3-Heteroaryl-2-pyridones: benzodiazepine site ligands with functional delectivity for alpha 2/alpha 3-subtypes of human GABA(A) receptor-ion channels

Symptomatic and neurotrophic effects of GABAA receptor positive allosteric modulation in a mouse model of chronic stress

Chronic stress is a risk factor for Major Depressive Disorder (MDD), and in rodents, it recapitulates human behavioral, cellular and molecular changes. In MDD and after chronic stress, neuronal dysfunctions and deficits in GABAergic signaling are observed and responsible for symptom severity. GABA signals predominantly through GABAA receptors (GABAA-R) composed of various subunit types that relate to downstream outcomes. Activity at α2-GABAA-Rs contributes to anxiolytic properties, α5-GABAA-Rs to cognitive functions, and α1-GABAA-Rs to sedation. Therefore, a therapy aiming at increasing α2- and α5-GABAA-Rs activity, but devoid of α1-GABAA-R activity, has potential to address several symptomologies of depression while avoiding side-effects. This study investigated the activity profiles and behavioral efficacy of two enantiomers of each other (GL-II-73 and GL-I-54), separately and as a racemic mixture (GL-RM), and potential disease-modifying effects on neuronal morphology. Results confirm GL-I-54 and GL-II-73 exert positive allosteric modulation at the α2-, α3-, α5-GABAA-Rs and α5-containing GABAA-Rs, respectively, and separately reduces immobility in the forced swim test and improves stress-induced spatial working memory deficits. Using unpredictable chronic mild stress (UCMS), we show that acute and chronic administration of GL-RM provide pro-cognitive effects, with mild efficacy on mood symptoms, although at lower doses avoiding sedation. Morphology studies showed reversal of spine density loss caused by UCMS after chronic GL-RM treatment at apical and basal dendrites of the PFC and CA1. Together, these results support using a racemic mixture with combined α2-, α3-, α5-GABAA-R profile to reverse chronic stress-induced mood symptoms, cognitive deficits, and with anti-stress neurotrophic effects.

Recent advances of heterocycle based anticancer hybrids

Cancer is one of the major causes of death across the world. Cancer is a broad word that encompasses a wide range of illnesses that can affect any part of the body. Cancer research has increased understanding of molecular biology and cellular biology, resulting in new cancer therapies. Despite of adverse effects, surgery, radiation, and anticancer medicines are the modern cancer treatments. Keeping in mind the excellent anticancer activity exhibited by various heterocyclics, various medicines with heterocyclic moiety have been developed to identify particular target regions. The chapter aims to discuss new discoveries in the field of anticancer pharmaceuticals comprising the thiazole, pyrazole, oxazole, and triazole rings over the last five years. The proposed anticancer drugs have a lot of future significance due to their high potency.

Synthesis of Functionalized Bicyclic Pyridones Containing the Dithiocarbamate Group Using Thioazlactones, Diamines, and Nitroketene Dithioacetal

An efficient method for the synthesis of highly substituted bicyclic pyridone derivatives containing the dithiocarbamate group is reported via a one-pot three-component reaction of 2-(alkylthio)thio­azlactones, diamines, and nitroketene dithioacetal in EtOH under catalyst-free conditions. The reaction proceeds via a domino amidation–­intramolecular 1,4-addition-type Friedel–Crafts alkylation reaction to afford the corresponding fused bicyclic pyridones with high yields and diastereoselectivity.

Photoinduced direct hydration of dipyridylacetylenes in acidic aqueous solution

The straightforward and catalyst-free photoinduced hydration reaction of dipyridylacetylenes in acidic aqueous solution was achieved upon UV irradiation at room temperature.

