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

DSP-6745, a novel 5-hydroxytryptamine modulator with rapid antidepressant, anxiolytic, antipsychotic and procognitive effects

BACKGROUND

Current treatment of major depressive disorder is facing challenges, including a low remission rate, late onset of efficacy, and worsening severity due to comorbid symptoms such as psychosis and cognitive dysfunction. Serotonin (5-HT) neurotransmission is involved in a wide variety of psychiatric diseases and its potential as a drug target continues to attract attention.

OBJECTIVES

The present study elucidates the effects of a novel 5-HT modulator, DSP-6745, on depression and its comorbid symptoms.

RESULTS

In vitro radioligand binding and functional assays showed that DSP-6745 is a potent inhibitor of 5-HT transporter and 5-HT2A, 5-HT2C, and 5-HT7 receptors. In vivo, DSP-6745 (6.4 and 19.1 mg/kg as free base, p.o.) increased the release of not only 5-HT, norepinephrine, and dopamine, but also glutamate in the medial prefrontal cortex. The results of in vivo mouse phenotypic screening by SmartCube® suggested that DSP-6745 has a behavioral signature combined with antidepressant-, anxiolytic-, and antipsychotic-like signals. A single oral dose of DSP-6745 (6.4 and 19.1 mg/kg) showed rapid antidepressant-like efficacy in the rat forced swim test, even at 24 h post-dosing, and anxiolytic activity in the rat social interaction test. Moreover, DSP-6745 (12.7 mg/kg, p.o.) led to an improvement in the apomorphine-induced prepulse inhibition deficit in rats. In the marmoset object retrieval with detour task, which is used to assess cognitive functions such as attention and behavioral inhibition, DSP-6745 (7.8 mg/kg, p.o.) enhanced cognition.

CONCLUSIONS

These data suggest that DSP-6745 is a multimodal 5-HT receptor antagonist and a 5-HT transporter inhibitor and has the potential to be a rapid acting antidepressant with efficacies in mitigating the comorbid symptoms of depression.

Design, synthesis, and biological evaluation of aralkyl piperazine and piperidine derivatives targeting SSRI/5-HT1A/5-HT7

Serotonin reuptake inhibition combined with the action targeting 5-hydroxytryptamine receptor subtypes can serve as a potential target for the development of antidepressant drugs. Herein a series of new aralkyl piperazines and piperidines were designed and synthesized by the structural modifications of the previously discovered aralkyl piperidine compound 1, targeting SSRI/5-HT1A/5-HT7. The results exhibited that compound 5a showed strong binding to 5-HT1A and 5-HT7 (Ki of 0.46 nM, 2.7 nM, respectively) and a high level of serotonin reuptake inhibition (IC50 of 1.9 nM), all of which were significantly elevated compared to 1. In particular, compound 5a showed weaker inhibitory activity against hERG than 1, and demonstrated good stability in liver microsomes in vitro. The preliminary screening using FST indicated that orally administered 5a, at a high dose, could reduce immobility time in mice markedly, indicating potential antidepressant activity.

Successful Challenge With Brexpiprazole for Idiopathic Hypersomnia in a Patient With Bipolar Disorder: A Case Report

We describe a 32-year-old Japanese female with hypersomnia and bipolar disorder. She had developed hypersomnia and sleep attacks in her teens. She was misdiagnosed with narcolepsy at a neurology department and then received methylphenidate (MPH) for many years. After giving birth, she developed postpartum depression and suffered from mood swings and irritability. Following 10-year treatment with methylphenidate, she experienced MPH-induced psychosis when she was in a manic state. Her psychosis improved rapidly with the cessation of methylphenidate. Furthermore, brexpiprazole treatment ameliorated her manic symptoms and hypersomnolence. Post-discharge, she was diagnosed with idiopathic hypersomnia based on nocturnal polysomnography and a multiple sleep latency test. This case indicates that brexpiprazole as a serotonin dopamine activity modulator might provide therapeutic effects against not only the patient's manic symptoms but also idiopathic hypersomnia.

The 5-HT7 receptor system as a treatment target for mood and anxiety disorders: A systematic review

BACKGROUND

Preclinical animal and preliminary human studies indicate that 5-HT7 antagonists have the potential as a new treatment approach for mood and anxiety disorders. In this systematic review, we aimed to review the relationship between the 5-HT7 receptor system and mood and anxiety disorders, and to explore the pharmacology and therapeutic potential of medications that target the 5-HT7 receptor for their treatment.

METHODS

Medline, Cochrane Library, EMBASE, PsycINFO databases, the National Institute of Health website Clinicaltrials.gov, controlled-trials.com, and relevant grey literature were used to search for original research articles, and reference lists of included articles were then hand searched.

RESULTS

Sixty-four studies were included in the review: 52 animal studies and 12 human studies. Studies used a variety of preclinical paradigms and questionnaires to assess change in mood, and few studies examined sleep or cognition. Forty-four out of 47 (44/47) preclinical 5-HT7 modulation studies identified potential antidepressant effects and 20/23 studies identified potential anxiolytic effects. In clinical studies, 5/7 identified potential antidepressant effects in major depressive disorder, 1/2 identified potential anxiolytic effects in generalized anxiety disorder, and 3/3 identified potential antidepressant effects in bipolar disorders.

CONCLUSION

While there is some evidence that the 5-HT7 receptor system may be a potential target for treating mood and anxiety disorders, many agents included in the review also bind to other receptors. Further research is needed using drugs that bind specifically to 5-HT7 receptors to examine treatment proof of concept further.

Functional Dimerization of Serotonin Receptors: Role in Health and Depressive Disorders

Understanding the neurobiological underpinnings of depressive disorder constitutes a pressing challenge in the fields of psychiatry and neurobiology. Depression represents one of the most prevalent forms of mental and behavioral disorders globally. Alterations in dimerization capacity can influence the functional characteristics of serotonin receptors and may constitute a contributing factor to the onset of depressive disorders. The objective of this review is to consolidate the current understanding of interactions within the 5-HT receptor family and between 5-HT receptors and members of other receptor families. Furthermore, it aims to elucidate the role of such complexes in depressive disorders and delineate the mechanisms through which antidepressants exert their effects.

SSRIs in the Treatment of Depression: A Pharmacological CUL-DE-SAC?

