Selective 5HT2A and 5HT6 receptor antagonists promote sleep in rats

Preventive Effects of Ramelteon, Suvorexant, and Lemborexant on Delirium in Hospitalized Patients With Physical Disease: A Retrospective Cohort Study

BACKGROUND

New sleep-inducing drugs (eg, ramelteon, suvorexant, and lemborexant) have been shown to prevent delirium in high-risk groups. However, no single study has simultaneously evaluated the delirium-preventing effects of all novel sleep-inducing drugs in hospitalized patients. Therefore, this study aimed to clarify the relationship between sleep-inducing drugs and delirium prevention in patients hospitalized in general medical-surgical settings for nonpsychiatric conditions who underwent liaison interventions for insomnia.

METHODS

This retrospective cohort study included patients treated in general medical-surgical settings for nonpsychiatric conditions with consultation-liaison psychiatry consult for insomnia. Delirium was diagnosed by fully certified psychiatrists using the Diagnostic and Statistical Manual of Mental Disorders 5th edition. The following items were retrospectively examined from medical records as factors related to delirium development: type of sleep-inducing drugs, age, sex, and delirium risk factors. The risk factors of delirium development were calculated using adjusted odds ratios (aORs) via multivariate logistic regression analysis.

RESULTS

Among the 710 patients analyzed, 257 (36.2%) developed delirium. Suvorexant (aOR, 0.61; 95% confidence interval [CI], 0.40-0.94; P = 0.02) and lemborexant (aOR, 0.23; 95% CI, 0.14-0.39; P < 0.0001) significantly reduced the risk of developing delirium. Benzodiazepines (aOR, 1.90; 95% CI, 1.15-3.13; P = 0.01) significantly increased this risk. Ramelteon (aOR, 1.30; 95% CI, 0.84-2.01; P = 0.24) and Z-drugs (aOR, 1.27; 95% CI, 0.81-1.98; P = 0.30) were not significantly associated with delirium development.

CONCLUSIONS

The use of suvorexant and lemborexant may prevent delirium in patients with a wide range of medical conditions.

In Vitro and In Vivo Evaluation of Pellotine: A Hypnotic Lophophora Alkaloid

Quality of life is often reduced in patients with sleep-wake disorders. Insomnia is commonly treated with benzodiazepines, despite their well-known side effects. Pellotine (1), a Lophophora alkaloid, has been reported to have short-acting sleep-inducing properties in humans. In this study, we set out to evaluate various in vitro and in vivo properties of 1. We demonstrate that 1 undergoes slow metabolism; e.g. in mouse liver microsomes 65% remained, and in human liver microsomes virtually no metabolism was observed after 4 h. In mouse liver microsomes, two phase I metabolites were identified: 7-desmethylpellotine and pellotine-N-oxide. In mice, the two diastereomers of pellotine-O-glucuronide were additionally identified as phase II metabolites. Furthermore, we demonstrated by DESI-MSI that 1 readily enters the central nervous system of rodents. Furthermore, radioligand-displacement assays showed that 1 is selective for the serotonergic system and in particular the serotonin (5-HT)1D, 5-HT6, and 5-HT7 receptors, where it binds with affinities in the nanomolar range (117, 170, and 394 nM, respectively). Additionally, 1 was functionally characterized at 5-HT6 and 5-HT7, where it was found to be an agonist at the former (EC50 = 94 nM, Emax = 32%) and an inverse agonist at the latter (EC50 = 291 nM, Emax = -98.6). Finally, we demonstrated that 1 dose-dependently decreases locomotion in mice, inhibits REM sleep, and promotes sleep fragmentation. Thus, we suggest that pellotine itself, and not an active metabolite, is responsible for the hypnotic effects and that these effects are possibly mediated through modulation of serotonergic receptors.

Activation of the nociceptin/orphanin-FQ receptor promotes NREM sleep and EEG slow wave activity

Sleep/wake control involves several neurotransmitter and neuromodulatory systems yet the coordination of the behavioral and physiological processes underlying sleep is incompletely understood. Previous studies have suggested that activation of the Nociceptin/orphanin FQ (N/OFQ) receptor (NOPR) reduces locomotor activity and produces a sedation-like effect in rodents. In the present study, we systematically evaluated the efficacy of two NOPR agonists, Ro64-6198 and SR16835, on sleep/wake in rats, mice, and Cynomolgus macaques. We found a profound, dose-related increase in non-Rapid Eye Movement (NREM) sleep and electroencephalogram (EEG) slow wave activity (SWA) and suppression of Rapid Eye Movement sleep (REM) sleep in all three species. At the highest dose tested in rats, the increase in NREM sleep and EEG SWA was accompanied by a prolonged inhibition of REM sleep, hypothermia, and reduced locomotor activity. However, even at the highest dose tested, rats were immediately arousable upon sensory stimulation, suggesting sleep rather than an anesthetic state. NOPR agonism also resulted in increased expression of c-Fos in the anterodorsal preoptic and parastrial nuclei, two GABAergic nuclei that are highly interconnected with brain regions involved in physiological regulation. These results suggest that the N/OFQ-NOPR system may have a previously unrecognized role in sleep/wake control and potential promise as a therapeutic target for the treatment of insomnia.

The Evolving Role of Animal Models in the Discovery and Development of Novel Treatments for Psychiatric Disorders

Historically, animal models have been routinely used in the characterization of novel chemical entities (NCEs) for various psychiatric disorders. Animal models have been essential in the in vivo validation of novel drug targets, establishment of lead compound pharmacokinetic to pharmacodynamic relationships, optimization of lead compounds through preclinical candidate selection, and development of translational measures of target occupancy and functional target engagement. Yet, with decades of multiple NCE failures in Phase II and III efficacy trials for different psychiatric disorders, the utility and value of animal models in the drug discovery process have come under intense scrutiny along with the widespread withdrawal of the pharmaceutical industry from psychiatric drug discovery. More recently, the development and utilization of animal models for the discovery of psychiatric NCEs has undergone a dynamic evolution with the application of the Research Domain Criteria (RDoC) framework for better design of preclinical to clinical translational studies combined with innovative genetic, neural circuitry-based, and automated testing technologies. In this chapter, the authors will discuss this evolving role of animal models for improving the different stages of the discovery and development in the identification of next generation treatments for psychiatric disorders.

Pimavanserin and Parkinson's Disease Psychosis: A Narrative Review

Pimavanserin (PMV) is the first approved drug for treating hallucinations and delusions in Parkinson's disease (PD) psychosis. Psychosis is one of the leading causes of nursing home placement in people with PD. Furthermore, hallucinations are a more frequent cause of institutionalization than motor disability or dementia related to PD. The management of PD psychosis involves antipsychotic medications. Most of the drugs in this class directly block dopamine D2 receptors, leading to significantly worsening motor symptoms in patients with PD. The most commonly used medications for managing PD psychosis are quetiapine, clozapine, and PMV. This literature review aims to study pimavanserin's history, mechanism, clinical trials, and post-marketing experience. PMV is a potent 5-HT2A receptor antagonist/inverse agonist. Moreover, this drug can interact with 5-HT2C receptors. We calculated some physicochemical descriptors and pharmacokinetic properties of PMV. Eight clinical trials of PMV and PD psychosis are registered on ClinicalTrials.gov. Only four of them have complete results already published. Meta-analytic results showed that PMV efficacy is inferior to clozapine. However, PMV has a significantly lower number of side-effects for managing psychosis in PD. Medicare database assessment revealed 35% lower mortality with PMV compared to other atypical antipsychotics. Moreover, sensitive statistical analysis demonstrated that PMV is a protective factor for the risk of falls in individuals with PD.

Analysis of the effects of a tricyclic antidepressant on secondary sleep disturbance induced by chronic pain in a preclinical model

Chronic pain and sleep have a bidirectional relationship that promotes a vicious circle making chronic pain more difficult to treat. Therefore, pain and sleep should be treated simultaneously. In our previous study, we suggested that hyperactivation of ascending serotonergic neurons could cause secondary sleep disturbance in chronic pain. This study aimed to demonstrate the effects of a tricyclic antidepressant (amitriptyline) and a selective 5-hydroxy-tryptamine 2A (5-HT_2A) antagonist (MDL 100907) that adjust serotonergic transmission, on secondary sleep disturbance induced in a preclinical chronic pain model. We produced a chronic neuropathic pain model by partial sciatic nerve ligation in mice, analyzed their electroencephalogram (EEG) and electromyogram (EMG) using the SleepSign software, and evaluated the sleep condition of the pain model mice after administration of amitriptyline or MDL 100907. Amitriptyline improved thermal hyperalgesia and the amount of sleep, especially non-REM sleep. Time change of normalized power density of δ wave in the nerve ligation group with amitriptyline administration showed a normal pattern that was similar to sham mice. In addition, MDL 100907 normalized sleep condition similar to amitriptyline, without improvement in pain threshold. In conclusion, amitriptyline could improve sleep quantity and quality impaired by chronic pain. 5-HT_2A receptor antagonism could partially contribute to this sleep improvement, but is not associated with pain relief.

