Antagonism of serotonergic 5-HT2A/2C receptors: mutual improvement of sleep, cognition and mood?

Early-life manipulation of the serotonergic system exacerbates the harmful effects of sleep deprivation on cognitive functions

Serotonin is a monoamine neurotransmitter that plays a main role in regulating physiological and cognitive functions. Serotonergic system dysfunction is involved in the etiology of various psychiatric and neurological disorders. Therefore, the present study was designed to investigate the effects of early-life serotonin depletion on cognitive disorders caused by sleep deprivation. Serotonin was depleted by para-chlorophenylalanine (PCPA, 100 mg/kg, s.c.) at postnatal days 10-20, followed by sleep deprivation-induced through the multiple platform apparatus for 24 h at PND 60. After the examination of the novel object recognition and passive avoidance memories, the hippocampi and prefrontal cortex were dissected to examine the brain-derived neurotrophic factor (BDNF) mRNA expression by PCR. Our findings showed that postnatal serotonin depletion and sleep deprivation impaired the novel object recognition and passive avoidance memories and changed the BDNF levels. In the same way, the serotonin depletion in early life before sleep deprivation exacerbated the harmful effects of sleep deprivation on cognitive function and BDNF levels. It can be claimed that the serotonergic system plays a main role in the modulation of sleep and cognitive functions.

Serotonin regulation of mitochondria in kidney diseases

Serotonin, while conventionally recognized as a neurotransmitter in the CNS, has recently gained attention for its role in the kidney. Specifically, serotonin is not only synthesized in the kidney, but it also regulates glomerular function, vascular resistance, and mitochondrial homeostasis. Because of serotonin's importance to mitochondrial health, this review is focused on the role of serotonin and its receptors in mitochondrial function in the context of acute kidney injury, chronic kidney disease, and diabetic kidney disease, all of which are characterized by mitochondrial dysfunction and none of which has approved pharmacological treatments. Evidence indicates that activation of certain serotonin receptors can stimulate mitochondrial biogenesis (MB) and restore mitochondrial homeostasis, resulting in improved renal function. Serotonin receptor agonists that induce MB are therefore of interest as potential therapeutic strategies for renal injury and disease. SIGNIFICANCE STATEMENT: Mitochondrial dysfunction is associated with many human renal diseases such as acute kidney injury, chronic kidney disease, and diabetic kidney disease, which are associated with increased morbidity and mortality. Unfortunately, none of these pathologies has an FDA-approved pharmacological intervention, underscoring the urgency of identifying new therapeutics for such disorders. Studies show that induction of mitochondrial biogenesis via serotonin (5-hydroxytryptamine, 5-HT) receptors reduces kidney injury markers, restores mitochondrial and renal function after kidney injury, and decreases mortality, suggesting that targeting 5-HT receptors may be a promising therapeutic avenue for mitochondrial dysfunction in kidney diseases. While numerous reviews describe the importance of mitochondria and mitochondrial quality control mechanisms in kidney disease, the relevance of 5-HT receptor-mediated mitochondrial metabolic modulation in the kidney has yet to be thoroughly explored.

Sleep alterations as a function of 88 health indicators

BACKGROUND

Alterations in sleep have been described in multiple health conditions and as a function of several medication effects. However, evidence generally stems from small univariate studies. Here, we apply a large-sample, data-driven approach to investigate patterns between in sleep macrostructure, quantitative sleep EEG, and health.

METHODS

We use data from the MrOS Sleep Study, containing polysomnography and health data from a large sample (N = 3086) of elderly American men to establish associations between sleep macrostructure, the spectral composition of the electroencephalogram, 38 medical disorders, 2 health behaviors, and the use of 48 medications.

RESULTS

Of sleep macrostructure variables, increased REM latency and reduced REM duration were the most common findings across health indicators, along with increased sleep latency and reduced sleep efficiency. We found that the majority of health indicators were not associated with objective EEG power spectral density (PSD) alterations. Associations with the rest were highly stereotypical, with two principal components accounting for 85-95% of the PSD-health association. PC1 consists of a decrease of slow and an increase of fast PSD components, mainly in NREM. This pattern was most strongly associated with depression/SSRI medication use and age-related disorders. PC2 consists of changes in mid-frequency activity. Increased mid-frequency activity was associated with benzodiazepine use, while decreases were associated with cardiovascular problems and associated medications, in line with a recently proposed hypothesis of immune-mediated circadian demodulation in these disorders. Specific increases in sleep spindle frequency activity were associated with taking benzodiazepines and zolpidem. Sensitivity analyses supported the presence of both disorder and medication effects.

CONCLUSIONS

Sleep alterations are present in various health conditions.

Efficacy and safety of agomelatine in epilepsy patients with sleep and mood disorders: An observational, retrospective cohort study

OBJECTIVE

To evaluate the therapeutic efficacy and safety of agomelatine for treating the sleep and mood disorders in epilepsy patients.

METHODS

Retrospective data were derived from 113 epilepsy patients for at least 8 weeks. All the subjects were divided into two groups, one was treated with agomelatine, the other was treated with escitalopram. Their depression and anxiety states were assessed by Hamilton Depression (HAMD) and Hamilton Anxiety (HAMA) Scales. Sleep quality was assessed by the Pittsburgh Sleep Quality Index (PSQI).

RESULTS

The HAMA, HAMD and PSQI scores in both groups significantly declined after the treatments with agomelatine and escitalopram. However, the agomelatine group exhibited greater improvement in terms of HAMA and PSQI scores compared to the escitalopram group. No severe adverse events were observed in agomelatine group.

SIGNIFICANCE

Agomelatine performed better in HAMA and PSQI scores compared to escitalopram, where no significant increase in seizure frequency or side effects were observed. Possibly, agomelatine presents a promising therapeutic option for treating the sleep or mood disorders in epilepsy patients.

Genetic polymorphism in HTR2A rs6313 is associated with internet addiction disorder

Introduction

Internet addiction disorder (IAD) has grown into public health concern of global proportions. Previous studies have indicated that individuals with IAD may exhibit altered levels of serotonin and dopamine, which are known to play crucial roles in depression, anxiety, impulsivity, and addiction. Therefore, polymorphisms in the receptors that mediate the effects of serotonin and dopamine and affect their functional states as well as their activities are suspect. In this study, we aimed to investigate the association between IAD and rs6313 (T102C) polymorphism in the serotonin 2A receptor (5-HT2A) gene, (HTR2A).

Methods

Twenty patients with IAD and twenty healthy controls (HCs) were included in this study. Young's Internet Addiction Test (IAT), Self-Rating Anxiety Scale, Self-Rating Depression Scale, Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), Barratt Impulse Scale, Pittsburgh Sleep Quality Index (PSQI), and Social Support Rating Scale (SSRS) were used to assess the severity of internet addiction, mental status, impulsive traits, sleep quality, and social support. Genotyping was performed to identify rs6313 polymorphisms in the HTR2A gene of all participants.

