Synthesis of Subtype Selective Bz/GABAA Receptor Ligands for the Treatment of Anxiety, Epilepsy and Neuropathic Pain, as Well as Schizophrenia and Asthma

The α2/α3 subtype selective Bz/GABAA receptor positive allosteric modulator HZ-166 (3) has been shown to be a nonsedating anxiolytic with anticonvulsant and antihyperalgesic activity. However, instability in vitro and in vivo has hindered its advancement into clinical trials. A series of ligands based off HZ-166 (3) were synthesized. Many of these ligands were designed to increase metabolic stability, while others were synthesized to study the effects that electronics and sterics have on the efficacy exerted when bound to the GABAA receptor. The α3 subtype selective methyl ester MP-III-024 (19) was shown to have increased resistance to metabolism in in vitro liver microsomal studies and exhibited significant anxiolytic and antihyperalgesic effects in mice without showing signs of sedation. However, pharmacokinetic studies indicated that esters as a functional group may not be suitable for extensive preclinical studies. A series of heterocyclic bioisosteres were synthesized to specifically overcome short half-lives in vivo. The oxadiazole MP-III-080 (34) and oxazole KRM-II-81 (36) underwent pharmacokinetic studies and were both found to exist in plasma and brain samples in high levels. These results indicated that these and related heterocycles would be stable in vivo to undergo extensive preclinical trials. A dozen ligands were assessed in vivo in an anxiolytic marble burying assay and a rotarod assay designed to measure ataxic effects. The results from these studies and other in vitro protocols led to additional studies using KRM-II-81 (36). This oxazole 36 was found to exhibit significant anxiolytic and anticonvulsant properties, including reducing network firing rate frequency in human brain tissue from a patient suffering from resistance epilepsy. In addition, KRM-II-81 (36) was found to be more efficacious than gabapentin to reverse the effects of hyperalgesia in a neuropathic pain model at a lower dose using rats, as well as exhibiting antidepressant-like effects. The α5 GABAA receptor subtype has been linked to the cognitive disorders in such diseases as schizophrenia, bipolar I disorder and major depressive disorder. The enantiomers SH-053-2\u27F-S-CH3 (51) and SH-053-2\u27F-R-CH3 (52) have been shown to be α2/α3/α5- and α5- subtype selective agonists, respectively. Both ligands (S)-51 and (R)-52 have been shown to reduce some positive symptoms of schizophrenia; the S-enantiomer 51 was active in the poly(I:C) model of schizophrenia while the R-enantiomer 52 was active in the MAM-model of schizophrenia. Due to the high rate of comorbidity of schizophrenia with anxiety, epilepsy and depression, the S-enatiomer (51) is shown here to be useful in these instances exhibiting anxiolytic and anticonvulsant properties. In addition, work on analogs of 52 produced MP-III-004 (63), an α5 subtype selective ligand with reduced efficacy at the α1, α2 and α3 subtypes as compared to 52, as well as the very potent α5 positive allosteric modulator MP-III-022 (65). This methyl amide 65 was shown to activate α5 subtypes in vivo in rats at low concentrations, providing a valuable tool to study the α5 GABAA receptor subtype. Recent work has shown SH-053-2\u27F-R-CH3 (52) and MP-III-022 (65) exert antidepressant-like effects in mice, indicating a new use for α5 subtype selective ligands. Moreover, work by Emala et al. has discovered a use for α5 subtype selective ligands outside of the central nervous system. A number of the ligands, especially the α5 selective acid 73, presented herein have been shown to relax precontracted human and guinea pig airway smooth muscle and may provide a novel treatment for those who suffer from asthma

A New Generation of Corporate Codes of Ethics

Michael K. Braswell is an associate professor in the Department of Finance, Insurance, Real Estate & Law, College of Business, University of North Texas, Denton, Texas 76203. Charles M. Foster is an associate professor in the Department of Finance, Insurance, Real Estate & Law, College of Business, University of North Texas, Denton, Texas 76203. Stephen L. Poe is a professor in the Department of Finance, Insurance, Real Estate & Law, College of Business, University of North Texas, Denton, Texas 76203

