Indiplon is a high-affinity positive allosteric modulator with selectivity for alpha1 subunit-containing GABAA receptors

Preferential Synaptic Type of GABA-A Receptor Ligands Enhancing Neuronal Survival and Facilitating Functional Recovery After Ischemic Stroke

Selective enhancement of synaptic GABA signaling mediated by GABA-A receptors has been previously reported to promote functional recovery after ischemic stroke, while tonic GABA signaling has been detrimental. To identify agents that enhance synaptic signaling, we synthesized GABA-A ligands based on three chemotypes with affinity values pKi= 6.44-8.32. Representative compounds showed a preference in functional responses toward synaptic type of GABA-A receptors, compared to the extrasynaptic ones. In a cellular ischemia model (OGD), selected compounds showed the potential to improve neuronal recovery. The selected lead, compound 4, demonstrated the ability to reduce mitochondrial dysfunction, regulate intracellular calcium levels, decrease caspase 3 levels, and promote neurite outgrowth in in vitro assays. In an animal model, compound 4 enhanced motor recovery and showed neuroprotective activity by reducing infarct volume and decreasing poststroke acidosis. These findings underscore the value of selective ligands modulating synaptic GABA-A receptors in promoting recovery from ischemic stroke.

Integrated workflow for the identification of new GABAA R positive allosteric modulators based on the in silico screening with further in vitro validation. Case study using Enamine's stock chemical space

Numerous studies reported an association between GABAA R subunit genes and epilepsy, eating disorders, autism spectrum disorders, neurodevelopmental disorders, and bipolar disorders. This study was aimed to find some potential positive allosteric modulators and was performed by combining the in silico approach with further in vitro evaluation of its real activity. We started from the GABAA R-diazepam complexes and assembled a lipid embedded protein ensemble to refine it via molecular dynamics (MD) simulation. Then we focused on the interaction of α1β2γ2 with some Z-drugs (non-benzodiazepine compounds) using an Induced Fit Docking (IFD) into the relaxed binding site to generate a pharmacophore model. The pharmacophore model was validated with a reference set and applied to decrease the pre-filtered Enamine database before the main docking procedure. Finally, we succeeded in identifying a set of compounds, which met all features of the docking model. The aqueous solubility and stability of these compounds in mouse plasma were assessed. Then they were tested for the biological activity using the rat Purkinje neurons and CHO cells with heterologously expressed human α1β2γ2 GABAA receptors. Whole-cell patch clamp recordings were used to reveal the GABA induced currents. Our study represents a convenient and tunable model for the discovery of novel positive allosteric modulators of GABAA receptors. A High-throughput virtual screening of the largest available database of chemical compounds resulted in the selection of 23 compounds. Further electrophysiological tests allowed us to determine a set of 3 the most outstanding active compounds. Considering the structural features of leader compounds, the study can develop into the MedChem project soon.

Activation of the dorsal, but not the ventral, hippocampus relieves neuropathic pain in rodents

ABSTRACT

Accumulating evidence suggests hippocampal impairment under the chronic pain phenotype. However, it is unknown whether neuropathic behaviors are related to dysfunction of the hippocampal circuitry. Here, we enhanced hippocampal activity by pharmacological, optogenetic, and chemogenetic techniques to determine hippocampal influence on neuropathic pain behaviors. We found that excitation of the dorsal (DH), but not the ventral (VH) hippocampus induces analgesia in 2 rodent models of neuropathic pain (SNI and SNL) and in rats and mice. Optogenetic and pharmacological manipulations of DH neurons demonstrated that DH-induced analgesia was mediated by N-Methyl-D-aspartate and μ-opioid receptors. In addition to analgesia, optogenetic stimulation of the DH in SNI mice also resulted in enhanced real-time conditioned place preference for the chamber where the DH was activated, a finding consistent with pain relief. Similar manipulations in the VH were ineffective. Using chemo-functional magnetic resonance imaging (fMRI), where awake resting-state fMRI was combined with viral vector-mediated chemogenetic activation (PSAM/PSEM89s) of DH neurons, we demonstrated changes of functional connectivity between the DH and thalamus and somatosensory regions that tracked the extent of relief from tactile allodynia. Moreover, we examined hippocampal functional connectivity in humans and observe differential reorganization of its anterior and posterior subdivisions between subacute and chronic back pain. Altogether, these results imply that downregulation of the DH circuitry during chronic neuropathic pain aggravates pain-related behaviors. Conversely, activation of the DH reverses pain-related behaviors through local excitatory and opioidergic mechanisms affecting DH functional connectivity. Thus, this study exhibits a novel causal role for the DH but not the VH in controlling neuropathic pain-related behaviors.

