Valium without dependence? Individual GABAA receptor subtype contribution toward benzodiazepine addiction, tolerance, and therapeutic effects

Synthesis and evaluation of neuroactive steroids with novel pharmacophore at C-21 let identify a compound with advantageous PK profile and higher EC50 and Emax as PAM on GABAA receptor

Zuranolone (SAGE-217) is a neuroactive steroid (γ-aminobutyric acid)A (GABAA) receptor positive allosteric modulator (PAM) as the first oral drug approved by the FDA in 2023, which is used to treat patients with postpartum depression (PPD). SAGE-217 has a "black box" warning with impairing ability to drive or engage in other potentially hazardous activities. In addition, SAGE-217 can cause CNS depressant effects such as somnolence and confusion, suicidal thoughts and behavior and embryo-fetal toxicity. Based on the structure-activity relationship (SAR) of SAGE-217, a total of 28 neuroactive steroids with novel pharmacophore at C-21 modulated SAGE-217 derivatives were designed and synthesized. The biological activities were evaluated by both synaptic α1β2γ2 GABAA receptor and extrasynaptic α4β3δ GABAA receptor cell assays. The optimal compound S28 exhibited much more potent potency and similar efficacy at extrasynaptic GABAA receptor than SAGE-217. Different from above, compound S28 exhibited similar potency and lower efficacy at synaptic GABAA receptor than SAGE-217, which were consistent with the analysis of molecular docking and dynamics simulation results. The appropriate lower efficacy at synaptic GABAA receptor of compound S28 might contribute to reduce the side effects of excessive sedation. Furthermore, compound S28 was demonstrated to have excellent in vivo pharmacokinetic (PK) parameters, robust in vivo pharmacodynamic (PD) effects and good safety profiles. Therefore, compound S28 represents a potentially promising treatment of PPD candidate that warrants further investigation.

New Insights Into Pharmacology of GABAA Receptor Alpha Subunits-Selective Modulators

BACKGROUND

Benzodiazepines have long held a leading position in medical therapeutics, known for their multiple common therapeutic properties and primarily being prescribed for anxiety and insomnia. However, their lack of specificity and various side effects have led to a reevaluation of their long-term use, resulting in a rapid growth in the literature focusing on targeted therapies.

AREAS OF UNCERTAINTY

Despite many efforts, uncertainties persist and there are heterogeneous findings across studies regarding the pharmacological effects attributed to gamma-aminobutyric acid type A (GABAA) receptor subunits. Selective compounds targeting GABAA receptor alpha subunits are currently under active research and definitive conclusions have not been reached yet. Some compounds have not progressed to clinical trials, while others, if advanced, have been halted. These challenges emphasize the difficulty in translating preclinical findings into clinical use.

DATA SOURCES

A literature review was conducted using the PubMed database, searching for articles discussing GABAA receptor subunits. The search was refined by including only selective compounds with potential anxiolytic and cognitive enhancement properties.

RESULTS

Findings reveal compounds with promising anxiolytic and antidepressant effects with minimal sedation and absence of tolerance development. Moreover, some compounds show potential in alleviating cognitive dysfunction. There is a broad spectrum of potential therapeutic applications for selective compounds, ranging from neurological disorders such as epilepsy and neuropathic pain to cognitive dysfunction-related conditions. Currently, the leading selective compounds with the most promising results in ongoing clinical trials are basmisanil and darigabat. Basmisanil holds further exploration potential in the treatment of cognitive impairment and related conditions, while darigabat shows progress in the advancement of adjunctive therapy of focal onset seizures and for the treatment of panic disorder, respectively.

CONCLUSIONS

Future drug discovery efforts are encouraged to focus on positive allosteric modulators that selectively target the α2, α3 subunits and negative/positive allosteric modulators that target the α5 subunit of the GABAA receptor. The pursuit of ligands possessing only anxiolytic effects or those enhancing cognition continues to be an important focus for future research, with promising advancements depicted in recent studies.

Long-term effects of benzodiazepine discontinuation among older adults: potential improvements on depressive symptoms

OBJECTIVES

To examine how change in benzodiazepine (BZD) use is linked to changes in depressive symptoms intensity, worry intensity, and sleep quality over 16 months.

METHOD

Data come from a larger randomised controlled trial (RCT) named the 'Programme d'Aide du Succès au SEvrage (PASSE-60+)' study (NCT02281175). Seventy-three participants age 60 years and older took part in a 4-month discontinuation programme and were assessed four times over 16 months. Change in BZD use was defined as the difference in reported mg/day between two assessments. Control variables were RCT discontinuation group; BZD use at T1; and either depressive symptoms, worry intensity, or sleep quality at T1. Hierarchical multiple regressions were used to analyse data.

