 |
 Previous Article | Next Article 
Volume 17, Number 2,
Issue of January 15, 1997
pp. 625-634
Copyright ©1997 Society for Neuroscience
Bicuculline and Gabazine Are Allosteric Inhibitors of Channel
Opening of the GABAA Receptor
Received Aug. 15, 1996; revised Oct. 31, 1996; accepted Nov. 15, 1996.
Shinya Ueno1,
John Bracamontes1,
Chuck Zorumski2,
David S. Weiss3, and
Joe Henry Steinbach1
Departments of 1 Anesthesiology and
2 Psychiatry, Washington University School of Medicine, St.
Louis, Missouri 63110, and 3 University of Alabama at
Birmingham, Neurobiology Research Center and Department of Physiology
and Biophysics, Birmingham, Alabama 35294-0021
Anesthetic drugs are known to interact with GABAA
receptors, both to potentiate the effects of low concentrations of GABA and to directly gate open the ion channel in the absence of GABA; however, the site(s) involved in direct gating by these drugs is not
known. We have studied the ability of alphaxalone (an anesthetic steroid) and pentobarbital (an anesthetic barbiturate) to directly activate recombinant GABAA receptors containing the  1,
 2, and  2L subunits. Steroid gating was not affected when either
of two mutated 2 subunits [2(Y157S) and 2(Y205S)] are
incorporated into the receptors, although these subunits greatly reduce
the affinity of GABA binding. These observations indicate that steroid binding and subsequent channel gating do not require these particular residues, as already shown for barbiturates. Bicuculline or gabazine (two competitive antagonists of GABA binding) reduced the currents elicited by alphaxalone and pentobarbital from wild-type
GABAA receptors; however, gabazine produced only a partial
block of responses to pentobarbital or alphaxalone, and bicuculline
only partially blocked responses to pentobarbital. These observations indicate that the blockers do not compete with alphaxalone or pentobarbital for a single class of sites on the GABAA
receptor. Finally, at receptors containing 12(Y157S)2L
subunits, both bicuculline and gabazine showed weak agonist activity
and actually potentiated responses to alphaxalone. These observations
indicate that the blocking drugs can produce allosteric changes in
GABAA receptors, at least those containing this mutated
2 subunit. We conclude that the sites for binding steroids and
barbiturates do not overlap with the GABA-binding site. Furthermore,
neither gabazine nor bicuculline competes for binding at the steroid or barbiturate sites. The data are consistent with a model in which both
gabazine and bicuculline act as allosteric inhibitors of channel
opening for the GABAA receptor after binding to the
GABA-binding site.
Key words:
GABAA receptor;
GABA;
neurosteroids;
bicuculline;
inverse agonist;
anesthetics;
allosteric inhibitor
This article has been cited by other articles:
|
|
|
|
 
D. Demazumder and J. P. Dilger
The kinetics of competitive antagonism of nicotinic acetylcholine receptors at physiological temperature
J. Physiol.,
February 15, 2008;
586(4):
951 - 963.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. R. McCartney, T. Z. Deeb, T. N. Henderson, and T. G. Hales
Tonically Active GABAA Receptors in Hippocampal Pyramidal Neurons Exhibit Constitutive GABA-Independent Gating
Mol. Pharmacol.,
February 1, 2007;
71(2):
539 - 548.