An overview of the synthetic route to the marketed formulations of pyrimidine: A Review

Pyrimidine and its derivatives are a very important class of heterocyclic compounds that show interesting applications in the field of medicinal chemistry. Pyrimidine not only plays an important role as an organic reaction intermediate but also has a wide range of interesting biological activities viz. antibacterial, antifungal, anticancer, anti-inflammatory, antiviral, and antiprotozoal activity, etc. Numerous methods are available for the formation of pyrimidine derivatives have been reported in the literature. The advantage of pyrimidine as a starting material for different therapeutically potent derivatives has given momentum to this research. This review aims to report the new work on the synthesis of marketed drugs which consist of pyrimidine moiety.

Rational approaches for the design of various GABA modulators and their clinical progression

GABA (γ-amino butyric acid) is an important inhibitory neurotransmitter in the central nervous system. Attenuation of GABAergic neurotransmission plays an important role in the etiology of several neurological disorders including epilepsy, Alzheimer's disease, Huntington's chorea, migraine, Parkinson's disease, neuropathic pain, and depression. Increase in the GABAergic activity may be achieved through direct agonism at the GABAA receptors, inhibition of enzymatic breakdown of GABA, or by inhibition of the GABA transport proteins (GATs). These functionalities make GABA receptor modulators and GATs attractive drug targets in brain disorders associated with decreased GABA activity. There have been several reports of development of GABA modulators (GABA receptors, GABA transporters, and GABAergic enzyme inhibitors) in the past decade. Therefore, the focus of the present review is to provide an overview on various design strategies and synthetic approaches toward developing GABA modulators. Furthermore, mechanistic insights, structure-activity relationships, and molecular modeling inputs for the biologically active derivatives have also been discussed. Summary of the advances made over the past few years in the clinical translation and development of GABA receptor modulators is also provided. This compilation will be of great interest to the researchers working in the field of neuroscience. From the light of detailed literature, it can be concluded that numerous molecules have displayed significant results and their promising potential, clearly placing them ahead as potential future drug candidates.

The Z-Drugs Zolpidem, Zaleplon, and Eszopiclone Have Varying Actions on Human GABA A Receptors Containing γ1, γ2, and γ3 Subunits

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.

Thienochromene derivatives inhibit pSTAT1 and pSTAT5 signaling induced by cytokines

Furanocoumarins, particularly furo[3,2-c]coumarins, are found in many natural products. However, coumarins annulated to a thiophene ring have received scarce attention to date in the literature. Therefore, we synthesized 4-oxo-4H-thieno[3,2-c]chromene derivatives and tested in vitro their anti-inflammatory activity. Anti-inflammatory potential of the synthesized compounds (1, 2, 6-8, 9a-e and 10a-c) has been evaluated by measuring various pSTAT (signal transducer and activator of transcription) inhibition within the JAK (Janus-activated family kinase)/STAT signaling pathway. Ethyl 7-hydroxy-4-oxo-4H-thieno[3,2-c]chromene-2-carboxylate (7) showed best inhibition properties on pSTAT5 in GM-CSF (Granulocyte-macrophage colony-stimulating factor)-triggered PBMC assay, with IC₅₀ value of 5.0 µM.

L-Proline-catalyzed regioselective C1 arylation of tetrahydroisoquinolines through a multicomponent reaction under solvent-free conditions

Here we disclose the C1 arylation of tetrahydroisoquinolines (THIQ) through regioselective C(sp3)-H functionalization using a multicomponent reaction. The reaction was performed by reacting THIQ, aldehydes and aminopyrazoles or indoles under neat conditions with l-proline as a catalyst. The regioselectivity of the products was confirmed by X-ray analysis and spectroscopic data. The formation of an azomethine ylide intermediate is crucial for obtaining the regioselectivity.

Copper-catalysed N-arylation of 5-aminopyrazoles: a simple route to pyrazolo[3,4-b]indoles

A copper-catalysed intramolecular N-arylation of 5-aminopyrazoles is demonstrated for the first time. Highly substituted pyrazolo[3,4-b]indoles are synthesized. In particular, the indole core is decorated with halogens and alkyl and methoxy groups. Furthermore, a selective N-arylation of unsymmetrical diaryl bromide containing pyrazoles is exemplified, resulting in valuable pyrazolo[1,5-a]benzimidazoles.