RESULTS

In the short term, right after the discontinuation programme, sleep quality worsened with lower BZD use. This link was no longer significant at the 3- and 12-month follow-up. In the long term, depressive symptoms lowered with lower BZD use. No change was found in worry intensity in relation to BZD use at all measurement times.

CONCLUSION

Discontinuation may improve depressive symptoms. Our study also questions the long-term effectiveness of BZD use, since long-term discontinuation was not linked with change in worry intensity and sleep quality.

Zolpidem Stimulant Effect and Dependence: A Case Report on Intranasal Use

Zolpidem is a widely used hypnotic. Dependence on zolpidem due to the induction of euphoria is a rare condition, while intranasal misuse of zolpidem is a rather new phenomenon. We present the first case of a patient who developed zolpidem dependence, which was associated with the prompt onset of euphoria exclusively following intranasal use. Mr. A was a 51-year-old polydrug abuser with antisocial personality disorder and a physical dependence on zolpidem. Over several years, he consumed 500 mg of the drug daily, usually divided into 30 mg doses, exclusively via the nasal route because unlike the oral administration of the same dose of the drug, intranasal administration induced euphoria. Euphoric effects manifested 3-5 minutes after taking the drug, and pronounced withdrawal symptoms (i.e., profuse sweating, tremors, nausea, vomiting, diarrhea, and inability to drink and eat), present 7-8 hours after the use could disappear within 3-5 minutes upon drug re-administration. The dependence was managed through a slow tapering of the zolpidem use. Clinicians should be aware that intranasal use of zolpidem could be associated with euphoric effects and the development of addiction. The potential for misuse of zolpidem via the nasal route may be of interest for future research.

Hyperbaric oxygen therapy for poststroke insomnia: a systematic review and meta-analysis protocol

INTRODUCTION

Insomnia stands as a frequent consequence of a cerebrovascular event, afflicting a substantial fraction of those who endure the aftermath of stroke. The ramifications of insomnia following a stroke can further exacerbate cognitive and behavioural anomalies while hindering the process of neurological convalescence. While several randomised controlled trials (RCTs) have scrutinised the effects of hyperbaric oxygen therapy (HBOT) on poststroke insomnia, the advantages and drawbacks persist in a state of ambiguity. We advocate for a systematic review and meta-analysis of randomised clinical trials to comprehensively evaluate the effectiveness and safety of HBOT in the context of poststroke insomnia.

METHODS AND ANALYSIS

A systematic search will be conducted from nine major databases (PubMed, Web of Science, EMBASE, VIP Information Database, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, China Biomedical Literature Database and Wanfang Database, Physiotherapy Evidence Database (PEDro)) for HBOT for poststroke insomnia of RCTs. The search procedures will adhere to a rigorous approach, commencing from the inception date of each database and continuing until 1 November 2023, with inquiries conducted exclusively in English and Chinese. The primary outcome will focus on the alteration in the quality of sleep while secondary outcomes will encompass the evaluation of adverse events and the rate of reoccurrence. The process of selecting studies, extracting data and evaluating the quality of research will be carried out independently by two reviewers. The quality of the included literature will be assessed using the tools of the Cochrane Collaboration. Meta-analysis will be performed by using RevMan V.5.4 and STATA V.16.0.b software. Finally, the quality of evidence will be assessed using the Grading of Recommendations, Assessment, Development and Evaluation method.

ETHICS AND DISSEMINATION

As all data are derived from published investigations via databases without direct patient contact, ethical approval is obviated in this study. The scientific studies will be published in professional academic publications.

PROSPERO REGISTRATION NUMBER

CRD42023468442.

[Sleep disorders during pregnancy]

Pregnancy is associated with a number of physiological changes in a woman's body, which in turn affect the quality and duration of sleep. According to research, insomnia and other sleep disorders are associated with a high risk of adverse pregnancy outcomes, as well as postpartum complications. Understanding the mechanisms of sleep disorders during pregnancy is necessary to form an integrated approach in the management of this group of patients. The appointment of medicinal and non-medicinal therapies, as well as general recommendations for lifestyle correction in order to treat sleep disorders, is focused on the safe and prolific effect of a particular drug on the mother and fetus. This review also examined the safety profile of commonly used groups of drugs for sleep disorders during pregnancy.

Therapeutic dilemmas with benzodiazepines and Z-drugs: insomnia and anxiety disorders versus increased fall risk: a clinical review

PURPOSE

The aim of this clinical review was to summarise the existing knowledge on fall risk associated with benzodiazepines (BZDs) and Z-drugs in older people with focus on appropriate prescribing, including deprescribing.

METHODS

We conducted a literature search in June 2021 in PubMed and Embase with citation and reference checking. Personal reference libraries and international websites were also used. Keywords for the searches included "benzodiazepines", "Z-drugs", "falls", "deprescribing", "fall-risk-increasing-drugs", "inappropriate prescribing", "older people" and matching synonyms. We discuss use of BZDs and Z-drugs, potential fall-related adverse reactions, alternatives for and deprescribing of BZDs and Z-drugs in older persons.