Zebrafish behavioural profiling identifies GABA and serotonin receptor ligands related to sedation and paradoxical excitation

Anesthetics are generally associated with sedation, but some anesthetics can also increase brain and motor activity—a phenomenon known as paradoxical excitation. Previous studies have identified GABA_A receptors as the primary targets of most anesthetic drugs, but how these compounds produce paradoxical excitation is poorly understood. To identify and understand such compounds, we applied a behavior-based drug profiling approach. Here, we show that a subset of central nervous system depressants cause paradoxical excitation in zebrafish. Using this behavior as a readout, we screened thousands of compounds and identified dozens of hits that caused paradoxical excitation. Many hit compounds modulated human GABA_A receptors, while others appeared to modulate different neuronal targets, including the human serotonin-6 receptor. Ligands at these receptors generally decreased neuronal activity, but paradoxically increased activity in the caudal hindbrain. Together, these studies identify ligands, targets, and neurons affecting sedation and paradoxical excitation in vivo in zebrafish.

Some anesthetics despite being generally associated with sedation, can also increase brain activity—a phenomenon called paradoxical excitation. The authors identified dozens of compounds that generally decrease neuronal activity, but increase activity in the caudal hindbrain of zebrafish.

Acute effects of 3,4-methylenedioxymethamphetamine (MDMA) and R(-) MDMA on actigraphy-based daytime activity and sleep parameters in rhesus monkeys

3,4-Methylenedioxymethamphetamine (MDMA) affects monoaminergic pathways that play a critical role in sleep-wake cycles. Dopaminergic mechanisms are thought to mediate the sleep-disrupting effects of stimulant drugs. However, the mechanisms underlying the effects of MDMA on sleep-wake cycles and the effects of R(-) MDMA, a stereoisomer that lacks dopaminergic activity, on sleep remain unknown. The aim of the present study was to investigate the effects of racemic MDMA and R(-) MDMA on daytime activity and sleep-like parameters evaluated with actigraphy in adult rhesus macaques (Macaca mulatta, n = 6). Actiwatch monitors were attached to the monkeys' collars and actigraphy recording was conducted during baseline conditions and after the administration of acute intramuscular injections of saline (vehicle), racemic MDMA (0.3, 1.0, or 1.7 mg/kg), or R(-) MDMA (0.3, 1.0, or 1.7 mg/kg) at 9 or 16 h (3 h before "lights off"). Morning treatments had no effects on sleep-like parameters. Racemic MDMA decreased general daytime activity during the first hour after injection and increased daytime activity at 3 hr posttreatment. Although afternoon administration of racemic MDMA increased sleep latency, it improved other sleep parameters, decreasing wake time after sleep onset (WASO) and increasing sleep efficiency for subjects with low baseline sleep efficiency. Afternoon treatment with R(-) MDMA improved sleep measures, increasing sleep efficiency and decreasing sleep latency and WASO, while having no effects on daytime activity. The stimulant and sleep-disrupting effects of racemic MDMA are likely mediated by dopaminergic and noradrenergic mechanisms, while serotonergic pathways appear to be involved in the sleep-promoting effects of MDMA. (PsycINFO Database Record

Relationship between Job Stress and 5-HT2A Receptor Polymorphisms on Self-Reported Sleep Quality in Physicians in Urumqi (Xinjiang, China): A Cross-Sectional Study

The serotonin receptor (5-HTR) plays a key role in sleep quality regulation. Job-related stress is an important factor that influences sleep quality. However, few reports on the interaction between 5-HTR2A polymorphisms and job stress, and how they may impact upon sleep quality are available. Therefore this study investigated the effects of job stress, 5-HTR2A polymorphisms, and their interaction on sleep quality, in physicians. Using a two-stage stratified sampling method, 918 participants were initially invited to participate in the study. After screening for study inclusion and exclusion criteria, 504 subjects were eventually included in the study. Job stress and sleep quality were assessed using the Job Stress Survey (JSS) and Pittsburgh Sleep Quality Index (PSQI), respectively. The 5-HTR2A receptor gene polymorphisms T102C and -1438G/A of were determined using polymerase chain reaction-restriction fragment length polymorphism. Job stress was significantly associated with sleep quality. High levels of job stress were linked to a higher risk of poor sleep quality compared to low or moderate levels [odds ratio (OR) = 2.909, 95% confidence interval (CI): 1.697–4.986]. High levels of stress may reduce subjects’ sleep quality, leading to an increase the likelihood of sleep disturbances and subsequent daytime dysfunction. The 5-HTR2A receptor gene polymorphism T102C was not significantly associated with sleep quality in this study, however, the -1438G/A polymorphism was significantly associated with sleep quality. The GG genotype of the -1438G/A polymorphism was linked to poorer sleep quality. When compared with subjects with low job-related stress levels×AG/AA genotype (OR = 2.106, 95% CI: 1.278–3.471), physicians with high job-related stress levels×GG genotype had a higher risk of experiencing poor sleep quality (OR = 13.400, 95% CI: 3.143–57.137). The findings of our study indicate that job stress and 5-HTR2A receptor gene polymorphisms are associated with sleep quality in physicians. Subjects with high job stress level or/and the -1438G/A GG genotype were more likely to report poor sleep quality, and furthermore, their combination effect on sleep quality was higher than their independent effects, so it may be suggested that job-related stress and genes have a cumulative effect on sleep quality; that is, stress can increase the risk of poor sleep quality, but this effect is worse in a group of people with specific gene polymorphisms.

Restoration of Physiological Expression of 5-HT6 Receptor into the Primary Cilia of Null Mutant Neurons Lengthens Both Primary Cilia and Dendrites

5-HT₆ (serotonin) receptors are promising targets for a variety of neuropsychiatric disorders and have been linked to several cellular signaling cascades. Endogenous 5-HT₆ receptors are restricted to the primary neuronal cilium, a small sensory organelle stemming from the cell body that receives numerous extrasynaptic signals. Inhibition of 5-HT₆ receptors decreases cilia length in primary neuronal cultures, but the signaling mechanisms involved are still unclear. Intense overexpression of exogenous 5-HT₆ receptors increases the probability for receptors to localize outside the primary cilium and have been associated with changes in cilia morphology and dendritic outgrowth. In the present study, we explore the role of 5-HT₆R rescue on neuronal morphology in primary neuronal cultures from 5-HT₆R-KO mice, at the same time maintaining a more physiologic level of expression, wherein the receptor localizes to cilia in 80%-90% of neurons (similar to endogenous 5-HT₆R localization). We found that rescue of 5-HT₆R expression is sufficient to increase cilia length and dendritic outgrowth, but primarily in neurons in which the receptor is located exclusively in the primary cilia. Additionally, we found that expression of 5-HT₆R mutants deficient in agonist-stimulated cAMP or without the predicted Fyn kinase binding domain maintained constitutive activity for stimulating cAMP and still increased the length of cilia, and that the proposed Fyn kinase domain was required for stimulating dendritic outgrowth. These findings highlight the complexity of 5-HT₆R function and localization, particularly with the use of exogenous overexpression, and provide greater understanding and potential mechanisms for 5-HT₆R drug therapies.

Sleep/Wake Physiology and Quantitative Electroencephalogram Analysis of the Neuroligin-3 Knockout Rat Model of Autism Spectrum Disorder

Study Objectives

Neuroligin-3 (NLGN3) is one of the many genes associated with autism spectrum disorder (ASD). Sleep dysfunction is highly prevalent in ASD, but has not been rigorously examined in ASD models. Here, we evaluated sleep/wake physiology and behavioral phenotypes of rats with genetic ablation of Nlgn3.

