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Differential Drug Responses on Native GABAA Receptors Revealing Heterogeneity in Extrasynaptic Populations in Cultured Hippocampal Neurons

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Abstract

Hippocampal pyramidal neurons potentially express multiple subtypes of GABAA receptors at extrasynaptic locations that could therefore respond to different drugs. We activated extrasynaptic GABAA receptors in cultured rat hippocampal pyramidal neurons and measured single-channel currents in order to compare the actions of two drugs that potentially target different GABAA receptor subtypes. Despite the possible difference in receptor targets of etomidate and diazepam, the two drugs were similar in their actions on native extrasynaptic GABAA receptors. Each drug produced three distinct responses that differed significantly in current magnitude, implying heterogeneous GABAA receptor populations. In the majority of patches, drug application increased both the single-channel conductance (>40 pS) and the open probability of the channels. By contrast, in the minority of patches, drug application caused an increase in open probability only. In the third group high-conductance channels were observed upon GABA activation and drug application increased their open probability only. The currents potentiated by etomidate or diazepam were substantially larger in patches displaying high-conductance GABA channels compared to those displaying only low-conductance channels. Factors contributing to the large magnitude of these currents were the long mean open time of high-conductance channels and the presence of multiple channels in these patches. In conclusion, we suggest that the local density of extrasynaptic GABAA receptors may influence their single-channel properties and may be an additional regulating factor for tonic inhibition and, importantly, differential drug modulation.

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References

  • Angelotti TP, Macdonald RL (1993) Assembly of GABAA receptor subunits: alpha1 beta1 and alpha1 beta1 gamma 2S subunits produce unique ion channels with dissimilar single-channel properties. J Neurosci 13:1429–1440

    PubMed  CAS  Google Scholar 

  • Bianchi MT, Macdonald RL (2003) Neurosteroids shift partial agonist activation of GABAA receptor channels from low- to high-efficacy gating patterns. J Neurosci 23:10934–10943

    PubMed  CAS  Google Scholar 

  • Birnir B, Everitt AB, Gage PW (1994) Characteristics of GABAA, channels in rat dentate gyrus. J Membr Biol 142:93–102

    PubMed  CAS  Google Scholar 

  • Birnir B, Eghbali M, Cox GB, Gage PW (2001) GABA concentration sets the conductance of delayed GABAA channels in outside–out patches from rat hippocampal neurons. J Membr Biol 181:171–183

    PubMed  CAS  Google Scholar 

  • Bogdanov Y, Michels G, Armstrong-Gold C, Haydon PG, Lindstrom J, Pangalos M, Moss SJ (2006) Synaptic GABAA receptors are directly recruited from their extrasynaptic counterparts. EMBO J 25:4381–4389

    Article  PubMed  CAS  Google Scholar 

  • Brickley SG, Cull-Candy SG, Farrant M (1999) Single-channel properties of synaptic and extrasynaptic GABAA receptors suggest differential targeting of receptor subtypes. J Neurosci 19:2960–2973

    PubMed  CAS  Google Scholar 

  • Brown N, Kerby J, Bonnert TP, Whiting PJ, Wafford KA (2002) Pharmacological characterization of a novel cell line expressing human alpha(4)beta(3)delta GABAA receptors. Br J Pharmacol 136:965–974

    Article  PubMed  CAS  Google Scholar 

  • Caraiscos VB, Elliott EM, You-Ten KE, Cheng VY, Belelli D, Newell JG, Jackson MF, Lambert JJ, Rosahl TW, Wafford KA, MacDonald JF, Orser BA (2004) Tonic inhibition in mouse hippocampal CA1 pyramidal neurons is mediated by alpha5 subunit-containing gamma-aminobutyric acid type A receptors. Proc Natl Acad Sci USA 101:3662–3667

    Article  PubMed  CAS  Google Scholar 

  • Chandra D, Jia F, Liang J, Peng Z, Suryanarayanan A, Werner DF, Spigelman I, Houser CR, Olsen RW, Harrison NL, Homanics GE (2006) GABAA receptor alpha 4 subunits mediate extrasynaptic inhibition in thalamus and dentate gyrus and the action of gaboxadol. Proc Natl Acad Sci USA 103:15230–15235

    Article  PubMed  CAS  Google Scholar 

  • Christie SB, Miralles CP, De Blas AL (2002) GABAergic innervation organizes synaptic and extrasynaptic GABAA receptor clustering in cultured hippocampal neurons. J Neurosci 22:684–697

    PubMed  CAS  Google Scholar 

  • Colquhoun D, Sigworth FJ (1983) Fitting and statistical analysis of single-channel records. Plenum Press, New York

    Google Scholar 

  • Curmi JP, Premkumar LS, Birnir B, Gage PW (1993) The influence of membrane potential on chloride channels activated by GABA in rat cultured hippocampal neurons. J Membr Biol 136:273–280

    PubMed  CAS  Google Scholar 

  • Eghbali M, Curmi JP, Birnir B, Gage PW (1997) Hippocampal GABAA channel conductance increased by diazepam. Nature 388:71–75

    Article  PubMed  CAS  Google Scholar 

  • Farrant M, Nusser Z (2005) Variations on an inhibitory theme: phasic and tonic activation of GABAA receptors. Nat Rev Neurosci 6:215–229

    Article  PubMed  CAS  Google Scholar 

  • Fisher JL, Macdonald RL (1997) Single channel properties of recombinant GABAA receptors containing gamma 2 or delta subtypes expressed with alpha 1 and beta 3 subtypes in mouse L929 cells. J Physiol 505:283–297

    Article  PubMed  CAS  Google Scholar 

  • Fritschy JM, Brünig I (2003) Formation and plasticity of GABAergic synapses: physiological mechanisms and pathophysiological implications. Pharmacol Ther 98:299–323