Expression and Function of GABA Receptors in Myelinating Cells

Myelin facilitates the fast transmission of nerve impulses and provides metabolic support to axons. Differentiation of oligodendrocyte progenitor cells (OPCs) and Schwann cell (SC) precursors is critical for myelination during development and myelin repair in demyelinating disorders. Myelination is tightly controlled by neuron-glia communication and requires the participation of a wide repertoire of signals, including neurotransmitters such as glutamate, ATP, adenosine, or γ-aminobutyric acid (GABA). GABA is the main inhibitory neurotransmitter in the central nervous system (CNS) and it is also present in the peripheral nervous system (PNS). The composition and function of GABA receptors (GABARs) are well studied in neurons, while their nature and role in glial cells are still incipient. Recent studies demonstrate that GABA-mediated signaling mechanisms play relevant roles in OPC and SC precursor development and function, and stand out the implication of GABARs in oligodendrocyte (OL) and SC maturation and myelination. In this review, we highlight the evidence supporting the novel role of GABA with an emphasis on the molecular identity of the receptors expressed in these glial cells and the possible signaling pathways involved in their actions. GABAergic signaling in myelinating cells may have potential implications for developing novel reparative therapies in demyelinating diseases.

Reintroduction of quazepam: an update on comparative hypnotic and adverse effects

Insomnia is a prevalent disorder that affects over one-third of the U.S. population to varying degrees and is highly disruptive towards quality of life. Pharmacological treatments for insomnia include benzodiazepines (BZs) and the non-BZ 'Z-drugs' (zolpidem, zaleplon, eszopiclone, zopiclone), which are amongst the most widely prescribed medications. Yet, these agents can produce adverse effects such as tolerance to the hypnotic effect, rebound insomnia, next-day residual drowsiness, as well as amnesia and complex behaviours such as sleep-walking, sleep-eating and sleep-driving. Quazepam, one of the five BZ approved for treatment of insomnia, was recently relaunched to the U.S. market in 2016 and is distinguished amongst hypnotic BZ by unique pharmacological characteristics including selectivity for sleep-promoting α1-subunit containing γ-aminobutyric acid (GABA-A) receptors and a significantly lower relative receptor binding affinity. These features likely drive the decreased rate of adverse events seen clinically with quazepam, such as tolerance, rebound insomnia and amnesic behaviours, compared with other BZ. Given the recent reintroduction of quazepam as a pharmacotherapeutic option, and the lack of head-to-head comparative trials against newer agents, the purpose of this review is to provide an update on distinguishing features of quazepam with regard to its pharmacology, pharmacokinetics, sleep efficacy and potential adverse effects compared to other agents used for insomnia.

Anti-aggregation effect on platelets of Indiplon a hypnotic sedative non-benzodiazepine drug

Cardiovascular diseases are one of the main public health problems, and many of them, their pathophysiology involves alterations in platelet activity. Platelet activation is an essential event that is regulated by the intracellular concentrations of Ca2+ and cAMP. Interestingly, it has been shown that the activation of adenosine A2A receptors increases cAMP levels and produces the inhibition of platelet aggregation, which appears as a potential target for regulation of platelet activity. Therefore, we tried to activate A2A receptors using Indiplon, a drug developed for the treatment of insomnia, and analyze its effect on platelet activity in vitro. Our results indicate that Indiplon is able to interact in silico with the adenosine A2A receptor (ΔG_bind of -73.321 kcal/mol, similar to that obtained with adenosine), which is involved in the regulation of platelet cAMP levels. In functional studies using PRP, a reduction in platelet aggregation induced by ADP was observed in the presence of Indiplon at 500 μM with a percentage of inhibition 70%, where the use of specific inhibitors (ZM241385 and MSX-2) of the A2A receptor also blocked these effects reducing the percentage of inhibition to 41% and 34.1%, respectively. Also, the use of Indiplon produced a decrease in the expression in the membrane of P-selectin. Thus, Indiplon acts as an A2A receptor agonist and whose activation results in inhibition of platelet aggregation and activation, showing a possible cardiovascular protective role.

International Union of Basic and Clinical Pharmacology. CVI: GABAA Receptor Subtype- and Function-selective Ligands: Key Issues in Translation to Humans

GABAA receptors are the major inhibitory transmitter receptors in the brain. They are ligand-gated chloride channels and the site of action of benzodiazepines, barbiturates, neuroactive steroids, anesthetics, and convulsants. GABAA receptors are composed of five subunits that can belong to different subunit classes. The existence of 19 homologous subunits and their distinct regional, cellular, and subcellular distribution gives rise to a large number of GABAA receptor subtypes with distinct pharmacology, which modulate different functions of the brain. A variety of compounds have been identified that were claimed to modulate selectively individual GABAA receptor subtypes. However, many of these compounds have only incompletely been investigated or, in addition to a preferential modulation of a receptor subtype, also modulate other subtypes at similar concentrations. Although their differential efficacy at distinct receptor subtypes reduced side effects in behavioral experiments in rodents, the exact receptor subtypes mediating their behavioral effects cannot be unequivocally delineated. In addition, the discrepant in vivo effects of some of these compounds in rodents and man raised doubts on the applicability of the concept of receptor subtype selectivity as a guide for the development of clinically useful drugs. Here, we provide an up-to-date review on the currently available GABAA receptor subtype-selective ligands. We present data on their actual activity at GABAA receptor subtypes, discuss the translational aspect of subtype-selective drugs, and make proposals for the future development of ligands with better anxioselectivity in humans. Finally, we discuss possible ways to strengthen the conclusions of behavioral studies with the currently available drugs.