Results

The frequencies of the C and T alleles of HTR2A T102C were 28% and 72% in the IAD group and 53% and 47% in the HCs group, respectively, indicating that the differences between these two groups were significant. No significant difference was observed in the distribution of the CC, CT, and TT genotypes of HTR2A gene T102C between the IAD and the HCs groups. Additionally, there was no difference in the distribution of the frequencies of the HTR2A gene T102C CC and CT+TT genotypes between the two groups. However, the distribution between the TT and CC+CT genotypes showed an apparent statistical difference in the HTR2A gene T102C between the two groups. Correlation analysis indicated that the IAT score was positively correlated with the Y-BOCS and BIS scores for the CC+CT genotype in patients with IAD. Moreover, the IAT score was positively correlated with the PSQI score in patients with IAD carrying the TT genotype.

Conclusion

The present study demonstrates that rs6313 in HTR2A is associated with IAD, and that the T allele of rs6313 in HTR2A may be a risk factor for IAD.

Role of Serotonergic System in Regulating Brain Tumor-Associated Neuroinflammatory Responses

Serotonin signaling regulates wide arrays of both neural and extra-neural functions. Serotonin is also found to affect cancer progression directly as well as indirectly by modulating the immune cells. In the brain, serotonin plays a key role in regulating various functions; disturbance of the normal activities of serotonin leads to various mental illnesses, including the neuroinflammatory response in the central nervous system (CNS). The neuroinflammatory response can be initiated in various psychological illnesses and brain cancer. Serotonergic signaling can impact the functions of both glial as well as the immune cells. It can also affect the tumor immune microenvironment and the inflammatory response associated with brain cancers. Apart from this, many drugs used for treatment of psychological illness are known to modulate serotonergic system and can cross the blood-brain barrier. Understanding the role of serotonergic pathways in regulating neuroinflammatory response and brain cancer will provide a new paradigm in modulating the serotonergic components in treating brain cancer and associated inflammation-induced brain damages.

Herbal medicines for insomnia through regulating 5-hydroxytryptamine receptors: a systematic review

Insomnia is a common sleep disorder without effective therapy and can affect a person's life. The mechanism of the disease is not completely understood. Hence, there is a need to understand the targets related to insomnia, in order to develop innovative therapies and new compounds. Recently, increasing interest has been focused on complementary and alternative medicines for treating or preventing insomnia. Research into their molecular components has revealed that their sedative and sleep-promoting properties rely on the interactions with various neurotransmitter systems in the brain. In this review, the role of 5-hydroxytryptamine (5-HT) in insomnia development is summarized, while a systematic analysis of studies is conducted to assess the mechanisms of herbal medicines on different 5-HT receptors subtypes, in order to provide reference for subsequent research.

The Effect of Agomelatine in Behavioral and Psychological Symptoms of Dementia

OBJECTIVE

Moderate and severe behavioral and psychological symptoms of dementia (BPSD) often need medical treatment to improve symptoms. Agomelatine is a selective melatonergic (MT1/MT2) agonist that has normalizing effects on disturbed circadian rhythms and disrupted sleep-wake cycles. Its activity of 5HT-2C receptor antagonism is associated with lessening depression and anxiety and increasing slow-wave sleep. Based on past clinical records and current findings it suggests that agomelatine can improve BPSD for patients. This retrospective cohort study was designed to compare the BPSD before and after using agomelatine.

METHODS

Records of dementia cases who had ever received agomelatine treatment for BPSD in a general hospital setting during the past 2.5 years were identified and reviewed. Scores from before and after 3 months of treatment with agomelatine were collected for Neuropsychiatric Inventory (NPI), Brief Psychiatric Rating Scale (BPRS), and Clinical Global Impression (CGI) to compare and analyze the difference of psychological and behavioral symptoms pre- and post-agomelatine used.

RESULTS

Records of 144 cases of dementia with BPSD who had ever used agomelatine from January 2015 to June 2017 were collected. All of the 112 cases had BPRS and CGI scores, of which 75 cases had additional NPI scores. Among these 112 cases, the BPRS and CGI scores were significantly improved in all types of dementia. NPI scores indicated that the use of agomelatine alleviated obvious symptoms and decreased overall distress, especially in the depression/poor mood, anxiety, and sleep/night behavior.

CONCLUSION

It is consistent with an effective result of agomelatine in improving BPSD.

Valerian essential oil for treating insomnia via the serotonergic synapse pathway

Valerian volatile oil can be used in the treatment of insomnia; however, the active components and mechanisms of action are currently unclear. Therefore, we used transcriptome sequencing and weight coefficient network pharmacology to predict the effective components and mechanism of action of valerian volatile oil in an insomnia model induced by intraperitoneal injection of para-Chlorophenylalanine (PCPA) in SD rats. Valerian essential oil was given orally for treatment and the contents of 5-hydroxytryptamine receptor 1 A (5-HT1AR), γ-aminobutyric acid (GABA), cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA) in the hippocampus of rats in each group were detected by enzyme-linked immunosorbent assay (ELISA), western blot, Polymerase Chain Reaction (PCR), and immunohistochemistry. The results showed that after treatment with valerian essential oil, insomnia rats showed significantly prolonged sleep duration and alleviated insomnia-induced tension and anxiety. Regarding the mechanism of action, we believe that caryophyllene in valerian essential oil upregulates the 5-HT1AR receptor to improve the activity or affinity of the central transmitter 5-HT, increase the release of 5-HT, couple 5-HT with a G protein coupled receptor, convert adenosine triphosphate (ATP) into cAMP (catalyzed by ADCY5), and then directly regulate the downstream pathway. Following pathway activation, we propose that the core gene protein kinase PKA activates the serotonergic synapse signal pathway to increase the expression of 5-HT and GABA, thus improving insomnia symptoms and alleviating anxiety. This study provides a theoretical basis for the application of valerian volatile oil in health food.

Sleep-Wake Neurochemistry

Behavioral states naturally alternate between wakefulness and the sleep phases rapid eye movement and nonrapid eye movement sleep. Waking and sleep states are complex processes that are elegantly orchestrated by spatially fine-tuned neurochemical changes of neurotransmitters and neuromodulators including glutamate, acetylcholine, γ-aminobutyric acid, norepinephrine, dopamine, serotonin, histamine, hypocretin, melanin concentrating hormone, adenosine, and melatonin. However, as highlighted in this brief overview, no single neurotransmitter or neuromodulator, but rather their complex interactions within organized neuronal ensembles, regulate waking and sleep states. The neurochemical pathways presented here are aimed to provide a conceptual framework for the understanding of the effects of currently used sleep medications.

Sleep and anxiety: From mechanisms to interventions

Anxiety is the most common mental health problem worldwide. Epidemiological studies show that sleep disturbances, particularly insomnia, affect ∼50% of individuals with anxiety, and that insufficient sleep can instigate or further exacerbate it. This review outlines brain mechanisms underlying sleep and anxiety, by addressing recent human functional/structural imaging studies on brain networks underlying the anxiogenic impact of sleep loss, and the beneficial effect of sleep on these brain networks. We discuss recent developments from human molecular imaging studies that highlight the role of specific brain neurotransmitter mechanisms, such as the adenosinergic receptor system, on anxiety, arousal, and sleep. This review further discusses frontline sleep interventions aimed at enhancing sleep in individuals experiencing anxiety, such as nonbenzodiazepines/antidepressants, lifestyle and sleep interventions and cognitive behavioral therapy for insomnia. Notwithstanding therapeutic success, up to ∼30% of individuals with anxiety can be nonresponsive to frontline treatments. Thus, we address novel non-invasive brain stimulation techniques that can enhance electroencephalographic slow waves, and might help alleviate sleep and anxiety symptoms. Collectively, these findings contribute to an emerging biological framework that elucidates the interrelationship between sleep and anxiety, and highlight the prospect of slow wave sleep as a potential therapeutic target for reducing anxiety.

