Pharmacological modulation of the diazepam-insensitive recombinant gamma-aminobutyric acidA receptors alpha 4 beta 2 gamma 2 and alpha 6 beta 2 gamma 2

F Knoflach, D Benke, Y Wang, L Scheurer, H Luddens, BJ Hamilton, DB Carter, H Mohler and JA Benson

Institute of Pharmacology, University of Zurich, Switzerland.

We characterized modulation of the gamma-aminobutyric acid (GABA)- evoked responses of the diazepam-insensitive alpha 4 beta 2 gamma2 and alpha 6 beta 2 gamma 2 recombinant GABAA receptors. The partial agonist bretazenil potentiated the responses of both receptors with similar dose dependence but with a higher maximal enhancement at the alpha 4 beta 2 gamma 2 receptor. The bretazenil-induced potentiation was reduced by the benzodiazepine antagonist flumazenil. At a high concentration (10 microM), flumazenil was a weak potentiator of the GABA response. The partial agonist imidazenil was inactive. The imidazobenzodiazepine inverse agonist Ro 15-4513, which is known to bind with high affinity to the alpha 6 beta 2 gamma 2 receptor, potentiated the GABA responses of the alpha 4 beta 2 gamma 2 and alpha 6 beta 2 gamma 2 receptor subtypes with similar dose dependence over the concentration range of 0.1-10 microM. Methyl-6, 7-dimethoxy-4-ethyl- beta-carboline, a beta-carboline inverse agonist, had a similar potentiating effect when tested at a concentration of 10 microM. The alpha 4 beta 2 gamma 2 and alpha 6 beta 2 gamma 2 receptor-mediated currents had equal sensitivities to furosemide and Zn2+ ions, both of which reduced the GABA-evoked responses. The alpha 6 beta 2 gamma 2 receptor but not the alpha 4 beta 2 gamma 2 receptor exhibited a low level of spontaneous activity in the absence of GABA; this resting current could be directly potentiated by Ro 15-4513, methyl-6,7- dimethoxy-4-ethyl-beta-carboline, bretazenil and flumazenil and was blocked by picrotoxin. Thus, although the alpha 4 beta 2 gamma 2 receptors are insensitive to benzodiazepine binding site full agonists, such as diazepam, they can be modulated by certain ligands acting as partial and inverse agonists at diazepam-sensitive receptors and thereby contribute to the respective pharmacological profiles.

Volume 50, Issue 5, pp. 1253-1261, 11/01/1996
Copyright © 1996 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				A. B. Ali and A. M. Thomson Synaptic {alpha}5 Subunit-Containing GABAA Receptors Mediate IPSPs Elicited by Dendrite-Preferring Cells in Rat Neocortex Cereb Cortex, June 1, 2008; 18(6): 1260 - 1271. [Abstract] [Full Text] [PDF]

				A. Keramidas and N. L. Harrison Agonist-dependent Single Channel Current and Gating in {alpha}4{beta}2{delta} and {alpha}1{beta}2{gamma}2S GABAA Receptors J. Gen. Physiol., January 28, 2008; 131(2): 163 - 181. [Abstract] [Full Text] [PDF]

				C. Sun, Z. Mtchedlishvili, A. Erisir, and J. Kapur Diminished Neurosteroid Sensitivity of Synaptic Inhibition and Altered Location of the {alpha}4 Subunit of GABAA Receptors in an Animal Model of Epilepsy J. Neurosci., November 14, 2007; 27(46): 12641 - 12650. [Abstract] [Full Text] [PDF]

				M. Mortensen and T. G. Smart Extrasynaptic {alpha}{beta} subunit GABAA receptors on rat hippocampal pyramidal neurons J. Physiol., December 15, 2006; 577(3): 841 - 856. [Abstract] [Full Text] [PDF]

				D. S. Roberts, Y. Hu, I. V. Lund, A. R. Brooks-Kayal, and S. J. Russek Brain-derived Neurotrophic Factor (BDNF)-induced Synthesis of Early Growth Response Factor 3 (Egr3) Controls the Levels of Type A GABA Receptor{alpha}4 Subunits in Hippocampal Neurons J. Biol. Chem., October 6, 2006; 281(40): 29431 - 29435. [Abstract] [Full Text] [PDF]

