Treatment of cognitive dysfunction in major depressive disorder—a review of the preclinical evidence for efficacy of selective serotonin reuptake inhibitors, serotonin–norepinephrine reuptake inhibitors and the multimodal-acting antidepressant vortioxetine

Effects of chronic stress on cognitive function - From neurobiology to intervention

Exposure to chronic stress contributes considerably to the development of cognitive impairments in psychiatric disorders such as depression, generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and addictive behavior. Unfortunately, unlike mood-related symptoms, cognitive impairments are not effectively treated by available therapies, a situation in part resulting from a still incomplete knowledge of the neurobiological substrates that underly cognitive domains and the difficulty in generating interventions that are both efficacious and safe. In this review, we will present an overview of the cognitive domains affected by stress with a specific focus on cognitive flexibility, behavioral inhibition, and working memory. We will then consider the effects of stress on neuronal correlates of cognitive function and the factors which may modulate the interaction of stress and cognition. Finally, we will discuss intervention strategies for treatment of stress-related disorders and gaps in knowledge with emerging new treatments under development. Understanding how cognitive impairment occurs during exposure to chronic stress is crucial to make progress towards the development of new and effective therapeutic approaches.

Design, synthesis and biological evaluation of arylpropylamine derivatives as potential multi-target antidepressants

In this study, a series of novel arylpropylamine derivatives were designed, synthesized and evaluated as potential multi-target antidepressants. Among them, compound (R)-13j displayed unique pharmacological features, exhibiting excellent inhibitory potency against serotonin and noradrenaline transporters (SERT/NET) and high affinity for 5-HT2A/2C receptor, and showing low affinity for histamine H1, adrenergic α1 receptors and hERG channels (to reduce QT interval prolongation). Molecular docking studies provided a rational binding model of (R)-13j in complex with SERT and 5-HT2A/2C receptor. In animal models, compound (R)-13j dose-dependently reduced the immobility time in the tail suspension test (TST) and the forced swimming test (FST) in mice, with higher efficacy when compared to duloxetine, and showed no stimulatory effect on the locomotor activity. Moreover, compound (R)-13j significantly shortened the immobility time in the ACTH-induced rat model of treatment-resistant depression (TRD). Furthermore, compound (R)-13j also exhibited a higher threshold for acute toxicity than duloxetine. In addition, compound (R)-13j possessed a favorable pharmacokinetic profile in mice. Taken together, compound (R)-13j may constitute a novel class of drugs for the treatment of depression.

Psilocybin as a lead candidate molecule in preclinical therapeutic studies of psychiatric disorders: A systematic review

Psilocybin is the main psychoactive compound found in hallucinogenic/magic mushrooms and can bind to both serotonergic and tropomyosin receptor kinase b (TrkB) receptors. Psilocybin has begun to show efficacy for a range of neuropsychiatric conditions, including treatment-resistant depression and anxiety disorders; however, neurobiological mechanisms are still being elucidated. Clinical research has found that psilocybin can alter functional connectivity patterns in human brains, which is often associated with therapeutic outcomes. However, preclinical research affords the opportunity to assess the potential cellular mechanisms by which psilocybin may exert its therapeutic effects. Preclinical rodent models can also facilitate a more tightly controlled experimental context and minimise placebo effects. Furthermore, where there is a rationale, preclinical researchers can investigate psilocybin administration in neuropsychiatric conditions that have not yet been researched clinically. As a result, we have systematically reviewed the knowledge base, identifying 82 preclinical studies which were screened based on specific criteria. This resulted in the exclusion of 44 articles, with 34 articles being included in the main review and another 2 articles included as Supporting Information materials. We found that psilocybin shows promise as a lead candidate molecule for treating a variety of neuropsychiatric conditions, albeit showing the most efficacy for depression. We discuss the experimental findings, and identify possible mechanisms whereby psilocybin could invoke therapeutic changes. Furthermore, we critically evaluate the between-study heterogeneity and possible future research avenues. Our review suggests that preclinical rodent models can provide valid and translatable tools for researching novel psilocybin-induced molecular and cellular mechanisms, and therapeutic outcomes.

Structural determinants for activity of the antidepressant vortioxetine at human and rodent 5-HT3 receptors

Vortioxetine (VTX) is a recently approved antidepressant that targets a variety of serotonin receptors. Here, we investigate the drug's molecular mechanism of operation at the serotonin 5-HT3 receptor (5-HT3R), which features two properties: VTX acts differently on rodent and human 5-HT3R, and VTX appears to suppress any subsequent response to agonists. Using a combination of cryo-EM, electrophysiology, voltage-clamp fluorometry and molecular dynamics, we show that VTX stabilizes a resting inhibited state of the mouse 5-HT3R and an agonist-bound-like state of human 5-HT3R, in line with the functional profile of the drug. We report four human 5-HT3R structures and show that the human receptor transmembrane domain is intrinsically fragile. We also explain the lack of recovery after VTX administration via a membrane partition mechanism.

Cognitive enhancing effect of rTMS combined with tDCS in patients with major depressive disorder: a double-blind, randomized, sham-controlled study

BACKGROUND

Cognitive dysfunction is one of the common symptoms in patients with major depressive disorder (MDD). Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) have been studied separately in the treatment of cognitive dysfunction in MDD patients. We aimed to investigate the effectiveness and safety of rTMS combined with tDCS as a new therapy to improve neurocognitive impairment in MDD patients.

METHODS

In this brief 2-week, double-blind, randomized, and sham-controlled trial, a total of 550 patients were screened, and 240 MDD inpatients were randomized into four groups (active rTMS + active tDCS, active rTMS + sham tDCS, sham rTMS + active tDCS, sham rTMS + sham tDCS). Finally, 203 patients completed the study and received 10 treatment sessions over a 2-week period. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was performed to assess patients' cognitive function at baseline and week 2. Also, we applied the 24-item Hamilton Depression Rating Scale (HDRS-24) to assess patients' depressive symptoms at baseline and week 2.

RESULTS

After 10 sessions of treatment, the rTMS combined with the tDCS group showed more significant improvements in the RBANS total score, immediate memory, and visuospatial/constructional index score (all p < 0.05). Moreover, post hoc tests revealed a significant increase in the RBANS total score and Visuospatial/Constructional in the combined treatment group compared to the other three groups but in the immediate memory, the combined treatment group only showed a better improvement than the sham group. The results also showed the RBANS total score increased significantly higher in the active rTMS group compared with the sham group. However, rTMS or tDCS alone was not superior to the sham group in terms of other cognitive performance. In addition, the rTMS combined with the tDCS group showed a greater reduction in HDRS-24 total score and a better depression response rate than the other three groups.

CONCLUSIONS

rTMS combined with tDCS treatment is more effective than any single intervention in treating cognitive dysfunction and depressive symptoms in MDD patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2100052122).

Stress-related cellular pathophysiology as a crosstalk risk factor for neurocognitive and psychiatric disorders

In this narrative review, we examine biological processes linking psychological stress and cognition, with a focus on how psychological stress can activate multiple neurobiological mechanisms that drive cognitive decline and behavioral change. First, we describe the general neurobiology of the stress response to define neurocognitive stress reactivity. Second, we review aspects of epigenetic regulation, synaptic transmission, sex hormones, photoperiodic plasticity, and psychoneuroimmunological processes that can contribute to cognitive decline and neuropsychiatric conditions. Third, we explain mechanistic processes linking the stress response and neuropathology. Fourth, we discuss molecular nuances such as an interplay between kinases and proteins, as well as differential role of sex hormones, that can increase vulnerability to cognitive and emotional dysregulation following stress. Finally, we explicate several testable hypotheses for stress, neurocognitive, and neuropsychiatric research. Together, this work highlights how stress processes alter neurophysiology on multiple levels to increase individuals' risk for neurocognitive and psychiatric disorders, and points toward novel therapeutic targets for mitigating these effects. The resulting models can thus advance dementia and mental health research, and translational neuroscience, with an eye toward clinical application in cognitive and behavioral neurology, and psychiatry.