Antiallergic drug desloratadine as a selective antagonist of 5HT2A receptor ameliorates pathology of Alzheimer's disease model mice by improving microglial dysfunction

Alzheimer's disease (AD) is a progressively neurodegenerative disease characterized by cognitive deficits and alteration of personality and behavior. As yet, there is no efficient treatment for AD. 5HT_2A receptor (5HT_2A R) is a subtype of 5HT₂ receptor belonging to the serotonin receptor family, and its antagonists have been clinically used as antipsychotics to relieve psychopathy. Here, we discovered that clinically first-line antiallergic drug desloratadine (DLT) functioned as a selective antagonist of 5HT_2A R and efficiently ameliorated pathology of APP/PS1 mice. The underlying mechanism has been intensively investigated by assay against APP/PS1 mice with selective 5HT_2A R knockdown in the brain treated by adeno-associated virus (AAV)-ePHP-si-5HT_2A R. DLT reduced amyloid plaque deposition by promoting microglial Aβ phagocytosis and degradation, and ameliorated innate immune response by polarizing microglia to an anti-inflammatory phenotype. It stimulated autophagy process and repressed neuroinflammation through 5HT_2A R/cAMP/PKA/CREB/Sirt1 pathway, and activated glucocorticoid receptor (GR) nuclear translocation to upregulate the transcriptions of phagocytic receptors TLR2 and TLR4 in response to microglial phagocytosis stimulation. Together, our work has highly supported that 5HT_2A R antagonism might be a promising therapeutic strategy for AD and highlighted the potential of DLT in the treatment of this disease.

The role of melatonin and its analogues in epilepsy

Extensive research has gone into proposing a promising link between melatonin administration and attenuation of epileptic activity, the majority of which suggest its propensity as an antiseizure with antioxidant and neuroprotective properties. In the past few years, a number of studies highlighting the association of the melatonergic ligands with epilepsy have also emerged. In this context, our review is based on discussing the recent studies and various mechanisms of action that the said category of drugs exhibit in the context of being therapeutically viable antiseizure drugs. Our search revealed several articles on the four major drugs i.e. melatonin, agomelatine, ramelteon and piromelatine along with other melatonergic agonists like tasimelteon and TIK-301. Our review is suggestive of antiseizure effects of both melatonin and its analogues; however, extensive research work is still required to study their implications in the treatment of persons with epilepsy. Further evaluation of melatonergic signaling pathways and mechanisms may prove to be helpful in the near future and might prove to be a significant advance in the field of epileptology.

Pharmacokinetic and Pharmacodynamic Aspects of Peyote and Mescaline: Clinical and Forensic Repercussions

BACKGROUND

Mescaline (3,4,5-trimethoxyphenethylamine), mainly found in the Peyote cactus (Lophophora williamsii), is one of the oldest known hallucinogenic agents that influence human and animal behavior, but its psychoactive mechanisms remain poorly understood.

OBJECTIVES

This article aims to fully review pharmacokinetics and pharmacodynamics of mescaline, focusing on the in vivo and in vitro metabolic profile of the drug and its implications for the variability of response.

METHODS

Mescaline pharmacokinetic and pharmacodynamic aspects were searched in books and in PubMed (U.S. National Library of Medicine) without a limiting period. Biological effects of other compounds found in peyote were also reviewed.

RESULTS

Although its illicit administration is less common, in comparison with cocaine and Cannabis, it has been extensively described in adolescents and young adults, and licit consumption often occurs in religious and therapeutic rituals practiced by the Native American Church. Its pharmacodynamic mechanisms of action are primarily attributed to the interaction with the serotonergic 5-HT2A-C receptors, and therefore clinical effects are similar to those elicited by other psychoactive substances, such as lysergic acid diethylamide (LSD) and psilocybin, which include euphoria, hallucinations, depersonalization and psychoses. Moreover, as a phenethylamine derivative, signs and symptoms are consistent with a sympathomimetic effect. Mescaline is mainly metabolized into trimethoxyphenylacetic acid by oxidative deamination but several minor metabolites with possible clinical and forensic repercussions have also been reported.

CONCLUSION

Most reports concerning mescaline were presented in a complete absence of exposure confirmation, since toxicological analysis is not widely available. Addiction and dependence are practically absent and it is clear that most intoxications appear to be mild and are unlikely to produce lifethreatening symptoms, which favors the contemporary interest in the therapeutic potential of the drugs of the class.

Sleep as a Therapeutic Target in the Aging Brain

Sleep is a behavioral phenomenon conserved among mammals and some invertebrates, yet the biological functions of sleep are still being elucidated. In humans, sleep time becomes shorter, more fragmented, and of poorer quality with advancing age. Epidemiologically, the development of age-related neurodegenerative diseases such as Alzheimer's and Parkinson's disease is associated with pronounced sleep disruption, whereas emerging mechanistic studies suggest that sleep disruption may be causally linked to neurodegenerative pathology, suggesting that sleep may represent a key therapeutic target in the prevention of these conditions. In this review, we discuss the physiology of sleep, the pathophysiology of neurodegenerative disease, and the current literature supporting the relationship between sleep, aging, and neurodegenerative disease.

Psychedelic medicine: The biology underlying the persisting psychedelic effects

Psychedelic substances have regained interest as therapeutic agents in the treatment of stress-related disorders. The effects seem to be of persisting nature even after a single dose. Also in lower than 'regular' recreational doses, so-called micro-doses, without the typical effects on consciousness, users report beneficial effects on cognitive processes and well-being. The exact neurobiological mechanism underlying these persisting effects is not clear. While previous research has mainly focused on the central nervous system including the immune system and the neuroendocrine system, I propose a central role for sleep and the microbiome in the effects of regular and low doses of psychedelics respectively. It will be explained why this is hypothesized and studies to test this idea proposed. It is concluded that while these studies are needed to understand the biology underlying psychedelic medicine, it is also important to approach it in a holistic way, including all the above mentioned biological processes psychedelics are known to affect, and explore the role of other substance-related factors like route of administration and form, and factors like diet and lifestyle which are part of the psychedelic experience.

Monoamines and their Derivatives on GPCRs: Potential Therapy for Alzheimer's Disease

Albeit cholinergic depletion remains the key event in Alzheimer's Disease (AD), recent information describes stronger links between monoamines (trace amines, catecholamines, histamine, serotonin, and melatonin) and AD than those known in the past century. Therefore, new drug design strategies focus efforts to translate the scope on these topics and to offer new drugs which can be applied as therapeutic tools in AD. In the present work, we reviewed the state-of-art regarding genetic, neuropathology and neurochemistry of AD involving monoamine systems. Then, we compiled the effects of monoamines found in the brain of mammals as well as the reported effects of their derivatives and some structure-activity relationships. Recent derivatives have triggered exciting effects and pharmacokinetic properties in both murine models and humans. In some cases, the mechanism of action is clear, essentially through the interaction on G-protein-coupled receptors as revised in this manuscript. Additional mechanisms are inhibition of enzymes for their biotransformation, regulation of free-radicals in the central nervous system and others for the effects on Tau phosphorylation or amyloid-beta accumulation. All these data make the monoamines and their derivatives attractive potential elements for AD therapy.

