Activation-induced regulation of GABAA receptors: Is there a link with the molecular basis of benzodiazepine tolerance?

Development of SV2A Ligands for Epilepsy Treatment: A Review of Levetiracetam, Brivaracetam, and Padsevonil

Epilepsy is a common neurological disorder that is primarily treated with antiseizure medications (ASMs). Although dozens of ASMs are available in the clinic, approximately 30% of epileptic patients have medically refractory seizures; other limitations in most traditional ASMs include poor tolerability and drug-drug interactions. Therefore, there is an urgent need to develop alternative ASMs. Levetiracetam (LEV) is a first-line ASM that is well tolerated, has promising efficacy, and has little drug-drug interaction. Although it is widely accepted that LEV acts through a unique therapeutic target synaptic vesicle protein (SV) 2A, the molecular basis of its action remains unknown. Even so, the next-generation SV2A ligands against epilepsy based on the structure of LEV have achieved clinical success. This review highlights the research and development (R&D) process of LEV and its analogs, brivaracetam and padsevonil, to provide ideas and experience for the R&D of novel ASMs.

Diazepam at environmentally relevant concentrations disturbed social interactions and brain neurotransmitters in adult Japanese medaka (Oryzias latipes)

Pollution by diazepam (DZP) is increasingly recognized as a major threat to aquatic organisms, but knowledge about its potential risk to fish is still limited. In this study, we exposed female and male Japanese medaka (Oryzias latipes) to environmentally relevant DZP (0.8 and 8 µg/L) for 28 days and investigated variation in their behavior (on days 7, 14, and 28) and brain neurotransmitter levels (on day 28). The results showed that DZP could be accumulated in the brain and gonads in Japanese medaka. When two fish of the same sex were placed in an aquarium, DZP exposure exhibited typical sedative effects on females (on day 7) and males (on days 7 and 14). However, these sedative effects on both sexes were no longer present after 28 days of exposure. Exposure to DZP induced sex-specific impacts on the social interactions of medaka on days 7, 14, and 28 of exposure in a time-dependent manner. When both sexes were placed into an aquarium in a ratio of 1:1, DZP could significantly alter their locomotor activity and social interaction on days 14 and 28 of the exposure. After 28 days of exposure, DZP significantly altered the levels of several neurotransmitters in the brain of medaka, also in sex-specific manners. The alterations in dopamine and serotonin levels exhibited significant correlations with the increased social interaction between females. At the same time, that of γ-aminobutyric acid significantly correlated to the decreased social interaction between males. Our findings suggest that chronic exposure to DZP, even at environmentally relevant concentrations, can accumulate in the brains and gonads of fish, and alter their behaviors by mediating brain neurotransmitter levels, which may further disturb their reproduction and population dynamics.

Insomnia Medication Use by University Students: A Systematic Review

Problematic sleep or insomnia has been a recognised issue for many individuals in society, and university students can be of particular concern due to unique academic pressures. A systematic review was designed to summarise the current evidence about the extent of insomnia medication used by university students and identify characteristics of those more willing to use medication to manage insomnia. Searches were undertaken using Psych INFO, PubMed, Embase, and Web of Science, resulting in 25 eligible studies across multiple countries between 1994 and 2020. The prevalence of sleep medication use by students varied widely, from 2% to 41.2%, with an average of 13.1%. Female gender, students experiencing poor sleep, smoking, drinking stimulant beverages, and undertaking fewer physical activities were associated with the use of insomnia medication. Insomnia medication use exists within university student populations but appears to vary considerably worldwide; identifying multiple population characteristics associated with such use would offer opportunities to identify and support those affected.

Two Cases of Inadequate Response to Remimazolam

We report the inadequate efficacy of remimazolam in two patients undergoing long-term benzodiazepine analog therapy. Remimazolam is a recently developed ultrashort-acting benzodiazepine. It is primarily used as an anesthetic in surgical procedures, as it has minimal effect on cardiac function and antagonists are available. It is expected to become more widely used in the future. On the other hand, similar to other benzodiazepines, benzodiazepine tolerance can also pose a challenge with remimazolam. Herein, we report two cases who were taking long-term oral benzodiazepine analogs. One patient did not fall asleep despite a sufficient dose of remimazolam and required a change to propofol. The other patient required a high dose of remimazolam to fall asleep; however, multiple signs of arousal were noted intraoperatively. Our findings suggest that remimazolam may not be an ideal anesthetic in long-term benzodiazepine analog users. Comprehensive assessment of preoperative medications and careful monitoring of intraoperative sedation levels are necessary. Furthermore, it may be advisable to consider the use of alternative agents such as propofol.

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.

A randomized, double-blind, placebo-controlled phase II trial to explore the effects of a GABAA-α5 NAM (basmisanil) on intellectual disability associated with Down syndrome

Background

There are currently no pharmacological therapies to address the intellectual disability associated with Down syndrome. Excitatory/inhibitory imbalance has been hypothesized to contribute to impairments in cognitive functioning in Down syndrome. Negative modulation of the GABA_A-α5 receptor is proposed as a mechanism to attenuate GABAergic function and restore the excitatory/inhibitory balance.

Methods

Basmisanil, a selective GABA_A-α5 negative allosteric modulator, was evaluated at 120 mg or 240 mg BID (80 or 160 mg for 12–13 years) in a 6-month, randomized, double-blind, placebo-controlled phase II trial (Clematis) for efficacy and safety in adolescents and young adults with Down syndrome. The primary endpoint was based on a composite analysis of working memory (Repeatable Battery for the Assessment of Neuropsychological Scale [RBANS]) and independent functioning and adaptive behavior (Vineland Adaptive Behavior Scales [VABS-II] or the Clinical Global Impression-Improvement [CGI-I]). Secondary measures included the Behavior Rating Inventory of Executive Functioning-Preschool (BRIEF-P), Clinical Evaluation of Language Fundamentals (CELF-4), and Pediatric Quality of Life Inventory (Peds-QL). EEG was conducted for safety monitoring and quantitatively analyzed in adolescents.