Aquaporin 4 beyond a water channel; participation in motor, sensory, cognitive and psychological performances, a comprehensive review

Aquaporin 4 (AQP4) is a protein highly expressed in the central nervous system (CNS) and peripheral nervous system (PNS) as well as various other organs, whose different sites of action indicate its importance in various functions. AQP4 has a variety of essential roles beyond water homeostasis. In this article, we have for the first time summarized different roles of AQP4 in motor and sensory functions, besides cognitive and psychological performances, and most importantly, possible physiological mechanisms by which AQP4 can exert its effects. Furthermore, we demonstrated that AQP4 participates in pathology of different neurological disorders, various effects depending on the disease type. Since neurological diseases involve a spectrum of dysfunctions and due to the difficulty of obtaining a treatment that can simultaneously affect these deficits, it is therefore suggested that future studies consider the role of this protein in different functional impairments related to neurological disorders simultaneously or separately by targeting AQP4 expression and/or polarity modulation.

Saffron carotenoids reversed the UCMS-induced depression and anxiety in rats: Behavioral and biochemical parameters, and hippocampal BDNF/ERK/CREB and NR2B signaling markers

BACKGROUND

Depression is a debilitating condition that affects the mind and the individual's body. The improving effects of saffron on depression and anxiety have long been discussed, with limited information about the molecular mechanism of action.

HYPOTHESIS/PURPOSE

Investigating the effect of saffron carotenoids, Crocin and Crocetin, on depression and anxiety in rats by emphasizing some signaling pathways involved.

STUDY DESIGN

Depression and anxiety were induced in rats via unpredictable chronic mild stress (UCMS). Then different rat groups were treated with Crocin, Crocetin, Fluoxetine, and vehicle. Behavioral tests were done before and after treatment.

METHODS

The serum Serotonin and Corticosterone and the expression of some hippocampal signaling proteins were studied. Furthermore, bioinformatics tools were used to predict the interactions of Crocin/ Crocetin with the Serotonin transporter and NMDA receptor subunit NR2B. Then, the patch-clamp was used to study the interaction of Crocetin with the NMDA receptor.

RESULTS

Various behavioral tests confirmed the induction of depression and the improvement of depression by these natural carotenoids. In addition, Crocin/ Crocetin significantly increased the decreased serum Serotonin and reduced the increased serum Corticosterone in the depressed groups. They also increased or caused a trend of increase in the CREB, ERK, BAD, BDNF, p11, and 5-HT1B expression in the hippocampus of the depressed groups. In addition, there were an increase or a trend in p-CREB/CREB, p-ERK1/2 /ERK1/2, and p-BAD/BAD ratios in the Crocin/ Crocetin treated depressed groups. However, the NR2B and FOXO3a expression showed a trend of decrease in depressed groups after treatment. The bioinformatics data indicated that Crocin/ Crocetin could bind to the Serotonin transporter (SLC6A4) and NR2B subunit of the NMDA receptor. Both carotenoids bind to the same site as Fluoxetine in the SLC6A4. However, they bound to different sites on the NR2B. So, Crocetin binds to NR2B at the same site as Ifenprodil. But Crocin bound to another site. The whole cell patch-clamp recording on the normal rat hippocampus revealed a significant decrease in the NMDA peak amplitude after Crocetin treatment, indicating its inhibitory effect on this receptor.

CONCLUSION

The antidepressant activities of Crocin/ Crocetin are possibly due to their effects on Serotonin and Corticosterone serum concentrations, NR2B expression, and the downstream signaling pathways. Furthermore, these natural carotenoids, like Fluoxetine, induced an increasing tendency in p11 and 5HT1B in depressed rats.

A comprehensive review and meta-analysis of neurological side effects related to second-generation antidepressants in individuals with major depressive disorder

Second-generation antidepressants (SGADs) often cause neurological side effects (SEs). This meta-analysis seeks to quantify the short-term rates of neurological SEs related to routinely used second-generation antidepressants used to treat major depressive disorder (MDD). A search of the PubMed, EMBASE,Cochrane Library databases and Web of Science was done to uncover double-blind, randomized, placebo-controlled studies evaluating the effectiveness of frequently used SGADs medicines in people with MDD. Qualifying studies were required to concentrate on the use of SGADs routinely used in MDD and to uncover data on treatment-emergent neurological SEs occurring within 12 weeks of therapy. Overall, 143 RCT studies containing 188 treatment arms were included in the meta-analyses. Most SGADs increased the risk of neurological SEs compared to placebo. The least tolerated antidepressants on the neurological tract were desvenlafaxine (OR=1.98; CI 0.85-4.65; p-value=0.12) and venlafaxine (OR=1.15; CI 0.96-1.38; p-value=0.13). Agomelatine, bupropion and vortioxetine exhibited reduced neurological SEs, showing diminished risk in insomnia (OR=0.56; CI 0.36-0.88; p-value=0.01), somnolence (OR=0.46; CI 0.27-0.79; p-value=0.01), vision blurred (OR=0.43; CI 0.19-0.96; p-value=0.04), respectively. Most SGADs did not or just marginally increased the risk of headache compared to placebo. In conclusion, frequently used SGADs demonstrated distinct patterns of neurological SEs, which physicians should consider when prescribing antidepressants to promote treatment adherence and favorable outcomes in patients with MDD.

Opportunities and challenges to non-communicable disease (NCD) research and training in Pakistan: a qualitative study from Pakistan

INTRODUCTION

Most of the global non-communicable disease (NCD)-related death burden is borne by low and middle-income countries (LMICs). In LMICs like Pakistan, however, a major gap in responding to NCDs is a lack of high-quality research leading to policy development and implementation of NCDs. To assess institutional opportunities and constraints to NCD research and training we conducted a situational analysis for NCD research and training at Aga Khan University Pakistan.

METHODS

We conducted a descriptive exploratory study using grounded theory as a qualitative approach: semistructured interviews of 16 NCD stakeholders (three excluded) and two focus group discussions with postgraduate and undergraduate trainees were conducted. A simple thematic analysis was done where themes were identified, and then recurring ideas were critically placed in their specific themes and refined based on the consensus of the investigators.

RESULTS

The major themes derived were priority research areas in NCDs; methods to improve NCD research integration; barriers to NCD research in LMICs like Pakistan; design of NCD research programme and career paths; and NCD prevention at mass level, policy and link to the government. In general, participants opined that while there was an appetite for NCD research and training, but few high-quality research training programmes in NCDs existed, such programmes needed to be established. The ideal NCD research and training programmes would have in-built protected time, career guidance and dedicated mentorship. Most participants identified cardiovascular diseases as a priority thematic area and health information technology and data science as key methodological approaches to be introduced into research training.

CONCLUSION

We conclude from this qualitative study on NCD research and training that high-quality research training programmes for NCDs are rare. Such programmes need to be established with in-built protected time, career guidance and mentorship for the trainees to improve their research capacity in Pakistan.

The effectiveness of high-frequency left DLPFC-rTMS on depression, response inhibition, and cognitive flexibility in female subjects with major depressive disorder

BACKGROUND

The purpose of the present study was to investigate the effect of high-frequency repetitive transcranial magnetic stimulation on depression severity, response inhibition, and cognitive flexibility in subjects with major depressive disorder.

METHODS

Twenty-eight female subjects with major depressive disorder were randomly divided into experimental and control groups. High frequency (20 Hz) rTMS stimulation at 85% of the MT consisted of 25 trains of 5 s duration, a total of 2500 pulses/session or sham stimulation was applied over the left DLPFC for five consecutive days per week, for two weeks. Depression severity, response inhibition, and cognitive flexibility of subjects were assessed by Beck Depression Inventory, Go/NoGo, and Wisconsin sort cards (WCST) tests, respectively, pre- and post-TMS intervention.

RESULTS

rTMS over the left DLPFC significantly decreased the depression severity at the Beck Depression Inventory, enhanced accuracy, and decreased reaction time at the Go/NoGo task. In the Wisconsin Card Sort Test, perseverative and non-perseverative errors and failure to maintain a set index significantly decreased following rTMS treatment.

CONCLUSIONS

Findings indicate that 20-Hz rTMS treatment on the left DLPFC has a positive effect on depression severity, response inhibition, and cognitive flexibility in depressed subjects.