Thiophene Syntheses by Ring Forming Multicomponent Reactions

Thiophenes occur as important building blocks in natural products, pharmaceutical active compounds, and in materials for electronic and opto-electronic devices. Therefore, there is a considerable demand for efficient synthetic strategies for producing these compounds. This review focuses on ring-forming multicomponent reactions for synthesizing thiophenes and their derivatives.

Activation of axon initial segmental GABAA receptors inhibits action potential generation in neocortical GABAergic interneurons

Ionotropic GABA_A receptors expressing at the axon initial segment (AIS) of glutamatergic pyramidal cell (PC) in the cortex plays critical roles in regulating action potential generation. However, it remains unclear whether these receptors also express at the AIS of cortical GABAergic interneurons. In mouse prefrontal cortical slices, we performed experiments at the soma and AIS of the two most abundant GABAergic interneurons: parvalbumin (PV) and somatostatin (SST) positive neurons. Local application of GABA at the perisomatic axonal regions could evoke picrotoxin-sensitive currents with a reversal potential near the Cl^- equilibrium potential. Puffing agonists to outside-out patches excised from AIS confirmed the expression of GABA_A receptors. Further pharmacological experiments revealed that GABA_A receptors in AIS of PV neurons contain α1 subunits, different from those containing α2/3 in AIS and α4 in axon trunk of layer-5 PCs. Cell-attached recording at the soma of PV and SST neurons revealed that the activation of AIS GABA_A receptors inhibits the action potential generation induced by synaptic stimulation. Together, our results demonstrate that the AIS of PV and SST neurons express GABA_A receptors with distinct subunit composition, which exert an inhibitory effect on neuronal excitability in these inhibitory interneurons.

Thalamic Control of Cognition and Social Behavior Via Regulation of Gamma-Aminobutyric Acidergic Signaling and Excitation/Inhibition Balance in the Medial Prefrontal Cortex

BACKGROUND

The mediodorsal thalamus plays a critical role in cognition through its extensive innervation of the medial prefrontal cortex (mPFC), but how the two structures cooperate at the single-cell level to generate associated cognitive functions and other mPFC-dependent behaviors remains elusive. Maintaining the proper balance between excitation and inhibition (E/I balance) is of principal importance for organizing cortical activity. Furthermore, the PFC E/I balance has been implicated in successful execution of multiple PFC-dependent behaviors in both animal research and the context of human psychiatric disorders.

METHODS

Here, we used a pharmacogenetic strategy to decrease mediodorsal thalamic activity in adult male rats and evaluated the consequences for E/I balance in PFC pyramidal neurons as well as cognition, social interaction, and anxiety.

RESULTS

We found that dampening mediodorsal thalamic activity caused significant reductions in gamma-aminobutyric acidergic signaling and increased E/I balance in the mPFC and was concomitant with abnormalities in these behaviors. Furthermore, by selectively activating parvalbumin interneurons in the mPFC with a novel pharmacogenetic approach, we restored gamma-aminobutyric acidergic signaling and E/I balance as well as ameliorated all behavioral impairments.

CONCLUSIONS

These findings underscore the importance of thalamocortical activation of mPFC gamma-aminobutyric acidergic interneurons in a broad range of mPFC-dependent behaviors. Furthermore, they highlight this circuitry as a platform for therapeutic investigation in psychiatric diseases that involve impairments in PFC-dependent behaviors.

An Efficient One-Pot, Four-Component Synthesis of Pyrazolo[3,4-b]pyridines Catalyzed by Tetrapropylammonium Bromide (TPAB) in Water

A novel and one-pot pseudo-four-component reaction between a series of arylglyoxals, malononitrile, 3-methyl-1-phenyl-1H-pyrazol-5-amine, and acetone in the presence of tetrapropylammonium bromide (TPAB) has been developed to synthesize a series of new substituted pyrazolo[3,4-b]pyridines, using water as an environmentally friendly solvent, in high to excellent yields.

