Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
Front Neurosci
2020 Jan 01;14:599812. doi: 10.3389/fnins.2020.599812.
Show Gene links
Show Anatomy links
The Z-Drugs Zolpidem, Zaleplon, and Eszopiclone Have Varying Actions on Human GABA A Receptors Containing γ1, γ2, and γ3 Subunits.
Richter G
,
Liao VWY
,
Ahring PK
,
Chebib M
.
???displayArticle.abstract???
γ-Aminobutyric-acid type A (GABA A ) receptors expressing the γ1 or γ3 subunit are only found within a few regions of the brain, some of which are involved in sleep. No known compounds have been reported to selectively target γ1- or γ3-containing GABA A receptors. Pharmacological assessments of this are conflicting, possibly due to differences in experimental models, conditions, and exact protocols when reporting efficacies and potencies. In this study, we evaluated the modulatory properties of five non-benzodiazepine Z-drugs (zaleplon, indiplon, eszopiclone, zolpidem, and alpidem) used in sleep management and the benzodiazepine, diazepam on human α1β2γ receptors using all three γ subtypes. This was accomplished using concatenated GABA A pentamers expressed in Xenopus laevis oocytes and measured via two-electrode voltage clamp. This approach removes the potential for single subunits to form erroneous receptors that could contribute to the pharmacological assessment of these compounds. No compound tested had significant effects on γ1-containing receptors below 10 μM. Interestingly, zaleplon and indiplon were found to modulate γ3-containing receptors equally as efficacious as γ2-containing receptors. Furthermore, zaleplon had a higher potency for γ3- than for γ2-containing receptors, indicating certain therapeutic effects could occur via these γ3-containing receptors. Eszopiclone modulated γ3-containing receptors with reduced efficacy but no reduction in potency. These data demonstrate that the imidazopyridines zaleplon and indiplon are well suited to further investigate potential γ3 effects on sleep in vivo.
FIGURE 1. A schematic diagram of a concatenated pentamer GABAA receptor construct. Linkers concatenating subunits are shown as arrows. The GABA binding site (orange arrowhead) is shown between the β2(+) and α(–) interfaces and the benzodiazepine binding site (gray arrowhead) is between the α1(+) and γ(–) interfaces.
FIGURE 2. Chemical structures and classes of the drugs used in this study.
FIGURE 3. (A) Normalized GABA concentration-response curves of α1β2γx receptors (x = 1,2,3) expressed as concatenated pentamers in Xenopus laevis oocytes measured via two-electrode voltage clamp. Oocytes were injected with 50 nL of 0.5 ng/nL cRNA for each concatenated construct. Datapoints are depicted as means ± SD (n = 12–14). Data were fitted by non-linear regression to the Hill equation with an unconstrained Hill slope. Log(EC50) and Hill slope parameters are as follows; γ1 Log(EC50) = –3.82 ± 0.07 Hill slope = 1.22 ± 0.32, γ2 Log(EC50) = –3.96 ± 0.10 Hill slope = 1.19 ± 0.55, γ3 Log(EC50) = –4.38 ± 0.07 Hill slope = 1.36 ± 0.63. (B) Representative traces of each construct with indicated concatenated subunit combination. Application bars designate 30 s application time and concentrations of GABA are indicated at the peak of each trace.
FIGURE 4. Modulatory actions of zaleplon, indiplon, eszopiclone, diazepam, zolpidem, and alpidem, on GABA evoked Cl– currents measured in human (A) α1β2γ1, (B) α1β2γ2, and (C) α1β2γ3 GABAA receptors expressed in Xenopus laevis oocytes measured via two-electrode voltage-clamp. The data are expressed as a percentage potentiation of GABA EC10 and are means ± SD (n = 4–8 from at least 2 separate Xenopus laevis donors). Data points were fitted to the Hill equation with bottom set to 0 and slope constrained to 1. (D–F) Representative traces illustrating modulator concentration-response experiments.
FIGURE 5. Modulatory actions of (A) zaleplon, (B) indiplon, (C) eszopiclone, (D) diazepam, (E) zolpidem, and (F) alpidem, on GABA evoked Cl– currents measured in human α1β2γ1, α1β2γ2, and α1β2γ3 GABAA receptors expressed in Xenopus laevis oocytes measured via two-electrode voltage-clamp. The data are expressed as a percentage potentiation of GABA EC10 and are means ± SD (n = 4–8 from at least 2 separate Xenopus laevis donors). Data points were fitted to the Hill equation with bottom set to 0 and slope constrained to 1.