[Pharmacotherapy of Sleep-Wake Disorders]

Pharmacotherapy of Sleep-Wake Disorders Abstract. Sleep is a complex behavior, coordinated by many different brain regions and neurotransmitters. These neurochemical systems can be pharmacologically influenced to modulate wakefulness and sleep. Excessive daytime sleepiness (EDS) is often treated with dopaminergic drugs, which in mild cases range from caffeine via (ar)modafinil to amphetamine derivatives. Tricyclic antidepressants and melatonin-based drugs are also used to promote alertness, but to a lesser extent. The drugs used to promote sleep include GABA-ergic drugs such as benzodiazepines and Z-hypnotics as well as histamine H1 receptor antagonists. Exogenous melatonin or a pharmacological combination of melatonin receptor agonists and 5-HT2C receptor antagonists are also used in mild cases. Selective and dual orexin (hypocretin) receptor antagonists (DORA) as well as drugs binding to specific 5-HT receptors are currently being investigated as future sleep-promoting drugs. However, pharmacological treatment is not always the primary treatment option, insomnia is treated first-line with cognitive behavioral therapy, and continuous positive airway pressure is used to treat sleep apnea.

Sleep Physiology, Circadian Rhythms, Waking Performance and the Development of Sleep-Wake Therapeutics

Disturbances of the sleep-wake cycle are highly prevalent and diverse. The aetiology of some sleep disorders, such as circadian rhythm sleep-wake disorders, is understood at the conceptual level of the circadian and homeostatic regulation of sleep and in part at a mechanistic level. Other disorders such as insomnia are more difficult to relate to sleep regulatory mechanisms or sleep physiology. To further our understanding of sleep-wake disorders and the potential of novel therapeutics, we discuss recent findings on the neurobiology of sleep regulation and circadian rhythmicity and its relation with the subjective experience of sleep and the quality of wakefulness. Sleep continuity and to some extent REM sleep emerge as determinants of subjective sleep quality and waking performance. The effects of insufficient sleep primarily concern subjective and objective sleepiness as well as vigilant attention, whereas performance on higher cognitive functions appears to be better preserved albeit at the cost of increased effort. We discuss age-related, sex and other trait-like differences in sleep physiology and sleep need and compare the effects of existing pharmacological and non-pharmacological sleep- and wake-promoting treatments. Successful non-pharmacological approaches such as sleep restriction for insomnia and light and melatonin treatment for circadian rhythm sleep disorders target processes such as sleep homeostasis or circadian rhythmicity. Most pharmacological treatments of sleep disorders target specific signalling pathways with no well-established role in either sleep homeostasis or circadian rhythmicity. Pharmacological sleep therapeutics induce changes in sleep structure and the sleep EEG which are specific to the mechanism of action of the drug. Sleep- and wake-promoting therapeutics often induce residual effects on waking performance and sleep, respectively. The need for novel therapeutic approaches continues not at least because of the societal demand to sleep and be awake out of synchrony with the natural light-dark cycle, the high prevalence of sleep-wake disturbances in mental health disorders and in neurodegeneration. Novel approaches, which will provide a more comprehensive description of sleep and allow for large-scale sleep and circadian physiology studies in the home environment, hold promise for continued improvement of therapeutics for disturbances of sleep, circadian rhythms and waking performance.

Relationship between mirtazapine dose and incidence of adrenergic side effects: An exploratory analysis

INTRODUCTION

Mirtazapine is an antidepressant with US Food and Drug Administration approval for management of major depressive disorder. Low doses of mirtazapine are often used for management of insomnia, with higher doses expected to provide more noradrenergic effect, and thus a higher degree of activation. If so, use of higher doses at bedtime may not be advisable and may worsen certain neuropsychiatric symptoms. No studies have been performed to evaluate these outcomes.

METHODS

This study consisted of a retrospective review of data submitted to the US Food and Drug Administration's Adverse Event Reporting System from January 1, 1995, to August 1, 2015. Cases that were deemed by study authors to represent activation of the noradrenergic system, and for which other confounders could not be identified, were included in the final analysis. The frequency of each specific adverse event was evaluated based on dose and compared to recent prescribing rates to determine if likelihood of a side effect increased with higher dose.

RESULTS

The study identified 308 incidences of anxiety, agitation, delusion, hallucination, hypertension, insomnia, nightmare, or tachycardia. After controlling for frequency of prescribing at a given dose, there was a statistically significant increase in rates of tachycardia which correlated with dose. However, after correction for multiple comparisons, results were no longer significant.

DISCUSSION

This study failed to support the hypothesis that mirtazapine is more activating at higher doses and appears to support the safety of increasing dose without increasing risk of noradrenergic side effects. Prospective studies will be necessary to confirm these findings.

A case report of the efficacy and usefulness of asenapine in the treatment of a cancer patient with delirium and aphagia

OBJECTIVE

Controlling hyperactive and mixed delirium is extremely important for the continuation of cancer treatment in palliative care. In general, oral antipsychotics are the first-line drug therapy for delirium; however, oral administration is problematic in patients presenting dysphagia. In this case report, we describe an end-stage cancer patient with aphagia who developed delirium and responded to sublingual antipsychotic asenapine for treating delirium. We also discuss the effectiveness of asenapine in hyperactive delirium as well as its usefulness for treating delirium in palliative care.

METHOD

A cancer patient with delirium was treated with several oral antipsychotics commonly used to treat delirium but did not respond to any of them. The patient subsequently developed aphagia with progression of the disease. Sublingual asenapine was therefore given to treat delirium.

RESULT

Asenapine was effective in treating delirium without causing any obvious side effects.

SIGNIFICANCE OF RESULTS

In the present case, asenapine was effective in treating hyperactive delirium that did not respond to commonly used antipsychotics. Because asenapine is a sublingual tablet, it can be used in patients with dysphagia and aphagia. In addition, this drug is anticipated to diminish the burden of end-stage patients from taking oral medications. Furthermore, its management is easier compared with injections, and can therefore also be easily used in homecare patients. Based on these perspectives, asenapine may become an important option for treating delirium in palliative care.

Drugs for Insomnia beyond Benzodiazepines: Pharmacology, Clinical Applications, and Discovery

Although the GABAergic benzodiazepines (BZDs) and Z-drugs (zolpidem, zopiclone, and zaleplon) are FDA-approved for insomnia disorders with a strong evidence base, they have many side effects, including cognitive impairment, tolerance, rebound insomnia upon discontinuation, car accidents/falls, abuse, and dependence liability. Consequently, the clinical use of off-label drugs and novel drugs that do not target the GABAergic system is increasing. The purpose of this review is to analyze the neurobiological and clinical evidence of pharmacological treatments of insomnia, excluding the BZDs and Z-drugs. We analyzed the melatonergic agonist drugs, agomelatine, prolonged-release melatonin, ramelteon, and tasimelteon; the dual orexin receptor antagonist suvorexant; the modulators of the α₂δ subunit of voltage-sensitive calcium channels, gabapentin and pregabalin; the H₁ antagonist, low-dose doxepin; and the histamine and serotonin receptor antagonists, amitriptyline, mirtazapine, trazodone, olanzapine, and quetiapine. The pharmacology and mechanism of action of these treatments and the evidence-base for the use of these drugs in clinical practice is outlined along with novel pipelines. There is evidence to recommend suvorexant and low-dose doxepin for sleep maintenance insomnia; there is also sufficient evidence to recommend ramelteon for sleep onset insomnia. Although there is limited evidence for the use of the quetiapine, trazodone, mirtazapine, amitriptyline, pregabalin, gabapentin, agomelatine, and olanzapine as treatments for insomnia disorder, these drugs may improve sleep while successfully treating comorbid disorders, with a different side effect profile than the BZDs and Z-drugs. The unique mechanism of action of each drug allows for a more personalized and targeted medical management of insomnia.

