1
|
Effects of bilobalide, ginkgolide B and picrotoxinin on GABA A receptor modulation by structurally diverse positive modulators. Eur J Pharmacol 2017; 806:83-90. [PMID: 28416372 DOI: 10.1016/j.ejphar.2017.04.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 04/11/2017] [Accepted: 04/13/2017] [Indexed: 12/20/2022]
Abstract
Anxiolytics and anticonvulsants generally positively modulate the action of GABA, whereas many convulsants (including the chloride channel blocker picrotoxinin) negatively modulate the action of GABA on GABAA receptors. Like picrotoxinin, bilobalide and ginkgolide B, active constituents of Ginkgo biloba, have been shown to negatively modulate the action of GABA at α1β2γ2L GABAA receptors. However, unlike picrotoxinin, bilobalide and ginkgolide B are not known to cause convulsions. We have assessed the action of bilobalide, ginkgolide B and picrotoxinin on a range of GABAA modulators (etomidate, loreclezole, propofol, thiopentone sodium, diazepam, and allopregnanolone), using two-electrode voltage clamp electrophysiology at recombinant α1β2γ2L GABAA receptors expressed in Xenopus oocytes. The results indicate that bilobalide and ginkgolide B differ from picrotoxinin in their ability to inhibit the actions of a range of these structurally diverse GABAA positive modulators consistent with these modulators acting on a multiplicity of active sites associated with GABAA receptors. In the presence GABA, ginkgolide B was more potent than bilobalide in inhibiting the GABA-potentiating effect of propofol, equipotent against loreclezole and allopregnanolone, and less potent against etomidate, diazepam, and thiopentone sodium. This indicates that in comparison to picrotoxinin, bilobalide and ginkgolide B differ in their effects on the different modulators.
Collapse
|
2
|
Hammer H, Bader BM, Ehnert C, Bundgaard C, Bunch L, Hoestgaard-Jensen K, Schroeder OHU, Bastlund JF, Gramowski-Voß A, Jensen AA. A Multifaceted GABAA Receptor Modulator: Functional Properties and Mechanism of Action of the Sedative-Hypnotic and Recreational Drug Methaqualone (Quaalude). Mol Pharmacol 2015; 88:401-20. [PMID: 26056160 DOI: 10.1124/mol.115.099291] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Accepted: 06/08/2015] [Indexed: 01/09/2023] Open
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.
Collapse
Affiliation(s)
- Harriet Hammer
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Benjamin M Bader
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Corina Ehnert
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Christoffer Bundgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Lennart Bunch
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Kirsten Hoestgaard-Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Olaf H-U Schroeder
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Jesper F Bastlund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Alexandra Gramowski-Voß
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| |
Collapse
|
4
|
Luszczki JJ, Ratnaraj N, Patsalos PN, Czuczwar SJ. Isobolographic analysis of interactions between loreclezole and conventional antiepileptic drugs in the mouse maximal electroshock-induced seizure model. Naunyn Schmiedebergs Arch Pharmacol 2006; 373:169-81. [PMID: 16604339 DOI: 10.1007/s00210-006-0055-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 02/22/2006] [Indexed: 11/26/2022]
Abstract
This study examined the interaction characteristics between loreclezole (LCZ) and various conventional antiepileptic drugs (phenytoin--PHT, carbamazepine--CBZ, valproate--VPA and phenobarbital--PB) in the mouse maximal electroshock (MES)-induced seizure model using isobolographic analysis. Drug-related adverse effects were ascertained by use of the chimney test (motor impairment) and the step-through passive avoidance task (learning and retrieval). It was observed that the combination of LCZ with VPA or PB, at the fixed ratio of 1:1, was supra-additive (synergistic) and the combination of LCZ with CBZ, at all fixed ratios tested (1:3, 1:1 and 3:1), was supra-additive against electroconvulsions. The remaining combinations evaluated, i.e., LCZ with PB or VPA at fixed ratios of 1:3 and 3:1, as well as all fixed-ratio combinations between LCZ and PHT, were additive in the MES test in mice. Pharmacokinetic characterization revealed that LCZ significantly increased both free plasma and brain concentrations of CBZ and PHT, but was without effect on PB. Moreover, a bi-directional pharmacokinetic interaction between LCZ and VPA was observed in that while LCZ increased free plasma, but not total brain VPA concentrations, VPA increased the total brain, but not free plasma LCZ concentrations. Adverse-effect testing revealed that for all antiepileptic drug combinations neither motor performance nor long-term memory was altered. Of the drug combinations investigated, only that of LCZ and PB at the fixed ratio of 1:1 was not associated with any pharmacokinetic interactions, and thus it may be concluded that the supra-additive (synergistic) isobolographic interaction was pharmacodynamic in nature. Furthermore, the fact that LCZ and PB have similar mechanisms of action would suggest that drugs with similar mechanisms of action may provide rational polytherapy regimens.
