The promise of ketamine for treatment-resistant depression: current evidence and future directions

Deciphering the dual role of N-methyl-D-Aspartate receptor in postoperative cognitive dysfunction: A comprehensive review

Postoperative cognitive dysfunction (POCD) is a common complication following surgery, adversely impacting patients' recovery, increasing the risk of negative outcomes, prolonged hospitalization, and higher mortality rates. The N-methyl-D-aspartate (NMDA) receptor, crucial for learning, memory, and synaptic plasticity, plays a significant role in the development of POCD. Various perioperative factors, including age and anesthetic use, can reduce NMDA receptor function, while surgical stress, inflammation, and pain may lead to its excessive activation. This review consolidates preclinical and clinical research to explore the intricate relationship between perioperative factors affecting NMDA receptor functionality and the onset of POCD. It discusses the influence of aging, anesthetic administration, perioperative injury, pain, and inflammation on the NMDA receptor-related pathophysiology of POCD. The comprehensive analysis presented aims to identify effective treatment targets for POCD, contributing to the improvement of patient outcomes post-surgery.

Promising new pharmacological targets for depression: The search for efficacy

Pharmacological treatment of major depressive disorder (MDD) still relies on the use of serotonergic drugs, despite their limited efficacy. A few mechanistically new drugs have been developed in recent years, but many fail in clinical trials. Several hypotheses have been proposed to explain MDD pathophysiology, indicating that physiological processes such as neuroplasticity, circadian rhythms, and metabolism are potential targets. Here, we review the current state of pharmacological treatments for MDD, as well as the preclinical and clinical evidence for an antidepressant effect of molecules that target non-serotonergic systems. We offer some insights into the challenges facing the development of new antidepressant drugs, and the prospect of finding more effectiveness for each target discussed.

Efficacy and Safety of Flexibly Dosed Esketamine Nasal Spray Plus a Newly Initiated Oral Antidepressant in Adult Patients with Treatment-Resistant Depression: A Randomized, Double-Blind, Multicenter, Active-Controlled Study Conducted in China and USA

Purpose

This Phase 3, multicenter study (NCT03434041) was conducted in primarily Chinese patients with treatment-resistant depression (TRD) to support the registration of esketamine nasal spray in China.

Patients and Methods

This randomized, double-blind, active-controlled study was conducted in China and the United States (US) in patients with TRD (single or recurrent episode). Eligible patients were randomized 1:1 to receive intranasal esketamine or matching placebo, each in conjunction with a newly initiated oral antidepressant (AD; duloxetine, escitalopram, sertraline, and venlafaxine extended release) (ie, esketamine plus AD or AD plus placebo). The primary endpoint, change from baseline in Montgomery-Åsberg Depression Rating Scale (MADRS) total score at Day 28, was analyzed using a mixed-effects model for repeated measures. Secondary endpoints including safety were also evaluated.

Results

Of 252 randomized patients (China, 224; US, 28), 214 completed the double-blind treatment phase. The difference between treatment groups at Day 28 was not statistically significant (difference in least-square means [95% CI]: -2.0 [-4.64, 0.55]; 2-sided p = 0.123). However, esketamine plus AD demonstrated a clinically meaningful treatment difference compared with AD plus placebo in MADRS total score at 24 hours after first dose for the study overall population and China sub-population (difference in least-square mean [95% CI]: -3.3 [-5.33, -1.33] and -2.6 [-4.64, -0.60], respectively). No new safety signals were observed.

Conclusion

Esketamine plus AD was not statistically superior to AD plus placebo in improving depressive symptoms in TRD patients at Day 28. Rapid reduction in depressive symptoms within 24 hours was observed for TRD patients treated with esketamine plus AD in the overall population and China sub-population. Safety was consistent with the established safety profile of esketamine.

Emotion Context Insensitivity is generalized in individuals with major depressive disorder but not in those with subclinical depression

BACKGROUND

Depressed individuals experience deficits in emotional reactivity. One well-established theory is the Emotion Context Insensitivity (ECI) theory. To better understand impairments in emotional reactivity, we investigated whether the ECI theory is applicable to anticipatory, consummatory, and remembered affect, in both clinical and subclinical depression.

METHODS

Participants were divided into four groups: Major Depressive Disorder Group (MDD, N = 60), Control Group for MDD (Control_MDD, N = 50), Subclinical Depression Group (SD, N = 56), and Control Group for SD (Control_SD, N = 56). The Hamilton Depression Rating Scale and the Beck Depression Inventory were used to assess the severity of depression and anhedonia symptoms. The Monetary Incentive Delay Task evaluated participants' affective responses towards monetary stimuli.