RESULTS

BZDs and Z-drugs differ in fall-related adverse effect profile. They contribute to fall risk through orthostatic hypotension, dizziness and/or imbalance, sedation, muscular weakness, ataxia, etc. Fall incidents contribute significantly to mortality and morbidity. Therefore, there is a need for appropriate prescribing and use of BZDs and Z-drugs in older people. In practice, this means pertaining to a strict indication, strongly consider to non-pharmacological alternatives, limit use to the lowest dose and the shortest duration possible. Judicious deprescribing should be considered and encouraged as well. Practical resources, tools and algorithms are available to guide and assist clinicians in deprescribing BZDs and Z-drugs.

CONCLUSIONS

Prescribing BZDs and Z-drugs should be done in a well-considered way in fall-prone older people. A good overview and insight in the fall-related adverse effects of these drugs, as well as the availability of different strategies to increase the appropriate use, including deprescribing initiatives, can assist clinicians in clinical decision-making.

Understanding the mechanism of action and clinical effects of neuroactive steroids and GABAergic compounds in major depressive disorder

The pathophysiology of major depressive disorder (MDD) is thought to result from impaired connectivity between key brain networks. Gamma-aminobutyric acid (GABA) is the key inhibitory neurotransmitter in the brain, working primarily via GABA_A receptors, with an important role in virtually all physiologic functions in the brain. Some neuroactive steroids (NASs) are positive allosteric modulators (PAMs) of GABA_A receptors and potentiate phasic and tonic inhibitory responses via activation of synaptic and extrasynaptic GABA_A receptors, respectively. This review first discusses preclinical and clinical data that support the association of depression with diverse defects in the GABAergic system of neurotransmission. Decreased levels of GABA and NASs have been observed in adults with depression compared with healthy controls, while treatment with antidepressants normalized the altered levels of GABA and NASs. Second, as there has been intense interest in treatment approaches for depression that target dysregulated GABAergic neurotransmission, we discuss NASs approved or currently in clinical development for the treatment of depression. Brexanolone, an intravenous NAS and a GABA_A receptor PAM, is approved by the U.S. Food and Drug Administration for the treatment of postpartum depression (PPD) in patients 15 years and older. Other NASs include zuranolone, an investigational oral GABA_A receptor PAM, and PH10, which acts on nasal chemosensory receptors; clinical data to date have shown improvement in depressive symptoms with these investigational NASs in adults with MDD or PPD. Finally, the review discusses how NAS GABA_A receptor PAMs may potentially address the unmet need for novel and effective treatments with rapid and sustained antidepressant effects in patients with MDD.

Diazepam-Induced Down-Regulation of The Gabaa Receptor α1 Subunit, as Mediated by the Activation of L-Type Voltage-Gated Calcium Channel/Ca2+/Protein Kinase A Signaling Cascade

Benzodiazepines are among the most prescribed drug class worldwide to treat disorders such as anxiety, insomnia, muscle spasticity, and convulsive disorders, and to induce presurgical sedation. Although benzodiazepines exhibit a high therapeutic index and low toxicity in short-term treatments, prolonged administration induces tolerance to most of their therapeutic actions. The mechanism of this tolerance remains unclear. The central actions of benzodiazepines are mediated by binding to GABA_A receptors, which mediate most fast inhibitory transmission in the brain. The majority of GABA_A receptors are composed of two α-(1-6), two β-(1-3) and one γ-subunits (1-3). In a previous report, we demonstrated that the prolonged exposure of cerebrocortical neurons to diazepam produces a transcriptional repression of the GABA_A receptor α1 subunit gene via a mechanism dependent on the activation of L-type voltage-gated calcium channels (L-VGCCs). The results reported here confirm that the diazepam-induced downregulation of the α1 subunit is contingent upon calcium influx from extracellular space. In addition, this regulatory mechanism involves the activation of protein kinase A (PKA) and is accompanied by the activation of two transcription factors, the cAMP-response element-binding protein (CREB) and the inducible cAMP early repressor (ICER). Together, our results suggest that diazepam's activation of an L-VGCC/Ca²⁺/PKA/CREB-ICER signaling pathway is responsible for the regulation of GABA_A receptors. This elucidation of the intracellular signaling cascade activated by a prolonged benzodiazepine exposure, itself potentially involved in the development of tolerance, may contribute to locating molecular targets for future therapeutic interventions.

GABAergic Effects of Etifoxine and Alprazolam Assessed by Double Pulse TMS

INTRODUCTION

There is a need for novel anxiolytics with improved side effect profiles compared to benzodiazepines. A promising candidate with alternative pharmacodynamics is the translocator protein ligand, etifoxine.