Sequence- And Structure-Specific Probing of RNAs by Short Nucleobase-Modified dsRNA-Binding PNAs Incorporating a Fluorescent Light-up Uracil Analog

RNAs are emerging as important biomarkers and therapeutic targets. The strategy of directly targeting double-stranded RNA (dsRNA) by triplex-formation is relatively underexplored mainly due to the weak binding at physiological conditions for the traditional triplex-forming oligonucleotides (TFOs). Compared to DNA and RNA, peptide nucleic acids (PNAs) are chemically stable and have a neutral peptide-like backbone, and thus, they show significantly enhanced binding to natural nucleic acids. We have successfully developed nucleobase-modified dsRNA-binding PNAs (dbPNAs) to facilitate structure-specific and selective recognition of dsRNA over single-stranded RNA (ssRNA) and dsDNA regions at near-physiological conditions. The triplex formation strategy facilitates the targeting of not only the sequence but also the secondary structure of RNA. Here, we report the development of novel dbPNA-based fluorescent light-up probes through the incorporation of A-U pair-recognizing 5-benzothiophene uracil (^btU). The incorporation of ^btU into dbPNAs does not affect the binding affinity toward dsRNAs significantly, in most cases, as evidenced by our nondenaturing gel shift assay data. The blue fluorescence emission intensity of ^btU-modified dbPNAs is sequence- and structure-specifically enhanced by dsRNAs, including the influenza viral RNA panhandle duplex and HIV-1-1 ribosomal frameshift-inducing RNA hairpin, but not ssRNAs or DNAs, at 200 mM NaCl, pH 7.5. Thus, dbPNAs incorporating ^btU-modified and other further modified fluorescent nucleobases will be useful biochemical tools for probing and detecting RNA structures, interactions, and functions.

General Recognition of U-G, U-A, and C-G Pairs by Double-Stranded RNA-Binding PNAs Incorporated with an Artificial Nucleobase

Chemically modified peptide nucleic acids (PNAs) show great promise in the recognition of RNA duplexes by major-groove PNA·RNA-RNA triplex formation. Triplex formation is favored for RNA duplexes with a purine tract within one of the RNA duplex strands, and is severely destabilized if the purine tract is interrupted by pyrimidine residues. Here, we report the synthesis of a PNA monomer incorporated with an artificial nucleobase S, followed by the binding studies of a series of S-modified PNAs. Our data suggest that an S residue incorporated into short 8-mer dsRNA-binding PNAs (dbPNAs) can recognize internal Watson-Crick C-G and U-A, and wobble U-G base pairs (but not G-C, A-U, and G-U pairs) in RNA duplexes. The short S-modified PNAs show no appreciable binding to DNA duplexes or single-stranded RNAs. Interestingly, replacement of the C residue in an S·C-G triple with a 5-methyl C results in the disruption of the triplex, probably due to a steric clash between S and 5-methyl C. Previously reported PNA E base shows recognition of U-A and A-U pairs, but not a U-G pair. Thus, S-modified dbPNAs may be uniquely useful for the general recognition of RNA U-G, U-A, and C-G pairs. Shortening the succinyl linker of our PNA S monomer by one carbon atom to have a malonyl linker causes a severe destabilization of triplex formation. Our experimental and modeling data indicate that part of the succinyl moiety in a PNA S monomer may serve to expand the S base forming stacking interactions with adjacent PNA bases.

Medicinal chemistry of vicinal diaryl scaffold: A mini review

The privileged structures have been widely used as a valuable template in new drug discovery. 1,2-Diaryl or vicinal diaryl is a simple scaffold found in many drugs and naturally occurring compounds. From synthetic point of view, the vicinal diaryl derivatives are easily accessible due to their facile and expedient syntheses. These scaffolds have shown numerous interesting pharmacological activities against various diseases with lot of clinical potentials. This review aims to highlight the evidence of vicinal diaryl motif as a privileged scaffold in COX-2 inhibitors and CA-4 analogs.