Adult Neurogenesis and Antidepressant Treatment: The Surprise Finding by Ron Duman and the Field 20 Years Later

Of Duman's many influential findings, the finding that long-term treatment with antidepressant drugs produces an increase in neurogenesis in the subgranular zone of the adult hippocampus may be one of the most enduring and far-reaching. This novel discovery and his decades of continued research in the field led to a new hypothesis about the mechanism of action of antidepressants, providing a critical step in our understanding of the neurotrophic hypothesis of depression and synaptic plasticity. It is now accepted that antidepressant treatments can oppose and even reverse the effects of stress on the brain and on newly born hippocampal cells, possibly via neurotrophic factors, which Duman had continued to explore. Furthermore, ablation studies have shown preclinically that hippocampal neurogenesis may be necessary for some of the clinical effects of antidepressant drugs. Duman's laboratory continued to interrogate neurotrophins and synaptic plasticity, demonstrating that newer clinically approved antidepressant compounds also affect neurogenesis and synaptic plasticity. In this review, we summarize Duman's original findings and discuss the current state of the field of neurogenesis with respect to animal models and human studies and the implications of those findings on the field of drug discovery.

Depressive Symptoms are Associated with low Serotonin Levels in Plasma but are not 5-HTTLPR Genotype Dependent in Older Adults

Depressive symptoms are diagnosed by physicians using scales but their pathophysiology is unclear. Low serotonin (5-HT) levels play an important role in depression, and the 5-HT transporter (5-HTT) is an important regulator of plasma serotonin levels and reuptake. Additionally, the 5-HTT gene-linked polymorphic region (5-HTTLPR) is associated with depression. The aim was to clarify the roles of plasma serotonin levels in plasma and the 5HTTPLR polymorphism in depressive symptoms in older adults. A total of 84 older adult participants were evaluated. Depressive symptoms were measured using the Center for Epidemiologic Studies Depression Scale of 20 items (CESD-20). The plasma serotonin levels were determined by ELISA, and the 5-HTTLPR genotype was analyzed by PCR. Depressive symptoms were present in 39.3% (N = 33) of the participants. The median plasma serotonin level was 204.34 ng/mL (SD = 93.88). A significant correlation was found between the CESD-20 scale and plasma serotonin levels (r = -.256; p = .019). Low serotonin levels were associated with the presence of depressive symptoms (p = .001). The 5-HTTLPR analysis showed that of the 84 older adults, 35.7% had the SS genotype, 10.7% had the LL genotype, and 53.6% were heterozygous. The 5-HTTLPR polymorphism was not associated with depressive symptoms (p = .587) and plasma serotonin levels (p = 0.391). Depressive symptoms correlate with low serotonin levels in plasma, but not with the 5-HTTLPR polymorphism in older Mexican adults.

GABA Supplementation Negatively Affects Cognitive Flexibility Independent of Tyrosine

Increasing evidence, particularly from animal studies, suggests that dopamine and GABA are important modulators of cognitive flexibility. In humans, increasing dopamine synthesis through its precursor tyrosine has been shown to result in performance improvements, but few studies have reported the effects of GABA supplementation in healthy participants. We conducted a double-blind, placebo-controlled, randomized experiment to test the interactive effects of tyrosine and GABA administration on two measures of cognitive flexibility, response inhibition and task switching. A total of 48 healthy volunteers were split into four groups (placebo, tyrosine alone, GABA alone, and tyrosine and GABA combined). They completed cognitive flexibility tasks at baseline and after drug administration. We found that tyrosine alone had no impact on the measures of cognitive flexibility, whereas GABA alone and in combination with tyrosine worsened task switching. Our results provide preliminary evidence that putative increases in GABA and dopamine synthesis do not interact to affect cognitive flexibility performance.

Vortioxetine on Cognition in Schizophrenia: A Pilot Study

BACKGROUND

Given the wide implications of cognitive impairment for prognosis and outcome in schizophrenia, the research on pharmacological approaches aimed at addressing dysfunctional cognition has been extensive; nevertheless, there are no currently available licensed drugs, and the evidence in this field is still unimpressive. Vortioxetine is a multimodal antidepressant, which has been proposed as a suitable treatment option for cognitive symptoms in depression.

METHODS

Twenty schizophrenia outpatients (mean age ± SD, 40.7 ±10.6 years) on stable clozapine treatment, assessed by neuropsychological (Wisconsin Card Sorting Test, Verbal Fluency, and Stroop task) and psychodiagnostic instruments (Positive and Negative Syndrome Scale [PANSS] and Calgary Depression Scale for Schizophrenia), received vortioxetine at the single daily dose of 10 mg/d until week 12; the dose was increased at 20 mg/d afterward, and this dosage was maintained unchanged until week 24. A physical examination, electrocardiogram with QTc measurement, and laboratory tests were also performed.

RESULTS

Vortioxetine supplementation significantly improved Stroop test (P = 0.013) at week 12 and Stroop test (P = 0.031) and Semantic Fluency (P = 0.002) at end point. Moreover, a significantly reduction of PANSS domains "positive" (P = 0.019) at week 12 and of PANSS domains positive (P = 0.019) and total score (P = 0.041) and of depressive symptoms (Calgary Depression Scale for Schizophrenia, P = 0.032) at end point. There was no significant change in clinical, metabolic, and safety parameters, and no subject spontaneously reported adverse effects.

CONCLUSIONS

Despite the limitations (open design, lack of a control group, small sample size, and short intervention period), our findings suggest for the first time that vortioxetine augmentation of clozapine may be a promising therapeutic strategy for addressing cognitive deficits in patients with schizophrenia.

Learned Immobility Produces Enduring Impairment of the HPA Axis Reactivity in Mice without Replicating the Broad Spectrum of Depressive-Like Phenotype

The forced swim stress test (FST) is widely used for screening pharmacological or non-pharmacological strategies with potential antidepressant activities. Recent data have suggested that repeated FST for five consecutive days (i.e., 5d-RFSS) could be used to generate a robust depressive-like phenotype in mice. However, the face, construct, and predictive validities of 5d-RFSS have been recently challenged. This study took advantage of recent findings showing that mice vulnerability to anxiety is enhanced when animals are stressed during the dark phase, to provide new insight into the relevance of this model. Our results showed a progressive increase in time of immobility in 5d-RFSS mice relative to control non-stressed animals (sham). Three weeks later, we noticed that 5d-RFSS mice injected with the vehicle compound (Veh) still exhibited a high level of immobility in the FST whereas this behavior was reversed by the antidepressant drug amitriptyline (AMI). However, 5d-RFSS/Veh and 5d-RFSS mice/AMI mice showed normal performances in the open field, the novelty suppressed feeding and the tail suspension tests. Despite this lack of generalized behavioral deficits, an impairment of different parameters characterizing the hypothalamic-pituitary-adrenal (HPA) axis reactivity was evidenced in 5d-RFSS mice/Veh but not in 5d-RFSS mice/AMI. Despite anomalies in the HPA axis, the activity of the central serotonergic system remained unaffected in 5d-RFSS mice relative to controls. From our results, it is suggested that learned immobility does not replicate the broad spectrum of depressive symptoms observed in other chronic models of depression such as the unpredictable chronic mild stress (UCMS) model, the chronic social defeat stress (CSDS) model or chronic corticosterone (CORT) exposure but its influence on the HPA axis is remarkable. Further experiments are warranted to makes this model suitable for modelling depression and therefore refine its translational applicability.

Effect of a 5-HT7 Receptor Antagonist on Reversal Learning in the Rat Attentional Set-Shifting Test

5-HT7 receptor antagonism has been shown to ameliorate ketamine-induced schizophrenia-like deficits in extradimensional set-shifting using the attentional set-shifting task (ASST). However, this rodent paradigm distinguishes between several types of cognitive rigidity associated with neuropsychiatric conditions. The goal of this study was to test 5-HT7 receptor involvement in the reversal learning component of the ASST because this ability depends primarily on the orbito-frontal cortex, which shows strong 5-HT7 receptor expression. We found that impaired performance on the ASST induced by NMDA receptor blockade (MK-801, 0.2 mg/kg) in 14 rats was reversed by coadministration of the 5-HT7 receptor antagonist SB-269970. The strongest effect was found on the reversal phases of ASST, whereas injection of SB-269970 alone had no effect. These results indicate that 5-HT7 receptor mechanisms may have a specific contribution to the complex cognitive deficits, increasing perseverative responding, in psychiatric diseases, including schizophrenia, depression, and anorexia nervosa, which express different forms of cognitive inflexibility.