The widespread adoption of selective serotonin reuptake inhibitors (SSRIs) as first-line pharmacological treatments in the management of clinical depression transformed the landscape of drug therapy for this condition. SSRIs are safer and better tolerated than the tricyclic antidepressants (TCAs) that they replaced. However, they have limitations that may have placed a ceiling on the expectations of first-line pharmacological treatment. Notable problems with SSRIs include induction of anxiety on treatment initiation, delayed onset of significant therapeutic effect, sexual dysfunction, sleep disturbance and overall modest efficacy. The latter is linked with an inability of SSRIs to effectively treat syndromes of anhedonia and cognitive impairment. Combined serotonin and noradrenaline reuptake inhibitors (SNRIs), such as venlafaxine, have produced some limited improvements over SSRIs in efficacy, at the cost of a greater side-effect burden. Attempts to supplement serotonin reuptake activity with actions at serotonin receptor sub-types have not yet yielded substantial benefits; however, vortioxetine may provide more utility in the management of cognitive impairment. Future advances might come from the development of SNRIs, which more closely mimic the actions of effective TCAs. There may also be possible benefits to be derived from combining SSRIs with 5-HT4 receptor agonists and 5-HT7 receptor antagonists.

Latest updates on the serotonergic system in depression and anxiety

Psychiatric disorders are among the leading causes of global health burden, with depression and anxiety being the most disabling subtypes. The two common disorders, depression and anxiety, usually coexist and are pathologically polygenic with complicated etiologies. Current drug-based therapies include selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, and 5-hydroxytryptamine partial agonists. However, these modalities share common limitations, such as slow onset and low efficacy, which is why potential mechanistic insights for new drug targets are needed. In this review, we summarize recent advances in brain localization, pathology, and therapeutic mechanisms of the serotonergic system in depression and anxiety.

The Implication of 5-HT Receptor Family Members in Aggression, Depression and Suicide: Similarity and Difference

Being different multifactorial forms of psychopathology, aggression, depression and suicidal behavior, which is considered to be violent aggression directed against the self, have principal neurobiological links: preclinical and clinical evidence associates depression, aggression and suicidal behavior with dysregulation in central serotonergic (5-HT) neurotransmission. The implication of different types of 5-HT receptors in the genetic and epigenetic mechanisms of aggression, depression and suicidality has been well recognized. In this review, we consider and compare the orchestra of 5-HT receptors involved in these severe psychopathologies. Specifically, it concentrates on the role of 5-HT_1A, 5-HT_1B, 5-HT_2A, 5-HT_2B, 5-HT_2C, 5-HT₃ and 5-HT₇ receptors in the mechanisms underlying the predisposition to aggression, depression and suicidal behavior. The review provides converging lines of evidence that: (1) depression-related 5-HT receptors include those receptors with pro-depressive properties (5-HT_2A, 5-HT₃ and 5-HT₇) as well as those providing an antidepressant effect (5-HT_1A, 5-HT_1B, 5-HT_2C subtypes). (2) Aggression-related 5-HT receptors are identical to depression-related 5-HT receptors with the exception of 5-HT₇ receptors. Activation of 5-HT_1A, 5-HT_1B, 5-HT_2A, 5-HT_2C receptors attenuate aggressiveness, whereas agonists of 5-HT₃ intensify aggressive behavior.

Serotonin Receptors as Therapeutic Targets for Autism Spectrum Disorder Treatment

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by repetitive and stereotyped behaviors as well as difficulties with social interaction and communication. According to reports for prevalence rates of ASD, approximately 1~2% of children worldwide have been diagnosed with ASD. Although there are a couple of FDA (Food and Drug Administration)—approved drugs for ASD treatment such as aripiprazole and risperidone, they are efficient for alleviating aggression, hyperactivity, and self-injury but not the core symptoms. Serotonin (5-hydroxytryptamine, 5-HT) as a neurotransmitter plays a crucial role in the early neurodevelopmental stage. In particular, 5-HT has been known to regulate a variety of neurobiological processes including neurite outgrowth, dendritic spine morphology, shaping neuronal circuits, synaptic transmission, and synaptic plasticity. Given the roles of serotonergic systems, the 5-HT receptors (5-HTRs) become emerging as potential therapeutic targets in the ASD. In this review, we will focus on the recent development of small molecule modulators of 5-HTRs as therapeutic targets for the ASD treatment.

Serotonin 5-HT7 receptor overexpression in the raphe nuclei area produces antidepressive effect and affects brain serotonin system in male mice

Heterodimerization between 5-HT₇ and 5-HT_1A receptors seems to play an important role in the mechanism of depression and antidepressant drug action. It was suggested that the shift of the ratio between 5-HT_1A /5-HT₇ hetero- and 5-HT_1A /5-HT_1A homodimers in presynaptic neurons toward 5-HT_1A /5-HT_1A homodimers is one of the reasons of depression. Consequently, the artificial elevation of 5-HT₇ receptor number in presynaptic terminals might restore physiological homo-/heterodimer ratio resulting in antidepressive effect. Here we showed that adeno-associated virus (AAV)-based 5-HT₇ receptor overexpression in the midbrain raphe nuclei area produced antidepressive effect in male mice of both C57Bl/6J and genetically predisposed to depressive-like behavior ASC (antidepressant sensitive cataleptics) strains. These changes were accompanied by the elevation of 5-HT₇ receptor mRNA level in the frontal cortex of C57Bl/6J and its reduction in the hippocampus of ASC mice. The presence of engineered 5-HT₇ receptor in the midbrain of both mouse strains was further demonstrated. Importantly that 5-HT₇ receptor overexpression resulted in the reduction of 5-HT_1A receptor level in the membrane protein fraction from the midbrain samples of C57Bl/6J, but not ASC, mice. 5-HT₇ receptor overexpression caused an increase of 5-HIAA/5-HT ratio in the midbrain and the frontal cortex of C57Bl/6J and in all investigated brain structures of ASC mice. Thus, 5-HT₇ receptor overexpression in the raphe nuclei area affects brain 5-HT system and causes antidepressive effect both in C57Bl/6J and in "depressive" ASC male mice. Obtained results indicate the involvement of 5-HT₇ receptor in the mechanisms underlying depressive behavior.

A Randomized, Double-blind, Placebo-controlled Proof-of-Concept Trial to Evaluate the Efficacy and Safety of Non-racemic Amisulpride (SEP-4199) for the Treatment of Bipolar I Depression

BACKGROUND

Non-racemic amisulpride (SEP-4199) is an 85:15 ratio of aramisulpride:esamisulpride with a 5-HT7 and D2 receptor binding profile optimized for the treatment of bipolar depression. The aim of this study was to evaluate the efficacy and safety of SEP-4199 for the treatment of bipolar depression.