METHODS

To get further insight into its mechanisms of action and side effects compared to the benzodiazepine alprazolam, we performed a double-blind, placebo-controlled, repeated-measures study in 36 healthy male subjects. Participants were examined for trait anxiety and side effects and underwent repeated transcranial magnetic stimulation (TMS) assessments, including motor evoked potentials (MEP), short intracortical inhibition (SICI), intracortical facilitation (ICF), and cortical silent period (CSP).

RESULTS

We observed attenuation of MEPs by alprazolam but not by etifoxine. SICI was not significantly affected by alprazolam or etifoxine. However, the response pattern indicated a lowered SICI threshold after the administration of etifoxine and alprazolam compared to the placebo. ICF and CSP were influenced by neither medication. Alprazolam led to higher sedation and subjective impairment of concentration compared to etifoxine. Individual anxiety trait scores did not affect TMS parameters.

DISCUSSION

This study indicated a favorable side effect profile of etifoxine in healthy volunteers. Moreover, it revealed differential GABA-related effects on neuromuscular function by means of TMS. The side effects and TMS profile of etifoxine are compatible with the involvement of neurosteroidogenesis and a predominant α3 subunit modulation compared to alprazolam.

Anhedonia modulates benzodiazepine and opioid demand among persons in treatment for opioid use disorder

Background

Benzodiazepine (BZD) misuse is a significant public health problem, particularly in conjunction with opioid use, due to increased risks of overdose and death. One putative mechanism underlying BZD misuse is affective dysregulation, via exaggerated negative affect (e.g., anxiety, depression, stress-reactivity) and/or impaired positive affect (anhedonia). Similar to other misused substances, BZD consumption is sensitive to price and individual differences. Although purchase tasks and demand curve analysis can shed light on determinants of substance use, few studies have examined BZD demand, nor factors related to demand.

Methods

This ongoing study is examining simulated economic demand for alprazolam (among BZD lifetime misusers based on self-report and DSM-5 diagnosis; n = 23 total; 14 male, 9 female) and each participant's preferred-opioid/route using hypothetical purchase tasks among patients with opioid use disorder (n = 59 total; 38 male, 21 female) who are not clinically stable, i.e., defined as being early in treatment or in treatment longer but with recent substance use. Aims are to determine whether: (1) BZD misusers differ from never-misusers on preferred-opioid economic demand, affective dysregulation (using questionnaire and performance measures), insomnia/behavioral alertness, psychiatric diagnoses or medications, or urinalysis results; and (2) alprazolam demand among BZD misusers is related to affective dysregulation or other measures.

Results

Lifetime BZD misuse is significantly (p < 0.05) related to current major depressive disorder diagnosis, opioid-negative and methadone-negative urinalysis, higher trait anxiety, greater self-reported affective dysregulation, and younger age, but not preferred-opioid demand or insomnia/behavioral alertness. Alprazolam and opioid demand are each significantly positively related to higher anhedonia and, to a lesser extent, depression symptoms but no other measures of negative-affective dysregulation, psychiatric conditions or medications (including opioid agonist therapy or inpatient/outpatient treatment modality), or sleep-related problems.

Conclusion

Anhedonia (positive-affective deficit) robustly predicted increased BZD and opioid demand; these factors could modulate treatment response. Routine assessment and effective treatment of anhedonia in populations with concurrent opioid and sedative use disorder may improve treatment outcomes.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03696017, identifier NCT03696017.

Voltage-clamp evidence of GABAA receptor subunit-specific effects: pharmacodynamic fingerprint of chlornordiazepam, the major active metabolite of mexazolam, as compared to alprazolam, bromazepam, and zolpidem

BACKGROUND

Anxiolytic benzodiazepines, due to their clinical effectiveness, are one of the most prescribed drugs worldwide, despite being associated with sedative effects and impaired psychomotor and cognitive performance. Not every GABA_A receptor functions in the same manner. Those containing α1 subunits are associated with sleep regulation and have a greater effect on the sedative-hypnotic benzodiazepines, whereas those containing α2 and/or α3 subunits are associated with anxiety phenomena and have a greater effect on the anxiolytic benzodiazepines. Therefore, characterization of the selectivity profile of anxiolytic drugs could translate into a significant clinical impact.

METHODS

The present study pharmacodynamically evaluated chlornordiazepam, the main active metabolite of mexazolam, upon GABA_A receptors containing α2 and/or α3, anxiety-related, and those containing an α1 subunit, associated with sleep modulation.

RESULTS

As shown by whole-cell patch-clamp data, chlornordiazepam potentiated GABA-evoked current amplitude in α2 and α3 containing receptors without changing the current amplitude in α1 containing receptors. However, current decay time increased, particularly in GABA_A receptors containing α1 subunits. In contrast, other anxiolytic benzodiazepines such as alprazolam, bromazepam, and zolpidem, all increased currents associated with GABA_A receptors containing the α1 subunit.

