during light perception.

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GABAergic dysfunction in mGlu7 receptor-deficient mice as reflected by decreased levels of glutamic acid decarboxylase 65 and 67kDa and increased reelin proteins in the hippocampus

Brain Research ◽

10.1016/j.brainres.2010.03.078 ◽

2010 ◽

Vol 1334 ◽

pp. 12-24 ◽

Cited By ~ 13

Author(s):

Joanna M. Wierońska ◽

P. Brański ◽

A. Siwek ◽

M. Dybala ◽

G. Nowak ◽

...

Keyword(s):

Glutamic Acid ◽

Glutamic Acid Decarboxylase ◽

Acid Decarboxylase ◽

Glutamic Acid Decarboxylase 65 ◽

Deficient Mice

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Submicromolar copper (II) ions stimulate transretinal signaling in the isolated retina from wild type but not fromCav2.3-deficient mice

10.21203/rs.2.16907/v3 ◽

2020 ◽

Author(s):

Jan Niklas Lüke ◽

Felix Neumaier ◽

Serdar Alpdogan ◽

Jürgen Hescheler ◽

Toni Schneider ◽

...

Keyword(s):

Ganglion Cells ◽

Indirect Evidence ◽

Gaba Release ◽

Light Perception ◽

Wild Type ◽

Inhibitory Neurotransmitters ◽

Bovine Retina ◽

Isolated Retina ◽

Deficient Mice ◽

Stimulation Of

Abstract Background: So far, only indirect evidence exists for the pharmacoresistant R-type voltage-gated Ca2+ channel (VGCC) to be involved in transretinal signaling by triggering GABA-release onto ON-bipolar neurons. This release of inhibitory neurotransmitters was deduced from the sensitivity of the b-wave to stimulation by Ni2+, Zn2+ and Cu2+. To further confirm the interpretation of these findings, we compared the effects of Cu2+ application and chelation (using kainic acid, KA) on the neural retina from wild type and Cav2.3-deficient mice. Furthermore, the immediately effect of KA on the ERG b-wave modulation was assessed.Methods: Transretinal signaling was recorded as an ERG from the superfused murine retina isolated from wildtype and Cav2.3-deficient miceResults: In mice, the stimulating effect of 100 nM CuCl2 is absent in the retinae from Cav2.3-deficient mice, but prominent in Cav2.3-competent mice. Application of up to 3 mM tricine does not affect the murine b-wave in both genotypes, most likely because of chelating amino acids present in the murine nutrient solution. Application of 27 µM KA significantly increased the b-wave amplitude in wild type and Cav2.3 (-|-) mice. This effect can most likely be explained by the stimulation of endogenous KA-receptors described in horizontal, OFF-bipolar, amacrine or ganglion cells, which could not be fully blocked in the present study.Conclusion: Cu2+ dependent modulation of transretinal signaling only occurs in the murine retina from Cav2.3 competent mice, supporting the ideas derived from previous work in the bovine retina that R-type Ca2+ channels are involved in shaping transretinal responses during light perception.

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Carrier-Mediated GABA Release Activates GABA Receptors on Hippocampal Neurons

Journal of Neurophysiology ◽

10.1152/jn.1998.80.1.270 ◽

1998 ◽

Vol 80 (1) ◽

pp. 270-281 ◽

Cited By ~ 62

Author(s):

Heidi L. Gaspary ◽

Wengang Wang ◽

George B. Richerson

Keyword(s):