Facile one-pot four-component synthesis of 3,4-dihydro-2-pyridone derivatives: novel urease inhibitor scaffold

In the current study, a series of 3,4-dihydro-2-pyridone derivatives were synthesized in a one-pot fourcomponent reaction of Meldrum's acid, benzaldehyde derivatives, methyl acetoacetate, and ammonium acetate. SiO2-Pr-SO3H was used as an efficient catalyst for the synthesis of the target compounds under solvent-free conditions. The most probable mechanism for this reaction has been discussed. The advantages of this methodology are high product yields, being environmentally benign, short reaction times, and easy handling. Eight 2-pyridinone derivatives were evaluated for their inhibitory activities against Jack bean urease. Molecular docking study of the synthesized compounds was also evaluated. All compounds showed good activities against urease and among them, 4-(4-nitrophenyl)-5-methoxycarbonyl-6-methyl-3,4-dihydropyridone (5a) showed the most potent activity (IC₅₀ = 29.12 µM), more potent than hydroxyurea as the reference drug (IC₅₀ = 100.0 µM). Also, the results from docking studies were in good agreement with those obtained with in vitro assay. According to the docking studies methionine (Met) 637 and nitro phenyl ring cause n-π interaction between lone pair of sulfur atom and π aromatic ring. Moreover, hydrophobic interactions existed between compound 5a and alanine (ALA) 636, ALA 440, and isoleucine 411. The results indicated that the inhibitory activities increased with the increase of electron withdrawing ability of the groups despite a less important role of lipophilicity in increasing the inhibitory activity.

To what extent is it possible to dissociate the anxiolytic and sedative/hypnotic properties of GABAA receptors modulators?

The relatively common view indicates a possible dissociation between the anxiolytic and sedative/hypnotic properties of benzodiazepines (BZs). Indeed, GABAA receptor (GABAAR) subtypes have specific cerebral distribution in distinct neural circuits. Thus, GABAAR subtype-selective drugs may be expected to perform distinct functions. However, standard behavioral test assays provide limited direction towards highlighting new action mechanisms of ligands targeting GABAARs. Automated behavioral tests, lack sensitivity as some behavioral characteristics or subtle behavioral changes of drug effects or that are not considered in the overall analysis (Ohl et al., 2001) and observation-based analyses are not always performed. In addition, despite the use of genetically engineered mice, any possible dissociation between the anxiolytic and sedative properties of BZs remains controversial. Moreover, the involvement the different subtypes of GABAAR subtypes in the anxious behavior and the mechanism of action of anxiolytic agents remains unclear since there has been little success in the pharmacological investigations so far. This raises the question of the involvement of the different subunits in anxiolytic-like and/or sedative effects; and the actual implication of these subunits, particularly, α-subunits in the modulation of sedation and/or anxiety-related disorders. This present review was prompted by several conflicting studies on the degree of involvement of these subunits in anxiolytic-like and/or sedative effects. To this end, we explored the GABAergic system, particularly, the role of different subunits containing synaptic GABAARs. We report herein the targeting gene encoding the different subunits and their contribution in anxiolytic-like and/or sedative actions, as well as, the mechanism underlying tolerance to BZs.

A highly efficient magnetic solid acid nanocatalyst for the synthesis of new bulky heterocyclic compounds

Fe₃O₄nanoparticles were coated with 3-aminopropyltriethoxysilane and further chemically modified with maleic anhydride to generate Fe₃O₄@APTES·MAH NPs. Then some new bulky heterocyclic compounds were synthesized using this catalyst.