METHODS

Patients meeting DSM-5 criteria for bipolar I depression were randomized to 6 weeks of double-blind, placebo-controlled treatment with SEP-4199 200 mg/d or 400 mg/d. The primary endpoint was change in the Montgomery-Asberg Depression Rating Scale (MADRS) at Week 6. The primary efficacy analysis population consisted of patients in Europe and US (n = 289); the secondary efficacy analysis population (ITT; n = 337) included patients in Japan.

RESULTS

Endpoint improvement in MADRS total score was observed on both the primary analysis for SEP-4199 200 mg/d (P = 0.054; effect size [ES], 0.31) and 400 mg/d (P = 0.054; ES, 0.29), and on the secondary (full ITT) analysis for SEP-4199 200 mg/d (P = 0.016; ES, 0.34) and 400 mg/d (P = 0.024; ES, 0.31). Study completion rates were 81% on SEP-4199 200 mg/d, 88% on 400 mg/d, and 86% on placebo. SEP-4199 had low rates of individual adverse events (<8%) and minimal effects on weight and lipids; median increases in prolactin were +83.6 μg/L on 200 mg/d, +95.2 μg/L on 400 mg/d compared with 0.0 μg/L on placebo.

LIMITATIONS

The study excluded patients with bipolar II depression and serious psychiatric or medical comorbidity.

CONCLUSION

Study results provide preliminary proof of concept, needing confirmation in subsequent randomized trials, for the efficacy of non-racemic amisulpride in bipolar depression.

Vortioxetine as an analgesic in preclinical inflammatory pain models: Mechanism of action

Vortioxetine is a novel atypical antidepressant with multimodal activity that has recently demonstrated efficacy against neuropathic pain. There is no published data about its analgesic properties in models characterized by peripheral inflammation and consequent pain pathway sensitization, nor data on its mechanism of antinociceptive action. This study aimed to investigate vortioxetine's antinociceptive/antihyperalgesic effects in trigeminal, visceral, and somatic inflammatory pain models, and provide evidence on its mechanism of action in the modulation of trigeminal nociception. Vortioxetine's effects on the nociceptive behavior in orofacial formalin test (OFT) and acetic acid-writhing test in mice and on mechanical hyperalgesia in carrageenan-induced paw inflammation in rats were examined following peroral single administration. The involvement of serotonergic/adrenergic/cholinergic/cannabinoid/adenosine receptors was evaluated in OFT by intraperitoneally treating mice with an appropriate antagonist immediately after vortioxetine application. We used antagonists of 5-HT_1B/1D serotonergic (GR 127935), α₁ -adrenergic (prazosin), α₂ -adrenergic (yohimbine), β₁ -adrenergic (metoprolol), muscarinic (atropine), α₇ nicotinic (methyllycaconitine), CB₁ /CB₂ cannabinoid (AM251 and AM630), and adenosine A₁ (DPCPX) receptors. Vortioxetine dose-dependently reduced pain behavior in OFT and acetic acid writhing test, as well as inflammatory hyperalgesia in paw pressure test. All examined antagonists except prazosin dose-dependently inhibited vortioxetine's antinociceptive effects. In conclusion, vortioxetine exerted analgesic efficacy in trigeminal, visceral, and somatic inflammatory pain. The effect is at least in part mediated by 5-HT_1B/1D serotonergic, α₂ /β₁ -adrenergic, muscarinic and nicotinic cholinergic, CB₁ /CB₂ cannabinoid, and adenosine A₁ receptors. These findings contribute to better understanding of the analgesic effect of vortioxetine and suggest its potential usefulness for inflammatory pain treatment.

5-HT Receptors and the Development of New Antidepressants

Serotonin modulates several physiological and cognitive pathways throughout the human body that affect emotions, memory, sleep, and thermal regulation. The complex nature of the serotonergic system and interactions with other neurochemical systems indicate that the development of depression may be mediated by various pathomechanisms, the common denominator of which is undoubtedly the disturbed transmission in central 5-HT synapses. Therefore, the deliberate pharmacological modulation of serotonergic transmission in the brain seems to be one of the most appropriate strategies for the search for new antidepressants. As discussed in this review, the serotonergic system offers great potential for the development of new antidepressant therapies based on the combination of SERT inhibition with different pharmacological activity towards the 5-HT system. The aim of this article is to summarize the search for new antidepressants in recent years, focusing primarily on the possibility of benefiting from interactions with various 5-HT receptors in the pharmacotherapy of depression.

Chemical update on the potential for serotonin 5-HT6 and 5-HT7 receptor agents in the treatment of Alzheimer's disease

Despite the better understanding of the mechanisms underlying Alzheimer's Disease (AD) and launched clinical trials, no AD-modifying treatment based on a synthetic drug has been introduced for almost twenty years. The serotonin 5-HT₆ and 5-HT₇ receptors turned out to be promising biological targets for modulation of central nervous system dysfunctions including cognitive impairment. Within this paper, we evaluate the pharmacological potency of both, 5-HT₆R and 5-HT₇R, agents in search for novel AD treatment. An overview of chemical structures of the 5-HTRs ligands with simultaneous procognitive action which have undergone preclinical and clinical studies within the last 10 years has been performed.

Discovery of Nonracemic Amisulpride to Maximize Benefit/Risk of 5-HT7 and D2 Receptor Antagonism for the Treatment of Mood Disorders

In contrast to the dose‐occupancy relationship in the treatment of schizophrenia, the minimal effective level of dopamine receptor 2 (D2R) blockade for antipsychotics in the treatment of bipolar depression is unknown. Lower doses aimed at reducing extrapyramidal side effects must be balanced against the need to retain the therapeutic benefit of D2R blockade on emergent cycling, mixed, manic, anxiety, and/or psychotic symptoms. Dose‐reductions intended to lower D2R blockade, however, could also decrease concomitant serotonin receptor antagonism and its potential benefit on depressive symptoms. Here, we uncoupled the potential antidepressant activity in amisulpride, driven by 5‐HT7 receptor (5‐HT7R) antagonism, from the D2R‐mediated antipsychotic activity by discovering that each enantiomer favors a different receptor. Aramisulpride was more potent at 5‐HT7R relative to esamisulpride (Ki 47 vs. 1,900 nM, respectively), whereas esamisulpride was more potent at D2R (4.0 vs. 140 nM). We hypothesized that a nonracemic ratio might achieve greater 5‐HT7R‐mediated antidepressant effects at a lower level of D2R blockade. The dose‐occupancy relationship of esamisulpride at D2R was determined by positron emission tomography (PET) imaging in human volunteers. Separately the dose‐relationship of aramisulpride was established in humans using suppression of rapid eye movement (REM) sleep as a marker of 5‐HT7R antagonism. These results led to the discovery of an 85:15 ratio of aramisulpride to esamisulpride (SEP‐4199) that maximizes the potential for antidepressant benefit of aramisulpride via 5‐HT7R and reduces esamisulpride to minimize D2R‐related extrapyramidal side effects while still retaining D2R‐mediated effects predicted to provide benefit in bipolar depression. The antidepressant efficacy of SEP‐4199 was recently confirmed in a proof‐of‐concept trial for the treatment of bipolar depression (NCT03543410).