Sleep-Wake Neurochemistry

The regulated alternations between wakefulness and sleep states reflect complex behavioral processes, orchestrated by distinct neurochemical changes in brain parenchyma. No single neurotransmitter or neuromodulator controls the sleep-wake states in isolation. Rather, fine-tuned interactions within organized neuronal circuits regulate waking and sleep states and drive their transitions. Structural or functional dysregulation and medications interfering with these ensembles can lead to sleep-wake disorders and exert wanted or unwanted pharmacological actions on sleep-wake states. Knowledge of the neurochemical bases of sleep-wake states, which will be discussed in this article, provides the conceptual framework for understanding pharmacological effects on sleep and wake.

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.

Novel Bivalent 5-HT2A Receptor Antagonists Exhibit High Affinity and Potency in Vitro and Efficacy in Vivo

The 5-HT_2A receptor (5-HT_2AR) plays an important role in various neuropsychiatric disorders, including substance use disorder and schizophrenia. Homodimerization of this receptor has been suggested, but tools that allow direct assessment of the relevance of the 5-HT_2AR:5-HT_2AR homodimer in these disorders are necessary. We chemically modified the selective 5-HT_2AR antagonist M100907 to synthesize a series of homobivalent ligands connected by ethylene glycol linkers of varying lengths that may be useful tools for probing 5-HT_2AR:5-HT_2AR homodimer function. We tested these molecules for 5-HT_2AR antagonist activity in a cell line stably expressing the functional 5-HT_2AR and quantified a downstream signaling target, activation (phosphorylation) of extracellular regulated kinases 1/2 (ERK_1/2), in comparison to in vivo efficacy of altering spontaneous or cocaine-evoked locomotor activity in rats. All of the synthetic compounds inhibited 5-HT-mediated phosphorylation of ERK_1/2 in the cellular signaling assay; the potency of the bivalent ligands varied as a function of linker length, with the intermediate linker lengths being the most potent. The K_i values for the binding of bivalent ligands to 5-HT_2AR were only slightly lower than the values for the parent (+)-M100907 compound, but significant selectivity for 5-HT_2AR over 5-HT_2BR or 5-HT_2CR binding was retained. In addition, the 11-atom-linked bivalent 5-HT_2AR antagonist (2 mg/kg, intraperitoneally) demonstrated efficacy on par with that of (+)-M100907 in inhibiting cocaine-evoked hyperactivity. As we develop further strategies for ligand-evoked receptor assembly and analyses of diverse signaling and functional roles, these novel homobivalent 5-HT_2AR antagonist ligands will serve as useful in vitro and in vivo probes of 5-HT_2AR structure and function.

The Association between 5HT2A T102C and Behavioral and Psychological Symptoms of Dementia in Alzheimer's Disease: A Meta-Analysis

The serotonin receptor gene (5-HT2A) has been reported to be a susceptible factor in behavioral and psychological symptoms of dementia (BPSD) in Alzheimer's disease (AD). However, previous results were conflicting. We aim to investigate the association of 5-HT2A T102C with BPSD in AD using a meta-analysis. Studies were collected using PubMed, Web of Science, the Cochrane Library databases, Chinese National Knowledge Infrastructure (CNKI), and Embase. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess associations. Nine studies with 1899 AD patients with/without BPSD were included in this meta-analysis. The 102C and CC genotypes were associated with psychosis in AD (102C: p < 0.00001, OR [95% CI] = 3.19 [2.12-4.79]; CC: p < 0.00001, OR [95% CI] = 7.24 [3.60-14.59]). The TT genotype was significantly associated with hallucinations, aberrant motor behavior, and psychosis in AD (hallucinations: p = 0.001, OR [95% CI] = 0.52 [0.36-0.77]; aberrant motor behavior: p = 0.03, OR [95% CI] = 0.58 [0.35-0.95]; and psychosis: p = 0.002, OR [95% CI] = 0.34 [0.17-0.67]). No association was observed between T102C alleles or genotypes and delusions, agitation/aggression, depression, and apathy (p > 0.05). Thus, the 5HT2A T102C might be a susceptible factor for hallucinations, aberrant motor behavior, and psychosis in AD. The potential mechanism of this polymorphism in BPSD in AD requires further exploration.

Towards a Functional Understanding of PGO Waves

Ponto-Geniculo-Occipital (PGO) waves are biphasic field potentials identified in a range of mammalian species that are ubiquitous with sleep, but can also be identified in waking perception and eye movement. Their role in REM sleep and visual perception more broadly may constitute a promising avenue for further research, however what was once an active field of study has recently fallen into stasis. With the reality that invasive recordings performed on animals cannot be replicated in humans; while animals themselves cannot convey experience to the extent required to elucidate how PGO waves factor into awareness and behavior, innovative solutions are required if significant research outcomes are to ever be realized. Advances in non-invasive imaging technologies and sophistication in imaging methods now offer substantial scope to renew the study of the electrophysiological substrates of waking and dreaming perception. Among these, Magnetoencephalogram (MEG) stands out through its capacity to measure deep brain activations with high temporal resolution. With the current trend in sleep and dream research to produce translational findings of psychopathological and medical significance, in addition to the clear links that PGO wave generation sites share, pharmacologically, with receptors involved in expression of mental illness; there is a strong case to support scientific research into PGO waves and develop a functional understanding of their broader role in human perception.

Adjunctive Brexpiprazole as a Novel Effective Strategy for Treating Major Depressive Disorder: A Systematic Review and Meta-Analysis

PURPOSE/BACKGROUND

Brexpiprazole was approved for adjunctive treatment of major depressive disorder (MDD) in 2015. Because only a small number of randomized controlled trials have investigated the use of brexpiprazole in MDD, we performed a meta-analysis.

METHODS/PROCEDURES

We systematically searched literatures in PubMed, Cochrane Library database, EMBASE, Google Scholar, and clinicaltrials.gov up to January 2016. The primary efficacy measure was the mean change in total Montgomery-Åsberg Depression Rating Scale (MADRS) score from baseline. Secondary efficacy measures were the mean change in total Hamilton Rating Scale for Depression (17 items) score from baseline and the response (≥50% reduction in MADRS total score) and remission (MADRS total score ≤ 10 with ≥50% reduction) rates.

FINDINGS/RESULTS

Four studies fulfilled the inclusion criteria and were included in the analysis. Brexpiprazole showed superior efficacy over placebo with effect sizes (mean differences) of -1.76 (95% confidence interval [CI], -2.45 to -1.07) for MADRS and -1.21 (95% CI, -1.71 to -0.72) for the 17-item Hamilton Rating Scale for Depression. The risk ratios for response and remission were 1.57 (95% CI, 1.29-1.91) and 1.55 (95% CI, 1.22-1.96), respectively. The incidences of discontinuation due to adverse events, akathisia, and weight increase were higher in the brexpiprazole group than in the placebo group, with risk ratios of 3.44 (95% CI, 1.52-7.80), 3.39 (95% CI, 2.08-5.51), and 4.36 (95% CI, 2.45-7.77), respectively, and the incidence of akathisia was related to the brexpiprazole dose.