Results

Basmisanil was safe and well-tolerated; the frequency and nature of adverse events were similar in basmisanil and placebo arms. EEG revealed treatment-related changes in spectral power (increase in low ~ 4-Hz and decrease in high ~ 20-Hz frequencies) providing evidence of functional target engagement. All treatment arms had a similar proportion of participants showing above-threshold improvement on the primary composite endpoint, evaluating concomitant responses in cognition and independent functioning (29% in placebo, 20% in low dose, and 25% in high dose). Further analysis of the individual measures contributing to the primary endpoint revealed no difference between placebo and basmisanil-treated groups in either adolescents or adults. There were also no differences across the secondary endpoints assessing changes in executive function, language, or quality of life.

Conclusions

Basmisanil did not meet the primary efficacy objective of concomitant improvement on cognition and adaptive functioning after 6 months of treatment, despite evidence for target engagement. This study provides key learnings for future clinical trials in Down syndrome.

Trial registration

The study was registered on December 31, 2013, at clinicaltrials.gov as NCT02024789.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-022-09418-0.

GABAA receptor subtypes and benzodiazepine use, misuse, and abuse

Benzodiazepines have been in use for over half a century. While they remain highly prescribed, their unfavorable side-effect profile and abuse liability motivated a search for alternatives. Most of these efforts focused on the development of benzodiazepine-like drugs that are selective for specific GABA_A receptor subtypes. While there is ample evidence that subtype-selective GABA_A receptor ligands have great potential for providing symptom relief without typical benzodiazepine side-effects, it is less clear whether subtype-selective targeting strategies can also reduce misuse and abuse potential. This review focuses on the three benzodiazepine properties that are relevant to the DSM-5-TR criteria for Sedative, Hypnotic, or Anxiolytic Use Disorder, namely, reinforcing properties of benzodiazepines, maladaptive behaviors related to benzodiazepine use, and benzodiazepine tolerance and dependence. We review existing evidence regarding the involvement of different GABA_A receptor subtypes in each of these areas. The reviewed studies suggest that α1-containing GABA_A receptors play an integral role in benzodiazepine-induced plasticity in reward-related brain areas and might be involved in the development of tolerance and dependence to benzodiazepines. However, a systematic comparison of the contributions of all benzodiazepine-sensitive GABA_A receptors to these processes, a mechanistic understanding of how the positive modulation of each receptor subtype might contribute to the brain mechanisms underlying each of these processes, and a definitive answer to the question of whether specific chronic modulation of any given subtype would result in some or all of the benzodiazepine effects are currently lacking from the literature. Moreover, how non-selective benzodiazepines might lead to the maladaptive behaviors listed in DSM and how different GABA_A receptor subtypes might be involved in the development of these behaviors remains unexplored. Considering the increasing burden of benzodiazepine abuse, the common practice of benzodiazepine misuse that leads to severe dependence, and the current efforts to generate side-effect free benzodiazepine alternatives, there is an urgent need for systematic, mechanistic research that provides a better understanding of the brain mechanisms of benzodiazepine misuse and abuse, including the involvement of specific GABA_A receptor subtypes in these processes, to establish an informed foundation for preclinical and clinical efforts.

Case report: Chronological symptom profile after cessation of overdose zolpidem in a patient with comorbid bipolar disorder-from anxiety, craving, paresthesia and influenza-like symptoms to seizures and hallucinations

INTRODUCTION

Insomnia is a major public health problem that determines the quality of life. Among the many causes of insomnia, psychological factors have an important influence on the process, duration of insomnia, help-seeking behavior, and treatment choice. Regarding medical treatment, zolpidem is always chosen to treat acute and transient insomnia due to its few side effects. Although some randomized controlled trials have verified its safety, zolpidem abuse and withdrawal reactions have been reported in recent years.

CASE REPORT

A 25-year-old unmarried man with a college degree who worked as a graphic designer was referred and admitted to the inpatient ward for a chief complaint of "alternative episodes of lowering and elevation of mood for 10 years, overdosage use of zolpidem for two years." He underwent a time-dependent withdrawal reaction after admission. It was characterized by rebound insomnia, anxiety, craving, skin paresthesia, influenza-like symptoms, tonic-clonic-type seizures, and hallucinations. At the 1-year follow-up, he did not exhibit any remaining withdrawal symptoms.

DISCUSSION

The acute cessation of overdosage zolpidem use causes a series of withdrawal symptoms that manifest in chronological order. Additionally, long-term benzodiazepine exposure has potential influences on zolpidem dependence/tolerance. However, patients with a history of abuse or dependence, or mental disorders seem to be at risk of drug abuse. Clinicians should be alert to the potential for zolpidem dependence and addiction. Once the acute cessation of overdosage zolpidem use occurs, the potential of the withdrawal reaction needs to be considered and addressed properly.

Tolerance and dependence following chronic alprazolam treatment in rhesus monkeys: Role of GABAA receptor subtypes

BACKGROUND

To assess GABA_A receptor subtypes involved in benzodiazepine tolerance and dependence, we evaluated the ability of subtype-selective and non-selective ligands to substitute for (i.e., produce "cross-tolerance") or precipitate withdrawal during chronic alprazolam treatment.

METHODS

Four female rhesus monkeys (Macaca mulatta) were implanted with chronic intravenous catheters and administered alprazolam (1.0 mg/kg every 4 h). Following 14+ days of chronic alprazolam, acute administration of selected doses of non-selective and subtype-selective ligands were substituted for, or administered with, alprazolam, followed by quantitative behavioral observations. The ligands included alprazolam and midazolam (positive modulators, non-selective), zolpidem (positive modulator, preferential affinity for α1-containing GABA_A receptors), HZ-166 (positive modulator, preferential efficacy at α2- and α3-containing GABA_A receptors), and βCCT (antagonist, preferential affinity for α1-containing GABA_A receptors).