CONCLUSIONS

This novel evidence demonstrates that mexazolam (through its main metabolite chlornordiazepam) has a "pharmacodynamic fingerprint" that correlates better with an anxiolytic profile and fewer sedative effects, when compared to alprazolam, bromazepam and zolpidem, explaining clinical trial outcomes with these drugs. This also highlights the relevance of the pharmacological selectivity over GABA_A receptor subtypes in the selection of benzodiazepines, in addition to their clinical performance and pharmacokinetic characteristics.

Pronounced antiseizure activity of the subtype-selective GABAA positive allosteric modulator darigabat in a mouse model of drug-resistant focal epilepsy

Aim

Darigabat is an α2/3/5 subunit‐selective positive allosteric modulator of GABA_A receptors that has demonstrated broad‐spectrum activity in several preclinical models of epilepsy as well as in a clinical photoepilepsy trial. The objective here was to assess the acute antiseizure effect of darigabat in the mesial temporal lobe epilepsy (MTLE) mouse model of drug‐resistant focal seizures.

Methods

The MTLE model is generated by single unilateral intrahippocampal injection of low dose (1 nmole) kainic acid in adult mice, and subsequent epileptiform activity is recorded following implantation of a bipolar electrode under general anesthesia. After a period of epileptogenesis (~4 weeks), spontaneous and recurrent hippocampal paroxysmal discharges (HPD; focal seizures) are recorded using intracerebral electroencephalography. The number and cumulated duration of HPDs were recorded following administration of vehicle (PO), darigabat (0.3–10 mg kg⁻¹, PO), and positive control diazepam (2 mg kg⁻¹, IP).

RESULTS

Darigabat dose‐dependently reduced the expression of HPDs, demonstrating comparable efficacy profile to diazepam at doses of 3 and 10 mg kg⁻¹.

CONCLUSIONS

Darigabat exhibited a robust efficacy profile in the MTLE model, a preclinical model of drug‐resistant focal epilepsy. A Phase II proof‐of‐concept placebo‐controlled, adjunctive‐therapy trial (NCT04244175) is ongoing to evaluate efficacy and safety of darigabat in patients with drug‐resistant focal seizures.

Efficacy and safety evaluation of bright light therapy in patients with post-stroke insomnia: A protocol for systematic review and meta-analysis

BACKGROUND

Post-stroke insomnia (PSI) is a common and severe illness among the complications of stroke. Although there are plenty of drugs currently used for PSI treatment, they generate several side effects and other problems. Bright light therapy (BLT) is thought to be relatively safe and effective in treating PSI patients. Despite this, there is still a lack of systematic review on BLT in the treatment of PSI. Allowing for this, the aim of this study is to assess the efficacy and safety of BLT for PSI.

METHODS

The meta-analysis and systematic review will perform a comprehensive electronic search for items fulfilling the required criteria in Web of Science, Google Scholar, Wan Fang database, MEDLINE, Baidu Scholar, PubMed, SinoMed, Embase, Chinese Biomedical Literature Database (CBM), China national knowledge infrastructure database (CNKI), Cochrane Library Central Register of Controlled Trials (CENTRAL), and Wei Pu database from establishment to January 1, 2022. We will select articles, collect data, and assess the methodology quality. And we will set the primary outcome and secondary outcomes in this research. RevMan 5.3 software will be used to analyze the data for this investigation.

RESULTS

The work of this research will be published in peer-reviewed scientific journals.

CONCLUSION

The aim of this study is to assess the efficacy and safety of BLT for PSI and present robust scientific evidence concerning BLT for PSI.

REGISTRATION

INPLASY2021100065.

Proceedings of the 2020 Epilepsy Foundation Pipeline Conference: Emerging Drugs and Devices

From August 27-28, 2020 the Epilepsy Foundation hosted the Pipeline Conference, exploring emerging issues related to antiepileptic drug and device development. The conference featured epilepsy therapeutic companies and academic laboratories developing drugs for focal epilepsies, innovations for rare and ultra-rare diseases, and devices both in clinical trials and approved for use. In this paper, we outline the virtual presentations by the authors, including novel data from their development pipeline.

Cognitive Behavioral Therapy and Acceptance and Commitment Therapy for the Discontinuation of Long-Term Benzodiazepine Use in Insomnia and Anxiety Disorders

Benzodiazepines have proven to be highly effective for treating insomnia and anxiety. Although considered safe when taken for a short period of time, a major risk–benefit dilemma arises in the context of long-term use, relating to addiction, withdrawal symptoms, and potential side effects. For these reasons, benzodiazepines are not recommended for treating chronic sleep disorders, anxiety disorders, nor for people over the age of 65, and withdrawal among long-term users is a public health issue. Indeed, only 5% of patients manage to discontinue using these drugs on their own. Even with the help of a general practitioner, this rate does not exceed 25 to 30% of patients, of which approximately 7% manage to remain drug-free in the long term. Cognitive Behavioral Therapies (CBT) offer a crucial solution to this problem, having been shown to increase abstinence success to 70–80%. This article examines traditional and novel CBT techniques in this regard, such as Acceptance and Commitment Therapy, which address both the underlying condition (insomnia/anxiety) and the substance-related disorder. The theoretical framework and evidence supporting the use of these approaches are reviewed. Finally, current research gaps are discussed, and key research perspectives are proposed.