Specific Localization of an Auto-inhibition Mechanism at Presynaptic Terminals of Identified Serotonergic Neurons

Auto-regulation mechanisms in serotonergic neurons regulate their electrical activity and secretion. Since these neurons release serotonin from different structural compartments - including presynaptic terminals, soma, axons and dendrites - through different mechanisms, autoregulation mechanisms are also likely to be different at each compartment. Here we show that a chloride-mediated auto-inhibitory mechanism is exclusively localized at presynaptic terminals, but not at extrasynaptic release sites, in serotonergic Retzius neurons of the leech. An auto-inhibition response was observed immediately after intracellular stimulation with an electrode placed in the soma, in neurons that were isolated and cultured retaining an axonal stump, where presynaptic terminals are formed near the soma, but not in somata isolated without axon, where no synaptic terminals are formed, nor in neurons in the nerve ganglion, where terminals are electrotonically distant from the soma. Furthermore, no auto-inhibition response was detected in either condition during the longer time course of somatic secretion. This shows that the auto-inhibition effects are unique to nerve terminals. We further determined that serotonin released from peri-synaptic dense-core vesicles contributes to auto-inhibition in the terminals, since blockade of L-type calcium channels, which are required to stimulate extrasynaptic but not synaptic release, decreased the amplitude of the auto-inhibition response. Our results show that the auto-regulation mechanism at presynaptic terminals is unique and different from that described in the soma of these neurons, further highlighting the differences in the mechanisms regulating serotonin release from different neuronal compartments, which expand the possibilities of a single neuron to perform multiple functions in the nervous system.

Cost-effectiveness of vortioxetine compared with levomilnacipran and vilazodone in patients with major depressive disorder switching from an initial antidepressant

Introduction: Many patients with major depressive disorder (MDD) do not achieve remission with their first antidepressant (AD), resulting in a high burden due to treatment failure. Vortioxetine is a valid treatment option for patients with MDD only partially responding to their first AD. Characterization of vortioxetine's potential benefits versus other approved treatments is important. Areas covered: The cost-effectiveness of vortioxetine, including cognitive outcomes, was modeled in comparison with levomilnacipran and vilazodone for patients switched to these medications after inadequate responses to a first AD. Expert opinion: Vortioxetine was associated with incremental quality-adjusted life-year (QALY) gains versus levomilnacipran (0.008) or vilazodone (0.009). Vortioxetine was dominant versus levomilnacipran and cost-effective versus vilazodone (incremental cost-effectiveness ratio [ICER],33,829 USD/QALY). In sensitivity analyses using residual cognitive dysfunction rates (vortioxetine, 49%; levomilnacipran, 58%, and vilazodone, 64%), incremental QALY gains for vortioxetine versus levomilnacipran (0.0085) or vilazodone (0.0109) were found. Vortioxetine remained dominant versus levomilnacipran and cost-effective versus vilazodone (ICER, 27,633 USD/QALY). ICER reduction was found with cognition outcomes inclusion. This model provides additional support for considering vortioxetine for patients requiring a switch of MDD treatments, although its conclusions are limited by the data available for inclusion. Additional research and real-world trials are needed to confirm the findings.

Neurocognitive impact of ketamine treatment in major depressive disorder: A review on human and animal studies

BACKGROUND

Most recent evidence support a rapid and sustained antidepressant effect of subanesthetic dose of intravenous ketamine in patients with major depressive disorder (MDD). However, clinical and animal studies investigating the effects of intravenous ketamine on specific functional domains disrupted by depression reported conflicting results. Therefore, the aim of this review is to provide an overview of the recent findings exploring the cognitive effects of ketamine in depression.

METHODS

After a bibliographic search on PubMed, Medline and PsycInfo, we retrieved 11 original studies meeting our research criteria, 7 in humans with MDD or Treatment Resistant Disorder and 4 using rats models for depression.

RESULTS

Overall the results showed that a) ketamine reduced activation and normalized connectivity measures of several brain regions related to depressive behaviors and reversed deficits in cognitive flexibility and coping response strategy in rats with depressive features, and b) ketamine leads to a no significant impairment on neurocognitive functions in most of the studies, with only three studies observing improvements in speed of processing, verbal learning, sustained attention and response control, verbal and working memory.

LIMITATIONS

The methodological heterogeneity, in terms of neuropsychological tests used and cognitive domain explored, of the studies included.

CONCLUSIONS

Most of the studies included showed no significant cognitive impairments in MDD patients after ketamine treatment. Furthermore, the results of the fMRI studies considered suggest that ketamine may have a normalizing effect on brain functions during attentional and emotional processing in MDD patients. However, further studies are needed to confirm these preliminary evidences.

Effectiveness, tolerability, and dropout rates of vortioxetine in comorbid depression: A naturalistic study

OBJECTIVE

Vortioxetine is a novel antidepressant whose safety, tolerability, and therapeutic action have been supported by several studies. The present naturalistic study aimed to characterize its effectiveness, tolerability, and dropout rate in the real world.

METHODS

Total sample consisted of 66 outpatients with major depressive episode, treated with vortioxetine, whose clinical variables were evaluated over three time points.

RESULTS

Most common primary diagnoses were major depressive disorder (45.5%) and bipolar disorder (33.4%), with an overall comorbidity rate of 48.5% and concomitant medications in the 89.4%. The mean vortioxetine daily dosage was 12.90 ± 5.65 mg. Effectiveness of vortioxetine through a significant improvement on specific psychometric scales emerged, while only a nonsignificant trend of association between higher dosage and effectiveness was found. In the total sample, 51.5% were classified as responders and 36.4% as remitters. Two-thirds of subjects did not report side effects, while in the remaining patients, gastrointestinal ones were the most frequent (72.7%). Almost two-thirds of the sample could complete the follow-up, while 36.4% dropped out; the main reasons for dropout were side effects (37.5%) and lack of efficacy (29.2%).

CONCLUSIONS

Larger sample studies are warranted to better characterize vortioxetine effectiveness and tolerability in the real world.

Behavioral and Biochemical Effects of Mukia madrespatana Following Single Immobilization Stress on Rats

BACKGROUND AND OBJECTIVES

Elevated oxidative stress has been shown to play an important role in the diagnosis and prognosis of stress and memory-related complications. Mukia madrespatana (M. madrespatana) has been reported to have various biological and antioxidant properties. We intended to evaluate the effect of M. madrespatana peel on single immobilization stress-induced behavioral deficits and memory changes in rats. Materials and Methods: M. madrespatana peel (2000 mg/kg/day, orally) was administered to control and immobilize stressed animals for 4 weeks. Anxiolytic, antidepressant, and memory-enhancing effects of M. madrespatana were observed in both unstressed and stressed animals. Results: Lipid peroxidation was decreased while antioxidant enzymes were increased in both unstressed and stressed animals. Acetylcholine level was increased while acetylcholinesterase activity was decreased in both M. madrespatana treated unstressed and stressed rats. There was also an improvement in memory function. Serotonin neurotransmission was also regulated in M. madrespatana treated rats following immobilization stress with anxiolytic and anti-depressive effects. Conclusion: Based on the current study, it is suggested that M. madrespatana has strong antioxidant properties and may be beneficial as dietary supplementation in stress and memory-related conditions.

Vortioxetine administration attenuates cognitive and synaptic deficits in 5×FAD mice

RATIONALE AND OBJECTIVE

Vortioxetine has been reported to exhibit a variety of neurobiological functions and neuroprotective effects. In the present study, we aimed to investigate the effects of vortioxetine on cognitive performance in a transgenic mouse model of Alzheimer's disease (AD).

METHODS

We administered vortioxetine (10 mg/kg, i.p., every day, for approximately 6 weeks), which acts on multiple 5-serotonin (5-HT) receptors, to 3.5-month-old 5×FAD mice. Subsequently, we used the open field (OF) test to detect anxiety-like behavior in the mice. The novel object recognition (NOR) test and Morris water maze (MWM) were used to assess the cognitive states of the 5×FAD mice. We also measured the levels of insoluble amyloid plaques and soluble β-amyloid (Aβ) plaques. Finally, we explored the expression levels of postsynaptic density protein 95 (PSD95), synaptophysin (SYP), and synaptotagmin-1 (SYT1) in the hippocampus of the mice.

RESULTS

The administration of vortioxetine effectively reversed the reduction in anxiety-type behaviors in 5×FAD mice and improved the impairment in recognition memory and spatial reference memory. However, we did not find that vortioxetine decreased or delayed the formation of amyloid plaques or Aβ. Interestingly, we found a significant increase in the expression levels of PSD95, SYP, and SYT1 in the 5×FAD mice after vortioxetine treatment compared with the control group.