RESULTS

Acutely, alprazolam and midazolam both induced observable ataxia along with a mild form of sedation referred to as "rest/sleep posture" at a lower dose (0.1 mg/kg, i.v.), whereas at a higher dose (1.0 mg/kg, i.v.), induced deep sedation and observable ataxia. With chronic alprazolam treatment, observable ataxia and deep sedation were reduced significantly, whereas rest/sleep posture was unchanged or emerged. Zolpidem showed a similar pattern of effects, whereas no behaviors engendered by HZ-166 were changed by chronic alprazolam. Administration of βCCT, but not HZ-166, resulted in significant withdrawal signs.

CONCLUSIONS

These results are consistent with a role for α1-containing GABA_A receptor subtypes in tolerance and dependence observed with chronic alprazolam, although other receptors may be involved in the withdrawal syndrome.

The effects of a high eicosapentaenoic acid multinutrient supplement on measures of stress, anxiety and depression in young adults: Study protocol for NutriMOOD, a randomised double-blind placebo-controlled trial

Anxiety disorders affect nearly 20% of young adults aged 18-29 years. First-line treatment for anxiety disorders comprises pharmacotherapy and Cognitive Behavioural Therapy, options often criticised for their low efficacy and safety. In contrast, fish-oil-based supplements comprising omega-3 polyunsaturated fatty acids and supporting nutrients are gaining recognition as safe and effective alternatives. Here we present the protocol for a randomised, double-blind, placebo-controlled trial investigating the effects of a high eicosapentaenoic acid multinutrient supplement on validated measures of anxiety and depression in healthy university students experiencing non-clinical levels of anxiety and depression. The primary outcome is improvement in anxiety compared to the placebo group assessed via the Generalised Anxiety Disorder Assessment-7 scale. The participants will be randomised to active treatment comprising a daily dose of 1125 mg eicosapentaenoic acid, 441 mg docosahexaenoic acid, 330 mg magnesium and 7.5 mg vitamin E, or placebo, for 24 weeks, and will complete validated questionnaires and tablet-based tasks sensitive to mood at baseline and end of intervention. Circulating fatty acids and key biomarkers will also be assessed. The students will be genotyped for polymorphisms thought to influence the relationship between long-chain omega-3 polyunsaturated fatty acids and affect. Trial registration; ClinicalTrials.gov, NCT04844034.

Regulation of GABAA Receptors Induced by the Activation of L-Type Voltage-Gated Calcium Channels

GABA_A receptors are pentameric ion channels that mediate most synaptic and tonic extrasynaptic inhibitory transmissions in the central nervous system. There are multiple GABA_A receptor subtypes constructed from 19 different subunits in mammals that exhibit different regional and subcellular distributions and distinct pharmacological properties. Dysfunctional alterations of GABA_A receptors are associated with various neuropsychiatric disorders. Short- and long-term plastic changes in GABA_A receptors can be induced by the activation of different intracellular signaling pathways that are triggered, under physiological and pathological conditions, by calcium entering through voltage-gated calcium channels. This review discusses several mechanisms of regulation of GABA_A receptor function that result from the activation of L-type voltage gated calcium channels. Calcium influx via these channels activates different signaling cascades that lead to changes in GABA_A receptor transcription, phosphorylation, trafficking, and synaptic clustering, thus regulating the inhibitory synaptic strength. These plastic mechanisms regulate the interplay of synaptic excitation and inhibition that is crucial for the normal function of neuronal circuits.

Remimazolam Tolerance in Long-term Benzodiazepine Users: A Case Report of 2 Cases

A 60-year-old woman with a 5-year history of anxiolytic use, a diazepam-equivalent daily dose of 15 mg, was scheduled for esophageal stent removal. She was given remimazolam (0.5 mg/kg) but remained fully alert. She only lost consciousness with propofol (40 mg). A 61-year-old man with a 1-year history of anxiolytic use, diazepam-equivalent daily dose of 20 mg, was scheduled for hand tumor resection. He was given remimazolam (0.3 mg/kg) but remained fully alert. He only lost consciousness after desflurane inhalation. In a patient with a history of long-term benzodiazepine use, anesthetic or sedative agents aside from remimazolam should be considered.

Padsevonil randomized Phase IIa trial in treatment-resistant focal epilepsy: a translational approach

Therapeutic options for patients with treatment-resistant epilepsy represent an important unmet need. Addressing this unmet need was the main factor driving the drug discovery program that led to the synthesis of padsevonil, a first-in-class antiepileptic drug candidate that interacts with two therapeutic targets: synaptic vesicle protein 2 and GABA_A receptors. Two PET imaging studies were conducted in healthy volunteers to identify optimal padsevonil target occupancy corresponding to levels associated with effective antiseizure activity in rodent models. Optimal padsevonil occupancy associated with non-clinical efficacy was translatable to humans for both molecular targets: high (>90%), sustained synaptic vesicle protein 2A occupancy and 10-15% transient GABA_A receptor occupancy. Rational dose selection enabled clinical evaluation of padsevonil in a Phase IIa proof-of-concept trial (NCT02495844), with a single-dose arm (400 mg bid). Adults with highly treatment-resistant epilepsy, who were experiencing ≥4 focal seizures/week, and had failed to respond to ≥4 antiepileptic drugs, were randomized to receive placebo or padsevonil as add-on to their stable regimen. After a 3-week inpatient double-blind period, all patients received padsevonil during an 8-week outpatient open-label period. The primary endpoint was ≥75% reduction in seizure frequency. Of 55 patients randomized, 50 completed the trial (placebo n = 26; padsevonil n = 24). Their median age was 36 years (range 18-60), and they had been living with epilepsy for an average of 25 years. They were experiencing a median of 10 seizures/week and 75% had failed ≥8 antiepileptic drugs. At the end of the inpatient period, 30.8% of patients on padsevonil and 11.1% on placebo were ≥75% responders (odds ratio 4.14; P = 0.067). Reduction in median weekly seizure frequency was 53.7% and 12.5% with padsevonil and placebo, respectively (unadjusted P = 0.026). At the end of the outpatient period, 31.4% were ≥75% responders and reduction in median seizure frequency was 55.2% (all patients). During the inpatient period, 63.0% of patients on placebo and 85.7% on padsevonil reported treatment-emergent adverse events. Overall, 50 (90.9%) patients who received padsevonil reported treatment-emergent adverse events, most frequently somnolence (45.5%), dizziness (43.6%) and headache (25.5%); only one patient discontinued due to a treatment-emergent adverse event. Padsevonil was associated with a favourable safety profile and displayed clinically meaningful efficacy in patients with treatment-resistant epilepsy. The novel translational approach and the innovative proof-of-concept trial design maximized signal detection in a small patient population in a short duration, expediting antiepileptic drug development for the population with the greatest unmet need in epilepsy.