IMPLICATIONS/CONCLUSIONS

Although our results suggest that brexpiprazole could be an effective adjunctive agent for MDD, they should be cautiously translated into clinical practice because the meta-analysis was based on only a handful of randomized controlled trials.

Inverse agonists - What do they mean for psychiatry?

The nomenclature of drugs is a critical aspect of science, since it can direct research and optimize treatment choices. Traditionally drugs acting on CNS receptors have been classified as either agonists or antagonists. Recently a new class of ligand, the inverse agonist, has been identified in some receptor systems. Inverse agonists have opposite actions to those of agonists but the effects of both of these can be blocked by antagonists. Pimavanserin is a new 5-HT2A receptor acting drug that has been given market authorization for psychosis in Parkinson׳s disease. The FDA have termed it an inverse agonist, but this conclusion is based on in-vitro data. In this paper we discuss the evidence for such a claim being made for pimavanserin in the human brain and conclude that this is not currently sufficient. It is therefore premature to conclude that the actions of pimavanserin in humans are due to inverse agonism, and we are of the opinion that it should be called a 5-HT2A antagonist until better evidence emerges.

A Review of Melatonin, Its Receptors and Drugs

After a Turkish scientist took Nobel Prize due to his contributions to understand clock genes, melatonin, closely related to these genes, may begin to shine. Melatonin, a hormone secreted from the pineal gland at night, plays roles in regulating sleep-wake cycle, pubertal development and seasonal adaptation. Melatonin has antinociceptive, antidepressant, anxiolytic, antineophobic, locomotor activity-regulating, neuroprotective, anti-inflammatory, pain-modulating, blood pressure-reducing, retinal, vascular, anti-tumor and antioxidant effects. It is related with memory, ovarian physiology, and osteoblast differentiation. Pathologies associated with an increase or decrease in melatonin levels are summarized in the review. Melatonin affects by four mechanisms: 1) Binding to melatonin receptors in plasma membrane, 2) Binding to intracellular proteins such as calmoduline, 3) Binding to Orphan nuclear receptors, and 4) Antioxidant effect. Receptors associated with melatonin are as follows: 1) Melatonin receptor type 1a: MT1 (on cell membrane), 2) Melatonin receptor type 1b: MT2 (on cell membrane), 3) Melatonin receptor type 1c (found in fish, amphibians and birds), 4) Quinone reductase 2 enzyme (MT3 receptor, a detoxification enzyme), 5) RZR/RORα: Retinoid-related Orphan nuclear hormone receptor (with this receptor, melatonin binds to the transcription factors in nucleus), and 6) GPR50: X-linked Melatonin-related Orphan receptor (it is effective in binding of melatonin to MT1). Melatonin agonists such as ramelteon, agomelatine, circadin, TIK-301 and tasimelteon are introduced and side effects will be discussed. In conclusion, melatonin and related drugs is a new and promising era for medicine. Melatonin receptors and melatonin drugs will take attention with greater interest day by day in the future.

Update on melatonin receptors: IUPHAR Review 20

Melatonin receptors are seven transmembrane-spanning proteins belonging to the GPCR superfamily. In mammals, two melatonin receptor subtypes exist - MT1 and MT2 - encoded by the MTNR1A and MTNR1B genes respectively. The current review provides an update on melatonin receptors by the corresponding subcommittee of the International Union of Basic and Clinical Pharmacology. We will highlight recent developments of melatonin receptor ligands, including radioligands, and give an update on the latest phenotyping results of melatonin receptor knockout mice. The current status and perspectives of the structure of melatonin receptor will be summarized. The physiological importance of melatonin receptor dimers and biologically important and type 2 diabetes-associated genetic variants of melatonin receptors will be discussed. The role of melatonin receptors in physiology and disease will be further exemplified by their functions in the immune system and the CNS. Finally, antioxidant and free radical scavenger properties of melatonin and its relation to melatonin receptors will be critically addressed.

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.

The serotonergic system in the neurobiology of depression: Relevance for novel antidepressants

The monoamine hypothesis of depression posits that an imbalance in monoaminergic neurotransmission is causally related to the clinical features of depression. Antidepressants influencing serotonin mainly aim at raising serotonin concentrations, thereby increasing serotonergic transmission at the level of the synapse, for example by inhibiting the serotonin transporter. However, the serotonin system is multifaceted. Different serotonin receptor subtypes turn the serotonergic system into a complex neurochemical arrangement that influences diverse neurotransmitters in various brain regions. Classical antidepressants as well as other psychopharmacological agents have various crucial effects on serotonin receptors. We aim at providing a clinically useful characterization of serotonin receptor subtypes in the treatment of depression. Clarifying the mode of action and the interplay of serotonin receptors with pharmacological agents should help antidepressant mechanisms and typical side effects to be better understood. Against this background, we feature the novel antidepressants vortioxetine, vilazodone and milnacipran/levomilnacipran with regard to their serotonin receptor targets such as the 5-HT1A, 5-HT3 and 5-HT7 which may account for their specific effects on certain symptoms of depression (e.g. cognition and anxiety) as well as a characteristic side-effect profile.

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.

mGlu2 Receptor Agonism, but Not Positive Allosteric Modulation, Elicits Rapid Tolerance towards Their Primary Efficacy on Sleep Measures in Rats

G-protein-coupled receptor (GPCR) agonists are known to induce both cellular adaptations resulting in tolerance to therapeutic effects and withdrawal symptoms upon treatment discontinuation. Glutamate neurotransmission is an integral part of sleep-wake mechanisms, which processes have translational relevance for central activity and target engagement. Here, we investigated the efficacy and tolerance potential of the metabotropic glutamate receptors (mGluR2/3) agonist LY354740 versus mGluR2 positive allosteric modulator (PAM) JNJ-42153605 on sleep-wake organisation in rats. In vitro, the selectivity and potency of JNJ-42153605 were characterized. In vivo, effects on sleep measures were investigated in rats after once daily oral repeated treatment for 7 days, withdrawal and consecutive re-administration of LY354740 (1–10 mg/kg) and JNJ-42153605 (3–30 mg/kg). JNJ-42153605 showed high affinity, potency and selectivity at mGluR2. Binding site analyses and knowledge-based docking confirmed the specificity of JNJ-42153605 at the mGluR2 allosteric binding site. Acute LY354740 and JNJ-42153605 dose-dependently decreased rapid eye movement (REM) sleep time and prolonged its onset latency. Sub chronic effects of LY354740 on REM sleep measures disappeared from day 3 onwards, whereas those of JNJ-42153605 were maintained after repeated exposure. LY354740 attenuated REM sleep homeostatic recovery, while this was preserved after JNJ-42153605 administration. JNJ-42153605 enhanced sleep continuity and efficiency, suggesting its potential as an add-on medication for impaired sleep quality during early stages of treatment. Abrupt cessation of JNJ-42153605 did not induce withdrawal phenomena and sleep disturbances, while the initial drug effect was fully reinstated after re-administration. Collectively, long-term treatment with JNJ-42153605 did not induce tolerance phenomena to its primary functional effects on sleep measures, nor adverse effects at withdrawal, while it promoted homeostatic recovery sleep. From the translational perspective, the present rodent findings suggest that mGluR2 positive allosteric modulation has therapeutic potential based on its superior long term efficacy over agonists in psychiatric disorders, particularly of those commonly occurring with REM sleep overdrive.