CONCLUSION

These results demonstrate that vortioxetine may improve cognitive impairment in 5×FAD mice. The role in cognitive improvement may be related to the beneficial effects of vortioxetine on synaptic function.

Effect of repetitive transcranial magnetic stimulation (rTMS) treatment of major depressive disorder (MDD) on cognitive control

BACKGROUND

Major Depressive Disorder (MDD) is commonly accompanied by cognitive control dysfunction that may persist after remission of clinical symptoms with antidepressant medication treatment. Repetitive Transcranial Magnetic Stimulation (rTMS) is an effective treatment alternative for medication-resistant MDD. In this study, we investigated whether rTMS treatment had a beneficial effect not only on depressive symptoms, but on also cognitive control dysfunction.

METHODS

77 subjects with MDD received a 30-session treatment course of 10 Hz rTMS administered at the left dorsolateral prefrontal cortex (DLPFC). Treatment efficacy was assessed using the Inventory of Depressive Symptomatology Self-Rated (IDS-SR) before and after treatment, with clinical response defined as 50% or greater decrease in the IDS-SR score at treatment 30. Cognitive control function was assessed before and after treatment using the Stroop word-color interference task. We examined changes in Stroop accuracy and reaction time for congruent and incongruent trials, as well as in relation to changes in depressive symptoms.

RESULTS

Performance accuracy improved particularly for the rTMS responders in the incongruent condition, with older subjects benefitting most from the rTMS treatment. Improvement in reaction times was positively associated with clinical improvement, especially in the incongruent condition.

LIMITATIONS

We used a single cognitive task in a naturalistic setting without control for individual rTMS treatment parameters or concomitant medication.

CONCLUSIONS

Overall, these results indicate that rTMS treatment for MDD has beneficial effects on psychomotor speed and cognitive control. Future studies should extend these findings to larger patient populations and other cognitive domains.

The influence of ketamine's repeated treatment on brain topology does not suggest an antidepressant efficacy

As ketamine is increasingly used as an effective antidepressant with rapid action, sustaining its short-lived efficacy over a longer period of time using a schedule of repeated injections appears as an option. An open question is whether repeated and single administrations would affect convergent neurocircuits. We used a combination of one of the most robust animal models of depression with high-field neuroimaging to perform a whole-brain delineation of functional mechanisms underlying ketamine's effects. Rats from two genetic strains, depressive-like and resilient, received seven treatments of 10 mg/kg S-ketamine (N = 14 depressive-like, N = 11 resilient) or placebo (N = 12 depressive-like, N = 10 resilient) and underwent resting-state functional magnetic resonance imaging. Using graph theoretical models of brain networks, we compared effects of repeated ketamine with those of single administration from a separate dataset of our previous study. Compared to single treatment, repeated ketamine evoked strain-specific brain network randomization, resembling characteristics of the depressive-like strain and patients. Several affected regions belonged to the auditory, visual, and motor circuitry, hinting at possible cumulative side effects. Finally, when compared to saline, repeated ketamine affected only a few local topological properties and had no effects on global properties. In combination with the lack of clear differences compared to placebo, our findings point toward an inefficacy of ketamine's long-term administration on brain topology, making questionable the postulated effect of repeated administration and being consistent with the recently reported absence of repeated ketamine's antidepressant efficacy in several placebo-controlled studies.

BDNF-TrkB pathway mediates antidepressant-like roles of H2 S in diabetic rats via promoting hippocampal autophagy

Hydrogen sulfide (H₂ S) plays antidepressant-like roles in diabetic rats. However, the underlying mechanisms remain unclear. Brain-derived neurotropic factor (BDNF), a neurotrophic factor, plays important regulatory roles in depression by its high-affinity tropomysin-related kinase B (TrkB) receptor. Autophagy also is implicated in modulation of depression. Previous work confirmed the modulatory roles of H₂ S in BDNF protein expression and autophagy. Thus, in this study, we explored whether the BDNF-TrkB pathway mediates the antidepressant-like effects of H₂ S in diabetic rats and whether this process is achieved via promoting hippocampal autophagy. We demonstrated that H₂ S upregulated the expressions of BDNF and p-TrkB proteins in the hippocampus of streptozotocin (STZ)-induced diabetic rats. K252a (an inhibitor of BDNF-TrkB pathway) reversed the antidepressant-like roles of H₂ S, as evidenced by the tail suspension, forced swimming, novelty suppressed feeding, and elevated plus-maze tests. Furthermore, K252a abolished H₂ S-promoted hippocampal autophagy in diabetic rats, as evidenced by a decrease in the number of autolysosome, downregulation of Beclin-1 (a regulator of autophagy in the early stage of the formation of autophagosomal membranes and its level is positively correlated with autophagic activity) expression, and upregulation of P62 (a substrate of autophagic degradation and its level is inversely correlated with autophagic activity) expression, in the hippocampus of rats co-treated with NaHS and STZ. Taken together, these data indicated that the BDNF-TrkB pathway mediates the antidepressant-like roles of H₂ S in diabetic rats by enhancing hippocampal autophagy.

Diverse cognitive impairment after spinal cord injury is associated with orthostatic hypotension symptom burden

This study: 1) compared cognitive functioning between individuals with chronic (>1 year) spinal cord injury (SCI) and non-injured controls and, 2) assessed associations between symptoms of autonomic dysreflexia and orthostatic hypotension with cognitive functioning in SCI participants with a history of unstable blood pressure (BP). Thirty-two individuals with SCI (C4-L2, American Spinal Injury Association Impairment Scale A-D) and thirty age, sex-matched non-injured controls participated in this study. Participants completed a motor-free neuropsychological test battery assessing 1) memory, 2) attention/concentration/psychomotor speed and, 3) executive function. Nineteen participants with SCI who had injuries ≥T6 and a history of unstable BP also completed the Autonomic Dysfunction Following Spinal Cord Injury (ADFSCI) questionnaire. Cognitive function was significantly lower in people with SCI across measures of memory and executive function compared to non-injured controls. Significant, moderate-to-large associations were observed between cumulative (frequency x severity) orthostatic hypotension and total BP instability symptoms scores, with measures of attention/concentration/psychomotor speed and executive function. These data demonstrate a 10 - 65% reduced performance across specific realms of cognitive functioning in individuals with SCI relative to non-injured controls. Furthermore, cumulative subjective scores for symptoms of unstable BP were associated with diverse cognitive deficits. These findings, in individuals without co-occurring traumatic brain injury, imply cardiovascular dysregulation plays a role in cognitive deficits observed in this population.

Differences between ketamine's short-term and long-term effects on brain circuitry in depression

Ketamine acts as a rapid clinical antidepressant at 25 min after injection with effects sustained for 7 days. As dissociative effects emerging acutely after injection are not entirely discernible from therapeutic action, we aimed to dissect the differences between short-term and long-term response to ketamine to elucidate potential imaging biomarkers of ketamine's antidepressant effect. We used a genetical model of depression, in which we bred depressed negative cognitive state (NC) and non-depressed positive cognitive state (PC) rat strains. Four parallel rat groups underwent stress-escape testing and a week later received either S-ketamine (12 NC, 13 PC) or saline (12 NC, 12 PC). We acquired resting-state functional magnetic resonance imaging time series before injection and at 30 min and 48 h after injection. Graph analysis was used to calculate brain network properties. We identified ketamine's distinct action over time in a qualitative manner. The rapid response entailed robust and strain-independent topological modifications in cognitive, sensory, emotion, and reward-related circuitry, including regions that exhibited correlation of connectivity metrics with depressive behavior, and which could explain ketamine's dissociative and antidepressant properties. At 48 h ketamine had mainly strain-specific action normalizing habenula, midline thalamus, and hippocampal connectivity measures in depressed rats. As these nodes mediate cognitive flexibility impaired in depression, action within this circuitry presumably reflects ketamine's procognitive effects induced only in depressed patients. This finding is especially valid, as our model represents cognitive aspects of depression. These empirically defined circuits explain ketamine's distinct action over time and might serve as translational imaging correlates of antidepressant response in preclinical testing.