FIGURE 6. Modulatory actions of 10 μM (A) zaleplon, (B) indiplon, (C) eszopiclone, (D) diazepam, (E) zolpidem, and (F) alpidem, on GABA evoked Cl– currents measured in human α1β2γ1, α1β2γ2, α1β2γ3, and binary α1β2 GABAA receptors expressed in Xenopus laevis oocytes measured via two-electrode voltage-clamp. Data are expressed as percentage potentiation of GABA EC10 and are means ± SD (n = 3–8 from at least 2 separate Xenopus laevis donors). One-way ANOVA with post hoc Sidak multiple comparisons test were calculated between all compounds on γ1 vs. α1β2 and between zolpidem and alpidem on γ3 vs. α1β2; *p < 0.01.
Ahring,
Concatenated nicotinic acetylcholine receptors: A gift or a curse?
2018, Pubmed,
Xenbase
Ahring,
Concatenated nicotinic acetylcholine receptors: A gift or a curse?
2018,
Pubmed
,
Xenbase
Ahring,
A pharmacological assessment of agonists and modulators at α4β2γ2 and α4β2δ GABAA receptors: The challenge in comparing apples with oranges.
2016,
Pubmed
,
Xenbase
Arbilla,
Pharmacological profile of the imidazopyridine zolpidem at benzodiazepine receptors and electrocorticogram in rats.
1985,
Pubmed
Benke,
GABAA receptor subtypes differentiated by their gamma-subunit variants: prevalence, pharmacology and subunit architecture.
1996,
Pubmed
Benson,
Pharmacology of recombinant gamma-aminobutyric acidA receptors rendered diazepam-insensitive by point-mutated alpha-subunits.
1998,
Pubmed
Boileau,
The relative amount of cRNA coding for gamma2 subunits affects stimulation by benzodiazepines in GABA(A) receptors expressed in Xenopus oocytes.
2002,
Pubmed
,
Xenbase
Bovolin,
Expression patterns of gamma-aminobutyric acid type A receptor subunit mRNAs in primary cultures of granule neurons and astrocytes from neonatal rat cerebella.
1992,
Pubmed
Buhr,
A point mutation in the gamma2 subunit of gamma-aminobutyric acid type A receptors results in altered benzodiazepine binding site specificity.
1997,
Pubmed
,
Xenbase
Cope,
Abolition of zolpidem sensitivity in mice with a point mutation in the GABAA receptor gamma2 subunit.
2004,
Pubmed
Davies,
Characterization of the interaction of zopiclone with gamma-aminobutyric acid type A receptors.
2000,
Pubmed
,
Xenbase
Ebert,
Molecular pharmacology of gamma-aminobutyric acid type A receptor agonists and partial agonists in oocytes injected with different alpha, beta, and gamma receptor subunit combinations.
1994,
Pubmed
,
Xenbase
Esmaeili,
GABAA receptors containing gamma1 subunits contribute to inhibitory transmission in the central amygdala.
2009,
Pubmed
Fleming,
A sleep laboratory evaluation of the long-term efficacy of zopiclone.
1988,
Pubmed
Gent,
Sleep-wake control and the thalamus.
2018,
Pubmed
Hadingham,
Expression and pharmacology of human GABAA receptors containing gamma 3 subunits.
1995,
Pubmed
,
Xenbase
Herb,
The third gamma subunit of the gamma-aminobutyric acid type A receptor family.
1992,
Pubmed
Hertz,
The astrocytic GABA(A)/benzodiazepine-like receptor: the Joker receptor for benzodiazepine-mimetic drugs?
2006,
Pubmed
Jia,
The modulation of synaptic GABA(A) receptors in the thalamus by eszopiclone and zolpidem.
2009,
Pubmed
Khom,
Pharmacological properties of GABAA receptors containing gamma1 subunits.
2006,
Pubmed
,
Xenbase
Klimm,
Zopiclone versus nitrazepam: a double-blind comparative study of efficacy and tolerance in elderly patients with chronic insomnia.
1987,
Pubmed
Knoflach,
The gamma 3-subunit of the GABAA-receptor confers sensitivity to benzodiazepine receptor ligands.
1991,
Pubmed
,
Xenbase
Kopp,
Sleep EEG changes after zolpidem in mice.
2004,
Pubmed
Kumar,
Central nervous system sites of the sleep promoting effects of eszopiclone in rats.
