Movatterモバイル変換

[0]ホーム
URL:

Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
Thehttps:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

NIH NLM Logo
Log inShow account info
Access keysNCBI HomepageMyNCBI HomepageMain ContentMain Navigation
pubmed logo
Advanced Clipboard
User Guide

Full text links

Elsevier Science full text link Elsevier Science Free PMC article
Full text links

Actions

Share

.2015 Aug;88(2):401-20.
doi: 10.1124/mol.115.099291. Epub 2015 Jun 8.

A Multifaceted GABAA Receptor Modulator: Functional Properties and Mechanism of Action of the Sedative-Hypnotic and Recreational Drug Methaqualone (Quaalude)

Affiliations

A Multifaceted GABAA Receptor Modulator: Functional Properties and Mechanism of Action of the Sedative-Hypnotic and Recreational Drug Methaqualone (Quaalude)

Harriet Hammer et al. Mol Pharmacol.2015 Aug.

Abstract

In the present study, we have elucidated the functional characteristics and mechanism of action of methaqualone (2-methyl-3-o-tolyl-4(3H)-quinazolinone, Quaalude), an infamous sedative-hypnotic and recreational drug from the 1960s-1970s. Methaqualone was demonstrated to be a positive allosteric modulator at human α1,2,3,5β2,3γ2S GABAA receptors (GABAARs) expressed in Xenopus oocytes, whereas it displayed highly diverse functionalities at the α4,6β1,2,3δ GABAAR subtypes, ranging from inactivity (α4β1δ), through negative (α6β1δ) or positive allosteric modulation (α4β2δ, α6β2,3δ), to superagonism (α4β3δ). Methaqualone did not interact with the benzodiazepine, barbiturate, or neurosteroid binding sites in the GABAAR. Instead, the compound is proposed to act through the transmembrane β((+))/α((-)) subunit interface of the receptor, possibly targeting a site overlapping with that of the general anesthetic etomidate. The negligible activities displayed by methaqualone at numerous neurotransmitter receptors and transporters in an elaborate screening for additional putative central nervous system (CNS) targets suggest that it is a selective GABAAR modulator. The mode of action of methaqualone was further investigated in multichannel recordings from primary frontal cortex networks, where the overall activity changes induced by the compound at 1-100 μM concentrations were quite similar to those mediated by other CNS depressants. Finally, the free methaqualone concentrations in the mouse brain arising from doses producing significant in vivo effects in assays for locomotion and anticonvulsant activity correlated fairly well with its potencies as a modulator at the recombinant GABAARs. Hence, we propose that the multifaceted functional properties exhibited by methaqualone at GABAARs give rise to its effects as a therapeutic and recreational drug.

Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

PubMed Disclaimer

Figures

Fig. 1.
Fig. 1.
Functional properties of methaqualone at human GABAARs expressed inXenopus oocytes. (A) Chemical structure of methaqualone. (B) Concentration-response curves for methaqualone atα1β2γ2S,α2β2γ2S,α3β2γ2S,α4β2δ,α5β2γ2S, andα6β2δ GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 5–9). (C) Representative traces for various concentrations of methaqualone coapplied with GABA EC10 atα1β2γ2S (left) andα6β2δ (right) GABAARs. The application bars in gray for the various methaqualone concentrations all represent a 30-second preincubation with methaqualone followed by coapplication of methaqualone and GABA EC10. The black application bars represent application of GABA EC10 and the GABA concentration eliciting the maximal response. (D) Concentration-response curves for methaqualone atα1β2γ2S andα6β2δ GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 5–6). (E) Concentration-response curves for GABA at theα1β2γ2S GABAAR in the absence or presence of 3µM diazepam or 300µM methaqualone (means ± S.E.M.;n = 4–6).
Fig. 2.
Fig. 2.
Functional properties of methaqualone at human GABAARs expressed inXenopus oocytes. (A) Concentration-response curves for methaqualone atα1β2,α1β2γ2S, andα1β3γ2S GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 6–7). (B) Modulation ofα4β1δ GABAAR signaling exerted by methaqualone in the presence of GABA EC10 or GABA EC70 (means ± S.E.M.;n = 4–8). (C) Representative trace and the concentration-response curve for methaqualone as an agonist at theα4β3δ GABAAR (means ± S.E.M.;n = 6). The gray application bars above the trace indicate application of the various methaqualone concentrations, and the black bar represents the application of a GABA concentration eliciting a maximal response. (D, left) Concentration-response curves for methaqualone atα6β2,α6β1δ,α6β2δ, andα6β3δ GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 4–8). (D, right) Concentration-inhibition curve for methaqualone at theα6β1δ GABAAR in the presence of GABA EC70 (means ± S.E.M.;n = 5). The hatched concentration-response curves forα1β2γ2S andα6β2δ in (A) and (D), respectively, are based on data displayed in Fig. 1B.
Fig. 3.
Fig. 3.
The potential interaction of methaqualone with three known allosteric sites in the GABAAR complex. The experiments were performed at human WT and mutantα1β2γ2S GABAARs expressed inXenopus oocytes. (A) Effects of 10μM flumazenil on the potentiation exerted by 3μM diazepam or 300μM methaqualone on the responses evoked by GABA EC10 through theα1β2γ2S GABAAR. Asterisks indicate significant differences between responses evoked by GABA EC10 in the presence of modulator (diazepam and methaqualone) and by GABA EC10 alone, either in the absence or presence of flumazenil: ****P < 0.0001 (means ± S.E.M.;n = 6–13). (B) The modulatory effects of 3μM diazepam and 300μM methaqualone on the GABA EC10-evoked responses throughα1β2γ2S andα1H102Rβ2γ2S GABAARs. Asterisks indicate significant differences between responses evoked by GABA EC10 in the presence of modulator and by GABA EC10 alone at the same receptor (means ± S.E.M.;n = 5–12): ***P < 0.001; ****P < 0.0001. (C) Direct activation of theα1β2γ2S GABAAR evoked by 300μM methaqualone, by 300µM pentobarbital, and by coapplication of 300μM methaqualone and 300µM pentobarbital (means ± S.E.M.;n = 7). Asterisks indicate the significant difference between the responses evoked by 300µM pentobarbital and by coapplication of 300µM methaqualone and 300µM pentobarbital: ****P < 0.0001. Insert: Representative trace for direct activation of theα1β2γ2S GABAAR by 300μM methaqualone, 300µM pentobarbital, and coapplication of 300μM methaqualone and 300µM pentobarbital. (D) The modulatory effects of 10μM allopregnanolone and 300μM methaqualone on the GABA EC10-evoked responses throughα1β2γ2S,α1T237Iβ2γ2S, andα1Q241Wβ2γ2S GABAARs. Asterisks indicate significant differences between responses evoked by GABA EC10 in the presence of modulator and by GABA EC10 alone at the same receptor (means ± S.E.M.;n = 4–11): ****P < 0.0001.
Fig. 4.
Fig. 4.
The potential interaction of methaqualone with the transmembraneβ(+)/α(–) subunit interface in the GABAAR complex. The experiments were performed at human WT and mutant GABAARs expressed inXenopus oocytes. (A) Modulatory effects of 100μM etomidate and 300μM methaqualone on the responses evoked by GABA EC10 throughα1β2γ2S orα1β2N265Mγ2S GABAARs (means ± S.E.M.;n = 3–14). Asterisks indicate significant differences between the responses evoked by GABA EC10 in the presence of modulator and by GABA EC10 alone at the same receptor: ****P < 0.0001. (B) Concentration-response curves for methaqualone atα6β2δ andα6β2S265Nδ GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 5). (C, left) Concentration-response curves for methaqualone atα6β2δ andα6β2N265Sδ GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 3–8). (C, right) Concentration-inhibition curves for methaqualone atα6β1δ andα6β2N265Sδ GABAARs in the presence of GABA EC60-70 (means ± S.E.M.;n = 5–7). (D, left) Direct activation ofα1β2γ2S andα1β2M236Wγ2S GABAAR signaling evoked by 100μM etomidate and 300μM methaqualone (means ± S.E.M.;n = 4–8). Asterisks indicate significant differences between the responses evoked by etomidate or methaqualone at the two receptors: ****P < 0.0001 (unpaired two-sidedt test). (D, right) Concentration-response curve for methaqualone as an agonist at theα1β2M236Wγ2S GABAAR (mean ± S.E.M.;n = 4). (E, left) Modulatory effects of 100μM etomidate and 300μM methaqualone on the responses evoked by GABA EC10 atα1β2γ2S andα1β2M286Wγ2S GABAARs (means ± S.E.M.;n = 3–10). Asterisks indicate significant differences between the responses evoked by GABA EC10 in the presence of modulator and by GABA EC10 alone at the same receptor: ****P < 0.0001; ***P < 0.001. (E, right) Concentration-response curves for methaqualone atα1β2γ2S andα1β2M286Wγ2S GABAARs in the presence of GABA EC10 (means ± S.E.M.;n = 5–7). The hatched concentration-response curves forα6β1δ (B)α6β2δ (C) andα1β2γ2S (E) are based on data in Figs. 2D, 1B, and 1B, respectively.