Methods

Male Nlgn3 knockout (KO) and wild-type (WT) rats were assessed using a test battery for ASD-related behaviors and also implanted with telemeters to record the electroencephalogram (EEG), electromyogram, body temperature, and locomotor activity. 24-h EEG recordings were analyzed for sleep/wake states and spectral composition.

Results

Nlgn3 KO rats were hyperactive, exhibited excessive chewing behavior, and had impaired prepulse inhibition to an auditory startle stimulus. KO rats also spent less time in non-rapid eye movement (NREM) sleep, more time in rapid eye movement (REM) sleep, exhibited elevated theta power (4-9 Hz) during wakefulness and REM, and elevated delta power (0.5-4 Hz) during NREM. Beta (12-30 Hz) power and gamma (30-50 Hz) power were suppressed across all vigilance states.

Conclusions

The sleep disruptions in Nlgn3 KO rats are consistent with observations of sleep disturbances in ASD patients. The EEG provides objective measures of brain function to complement rodent behavioral analyses and therefore may be a useful tool to study ASD.

Deletion of Trace Amine-Associated Receptor 1 Attenuates Behavioral Responses to Caffeine

Trace amines (TAs), endogenous amino acid metabolites that are structurally similar to the biogenic amines, are endogenous ligands for trace amine-associated receptor 1 (TAAR1), a GPCR that modulates dopaminergic, serotonergic, and glutamatergic activity. Selective TAAR1 full and partial agonists exhibit similar pro-cognitive, antidepressant- and antipsychotic-like properties in rodents and non-human primates, suggesting TAAR1 as a novel target for the treatment of neurological and psychiatric disorders. We previously reported that TAAR1 partial agonists are wake-promoting in rats and mice, and that TAAR1 knockout (KO) and overexpressing mice exhibit altered sleep-wake and EEG spectral composition. Here, we report that locomotor and EEG spectral responses to the psychostimulants modafinil and caffeine are attenuated in TAAR1 KO mice. TAAR1 KO mice and WT littermates were instrumented for EEG and EMG recording and implanted with telemetry transmitters for monitoring locomotor activity (LMA) and core body temperature (T_b). Following recovery, mice were administered modafinil (25, 50, 100 mg/kg), caffeine (2.5, 10, 20 mg/kg) or vehicle p.o. at ZT6 in balanced order. In WT mice, both modafinil and caffeine dose-dependently increased LMA for up to 6 h following dosing, whereas only the highest dose of each drug increased LMA in KO mice, and did so for less time after dosing. This effect was particularly pronounced following caffeine, such that total LMA response was significantly attenuated in KO mice compared to WT at all doses of caffeine and did not differ from Vehicle treatment. T_b increased comparably in both genotypes in a dose-dependent manner. TAAR1 deletion was associated with reduced wake consolidation following both drugs, but total time in wakefulness did not differ between KO and WT mice. Furthermore, gamma band EEG activity following both modafinil and caffeine treatment was attenuated in TAAR1 KO compared to WT mice. Our results show that TAAR1 is a critical component of the behavioral and cortical arousal associated with two widely used psychostimulants with very different mechanisms of action. Together with our previous findings, these data suggest that TAAR1 is a previously unrecognized component of an endogenous wake-modulating system.

Serotonin and brain function: a tale of two receptors

Previous attempts to identify a unified theory of brain serotonin function have largely failed to achieve consensus. In this present synthesis, we integrate previous perspectives with new and older data to create a novel bipartite model centred on the view that serotonin neurotransmission enhances two distinct adaptive responses to adversity, mediated in large part by its two most prevalent and researched brain receptors: the 5-HT1A and 5-HT2A receptors. We propose that passive coping (i.e. tolerating a source of stress) is mediated by postsynaptic 5-HT1AR signalling and characterised by stress moderation. Conversely, we argue that active coping (i.e. actively addressing a source of stress) is mediated by 5-HT2AR signalling and characterised by enhanced plasticity (defined as capacity for change). We propose that 5-HT1AR-mediated stress moderation may be the brain's default response to adversity but that an improved ability to change one's situation and/or relationship to it via 5-HT2AR-mediated plasticity may also be important - and increasingly so as the level of adversity reaches a critical point. We propose that the 5-HT1AR pathway is enhanced by conventional 5-HT reuptake blocking antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), whereas the 5-HT2AR pathway is enhanced by 5-HT2AR-agonist psychedelics. This bipartite model purports to explain how different drugs (SSRIs and psychedelics) that modulate the serotonergic system in different ways, can achieve complementary adaptive and potentially therapeutic outcomes.

Flibanserin Efficacy and Safety in Premenopausal Women With Generalized Acquired Hypoactive Sexual Desire Disorder

INTRODUCTION

Flibanserin is a postsynaptic 5-HT-1A agonist and 5-HT-2A antagonist for the treatment of generalized acquired hypoactive sexual desire disorder in premenopausal women.

AIM

To review and evaluate the efficacy and safety of flibanserin.

METHODS

We review and critique the appropriateness of the co-primary and secondary end points used in the flibanserin pivotal trial research program. We review the efficacy and safety parameters of this drug based on the published literature and related sources.

MAIN OUTCOME MEASURES

Pivotal trial primary and secondary end points and safety profile data from the flibanserin development program.

RESULTS

Our review identified instances of poor fit of two primary trial pivotal trial end points with the hypoactive sexual desire disorder construct: satisfying sexual events and electronic daily diary assessments of the most intense level of sexual desire experienced each day. Efficacy findings of the flibanserin pivotal trials program were positive for satisfying sexual events, not positive for electronic daily diary assessments of the most intense level of sexual desire experienced, and positive for secondary end points of the Female Sexual Function Index desire domain and overall measurements and the Female Sexual Distress Scale-Revised desire-specific and overall measurements. Safety data from the clinical trial program showed a reasonable safety profile.

CONCLUSION

Flibanserin has demonstrated efficacy on appropriate measurements of the hallmarks of hypoactive sexual desire disorder-experience of absent or decreased sexual desire that is persistent over time and distressing-and the safety profile of flibanserin is acceptable. Fisher WA, Pyke RE. Flibanserin Efficacy and Safety in Premenopausal Women With Generalized Acquired Hypoactive Sexual Desire Disorder. Sex Med Rev 2017:5;445-460.

Potential functional and pathological side effects related to off-target pharmacological activity

Most pharmaceutical companies test their discovery-stage proprietary molecules in a battery of in vitro pharmacology assays to try to determine off-target interactions. During all phases of drug discovery and development, various questions arise regarding potential side effects associated with such off-target pharmacological activity. Here we present a scientific literature curation effort undertaken to determine and summarize the most likely functional and pathological outcomes associated with interactions at 70 receptors, enzymes, ion channels and transporters with established links to adverse effects. To that end, the scientific literature was reviewed using an on-line database, and the most commonly reported effects were summarized in tabular format. The resultant table should serve as a practical guide for research scientists and clinical investigators for the prediction and interpretation of adverse side effects associated with molecules interacting with components of this screening battery.

Molecular mechanisms of serotonergic action of the HIV-1 antiretroviral efavirenz

Efavirenz is highly effective at suppressing HIV-1, and the WHO guidelines list it as a component of the first-line antiretroviral (ARV) therapies for treatment-naïve patients. Though the pharmacological basis is unclear, efavirenz is commonly associated with a risk for neuropsychiatric adverse events (NPAEs) when taken at the prescribed dose. In many patients these NPAEs appear to subside after several weeks of treatment, though long-term studies show that in some patients the NPAEs persist. In a recent study focusing on the abuse potential of efavirenz, its receptor psychopharmacology was reported to include interactions with a number of established molecular targets for known drugs of abuse, and it displayed a prevailing behavioral profile in rodents resembling an LSD-like activity. In this report, we discovered interactions with additional serotonergic targets that may be associated with efavirenz-induced NPAEs. The most robust interactions were with 5-HT3A and 5-HT6 receptors, with more modest interactions noted for the 5-HT2B receptor and monoamine oxidase A. From a molecular mechanistic perspective, efavirenz acts as a 5-HT6 receptor inverse agonist of Gs-signaling, 5-HT2A and 5-HT2C antagonist of Gq-signaling, and a blocker of the 5-HT3A receptor currents. Efavirenz also completely or partially blocks agonist stimulation of the M1 and M3 muscarinic receptors, respectively. Schild analysis suggests that efavirenz competes for the same site on the 5-HT2A receptor as two known hallucinogenic partial agonists (±)-DOI and LSD. Prolonged exposure to efavirenz reduces 5-HT2A receptor density and responsiveness to 5-HT. Other ARVs such as zidovudine, nevirapine and emtricitabine did not share the same complex pharmacological profile as efavirenz, though some of them weakly interact with the 5-HT6 receptor or modestly block GABAA currents.