Targeting the modulation of neural circuitry for the treatment of anxiety disorders

Anxiety disorders are a major public health concern. Here, we examine the familiar area of anxiolysis in the context of a systems-level understanding that will hopefully lead to revealing an underlying pharmacological connectome. The introduction of benzodiazepines nearly half a century ago markedly improved the treatment of anxiety disorders. These agents reduce anxiety rapidly by allosterically enhancing the postsynaptic actions of GABA at inhibitory type A GABA receptors but side effects limit their use in chronic anxiety disorders. Selective serotonin reuptake inhibitors and serotonin/norepinephrine reuptake inhibitors have emerged as an effective first-line alternative treatment of such anxiety disorders. However, many individuals are not responsive and side effects can be limiting. Research into a relatively new class of agents known as neurosteroids has revealed novel modulatory sites and mechanisms of action that are providing insights into the pathophysiology of certain anxiety disorders, potentially bridging the gap between the GABAergic and serotonergic circuits underlying anxiety. However, translating the pharmacological activity of compounds targeted to specific receptor subtypes in rodent models of anxiety to effective therapeutics in human anxiety has not been entirely successful. Since modulating any one of several broad classes of receptor targets can produce anxiolysis, we posit that a systems-level discovery platform combined with an individualized medicine approach based on noninvasive brain imaging would substantially advance the development of more effective therapeutics.

Divergent synthesis of 4,6-diarylated pyridin-2(1H)-ones from chalcones: novel access to 2,4,6-triaryl pyridines

A wide range of 4,6-diarylated-2(1H)-one derivatives were synthesized in excellent yields from chalcones in one pot. Further the designed 4,6-diarylated pyridin-2(1H)-one derivatives have been successfully utilized in synthesizing 2,4,6-triarylpyridines.

Thiazole: a promising heterocycle for the development of potent CNS active agents

Thiazole is a valuable scaffold in the field of medicinal chemistry and has accounted to display a variety of biological activities. Thiazole and its derivatives have attracted continuing interest to design various novel CNS active agents. In the past few decades, thiazoles have been widely used to develop a variety of therapeutic agents against numerous CNS targets. Thiazole containing drug molecules are currently being used in treatment of various CNS disorders and a number of thiazole derivatives are also presently in clinical trials. A lot of research has been carried out on thiazole and their analogues, which has proved their efficacy to overcome several CNS disorders in rodent as well as primate models. The aim of present review is to highlights diverse CNS activities displayed by thiazole and their derivatives. SAR of this nucleus has also been well discussed. This review covers the recent updates present in literature and will surely provide a greater insight for the designing and development of potent thiazole based CNS active agents in future.

Novel bisaryl substituted thiazoles and oxazoles as highly potent and selective peroxisome proliferator-activated receptor delta agonists

The discovery, synthesis, and optimization of compound 1 from a high-throughput screening hit to highly potent and selective peroxisome proliferator-activated receptor delta (PPARdelta) agonists are reported. The synthesis and structure-activity relationship in this series are described in detail. On the basis of a general schematic PPAR pharmacophore model, scaffold 1 was divided into headgroup, linker, and tailgroup and successively optimized for PPAR activation using in vitro PPAR transactivation assays. A (2-methylphenoxy)acetic acid headgroup, a flexible linker, and a five-membered heteroaromatic center ring with two hydrophobic aryl substituents were required for efficient and selective PPARdelta activation. The fine-tuning of these aryl substituents led to an array of highly potent and selective compounds such as compound 38c, displaying an excellent pharmacokinetic profile in mouse. In an in vivo acute dosing model, selected members of this array were shown to induce the expression of pyruvate dehydrogenase kinase-4 (PDK4) and uncoupling protein-3 (UCP3), genes that are known to be involved in energy homeostasis and regulated by PPARdelta in skeletal muscle.