Fluoxetine and Vortioxetine Reverse Depressive-Like Phenotype and Memory Deficits Induced by Aβ1-42 Oligomers in Mice: A Key Role of Transforming Growth Factor-β1

Depression is a risk factor for the development of Alzheimer’s disease (AD), and the presence of depressive symptoms significantly increases the conversion of mild cognitive impairment (MCI) into AD. A long-term treatment with antidepressants reduces the risk to develop AD, and different second-generation antidepressants such as selective serotonin reuptake inhibitors (SSRIs) are currently being studied for their neuroprotective properties in AD. In the present work, the SSRI fluoxetine and the new multimodal antidepressant vortioxetine were tested for their ability to prevent memory deficits and depressive-like phenotype induced by intracerebroventricular injection of amyloid-β (1-42) (Aβ_1-42) oligomers in 2-month-old C57BL/6 mice. Starting from 7 days before Aβ injection, fluoxetine (10 mg/kg) and vortioxetine (5 and 10 mg/kg) were intraperitoneally injected daily for 24 days. Chronic treatment with fluoxetine and vortioxetine (both at the dose of 10 mg/kg) was able to rescue the loss of memory assessed 14 days after Aβ injection by the passive avoidance task and the object recognition test. Both antidepressants reversed the increase in immobility time detected 19 days after Aβ injection by forced swim test. Vortioxetine exerted significant antidepressant effects also at the dose of 5 mg/kg. A significant deficit of transforming growth factor-β1 (TGF-β1), paralleling memory deficits and depressive-like phenotype, was found in the hippocampus of Aβ-injected mice in combination with a significant reduction of the synaptic proteins synaptophysin and PSD-95. Fluoxetine and vortioxetine completely rescued hippocampal TGF-β1 levels in Aβ-injected mice as well as synaptophysin and PSD-95 levels. This is the first evidence that a chronic treatment with fluoxetine or vortioxetine can prevent both cognitive deficits and depressive-like phenotype in a non-transgenic animal model of AD with a key contribution of TGF-β1.

Results of a real-world study on vortioxetine in patients with major depressive disorder in South East Asia (REVIDA)

OBJECTIVE

The REVIDA study aimed to assess the evolution of major depression symptoms in South East Asian (SEA) patients treated with vortioxetine for major depression in real-world clinical practice.

METHODS

This non-interventional study was conducted from August 2016 to April 2017. A total of 138 patients (aged 18-65 years) with an active episode of major depression were recruited from Malaysia, Philippines, Singapore and Thailand. Vortioxetine was initiated on the first visit and patients were followed for 3 months. Depression severity was assessed using the PHQ-9 questionnaire (patient assessed) and CGI-S scale (physician assessed); cognitive function was assessed with the PDQ-D questionnaire; work productivity and activity impairment (WPAI) was assessed with the WPAI questionnaire.

RESULTS

At baseline, 89.9% of patients were moderately to severely depressed (PHQ-9 score ≥10). During the 3 month treatment period, mean ± SD PHQ-9 score decreased from 18.7 ± 5.7 to 5.0 ± 5.3, mean ± SD CGI-S score decreased from 4.4 ± 0.7 to 2.2 ± 1.1 and mean ± SD PDQ-D score decreased from 42.1 ± 18.8 to 13.4 ± 13.0. By Month 3, response and remission rates reached 80.8% and 59.0%, respectively. Work productivity loss decreased from 73.6% to 30.5%, while activity impairment decreased from 71.5% to 24.6%. Positive correlations were observed between PHQ-9, PDQ-D, and WPAI work productivity loss and activity impairment. By Month 3, 82.0% of patients were either not depressed or only mildly depressed (PHQ-9 score ≤9).

CONCLUSION

In real-world clinical settings, vortioxetine was effective in reducing depression severity and improving cognitive function and work productivity in SEA patients with major depression.

Pharmacological Characterization of H05, a Novel Serotonin and Noradrenaline Reuptake Inhibitor with Moderate 5-HT2A Antagonist Activity for the Treatment of Depression

Multitarget antidepressants selectively inhibiting monoaminergic transporters and 5-hydroxytryptamine (5-HT) 2A receptor have demonstrated higher efficacy and fewer side effects than selective serotonin reuptake inhibitors. In the present study, we synthesized a series of novel 3-(benzo[d][1,3]dioxol-4-yloxy)-3-arylpropyl amine derivatives, among which compound H05 was identified as a lead, exhibiting potent inhibitory effects on both serotonin (K_i = 4.81 nM) and norepinephrine (NE) (K_i = 6.72 nM) transporters and moderate 5-HT_2A antagonist activity (IC₅₀ = 60.37 nM). H05 was able to dose-dependently reduce the immobility duration in mouse forced swimming test and tail suspension test, with the minimal effective doses lower than those of duloxetine, and showed no stimulatory effect on locomotor activity. The administration of H05 (5, 10, and 20 mg/kg, by mouth) significantly shortened the immobility time of adrenocorticotropin-treated rats that serve as a model of treatment-resistant depression, whereas imipramine (30 mg/kg, by mouth) and duloxetine (30 mg/kg, by mouth) showed no obvious effects. Chronic treatment with H05 reversed the depressive-like behaviors in a rat model of chronic unpredictable mild stress and a mouse model of corticosterone-induced depression. Microdialysis analysis revealed that the administration of H05 at either 10 or 20 mg/kg increased the release of 5-HT and NE from the frontal cortex. The pharmacokinetic (PK) and brain penetration analyses suggest that H05 has favorable PK properties with good blood-brain penetration ability. Therefore, it can be concluded that H05, a novel serotonin and NE reuptake inhibitor with 5-HT_2A antagonist activity, possesses efficacious activity in the preclinical models of depression and treatment-resistant depression, and it may warrant further evaluation for clinical development.

Vortioxetine Treatment Reverses Subchronic PCP Treatment-Induced Cognitive Impairments: A Potential Role for Serotonin Receptor-Mediated Regulation of GABA Neurotransmission

Major depressive disorder (MDD) is associated with cognitive impairments that may contribute to poor functional outcomes. Clinical data suggests that the multimodal antidepressant vortioxetine attenuates some cognitive impairments in MDD patients, but the mechanistic basis for these improvements is unclear. One theory suggests that vortioxetine improves cognition by suppressing γ-amino butyric acid (GABA)ergic neurotransmission, thereby increasing glutamatergic activation. Vortioxetine’s effects on cognition, GABA and glutamate neurotransmission have been supported in separate experiments, but no empirical work has directly connected vortioxetine’s cognitive effects to those on GABA and glutamate neurotransmission. In this paper, we attempt to bridge this gap by evaluating vortioxetine’s effects in the subchronic PCP (subPCP) model, which induces impaired cognitive function and altered GABA and glutamate neurotransmission. We demonstrate that acute or subchronic vortioxetine treatment attenuated subPCP-induced deficits in attentional set shifting (AST) performance, and that the selective 5-HT₃ receptor antagonist ondansetron or the 5-HT reuptake inhibitor escitalopram could mimic this effect. Furthermore, acute vortioxetine treatment reversed subPCP-induced object recognition (OR) deficits in rats, while subchronic vortioxetine reversed subPCP-induced Object Recognition and object placement impairments in mice. Finally, subPCP treatment reduced GABA_B receptor expression in a manner that was insensitive to vortioxetine treatment, and subchronic vortioxetine treatment alone, but not in combination with subPCP, significantly increased GABA’s affinity for the GABA_A receptor. These data suggest that vortioxetine reverses cognitive impairments in a model associated with altered GABA and glutamate neurotransmission, further supporting the hypothesis that vortioxetine’s GABAergic and glutamatergic effects are relevant for cognitive function.

Cognitive dysfunction in major depressive disorder

PURPOSE OF REVIEW

The principal aim of this review is to highlight recent advances in our understanding of cognitive dysfunction in major depressive disorder (MDD). We review new assessment and treatment approaches, in which cognition and associated psychosocial dysfunction are considered primary outcomes.

RECENT FINDINGS

Current work suggests that cognitive dysfunction reduces occupational productivity, and interferes broadly with domains of day-to-day and social functioning. These findings imply that cognitive dysfunction interacts with emotional and social factors relevant to MDD. Recent advances in screening instruments enable standardized detection of cognitive symptoms in MDD. Clinical trials suggest that cognitive symptoms are suitable targets and primary outcomes of psychological and pharmacological treatments.