The sleep effects of lurasidone: a placebo-controlled cross-over study using a 4-h phase-advance model of transient insomnia

BACKGROUND

Lurasidone, an atypical antipsychotic, is a potent 5-HT7 antagonist and D2 , 5-HT2A antagonist, and 5-HT1A partial agonist. As such, lurasidone would be expected to modulate sleep and circadian function but there have been no human studies of the sleep effects of a 5-HT7 antagonist. The purpose of this study was to assess effects of lurasidone on sleep.

METHODS

This was a cross-over, polysomnographic study involving 54 healthy volunteers who underwent two treatment periods (order randomized) each consisting of two nights in the laboratory: Night 1-lights out at usual bedtime; Night 2-4-h advance of sleep phase and randomization to either lurasidone 40 mg or placebo. The next morning impairment testing was carried out.

RESULTS

Lurasidone significantly (p < 0.05) increased total sleep time by an average of 28.4 min versus placebo, decreased wake time after sleep onset and wake time after the final awakening, and increased sleep efficiency. No other effects were found.

CONCLUSIONS

Lurasidone had a sleep maintenance effect without effects on sleep onset, rapid eye movement, or slow-wave sleep. Lurasidone is likely to be beneficial to patients with disturbed sleep, particularly those with sleep maintenance problems. Copyright © 2016 John Wiley & Sons, Ltd.

Role for serotonin2A (5-HT2A) and 2C (5-HT2C) receptors in experimental absence seizures

Absence seizures (ASs) are the hallmark of childhood/juvenile absence epilepsy. Monotherapy with first-line anti-absence drugs only controls ASs in 50% of patients, indicating the need for novel therapeutic targets. Since serotonin family-2 receptors (5-HT₂Rs) are known to modulate neuronal activity in the cortico-thalamo-cortical loop, the main network involved in AS generation, we investigated the effect of selective 5-HT_2AR and 5-HT_2CR ligands on ASs in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well established polygenic rat model of these non-convulsive seizures. GAERS rats were implanted with fronto-parietal EEG electrodes under general anesthesia, and their ASs were later recorded under freely moving conditions before and after intraperitoneal administration of various 5-HT_2AR and 5-HT_2CR ligands. The 5-HT_2A agonist TCB-2 dose-dependently decreased the total time spent in ASs, an effect that was blocked by the selective 5-HT_2A antagonist MDL11,939. Both MDL11,939 and another selective 5-HT_2A antagonist (M100,907) increased the length of individual seizures when injected alone. The 5-HT_2C agonists lorcaserin and CP-809,101 dose-dependently suppressed ASs, an effect blocked by the selective 5-HT_2C antagonist SB 242984. In summary, 5-HT_2ARs and 5-HT_2CRs negatively control the expression of experimental ASs, indicating that selective agonists at these 5-HT₂R subtypes might be potential novel anti-absence drugs.

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5-HT2AR activation decreases absence seizures in GAERS.

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5-HT2CR activation decreases absence seizures in GAERS.

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5-HT2AR blockade increases absence seizures in GAERS.

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5-HT2CR blockade does not affect absence seizures in GAERS.

Locus Coeruleus and Tuberomammillary Nuclei Ablations Attenuate Hypocretin/Orexin Antagonist-Mediated REM Sleep

Hypocretin 1 and 2 (Hcrts; also known as orexin A and B), excitatory neuropeptides synthesized in cells located in the tuberal hypothalamus, play a central role in the control of arousal. Hcrt inputs to the locus coeruleus norepinephrine (LC NE) system and the posterior hypothalamic histaminergic tuberomammillary nuclei (TMN HA) are important efferent pathways for Hcrt-induced wakefulness. The LC expresses Hcrt receptor 1 (HcrtR1), whereas HcrtR2 is found in the TMN. Although the dual Hcrt/orexin receptor antagonist almorexant (ALM) decreases wakefulness and increases NREM and REM sleep time, the neural circuitry that mediates these effects is currently unknown. To test the hypothesis that ALM induces sleep by selectively disfacilitating subcortical wake-promoting populations, we ablated LC NE neurons (LCx) or TMN HA neurons (TMNx) in rats using cell-type-specific saporin conjugates and evaluated sleep/wake following treatment with ALM and the GABA_A receptor modulator zolpidem (ZOL). Both LCx and TMNx attenuated the promotion of REM sleep by ALM without affecting ALM-mediated increases in NREM sleep. Thus, eliminating either HcrtR1 signaling in the LC or HcrtR2 signaling in the TMN yields similar effects on ALM-induced REM sleep without affecting NREM sleep time. In contrast, neither lesion altered ZOL efficacy on any measure of sleep–wake regulation. These results contrast with those of a previous study in which ablation of basal forebrain cholinergic neurons attenuated ALM-induced increases in NREM sleep time without affecting REM sleep, indicating that Hcrt neurotransmission influences distinct aspects of NREM and REM sleep at different locations in the sleep–wake regulatory network.

GABA-BZD Receptor Modulating Mechanism of Panax quinquefolius against 72-h Sleep Deprivation Induced Anxiety like Behavior: Possible Roles of Oxidative Stress, Mitochondrial Dysfunction and Neuroinflammation

Rationale:Panax quinquefolius (American Ginseng) is known for its therapeutic potential against various neurological disorders, but its plausible mechanism of action still remains undeciphered. GABA (Gamma Amino Butyric Acid) plays an important role in sleep wake cycle homeostasis. Thus, there exists rationale in exploring the GABA-ergic potential of Panax quinquefolius as neuroprotective strategy in sleep deprivation induced secondary neurological problems.

Objective: The present study was designed to explore the possible GABA-ergic mechanism in the neuro-protective effect of Panax quinquefolius against 72-h sleep deprivation induced anxiety like behavior, oxidative stress, mitochondrial dysfunction, HPA-axis activation and neuroinflammation.

Materials and Methods: Male laca mice were sleep deprived for 72-h by using Grid suspended over water method. Panax quinquefolius (American Ginseng 50, 100, and 200 mg/kg) was administered alone and in combination with GABA modulators (GABA Cl⁻ channel inhibitor, GABA-benzodiazepine receptor inhibitor and GABAA agonist) for 8 days, starting 5 days prior to 72-h sleep deprivation period. Various behavioral (locomotor activity, mirror chamber test), biochemical (lipid peroxidation, reduced glutathione, catalase, nitrite levels), mitochondrial complexes, neuroinflammation marker (Tumor Necrosis Factor, TNF-alpha), serum corticosterone, and histopathological sections of brains were assessed.

Results: Seventy two hours sleep deprivation significantly impaired locomotor activity, caused anxiety-like behavior, conditions of oxidative stress, alterations in mitochondrial enzyme complex activities, raised serum corticosterone levels, brain TNFα levels and led to neuroinflammation like signs in discrete brain areas as compared to naive group. Panax quinquefolius (100 and 200 mg/kg) treatment restored the behavioral, biochemical, mitochondrial, molecular and histopathological alterations. Pre-treatment of GABA Cl⁻ channel inhibitor as well as GABA-benzodiazepine receptor inhibitor, significantly reversed the protective effect of P. quinquefolius (100 mg/kg) in 72-h sleep deprived animals (P < 0.05). However, pretreatment with GABAA agonist, potentiated Panax quinquefolius's protective effect which was significant as compared to their effect per se (p < 0.05).

Conclusion: GABA-ergic mechanism could be involved in the neuroprotective effect of P.quinquefolius against sleep deprivation induced anxiety-like behavior, oxidative stress, mitochondrial dysfunction, HPA axis activation and neuroinflammation.