[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]
|
|
|
|
|
|
|
J. Ren and J. J. Greer
Neurosteroid modulation of respiratory rhythm in rats during the perinatal period
J. Physiol.,
July 15, 2006;
574(2):
535 - 546.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Akk and J. H. Steinbach
Galantamine Activates Muscle-Type Nicotinic Acetylcholine Receptors without Binding to the Acetylcholine-Binding Site
J. Neurosci.,
February 23, 2005;
25(8):
1992 - 2001.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Sedelnikova, C. D. Smith, S. O. Zakharkin, D. Davis, D. S. Weiss, and Y. Chang
Mapping the {rho}1 GABAC Receptor Agonist Binding Pocket: CONSTRUCTING A COMPLETE MODEL
J. Biol. Chem.,
January 14, 2005;
280(2):
1535 - 1542.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. G. Newell, R. A. McDevitt, and C. Czajkowski
Mutation of Glutamate 155 of the GABAA Receptor {beta}2 Subunit Produces a Spontaneously Open Channel: A Trigger for Channel Activation
J. Neurosci.,
December 15, 2004;
24(50):
11226 - 11235.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. S. Chan, R. Shigemoto, J. N. Mercer, and D. J. Surmeier
HCN2 and HCN1 Channels Govern the Regularity of Autonomous Pacemaking and Synaptic Resetting in Globus Pallidus Neurons
J. Neurosci.,
November 3, 2004;
24(44):
9921 - 9932.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. C. Bieda and M. B. MacIver
Major Role For Tonic GABAA Conductances in Anesthetic Suppression of Intrinsic Neuronal Excitability
J Neurophysiol,
September 1, 2004;
92(3):
1658 - 1667.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
H.-J. Shu, L. N. Eisenman, D. Jinadasa, D. F. Covey, C. F. Zorumski, and S. Mennerick
Slow Actions of Neuroactive Steroids at GABAA Receptors
J. Neurosci.,
July 28, 2004;
24(30):
6667 - 6675.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Akk, J. Bracamontes, and J. H. Steinbach
Activation of GABAA receptors containing the {alpha}4 subunit by GABA and pentobarbital
J. Physiol.,
April 15, 2004;
556(2):
387 - 399.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. Darbandi-Tonkabon, B. D. Manion, W. R. Hastings, W. J. Craigen, G. Akk, J. R. Bracamontes, Y. He, T. V. Sheiko, J. H. Steinbach, S. J. Mennerick, et al.
Neuroactive Steroid Interactions with Voltage-Dependent Anion Channels: Lack of Relationship to GABAA Receptor Modulation and Anesthesia
J. Pharmacol. Exp. Ther.,
February 1, 2004;
308(2):
502 - 511.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. W. Baumann, R. Baur, and E. Sigel
Individual Properties of the Two Functional Agonist Sites in GABAA Receptors
J. Neurosci.,
December 3, 2003;
23(35):
11158 - 11166.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Eghbali, B. Birnir, and P. W Gage
Conductance of GABAA Channels Activated by Pentobarbitone in Hippocampal Neurons from Newborn Rats
J. Physiol.,
October 1, 2003;
552(1):
13 - 22.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
I. Dean, S. J. Robertson, and F. A. Edwards
Serotonin Drives a Novel GABAergic Synaptic Current Recorded in Rat Cerebellar Purkinje Cells: A Lugaro Cell to Purkinje Cell Synapse
J. Neurosci.,
June 1, 2003;
23(11):
4457 - 4469.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Bacci, J. R. Huguenard, and D. A. Prince
Functional Autaptic Neurotransmission in Fast-Spiking Interneurons: A Novel Form of Feedback Inhibition in the Neocortex
J. Neurosci.,
February 1, 2003;
23(3):
859 - 866.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Y. T. Yeung, K. J. Canning, G. Zhu, P. Pennefather, J. F. MacDonald, and B. A. Orser
Tonically Activated GABAA Receptors in Hippocampal Neurons Are High-Affinity, Low-Conductance Sensors for Extracellular GABA
Mol. Pharmacol.,
January 1, 2003;
63(1):
2 - 8.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
G. Lowe
Inhibition of Backpropagating Action Potentials in Mitral Cell Secondary Dendrites
J Neurophysiol,
July 1, 2002;
88(1):
64 - 85.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. T. Bianchi and R. L. Macdonald
Agonist Trapping by GABAA Receptor Channels
J. Neurosci.,
December 1, 2001;
21(23):
9083 - 9091.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Chang, Y. Xie, and D. S Weiss
Positive allosteric modulation by ultraviolet irradiation on GABAA, but not GABAC, receptors expressed in Xenopus oocytes
J. Physiol.,
October 15, 2001;
536(2):
471 - 478.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. Sigel, R. Baur, R. Furtmueller, R. Razet, R. H. Dodd, and W. Sieghart
Differential Cross Talk of ROD Compounds with the Benzodiazepine Binding Site
Mol. Pharmacol.,
June 1, 2001;
59(6):
1470 - 1477.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
G. Akk, J. Bracamontes, and J. H. Steinbach
Pregnenolone sulfate block of GABAA receptors: mechanism and involvement of a residue in the M2 region of the {alpha} subunit
J. Physiol.,
May 1, 2001;
532(3):
673 - 684.