Understanding the effects of chronic benzodiazepine use in depression: a focus on neuropharmacology

Benzodiazepines are frequently prescribed on an ongoing basis to individuals with depression, mainly to alleviate anxiety or insomnia, despite current guideline recommendations that continuous use should not exceed 4 weeks. Currently, there are no efficacy trials published beyond 8 weeks. Several antidepressant trials demonstrate that the concomitant use of a benzodiazepine is associated with poorer depressive outcomes and functional status; however, it is unclear why this is the case. Patients with depression receiving a benzodiazepine may reflect a more ill or high anxiety group, although even within anxiety disorders, the use of a benzodiazepine is associated with poorer outcomes. The neuroadaptive consequences of long-term benzodiazepine use may be a factor underlying these findings. Chronic benzodiazepine use results in decreased gamma-aminobutyric acid and monoaminergic function, as well as interference with neurogenesis, which are all purported to play a role in antidepressant efficacy. This review will discuss the oppositional neuropharmacological interactions between chronic benzodiazepine use and antidepressant mechanism of action, which could result in reduced antidepressant efficacy and function in depression.

Precise 3D modulation of electro-optical parameters during neurotransmitter uncaging experiments with neurons in vitro

Ruthenium–bipyridinetriphenylphosphine–GABA (RuBi–GABA) is a caged compound that allows studying the neuronal transmission in a specific region of a neuron. The inhibitory neurotransmitter γ-aminobutyric acid (GABA) is bound to a caged group that blocks the interaction of the neurotransmitter with its receptor site. Following linear—one-photon (1P)—and non-linear—multi-photon—absorption of light, the covalent bond of the caged molecule is broken, and GABA is released. Such a controlled release in time and space allows investigating the interaction with its receptor in four dimensions (X,Y,Z,t). Taking advantage of this strategy, we succeeded in addressing the modulation of GABA_A in rat cerebellar neurons by coupling the photoactivation process, by confocal or two-photon excitation microscopy, with the electrophysiological technique of the patch-clamp in the whole-cell configuration. Key parameters have been comprehensively investigated and correlated in a temporally and spatially confined way, namely: photoactivation laser power, time of exposure, and distance of the uncaging point from the cell of interest along the X, Y, Z spatial coordinates. The goal of studying specific biological events as a function of controlled physical parameters has been achieved.

Prevalence of benzodiazepines and benzodiazepine-related drugs exposure before, during and after pregnancy: A systematic review and meta-analysis

BACKGROUND

Maternal use of benzodiazepines during pregnancy is common and has increased over the last decades. In this systematic review and meta-analysis, we studied the literature to estimate the worldwide use of benzodiazepines before, during and after pregnancy, which could help to estimate benzodiazepine exposure and to prioritize and guide future investigations.

METHODS

We systematically searched Embase, Medline Ovid, Web of Science and Cochrane Central up until July 2019 for studies reporting on benzodiazepine use before (12 months), during and after pregnancy (12 months). Random effects meta-analysis was conducted to calculate pooled prevalence estimates, as well as stratified according to substantive variables.

RESULTS

We identified 32 studies reporting on 28 countries, together reporting on 7,343,571 pregnancies. The worldwide prevalence of benzodiazepine use/prescriptions during pregnancy was 1.9% (95%CI 1.6%-2.2%; I² 97.48%). Highest prevalence was found in the third trimester (3.1%; 95%CI 1.8%-4.5%; I² 99.83%). Lorazepam was the most frequently used/prescribed benzodiazepine (1.5%; 95%CI 0.5%-2.5%; I² 99.87%). Highest prevalence was found in Eastern Europe (14.0%; 95%CI 12.1%-15.9%; I² 0.00%).

LIMITATIONS

All analyses revealed considerable heterogeneity.

CONCLUSIONS

Our meta-analysis confirmed that benzodiazepine use before, during and after pregnancy is prevalent. The relatively common use of benzodiazepines with possible risks for both mother and (unborn) child is worrying and calls for prescription guidelines for women, starting in the preconception period. Given the substantial proportion of children exposed to benzodiazepines in utero, future research should continue to study the short- and long-term safety of maternal benzodiazepine use during pregnancy and to explore non-pharmacological alternative treatments.

Tolerance and dependence following chronic alprazolam treatment: quantitative observation studies in female rhesus monkeys

RATIONALE

In order to understand mechanisms underlying tolerance and dependence following chronic benzodiazepine treatments, quantitative and reproducible behavioral models of these phenomena are required.

OBJECTIVES

This research evaluated the ability of chronic treatment with a commonly prescribed benzodiazepine, alprazolam, to induce tolerance to sedative effects and physical dependence using a novel set of behavioral measurements in rhesus monkeys.

METHODS

Four female rhesus monkeys (Macaca mulatta) were implanted with chronic intravenous catheters and administered i.v. alprazolam (1.0 mg/kg every 4 h, 38 days total). Quantitative observation measures were obtained during the 38 days of treatment. Acute administration of the benzodiazepine receptor antagonist flumazenil (0.1, 0.3 mg/kg, i.v.) was given to assess precipitated withdrawal. On day 39, saline was substituted for alprazolam and withdrawal signs were assessed for 7 days.

RESULTS

Maximal sedation ("deep sedation") was evident on day 1 but was not significantly different from baseline levels by day 4 and was absent for the remainder of the 38 days of treatment. A milder form of sedation, "rest/sleep posture," emerged by day 3 and did not decline over 38 days. Cessation of alprazolam treatment resulted in significant withdrawal signs (nose rub, vomit, procumbent posture, tremor/jerk, rigid posture) that dissipated by day 3. These signs also were observed with flumazenil (0.3 mg/kg).