Leite L, da S. Tavares-Henriques M, Lopes LAF, Oliveira LGR, Silva-Filho SE, da Silveira APS, Cuman RKN, de S. Silva-Comar FM, Comar JF, do A. Brasileiro L, dos Santos JN, de Freitas WR, Leão KV, da Silva JG, Klein RC, Klein MHF, da S. Ramos BH, Fernandes CKC, de L. Ribas DG, Oesterreich SA. Modulation of the Serotonergic Receptosome in the Treatment of Anxiety and Depression: A Narrative Review of the Experimental Evidence

Serotonin (5-HT) receptors are found throughout central and peripheral nervous systems, mainly in brain regions involved in the neurobiology of anxiety and depression. 5-HT receptors are currently promising targets for discovering new drugs for treating disorders ranging from migraine to neuropsychiatric upsets, such as anxiety and depression. It is well described in the current literature that the brain expresses seven types of 5-HT receptors comprising eighteen distinct subtypes. In this article, we comprehensively reviewed 5-HT1-7 receptors. Of the eighteen 5-HT receptors known today, thirteen are G protein-coupled receptors (GPCRs) and represent targets for approximately 40% of drugs used in humans. Signaling pathways related to these receptors play a crucial role in neurodevelopment and can be modulated to develop effective therapies to treat anxiety and depression. This review presents the experimental evidence of the modulation of the “serotonergic receptosome” in the treatment of anxiety and depression, as well as demonstrating state-of-the-art research related to phytochemicals and these disorders. In addition, detailed aspects of the pharmacological mechanism of action of all currently known 5-HT receptor families were reviewed. From this review, it will be possible to direct the rational design of drugs towards new therapies that involve signaling via 5-HT receptors.

Effects of Subchronic Administrations of Vortioxetine, Lurasidone, and Escitalopram on Thalamocortical Glutamatergic Transmission Associated with Serotonin 5-HT7 Receptor

The functional suppression of serotonin (5-HT) type 7 receptor (5-HT7R) is forming a basis for scientific discussion in psychopharmacology due to its rapid-acting antidepressant-like action. A novel mood-stabilizing atypical antipsychotic agent, lurasidone, exhibits a unique receptor-binding profile, including a high affinity for 5-HT7R antagonism. A member of a novel class of antidepressants, vortioxetine, which is a serotonin partial agonist reuptake inhibitor (SPARI), also exhibits a higher affinity for serotonin transporter, serotonin receptors type 1A (5-HT1AR) and type 3 (5-HT3R), and 5-HT7R. However, the effects of chronic administration of lurasidone, vortioxetine, and the selective serotonin reuptake inhibitor (SSRI), escitalopram, on 5-HT7R function remained to be clarified. Thus, to explore the mechanisms underlying the clinical effects of vortioxetine, escitalopram, and lurasidone, the present study determined the effects of these agents on thalamocortical glutamatergic transmission, which contributes to emotional/mood perception, using multiprobe microdialysis and 5-HT7R expression using capillary immunoblotting. Acute local administration of a 5-HT7R agonist and antagonist into the mediodorsal thalamic nucleus (MDTN) enhanced and reduced thalamocortical glutamatergic transmission, induced by N-methyl-D-aspartate (NMDA)/glutamate receptor inhibition in the reticular thalamic nucleus (RTN). Acute local administration of a relevant therapeutic concentration of vortioxetine and lurasidone into the MDTN suppressed the thalamocortical glutamatergic transmission via 5-HT7R inhibition, whereas that of escitalopram activated 5-HT7R. Subchronic administration of effective doses of vortioxetine and lurasidone (for 7 days) reduced the thalamocortical glutamatergic transmission, but escitalopram did not affect it, whereas subchronic administration of these three agents attenuated the stimulatory effects of the 5-HT7R agonist on thalamocortical glutamatergic transmission. Subchronic administration of effective doses of vortioxetine, lurasidone, and escitalopram downregulated the 5-HT7R expression of the plasma membrane in the MDTN; the 5-HT7R downregulation induced by vortioxetine and lurasidone was observed at 3 days, but that induced by escitalopram required a longer duration of 7 days. These results indicate that chronic administration of vortioxetine, escitalopram, and lurasidone generate downregulation of 5-HT7R in the thalamus; however, the direct inhibition of 5-HT7R associated with vortioxetine and lurasidone generates more rapid downregulation than the indirect elevation of the extracellular serotonin level via serotonin transporter inhibition by escitalopram.

Discovery and SAR studies of 2-alkyl-3-phenyl-2,4,5,6,7,8-hexahydropyrazolo[3,4-d]azepines as 5-HT7/2 inhibitors leading to the identification of a clinical candidate

We report here the synthesis and characterization of a dual 5-HT₇ / 5-HT₂ receptor antagonist 3-(4-Fluoro-phenyl)-2-isopropyl-2,4,5,6,7,8-hexahydro-1,2,6-triaza-azulene (4j). 4j is a high affinity 5-HT₇ and 5-HT_2A receptor ligand having a pK_i = 8.1 at both receptors. It behaves as an antagonist in an in vitro functional assay for 5-HT_2A and as an inverse agonist in an in vitro functional assay for 5-HT₇. In a validated in vivo model for central 5-HT₇ activity in rats, blockade of 5-carboxamidotryptamine (5-CT) induced hypothermia, 4j shows efficacy at low doses (ED₅₀ = 0.05 mg/kg, p.o., 1 h) and maximal efficacy was observed at 0.3 mg/kg p.o. with a corresponding plasma concentration of ~27 ng/ml. In a validated in vivo model for central 5-HT_2A activity, blockade of 2,5-dimethoxy-4-iodoamphetamine (DOI) induced head-twitches in mice, 4j shows efficacy at low doses with an ED₅₀ = 0.3 mg/kg p.o. Ex vivo receptor binding studies demonstrate that 4j occupied 5-HT_2A receptor binding sites in the frontal cortex of the rat brain with an ED₅₀ in good agreement with the ED₅₀ value for central functional effect mediated by 5-HT_2A receptor (ED₅₀ = 0.8 mg/kg, p.o., 1 h).