SUMMARY

A growing interest in cognitive dysfunction in MDD has improved our ability to assess and treat MDD. Future research will be strengthened by the use of consistent terminology, standardized cognitive screening, and treatments that target cognitive dysfunction in MDD. Integration of emotional and social treatment strategies may further advance clinical efficacy.

A Network Meta-Analysis Comparing Effects of Various Antidepressant Classes on the Digit Symbol Substitution Test (DSST) as a Measure of Cognitive Dysfunction in Patients with Major Depressive Disorder

BACKGROUND

Major depressive disorder is a common condition that often includes cognitive dysfunction. A systematic literature review of studies and a network meta-analysis were carried out to assess the relative effect of antidepressants on cognitive dysfunction in major depressive disorder.

METHODS

MEDLINE, Embase, Cochrane, CDSR, and PsychINFO databases; clinical trial registries; and relevant conference abstracts were searched for randomized controlled trials assessing the effects of antidepressants/placebo on cognition. A network meta-analysis comparing antidepressants was conducted using a random effects model.

RESULTS

The database search retrieved 11337 citations, of which 72 randomized controlled trials from 103 publications met the inclusion criteria. The review identified 86 cognitive tests assessing the effect of antidepressants on cognitive functioning. However, the Digit Symbol Substitution Test, which targets multiple domains of cognition and is recognized as being sensitive to change, was the only test that was used across 12 of the included randomized controlled trials and that allowed the construction of a stable network suitable for the network meta-analysis. The interventions assessed included selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and other non-selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitors. The network meta-analysis using the Digit Symbol Substitution Test showed that vortioxetine was the only antidepressant that improved cognitive dysfunction on the Digit Symbol Substitution Test vs placebo {standardized mean difference: 0.325 (95% CI = 0.120; 0.529, P=.009}. Compared with other antidepressants, vortioxetine was statistically more efficacious on the Digit Symbol Substitution Test vs escitalopram, nortriptyline, and the selective serotonin reuptake inhibitor and tricyclic antidepressant classes.

CONCLUSIONS

This study highlighted the large variability in measures used to assess cognitive functioning. The findings on the Digit Symbol Substitution Test indicate differential effects of various antidepressants on improving cognitive function in patients with major depressive disorder.

A longitudinal study of cognitive trajectories in Mexican Americans age 75 and older

OBJECTIVE

To identify distinct trajectories for global cognition, memory, and non-memory domains among Mexican American adults 75 years of age and older.

METHODS

The final sample included 1336 participants of the Hispanic Established Population for the Epidemiologic Study of the Elderly observed during four Waves from 2004-2005 to 2012-2013. Latent class growth curve models were used to identify distinct trajectories for global cognition, memory, and non-memory.

RESULTS

Three trajectory classes were identified for global cognition, memory, and non-memory domains. Nearly 31% of the final sample maintained high global cognition (persistent high), 52.6% experienced slight decline (decline but high), and 15% experienced severe decline in global cognition (decline to low). Over 95% of participants classified in the decline to low trajectory for global cognition were also classified as decline to low for memory and non-memory. This high level of consistency for memory and non-memory domains was observed for the decline but high (97.0%) and persistent high (93.7%) trajectory classes.

CONCLUSIONS

These results indicate that the majority of Mexican American older adults will experience varying degrees of cognitive decline. However, a substantial proportion of older Mexican Americans are able to maintain high cognitive functioning into advanced age despite the high prevalence of risk factors for cognitive decline in this population. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of agomelatine on memory deficits and hippocampal gene expression induced by chronic social defeat stress in mice

Chronic stress is known to induce not only anxiety and depressive-like phenotypes in mice but also cognitive impairments, for which the action of classical antidepressant compounds remains unsatisfactory. In this context, we investigated the effects of chronic social defeat stress (CSDS) on anxiety-, social- and cognitive-related behaviors, as well as hippocampal Bdnf, synaptic plasticity markers (PSD-95, Synaptophysin, Spinophilin, Synapsin I and MAP-2), and epigenetic modifying enzymes (MYST2, HDAC2, HDAC6, MLL3, KDM5B, DNMT3B, GADD45B) gene expression in C57BL/6J mice. CSDS for 10 days provoked long-lasting anxious-like phenotype in the open field and episodic memory deficits in the novel object recognition test. While total Bdnf mRNA level was unchanged, Bdnf exon IV, MAP-2, HDAC2, HDAC6 and MLL3 gene expression was significantly decreased in the CSDS mouse hippocampus. In CSDS mice treated 3 weeks with 50 mg/kg/d agomelatine, an antidepressant with melatonergic receptor agonist and 5-HT_2C receptor antagonist properties, the anxious-like phenotype was not reversed, but the treatment successfully prevented the cognitive impairments and hippocampal gene expression modifications. Altogether, these data evidenced that, in mice, agomelatine was effective in alleviating stress-induced altered cognitive functions, possibly through a mechanism involving BDNF signaling, synaptic plasticity and epigenetic remodeling.

Crystal Structures, X-Ray Photoelectron Spectroscopy, Thermodynamic Stabilities, and Improved Solubilities of 2-Hydrochloride Salts of Vortioxetine

Two vortioxetine (VOT) salts with hydrochloride (VOT-HCl and VOT-0.5HCl) were prepared and structurally characterized. VOT-HCl features 1-dimensional P/M helical chains through N-H···Cl hydrogen bond interactions, whereas VOT-0.5HCl possesses a 1-dimensional zigzag structure in which 2 VOT molecules share a single proton through N···H⁺···N interactions. VOT-HCl converts into the monohydrate VOT-HCl·H₂O after dissolution in water, whereas VOT-0.5HCl remains stable. The N 1s X-ray photoelectron spectroscopy analysis shows a characteristic binding energy peak at approximately 398.0 eV for VOT. The shift to high energy occurs at 400.3 eV for VOT-HCl and VOT-HBr, and at 399.7 eV for VOT-0.5HCl, which supports the salt formation by the degree of proton transfer and is confirmed by single-crystal X-ray analyses. The apparent equilibrium solubilities of VOT in water are significantly improved to 2.90 mg/mL (approximately a 32.0-fold increase over that of the free base) for VOT-HCl and to 0.59 mg/mL (approximately a 5.7-fold increase over that of the free base) for VOT-0.5HCl at 25°C.

Distinct Antidepressant-Like and Cognitive Effects of Antidepressants with Different Mechanisms of Action in Middle-Aged Female Mice

BACKGROUND

Cognitive dysfunction is among the key symptoms of major depressive disorder and can be affected by antidepressants. Cognitive decline also occurs in normal aging. The effects of different antidepressants on affective and cognitive domains in older subjects are seldom assessed simultaneously.

METHODS

Healthy middle-aged female mice received vehicle or antidepressant (vortioxetine, vilazodone, duloxetine, or fluoxetine) at therapeutic doses. After 1 month treatment, mice were accessed for visuospatial memory and depression-like behavior. A separate cohort of mice received 3 months of treatment and was test for recognition memory and depression-like behavior.

RESULTS

After 1 month treatment, vortioxetine improved visuospatial memory and reduced depression-like behavior. Vilazodone reduced depression-like behavior. Duloxetine and fluoxetine were ineffective in both tests. After 3 months treatment, vortioxetine reduced depression-like behavior without affecting recognition memory, while fluoxetine impaired recognition memory. Duloxetine and vilazodone had no effect in both tests.

CONCLUSION

Different antidepressants have distinct effects in middle-aged female mice.

Chronic vortioxetine treatment in rodents modulates gene expression of neurodevelopmental and plasticity markers

The multimodal antidepressant vortioxetine displays an antidepressant profile distinct from those of conventional selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) and possesses cognitive-enhancing properties in preclinical and clinical studies. Recent studies have begun to investigate molecular mechanisms that may differentiate vortioxetine from other antidepressants. Acute studies in adult rats and chronic studies in a middle-aged mouse model reveal upregulation of several markers that play a central role in synaptic plasticity. However, the effect of chronic vortioxetine treatment on expression of neuroplasticity and neurodevelopmental biomarkers in naïve rats has not been evaluated. In the present study, we demonstrate that vortioxetine at a range of doses regulates expression of genes associated with plasticity in the frontal cortex, hippocampus, region encompassing the amygdala, as well as in blood, and displays similar effects relative to the SSRI fluoxetine in adult naïve rats. These genes encode immediate early genes (IEGs), translational regulators, and the neurodevelopmental marker Sema4g. Similar findings detected in brain regions and in blood provide a potential translational impact, and vortioxetine appears to consistently regulate signaling in these networks of neuroplasticity and developmental markers.