CONCLUSIONS

Chronic alprazolam treatment resulted in rapid tolerance to some behaviors (e.g., deep sedation) but no tolerance to others (e.g., rest/sleep posture). Physical dependence was observed via both spontaneous and precipitated withdrawal. Based on previous research, these phenomena may reflect differential plasticity at GABA_A receptor subtypes.

Chronic Exposure to Oxazepam Pollution Produces Tolerance to Anxiolytic Effects in Zebrafish (Danio rerio)

Environmental concentrations of the anxiolytic drug oxazepam have been found to disrupt antipredator behaviors of wild fish. Most experiments exposed fish for a week, while evidence from mammals suggests that chronic exposure to therapeutic concentrations of benzodiazepines (such as oxazepam) results in the development of tolerance to the anxiolytic effects. If tolerance can also develop in response to the low concentrations found in the aquatic environment, it could mitigate the negative effects of oxazepam pollution. In the current study, we exposed wild-caught zebrafish to oxazepam (∼7 μg L^-1) for 7 or 28 days and evaluated behavioral and physiological parameters at both time points. Females showed reduced diving responses to conspecific alarm pheromone after 7 days, but not after 28 days, indicating that they had developed tolerance to the anxiolytic effects of the drug. Zebrafish males were not affected by this oxazepam concentration, in line with earlier results. Serotonin turnover (ratio 5-HIAA/5-HT) was reduced in exposed females and males after 28 days, indicating that brain neurochemistry had not normalized. Post-confinement cortisol concentrations and gene expression of corticotropin-releasing hormone (CRH) were not affected by oxazepam. We did not find evidence that chronically exposed fish had altered relative expression of GABA_A receptor subunits, suggesting that some other still unknown mechanism caused the developed tolerance.

Benzodiazepine exposure induces transcriptional down-regulation of GABAA receptor α1 subunit gene via L-type voltage-gated calcium channel activation in rat cerebrocortical neurons

GABA_A receptors are targets of different pharmacologically relevant drugs, such as barbiturates, benzodiazepines, and anesthetics. In particular, benzodiazepines are prescribed for the treatment of anxiety, sleep disorders, and seizure disorders. Benzodiazepines potentiate GABA responses by binding to GABA_A receptors, which are mainly composed of α (1-3, 5), β2, and γ2 subunits. Prolonged activation of GABA_A receptors by endogenous and exogenous modulators induces adaptive changes that lead to tolerance. For example, chronic administration of benzodiazepines produces tolerance to most of their pharmacological actions, limiting their usefulness. The mechanism of benzodiazepine tolerance is still unknown. To investigate the molecular basis of tolerance, we studied the effect of sustained exposure of rat cerebral cortical neurons to diazepam on the GABA_A receptor. Flunitrazepam binding experiments showed that diazepam treatment induced uncoupling between GABA and benzodiazepine sites, which was blocked by co-incubation with flumazenil, picrotoxin, or nifedipine. Diazepam also produced selective transcriptional down-regulation of GABA_A receptor α1 subunit gene through a mechanism dependent on the activation of L-type voltage-gated calcium channels. These findings suggest benzodiazepine-induced stimulation of calcium influx through L-type voltage-gated calcium channels triggers the activation of a signaling pathway that leads to uncoupling and an alteration of receptor subunit expression. Insights into the mechanism of benzodiazepine tolerance will contribute to the design of new drugs that can maintain their efficacies after long-term treatments.

4,5 caffeoylquinic acid and scutellarin, identified by integrated metabolomics and proteomics approach as the active ingredients of Dengzhan Shengmai, act against chronic cerebral hypoperfusion by regulating glutamatergic and GABAergic synapses

Dengzhan Shengmai (DZSM) is a proprietary Chinese medicine for remarkable curative effect as a treatment of cerebrovascular diseases, such as chronic cerebral hypoperfusion (CCH) and dementia based on evidence-based medicine, which have been widely used in the recovery period of ischemic cerebrovascular diseases. The purpose of this study was to investigate the active substances and mechanism of DZSM against CCH. Integrative metabolomic and proteomic studies were performed to investigate the neuroprotective effect of DZSM based on CCH model rats. The exposed components of DZSM in target brain tissue were analysed by a high-sensitivity HPLC-MS/MS method, and the exposed components were tested on a glutamate-induced neuronal excitatory damage cell model for the verification of active ingredients and mechanism of DZSM. Upon proteomic and metabolomic analysis, we observed a significant response in DZSM therapy from the interconnected neurotransmitter transport pathways including glutamatergic and GABAergic synapses. Additionally, DZSM had a significant regulatory effect on glutamate and GABA-related proteins including vGluT1 and vIAAT, suggested that DZSM could be involved in the vesicle transport of excitatory and inhibitory neurotransmitters in the pre-synaptic membrane. DZSM could also regulated the metabolism of arachidonic acid (AA), phospholipids, lysophospholipids and the expression of phospholipase A2 in post-synaptic membrane. The results of glutamate-induced neuronal excitatory injury cell model experiment for verification of active ingredients and mechanism of DZSM showed that there are five active ingredients, and among them, 4,5 caffeoylquinic acid (4,5-CQA) and scutellarin (SG) could simultaneously affect the GABAergic and glutamatergic synaptic metabolism as well as the related receptors, the NR2b subunit of NMDA and the α1 subunit of GABA_A. The active ingredients of DZSM could regulate the over-expression of the NMDA receptor, enhance the expression of the GABA_A receptor, resist glutamate-induced neuronal excitatory damage, and finally maintain the balance of excitatory and inhibitory synaptic metabolism dominated by glutamate and GABA. Furtherly, we compared the efficacy of DZSM, 4,5-CQA, SG and the synergistic effect of 4,5-CQA and SG, and the results showed that all the groups significantly improved cell viability compared with the model group (p < 0.001). The western blot results showed that DZSM, 4,5-CQA, SG and 4,5-CQA/SG co-administration groups could significantly regulate the expression of receptors (GABA_A α1 and NR2b subunit of NMDA) and synaptic-related proteins, such as Sv2a, Syp, Slc17a7, bin1 and Prkca, respectively. These results proved DZSM and its active ingredients (4,5-CQA and SG) had the effect of regulating glutamatergic and GABAergic synapses. Finally, membrane potential FLIPR assay of 4,5-CQA and SG was used for GABRA1 activity test, and it was found that the two compounds could increase GABA-induced activation of GABRA1 receptor (GABA 10 μM) in a dose-dependent manner with EC₅₀ value of 48.74 μM and 29.77 μM, respectively. Manual patch clamp method was used to record NMDA NR1/NR2B subtype currents, and scutellarin could cause around 10 % blockade at 10 μM (p＜0.05 compared with the control group). These studies provided definitive clues of the mechanism for the neuroprotective effect of DZSM for CCH treatment and the active compounds regulating glutamatergic and GABAergic synapses. Additionally, 4,5-CQA and SG might be potential drugs for the treatment of neurodegenerative disease related to CCH.