Current Limitations and Candidate Potential of 5-HT7 Receptor Antagonism in Psychiatric Pharmacotherapy

Several mood-stabilizing atypical antipsychotics and antidepressants weakly block serotonin (5-HT) receptor type-7 (5-HT7R); however, the contributions of 5-HT7R antagonism to clinical efficacy and pathophysiology are yet to be clarified. A novel mood-stabilizing antipsychotic agent, lurasidone exhibits predominant binding affinity to 5-HT7R when compared with other monoamine receptors. To date, we have failed to discover the superior clinical efficacy of lurasidone on schizophrenia, mood, or anxiety disorders when compared with conventional mood-stabilizing atypical antipsychotics; however, numerous preclinical findings have indicated the possible potential of 5-HT7R antagonism against several neuropsychiatric disorders, as well as the generation of novel therapeutic options that could not be expected with conventional atypical antipsychotics. Traditional experimental techniques, electrophysiology, and microdialysis have demonstrated that the effects of 5-HT receptor type-1A (5-HT1AR) and 5-HT7R on neurotransmission are in contrast, but the effect of 5-HT1AR is more predominant than that of 5-HT7R, resulting in an insufficient understanding of the 5-HT7R function in the field of psychopharmacology. Accumulating knowledge regarding the pharmacodynamic profiles of 5-HT7R suggests that 5-HT7R is one of the key players in the establishment and remodeling of neural development and cytoarchitecture during the early developmental stage to the mature brain, and dysfunction or modulation of 5-HT7R is linked to the pathogenesis/pathophysiology of neuropsychiatric and neurodevelopmental disorders. In this review, to explore candidate novel applications for the treatment of several neuropsychiatric disorders, including mood disorders, schizophrenia, and other cognitive disturbance disorders, we discuss perspectives of psychopharmacology regarding the effects of 5-HT7R antagonism on transmission and intracellular signaling systems, based on preclinical findings.

Vortioxetine as a new frontier in the treatment of chronic neuropathic pain: a review and update

Chronic neuropathic pain (CNP) is a disabling medical condition that impairs the health-related quality-of-life of affected patients. A high prevalence of anxiety, depression, sleep disturbance and cognitive impairment has frequently been reported in association with CNP, making the management of this disease complex and often multidisciplinary. Dual-acting agents such as selective serotonin and noradrenalin reuptake inhibitors (SNRIs) are considered particularly useful in the modulation of pain and in treatment of the mood disorders frequently associated with CNP. Recent evidence suggests that the top-down inhibitory control of pain involves the engagement and enhancement of descending endogenous opioidergic, cannabinoid and serotonergic systems, with the effect of serotonin being particularly related to the receptor subtypes that are preferentially activated; indeed serotonin induces analgesia via activation of 5-HT7 receptors and hyperalgesia via activation of 5-HT3 receptors. Vortioxetine (VO) is a novel multimodal serotonergic antidepressant with a unique mechanism of action. It has been demonstrated recently in experimental and clinical studies to have efficacy on pain hypersensitivity and on mood disorders. This drug inhibits the serotonin transporter with a high affinity, antagonises the 5-HT3, 5-HT1D and 5HT7 serotonin receptors, and activates the 5-HT1A and 5-HT1B receptors. In clinical studies, VO has proved effective at a dose of 10-20 mg/daily in short- and long-term treatment of patients with chronic orofacial pain, demonstrating a higher rate of clinical response and remission, a better acceptability, safety rate and tolerability, and a lower latency of action compared with other antidepressants. In the light of these recent findings, VO may be considered as a new pharmacological treatment also in relation to various types of CNP, particularly in elderly patients with concomitant mood disorders and cognitive impairment. The purpose of this review is to provide an up-to-date overview of the pharmacology and clinical applications of VO and to highlight its potential therapeutic properties and advantages in the management of CNP.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

The relationship between stereochemical and both, pharmacological and ADME-Tox, properties of the potent hydantoin 5-HT7R antagonist MF-8

This study concerns synthesis and evaluation of pharmacodynamic and pharmacokinetic profile for all four stereoisomers of MF-8 (5-(4-fluorophenyl)-3-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)-5-methylimidazolidine-2,4-dione), the previously described, highly potent 5-HT₇R ligand with antidepressant activity on mice. The combination of DFT calculations of ¹H NMR chemical shifts with docking and dynamic simulations, in comparison to experimental screening results, provided prediction of the configuration for one of two present stereogenic centers. The experimental data for stereoisomers (MF-8A-MF-8D) confirmed the significant impact of stereochemistry on both, 5-HT₇R affinity and antagonistic action, with K_i and K_b values in the range of 3-366 nM and 0.024-99 μM, respectively. We also indicated the stereochemistry-dependent influence of the tested compounds on P-glycoprotein efflux, absorption in Caco-2 model, metabolic pathway as well as CYP3A4 and CYP2C9 activities.

Amelioration of Tau pathology and memory deficits by targeting 5-HT7 receptor

Tauopathies comprise a heterogeneous family of neurodegenerative diseases characterized by pathological accumulation of hyperphosphorylated Tau protein. Pathological changes in serotonergic signaling have been associated with tauopathy etiology, but the underlying mechanisms remain poorly understood. Here, we studied the role of the serotonin receptor 7 (5-HT7R), in a mouse model of tauopathy induced by overexpressing the human Tau[R406W] mutant associated with inherited forms of frontotemporal dementia. We showed that the constitutive 5-HT7R activity is required for Tau hyperphosphorylation and formation of highly bundled Tau structures (HBTS) through G-protein-independent, CDK5-dependent mechanism. We also showed that 5-HT7R physically interacts with CDK5. At the systemic level, 5-HT7R-mediated CDK5 activation induces HBTS leading to neuronal death, reduced long-term potentiation (LTP), and impaired memory in mice. Specific blockade of constitutive 5-HT7R activity in neurons that overexpressed Tau[R406W] prevents Tau hyperphosphorylation, aggregation, and neurotoxicity. Moreover, 5-HT7R knockdown in the prefrontal cortex fully abrogates Tau[R406W]-induced LTP deficits and memory impairments. Thus, 5-HT7R/CDK5 signaling emerged as a new, promising target for tauopathy treatments.