Physiological and pharmacological properties of inhibitory postsynaptic currents mediated by α5β1γ2, α5β2γ2 and α5β3γ2 GABAA receptors

α5-containing GABA_ARs are potential therapeutic targets for clinical conditions including age-related dementia, stroke, schizophrenia, Down syndrome, anaesthetic-induced amnesia, anxiety and pain. α5-containing GABA_ARs are expressed in layer 5 cortical neurons and hippocampal pyramidal neurons where they mediate both tonic currents and slow inhibitory postsynaptic currents (IPSCs). A range of drugs has been developed to specifically modulate these receptors. The main α5-containing GABA_ARs that are likely to exist in vivo are the α5β1γ2, α5β2γ2 and α5β3γ2 isoforms. We currently have few clues as to how these isoforms are distributed between synaptic and extrasynaptic compartments or their relative roles in controlling neuronal excitability. Accordingly, the aim of this study was to define the basic biophysical and pharmacological properties of IPSCs mediated by the three isoforms in a hippocampal neuron-HEK293 cell co-culture assay. The IPSC decay time constants were slow (α5β1γ2L: 45 ms; α5β1γ2L: 80 ms; α5β3γ2L: 184 ms) and were largely dominated by the intrinsic channel deactivation rates. By comparing IPSC rise times, we inferred that α5β1γ2L GABA_ARs are located postsynaptically whereas the other two are predominantly perisynaptic. α5β3γ2L GABA_ARs alone mediated tonic currents. We quantified the effects of four α5-specific inverse agonists (TB-21007, MRK-016, α5IA and L-655708) on IPSCs mediated by the three isoforms. All compounds selectively inhibited IPSC amplitudes and accelerated IPSC decay rates, albeit with distinct isoform specificities. MRK-016 also significantly accelerated IPSC rise times. These results provide a reference for future studies seeking to identify and characterize the properties of IPSCs mediated by α5-containing GABA_AR isoforms in neurons.

Organocatalytic Stereoconvergent Synthesis of α-CF3 Amides: Triketopiperazines and Their Heterocyclic Metamorphosis

The highly enantioselective alkylation of α-CF₃ enolates, generated from triketopiperazines, has been accomplished through use of a bifunctional thiourea organocatalyst to facilitate 1,4-addition to varied enone acceptors. On treatment with appropriate nitrogen nucleophiles, the chiral triketopiperazine products undergo a metamorphosis, to provide novel fused heterocyclic lactams such as extended pyrazolopyrimidines.

Regioselective Synthesis of 7-(Trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines via Reaction of Pyrazolamines with Enynones

Condensation of enynones readily available from cheap starting material with pyrazolamines provides easy access to fluorescent 7-(trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines. The reaction is straightforward, does not require the use of any additional reagents or catalysts, and can be performed without inert atmosphere. Various substituents and functional groups in both enynone and pyrazolamine are tolerated. The presented method features full regioselectivity, high isolated yields, and simplicity of both setup and product purification. Fluorescent properties of the obtained pyrazolopyrimidines were studied.

Axon-to-Glia Interaction Regulates GABAA Receptor Expression in Oligodendrocytes

Myelination requires oligodendrocyte-neuron communication, and both neurotransmitters and contact interactions are essential for this process. Oligodendrocytes are endowed with neurotransmitter receptors whose expression levels and properties may change during myelination. However, only scant information is available about the extent and timing of these changes or how they are regulated by oligodendrocyte-neuron interactions. Here, we used electrophysiology to study the expression of ionotropic GABA, glutamate, and ATP receptors in oligodendrocytes derived from the optic nerve and forebrain cultured either alone or in the presence of dorsal root ganglion neurons. We observed that oligodendrocytes from both regions responded to these transmitters at 1 day in culture. After the first day in culture, however, GABA sensitivity diminished drastically to less than 10%, while that of glutamate and ATP remained constant. In contrast, the GABA response amplitude was sustained and remained stable in oligodendrocytes cocultured with dorsal root ganglion neurons. Immunochemistry and pharmacological properties of the responses indicated that they were mediated by distinctive GABAA receptors and that in coculture with neurons, the oligodendrocytes bearing the receptors were those in direct contact with axons. These results reveal that GABAA receptor regulation in oligodendrocytes is driven by axonal cues and that GABA signaling may play a role in myelination and/or during axon-glia recognition.

Regional Specificity of GABAergic Regulation of Cross-Modal Plasticity in Mouse Visual Cortex after Unilateral Enucleation