Gamma-Aminobutyric Acid (GABA) Inhibits α-Melanocyte-Stimulating Hormone-Induced Melanogenesis through GABAA and GABAB Receptors

Gamma-aminobutyric acid (GABA) is considered the primary inhibitory neurotransmitter in the human cortex. However, whether GABA regulates melanogenesis has not been comprehensively elucidated. In this study, we reveal that GABA (20 mM) significantly inhibited α-melanocyte-stimulating hormone (α-MSH)-induced extracellular (from 354.9% ± 28.4% to 126.5% ± 16.0%) and intracellular melanin contents (from 236.7% ± 11.1% to 102.7% ± 23.1%) in B16F10 melanoma cells, without inducing cytotoxicity. In addition, α-MSH-induced hyperpigmentation in zebrafish larvae was inhibited from 246.3% ± 5.4% to 116.3% ± 3.1% at 40 mM GABA, displaying no apparent cardiotoxicity. We also clarify that the GABA-mediated antimelanogenic properties were related to the direct inhibition of microphthalmia-associated transcription factor (MITF) and tyrosinase expression by inhibiting cyclic adenosine monophosphate (cAMP) and cAMP response element-binding protein (CREB). Furthermore, under α-MSH stimulation, GABA-related antimelanogenic effects were mediated through the GABA_A and GABA_B receptors, with subsequent inhibition of Ca²⁺ accumulation. In B16F10 melanoma cells and zebrafish larvae, pretreatment with bicuculline, a GABA_A receptor antagonist, and CGP 46381, a GABA_B receptor antagonist, reversed the antimelanogenic effect of GABA following α-MSH treatment by upregulating Ca²⁺ accumulation. In conclusion, our results indicate that GABA inhibits α-MSH-induced melanogenesis. Hence, in addition to the health benefits of GABA in the central nervous system, it could ameliorate hyperpigmentation disorders.

Increased levels of α4-containing GABAA receptors in focal cortical dysplasia: A possible cause of benzodiazepine resistance

Benzodiazepines are the first choice of anti-epileptic drugs used to treat seizures. However, it has been seen that their efficacy decreases with time leading to drug insensitivity, plausibly caused by an alteration in the expression of the benzodiazepine biding site on GABA_A receptors. This study was designed to investigate if the differential expression of GABA_A receptor subunits α1/α4/γ2/δ across the postsynaptic sites could contribute to benzodiazepine resistance in patients with focal cortical dysplasia (FCD), the most common cause of drug resistant epilepsy in pediatric population. Differential gene and cellular expression of GABA_A receptor subunits α1, α4, γ2 and δ were evaluated and validated using qPCR and immunohistochemistry. Whole cell patch clamp studies were performed on pyramidal neurons of resected cortical FCD samples to measure the spontaneous GABA_A receptor activity. Upregulation of α4-and γ2-subunits containing GABA_A receptors were observed at both mRNA and protein level. α1-and δ-subunits containing GABA_A receptors did not show any significant changes. Flumazenil treatment did not affect the kinetics of GABAergic events in FCD; however, it significantly reduced the frequency and amplitude of spontaneous GABAergic activity in non-seizure control samples. Our results demonstrate the enhanced expression of α4-containing GABA_A receptors and GABAergic activity in pyramidal neurons which in turn may contribute to benzodiazepine resistance in FCD patients.

Looking for Novelty in an "Old" Receptor: Recent Advances Toward Our Understanding of GABAARs and Their Implications in Receptor Pharmacology

Diverse populations of GABA_A receptors (GABA_ARs) throughout the brain mediate fast inhibitory transmission and are modulated by various endogenous ligands and therapeutic drugs. Deficits in GABA_AR signaling underlie the pathophysiology behind neurological and neuropsychiatric disorders such as epilepsy, anxiety, and depression. Pharmacological intervention for these disorders relies on several drug classes that target GABA_ARs, such as benzodiazepines and more recently neurosteroids. It has been widely demonstrated that subunit composition and receptor stoichiometry impact the biophysical and pharmacological properties of GABA_ARs. However, current GABA_AR-targeting drugs have limited subunit selectivity and produce their therapeutic effects concomitantly with undesired side effects. Therefore, there is still a need to develop more selective GABA_AR pharmaceuticals, as well as evaluate the potential for developing next-generation drugs that can target accessory proteins associated with native GABA_ARs. In this review, we briefly discuss the effects of benzodiazepines and neurosteroids on GABA_ARs, their use as therapeutics, and some of the pitfalls associated with their adverse side effects. We also discuss recent advances toward understanding the structure, function, and pharmacology of GABA_ARs with a focus on benzodiazepines and neurosteroids, as well as newly identified transmembrane proteins that modulate GABA_ARs.