Odloženi bihejvioralni efekti SH-I-048A, novog neselektivnog pozitivnog modulatora GABAA receptora, nakon povrede perifernog nerva pacova

The complex clinical picture of mono-neuropathy following injury of peripheral nerve is often accompanied by changes in the patients' affective states. It has been shown that positive allosteric modulators of GABAA receptors can decrease nociceptive transmission in animal pain models. However, recent findings suggest a possibility that at least some of the antinociceptive effects of benzodiazepines, related to neuropathic painful stimuli, may to a significant degree be a consequence of their anxiolytic action. In this study we evaluated the possible delayed effects of SH-I-048A, a newly- synthesized high-efficacy nonselective positive modulator of GABAA receptors, on anxiety-like behavior and locomotor activity in Wistar rats with a previously induced peripheral nerve injury. Assessment of behavioral parameters, using spontaneous locomotor activity and elevated plus maze tests, was performed 48h after completion of single-day three i.p. injections treatment consisting of zero, one, two or three doses of SH-I-048A (10 mg/kg). In general, rats' behavior observed 72 h after a moderate peripheral nerve injury did not indicate the persistence of sequelae of mono-neuropathic pain. The rats treated with three doses of SH-I-048A displayed an enhanced immobility time in the locomotor activity test, without concomitant decrease of the total distance traveled. On the other hand, in the group treated with two doses of SH-I-048A, a decrease in the emotional reactivity in the elevated plus maze test was observed. Subtle changes in the regimen of dosing of SH-I-048A affect locomotor activity and anxiety-related behavior in animals with peripheral nerve injury.Kompleksna klinička slika neuropatije nakon povrede perifernog nerva često je praćena i promenama afektivnog stanja pacijenata. U animalnim modelima bola pokazano je da pozitivni alosterni modulatori GABAA receptora mogu da smanje nociceptivnu transmisiju. Međutim, skorašnji nalazi ukazuju i na mogućnost da je prividni antinociceptivni efekat benzodiazepina nakon delovanja akutnog bolnog stimulusa u značajnoj meri posledica anksiolitičnog efekta. U ovoj studiji ispitani su mogući odloženi efekti novosintetisanog, neselektivnog liganda GABAA receptora (SH-I-048A) na lokomotornu aktivnost i ponašanje u vezi sa anksioznošću kod pacova soja Wistar prethodno podvrgnutih povredi perifernog nerva. Procena bihejvioralnih parametara sprovedena je testovima spontane lokomotorne aktivnosti i uzdignutog plus lavirinta 48 sati nakon što su životinje u periodu od 24 sata primile rastvarač, jednu, dve ili tri doze SH-I-048A (10 mg/kg). Generalno, ponašanje pacova praćeno 72 sata nakon umerene povrede perifernog nerva nije ukazivalo na prisustvo perzistentnih posledica neuropatskog bola. Pacovi prethodno tretirani sa tri doze SH-I-048A ispoljili su povećano vreme imobilnosti u testu lokomotorne aktivnosti, bez značajnog smanjenja ukupnog pređenog puta. S druge strane, u grupi koja je tretirana sa dve doze SH-I-048A zapažena je smanjena emocionalna reaktivnost u uzdignutom plus lavirintu. Kod životinja sa povredom perifernog nerva, suptilne razlike u režimu doziranja pozitivnog modulatora GABAA, mogu značajno da utiču na ponašanje vezano za lomotornu aktivnost i nivo anksioznosti

Ester to amide substitution improves selectivity, efficacy and kinetic behavior of a benzodiazepine positive modulator of GABA(A) receptors containing the alpha 5 subunit