The Dual Hypocretin Receptor Antagonist Almorexant is Permissive for Activation of Wake-Promoting Systems

The dual hypocretin receptor (HcrtR) antagonist almorexant (ALM) may promote sleep through selective disfacilitation of wake-promoting systems, whereas benzodiazepine receptor agonists (BzRAs) such as zolpidem (ZOL) induce sleep through general inhibition of neural activity. Previous studies have indicated that HcrtR antagonists cause less-functional impairment than BzRAs. To gain insight into the mechanisms underlying these differential profiles, we compared the effects of ALM and ZOL on functional activation of wake-promoting systems at doses equipotent for sleep induction. Sprague-Dawley rats, implanted for EEG/EMG recording, were orally administered vehicle (VEH), 100 mg/kg ALM, or 100 mg/kg ZOL during their active phase and either left undisturbed or kept awake for 90 min after which their brains were collected. ZOL-treated rats required more stimulation to maintain wakefulness than VEH- or ALM-treated rats. We measured Fos co-expression with markers for wake-promoting cell groups in the lateral hypothalamus (Hcrt), tuberomammillary nuclei (histamine; HA), basal forebrain (acetylcholine; ACh), dorsal raphe (serotonin; 5HT), and singly labeled Fos(+) cells in the locus coeruleus (LC). Following SD, Fos co-expression in Hcrt, HA, and ACh neurons (but not in 5HT neurons) was consistently elevated in VEH- and ALM-treated rats, whereas Fos expression in these neuronal groups was unaffected by SD in ZOL-treated rats. Surprisingly, Fos expression in the LC was elevated in ZOL- but not in VEH- or ALM-treated SD animals. These results indicate that Hcrt signaling is unnecessary for the activation of Hcrt, HA, or ACh wake-active neurons, which may underlie the milder cognitive impairment produced by HcrtR antagonists compared to ZOL.

Effects of the 5-HT(1A) Receptor Agonist Tandospirone on ACTH-Induced Sleep Disturbance in Rats

The aim of this study was to compare the effect of the serotonin (5-HT)1A receptor agonist tandospirone versus that of the benzodiazepine hypnotic flunitrazepam in a rat model of long-term adrenocorticotropic hormone (ACTH)-induced sleep disturbance. Rats implanted with electrodes for recording electroencephalogram and electromyogram were injected with ACTH once daily at a dose of 100 µg/rat. Administration of ACTH for 10 d caused a significant increase in sleep latency, decrease in non-rapid eye movement (non-REM) sleep time, and increase in wake time. Tandospirone caused a significant decrease in sleep latency and increase in non-REM sleep time in rats treated with ACTH. The effect of tandospirone on sleep patterns was antagonized by the 5-HT1A receptor antagonist WAY-100635. In contrast, flunitrazepam had no significant effect on sleep parameters in ACTH-treated rats. These results clearly indicate that long-term administration of ACTH causes sleep disturbance, and stimulating the 5-HT1A receptor by tandospirone may be efficacious for improving sleep in cases in which benzodiazepine hypnotics are ineffective.

Elucidation of Molecular Mechanism(s) of Cognition Enhancing Activity of Bacomind®: A Standardized Extract of Bacopa Monnieri

Background:

Bacopa monnieri (L.) Wettst., commonly known as Brahmi, is renowned in Indian traditional system for its potent memory enhancing activity, which has been validated by various scientific studies.

Objective:

The objective of this study was to understand the molecular mechanism of memory enhancing activity of BacoMind^® (BM), a standardized extract of B. monnieri.

Materials and Methods:

BM was screened in vitro in a panel of cell-free and receptor-transfected cell assays. The purified enzymes/membrane homogenates/cells were incubated with substrate/standard ligand in the absence or presence of the test compound. The IC₅₀ values and EC₅₀ values were determined by nonlinear regression analysis of the concentration–response curves generated with mean replicate values using Hill equation curve fitting.

Results:

BM was found to inhibit three enzymes; Catechol-O-methyl transferase (COMT), Prolyl endopeptidase (PEP), and Poly (ADP-ribose) polymerase (PARP). It also had an antagonistic effect on serotonin 6 and 2A (5-HT₆ and 5-HT_2A) receptors_, known to influence the different neurological pathways, associated with memory and learning disorders, age-associated memory impairment.

Conclusion:

BM was found to inhibit three enzymes namely, Catechol-O-methyl transferase (COMT), Prolyl endopeptidase (PEP), and Poly (ADP-ribose) polymerase (PARP). It also exhibited an antagonistic effect on 5-HT₆ and 5-HT_2A receptors.

SUMMARY

This study was conducted to understand the molecular mechanism of memory enhancing activity of a standardized extract of B. monnieri by was screening it in vitro in a panel of cell-free and receptor-transfected cell assays. The purified enzymes/membrane homogenates/cells were incubated with substrate/standard ligand in the absence or presence of the test compound. BM was found to inhibit three enzymes; Catechol-O-methyl transferase (COMT), Prolyl endopeptidase (PEP), and Poly (ADP-ribose) polymerase (PARP). It also had an antagonistic effect on serotonin₆ and_2A (5-HT⁶ and 5-HT^2A) receptors, known to influence the different neurological pathways, associated with memory and learning disorders, age-associated memory impairment.

Abbreviations used: HTRF: Homogenous time resolved fluorescence, cAMP: Cyclic adenosine monophosphate, CHO: Chinese hamster ovary, RFU: Relative fluorescence unit, pNP: Para nitro phenol, AMC: 7-amino-4-methylcoumarin, ELISA: Enzyme linked immunosorbent assay, Z-Pro-Pro-CHO: Z-prolyl-prolinal, HEK: Human embryonic kidney, TE: Trolox equivalent.

Differentiated effects of the multimodal antidepressant vortioxetine on sleep architecture: Part 2, pharmacological interactions in rodents suggest a role of serotonin-3 receptor antagonism

Antidepressants often disrupt sleep. Vortioxetine, a multimodal antidepressant acting through serotonin (5-HT) transporter (SERT) inhibition, 5-HT3, 5-HT7 and 5-HT1D receptor antagonism, 5-HT1B receptor partial agonism, and 5-HT1A receptor agonism, had fewer incidences of sleep-related adverse events reported in depressed patients. In the accompanying paper a polysomnographic electroencephalography (sleep-EEG) study of vortioxetine and paroxetine in healthy subjects indicated that at low/intermediate levels of SERT occupancy, vortioxetine affected rapid eye movement (REM) sleep differently than paroxetine. Here we investigated clinically meaningful doses (80-90% SERT occupancy) of vortioxetine and paroxetine on sleep-EEG in rats to further elucidate the serotoninergic receptor mechanisms mediating this difference. Cortical EEG, electromyography (EMG), and locomotion were recorded telemetrically for 10 days, following an acute dose, from rats receiving vortioxetine-infused chow or paroxetine-infused water and respective controls. Sleep stages were manually scored into active wake, quiet wake, and non-REM or REM sleep. Acute paroxetine or vortioxetine delayed REM onset latency (ROL) and decreased REM episodes. After repeated administration, vortioxetine yielded normal sleep-wake rhythms while paroxetine continued to suppress REM. Paroxetine, unlike vortioxetine, increased transitions from non-REM to wake, suggesting fragmented sleep. Next, we investigated the role of 5-HT3 receptors in eliciting these differences. The 5-HT3 receptor antagonist ondansetron significantly reduced paroxetine's acute effects on ROL, while the 5-HT3 receptor agonist SR57227A significantly increased vortioxetine's acute effect on ROL. Overall, our data are consistent with the clinical findings that vortioxetine impacts REM sleep differently than paroxetine, and suggests a role for 5-HT3 receptor antagonism in mitigating these differences.

Pharmacological and pharmacokinetic properties of JNJ-40411813, a positive allosteric modulator of the mGlu2 receptor

Compounds modulating metabotropic glutamate type 2 (mGlu2) receptor activity may have therapeutic benefits in treating psychiatric disorders like schizophrenia and anxiety. The pharmacological and pharmacokinetic properties of a novel mGlu2 receptor-positive allosteric modulator (PAM), 1-butyl-3-chloro-4-(4-phenyl-1-piperidinyl)-2(1H)-pyridinone (JNJ-40411813/ADX71149) are described here. JNJ-40411813 acts as a PAM at the cloned mGlu2 receptor: EC50 = 147 ± 42 nmol/L in a [(35)S]GTPγS binding assay with human metabotropic glutamate type 2 (hmGlu2) CHO cells and EC50 = 64 ± 29 nmol/L in a Ca(2+) mobilization assay with hmGlu2 G α16 cotransfected HEK293 cells. [(35)S]GTPγS autoradiography on rat brain slices confirmed PAM activity of JNJ-40411813 on native mGlu2 receptor. JNJ-40411813 displaced [(3)H]JNJ-40068782 and [(3)H]JNJ-46281222 (mGlu2 receptor PAMs), while it failed to displace [(3)H]LY341495 (a competitive mGlu2/3 receptor antagonist). In rats, JNJ-40411813 showed ex vivo mGlu2 receptor occupancy using [(3)H]JNJ-46281222 with ED50 of 16 mg/kg (p.o.). PK-PD modeling using the same radioligand resulted in an EC50 of 1032 ng/mL. While JNJ-40411813 demonstrated moderate affinity for human 5HT2A receptor in vitro (K b = 1.1 μmol/L), higher than expected 5HT2A occupancy was observed in vivo (in rats, ED50 = 17 mg/kg p.o.) due to a metabolite. JNJ-40411813 dose dependently suppressed REM sleep (LAD, 3 mg/kg p.o.), and promoted and consolidated deep sleep. In fed rats, JNJ-40411813 (10 mg/kg p.o.) was rapidly absorbed (C max 938 ng/mL at 0.5 h) with an absolute oral bioavailability of 31%. Collectively, our data show that JNJ-40411813 is an interesting candidate to explore the therapeutic potential of mGlu2 PAMs, in in vivo rodents experiments as well as in clinical studies.