Collapse
Affiliation(s)
- Jarogniew J Luszczki
- Department of Pathophysiology, Medical University of Lublin, Jaczewskiego 8, 20-090, Lublin, Poland.
| | | | | | | |
Collapse
|
6
|
Abuhamdah S, Fürstner A, Lees G, Chazot PL. Radioligand binding studies of caloporoside and novel congeners with contrasting effects upon [35S] TBPS binding to the mammalian GABAA receptor. Biochem Pharmacol 2005; 70:1382-8. [PMID: 16168965 DOI: 10.1016/j.bcp.2005.07.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2005] [Revised: 07/25/2005] [Accepted: 07/26/2005] [Indexed: 11/21/2022]
Abstract
Caloporoside is a natural active fungal metabolite, which was isolated from Caloporous dichrous and was described to exhibit antibacterial, antifungal and phospholipase C inhibitory activity. We have previously reported evidence that related beta-linked compounds, lactose and octyl-beta-d-mannoside, bind and functionally modulate rodent GABA(A) receptors, respectively. We have characterized the binding pharmacology of synthetic caloporoside and two further congeners, 2-hydroxy-6-([(16R)-(beta-d-mannopyranosyloxy)heptadecyl]) benzoic acid and octyl-beta-d-glucoside on GABA(A) receptors using a [35S]-t-butylbicyclophosphoorothionate (TBPS) radioligand binding assay. Caloporoside and 2-hydroxy-6-([(16R)-(beta-d-mannopyranosyloxy)heptadecyl]) benzoic acid produced concentration-dependent complete inhibition of specific [35S] TBPS binding with overall apparent IC50 values of 14.7+/-0.1 and 14.2+/-0.1 microM, respectively. In contrast, octyl-beta-d-glucoside elicited a concentration-dependent stimulation of specific [35S] TBPS binding (E(max)=144+/-4%; EC50=39.2+/-22.7 nM). The level of stimulation was similar to that elicited by diazepam (E(max)=147+/-6%; EC50=0.8+/-0.1 nM), and was occluded by GABA (0.3 microM). However, the three test compounds failed to elicit any significant effect (positive or negative) upon [3H] flunitrazepam or [3H] muscimol binding, indicating that they did not bind directly, or allosterically couple, to the benzodiazepine or agonist binding site of the GABA(A) receptor, respectively. The constituent monosaccharide, glucose, and both the closely related congeners octyl-beta-d-glucoside or hexyl-beta-d-glucoside have no significant effect upon [35S] TBPS binding. These data, together, provide strong evidence that a beta-glycosidic linkage and chain length are crucial for the positive modulation of [35S] TBPS binding to the GABA(A) receptor by this novel chemical class.