We have synthesized and characterized MP-III-022 ((R)-8-ethynyl 6 (2 fluorophenyl)-N,4-dimethyl4H-benzo[f]imidazo[1,5-alpha][1,4]diazepine-3-carboxamide) in vitro and in vivo as a binding- and efficacy selective positive allosteric modulator of GABA(A) receptors containing the alpha 5 subunit (alpha 5GABA(A)Rs). By approximation of the electrophysiological responses which the estimated free rat brain concentrations can induce, we demonstrated that convenient systemic administration of MP-III-022 in the dose range 110 mg/kg may result in a selective potentiation, over a wide range from mild to moderate to strong, of alpha 5 beta gamma 2 GABA(A) receptors. For eliciting a comparable range of potentiation, the widely studied parent ligand SH-053-2'F-R-CH3 containing an ester moiety needs to be administered over a much wider dose range (10-200 mg/kg), but at the price of activating non-alpha 5 GABA(A)Rs as well as the desired alpha 5GABA(A)Rs at the highest dose. At the dose of 10 mg/kg, which elicits a strong positive modulation of alpha 5GABA(A)Rs, MP-III-022 caused mild, but significant muscle relaxation, while at doses 1-10 mg/kg was devoid of ataxia, sedation or an influence on the anxiety level, characteristic for non-selective benzodiazepines. As an amide compound with improved stability and kinetic properties, MP-III-022 may represent an optimized tool to study the influence of alpha 5GABA(A)Rs on the neuronal pathways related to CNS disorders such as schizophrenia, Alzheimer's disease, Down syndrome or autism

A Review of the Updated Pharmacophore for the Alpha 5 GABA(A) Benzodiazepine Receptor Model

An updated model of the GABA(A) benzodiazepine receptor pharmacophore of the alpha 5-BzR/GABA(A) subtype has been constructed prompted by the synthesis of subtype selective ligands in light of the recent developments in both ligand synthesis, behavioral studies, and molecular modeling studies of the binding site itself. A number of BzR/GABA(A) alpha 5 subtype selective compounds were synthesized, notably alpha 5-subtype selective inverse agonist PWZ-029 (1) which is active in enhancing cognition in both rodents and primates. In addition, a chiral positive allosteric modulator (PAM), SH-053-2'F-R-CH3 (2), has been shown to reverse the deleterious effects in the MAM-model of schizophrenia as well as alleviate constriction in airway smooth muscle. Presented here is an updated model of the pharmacophore for alpha 5 beta 2 gamma 2 Bz/GABA(A) receptors, including a rendering of PWZ-029 docked within the alpha 5-binding pocket showing specific interactions of the molecule with the receptor. Differences in the included volume as compared to alpha 1 beta 2 gamma 2, alpha 2 beta 2 gamma 2, and alpha 3 beta 2 gamma 2 will be illustrated for clarity. These new models enhance the ability to understand structural characteristics of ligands which act as agonists, antagonists, or inverse agonists at the Bz BS of GABA(A) receptors

Sex-Dependent Anti-Stress Effect of an alpha 5 Subunit Containing GABA(A) Receptor Positive Allosteric Modulator

Rationale: Current first-line treatments for stress related disorders such as major depressive disorder (MDD) act on monoaminergic systems and take weeks to achieve a therapeutic effect with poor response and low remission rates. Recent research has implicated the GABAergic system in the pathophysiology of depression, including deficits in interneurons targeting the dendritic compartment of cortical pyramidal cells. Objectives: The present study evaluates whether SH-053-2'F-R-CH3 (denoted "alpha 5-PAM"), a positive allosteric modulator selective for (alpha 5-subunit containing GABA(A) receptors found predominantly on cortical pyramidal cell dendrites, has anti stress effects. Methods: Female and male C57BL6/J mice were exposed to unpredictable chronic mild stress (UCMS) and treated with alpha 5-PAM acutely (30 min prior to assessing behavior) or chronically before being assessed behaviorally. Results: Acute and chronic alpha 5-PAM treatments produce a pattern of decreased stress induced behaviors (denoted as "behavioral emotionality") across various tests in female, but not in male mice. Behavioral Z-scores calculated across a panel of tests designed to best model the range and heterogeneity of human symptomatology confirmed that acute and chronic alpha 5-PAM treatments consistently produce significant decreases in behavioral emotionality in several independent cohorts of females. The behavioral responses to alpha 5-PAM could not be completely accounted for by differences in drug brain disposition between female and male mice. In mice exposed to UCMS, expression of the Gabra5 gene was increased in the frontal cortex after acute treatment and in the hippocampus after chronic treatment with alpha 5-PAM in females only, and these expression changes correlated with behavioral emotionality. Conclusion: We showed that acute and chronic positive modulation of alpha 5 subunit containing GABA(A) receptors elicit anti-stress effects in a sex-dependent manner, suggesting novel therapeutic modalities