[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]
|
|
|
|
|
|
|
S. R. Engel, R. H. Purdy, and K. A. Grant
Characterization of Discriminative Stimulus Effects of the Neuroactive Steroid Pregnanolone
J. Pharmacol. Exp. Ther.,
April 12, 2001;
297(2):
489 - 495.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
D. Bai, G. Zhu, P. Pennefather, M. F. Jackson, J. F. MacDonald, and B. A. Orser
Distinct Functional and Pharmacological Properties of Tonic and Quantal Inhibitory Postsynaptic Currents Mediated by {gamma}-Aminobutyric AcidA Receptors in Hippocampal Neurons
Mol. Pharmacol.,
April 1, 2001;
59(4):
814 - 824.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
D. A. Wagner and C. Czajkowski
Structure and Dynamics of the GABA Binding Pocket: A Narrowing Cleft that Constricts during Activation
J. Neurosci.,
January 1, 2001;
21(1):
67 - 74.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Eghbali, P. W. Gage, and B. Birnir
Pentobarbital Modulates gamma -Aminobutyric Acid-Activated Single-Channel Conductance in Rat Cultured Hippocampal Neurons
Mol. Pharmacol.,
September 1, 2000;
58(3):
463 - 469.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
R. Serafini, J. Bracamontes, and J. H. Steinbach
Structural domains of the human GABAA receptor {beta}3 subunit involved in the actions of pentobarbital
J. Physiol.,
May 1, 2000;
524(3):
649 - 676.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. I. Banks and R. A. Pearce
Kinetic Differences between Synaptic and Extrasynaptic GABAA Receptors in CA1 Pyramidal Cells
J. Neurosci.,
February 1, 2000;
20(3):
937 - 948.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
B. D. Bennett and C. J. Wilson
Spontaneous Activity of Neostriatal Cholinergic Interneurons In Vitro
J. Neurosci.,
July 1, 1999;
19(13):
5586 - 5596.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Y. Kurata, W. Marszalec, J. Z. Yeh, and T. Narahashi
Agonist and Potentiation Actions of n-Octanol on gamma -Aminobutyric Acid Type A Receptors
Mol. Pharmacol.,
June 1, 1999;
55(6):
1011 - 1019.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
T. R. Neelands, J. L. Fisher, M. Bianchi, and R. L. Macdonald
Spontaneous and gamma -Aminobutyric Acid (GABA)-Activated GABAA Receptor Channels Formed by epsilon Subunit-Containing Isoforms
Mol. Pharmacol.,
January 1, 1999;
55(1):
168 - 178.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
M. V. Jones, Y. Sahara, J. A. Dzubay, and G. L. Westbrook
Defining Affinity with the GABAA Receptor
J. Neurosci.,
November 1, 1998;
18(21):
8590 - 8604.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. V. Jones and G. L. Westbrook
Shaping of IPSCs by Endogenous Calcineurin Activity
J. Neurosci.,
October 15, 1997;
17(20):
7626 - 7633.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L. S. Aspinwall, I. Bermudez, L. A. King, and K. A. Wafford
The Interactions of Hexachlorocyclohexane Isomers with Human gamma -Aminobutyric AcidA Receptors Expressed in Xenopus Oocytes
J. Pharmacol. Exp. Ther.,
September 1, 1997;
282(3):
1557 - 1564.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
A. J. Boileau, J. G. Newell, and C. Czajkowski
GABAA Receptor beta 2 Tyr97 and Leu99 Line the GABA-binding Site. INSIGHTS INTO MECHANISMS OF AGONIST AND ANTAGONIST ACTIONS
J. Biol. Chem.,
January 18, 2002;
277(4):
2931 - 2937.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