In adult mice, monocular enucleation (ME) results in an immediate deactivation of the contralateral medial monocular visual cortex. An early restricted reactivation by open eye potentiation is followed by a late overt cross-modal reactivation by whiskers (Van Brussel et al., 2011). In adolescence (P45), extensive recovery of cortical activity after ME fails as a result of suppression or functional immaturity of the cross-modal mechanisms (Nys et al., 2014). Here, we show that dark exposure before ME in adulthood also prevents the late cross-modal reactivation component, thereby converting the outcome of long-term ME into a more P45-like response. Because dark exposure affects GABAergic synaptic transmission in binocular V1 and the plastic immunity observed at P45 is reminiscent of the refractory period for inhibitory plasticity reported by Huang et al. (2010), we molecularly examined whether GABAergic inhibition also regulates ME-induced cross-modal plasticity. Comparison of the adaptation of the medial monocular and binocular cortices to long-term ME or dark exposure or a combinatorial deprivation revealed striking differences. In the medial monocular cortex, cortical inhibition via the GABAA receptor α1 subunit restricts cross-modal plasticity in P45 mice but is relaxed in adults to allow the whisker-mediated reactivation. In line, in vivo pharmacological activation of α1 subunit-containing GABAA receptors in adult ME mice specifically reduces the cross-modal aspect of reactivation. Together with region-specific changes in glutamate acid decarboxylase (GAD) and vesicular GABA transporter expression, these findings put intracortical inhibition forward as an important regulator of the age-, experience-, and cortical region-dependent cross-modal response to unilateral visual deprivation.

SIGNIFICANCE STATEMENT

In adult mice, vision loss through one eye instantly reduces neuronal activity in the visual cortex. Strengthening of remaining eye inputs in the binocular cortex is followed by cross-modal adaptations in the monocular cortex, in which whiskers become a dominant nonvisual input source to attain extensive cortical reactivation. We show that the cross-modal component does not occur in adolescence because of increased intracortical inhibition, a phenotype that was mimicked in adult enucleated mice when treated with indiplon, a GABAA receptor α1 agonist. The cross-modal versus unimodal responses of the adult monocular and binocular cortices also mirror regional specificity in inhibitory alterations after visual deprivation. Understanding cross-modal plasticity in response to sensory loss is essential to maximize patient susceptibility to sensory prosthetics.

Functional characterization of the 1,5-benzodiazepine clobazam and its major active metabolite N-desmethylclobazam at human GABA(A) receptors expressed in Xenopus laevis oocytes

The 1,5-benzodiazepine clobazam is indicated for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients 2 years of age or older in the United States, and for treatment of anxiety and various forms of epilepsy elsewhere. Clobazam has been reported to exhibit different in vivo adverse effects and addiction liability profile than the classic 1,4-benzodiazepines. In this study, it was investigated whether the in vitro pharmacological properties of clobazam and its major active metabolite N-desmethylclobazam could explain some of these clinical differences. The functional properties of the two 1,5-benzodiazepines were characterized at the human γ-aminobutyric acid type A receptor (GABA_AR) subtypes α₁β₂γ_2S, α₂β₂γ_2S, α₃β₂γ_2S, α₅β₂γ_2S and α₆β₂δ expressed in Xenopus laevis oocytes by use of two-electrode voltage-clamp electrophysiology and compared to those exhibited by the 1,4-benzodiazepine clonazepam. All three compounds potentiated GABA EC₂₀-evoked responses through the α_1,2,3,5β₂γ_2S GABA_ARs in a reversible and concentration-dependent manner, with each displaying similar EC₅₀ values at the four subtypes. Furthermore, the degrees of potentiation of the GABA EC₂₀ currents through the four receptors mediated by saturating modulator concentrations did not differ substantially for any of the three benzodiazepines. The three compounds were substantially less potent (200-3900 fold) as positive allosteric modulators at the α₆β₂δ GABA_AR than at the α_1,2,3,5β₂γ_2S receptors. Interestingly, however, clobazam and especially N-desmethylclobazam were highly efficacious potentiators of α₆β₂δ receptor signaling. Although this activity component is unlikely to contribute to the in vivo effects of clobazam/N-desmethylclobazam, the 1,5-benzodiazepine could constitute an interesting lead for novel modulators targeting this low-affinity binding site in GABA_ARs. In conclusion, the non-selective modulation exerted by clobazam, N-desmethylclobazam and clonazepam at the α₁β₂γ_2S, α₂β₂γ_2S, α₃β₂γ_2S and α₅β₂γ_2S GABA_ARs indicate that the observed clinical differences between clobazam and 1,4-benzodiazepines are likely to arise from factors other than their respective pharmacological properties at the GABA_ARs as investigated here.