Discovery of N-Alkyl Catecholamides as Selective Phosphodiesterase-4 Inhibitors with Anti-neuroinflammation Potential Exhibiting Antidepressant-like Effects at Non-emetic Doses

Depression involving neuroinflammation is one of the most common disabling and life-threatening psychiatric disorders. Phosphodiesterase 4 (PDE4) inhibitors produce potent antidepressant-like and cognition-enhancing effects. However, their clinical utility is limited by their major side effect of emesis. To obtain more selective PDE4 inhibitors with antidepressant and anti-neuroinflammation potential and less emesis, we designed and synthesized a series of N-alkyl catecholamides by modifying the 4-methoxybenzyl group of our hit compound, FCPE07, with an alkyl side chain. Among these compounds, 10 compounds displayed submicromolar IC₅₀ values in the mid- to low-nanomolar range. Moreover, 4-difluoromethoxybenzamides 10g and 10j, bearing isopropyl groups, exhibited the highest PDE4 inhibitory activities, with IC₅₀ values in the low-nanomolar range and with higher selectivities for PDE4 (approximately 5000-fold and 2100-fold over other PDEs, respectively). Furthermore, compound 10j displayed anti-neuroinflammation potential, promising antidepressant-like effects, and a zero incidence rate of emesis at 0.8 mg/kg within 180 min.

Systematic review of randomized controlled trials of candidate treatments for cognitive impairment in depression and methodological challenges in the field

Cognitive impairment is a core feature of Major Depressive Disorder (MDD) but treatments targeting cognition are lacking. Numerous pre-clinical and clinical studies have investigated potential cognition treatments, but overall the evidence is conflicting. We conducted a systematic search following the PRISMA guidelines on PubMed and PsychInfo to evaluate the extant evidence and methodological challenges in randomized controlled trials (RCTs) of biological, psychological and behavioural candidate treatments targeting cognition in MDD. Inclusion criteria were RCTs with a placebo control assessing potential pro-cognitive effects of candidate treatments in MDD. Two independent authors reviewed the studies and assessed their risk of bias with the Cochrane Collaboration׳s Risk of Bias tool. Twenty-eight eligible studies (24 biological and four psychological or behavioural studies) were identified. Cognition was the primary treatment target in ten (36%) trials and an additional treatment outcome together with mood symptoms in 18 (64%) trials. The risk of bias was high or unclear in 93% of trials due to potential selective outcome reporting or 'pseudospecificity' (unspecific cognitive improvement due to reduced depression severity), and/or insufficient details on how the allocation sequence was generated or how blinding was maintained. Several promising treatments were identified, including vortioxetine, erythropoietin, transcranial direct current stimulation and cognitive remediation. However, several common methodological challenges may impede advances in the field. In particular, future trials should select one cognitive composite score as primary outcome, screen for cognitive impairment before inclusion of participants and address 'pseudospecificity' issues. Together, these strategies may improve the success of future cognition trials in MDD.

Differential interaction with the serotonin system by S-ketamine, vortioxetine, and fluoxetine in a genetic rat model of depression

RATIONALE

The mechanisms mediating ketamine's antidepressant effect have only been partly resolved. Recent preclinical reports implicate serotonin (5-hydroxytryptamine; 5-HT) in the antidepressant-like action of ketamine. Vortioxetine is a multimodal-acting antidepressant that is hypothesized to exert its therapeutic activity through 5-HT reuptake inhibition and modulation of several 5-HT receptors.

OBJECTIVES

The objective of this study was to evaluate the therapeutic-like profiles of S-ketamine, vortioxetine, and the serotonin reuptake inhibitor fluoxetine in response to manipulation of 5-HT tone.

METHOD

Flinders Sensitive Line (FSL) rats, a genetic model of depression, were depleted of 5-HT by repeated administration of 4-chloro-DL-phenylalanine methyl ester HCl (pCPA). Using pCPA-pretreated and control FSL rats, we investigated the acute and sustained effects of S-ketamine (15 mg/kg), fluoxetine (10 mg/kg), or vortioxetine (10 mg/kg) on recognition memory and depression-like behavior in the object recognition task (ORT) and forced swim test (FST), respectively.

RESULTS

The behavioral phenotype of FSL rats was unaffected by 5-HT depletion. Vortioxetine, but not fluoxetine or S-ketamine, acutely ameliorated the memory deficits of FSL rats in the ORT irrespective of 5-HT tone. No sustained effects were observed in the ORT. In the FST, all three drugs demonstrated acute antidepressant-like activity but only S-ketamine had sustained effects. Unlike vortioxetine, the antidepressant-like responses of fluoxetine and S-ketamine were abolished by 5-HT depletion.

CONCLUSIONS

These observations suggest that the acute and sustained antidepressant-like effects of S-ketamine depend on endogenous stimulation of 5-HT receptors. In contrast, the acute therapeutic-like effects of vortioxetine on memory and depression-like behavior may be mediated by direct activity at 5-HT receptors.

The Effects of Vortioxetine on Cognitive Function in Patients with Major Depressive Disorder: A Meta-Analysis of Three Randomized Controlled Trials

BACKGROUND

Management of cognitive deficits in Major Depressive Disorder (MDD) remains an important unmet need. This meta-analysis evaluated the effects of vortioxetine on cognition in patients with MDD.

METHODS

Random effects meta-analysis was applied to three randomized, double-blind, placebo-controlled 8-week trials of vortioxetine (5-20mg/day) in MDD, and separately to two duloxetine-referenced trials. The primary outcome measure was change in Digit Symbol Substitution Test (DSST) score. Standardized effect sizes (SES) versus placebo (Cohen's d ) were used as input. Path analysis was employed to determine the extent to which changes in DSST were mediated independently of a change in Montgomery-Åsberg Depression Rating Scale (MADRS) score. Meta-analysis was applied to MADRS-adjusted and -unadjusted SES values. Changes on additional cognitive tests were evaluated (source studies only).

RESULTS

Before adjustment for MADRS, vortioxetine separated from placebo on DSST score (SES 0.25-0.48; nominal p < 0.05) in all individual trials, and statistically improved DSST performance versus placebo in meta-analyses of the three trials (SES = 0.35; p < 0.0001) and two duloxetine-referenced trials (SES = 0.26; p = 0.001). After adjustment for MADRS, vortioxetine maintained DSST improvement in one individual trial ( p = 0.001) and separation from placebo was maintained in meta-analyses of all three trials (SES = 0.24; p < 0.0001) and both duloxetine-referenced trials (SES 0.19; p = 0.01). Change in DSST with duloxetine failed to separate from placebo in individual trials and both meta-analyses. Change in DSST statistically favored vortioxetine versus duloxetine after MADRS adjustment (SES = 0.16; p = 0.04).

CONCLUSIONS

Vortioxetine, but not duloxetine, significantly improved cognition, independent of depressive symptoms. Vortioxetine represents an important treatment for MDD-related cognitive dysfunction.

The impact of metabotropic glutamate receptors into active neurodegenerative processes: A "dark side" in the development of new symptomatic treatments for neurologic and psychiatric disorders

Metabotropic glutamate (mGlu) receptor ligands are under clinical development for the treatment of CNS disorders with high social and economic burden, such as schizophrenia, major depressive disorder (MDD), and Parkinson's disease (PD), and are promising drug candidates for the treatment of Alzheimer's disease (AD). So far, clinical studies have shown symptomatic effects of mGlu receptor ligands, but it is unknown whether these drugs act as disease modifiers or, at the opposite end, they accelerate disease progression by enhancing neurodegeneration. This is a fundamental issue in the treatment of PD and AD, and is also an emerging theme in the treatment of schizophrenia and MDD, in which neurodegeneration is also present and contribute to disease progression. Moving from in vitro data and preclinical studies, we discuss the potential impact of drugs targeting mGlu2, mGlu3, mGlu4 and mGlu5 receptor ligands on active neurodegeneration associated with AD, PD, schizophrenia, and MDD. We wish to highlight that our final comments on the best drug candidates are not influenced by commercial interests or by previous or ongoing collaborations with drug companies. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.