Fig. 5.
Fig. 5.
Functional properties of 100μM etomidate at humanα4βδ GABAARs expressed inXenopus oocytes. The modulation exerted by etomidate and methaqualone was determined at the sameα4β1δ-,α4β2δ-, orα4β3δ-expressing oocytes. (A) Modulatory effects of 100μM etomidate and 300μM methaqualone on the responses evoked by GABA EC10 throughα4β1δ orα4β2δ GABAARs. Responses given as means ± S.E.M. in the percentage ofRmax of GABA; etomidate: 118 ± 9% (α4β1δ;n = 6) and 195 ± 23% (α4β2δ,n = 4); methaqualone: 16% ± 1.7 (α4β1δ;n = 6) and 154 ± 11% (α4β2δ,N = 4). ****P < 0.0001. (B) Direct activation of theα4β3δ GABAAR by 100μM etomidate or 300μM methaqualone. Responses given as means ± S.E.M. in percentage ofRmax of GABA; etomidate: 410 ± 88%;n = 6; methaqualone: 437 ± 74%;n = 6.
Fig. 6.
Fig. 6.
The putative shared binding mode of etomidate, loreclezole, and methaqualone. (A) Illustration of the structural similarities between etomidate (left), loreclezole (middle), and methaqualone (right). The putative pockets P1 and P2 are given in blue, and the hydrogen bond acceptors in the compounds are indicated with red arrows. (B) Superimposition of low-energy conformations of etomidate (type code), loreclezole (pink), and methaqualone (green) by fitting the carbonyl groups of etomidate and methaqualone and the vinylogous chlorine of loreclezole.
Fig. 7.
Fig. 7.
Multiparametric analysis of cortical neuron network activity. Top panels: Representative spike raster plots of native cortical activity and cortical activity after acute treatment with 100µM methaqualone. Reduction of overall spiking and bursting activity, as well as reduction of burst strength is observed (higher magnification). Bottom panel: Scheme of two simplified bursts outlining some of the parameters that can be extracted from the recordings. Parameters describing general activity [burst inter burst interval (IBI) and burst period] and burst structure [burst duration, burst plateau, burst amplitude, burst inter spike interval (ISI) and burst area] are indicated. Standard deviations of these parameters such as S.D. of burst rate and S.D. of burst duration are measures for regularity of general activity and burst structure, respectively.
Fig. 8.
Fig. 8.
Summary of the changes induced by methaqualone, DS2, diazepam, phenobarbital, and etomidate on cortical network activity in vitro. The heat maps present the significant changes in 60 activity-describing parameters from four defined categories arising from eight or nine cumulatively increasing concentrations of the five modulators (concentrations are given in molar). The colors encode statistically significant modulator-induced changes (increases or decreases) in parameters relative to native activity (no drug, 100%).
Fig. 9.
Fig. 9.
Selected functional effects of methaqualone, DS2, etomidate, phenobarbital, and diazepam on cortical network activity in vitro. The effects of eight or nine cumulatively increasing concentrations of methaqualone (black square, blue line), DS2 (gray triangle, gray line), phenobarbital (black circle, black line), diazepam (open circle, green line), and etomidate (black diamond, red line) at 16 activity-describing parameters from four defined categories. Data are given as mean ± S.E.M. relative to native activity (no drug, 100%).
Fig. 10.
Fig. 10.
Similarity analysis of the effects of methaqualone at cortical network activity. Top 10 ranks of the most phenotypically similar functional profiles of 69 reference compounds from the NeuroProof database (listed in Table 3) ranked based on the similarity score for methaqualone at concentrations ranging from 1 to 100µM. Data for the methaqualone concentrations 1, 10, and 100 nM are given in shaded colors. The concentration-response profiles of the 69 reference compounds were used for training the classifier, and the methaqualone data sets were classified per concentration (10 per concentration). Table values correspond to similarity score per concentration (e.g., at 100µM methaqualone, 8% of its data sets were classified as etomidate, 4% as diazepam, 12% as chlorpromazine, and so forth). High values reflect high functional phenotypic similarity between reference compound effects and methaqualone effects.
Fig. 11.
Fig. 11.
Sedative or ataxic effects and anticonvulsant efficacy of methaqualone (A) and diazepam (B) in beam walk and MEST assays in mice. Data are given as average slips and falls (mean ± S.E.M.) and by the average current threshold (mean ± S.E.M.), respectively. *P < 0.05 analysis of variance and post hoc Dunnett’s test. HPBc; hydroxypropyl-β-cyclodextrin
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Bali M, Akabas MH. (2004) Defining the propofol binding site location on the GABAA receptor. Mol Pharmacol 65:68–76. - PubMed
    1. Barcelo R. (1961) A clinical study of methaqualone: a new nonbarbiturate hypnotic. Can Med Assoc J 85:1304–1305. - PMC - PubMed
    1. Barceloux DG (2012) Methaqualone and related compounds, in Medical Toxicology of Drug Abuse, pp 504–513, John Wiley & Sons, Inc., New York.
    1. Belelli D, Harrison NL, Maguire J, Macdonald RL, Walker MC, Cope DW. (2009) Extrasynaptic GABAA receptors: form, pharmacology, and function. J Neurosci 29:12757–12763. - PMC - PubMed
    1. Belelli D, Lambert JJ, Peters JA, Wafford K, Whiting PJ. (1997) The interaction of the general anesthetic etomidate with the γ-aminobutyric acid type A receptor is influenced by a single amino acid. Proc Natl Acad Sci USA 94:11031–11036. - PMC - PubMed

Publication types

MeSH terms

Substances

Related information

LinkOut - more resources

Full text links
Elsevier Science full text link Elsevier Science Free PMC article
Cite
Send To

NCBI Literature Resources

MeSHPMCBookshelfDisclaimer

The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Unauthorized use of these marks is strictly prohibited.

[8]ページ先頭
©2009-2025 Movatter.jp