				M. Yamashita, W. Marszalec, J. Z. Yeh, and T. Narahashi Effects of Ethanol on Tonic GABA Currents in Cerebellar Granule Cells and Mammalian Cells Recombinantly Expressing GABAA Receptors J. Pharmacol. Exp. Ther., October 1, 2006; 319(1): 431 - 438. [Abstract] [Full Text] [PDF]

				V. C. Cuzon, P. W. Yeh, Q. Cheng, and H. H. Yeh Ambient GABA Promotes Cortical Entry of Tangentially Migrating Cells Derived from the Medial Ganglionic Eminence Cereb Cortex, October 1, 2006; 16(10): 1377 - 1388. [Abstract] [Full Text] [PDF]

				G. Pinna, R. C. Agis-Balboa, A. Zhubi, K. Matsumoto, D. R. Grayson, E. Costa, and A. Guidotti Imidazenil and diazepam increase locomotor activity in mice exposed to protracted social isolation. PNAS, March 14, 2006; 103(11): 4275 - 4280. [Abstract] [Full Text] [PDF]

				J. Liang, N. Zhang, E. Cagetti, C. R. Houser, R. W. Olsen, and I. Spigelman Chronic Intermittent Ethanol-Induced Switch of Ethanol Actions from Extrasynaptic to Synaptic Hippocampal GABAA Receptors J. Neurosci., February 8, 2006; 26(6): 1749 - 1758. [Abstract] [Full Text] [PDF]

				F. Jia, L. Pignataro, C. M. Schofield, M. Yue, N. L. Harrison, and P. A. Goldstein An Extrasynaptic GABAA Receptor Mediates Tonic Inhibition in Thalamic VB Neurons J Neurophysiol, December 1, 2005; 94(6): 4491 - 4501. [Abstract] [Full Text] [PDF]

				D. S. Roberts, Y. H. Raol, S. Bandyopadhyay, I. V. Lund, E. C. Budreck, M. A. Passini, J. H. Wolfe, A. R. Brooks-Kayal, and S. J. Russek Egr3 stimulation of GABRA4 promoter activity as a mechanism for seizure-induced up-regulation of GABAA receptor {alpha}4 subunit expression PNAS, August 16, 2005; 102(33): 11894 - 11899. [Abstract] [Full Text] [PDF]

				P. I. Ortinski, C. Lu, K. Takagaki, Z. Fu, and S. Vicini Expression of Distinct {alpha} Subunits of GABAA Receptor Regulates Inhibitory Synaptic Strength J Neurophysiol, September 1, 2004; 92(3): 1718 - 1727. [Abstract] [Full Text] [PDF]

				J. Liang, E. Cagetti, R. W. Olsen, and I. Spigelman Altered Pharmacology of Synaptic and Extrasynaptic GABAA Receptors on CA1 Hippocampal Neurons Is Consistent with Subunit Changes in a Model of Alcohol Withdrawal and Dependence J. Pharmacol. Exp. Ther., September 1, 2004; 310(3): 1234 - 1245. [Abstract] [Full Text] [PDF]

				I. Bohme, H. Rabe, and H. Luddens Four Amino Acids in the {alpha} Subunits Determine the {gamma}-Aminobutyric Acid Sensitivities of GABAA Receptor Subtypes J. Biol. Chem., August 20, 2004; 279(34): 35193 - 35200. [Abstract] [Full Text] [PDF]

				B. C. Drafts and J. L. Fisher Structural Determinants of the Pharmacological Properties of the GABAA Receptor {alpha}6 Subunit J. Pharmacol. Exp. Ther., June 1, 2004; 309(3): 1108 - 1115. [Abstract] [Full Text] [PDF]

				S. T. Sinkkonen, S. Mansikkamaki, T. Moykkynen, H. Luddens, M. Uusi-Oukari, and E. R. Korpi Receptor Subtype-Dependent Positive and Negative Modulation of GABAA Receptor Function by Niflumic Acid, a Nonsteroidal Anti-Inflammatory Drug Mol. Pharmacol., September 1, 2003; 64(3): 753 - 763. [Abstract] [Full Text] [PDF]

				E. Cagetti, J. Liang, I. Spigelman, and R. W. Olsen Withdrawal from Chronic Intermittent Ethanol Treatment Changes Subunit Composition, Reduces Synaptic Function, and Decreases Behavioral Responses to Positive Allosteric Modulators of GABAA Receptors Mol. Pharmacol., January 1, 2003; 63(1): 53 - 64. [Abstract] [Full Text] [PDF]