Gaba Receptors ◽

Hippocampal Neurons ◽

Reversal Potential ◽

Gaba Release ◽

Receptor Activation ◽

Neuronal Firing ◽

Gaba Transporter ◽

Gaba Transporters ◽

Acid Hydrochloride

Gaspary, Heidi L., Wengang Wang, and George B. Richerson. Carrier-mediated GABA release activates GABA receptors on hippocampal neurons. J. Neurophysiol. 80: 270–281, 1998. γ-Aminobutyric acid (GABA) transporters are electrogenic and sodium-dependent and can operate in reverse when cells are depolarized or when there is reversal of the inward sodium gradient. However, the functional relevance of this phenomenon is unclear. We have examined whether depolarization induced by a physiologically relevant increase in extracellular [K+] leads to sufficient amounts of carrier-mediated GABA release to activate GABAA receptors on neurons. Patch-clamp recordings were made from rat hippocampal neurons in culture with solutions designed to isolate chloride currents in the recorded neuron. Pressure microejection was used to increase extracellular [K+] from 3 to 12 mM. After blockade of vesicular GABA release by removal of extracellular calcium, this stimulus induced a large conductance increase in hippocampal neurons [18.9 ± 6.8 (SD) nS; n = 16]. This was blocked by the GABAA receptor antagonists picrotoxin and bicuculline and had a reversal potential that followed the Nernst potential for chloride, indicating that it was mediated by GABAA receptor activation. Similar responses occurred after block of vesicular neurotransmitter release by tetanus toxin. GABAA receptors also were activated when an increase in extracellular [K+] (from 3 to 13 mM) was combined with a reduction in extracellular [Na+] or when cells were exposed to a decrease in extracellular [Na+] alone. These results indicate that depolarization and/or reversal of the Na+ gradient activated GABA receptors via release of GABA from neighboring cells. We found that the GABA transporter antagonists 1-(4,4-diphenyl-3-butenyl)-3-piperidinecarboxylic acid hydrochloride (SKF89976A; 20–100 μM) and 1-(2-{[(diphenylmethylene)amino]oxy}ethyl) -1, 2, 5, 6 - tetrahydro - 3 - pyridine - carboxylic acid hydrochloride (NO-711; 10 μM) both decreased the responses, indicating that the release of GABA resulted from reversal of the GABA transporter. We propose that carrier-mediated GABA release occurs in vivo during high-frequency neuronal firing and seizures, and dynamically modulates inhibitory tone.

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Lack of functional GABAB receptors alters GnRH physiology and sexual dimorphic expression of GnRH and GAD-67 in the brain

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00532.2009 ◽

2010 ◽

Vol 298 (3) ◽

pp. E683-E696 ◽

Cited By ~ 22

Author(s):

Paolo N. Catalano ◽

Noelia Di Giorgio ◽

María M. Bonaventura ◽

Bernhard Bettler ◽

Carlos Libertun ◽

...

Keyword(s):

Serum Levels ◽

Pulse Frequency ◽

Gabab Receptors ◽

Acid Decarboxylase ◽

Tissue Samples ◽

Inhibitory Neurotransmitter ◽

Qrt Pcr ◽

Adenohypophyseal Cell ◽

Lh Secretion ◽

Dimorphic Expression

GABA, the main inhibitory neurotransmitter, acts through GABAA/C and GABAB receptors (GABABRs); it is critical for gonadotropin regulation. We studied whether the lack of functional GABABRs in GABAB1 knockout (GABAB1KO) mice affected the gonadotropin axis physiology. Adult male and female GABAB1KO 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 GABAB1KO mice. MBH-PH, OB, and CT did not follow this pattern. In GABAB1KO 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 GABAB1KO female ACCs. These results support the hypothesis that the absence of functional GABABRs alters GnRH physiology and critically affects sexual dimorphic expression of GnRH and GAD-67 in POA-AH.

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Submicromolar copper (II) ions stimulate transretinal signaling in the isolated retina from wild type but not from Cav2.3-deficient mice

10.21203/rs.2.16907/v1 ◽

2019 ◽

Author(s):

Toni Schneider ◽

Jan Niklas Lüke ◽

Felix Neumaier ◽

Serdar Alpdogan ◽

Jürgen Hescheler ◽

...