Role of GABAA receptors in cognition

Complex brains have developed specialized mechanisms for the grouping of principal cells into temporal coalitions of local or distant networks: the inhibitory interneuron ‘clocking’ networks. They consist of GABAergic (where GABA is γ-aminobutyric acid) interneurons of a rich diversity. In cortical circuits, these neurons control spike timing of the principal cells, sculpt neuronal rhythms, select cell assemblies and implement brain states. On the basis of these considerations, the deficits in cognition, emotion and perception in psychiatric disorders such as anxiety, depression or schizophrenia are considered to manifest themselves through a dysregulation of the inhibitory interneuron ‘clocking’ network as a final common denominator, irrespective of the diverse underlying disease pathologies. The diversity of GABAergic interneurons is paralleled by a corresponding diversity of GABAA receptors in network regulation. The region-, cell- and domain-specific location of these receptor subtypes offers the possibility to gain functional insights into the role of behaviourally relevant neuronal circuits. Using genetic manipulation, the regulation of anxiety behaviour was attributed to neuronal circuits characterized by the expression of α2-GABAA receptors. Neurons expressing α3-GABAA receptors, located mainly in aminergic and basal forebrain cholinergic neurons, were related to a hyperdopaminergic phenotype, typical of schizophrenic symptoms. Temporal and spatial memory were selectively modulated by extrasynaptic α5-GABAA receptors. Chronic pathological pain was under the regulation of spinal and cortical α2- (and α3-) GABAA receptors. Thus the relevance of the diversity of inhibitory GABAA receptor subtypes for the regulation of cognition, emotion and memory is increasingly being recognized. The clinical proof-of-concept of a subtype-specific pharmacology is most advanced for the alleviation of cognitive dysfunctions in schizophrenia, based on the treatment of patients with an α2/α3-GABAA receptor ligand.

Discriminative stimulus effects of L-838,417 (7-tert-butyl-3-(2,5-difluoro-phenyl)-6-(2-methyl-2H-[1,2,4]triazol-3-ylmethoxy)-[1,2,4]triazolo[4,3-b]pyridazine): role of GABA(A) receptor subtypes

Previous reports suggest that gamma-aminobutyric acid type A (GABA(A)) receptors containing alpha1 subunits may play a pivotal role in mediating the discriminative stimulus effects of benzodiazepines (BZs). L-838,417 (7-tert-Butyl-3-(2,5-difluoro-phenyl)-6-(2-methyl-2H-[1,2,4]triazol-3-ylmethoxy)-[1,2,4]triazolo[4,3-b]pyridazine) is a GABA(A) receptor modulator with intrinsic efficacy in vitro at alpha2, alpha3, and alpha5 subunit-containing GABA(A) receptors, and little demonstrable intrinsic efficacy in vitro at alpha1 subunit-containing GABA(A) receptors. The present study evaluated the discriminative stimulus effects of L-838,417 in order to determine the extent to which the alpha2, alpha3, and alpha5 subunit-containing GABA(A) receptors contribute to the interoceptive effects of BZ-type drugs. Squirrel monkeys (Saimiri sciureus) were trained to discriminate L-838,417 (0.3 mg/kg, i.v.) from vehicle under a 5-response fixed-ratio schedule of food reinforcement. Under test conditions, L-838,417 administration resulted in dose-dependent increases in drug-lever responding that were antagonized by the BZ-site antagonist, flumazenil. Administration of non-selective BZs, compounds with 10-fold greater affinity for alpha1 subunit-containing GABA(A) receptors compared to alpha2, alpha3, and alpha5 subunit-containing GABA(A) receptors, barbiturates and ethanol (which modulate the GABA(A) receptor via a non-BZ site), all resulted in a majority of responses on the L-838,417-paired lever (65-100% drug-lever responding). betaCCT, an antagonist that binds with 20-fold greater affinity for alpha1 subunit-containing GABA(A) receptors relative to alpha2, alpha3, and alpha5-containing GABA(A) receptors, had no significant effect on the discriminative stimulus effects of L-838,417 or the L-838,417-like effects of diazepam or zolpidem. These data suggest that efficacy at alpha2, alpha3, and/or alpha5 subunit-containing GABA(A) receptors likely are sufficient for engendering BZ-like discriminative stimulus effects.