Safety and efficacy of midazolam nasal spray in the outpatient treatment of patients with seizure clusters: An open-label extension trial

OBJECTIVE

To evaluate safety- and seizure-related outcomes with repeated intermittent use of a novel formulation of midazolam administered as a single-dose nasal spray (MDZ-NS) in the outpatient treatment of patients experiencing seizure clusters (SCs).

METHODS

In this open-label extension trial (ClinicalTrials.gov NCT01529034), patients aged ≥12 years and on a stable regimen of antiepileptic drugs who completed the original phase III, randomized controlled trial were enrolled. Caregivers administered MDZ-NS 5 mg when patients experienced SCs; a second dose could be given if seizures did not terminate within 10 minutes or recurred within 10 minutes-6 hours. Patients were monitored for treatment-emergent adverse events (TEAEs) throughout, and the main seizure-related outcome was treatment success, defined as seizure termination within 10 minutes and no recurrence 10 minutes-6 hours after drug administration.

RESULTS

Of 175 patients enrolled, 161 (92.0%) received ≥1 MDZ-NS dose, for a total of 1998 SC episodes. Median time spent by patients in the trial was 16.8 months (range = 1-55.7 months). TEAEs were experienced by 40.4% of patients within 2 days of drug administration and 57.1% overall. TEAEs reported by most patients (within 2 days and overall) were nasal discomfort (12.4%) and somnolence (9.3%). One patient each discontinued due to treatment-related nasal discomfort and somnolence. There were no patients with treatment-related respiratory depression, and none with TEAEs indicative of drug abuse or dependence. Treatment success criteria were met in 55% (1108/1998) of SC episodes after administration of a single 5-mg dose and in 80.2% (617/769) with the second dose. Treatment success was consistent over treated episode number.

SIGNIFICANCE

Repeated, intermittent, acute treatment of patients experiencing SCs with MDZ-NS in the outpatient setting was well tolerated over an extended period, with maintenance of efficacy suggesting lack of development of tolerance.

Involvement of the GABAA receptor α subunit in the mode of action of etifoxine

Etifoxine (EFX) is a non-benzodiazepine psychoactive drug which exhibits anxiolytic effects through a dual mechanism, by directly binding to GABA_A receptors (GABA_ARs) and to the mitochondrial 18-kDa translocator protein, resulting in the potentiation of the GABAergic function. The β subunit subtype plays a key role in the EFX-GABA_AR interaction, however this does not explain the anxiolytic effects of this drug. Here, we combined behavioral and electrophysiological experiments to challenge the role of the GABA_AR α subunit in the EFX mode of action. After single administrations of anxiolytic doses (25-50 mg/kg, intraperitoneal), EFX did not induce any neurological nor locomotor impairments, unlike the benzodiazepine bromazepam (0.5-1 mg/kg, intraperitoneal). We established the EFX pharmacological profile on heteropentameric GABA_ARs constructed with α1 to α6 subunit expressed in Xenopus oocyte. Unlike what is known for benzodiazepines, neither the γ nor δ subunits influenced EFX-mediated potentiation of GABA-evoked currents. EFX acted first as a partial agonist on α2β3γ2S, α3β3γ2S, α6β3γ2S and α6β3δ GABA_ARs, but not on α1β3γ2S, α4β3γ2S, α4β3δ nor α5β3γ2S GABA_ARs. Moreover, EFX exhibited much higher positive allosteric modulation towards α2β3γ2S, α3β3γ2S and α6β3γ2S than for α1β3γ2S, α4β3γ2S and α5β3γ2S GABA_ARs. At 20 μM, corresponding to brain concentration at anxiolytic doses, EFX increased GABA potency to the highest extent for α3β3γ2S GABA_ARs. We built a docking model of EFX on α3β3γ2S GABA_ARs, which is consistent with a binding site located between α and β subunits in the extracellular domain. In conclusion, EFX preferentially potentiates α2β3γ2S and α3β3γ2S GABA_ARs, which might support its advantageous anxiolytic/sedative balance.

Gephyrin Palmitoylation in Basolateral Amygdala Mediates the Anxiolytic Action of Benzodiazepine

BACKGROUND

Benzodiazepines (BZDs) have been used to treat anxiety disorders for more than five decades as the allosteric modulator of the gamma-aminobutyric acid A receptor (GABA_AR). Little is known about other mechanisms of BZDs. Here, we describe how the rapid stabilization of postsynaptic GABA_AR is essential and sufficient for the anxiolytic effect of BZDs via a palmitoylation-dependent mechanism.

METHODS

Palmitoylated proteins in the basolateral amygdala (BLA) of rats with different anxious states were assessed by a biotin exchange protocol. Both pharmacological and genetic approaches were used to investigate the role of palmitoylation in anxiety behavior. Electrophysiological recording, reverse transcription polymerase chain reaction, Western blotting, and coimmunoprecipitation were used to investigate the mechanisms.