Homeostatic sleep pressure is the primary factor for activation of cortical nNOS/NK1 neurons

Cortical interneurons, immunoreactive for neuronal nitric oxide synthase (nNOS) and the receptor NK1, express the functional activity marker Fos selectively during sleep. NREM sleep 'pressure' is hypothesized to accumulate during waking and to dissipate during sleep. We reported previously that the proportion of Fos(+) cortical nNOS/NK1 neurons is correlated with established electrophysiological markers of sleep pressure. As these markers covary with the amount of NREM sleep, it remained unclear whether cortical nNOS/NK1 neurons are activated to the same degree throughout NREM sleep or whether the extent of their activation is related to the sleep pressure that accrued during the prior waking period. To distinguish between these possibilities, we used hypnotic medications to control the amount of NREM sleep in rats while we varied prior wake duration and the resultant sleep pressure. Drug administration was preceded by 6 h of sleep deprivation (SD) ('high sleep pressure') or undisturbed conditions ('low sleep pressure'). We find that the proportion of Fos(+) cortical nNOS/NK1 neurons was minimal when sleep pressure was low, irrespective of the amount of time spent in NREM sleep. In contrast, a large proportion of cortical nNOS/NK1 neurons was Fos(+) when an equivalent amount of sleep was preceded by SD. We conclude that, although sleep is necessary for cortical nNOS/NK1 neuron activation, the proportion of cells activated is dependent upon prior wake duration.

Functional profile of a novel modulator of serotonin, dopamine, and glutamate neurotransmission

RATIONALE

Schizophrenia remains among the most prevalent neuropsychiatric disorders, and current treatment options are accompanied by unwanted side effects. New treatments that better address core features of the disease with minimal side effects are needed.

OBJECTIVES

As a new therapeutic approach, 1-(4-fluoro-phenyl)-4-((6bR, 10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H,7H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxalin-8-yl)-butan-1-one (ITI-007) is currently in human clinical trials for the treatment of schizophrenia. Here, we characterize the preclinical functional activity of ITI-007.

RESULTS

ITI-007 is a potent 5-HT2A receptor ligand (K i  = 0.5 nM) with strong affinity for dopamine (DA) D2 receptors (K i  = 32 nM) and the serotonin transporter (SERT) (K i  = 62 nM) but negligible binding to receptors (e.g., H1 histaminergic, 5-HT2C, and muscarinic) associated with cognitive and metabolic side effects of antipsychotic drugs. In vivo it is a 5-HT2A antagonist, blocking (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI)-induced headtwitch in mice with an inhibitory dose 50 (ID50) = 0.09 mg/kg, per oral (p.o.), and has dual properties at D2 receptors, acting as a postsynaptic D2 receptor antagonist to block D-amphetamine hydrochloride (D-AMPH) hyperlocomotion (ID50 = 0.95 mg/kg, p.o.), yet acting as a partial agonist at presynaptic striatal D2 receptors in assays measuring striatal DA neurotransmission. Further, in microdialysis studies, this compound significantly and preferentially enhances mesocortical DA release. At doses relevant for antipsychotic activity in rodents, ITI-007 has no demonstrable cataleptogenic activity. ITI-007 indirectly modulates glutamatergic neurotransmission by increasing phosphorylation of GluN2B-type N-methyl-D-aspartate (NMDA) receptors and preferentially increases phosphorylation of glycogen synthase kinase 3β (GSK-3β) in mesolimbic/mesocortical dopamine systems.

CONCLUSION

The combination of in vitro and in vivo activities of this compound support its development for the treatment of schizophrenia and other psychiatric and neurologic disorders.

Hypocretin/orexin antagonism enhances sleep-related adenosine and GABA neurotransmission in rat basal forebrain

Hypocretin/orexin (HCRT) neurons provide excitatory input to wake-promoting brain regions including the basal forebrain (BF). The dual HCRT receptor antagonist almorexant (ALM) decreases waking and increases sleep. We hypothesized that HCRT antagonists induce sleep, in part, through disfacilitation of BF neurons; consequently, ALM should have reduced efficacy in BF-lesioned (BFx) animals. To test this hypothesis, rats were given bilateral IgG-192-saporin injections, which predominantly targets cholinergic BF neurons. BFx and intact rats were then given oral ALM, the benzodiazepine agonist zolpidem (ZOL) or vehicle (VEH) at lights-out. ALM was less effective than ZOL at inducing sleep in BFx rats compared to controls. BF adenosine (ADO), γ-amino-butyric acid (GABA), and glutamate levels were then determined via microdialysis from intact, freely behaving rats following oral ALM, ZOL or VEH. ALM increased BF ADO and GABA levels during waking and mixed vigilance states, and preserved sleep-associated increases in GABA under low and high sleep pressure conditions. ALM infusion into the BF also enhanced cortical ADO release, demonstrating that HCRT input is critical for ADO signaling in the BF. In contrast, oral ZOL and BF-infused ZOL had no effect on ADO levels in either BF or cortex. ALM increased BF ADO (an endogenous sleep-promoting substance) and GABA (which is increased during normal sleep), and required an intact BF for maximal efficacy, whereas ZOL blocked sleep-associated BF GABA release, and required no functional contribution from the BF to induce sleep. ALM thus induces sleep by facilitating the neural mechanisms underlying the normal transition to sleep.

Piromelatine exerts antinociceptive effect via melatonin, opioid, and 5HT1A receptors and hypnotic effect via melatonin receptors in a mouse model of neuropathic pain

RATIONALE

An effective and safe treatment of insomnia in patients with neuropathic pain remains an unmet need. Melatonin and its analogs have been shown to have both analgesic and hypnotic effects; however, capacity of them on sleep disturbance with neuropathic pain as well as the precise mechanism is unclear.

OBJECTIVE

The present study evaluated effects of piromelatine, a novel melatonin receptor agonist, on sleep disturbance in a neuropathic pain-like condition as well as the underlying mechanisms.

METHODS

A mouse model of chronic neuropathic pain induced by partial sciatic nerve ligation (PSL) was employed. The antinociceptive and hypnotic effects of piromelatine were evaluated by measurement of thermal hyperalgesia, mechanical allodynia, and electroencephalogram (EEG) recordings in PSL mice. Pharmacological approaches were used to clarify the mechanisms of action of piromelatine.

RESULTS

PSL significantly lowered thermal and mechanical latencies and decreased non-rapid eye movement (NREM) sleep, and PSL mice exhibited sleep fragmentation. Treatment with 25, 50, or 100 mg/kg of piromelatine significantly prolonged thermal and mechanical latencies and increased NREM sleep. Moreover, the antinociceptive effect of piromelatine was prevented by melatonin antagonist luzindole, opioid receptor antagonist naloxone, or 5HT1A receptor antagonist WAY-100635. The hypnotic effect of piromelatine was blocked by luzindole but neither by naloxone nor WAY-100635.

CONCLUSIONS

These data indicate that piromelatine is an effective treatment for both neuropathic pain and sleep disturbance in PSL mice. The antinociceptive effect of piromelatine is likely mediated by melatonin, opioid, and 5HT1A receptors; however, the hypnotic effect of piromelatine appears to be mediated by melatonin receptors.

Add-on clinical effects of selective antagonist of 5HT6 receptors AVN-211 (CD-008-0173) in patients with schizophrenia stabilized on antipsychotic treatment: pilot study

The serotoninergic system as a target for add-on treatment seems to be a promising approach in patients with schizophrenia.