Pentraxins coordinate excitatory synapse maturation and circuit integration of parvalbumin interneurons

Circuit computation requires precision in the timing, extent, and synchrony of principal cell (PC) firing that is largely enforced by parvalbumin-expressing, fast-spiking interneurons (PVFSIs). To reliably coordinate network activity, PVFSIs exhibit specialized synaptic and membrane properties that promote efficient afferent recruitment such as expression of high-conductance, rapidly gating, GluA4-containing AMPA receptors (AMPARs). We found that PVFSIs upregulate GluA4 during the second postnatal week coincident with increases in the AMPAR clustering proteins NPTX2 and NPTXR. Moreover, GluA4 is dramatically reduced in NPTX2(-/-)/NPTXR(-/-) mice with consequent reductions in PVFSI AMPAR function. Early postnatal NPTX2(-/-)/NPTXR(-/-) mice exhibit delayed circuit maturation with a prolonged critical period permissive for giant depolarizing potentials. Juvenile NPTX2(-/-)/NPTXR(-/-) mice display reduced feedforward inhibition yielding a circuit deficient in rhythmogenesis and prone to epileptiform discharges. Our findings demonstrate an essential role for NPTXs in controlling network dynamics highlighting potential therapeutic targets for disorders with inhibition/excitation imbalances such as schizophrenia.

Non-Benzodiazepine Receptor Agonists for Insomnia

Because of proven efficacy, reduced side effects, and less concern about addiction, non-benzodiazepine receptor agonists (non-BzRA) have become the most commonly prescribed hypnotic agents to treat onset and maintenance insomnia. First-line treatment is cognitive-behavioral therapy. When pharmacologic treatment is indicated, non-BzRA are first-line agents for the short-term and long-term management of transient and chronic insomnia related to adjustment, psychophysiologic, primary, and secondary causation. In this article, the benefits and risks of non-BzRA are reviewed, and the selection of a hypnotic agent is defined, based on efficacy, pharmacologic profile, and adverse events.

Pyrazoloquinazolines: Synthetic strategies and bioactivities

Numerous N-heterocycles are indisputably evidenced to exhibit myriad biological activities. In the recent past, attempts made to condense the various heterocycles have resulted in derivatives possessing better bioactivities. Among many such condensed heterocycles, pyrazoloquinazolines have managed to hold the attention of many researchers, owing to the broad spectrum of activities they portray. This review is the first of its kind to congregate the various pyrazoloquinazolines reported until now and categorizes these structurally isomeric classes into eleven different groups based on the fusion pattern of the ring such as [1,5-c], [5,1-b], [4,3-h], etc. Furthermore, this review is a concerted effort to highlight design, synthetic strategies as well as biological activities of each class of this condensed heterocycle. Structure-activity relationship studies and in silico approaches wherever reported have also been discussed. In addition, manuscript also offers scope for design, synthesis and generation of libraries of unreported classes of pyrazoloquinazolines for the biological evaluation.

Cntnap4 differentially contributes to GABAergic and dopaminergic synaptic transmission

Although considerable evidence suggests that the chemical synapse is a lynchpin underlying affective disorders, how molecular insults differentially affect specific synaptic connections remains poorly understood. For instance, Neurexin 1a and 2 (NRXN1 and NRXN2) and CNTNAP2 (also known as CASPR2), all members of the neurexin superfamily of transmembrane molecules, have been implicated in neuropsychiatric disorders. However, their loss leads to deficits that have been best characterized with regard to their effect on excitatory cells. Notably, other disease-associated genes such as BDNF and ERBB4 implicate specific interneuron synapses in psychiatric disorders. Consistent with this, cortical interneuron dysfunction has been linked to epilepsy, schizophrenia and autism. Using a microarray screen that focused upon synapse-associated molecules, we identified Cntnap4 (contactin associated protein-like 4, also known as Caspr4) as highly enriched in developing murine interneurons. In this study we show that Cntnap4 is localized presynaptically and its loss leads to a reduction in the output of cortical parvalbumin (PV)-positive GABAergic (γ-aminobutyric acid producing) basket cells. Paradoxically, the loss of Cntnap4 augments midbrain dopaminergic release in the nucleus accumbens. In Cntnap4 mutant mice, synaptic defects in these disease-relevant neuronal populations are mirrored by sensory-motor gating and grooming endophenotypes; these symptoms could be pharmacologically reversed, providing promise for therapeutic intervention in psychiatric disorders.

Early adolescent MK-801 exposure impairs the maturation of ventral hippocampal control of basolateral amygdala drive in the adult prefrontal cortex