Sh-I-048A, an in vitro non-selective super-agonist at the benzodiazepine site of GABAA receptors: The approximated activation of receptor subtypes may explain behavioral effects

Enormous progress in understanding the role of four populations of benzodiazepine-sensitive GABA(A) receptors was paralleled by the puzzling findings suggesting that substantial separation of behavioral effects may be accomplished by apparently nonselective modulators. We report on SH-I-048A, a newly synthesized chiral positive modulator of GABAA receptors characterized by exceptional subnanomolar affinity, high efficacy and non-selectivity. Its influence on behavior was assessed in Wistar rats and contrasted to that obtained with 2 mg/kg diazepam. SH-I-048A reached micromolar concentrations in brain tissue, while the unbound fraction in brain homogenate was around 1.5%. The approximated electrophysiological responses, which estimated free concentrations of SH-I-048A or diazepam are able to elicit, suggested a similarity between the 10 mg/kg dose of the novel ligand and 2 mg/kg diazepam; however, SH-I-048A was relatively more active at and as-containing GABAA receptors. Behaviorally, SH-I-048A induced sedative, muscle relaxant and ataxic effects, reversed mechanical hyperalgesia 24 h after injury, while it was devoid of clear anxiolytic actions and did not affect water-maze performance. While lack of clear anxiolytic actions may be connected with an enhanced potentiation at al-containing GABAA receptors, the observed behavior in the rotarod, water maze and peripheral nerve injury tests was possibly affected by its prominent action at receptors containing the as subunit. The current results encourage further innovative approaches aimed at linking in vitro an in vivo data in order to help define fine-tuning mechanisms at four sensitive receptor populations that underlie subtle differences in behavioral profiles of benzodiazepine site ligands

Regulating anxiety with extrasynaptic inhibition

Aversive experiences can lead to complex behavioral adaptations including increased levels of anxiety and fear generalization. The neuronal mechanisms underlying such maladaptive behavioral changes, however, are poorly understood. Here, using a combination of behavioral, physiological and optogenetic approaches in mouse, we identify a specific subpopulation of central amygdala neurons expressing protein kinase C δ (PKCδ) as key elements of the neuronal circuitry controlling anxiety. Moreover, we show that aversive experiences induce anxiety and fear generalization by regulating the activity of PKCδ+ neurons via extrasynaptic inhibition mediated by α5 subunit-containing GABAA receptors. Our findings reveal that the neuronal circuits that mediate fear and anxiety overlap at the level of defined subpopulations of central amygdala neurons and demonstrate that persistent changes in the excitability of a single cell type can orchestrate complex behavioral changes

Ghosts of other stories: a synthesis of hauntology, crime and space

Criminology has long sought to illuminate the lived experience of those at the margins. More recently, there has been a turn toward the spatial in the discipline. This paper sets out an analytical framework that synthesizes spatial theory with hauntology. We demonstrate how a given space's violent histories can become embedded in the texts that constitute it and the language that describes it. The art installation ‘Die Familie Schneider’ is used as an example of how the incorporation of social trauma can lead to the formation of a spatial “crypt”. Cracking open this “crypt” allows us to draw out Derrida's notion of the specter within the context of a “haunted” city space