Synaptic plasticity model of therapeutic sleep deprivation in major depression

Therapeutic sleep deprivation (SD) is a rapid acting treatment for major depressive disorder (MDD). Within hours, SD leads to a dramatic decrease in depressive symptoms in 50-60% of patients with MDD. Scientifically, therapeutic SD presents a unique paradigm to study the neurobiology of MDD. Yet, up to now, the neurobiological basis of the antidepressant effect, which is most likely different from today's first-line treatments, is not sufficiently understood. This article puts the idea forward that sleep/wake-dependent shifts in synaptic plasticity, i.e., the neural basis of adaptive network function and behavior, represent a critical mechanism of therapeutic SD in MDD. Particularly, this article centers on two major hypotheses of MDD and sleep, the synaptic plasticity hypothesis of MDD and the synaptic homeostasis hypothesis of sleep-wake regulation, and on how they can be integrated into a novel synaptic plasticity model of therapeutic SD in MDD. As a major component, the model proposes that therapeutic SD, by homeostatically enhancing cortical synaptic strength, shifts the initially deficient inducibility of associative synaptic long-term potentiation (LTP) in patients with MDD in a more favorable window of associative plasticity. Research on the molecular effects of SD in animals and humans, including observations in the neurotrophic, adenosinergic, monoaminergic, and glutamatergic system, provides some support for the hypothesis of associative synaptic plasticity facilitation after therapeutic SD in MDD. The model proposes a novel framework for a mechanism of action of therapeutic SD that can be further tested in humans based on non-invasive indices and in animals based on direct studies of synaptic plasticity. Further determining the mechanisms of action of SD might contribute to the development of novel fast acting treatments for MDD, one of the major health problems worldwide.

Histamine H1 receptor occupancy by the new-generation antipsychotics olanzapine and quetiapine: a positron emission tomography study in healthy volunteers

RATIONALE

Histamine H1 antagonists have hypnotic, appetite-promoting, and sedative side effects. Most second-generation antipsychotics have potent antagonistic effects on histamine H1 receptor (H1R). Positron emission tomography (PET) can measure the H1R occupancy (H1RO) in vivo, although there are no reports regarding antipsychotics.

OBJECTIVES

We studied the H1RO of olanzapine and quetiapine in vivo with respect to their plasma concentrations and subjective drowsiness by performing human PET imaging studies with [(11)C]doxepin, a potent PET ligand of H1R.

METHODS

Six healthy Japanese male volunteers were enrolled. Cross-randomized PET imaging was performed after a single oral administration of olanzapine (2.5 mg), quetiapine (25 mg), or placebo. PET data were analyzed by region of interest and voxel-by-voxel analysis. We concurrently measured plasma drug concentrations by liquid chromatography/tandem mass spectrometry and evaluated subjective sleepiness.

RESULTS

The binding potential ratios of olanzapine and quetiapine in the cerebral cortex were significantly lower than that of the placebo. The H1RO values of olanzapine and quetiapine in the cortex were approximately 61-80 and 56-81%, respectively. The binding potential ratios of the drugs were significantly lower than that of the placebo in the dorsolateral prefrontal and lateral temporal cortices, and anterior and posterior cingulate gyri. The H1RO values in the cortex were significantly correlated with subjective sleepiness but not plasma drug concentrations.

CONCLUSIONS

Olanzapine and quetiapine have high H1RO values in the human brain under their clinical minimum doses. This study provides a foundation of the properties by which new-generation antipsychotics block the central histaminergic system in humans.

Agomelatine in the treatment of major depressive disorder: an assessment of benefits and risks

Agomelatine (AGM) was approved for the treatment of major depressive disorder (MDD) in adults by the European Medicines Agency (EMA) in February 2009. It is an analogue of melatonin and features a unique pharmacodynamic profile with agonism on both types of melatonergic receptors (MT1/MT2) and antagonism at serotonergic 5-HT2C receptors. There is, however, an ongoing debate regarding the efficacy and safety of this novel antidepressant agent, originally evoked by claims of a significant publication bias underlying the assessment of AGM being an effective antidepressant. Indeed, two recent comprehensive metaanalyses of published and unpublished clinical trials found evidence for a relevant publication bias. However, due to its statistically significant advantage over placebo based on the results of these metaanalyses AGM must be referred to as an effective antidepressant agent in the acute phase of MDD. However, the effect sizes of AGM in the treatment of MDD were evaluated as being small in comparison to other antidepressant agents. In addition, there is insufficient evidence for the efficacy of AGM in relapse prevention of MDD. Apart from efficacy issues, AGM appears to have the potential to exhibit severe hepatotoxicity (the EMA has identified AGM-associated “hepatotoxic reactions” as a new safety concern in September 2013) that is currently poorly understood. Considering these aspects, it seems inappropriate to evaluate AGM as an antidepressant agent of first choice. Nevertheless, its unique mechanism of action with particular sleep modulating effects may represent a specific treatment strategy for patients with particular characteristics; further studies with thorough characterization of patients are needed to test this hypothesis.

Melatonergic drugs in development

Melatonin (N-acetyl-5-methoxytryptamine) is widely known as "the darkness hormone". It is a major chronobiological regulator involved in circadian phasing and sleep-wake cycle in humans. Numerous other functions, including cyto/neuroprotection, immune modulation, and energy metabolism have been ascribed to melatonin. A variety of studies have revealed a role for melatonin and its receptors in different pathophysiological conditions. However, the suitability of melatonin as a drug is limited because of its short half-life, poor oral bioavailability, and ubiquitous action. Due to the therapeutic potential of melatonin in a wide variety of clinical conditions, the development of new agents able to interact selectively with melatonin receptors has become an area of great interest during the last decade. Therefore, the field of melatonergic receptor agonists comprises a great number of structurally different chemical entities, which range from indolic to nonindolic compounds. Melatonergic agonists are suitable for sleep disturbances, neuropsychiatric disorders related to circadian dysphasing, and metabolic diseases associated with insulin resistance. The results of preclinical studies on animal models show that melatonin receptor agonists can be considered promising agents for the treatment of central nervous system-related pathologies. An overview of recent advances in the field of investigational melatonergic drugs will be presented in this review.

Olanzapine and clozapine differently affect sleep in patients with schizophrenia: results from a double-blind, polysomnographic study and review of the literature

Schizophrenia is associated with impaired sleep continuity. The second generation antipsychotics clozapine and olanzapine have been reported to improve sleep continuity but also to rarely induce restless legs syndrome (RLS). The aims of this randomized double-blind study were to compare the effects of clozapine and olanzapine on sleep and the occurrence of RLS. Therefore, polysomnographies were recorded and RLS symptoms were assessed in 30 patients with schizophrenia before and after 2, 4 and 6 weeks of treatment with either clozapine or olanzapine. Treatment with both antipsychotics increased total sleep time, sleep period time and sleep efficiency and decreased sleep onset latency. These changes were similar in both groups, occurred during the first 2 treatment weeks and were sustained. For example, sleep efficiency increased from 83% (olanzapine) and 82% (clozapine) at baseline to 95% at week 2 and 97% at week 6 in both treatment groups. Sleep architecture was differently affected: clozapine caused a significantly stronger increase of stage 2 sleep (44%) than olanzapine (11%) but olanzapine a significantly stronger increase of REM-sleep. Olanzapine caused an 80% increase of slow wave sleep whereas clozapine caused a 6% decrease. No patient reported any of 4 RLS defining symptoms at baseline. During treatment, 1 patient of each group reported at one visit all 4 symptoms, i.e. met the diagnosis of an RLS. In conclusion, sleep continuity similarly improved and sleep architecture changed more physiologically with olanzapine. Neither of the antipsychotics induced RLS symptoms that were clinically relevant.