The adolescent susceptibility to the onset of psychiatric disorders is only beginning to be understood when factoring in the development of the prefrontal cortex (PFC). The functional maturation of the PFC is dependent upon proper integration of glutamatergic inputs from the ventral hippocampus (vHipp) and the basolateral amygdala (BLA). Here we assessed how transient NMDAR blockade during adolescence alters the functional interaction of vHipp-BLA inputs in regulating PFC plasticity. Local field potential recordings were used to determine changes in long-term depression (LTD) and long-term potentiation (LTP) of PFC responses resulting from vHipp and BLA high-frequency stimulation in adult rats that received repeated injections of saline or the NMDAR antagonist MK-801 from postnatal day 35 (P35) to P40. We found that early adolescent MK-801 exposure elicited an age- and input-specific dysregulation of vHipp-PFC plasticity, characterized by a shift from LTD to LTP without altering the BLA-induced LTP. Data also showed that the vHipp normally resets the LTP state of BLA transmission; however, this inhibitory regulation is absent following early adolescent MK-801 treatment. This deficit was reminiscent of PFC responses seen in drug-naive juveniles. Notably, local prefrontal upregulation of GABAAα1 function completely restored vHipp functionality and its regulation of BLA plasticity in MK-801-treated rats. Thus, NMDAR signaling is critical for the periadolescent acquisition of a GABA-dependent hippocampal control of PFC plasticity, which enables the inhibitory control of the prefrontal output by the vHipp. A dysregulation of this pathway can alter PFC processing of other converging afferents such as those from the BLA.

The effects of repeated zolpidem treatment on tolerance, withdrawal-like symptoms, and GABAA receptor mRNAs profile expression in mice: comparison with diazepam

RATIONALE

Zolpidem is a short-acting, non-benzodiazepine hypnotic that acts as a full agonist at α1-containing GABAA receptors. Overall, zolpidem purportedly has fewer instances of abuse and dependence than traditionally used benzodiazepines. However, several studies have shown that zolpidem may be more similar to benzodiazepines in terms of behavioral tolerance and withdrawal symptoms.

OBJECTIVES

In the current study, we examined whether subchronic zolpidem or diazepam administration produced deficits in zolpidem's locomotor-impairing effects, anxiety-like behaviors, and changes in GABAAR subunit messenger RNA (mRNA).

METHODS

Mice were given subchronic injections of either zolpidem (10 mg/kg), diazepam (20 mg/kg), or vehicle twice daily for 7 days. On day 8, mice were given a challenge dose of zolpidem (2 mg/kg) or vehicle before open field testing. Another set of mice underwent the same injection regimen but were sacrificed on day 8 for qRT-PCR analysis.

RESULTS

We found that subchronic zolpidem and diazepam administration produced deficits in the acute locomotor-impairing effects of zolpidem and increased anxiety-like behaviors 1 day after drug termination. In addition, we found that subchronic treatment of zolpidem and diazepam induced distinct but overlapping GABAAR subunit mRNA changes in the cortex but few changes in the hippocampus, amygdala, or prefrontal cortex. Levels of mRNA measured in separate mice after a single injection of either zolpidem or diazepam revealed no mRNA changes.

CONCLUSIONS

In mice, subchronic treatment of zolpidem and diazepam can produce deficits in the locomotor-impairing effects of zolpidem, anxiety-like withdrawal symptoms, and subunit-specific mRNA changes.

Indiplon is hydrolyzed by arylacetamide deacetylase in human liver

Human arylacetamide deacetylase (AADAC) catalyzes the hydrolysis of some clinically used drugs, but the information available on its substrates is limited. To increase our knowledge of the AADAC substrates, we examined whether AADAC catalyzes the hydrolysis of indiplon, which was initially developed as a hypnotic sedative drug. It has been reported that approximately 30-40% of the administered indiplon was hydrolyzed to deacetylindiplon in humans, but the enzyme responsible for this hydrolysis had not been identified. We detected high levels of indiplon hydrolase activity in human liver microsomes (HLMs), but the levels found in human liver cytosol and plasma were scarcely detectable. Recombinant AADAC showed a high level of indiplon hydrolase activity, whereas recombinant carboxylesterase 1 (CES1) and 2 (CES2) showed marginal activity. The indiplon hydrolase activity of HLM was potently inhibited by vinblastine, a potent inhibitor of AADAC and CES2, but it was not inhibited by digitonin and telmisartan, inhibitors of CES1 and CES2, respectively. In a panel of 24 individual HLM samples, the indiplon hydrolase activities were significantly correlated with the hydrolase activities of flutamide, phenacetin, and rifampicin, which are known AADAC substrates. An HLM sample with a homozygous AADAC*3 allele, which was previously found to exhibit decreased enzyme activity, showed the lowest indiplon hydrolase activity among the 24 tested samples. Collectively, we found that human AADAC is responsible for the hydrolysis of indiplon. Thus, we can add indiplon to the list of human AADAC substrates.

Microwave-assisted palladium mediated efficient synthesis of pyrazolo[3,4-b]pyridines, pyrazolo[3,4-b]quinolines, pyrazolo[1,5-a]pyrimidines and pyrazolo[1,5-a]quinazolines

An efficient method was developed for the synthesis of pyrazole fused heterocycles via the palladium-catalyzed solvent free reaction of β-halovinyl/aryl aldehydes and 3-aminopyrazoles/5-aminopyrazoles under microwave irradiation in good yields.