Antidepressant-like activity and safety profile evaluation of 1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione derivatives as 5-HT1A receptor partial agonists

Current antidepressant therapy has several disadvantages related to the properties of antidepressants. Considering their unfavourable features, the process of searching for new antidepressant drugs with better safety and tolerability requires consistent efforts and many complementary studies. Serotonin 5-HT_1A receptor is considered as an interesting target of antidepressant therapy. In the present study, the intrinsic activity at different signaling pathways coupled to serotonin 5-HT_1A receptor, antidepressant-like and pharmacokinetic properties, and the safety profile of two novel imidazopurine-2,4-dione derivatives, namely compounds AZ-853 (8-(4-(4-(2-fluorophenyl)piperazin-1-yl)butyl)-1,3-dimethyl-1H- imidazo[2,1-f]purine-2,4(3H,8H)-dione) and AZ-861 (1,3-dimethyl-8-(4-(4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)butyl)-1H-imidazo[2,1-f]purine-2,4(3H,8H)-dione), were studied in animal models through in vitro and in vivo experiments. We demonstrated that AZ-853 and AZ-861, which structurally differ by one substituent and its placement in the phenyl ring, showed varied functional, pharmacological, and pharmacokinetic properties as well as side effect profiles. AZ-861 exhibited stronger agonistic action in all functional assays. After acute and repeated administration in mice, both compounds showed antidepressant-like activity in the forced swim test, which was partially mediated by 5-HT_1A receptor activation. AZ-853 showed a more potent antidepressant-like effect, presumably due to its better penetration into brain structures. Both compounds did not show anticholinergic properties, but after repeated administration, they induced weak sedation and lipid metabolism disturbances without affecting serum glucose level. The stronger α₁-adrenolytic effect of AZ-853 is responsible for decreased systolic blood pressure, and in contrast to AZ-861, AZ-853 induced weight gain in mice. The interesting comparative pharmacological profiles of AZ-853 and AZ-861 encourage to conduct further experiments to fully understand their mechanisms and differences in action.

Central 5-HT receptors and their function; present and future

Since our review of central 5-HT receptors and their function twenty years ago, no new 5-HT receptor has been discovered and there is little evidence that this situation will change in the near future. Nevertheless, over this time significant progress has been made in our understanding of the properties of these receptors and in the clinical translation of this information, and some of these developments are highlighted herein. Such highlights include extensive mapping of 5-HT receptors in both animal and human brain, culminating in readily-accessible brain atlases of 5-HT receptor distribution, as well as emerging data on how 5-HT receptors are distributed within complex neural circuits. Also, a range of important pharmacological and genetic tools have been developed that allow selective 5-HT receptor manipulation, in cells through to whole organism models. Moreover, unexpected complexity in 5-HT receptor function has been identified including agonist-dependent signalling that goes beyond the pharmacology of canonical 5-HT receptor signalling pathways set down in the 1980s and 1990s. This new knowledge of 5-HT signalling has been extended by the discovery of combined signalling of 5-HT and co-released neurotransmitters, especially glutamate. Another important advance has been the progression of a large number of 5-HT ligands through to experimental medicine studies and clinical trials, and some such agents have already become prescribed therapeutic drugs. Much more needs to be discovered and understood by 5-HT neuropharmacologists, not least how the diverse signalling effects of so many 5-HT receptor types interact with complex neural circuits to generate neurophysiological changes which ultimately lead to altered cognitions and behaviour. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

Reverse translation of major depressive disorder symptoms: A framework for the behavioural phenotyping of putative biomarkers

BACKGROUND

Reverse translating putative biomarkers of depression from patients to animals is complex because Major Depressive Disorder (MDD) is a highly heterogenous condition. This review proposes an approach to reverse translation based on relating relevant bio-behavioural functions in laboratory rodents to MDD symptoms.

METHODS

This systematic review outlines symptom clusters assessed by psychometric tests of MDD and antidepressant treatment response including the Montgomery-Åsberg Depression Rating Scale, the Hamilton Depression Rating Scale, and the Beck Depression Inventory. Symptoms were related to relevant behavioural assays in laboratory rodents.

RESULTS

The resulting battery of tests includes passive coping, anxiety-like behaviours, sleep, caloric intake, cognition, psychomotor functions, hedonic reactivity and aversive learning. These assays are discussed alongside relevant clinical symptoms of MDD, providing a framework through which reverse translation of a biomarker can be interpreted.

LIMITATIONS

Certain aspects of MDD may not be quantified by tests in laboratory rodents, and their biological significance may not always be of clinical relevance.

CONCLUSIONS

Using this reverse translation approach, it is possible to clarify the functional significance of a putative biomarker in rodents and hence translate its contribution to specific clinical symptoms, or clusters of symptoms.

Fluorinated indole-imidazole conjugates: Selective orally bioavailable 5-HT7 receptor low-basicity agonists, potential neuropathic painkillers

The 5-HT₇ receptor has recently gained much attention due to its involvement in multiple physiological functions and diseases. The insufficient quality of the available molecular probes prompted design of fluorinated 3-(1-alkyl-1H-imidazol-5-yl)-1H-indoles as a new generation of selective 5-HT₇ receptor agonists. A potent and drug-like agonist, 3-(1-ethyl-1H-imidazol-5-yl)-5-iodo-4-fluoro-1H-indole (AGH-192, 35, K_{i 5-HT7R} = 4 nM), was identified by optimizing the halogen bond formation with Ser5.42 as the supposed partner. The compound was characterized by excellent water solubility, high selectivity over related CNS targets, high metabolic stability, oral bioavailability and low cytotoxicity. Rapid absorption into the blood, medium half-life and a high peak concentration in the brain C_max = 1069 ng/g were found after i.p. (2.5 mg/kg) administration in mice. AGH-192 may thus serve as the long-sought tool compound in the study of 5-HT₇ receptor function, as well as a potential analgesic, indicated by the antinociceptive effect observed in a mouse model of neuropathic pain.

Pharmacology and Therapeutic Potential of the 5-HT7 Receptor

It is well-documented that serotonin (5-HT) exerts its pharmacological effects through a series of 5-HT receptors. The most recently identified member of this family, 5-HT₇, was first identified in 1993. Over the course of the last 25 years, this receptor has been the subject of intense investigation, and it has been demonstrated that 5-HT₇ plays an important role in a wide range of pharmacological processes. As a result of these findings, modulation of 5-HT₇ activity has been the focus of numerous drug discovery and development programs. This review provides an overview of the roles of 5-HT₇ in normal physiology and the therapeutic potential of this interesting drug target.