Potential modulating effect of the Ascaris suum nicotinic acetylcholine receptor (nAChR) by compounds GSK575594A, diazepam and flumazenil discovered by structure-based virtual screening approach

Parasitic infections are a widespread health problem and research of novel anthelmintic compounds is of the utmost importance. In this study we performed a virtual screening campaign by coupling ligand-based pharmacophore, homology modeling and molecular docking. The virtual screening campaign was conducted using a joined pool of the Drugbank database and a library of purchasable compounds in order to identify drug like compounds with similar pharmacological activity. Our aim was to identify compounds with a potential antihelmintic modulatory effect on nicotinic acetylcholine receptors (nAChR). We derived a 3D pharmacophore model based on the chemical features of known Ascaris suum nAChR modulators. To evaluate the in silico predictions, we tested selected hit compounds in contraction assays using somatic muscle flaps of the Ascaris suum neuromuscular tissue. We tested the modulatory effects of GSK575594A, diazepam and flumazenil hit compounds on nematode contractions induced by acetyl choline (ACh). The compound GSK575594A (3 μM) increased the E_max by 21 % with the EC₅₀ dose ratio of 0.96. Diazepam (100 μM) decreased the E_max by 15 % (1.11 g to 0.95 g) with the EC₅₀ ratio of 1.42 (shifted to the left from 11.25 to 7.93). Flumazenil decreased the EC₅₀ value (from 11.22 μM to 4.88 μM) value showing dose ratio of 2.30, and increased the E_max by 4 % (from 1.54 g to 1.59 g). The observed biological activity was rationalized by molecular docking calculations. Docking scores were calculated against several binding sites within the Ascaris suum homology model. We constructed the homology model using the ACR-16 subunit sequence. The compound GSK575594A showed strong affinity for the intersubunit allosteric binding site within the nAChR transmembrane domain. The binding modes of diazepam and flumazenil suggest that these compounds have a comparable affinity for orthosteric and allosteric nAChR binding sites. The selected hit compounds displayed potential for further optimization as lead compounds. Therefore, such compounds may be useful in neutralizing the growing resistance of parasites to drugs, either alone or in combination with existing conventional anthelmintics.

Possible interplay between the theories of pharmacoresistant epilepsy

Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.

5-[Aryloxypyridyl (or nitrophenyl)]-4H-1,2,4-triazoles as novel flexible benzodiazepine analogues: Synthesis, receptor binding affinity and lipophilicity-dependent anti-seizure onset of action

A new series of 5-(2-aryloxy-4-nitrophenyl)-4H-1,2,4-triazoles and 5-(2-aryloxy-3-pyridyl)-4H-1,2,4-triazoles, possessing C-3 thio or alkylthio substituents, was synthesized and evaluated for their benzodiazepine receptor affinity and anti-seizure activity. These analogues revealed similar to significantly superior affinity to GABA_A/benzodiazepine receptor complex (IC₅₀ values of 0.04-4.1 nM), relative to diazepam as the reference drug (IC₅₀ value of 2.4 nM). To determine the onset of anti-seizure activity, the time-dependent effectiveness of i.p. administration of compounds on pentylenetetrazole induced seizure threshold was studied and a very good relationship was observed between the lipophilicity (cLogP) and onset of action of studied analogues (r² = 0.964). The minimum effective dose of the compounds, determined at the time the analogues showed their highest activity, was demonstrated to be 0.025-0.1 mg/kg, relative to diazepam (0.025 mg/kg).

Detoxification Improves Multidomain Cognitive Dysfunction in High-Dose Benzodiazepine Abusers

Purpose

High-dose benzodiazepines (BZDs) abuse has been documented to cause multidomain cognitive dysfunction. We explored whether cognitive abnormalities to high-dose BZD abuse might be reversed by detoxification with slow subcutaneous infusion of flumazenil.

Methods

We recruited 96 patients consecutively admitted to the Department of Internal Medicine, Addiction Medicine Unit, Verona University Hospital, Italy for detoxification from high-dose BZD dependence. After selection for inclusion and exclusion criteria, 50 patients (23 men, 27 women; age 42.7 ± 10.3 years) were included. They underwent a comprehensive neuropsychological battery to explore verbal memory, visuospatial memory, working memory, attention, and executive functions 28–30 days prior to admission for detoxification (T0) and at the end of detoxification, i.e., 7 days after admission (T1). A group of 50 healthy adults (24 men, 26 women; mean age 44.5 ± 12.8 years) matched for age, sex, and education served as controls.