				G. W. Sawyer, D. C. Chiara, R. W. Olsen, and J. B. Cohen Identification of the Bovine gamma -Aminobutyric Acid Type A Receptor alpha Subunit Residues Photolabeled by the Imidazobenzodiazepine [3H]Ro15-4513 J. Biol. Chem., December 13, 2002; 277(51): 50036 - 50045. [Abstract] [Full Text] [PDF]

				R.-Q. Huang and G. H. Dillon Functional Characterization of GABAA Receptors in Neonatal Hypothalamic Brain Slice J Neurophysiol, October 1, 2002; 88(4): 1655 - 1663. [Abstract] [Full Text] [PDF]

				J. L. Fisher Amiloride Inhibition of gamma -Aminobutyric AcidA Receptors Depends upon the alpha Subunit Subtype Mol. Pharmacol., June 1, 2002; 61(6): 1322 - 1328. [Abstract] [Full Text] [PDF]

				S. H. Browne, J. Kang, G. Akk, L. W. Chiang, H. Schulman, J. R. Huguenard, and D. A. Prince Kinetic and Pharmacological Properties of GABAA Receptors in Single Thalamic Neurons and GABAA Subunit Expression J Neurophysiol, November 1, 2001; 86(5): 2312 - 2322. [Abstract] [Full Text] [PDF]

				C. E. Adkins, G. V. Pillai, J. Kerby, T. P. Bonnert, C. Haldon, R. M. McKernan, J. E. Gonzalez, K. Oades, P. J. Whiting, and P. B. Simpson alpha 4beta 3delta GABAA Receptors Characterized by Fluorescence Resonance Energy Transfer-derived Measurements of Membrane Potential J. Biol. Chem., October 12, 2001; 276(42): 38934 - 38939. [Abstract] [Full Text] [PDF]

				P. Molnar and J. V. Nadler Lack of Effect of Mossy Fiber-Released Zinc on Granule Cell GABAA Receptors in the Pilocarpine Model of Epilepsy J Neurophysiol, May 1, 2001; 85(5): 1932 - 1940. [Abstract] [Full Text] [PDF]

				A. J. Smith, L. Alder, J. Silk, C. Adkins, A. E. Fletcher, T. Scales, J. Kerby, G. Marshall, K. A. Wafford, R. M. McKernan, et al. Effect of alpha Subunit on Allosteric Modulation of Ion Channel Function in Stably Expressed Human Recombinant gamma -Aminobutyric AcidA Receptors Determined Using 36Cl Ion Flux Mol. Pharmacol., April 16, 2001; 59(5): 1108 - 1118. [Abstract] [Full Text]

				J. W. Gibbs III, Y.-F. Zhang, M. D. Shumate, and D. A. Coulter Regionally Selective Blockade of GABAergic Inhibition by Zinc in the Thalamocortical System: Functional Significance J Neurophysiol, March 1, 2000; 83(3): 1510 - 1521. [Abstract] [Full Text] [PDF]

				C. Sur, S. J. Farrar, J. Kerby, P. J. Whiting, J. R. Atack, and R. M. McKernan Preferential Coassembly of alpha 4 and delta  Subunits of the gamma -Aminobutyric AcidA Receptor in Rat Thalamus Mol. Pharmacol., July 1, 1999; 56(1): 110 - 115. [Abstract] [Full Text]

				J. Kapur and R. L. Macdonald Postnatal Development of Hippocampal Dentate Granule Cell gamma -Aminobutyric AcidA Receptor Pharmacological Properties Mol. Pharmacol., March 1, 1999; 55(3): 444 - 452. [Abstract] [Full Text]

				S. S. Smith, Q. H. Gong, X. Li, M. H. Moran, D. Bitran, C. A. Frye, and F.-C. Hsu Withdrawal from 3alpha -OH-5alpha -Pregnan-20-One Using a Pseudopregnancy Model Alters the Kinetics of Hippocampal GABAA-Gated Current and Increases the GABAA Receptor alpha 4 Subunit in Association with Increased Anxiety J. Neurosci., July 15, 1998; 18(14): 5275 - 5284. [Abstract] [Full Text] [PDF]

				J. L. Fisher and R. L. Macdonald The Role of an alpha  Subtype M2-M3 His in Regulating Inhibition of GABAA Receptor Current by Zinc and Other Divalent Cations J. Neurosci., April 15, 1998; 18(8): 2944 - 2953. [Abstract] [Full Text] [PDF]