Serotonin receptors in depression and anxiety: Insights from animal studies

Serotonin regulates many physiological processes including sleep, appetite, and mood. Thus, serotonergic system is an important target in the treatment of psychiatric disorders, such as major depression and anxiety. This natural neurotransmitter interacts with 7 families of its receptors (5-HT1-7), which cause a variety of pharmacological effects. Using genetically modified animals and selective or preferential agonists and antagonist, numerous studies demonstrated the involvement of almost all serotonin receptor subtypes in antidepressant- or anxiolytic-like effects. In this review, based on animal studies, we discuss the possible involvement of serotonin receptor subtypes in depression and anxiety.

Discovery of β-Arrestin Biased Ligands of 5-HT7R

Though many studies have been published about therapeutic potentials of selective 5-HT₇R ligands, there have been few biased ligands of 5-HT₇R. The development of potent and selective biased ligands of 5-HT₇R would be of great help in understanding the relationship between pharmacological effects and G protein/β-arrestin signaling pathways of 5-HT₇R. In order to identify 5-HT₇R ligands with biased agonism, we designed and synthesized a series of tetrahydroazepine derivatives 1 and 2 with arylpyrazolo moiety or arylisoxazolo moiety. Through several biological evaluations such as binding affinity, selectivity profile, and functions in G protein and β-arrestin signaling pathways, 3-(4-chlorophenyl)-1,4,5,6,7,8-hexahydropyrazolo[3,4- d]azepine 1g was discovered as the β-arrestin biased ligand of 5-HT₇R. In an electroencephalogram (EEG) test, 1g increased total non-rapid eye movement (NREM) sleep time and decreased total rapid eye movement (REM) sleep time.

Structure-Activity Relationships and Therapeutic Potentials of 5-HT7 Receptor Ligands: An Update

Serotonin 5-HT₇ receptor (5-HT₇R) has been the subject of intense research efforts because of its presence in brain areas such as the hippocampus, hypothalamus, and cortex. Preclinical data link the 5-HT₇R to a variety of central nervous system processes including the regulation of circadian rhythms, mood, cognition, pain processing, and mechanisms of addiction. 5-HT₇R blockade has antidepressant effects and may ameliorate cognitive deficits associated with schizophrenia. 5-HT₇R has been recently shown to modulate neuronal morphology, excitability, and plasticity, thus contributing to shape brain networks during development and to remodel neuronal wiring in the mature brain. Therefore, the activation of 5-HT₇R has been proposed as a therapeutic approach for neurodevelopmental and neuropsychiatric disorders associated with abnormal neuronal connectivity. This Perspective celebrates the silver jubilee of the discovery of 5-HT₇R by providing a survey of recent studies on the medicinal chemistry of 5-HT₇R ligands and on the neuropharmacology of 5-HT₇R.

The role of aryl-topology in balancing between selective and dual 5-HT7R/5-HT1A actions of 3,5-substituted hydantoins

In order to search for active and selective serotonin 5-HT₇R antagonists among 3,5-disubstituted arylpiperazine-imidazolidine-2,4-diones, the role of the introduction/deletion and the mutual orientation of aromatic rings was analyzed. Chemical modifications of 2nd generation lead structure of 3-(3-(4-(diphenylmethyl)piperazin-1-yl)-2-hydroxypropyl)-5-(4-fluorophenyl)-5-methylimidazolidine-2,4-dione (2, KKB16) were performed. New derivatives (4-18) were designed and synthesized. X-ray crystallographic analysis of the representative compound 5-(4-fluorophenyl)-3-[2-hydroxy-3-(4-phenylpiperazin-1-yl)propyl]-5-methylimidazolidine-2,4-dione (3) was performed to support molecular modeling and SAR studies. The affinity for 5-HT₇R, D₂R and 5-HT_1AR in radioligand binding assays for the entire series and ADME-Tox parameters in vitro for selected compounds (7, 10, and 13) were evaluated. Molecular docking and pharmacophore model assessment were performed. According to the obtained results, 5-methyl-5-naphthylhydantoin derivatives were found to be the new highly active 5-HT₇R agents (K_i ≤ 5 nM) with significant selectivity over 5-HT_1AR and D₂R. On the contrary, the (1-naphthyl)piperazine moiety was gained with the potent dual 5-HT₇R/5-HT_1AR action (K_i: 11 nM/19 nM).

Five potential therapeutic agents as antidepressants: a brief review and future directions

Despite the availability of numerous antidepressants, many patients with depression do not show adequate response. The therapeutic lag between drug administration and onset of clinical improvement observed with conventional antidepressants has led to a need for antidepressants with a novel mechanism of action. Recently, five such agents, including acetyl-L-carnitine, scopolamine, ω-3 polyunsaturated fatty acids, ketamine, and selective 5-HT7 serotonin receptor antagonists, have gained interest as potential antidepressants with enhanced symptom control, improved tolerability, and faster onset of action compared to conventional antidepressants. This review provides an update and critical examination of these five novel therapeutic agents as potential antidepressants.

MF-8, a novel promising arylpiperazine-hydantoin based 5-HT7 receptor antagonist: In vitro drug-likeness studies and in vivo pharmacological evaluation

We report the in vitro drug-likeness studies and in vivo pharmacological evaluation for a new potent 5-HT₇ receptor antagonist MF-8 (5-(4-fluorophenyl)-3-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)-5-methylhydantoin). The in vitro tests showed good permeability, very good metabolic stability, low risk of drug-drug interactions and satisfying safety profile. Moreover, MF-8 showed excellent antidepressant-like activity in the forced swim test in rodents and promising anxiolytic-like activity in the four-plate test in mice. Regarding the potent affinity, high selectivity and antagonistic activity of MF-8 for the 5-HT₇ receptor as well as excellent drug - like properties in vitro and confirmed in vivo pharmacological activity, MF-8 should be considered as a very significant molecule in the search for a new class of anti-depressant drugs.

In the search for a lead structure among series of potent and selective hydantoin 5-HT7 R agents: The drug-likeness in vitro study

Since the year 1993, when 5-HT₇ receptor (5-HT₇ R) was discovered, there is no selective 5-HT₇ R ligand introduced to the pharmaceutical market. One out of the main reasons disqualifying the 5-HT₇ R ligands is weak drugability properties, including metabolic instability or low permeability. This study is focused on the search of a lead compound by "drug-likeness" estimation of the first series of selective and potent 5-HT₇ R ligands among 5-(4-fluorophenyl)-3-(2-hydroxy-3-(4-aryl-piperazin-1-yl)propyl)-5-methylimidazolidine-2,4-dione derivatives (11-16). The most important drugability parameters, i.e., permeability, metabolic stability, and safety, have been evaluated. The main metabolic pathways were determined. The forced swim test (FST) in mice was performed as a primary in vivo assay for compound 13 and the reference 2. The experiments showed promising drug-like properties for all ligands, with special attention to the benzhydryl (diphenylmethyl) derivative 13. The studies have also indicated in vivo activity of the compound 13 that was observed as a significant and specific antidepressant-like activity in the FST. Taking into account the beneficial properties of 13, i.e., good drug-like parameters, the significant antagonistic action, high selectivity to 5-HT₇ R, and its in vivo antidepressant-like activity, the compound should be considered as a new lead in the search for drugs acting on CNS via 5-HT₇ receptor.