    Article  PubMed  CAS  Google Scholar 

  • Glykys J, Mann EO, Mody I (2008) Which GABAA receptor subunits are necessary for tonic inhibition in the hippocampus? J Neurosci 28:1421–1426

    Article  PubMed  CAS  Google Scholar 

  • Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981) Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pfluegers Arch 391:85–100

    Article  CAS  Google Scholar 

  • Herd MB, Haythornthwaite AR, Rosahl TW, Wafford KA, Homanics GE, Lambert JJ, Belelli D (2008) The expression of GABAA beta subunit isoforms in synaptic and extrasynaptic receptor populations of mouse dentate gyrus granule cells. J Physiol 586:989–1004

    Article  PubMed  CAS  Google Scholar 

  • Horn R (1987) Statistical methods for model discrimination. Biophys J 51:255–263

    Article  PubMed  CAS  Google Scholar 

  • Leil TA, Chen ZW, Chang CS, Olsen RW (2004) GABAA receptor-associated protein traffics GABAA receptors to the plasma membrane in neurons. J Neurosci 24:11429–11438

    Article  PubMed  CAS  Google Scholar 

  • Luu T, Cromer B, Gage PW, Tierney ML (2005) A role for the 2′ residue in the second transmembrane helix of the GABAA receptor gamma2S subunit in channel conductance and gating. J Membr Biol 205:17–28

    Article  PubMed  CAS  Google Scholar 

  • Luu T, Gage PW, Tierney ML (2006) GABA increases both the conductance and mean open time of recombinant GABAA channels co-expressed with GABARAP. J Biol Chem 281:35699–35708

    Article  PubMed  CAS  Google Scholar 

  • Mangan PS, Sun C, Carpenter M, Goodkin HP, Sieghart W, Kapur J (2005) Cultured hippocampal pyramidal neurons express two kinds of GABAA receptors. Mol Pharmacol 67:775–788

    Article  PubMed  CAS  Google Scholar 

  • Mody I (2005) Aspects of the homeostatic plasticity of GABAA receptor-mediated inhibition. J Physiol 562:37–46

    Article  PubMed  CAS  Google Scholar 

  • Mody I, De Koninck Y, Otis TS, Soltesz I (1994) Bridging the cleft at GABA synapses in the brain. Trends Neurosci 17:517–525

    Article  PubMed  CAS  Google Scholar 

  • Mortensen M, Smart TG (2006) Extrasynaptic alphabeta subunit GABAA receptors on rat hippocampal pyramidal neurons. J Physiol 577:841–856

    Article  PubMed  CAS  Google Scholar 

  • Petrini EM, Zacchi P, Barberis A, Mozrzymas JW, Cherubini E (2003) Declusterization of GABAA receptors affects the kinetic properties of GABAergic currents in cultured hippocampal neurons. J Biol Chem 278:16271–16279

    Article  PubMed  CAS  Google Scholar 

  • Petrini EM, Marchionni I, Zacchi P, Sieghart W, Cherubini E (2004) Clustering of extrasynaptic GABAA receptors modulates tonic inhibition in cultured hippocampal neurons. J Biol Chem 279:45833–45843

    Article  PubMed  CAS  Google Scholar 

  • Rogers CJ, Twyman RE, Macdonald RL (1994) Benzodiazepine and beta-carboline regulation of single GABAA receptor channels of mouse spinal neurones in culture. J Physiol 475:69–82

    PubMed  CAS  Google Scholar 

  • Sigel E, Baur R (1988) Allosteric modulation by benzodiazepine receptor ligands of the GABAA receptor channel expressed in Xenopus oocytes. J Neurosci 8:289–295

    PubMed  CAS  Google Scholar 

  • Sigworth FJ, Sine SM (1987) Data transformations for improved display and fitting of single-channel dwell time histograms. Biophys J 52:1047–1054

    Article  PubMed  CAS  Google Scholar 

  • Stell BM, Brickley SG, Tang CY, Farrant M, Mody I (2003) Neuroactive steroids reduce neuronal excitability by selectively enhancing tonic inhibition mediated by delta subunit-containing GABAA receptors. Proc Natl Acad Sci USA 100:14439–14444

    Article  PubMed  CAS  Google Scholar 

  • Uchida I, Kamatchi G, Burt D, Yang J (1995) Etomidate potentiation of GABAA receptor gated current depends on the subunit composition. Neurosci Lett 185:203–206

    Article  PubMed  CAS  Google Scholar 

  • Yang J, Uchida I (1996) Mechanisms of etomidate potentiation of GABAA receptor-gated currents in cultured postnatal hippocampal neurons. Neuroscience 73:69–78

    Article  PubMed  CAS  Google Scholar 

Download references

Acknowledgement

This study was funded by a grant from the Australian NHMRC (418027).

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Authors and Affiliations

  1. Division of Molecular Bioscience, The John Curtin School of Medical Research, The Australian National University, Building 54, Garran Road, Canberra, ACT, 0200, Australia

    Victoria A. L. Seymour, Andrea B. Everitt & M. Louise Tierney

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  1. Victoria A. L. Seymour
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  2. Andrea B. Everitt
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  3. M. Louise Tierney
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Correspondence to M. Louise Tierney.

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This work is dedicated to the memory of Professor P. W. Gage.

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Seymour, V.A.L., Everitt, A.B. & Tierney, M.L. Differential Drug Responses on Native GABAA Receptors Revealing Heterogeneity in Extrasynaptic Populations in Cultured Hippocampal Neurons. J Membrane Biol 227, 111–122 (2009). https://doi.org/10.1007/s00232-008-9150-4

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  • DOI: https://doi.org/10.1007/s00232-008-9150-4

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