RESULTS

Highly anxious rats were accompanied by the deficiency of gephyrin palmitoylation and decreased the synaptic function of GABA_AR in the BLA. We then identified that the dysfunction of DHHC12, a palmitoyl acyltransferase that specifically palmitoylates gephyrin, contributed to the high-anxious state. Furthermore, diazepam, as an anxiolytic drug targeting GABA_ARs, was found to increase gephyrin palmitoylation in the BLA via a GABA_AR-dependent manner to activate DHHC12. The anxiolytic effect of diazepam was nearly abolished by the DHHC12 knockdown. Specifically, similar to the effect of BZD, the overexpression of DHHC12 in the BLA exerted a significant anxiolytic action, which was prevented by flumazenil.

CONCLUSIONS

Our results support the view that the strength of inhibitory synapse was controlled by gephyrin palmitoylation in vivo and proposes a previously unknown palmitoylation-centered mode of BZD's action.

The need to improve detection and treatment of physical pain of homeless people with schizophrenia and bipolar disorders. Results from the French Housing First Study

OBJECTIVE

The aim of this study was to investigate the prevalence and associated factors of physical pain in a large multicenter sample of Homeless Schizophrenia and Bipolar (HSB) patients.

METHODS

This multicenter study was conducted in 4 French cities: Lille, Marseille, Paris and Toulouse. Pain was measured by EQ5D-3 L questionnaire with no specified period or location. In addition, sociodemographic information, duration of homelessness, illness severity using the Modified Colorado Symptom Index (MCSI) and drug information were collected.

RESULTS

Overall, 655 HSB patients, mean age 38.8 years and 82.6% men were included, 448 (68.9%) were diagnosed with schizophrenia and 202 (31.1%) with bipolar disorder. More than half patients (N = 337, 51.5%) reported moderate to extreme physical pain while only 2.7% were administered analgesic drugs. In the multivariate analysis, self-reported moderate to extreme physical pain was associated with antidepressant consumption (adjusted odd ratio aOR = 2.56[1.25;5.26], p = .01), female gender (aOR = 1.72[1.03;2.86], p = .04), bipolar disorders (vs. schizophrenia) (aOR = 1.81[1.19;2.77], p = .006), older age (aOR = 1.03 [1.01;1.05], p = .01), with higher MCSI psychotic score (a0R = 1.04[1.01;1.06],p = .002), independently of the number of days in the street during the last 180 days, MCSI depression score, alcohol and substance use disorders, psychotropic drugs and analgesic treatments. No association with education level, antipsychotics, mood stabilizers, anxiolytic, hypnotic or medication adherence was found (all p > .05).

CONCLUSION

Physical pain was highly reported in homeless patients with severe mental illness with insufficient care. Physical pain should be systematically explored and treated in this population. Bipolar disorders, antidepressant consumption and female gender may be targeted in priority. Age and psychotic symptomatology were found to influence self-reported pain in a marginal way.

Inert gas narcosis in scuba diving, different gases different reactions

PURPOSE

Underwater divers face several potential neurological hazards when breathing compressed gas mixtures including nitrogen narcosis which can impact diver's safety. Various human studies have clearly demonstrated brain impairment due to nitrogen narcosis in divers at 4 ATA using critical flicker fusion frequency (CFFF) as a cortical performance indicator. However, recently some authors have proposed a probable adaptive phenomenon during repetitive exposure to high nitrogen pressure in rats, where they found a reversal effect on dopamine release.

METHODS

Sixty experienced divers breathing Air, Trimix or Heliox, were studied during an open water dive to a depth of 6 ATA with a square profile testing CFFF measurement before (T₀), during the dive upon arriving at the bottom (6 ATA) (T₁), 20 min of bottom time (T₂), and at 5 m (1.5 ATA) (T₃).

RESULTS

CFFF results showed a slight increase in alertness and arousal during the deep dive regardless of the gas mixture breathed. The percent change in CFFF values at T₁ and T₂ differed among the three groups being lower in the air group than in the other groups. All CFFF values returned to basal values 5 min before the final ascent at 5 m (T₃), but the Trimix measurements were still slightly better than those at T₀.

CONCLUSIONS

Our results highlight that nitrogen and oxygen alone and in combination can produce neuronal excitability or depression in a dose-related response.

Diazepam-induced loss of inhibitory synapses mediated by PLCδ/ Ca2+/calcineurin signalling downstream of GABAA receptors

Benzodiazepines facilitate the inhibitory actions of GABA by binding to γ-aminobutyric acid type A receptors (GABAARs), GABA-gated chloride/bicarbonate channels, which are the key mediators of transmission at inhibitory synapses in the brain. This activity underpins potent anxiolytic, anticonvulsant and hypnotic effects of benzodiazepines in patients. However, extended benzodiazepine treatments lead to development of tolerance, a process which, despite its important therapeutic implications, remains poorly characterised. Here we report that prolonged exposure to diazepam, the most widely used benzodiazepine in clinic, leads to a gradual disruption of neuronal inhibitory GABAergic synapses. The loss of synapses and the preceding, time- and dose-dependent decrease in surface levels of GABAARs, mediated by dynamin-dependent internalisation, were blocked by Ro 15-1788, a competitive benzodiazepine antagonist, and bicuculline, a competitive GABA antagonist, indicating that prolonged enhancement of GABAAR activity by diazepam is integral to the underlying molecular mechanism. Characterisation of this mechanism has revealed a metabotropic-type signalling downstream of GABAARs, involving mobilisation of Ca2+ from the intracellular stores and activation of the Ca2+/calmodulin-dependent phosphatase calcineurin, which, in turn, dephosphorylates GABAARs and promotes their endocytosis, leading to disassembly of inhibitory synapses. Furthermore, functional coupling between GABAARs and Ca2+ stores was sensitive to phospholipase C (PLC) inhibition by U73122, and regulated by PLCδ, a PLC isoform found in direct association with GABAARs. Thus, a PLCδ/Ca2+/calcineurin signalling cascade converts the initial enhancement of GABAARs by benzodiazepines to a long-term downregulation of GABAergic synapses, this potentially underpinning the development of pharmacological and behavioural tolerance to these widely prescribed drugs.