Identification of anxiolytic/nonsedative agents among indol-3-ylglyoxylamides acting as functionally selective agonists at the gamma-aminobutyric acid-A (GABAA) alpha2 benzodiazepine receptor

Anxioselective agents may be identified among compounds binding selectively to the alpha(2)beta(x)gamma(2) subtype of the gamma-aminobutyric acid-A (GABA(A))/central benzodiazepine receptor (BzR) complex and behaving as agonists or among compounds binding with comparable potency to various BzR subtypes but eliciting agonism only at the alpha(2)beta(x)gamma(2) receptor. Because of subtle steric differences among BzR subtypes, the latter approach has proved much more successful. A biological screening within the class of indol-3-ylglyoxylamides 1-3 allowed us to identify compounds 1c and 2b as potential anxiolytic/nonsedative agents showing alpha(2) selective efficacy in vitro and anxioselective effects in vivo. According to molecular modeling studies, and consistently with SARs accumulated in the past decade, 5-NO(2)- and 5-H-indole derivatives would preferentially bind to BzR by placing the indole ring in the L(Di) and the L(2) receptor binding sites, respectively.

Glutamatergic and GABAergic modulations of ultrasonic vocalizations during maternal separation distress in mouse pups

INTRODUCTION

Dysregulation of GABAergic inhibition and glutamatergic excitation has been implicated in exaggerated anxiety. Mouse pups emit distress-like ultrasonic vocalizations (USVs) when they are separated from their dam/siblings, and this behavior is reduced by benzodiazepines (BZs) which modulate GABAergic inhibition. The roles of glutamate receptors on USVs remain to be investigated.

MATERIALS AND METHODS

We examined the roles of glutamate receptor subtypes on mouse pup USVs using N-methyl-D: -aspartate (NMDA) receptor antagonists with different affinities [dizocilpine (MK-801), memantine, and neramexane] and group II metabotropic glutamate receptor agonist (LY-379268) and antagonist (LY-341495). These effects were compared with classic BZs: flunitrazepam, bromazepam, and chlordiazepoxide. To assess the role of GABA(A) receptor subunits on USVs, drugs that have preferential actions at different GABA(A)-alpha subunits (L-838417 and QH-ii-066) were tested. Seven-day-old CFW mouse pups were separated from their dam and littermates and placed individually on a 19 degrees C test platform for 4 min. Grid crossings and body rolls were measured in addition to USVs.

RESULTS

Dizocilpine dose-dependently reduced USVs, whereas memantine and neramexane showed biphasic effects and enhanced USVs at low to moderate doses. The NMDA receptor antagonists increased locomotion. LY-379268 reduced USVs but also suppressed locomotion. All BZs reduced USVs and increased motor incoordination. Neither L-838417 nor QH-ii-066 changed USVs, but both induced motor incoordination.

CONCLUSION

Low-affinity NMDA receptor antagonists, but not the high-affinity antagonist, enhanced mouse pup distress calls, which may be reflective of an anxiety-like state. BZs reduced USVs but also induced motor incoordination, possibly mediated by the alpha5 subunit containing GABA(A) receptors.

Contribution of alpha1 subunit-containing gamma-aminobutyric acidA (GABAA) receptors to motor-impairing effects of benzodiazepines in squirrel monkeys

RATIONALE

Benzodiazepines (BZs) are effective anxiolytics and hypnotics, but their use is limited by unwanted side effects, such as motor impairment.

OBJECTIVES

To assess the contribution of alpha1 subunit-containing gamma-aminobutyric acid(A) (GABA(A)) receptor subtypes to the motor-impairing effects of BZs, the present study evaluated two observable measures of motor coordination (balance on a pole, resistance to hind-limb flexion) engendered by nonselective and selective BZ-site agonists in squirrel monkeys.