Collapse
Affiliation(s)
- S Abuhamdah
- School of Biological and Biomedical Sciences, Science Park, South Road, Durham University, Durham DH1 3LE, UK
| | | | | | | |
Collapse
|
8
|
Rezai N, Duggan C, Cairns D, Lees G, Chazot PL. Modulation of [3H] TBOB binding to the rodent GABAA receptor by simple disaccharides. Biochem Pharmacol 2003; 65:619-23. [PMID: 12566090 DOI: 10.1016/s0006-2952(02)01611-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We have recently reported evidence that a simple beta-linked alkylated mannose reversibly increased the magnitude of GABA(A) receptor currents evoked in cultured rat pyramidal neurons whilst concomitantly reducing the incidence of spontaneous synaptic activity. In this present study, the effects of the simple beta-linked disaccharide, lactose was investigated using a [3H] TBOB (t-[3H] butylbicycloorthobenzoate) binding assay in adult rat forebrain and cerebellum membranes. Lactose elicited a significant potentiation of [3H] TBOB binding to well-washed forebrain and cerebellar membranes (mean E(max) values=367 and 287%; mean EC(50) values=1.5 and 30 microM, respectively, N=4). The alpha-linked disaccharides, maltose and sucrose also potentiated [3H] TBOB binding, but with 100-600-fold higher EC(50) values than lactose. The lactose-mediated potentiation of [3H] TBOB in the forebrain and cerebellum was completely abolished in the presence of 0.3 microM GABA. Over the concentration range in which significant potentiation of [3H] TBOB binding was detected, lactose elicited no significant effect upon [3H] flunitrazepam binding. This study demonstrated that lactose can modulate the GABA(A) receptor channel, allosterically coupled to the agonist site, but independent of the benzodiazepine site. Furthermore, lactose displayed differential effects upon forebrain and cerebellar GABA(A) receptors indicating that it may be a novel subtype selective agent.
Collapse
Affiliation(s)
- N Rezai
- Institute of Pharmacy, Chemistry and Biomedical Sciences, School of Health, Natural and Social Sciences, University of Sunderland, Sunderland SR1 3SD, Tyne and Wear, UK
| | | | | | | | | |
Collapse
|
12
|
Sanna E, Murgia A, Casula A, Usala M, Maciocco E, Tuligi G, Biggio G. Direct activation of GABAA receptors by loreclezole, an anticonvulsant drug with selectivity for the beta-subunit. Neuropharmacology 1996; 35:1753-60. [PMID: 9076754 DOI: 10.1016/s0028-3908(96)00138-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Loreclezole, an anticonvulsant and antiepileptic compound, potentiates gamma-aminobutyric acid (GABA) type A receptor function, by interacting with a specific allosteric modulatory site on receptor beta-subunits. A similar selectivity for GABAA receptor beta-subunits is apparent for the direct activation of receptor-operated Cl- channels, by the general anesthetics propofol and pentobarbital. The ability of loreclezole to activate GABAA receptors directly has now been compared, biochemically and electrophysiologically, with that of propofol. In well-washed rat cortical membranes (devoid of endogenous GABA), loreclezole and propofol increased t-[35S]butylbicyclophosphorothionate ([35S]TBPS) binding by up to 28% (at 5 microM) and 80% (at 10 microM), respectively. Higher concentrations (50-100 microM) of both compounds inhibited [35S]TBPS binding with great efficacy, an effect mimicked by GABA. In contrast, the benzodiazepine diazepam increased [35S]TBPS binding, but failed to inhibit this parameter, even at high concentrations. At concentrations of 50-100 microM, loreclezole induced inward Cl- currents in the absence of GABA, in Xenopus oocytes expressing human recombinant GABAA receptors, comprised of alpha 1-, beta 2- and gamma 2S-subunits. At 100 microM, the current evoked by loreclezole was 26% of that induced by 5 microM GABA. The current evoked by 100 microM propofol was 98% of that induced by 5 microM GABA. Currents induced by loreclezole, like those evoked by propofol, were potentiated by diazepam in a flumazenil-sensitive manner and blocked by either bicuculline or picrotoxin. These data suggest that loreclezole shares, with propofol, an agonistic action at GABAA receptors containing the beta 2-subunit and that the different efficacies of the two compounds in this regard, may underlie the difference in their pharmacological profiles. The failure of loreclezole to activate GABAA receptors containing the beta 1-subunit may be responsible for its lack of hypnotic effect.
Collapse
Affiliation(s)
- E Sanna
- Department of Experimental Biology Bernardo Loddo, University of Cagliari Via Palabanda, Italy
| | | | | | | | | | | | | |
Collapse
|