2011,
Pubmed
Laurie,
The distribution of thirteen GABAA receptor subunit mRNAs in the rat brain. III. Embryonic and postnatal development.
1992,
Pubmed
Liao,
Concatenated γ-aminobutyric acid type A receptors revisited: Finding order in chaos.
2019,
Pubmed
Lippa,
Selective anxiolysis produced by ocinaplon, a GABA(A) receptor modulator.
2005,
Pubmed
,
Xenbase
Lüddens,
Impact of beta and gamma variants on ligand-binding properties of gamma-aminobutyric acid type A receptors.
1994,
Pubmed
Masiulis,
GABAA receptor signalling mechanisms revealed by structural pharmacology.
2019,
Pubmed
McKernan,
The pharmacology of the benzodiazepine site of the GABA-A receptor is dependent on the type of gamma-subunit present.
1995,
Pubmed
,
Xenbase
McKernan,
Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype.
2000,
Pubmed
Nutt,
Searching for perfect sleep: the continuing evolution of GABAA receptor modulators as hypnotics.
2010,
Pubmed
Olsen,
International Union of Pharmacology. LXX. Subtypes of gamma-aminobutyric acid(A) receptors: classification on the basis of subunit composition, pharmacology, and function. Update.
2008,
Pubmed
Petroski,
Indiplon is a high-affinity positive allosteric modulator with selectivity for alpha1 subunit-containing GABAA receptors.
2006,
Pubmed
Pirker,
GABA(A) receptors: immunocytochemical distribution of 13 subunits in the adult rat brain.
2000,
Pubmed
Puia,
Influence of recombinant gamma-aminobutyric acid-A receptor subunit composition on the action of allosteric modulators of gamma-aminobutyric acid-gated Cl- currents.
1991,
Pubmed
Quirk,
gamma-Aminobutyric acid type A receptors in the rat brain can contain both gamma 2 and gamma 3 subunits, but gamma 1 does not exist in combination with another gamma subunit.
1994,
Pubmed
Ramerstorfer,
The point mutation gamma 2F77I changes the potency and efficacy of benzodiazepine site ligands in different GABAA receptor subtypes.
2010,
Pubmed
Sanna,
Comparison of the effects of zaleplon, zolpidem, and triazolam at various GABA(A) receptor subtypes.
2002,
Pubmed
,
Xenbase
Saper,
The sleep switch: hypothalamic control of sleep and wakefulness.
2001,
Pubmed
Sieghart,
Subunit composition, distribution and function of GABA(A) receptor subtypes.
2002,
Pubmed
Sieghart,
Allosteric modulation of GABAA receptors via multiple drug-binding sites.
2015,
Pubmed
Sieghart,
International Union of Basic and Clinical Pharmacology. CVI: GABAA Receptor Subtype- and Function-selective Ligands: Key Issues in Translation to Humans.
2018,
Pubmed
Sieghart,
Structure and pharmacology of gamma-aminobutyric acidA receptor subtypes.
1995,
Pubmed
Sigel,
The benzodiazepine binding site of GABAA receptors.
1997,
Pubmed
Sigel,
Impact of subunit positioning on GABAA receptor function.
2006,
Pubmed
Tögel,
gamma-Aminobutyric acidA receptors displaying association of gamma 3-subunits with beta 2/3 and different alpha-subunits exhibit unique pharmacological properties.
1994,
Pubmed
Uygun,
Bottom-Up versus Top-Down Induction of Sleep by Zolpidem Acting on Histaminergic and Neocortex Neurons.
2016,
Pubmed
Wafford,
Functional comparison of the role of gamma subunits in recombinant human gamma-aminobutyric acidA/benzodiazepine receptors.
1993,
Pubmed
,
Xenbase
Walters,
Benzodiazepines act on GABAA receptors via two distinct and separable mechanisms.
2000,
Pubmed
,
Xenbase
Wieland,
A single histidine in GABAA receptors is essential for benzodiazepine agonist binding.
1992,
Pubmed
Wingrove,
Key amino acids in the gamma subunit of the gamma-aminobutyric acidA receptor that determine ligand binding and modulation at the benzodiazepine site.
1997,
Pubmed
,
Xenbase
Wulff,
From synapse to behavior: rapid modulation of defined neuronal types with engineered GABAA receptors.
2007,
Pubmed
Xi,
Effects of eszopiclone and zolpidem on sleep and waking states in the adult guinea pig.
2008,
Pubmed
Zhu,
Structure of a human synaptic GABAA receptor.
2018,
Pubmed