Results

At T0, patients scored significantly worse than healthy controls in all the neuropsychological tests. Depression and anxiety scores were associated with impaired verbal memory at T0 in patients. T1–T0 comparison showed improved performances in all neuropsychological tests after the end of detoxification in patients.

Conclusion

We confirmed that all neuropsychological domains were significantly and profoundly impaired by high-dose BZD abuse and documented that cognitive abnormalities improved after detoxification with slow subcutaneous infusion of flumazenil.

Translational Studies in the Complex Role of Neurotransmitter Systems in Anxiety and Anxiety Disorders

Discovery of innovative anxiolytics is severely hampering. Existing anxiolytics are developed decades ago and are still the therapeutics of choice. Moreover, lack of new drug targets forecasts a severe jeopardy in the future treatment of the huge population of CNS-diseased patients. We simply lack the knowledge on what is wrong in brains of anxious people (normal and diseased). Translational research, based on interacting clinical and preclinical research, is extremely urgent. In this endeavor, genetic and genomic approaches are part of the spectrum of contributing factors. We focus on three druggable targets: serotonin transporter, 5-HT_1A, and GABA_A receptors. It is still uncertain whether and how these targets are involved in normal and diseased anxiety processes. For serotonergic anxiolytics, the slow onset of action points to indirect effects leading to plasticity changes in brain systems leading to reduced anxiety. For GABA_A benzodiazepine drugs, acute anxiolytic effects are found indicating primary mechanisms directly influencing anxiety processes. Close translational collaboration between fundamental academic and discovery research will lead to badly needed breakthroughs in the search for new anxiolytics.

High-dose lormetazepam dependence: strange case of Dr. Jekyll and Mr. Hyde

High-dose benzodiazepine (BZD) abuse is emerging as a substance use disorder (SUD). The aim of the study is to explore the impact of high-dose lormetazepam (LMZ) abuse and the characteristics of patients affected by this SUD in a tertiary referral addiction unit. We have retrospectively evaluated 1112 patients admitted to the Addiction Medicine Unit, Verona University Hospital, Italy for detoxification from high-dose BZD dependence. LMZ was the most common BZD, with an increasing prevalence from January 2003 to June 2018. Socio-demographic (more women; higher age and education) and clinical features (higher daily diazepam dosage equivalent, BZD abuse duration, age of first BZD intake; BZD prescribed more frequently for sleep disorders; less frequent history of other SUDs, previous/active alcohol, previous opioids abuse; more frequent overall major psychiatric diseases and major depression; less-frequent bipolar disorders and other psychoses, personality disorders, and more than one psychiatric disease) of LMZ vs. other BZD abusers significantly differed. 96.7% LMZ abusers took oral solution, while two-thirds of other BZD abusers took tablets. Oral solution, BZD abuse duration and prescription of BZD for sleep disorders increased, while history of other SUDs, previous/active alcohol and active cannabinoids SUD reduced the risk of high-dose LMZ vs. other BZDs abuse. The large prevalence of high-dose LMZ abusers in Italy may be strongly related to the availability and characteristics of oral formulation that may transform the innocuous Dr. Jekyll tablets into an evil Mr. Hyde. Restriction to the market of LMZ oral formulation might reduce the risk of high-dose abuse.

Novel pharmacological targets in drug development for the treatment of anxiety and anxiety-related disorders

Current medication for anxiety disorders is suboptimal in terms of efficiency and tolerability, highlighting the need for improved drug treatments. In this review an overview of drugs being studied in different phases of clinical trials for their potential in the treatment of fear-, anxiety- and trauma-related disorders is presented. One strategy followed in drug development is refining and improving compounds interacting with existing anxiolytic drug targets, such as serotonergic and prototypical GABAergic benzodiazepines. A more innovative approach involves the search for compounds with novel mechanisms of anxiolytic action using the growing knowledge base concerning the relevant neurocircuitries and neurobiological mechanisms underlying pathological fear and anxiety. The target systems evaluated in clinical trials include glutamate, endocannabinoid and neuropeptide systems, as well as ion channels and targets derived from phytochemicals. Examples of promising novel candidates currently in clinical development for generalised anxiety disorder, social anxiety disorder, panic disorder, obsessive compulsive disorder or post-traumatic stress disorder include ketamine, riluzole, xenon with one common pharmacological action of modulation of glutamatergic neurotransmission, as well as the neurosteroid aloradine. Finally, compounds such as D-cycloserine, MDMA, L-DOPA and cannabinoids have shown efficacy in enhancing fear-extinction learning in humans. They are thus investigated in clinical trials as an augmentative strategy for speeding up and enhancing the long-term effectiveness of exposure-based psychotherapy, which could render chronic anxiolytic drug treatment dispensable for many patients. These efforts are indicative of a rekindled interest and renewed optimism in the anxiety drug discovery field, after decades of relative stagnation.