MATERIALS AND METHODS

Multiple doses of nonselective BZs (triazolam, alprazolam, diazepam, and chlordiazepoxide) and alpha1 subunit-preferring agonists (zolpidem and zaleplon) were administered to adult male squirrel monkeys (N = 4-6), and experimenters rated the monkey's ability to balance on a horizontal pole ("ataxic-like effects"), as well as the degree of resistance to hind-limb flexion ("myorelaxant-like effects").

RESULTS

Administration of all BZ-type drugs resulted in ataxic-like and myorelaxant-like effects. Pretreatment with the alpha1 subunit-preferring antagonist beta-carboline-3-carboxylate-t-butyl ester (betaCCT) attenuated the ataxic-like effects engendered by both types of drugs. However, betaCCT was largely ineffective at blocking the ability of both BZs and non-BZs to induce myorelaxant-like effects.

CONCLUSIONS

These experiments demonstrate dose-dependent motor impairment in squirrel monkeys using quantitative behavioral observation techniques. Altogether, these findings suggest a lack of a prominent role for alpha1 subunit-containing receptors in the alteration of hind-limb flexion, a putative measure of myorelaxation, induced by BZ-type drugs in monkeys.

Synthesis of GABAA receptor agonists and evaluation of their alpha-subunit selectivity and orientation in the GABA binding site

Drugs used to treat various disorders target GABA A receptors. To develop alpha subunit selective compounds, we synthesized 5-(4-piperidyl)-3-isoxazolol (4-PIOL) derivatives. The 3-isoxazolol moiety was substituted by 1,3,5-oxadiazol-2-one, 1,3,5-oxadiazol-2-thione, and substituted 1,2,4-triazol-3-ol heterocycles with modifications to the basic piperidine substituent as well as substituents without basic nitrogen. Compounds were screened by [(3)H]muscimol binding and in patch-clamp experiments with heterologously expressed GABA A alpha ibeta 3gamma 2 receptors (i = 1-6). The effects of 5-aminomethyl-3 H-[1,3,4]oxadiazol-2-one 5d were comparable to GABA for all alpha subunit isoforms. 5-piperidin-4-yl-3 H-[1,3,4]oxadiazol-2-one 5a and 5-piperidin-4-yl-3 H-[1,3,4]oxadiazol-2-thione 6a were weak agonists at alpha 2-, alpha 3-, and alpha 5-containing receptors. When coapplied with GABA, they were antagonistic in alpha 2-, alpha 4-, and alpha 6-containing receptors and potentiated alpha 3-containing receptors. 6a protected GABA binding site cysteine-substitution mutants alpha 1F64C and alpha 1S68C from reacting with methanethiosulfonate-ethylsulfonate. 6a specifically covalently modified the alpha 1R66C thiol, in the GABA binding site, through its oxadiazolethione sulfur. These results demonstrate the feasibility of synthesizing alpha subtype selective GABA mimetic drugs.

Structural basis for ligand recognition at the benzodiazepine binding site of GABAA alpha 3 receptor, and pharmacophore-based virtual screening approach

Given the heterogeneity of GABA(A) receptor, the pharmacological significance of identifying subtype selective modulators is increasingly being recognized. Thus, drugs selective for GABA(A) alpha(3) receptors are expected to display fewer side effects than the drugs presently in clinical use. Hence we carried out 3D QSAR (three-dimensional quantitative structure-activity relationship) studies on a series of novel GABA(A) alpha(3) subtype selective modulators to gain more insight into subtype affinity. To identify the 3D functional attributes required for subtype selectivity, a chemical feature-based pharmacophore, primarily based on selective ligands representing diverse structural classes was generated. The obtained pseudo receptor model of the benzodiazepine binding site revealed a binding mode akin to "Message-Address" concept. Scaffold hopping was carried out across multi-conformational May Bridge database for the identification of novel chemotypes. Further a focused data reduction approach was employed to choose a subset of enriched compounds based on "Drug likeness" and "Similarity-based" methods. These results taken together could provide impetus for rational design and optimization of more selective and high affinity leads with a potential to have decreased adverse effects.