OBJECTIVE

To clarify if selective 5HT-6 antagonist AVN-211 (CD-008-0173) adds clinical and cognitive effects to stable antipsychotic treatment.

METHODS

A randomized, double-blind, placebo-controlled, add-on, 4r-week trial in 47 schizophrenia patients (21 patients receiving study drug and 26 receiving placebo) who were stabilized on antipsychotic medication was performed. Seventeen patients from the study drug group and 25 patients from the placebo group completed the trial. Treatment effects were measured using clinical rating scales and attention tests.

RESULTS

With no differences at baseline, there was a significant difference between the groups in Positive and Negative Syndrome Scale (PANSS) positive subscale score (p = 0.058) in favor of patients in the treatment group at the endpoint. The PANSS positive subscore (p = 0.0068) and Clinical Global Impression-Severity (CGI-S) (p = 0.048) score significantly changed only in the treatment group. Only in the placebo group were significant changes in Calgary Depression Rating Scale (CDRS) total score registered. The indices of attention tests at endpoint did not show differences between the groups, with the exception of the scope of change in the results of the subtest VIII of the Wechsler Adult Intelligence Scale (WAIS), which showed difference between the groups (p = 0.02) and was significantly larger in the treatment group. Only inside the study drug group, significant changes in selectivity and continuous attention were observed regarding total correct responses (p = 0.0038) and reaction time (p = 0.058) in the Continuous Attention Task (CAT) test.

CONCLUSION

Selective 5HT6 antagonist AVN-211 (CD-008-0173) added antipsychotic and some procognitive (attention) effects to antipsychotic medication.

The hypocretin/orexin antagonist almorexant promotes sleep without impairment of performance in rats

The hypocretin receptor (HcrtR) antagonist almorexant (ALM) has potent hypnotic actions but little is known about neurocognitive performance in the presence of ALM. HcrtR antagonists are hypothesized to induce sleep by disfacilitation of wake-promoting systems whereas GABA_A receptor modulators such as zolpidem (ZOL) induce sleep through general inhibition of neural activity. To test the hypothesis that less functional impairment results from HcrtR antagonist-induced sleep, we evaluated the performance of rats in the Morris Water Maze in the presence of ALM vs. ZOL. Performance in spatial reference memory (SRM) and spatial working memory (SWM) tasks were assessed during the dark period after equipotent sleep-promoting doses (100 mg/kg, po) following undisturbed and sleep deprivation (SD) conditions. ALM-treated rats were indistinguishable from vehicle (VEH)-treated rats for all SRM performance measures (distance traveled, latency to enter, time within, and number of entries into, the target quadrant) after both the undisturbed and 6 h SD conditions. In contrast, rats administered ZOL showed impairments in all parameters measured compared to VEH or ALM in the undisturbed conditions. Following SD, ZOL-treated rats also showed impairments in all measures. ALM-treated rats were similar to VEH-treated rats for all SWM measures (velocity, time to locate the platform and success rate at finding the platform within 60 s) after both the undisturbed and SD conditions. In contrast, ZOL-treated rats showed impairments in velocity and in the time to locate the platform. Importantly, ZOL rats only completed the task 23–50% of the time while ALM and VEH rats completed the task 79–100% of the time. Thus, following equipotent sleep-promoting doses, ZOL impaired rats in both memory tasks while ALM rats performed at levels comparable to VEH rats. These results are consistent with the hypothesis that less impairment results from HcrtR antagonism than from GABA_A-induced inhibition.

Traditional Japanese medicine, Yokukansan, for the treatment of nocturnal enuresis in children

BACKGROUND

The major pathogenic factors involved in nocturnal enuresis are nocturnal polyuria, small bladder capacity and/or detrusor overactivity, and a high arousal threshold. Desmopressin is the first-line therapy for the patients with diuresis-dependent nocturnal enuresis. Yokukansan, a traditional Japanese medicine, has been used in Japan to treat patients with nervousness, insomnia, and children with night terrors and temper tantrums. We experienced the positive effect of Yokukansan in some of the patients who did not respond well to desmopressin therapy.

METHODS

In total, 32 children with monosymptomatic nocturnal enuresis with nocturnal polyuria were treated with oral desmopressin melt tablets, which were approved for clinical use in Japan on 29 May 2012. This treatment was effective for 14 of them. For the rest (n = 18), Yokukansan was introduced in combination with desmopressin.

RESULTS

Yokukansan was effective for 12 out of the 18 cases.

CONCLUSIONS

Yokukansan should be a candidate for the medication of nocturnal enuresis.

A role for cortical nNOS/NK1 neurons in coupling homeostatic sleep drive to EEG slow wave activity

Although the neural circuitry underlying homeostatic sleep regulation is little understood, cortical neurons immunoreactive for neuronal nitric oxide synthase (nNOS) and the neurokinin-1 receptor (NK1) have been proposed to be involved in this physiological process. By systematically manipulating the durations of sleep deprivation and subsequent recovery sleep, we show that activation of cortical nNOS/NK1 neurons is directly related to non-rapid eye movement (NREM) sleep time, NREM bout duration, and EEG δ power during NREM sleep, an index of preexisting homeostatic sleep drive. Conversely, nNOS knockout mice show reduced NREM sleep time, shorter NREM bouts, and decreased power in the low δ range during NREM sleep, despite constitutively elevated sleep drive. Cortical NK1 neurons are still activated in response to sleep deprivation in these mice but, in the absence of nNOS, they are unable to up-regulate NREM δ power appropriately. These findings support the hypothesis that cortical nNOS/NK1 neurons translate homeostatic sleep drive into up-regulation of NREM δ power through an NO-dependent mechanism.

A new perspective for schizophrenia: TAAR1 agonists reveal antipsychotic- and antidepressant-like activity, improve cognition and control body weight

Schizophrenia is a chronic, severe and highly complex mental illness. Current treatments manage the positive symptoms, yet have minimal effects on the negative and cognitive symptoms, two prominent features of the disease with critical impact on the long-term morbidity. In addition, antipsychotic treatments trigger serious side effects that precipitate treatment discontinuation. Here, we show that activation of the trace amine-associated receptor 1 (TAAR1), a modulator of monoaminergic neurotransmission, represents a novel therapeutic option. In rodents, activation of TAAR1 by two novel and pharmacologically distinct compounds, the full agonist RO5256390 and the partial agonist RO5263397, blocks psychostimulant-induced hyperactivity and produces a brain activation pattern reminiscent of the antipsychotic drug olanzapine, suggesting antipsychotic-like properties. TAAR1 agonists do not induce catalepsy or weight gain; RO5263397 even reduced haloperidol-induced catalepsy and prevented olanzapine from increasing body weight and fat accumulation. Finally, TAAR1 activation promotes vigilance in rats and shows pro-cognitive and antidepressant-like properties in rodent and primate models. These data suggest that TAAR1 agonists may provide a novel and differentiated treatment of schizophrenia as compared with current medication standards: TAAR1 agonists may improve not only the positive symptoms but also the negative symptoms and cognitive deficits, without causing adverse effects such as motor impairments or weight gain.

Activation of 5-HT6 receptors modulates sleep-wake activity and hippocampal theta oscillation

The modulatory role of 5-HT neurons and a number of different 5-HT receptor subtypes has been well documented in the regulation of sleep-wake cycles and hippocampal activity. A high level of 5-HT(6) receptor expression is present in the rat hippocampus. Further, hippocampal function has been shown to be modulated by both 5-HT(6) agonists and antagonists. In the current study, the potential involvement of 5-HT(6) receptors in the control of hippocampal theta rhythms and sleep-wake cycles has been investigated. Hippocampal activity was recorded by intracranial hippocampal electrodes both in anesthetized (n = 22) and in freely moving rats (n = 9). Theta rhythm was monitored in different sleep-wake states in freely moving rats and was elicited by stimulation of the brainstem reticular formation under anesthesia. Changes in theta frequency and power were analyzed before and after injection of the 5-HT(6) antagonist (SAM-531) and the 5-HT(6) agonist (EMD386088). In freely moving rats, EMD386088 suppressed sleep for several hours and significantly decreased theta peak frequency, while, in anesthetized rats, EMD386088 had no effect on theta power but significantly decreased theta frequency, which could be blocked by coadministration of SAM-531. SAM-531 alone did not change sleep-wake patterns and had no effect on theta parameters in both unanesthetized and anesthetized rats. Decreases in theta frequency induced by the 5-HT(6) receptor agonist correspond to previously described electrophysiological patterns shared by all anxiolytic drugs, and it is in line with its behavioral anxiolytic profile. The 5-HT(6) antagonist, however, failed to potentiate theta power, which is characteristic of many pro-cognitive substances, indicating that 5-HT(6) receptors might not tonically modulate hippocampal oscillations and sleep-wake patterns.