Asenapine modulates mood-related behaviors and 5-HT1A/7 receptors-mediated neurotransmission

AIM

Asenapine is a new atypical antipsychotic prescribed for the treatment of psychosis/bipolar disorders that presents higher affinity for serotonergic than dopaminergic receptors. The objective of this study was to investigate its antidepressant-like and antimanic-like properties on relevant animal models of depression and mania and to assess the acute and chronic effect of Asenapine on dorsal raphe nucleus (DRN) 5-HT cell firing activity.

METHODS

We assessed the effects of Asenapine using in vivo electrophysiological and behavioral assays in rats.

RESULTS

Behavioral experiments showed that Asenapine had no significant effect on immobility time in the forced swim test (FST) in control rats. In the ACTH-treated rats, a model of antidepressant-resistance, Asenapine failed to alter immobility time in the FST. In contrast in the sleep deprivation (SD) model of mania, acute administration of Asenapine significantly decreased the hyperlocomotion of SD rats. In the DRN, acute administration of Asenapine reduced the suppressant effect of the selective 5-HT₇ receptor agonist LP-44 and of the prototypical 5-HT_1A receptor agonist 8-OH-DPAT on 5-HT neuronal firing activity. In addition, chronic treatment with Asenapine enhanced DRN 5-HT neuronal firing and this effect was associated with an alteration of the 5-HT₇ receptor responsiveness.

CONCLUSION

These results confirm that Asenapine displays robust antimanic property and effective in vivo antagonistic activity at 5-HT_1A/7 receptors.

Novel 5-HT7R antagonists, arylsulfonamide derivatives of (aryloxy)propyl piperidines: Add-on effect to the antidepressant activity of SSRI and DRI, and pro-cognitive profile

A novel series of arylsulfonamide derivatives of (aryloxy)propyl piperidines was designed to obtain potent 5-HT₇R antagonists. Among the compounds evaluated herein, 3-chloro-N-{1-[3-(1,1-biphenyl-2-yloxy)2-hydroxypropyl]piperidin-4-yl}benzenesulfonamide (25) exhibited antagonistic properties at 5-HT₇R and showed selectivity over selected serotoninergic and dopaminergic receptors, as well as over serotonin, noradrenaline and dopamine transporters. Compound 25 demonstrated significant antidepressant-like activity in the forced swim test (0.625-2.5mg/kg, i.p.) and in the tail suspension test (1.25mg/kg, i.p.), augmented the antidepressant effect of inactive doses of escitalopram (selective serotonin reuptake inhibitor) and bupropion (dopamine reuptake inhibitor) in the FST in mice, and similarly to SB-269970, exerted pro-cognitive properties in the novel object recognition task in cognitively unimpaired conditions in rats (0.3mg/kg, i.p.). Such an extended pharmacological profile, especially the augmentation effect of the identified 5-HT₇R antagonist on SSRI activity, seems promising regarding the complexity of affective disorders and potentially improved outcomes, including mnemonic performance.

[Antidepressant and tolerance: Determinants and management of major side effects]

Antidepressant therapy aims to reach remission of depressive symptoms while reducing the complications and risks of relapse. Even though they have proven their efficacy, it takes several weeks for antidepressants to demonstrate full effectiveness, and adverse effects occur more quickly or (quicker) which can be a source of poor compliance. This latest aspect often leads to dose reduction and/or change of molecule that have the effect of delaying remission. This review attempts to present, from the pharmacological properties of the major classes of antidepressants (monoamine oxidase inhibitor [MAOI], tricyclic antidepressants [TCA], selective serotonin reuptake inhibitor [SSRI] and serotonin and noradrenaline reuptake inhibitor [SNRI]), to the pharmacological mechanisms involved in adverse effects by focusing on sexual dysfunction, nausea/vomiting, and weight changes and sleep disruption. If the activation of dopamine D_1/2 or norepinephrine receptors through the autonomic nervous system controls and facilitates sexual desire, increasing serotoninergic transmission through 5-HT_1B/2A/2C receptors activation inhibits this process. The pharmacological properties of drugs inducing nausea/vomiting activate opiate receptors μ, increase dopaminergic and serotoninergic transmission activating the dopamine D₂ and serotonin 5-HT₃ receptors, respectively. Among the causes responsible for weight gain under antidepressant therapy, monoamine neurotransmission still plays an important role. The blockade of serotonin 5-HT_2C or histamine H₁ receptors is directly responsible for weight gain. Finally, the activation of 5-HT_1A/1B/3/7 serotoninergique receptors modulates wakefulness, raid eyes movement or sleep duration. In conclusion, if antidepressant activity of SERT or MAO inhibitors is an indirect consequence of postsynaptic 5-HT, DA, NA receptor activation, it is also responsible for side effects, causes of poor compliance and hence therapeutic failures. Finally, we need to take into account the key role of the nocebo effect in the occurrence of adverse effects. The next generation of antidepressant would aim to have a rapid efficacy in patients unresponsive or resistant to drugs currently available while improving certain effects of tolerance through an optimization of their psychopharmacological properties leading to a reduction of their side effects.

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.

Novel N-acyl-carbazole derivatives as 5-HT7R antagonists

To discover a novel 5-HT7R antagonist for treatment of depression, we designed N-acyl-carbazole derivatives which were synthesized and biologically evaluated against 5-HT7R. Among total 30 compounds synthesized, four compounds 27-30 showed good binding affinities with Ki values of <100 nM. The compound 28, 1-(9H-carbazol-9-yl)-6-(4-(2-methoxyphenyl)piperazin-1-yl)hexan-1-one, showed good selectivity over other serotonin receptor subtypes and turned out to be a novel selective 5-HT7R antagonist following functional assays. The compound 28 showed moderate activity on hERG channel and good stability in microsomal stability test. The compound 28 exhibited a good pharmacokinetic profile with 67.8% oral bioavailability and good penetration to the brain. The compound 28 was also tested in in vivo depression animal model and showed antidepressant effect in the forced swimming test. Therefore, the selective 5-HT7R antagonist 28 can be considered as a good lead for discovery of novel 5-HT7R antagonists as antidepressants.