DNA damage and oxidative stress induced by seizures are decreased by anticonvulsant and neuroprotective effects of lobeline, a candidate to treat alcoholism

The alkaloid lobeline (Lob) has been studied due to its potential use in treatment of drug abuse. This study evaluates the possible anticonvulsant and neuroprotective activities of Lob to obtain new information on its properties that could confirm it as a candidate in the treatment of alcohol addiction. The anticonvulsant effect of Lob was evaluated using a pilocarpine-induced seizure model. In addition, possible neuroprotective effects were investigated measuring DNA damage using the comet assay, assessing free radical levels by dichlorofluorescein diacetate (DCF) oxidation, and measuring the antioxidant potential using the α, α-diphenyl-β-picrylhydrazyl (DPPH) scavenging assay, besides measuring superoxide dismutase (SOD) and catalase (CAT) enzyme activities in brain tissues. Lobeline increased the latency to the first seizure and decreased the percentage of seizures in a similar way as diazepam, used as control. DNA damage induced by Pil and hydrogen peroxide were decreased in hippocampus and cerebral cortex from mice treated with Lob. The levels of free radicals and CAT activity increased in cortex and hippocampus, respectively, in mice treated with Pil. Lobeline decreased CAT in hippocampus, leading to similar values as in the saline negative control. In conclusion, Lob has anticonvulsant and neuroprotective actions that may be mediated by antioxidant-like mechanisms, indicating its potential as candidate drug in alcoholism therapy.

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

Benzodiazepines are one of the most prescribed medications as first-line treatment of anxiety, insomnia, and epilepsy around the world. Over the past two decades, advances in the neuropharmacological understanding of gamma aminobutyric acid (GABA)_A receptors revealed distinct contributions from each subtype and produced effects. Recent findings have highlighted the importance of α₁ containing GABA_A receptors in the mechanisms of addiction and tolerance in benzodiazepine treatments. This has shown promise in the development of tranquilizers with minimal side effects such as cognitive impairment, dependence, and tolerance. A valium-like drug without its side effects, as repeatedly demonstrated in animals, is achievable.

Cerebral Malaria Causes Enduring Behavioral and Molecular Changes in Mice Brain Without Causing Gross Histopathological Damage

Malaria, parasitic disease considered a major health public problem, is caused by Plasmodium protozoan genus and transmitted by the bite of infected female Anopheles mosquito genus. Cerebral malaria (CM) is the most severe presentation of malaria, caused by P. falciparum and responsible for high mortality and enduring development of cognitive deficits which may persist even after cure and cessation of therapy. In the present study we evaluated selected behavioral, neurochemical and neuropathologic parameters after rescue from experimental cerebral malaria caused by P. berghei ANKA in C57BL/6 mice. Behavioral tests showed impaired nest building activity as well as increased marble burying, indicating that natural behavior of mice remains altered even after cure of infection. Regarding the neurochemical data, we found decreased α2/α3 Na⁺,K⁺-ATPase activity and increased immunoreactivity of phosphorylated Na⁺,K⁺-ATPase at Ser⁹⁴³ in cerebral cortex after CM. In addition, [³H]-Flunitrazepam binding assays revealed a decrease of benzodiazepine/GABA_A receptor binding sites in infected animals. Moreover, in hippocampus, dot blot analysis revealed increased levels of protein carbonyls, suggesting occurrence of oxidative damage to proteins. Interestingly, no changes in the neuropathological markers Fluoro-Jade C, Timm staining or IBA-1 were detected. Altogether, present data indicate that behavioral and neurochemical alterations persist even after parasitemia clearance and CM recovery, which agrees with available clinical findings. Some of the molecular mechanisms reported in the present study may underlie the behavioral changes and increased seizure susceptibility that persist after recovery from CM and may help in the future development of therapeutic strategies for CM sequelae.

Peptide Selank Enhances the Effect of Diazepam in Reducing Anxiety in Unpredictable Chronic Mild Stress Conditions in Rats

It was shown that the anxiolytic effect of Selank is comparable to that of classical benzodiazepine drugs and that the basis of their mechanism of action may be similar. These data suggest that the presence of Selank may change the action of classical benzodiazepine drugs. To test this hypothesis, we evaluated the anxiolytic activity of Selank and diazepam in rats both under conditions of unpredictable chronic mild stress and in its absence, after the individual and combined administration of these compounds using the elevated plus maze test. We found that, even in the absence of chronic stress, the administration of a course of test substances changed anxiety indicators toward their deterioration, but the changes after the administration of a course of Selank were less pronounced. In conditions of chronic stress, anxiety indicator values after the simultaneous use of diazepam and Selank did not differ from the respective values observed before chronic stress exposure. The data obtained indicate that the individual administration of Selank was the most effective in reducing elevated levels of anxiety, induced by the administration of a course of test substances, whereas the combination of diazepam with Selank was the most effective in reducing anxiety in unpredictable chronic mild stress conditions.

The Importance of L-Arginine:NO:cGMP Pathway in Tolerance to Flunitrazepam in Mice

The goal of the study was to investigate the effects of drugs modifying l-arginine:NO:cGMP pathway on the development of tolerance to flunitrazepam (FNZ)-induced motor impairment in mice. FNZ-induced motor incoordination was assessed on the 1st and 8th days of experiment, using the rotarod and chimney tests. It was found that (a) both a non-selective nitric oxide synthase (NOS) inhibitor: N^G-nitro-l-arginine methyl ester (l-NAME) and an unselective neuronal NOS inhibitor: 7-nitroindazole (7-NI) inhibited the development of tolerance to the motor-impairing effects of FNZ in the rotarod and the chimney tests and (b) both a NO precursor: l-arginine and a selective inhibitor of phosphodiesterase 5 (PDE5): sildenafil did not affect the development of tolerance to FNZ-induced motor impairment in mice. Those findings provided behavioural evidence that NO could contribute an important role in the development of tolerance to FNZ in mice.