Further evidence for the sleep-promoting effects of 5-HT₂A receptor antagonists and demonstration of synergistic effects with the hypnotic, zolpidem in rats

5-Hydroxytryptamine (5-HT)2A antagonists are promising therapeutic agents for the treatment of sleep maintenance insomnias, but unlike hypnotics, they have limited effects on sleep initiation. This study evaluated the effects of several 5-HT₂A antagonists (eplivanserin, volinanserin and AVE8488) alone and/or in combination with the short-acting hypnotic, zolpidem, on the rat sleep profile. A repeated-measures design was used in which rats were treated with eplivanserin (3 and 10 mg/kg, i.p. or p.o.), volinanserin (0.3-3 mg/kg, i.p.), AVE8488 (0.1-3 mg/kg, i.p.) and zolpidem (3 and 10 mg/kg, p.o.). In addition, animals received a combination of eplivanserin (3 mg/kg, p.o.) and zolpidem (3 mg/kg, p.o.). Electroencephalogram was analyzed for 6 h after administration. Eplivanserin did not modify wakefulness and non-rapid eye movement sleep (NREMS), while zolpidem (10 mg/kg po) induced a marked increase in NREMS duration. Volinanserin (1 and 3 mg/kg) and AVE8488 (0.3 mg/kg) similarly increased NREMS, while reducing wakefulness. Moreover, the 5-HT₂A antagonists and, to a lesser extent, zolpidem, increased duration of NREMS episodes, while decreasing their frequency. When eplivanserin was co-administered with zolpidem, a synergistic effect was observed as the combination produced an increase in NREMS time and bouts duration. These findings confirm further that 5-HT₂A antagonists promote the maintenance of sleep, and suggest that combining a 5-HT₂A antagonist with a short-acting hypnotic may be a useful strategy for the treatment of insomnia.

Trace amine-associated receptor 1 partial agonism reveals novel paradigm for neuropsychiatric therapeutics

BACKGROUND

Trace amines, compounds structurally related to classical biogenic amines, represent endogenous ligands of the trace amine-associated receptor 1 (TAAR1). Because trace amines also influence the activity of other targets, selective ligands are needed for the elucidation of TAAR1 function. Here we report on the identification and characterization of the first selective and potent TAAR1 partial agonist.

METHODS

The TAAR1 partial agonist RO5203648 was evaluated for its binding affinity and functional activity at rodent and primate TAAR1 receptors stably expressed in HEK293 cells, for its physicochemical and pharmacokinetic properties, for its effects on the firing frequency of monoaminergic neurons ex vivo, and for its properties in vivo with genetic and pharmacological models of central nervous system disorders.

RESULTS

RO5203648 showed high affinity and potency at TAAR1, high selectivity versus other targets, and favorable pharmacokinetic properties. In mouse brain slices, RO5203648 increased the firing frequency of dopaminergic and serotonergic neurons in the ventral tegmental area and the dorsal raphe nucleus, respectively. In various behavioral paradigms in rodents and monkeys, RO5203648 demonstrated clear antipsychotic- and antidepressant-like activities as well as potential anxiolytic-like properties. Furthermore, it attenuated drug-taking behavior and was highly effective in promoting attention, cognitive performance, and wakefulness.

CONCLUSIONS

With the first potent and selective TAAR1 partial agonist, RO5203648, we show that TAAR1 is implicated in a broad range of relevant physiological, behavioral, and cognitive neuropsychiatric dimensions. Collectively, these data uncover important neuromodulatory roles for TAAR1 and suggest that agonists at this receptor might have therapeutic potential in one or more neuropsychiatric domains.

Neuropharmacology of Sleep and Wakefulness: 2012 Update

The development of sedative/hypnotic molecules has been empiric rather than rational. The empiric approach has produced clinically useful drugs but for no drug is the mechanism of action completely understood. All available sedative/hypnotic medications have unwanted side effects and none of these medications creates a sleep architecture that is identical to the architecture of naturally occurring sleep. This chapter reviews recent advances in research aiming to elucidate the neurochemical mechanisms regulating sleep and wakefulness. One promise of rational drug design is that understanding the mechanisms of sedative/hypnotic action will significantly enhance drug safety and efficacy.

Dual hypocretin receptor antagonism is more effective for sleep promotion than antagonism of either receptor alone

The hypocretin (orexin) system is involved in sleep/wake regulation, and antagonists of both hypocretin receptor type 1 (HCRTR1) and/or HCRTR2 are considered to be potential hypnotic medications. It is currently unclear whether blockade of either or both receptors is more effective for promoting sleep with minimal side effects. Accordingly, we compared the properties of selective HCRTR1 (SB-408124 and SB-334867) and HCRTR2 (EMPA) antagonists with that of the dual HCRTR1/R2 antagonist almorexant in the rat. All 4 antagonists bound to their respective receptors with high affinity and selectivity in vitro. Since in vivo pharmacokinetic experiments revealed poor brain penetration for SB-408124, SB-334867 was selected for subsequent in vivo studies. When injected in the mid-active phase, SB-334867 produced small increases in rapid-eye-movement (REM) and non-REM (NR) sleep. EMPA produced a significant increase in NR only at the highest dose studied. In contrast, almorexant decreased NR latency and increased both NR and REM proportionally throughout the subsequent 6 h without rebound wakefulness. The increased NR was due to a greater number of NR bouts; NR bout duration was unchanged. At the highest dose tested (100 mg/kg), almorexant fragmented sleep architecture by increasing the number of waking and REM bouts. No evidence of cataplexy was observed. HCRTR1 occupancy by almorexant declined 4–6 h post-administration while HCRTR2 occupancy was still elevated after 12 h, revealing a complex relationship between occupancy of HCRT receptors and sleep promotion. We conclude that dual HCRTR1/R2 blockade is more effective in promoting sleep than blockade of either HCRTR alone. In contrast to GABA receptor agonists which induce sleep by generalized inhibition, HCRTR antagonists seem to facilitate sleep by reducing waking “drive”.

Translational evaluation of JNJ-18038683, a 5-hydroxytryptamine type 7 receptor antagonist, on rapid eye movement sleep and in major depressive disorder

In rodents 5-hydroxytryptamine type 7 (5-HT(7)) receptor blockade has been shown to be effective in models of depression and to increase the latency to rapid eye movement (REM) sleep and decrease REM duration. In the clinic, the REM sleep reduction observed with many antidepressants may serve as a biomarker. We report here the preclinical and clinical evaluation of a 5-HT(7) receptor antagonist, (3-(4-chlorophenyl)-1,4,5,6,7,8-hexahydro-1-(phenylmethyl)pyrazolo[3,4-d]azepine 2-hydroxy-1,2,3-propanetricarboxylate) (JNJ-18038683). In rodents, JNJ-18038683 increased the latency to REM sleep and decreased REM duration, and this effect was maintained after repeated administration for 7 days. The compound was effective in the mouse tail suspension test. JNJ-18038683 enhanced serotonin transmission, antidepressant-like behavior, and REM sleep suppression induced by citalopram in rodents. In healthy human volunteers JNJ-18038683 prolonged REM latency and reduced REM sleep duration, demonstrating that the effect of 5-HT(7) blockade on REM sleep translated from rodents to humans. Like in rats, JNJ-18038683 enhanced REM sleep suppression induced by citalopram in humans, although a drug-drug interaction could not be ruled out. In a double-blind, active, and placebo-controlled clinical trial in 225 patients suffering from major depressive disorder, neither treatment with pharmacologically active doses of JNJ-18038683 or escitalopram separated from placebo, indicating a failed study lacking assay sensitivity. Post hoc analyses using an enrichment window strategy, where all the efficacy data from sites with an implausible high placebo response [placebo group Montgomery-Åsberg Depression Rating Scale (MADRS) < = 12] and from sites with no placebo response (MADRS > = 28) are removed, there was a clinically meaningful difference between JNJ-18038683 and placebo. Further clinical studies are required to characterize the potential antidepressant efficacy of JNJ-18038683.