Histamine H₁ receptor occupancy by the new-generation antidepressants fluvoxamine and mirtazapine: a positron emission tomography study in healthy volunteers

RATIONALE

Histamine H₁ antagonists have hypnotic, appetite-promoting, and sedative effects. The affinities of various antidepressants for histamine receptors have only been partially determined in vitro and animal study. Positron emission tomography (PET) can clarify the in vivo dynamics of antidepressants at histamine receptors.

OBJECTIVES

We performed human PET imaging with [¹¹C]doxepin, a selective PET ligand of the histamine H₁ receptor (H₁R), to study the in vivo affinities of fluvoxamine and mirtazapine for the H₁R.

METHODS

The subjects were five male healthy Japanese volunteers. We performed cross-randomized PET imaging after single oral administration of fluvoxamine (25mg), mirtazapine (15 mg), or placebo. PET data were analyzed by region-of-interest and voxel-by-voxel analysis. We concurrently measured plasma drug concentrations, using liquid chromatography/tandem mass spectrometry and subjective sleepiness.

RESULTS

The binding potential ratio of mirtazapine in brain cortex was significantly lower than that of fluvoxamine or placebo. Fluvoxamine did not occupy the H₁R, whereas H₁R occupancy (H₁RO) of mirtazapine reached 80-90 % in the cerebral neocortex. In the voxel-by-voxel analysis, the binding potential of mirtazapine was significantly lower than placebo in the dorsolateral prefrontal cortex, lateral temporal cortex, anterior cingulate gyrus, and posterior cingulate gyrus. The H₁RO of mirtazapine depended on the plasma drug concentration (AUC(0-180 min)) and was related to subjective sleepiness.

CONCLUSIONS

Our results demonstrate a low affinity of fluvoxamine and a very high affinity of mirtazapine for the human brain H₁R in vivo. This study provides a basis for investigating the efficacy of new-generation antidepressants in central histamine systems.

[A combination of ramelteon and Yi-gan san successfully improved post-surgical delirium in a patient with subarachnoid hemorrhage]

A 68-year-old woman presented with a sudden severe headache, vomiting, and disturbed consciousness. She was admitted to the emergency room. Computed tomography (CT) revealed a hemorrhage in the right temporal lobe. Angiography demonstrated a ruptured aneurysm in the right middle cerebral artery (MCA) and an unruptured aneurysm in the left MCA. The subarachnoid hemorrhage was grade 3 (Hunt and Kosnik classification). Emergency craniotomy, clipping of the ruptured aneurysm and removal of the hematoma were performed. The left hemiparesis improved, and the patient was able to walk. We prescribed triazolam (0.25 mg/day) to treat the patient's insomnia. The unruptured aneurysm was additionally clipped on the 15th hospital day. After the second operation, the patient complained of delirium with restlessness, excitement, disorganized behavior, and sleep disturbance. Treatment with thiapride (150 mg/day) did not improve the delirium. We additionally administered Yi-gan san (7.5 g/day) and switched the triazolam to ramelteon (8 mg/day). The Memorial Delirium Assessment Scale score improved dramatically (from 16 at onset to 5 on day 7 and 1 at two months). Yi-gan san is reported to be effective for the treatment of behavioral and psychological symptoms of dementia. Ramelteon, a melatonin receptor agonist, is implicated in the regulation of the sleep-wake cycle. Ramelteon, unlike other hypnotic drugs, does not cause oversedation, rebound insomnia, withdrawal symptoms or dependence. In addition, we have noted no adverse effects, including oversedation or clinically significant changes in laboratory data, during combination therapy. A combination of ramelteon and Yi-gan san may therefore be beneficial in elderly patients with delirium, especially when there is a risk of oversedation.

Sleep architecture in ziprasidone-treated bipolar depression: a pilot study

OBJECTIVES

This study investigated the effect of ziprasidone augmentation therapy on sleep architecture in bipolar depression.

METHODS

We conducted a double-blind, randomized, placebo-controlled clinical pilot trial of ziprasidone versus placebo in Diagnostic and Statistical Manual of Mental Disorders, fourth edition bipolar disorder with current major depressive episode. The effects during acute (2-5 days) and continuation treatment (28-31 days) were measured. Main outcomes were sleep architecture variables including rapid eye movement sleep (REM) and slow wave sleep (SWS) measured by polysomnography. Secondary outcomes included subjective sleep quality measures and illness severity measures including the 17-item Hamilton Depression Rating Scale (HAMD-17), Montgomery Asberg Depression Rating Scale (MADRS), Hamilton Anxiety Rating Scale (HAMA) and Clinical Global Illness Severity (CGI-S) scores.

RESULTS

The completer analysis comprised of 14 patients (ziprasidone, N = 8 and placebo, N = 6). Latency to REM, duration of SWS, duration of stage 2 sleep, total sleep time, onset to sleep latency, number of awakenings and overall sleep efficiency significantly improved in ziprasidone-treated participants over placebo. CGI-S and HAMA scores also significantly improved. No significant difference between treatment groups was seen on the HAMD-17, MADRS or in self-reported sleep quality. Increase in SWS duration significantly correlated with improvement in CGI-S, however, this finding did not withstand Bonferroni correction.

CONCLUSION

Adjunctive ziprasidone treatment alters sleep architecture in patients with bipolar depression, which may partially explain its mechanism of action and merits further investigation.

Assessment of adverse effects of neurotropic drugs in monkeys with the "drug effects on the nervous system" (DENS) scale

Research into therapeutics for neuropsychiatric disorders is increasingly focusing on drugs with new mechanisms of action, and such agents are often assessed in preclinical studies using nonhuman primates. However, researchers lack a standardised method to compare different drugs for common adverse effects on the nervous system. We have developed a new scale for this purpose, named "Drug Effects on the Nervous System" (DENS), and tested its utility in an analysis of the second-generation antipsychotic risperidone in monkeys. The behavioural effects of risperidone over a ten-fold clinically relevant exposure range were rated with the DENS scale and compared with a standard motor disability scale for primates. The ratings were correlated with projected D2 and 5-HT2A receptor occupancies over time. The DENS scale detected dose-dependent side effects of risperidone in addition to the motor effects detected with the motor disability scale, including cognitive, sensorimotor and autonomic functions. A consistent temporal association between the DENS scale changes and the projected D2 receptor occupancy was observed, and the DENS scale ratings demonstrated high inter-rater reliability. These results demonstrate the usefulness of the DENS scale as a highly sensitive, reliable and accurate method to identify common adverse effects of risperidone and potentially other neurotropics for translational studies in primates.