Keyword(s):

Ganglion Cells ◽

Indirect Evidence ◽

Gaba Release ◽

Wild Type ◽

Inhibitory Neurotransmitters ◽

Bovine Retina ◽

Isolated Retina ◽

Deficient Mice ◽

Ca2 Channels ◽

Stimulation Of

Abstract Background: So far, only indirect evidence exists for the pharmacoresistant R-type voltage-gated Ca2+ channel (VGCC) to be involved in transretinal signaling by triggering GABA-release onto ON-bipolar neurons. This release of inhibitory neurotransmitters was deduced from the sensitivity of the b-wave to stimulation by Ni2+ , Zn2+ and Cu2+ . To further confirm the interpretation of these findings, we compared the effects of Cu2+ application and chelation on the neural retina from wildtype and Cav2.3-deficient mice. Furthermore, the effect of kainic acid (KA) on the ERG b-wave modulation was assessed. Methods: Transretinal signaling was recorded as an ERG from the superfused murine retina isolated from wildtype and Cav2.3-deficient mice Results: In mice, the stimulating effect of 100 nM CuCl2 is absent in the retinae from Cav2.3-deficient mice, but prominent in Cav2.3-competent mice. Application of up to 3 mM tricine does not affect the murine b-wave in both genotypes, most likely because of chelating amino acids present in the murine nutrient solution. Application of 27 µM KA significantly increased the b-wave amplitude in wild type and Cav2.3 (-|-) mice. This effect can most likely be explained by the stimulation of endogenous KA-receptors described in horizontal, OFF-bipolar, amacrine or ganglion cells, which could not be fully blocked in the present study. Conclusion: Cu2+ dependent modulation of transretinal signaling only occurs in the murine retina from Cav2.3 competent mice, supporting the ideas derived from previous work in the bovine retina that R-type Ca2+ channels are involved in shaping transretinal responses during light perception.

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Submicromolar copper (II) ions stimulate transretinal signaling in the isolated retina from wild type but not from Cav2.3-deficient mice

10.21203/rs.2.16907/v4 ◽

2020 ◽

Author(s):

Jan Niklas Lüke ◽

Felix Neumaier ◽

Serdar Alpdogan ◽

Jürgen Hescheler ◽

Toni Schneider ◽

...

Keyword(s):

Ganglion Cells ◽

Indirect Evidence ◽

Gaba Release ◽

Light Perception ◽

Wild Type ◽

Inhibitory Neurotransmitters ◽

Bovine Retina ◽

Isolated Retina ◽

Deficient Mice ◽

Stimulation Of

Abstract Background: So far, only indirect evidence exists for the pharmacoresistant R-type voltage-gated Ca2+ channel (VGCC) to be involved in transretinal signaling by triggering GABA-release onto ON-bipolar neurons. This release of inhibitory neurotransmitters was deduced from the sensitivity of the b-wave to stimulation by Ni2+, Zn2+ and Cu2+. To further confirm the interpretation of these findings, we compared the effects of Cu2+ application and chelation (using kainic acid, KA) on the neural retina from wildtype and Cav2.3-deficient mice. Furthermore, the immediately effect of KA on the ERG b-wave modulation was assessed.Methods: Transretinal signaling was recorded as an ERG from the superfused murine retina isolated from wildtype and Cav2.3-deficient mice.Results: In mice, the stimulating effect of 100 nM CuCl2 is absent in the retinae from Cav2.3-deficient mice, but prominent in Cav2.3-competent mice. Application of up to 3 mM tricine does not affect the murine b-wave in both genotypes, most likely because of chelating amino acids present in the murine nutrient solution. Application of 27 µM KA significantly increased the b-wave amplitude in wild type and Cav2.3 (-|-) mice. This effect can most likely be explained by the stimulation of endogenous KA-receptors described in horizontal, OFF-bipolar, amacrine or ganglion cells, which could not be fully blocked in the present study.Conclusion: Cu2+-dependent modulation of transretinal signaling only occurs in the murine retina from Cav2.3 competent mice, supporting the ideas derived from previous work in the bovine retina that R-type Ca2+ channels are involved in shaping transretinal responses during light perception.

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