RESULTS

The MDD group was more insensitive to both monetary reward and loss across most types of affect than was the control group. Compared with the controls, the SD group exhibited lower reactivity in anticipatory positive affect but enhanced reactivity in consummatory positive, anticipatory, and remembered negative affect.

LIMITATIONS

Emotional affect was evaluated by subjective ratings, which may lack objectivity. Additionally, laboratory settings and monetary rewards used in this study may cause the results less generalized to daily life and to other types of rewards.

CONCLUSION

The pattern of emotional reactivity in the MDD group was partly consistent with the ECI theory, whereas the SD group showed greater arousal and instability of emotional reactions. These different patterns could facilitate the understanding of emotional reactivity and develop further treatments across the course of depression.

Brain Changes Associated With Long-Term Ketamine Abuse, A Systematic Review

Recently, the abuse of ketamine has soared. Therefore, it is of great importance to study its potential risks. The effects of prolonged ketamine on the brain can be observationally studied in chronic recreational users. We performed a systematic review of studies reporting functional and structural brain changes after repeated ketamine abuse. We searched the following electronic databases: Medline, Embase and PsycINFO We screened 11,438 records and 16 met inclusion criteria, totaling 440 chronic recreational ketamine users (2–9.7 years; mean use 2.4 g/day), 259 drug-free controls and 44 poly-drug controls. Long-term recreational ketamine use was associated with lower gray matter volume and less white matter integrity, lower functional thalamocortical and corticocortical connectivity. The observed differences in both structural and functional neuroanatomy between ketamine users and controls may explain some of its long-term cognitive and psychiatric side effects, such as memory impairment and executive functioning. Given the effect that long-term ketamine exposure may yield, an effort should be made to curb its abuse.

Anhedonia and Suicide

Suicide is a leading cause of death, and presently, there is no definitive clinical indicator of future suicide behaviors. Anhedonia, a transdiagnostic symptom reflecting diminished ability to experience pleasure, has recently emerged as a risk factor for suicidal thoughts and behaviors (STBs). This overview, therefore, has the following aims. First, prior research relating anhedonia to STBs will be reviewed, with a particular focus on clarifying whether anhedonia is more closely associated with suicidal thoughts versus behaviors. Second, the National Institute of Mental Health's Research Domain Criteria Positive Valence Systems provide a useful heuristic to probe anhedonia across different units of analysis, including clinical symptoms, behaviors, neural mechanisms, and molecular targets. Accordingly, anhedonia-related constructs linked to STBs will be detailed as well as promising next steps for future research. Third, although anhedonia is not directly addressed in leading suicide theories, this review will provide potential inroads to explore anhedonia within diathesis-stress and interpersonal suicide frameworks. Last, novel approaches to treat anhedonia as a means of reducing STBs will be examined.

The effect of physical activity on anhedonia in individuals with depressive symptoms

The therapeutic effect of antidepressants has been demonstrated for anhedonia in patients with depression. However, antidepressants may cause side-effects, such as cardiovascular dysfunction. Although physical activity has minor side-effects, it may serve as an alternative for improving anhedonia and depression. We sought to investigate whether physical activity reduces the level of anhedonia in individuals with depression. Fifty-six university students with moderate depressive symptoms (Beck Depression Inventory total score > 16) were divided into three training groups: the Running Group (RG, n = 19), the Stretching Group (SG, n = 19), and the Control Group (n = 18). We employed the Monetary Incentive Delay (MID) task and the Temporal Experience of Pleasure Scale (TEPS) to evaluate hedonic capacity. All participants in the RG and SG received 8 weeks of jogging and stretching training, respectively. The RG experienced an increase in the level of arousal during anticipation of a future reward and recalled less negativity towards the loss condition. The SG exhibited enhanced scores on the Anticipatory and Consummatory Pleasure subscales of the TEPS after training. Moreover, in the RG, greater improvements in anticipatory arousal ratings for pleasure and remembered valence ratings for negative affect were associated with longer training duration, lower maximum heart rate, and higher consumed calories during training. To conclude, physical activity is effective in improving anticipatory anhedonia in individuals with depressive symptoms.

Anhedonia as a central factor in depression: Neural mechanisms revealed from preclinical to clinical evidence

Anhedonia is one of the core symptoms of major depressive disorder (MDD), which is often inadequately treated by traditional antidepressants. The modern framework of anhedonia extends the definition from impaired consummatory pleasure or interest in rewards to a broad spectrum of deficits that impact functions such as reward anticipation, approach motivation, effort expenditure, reward valuation, expectation, and reward-cue association learning. Substantial preclinical and clinical research has explored the neural basis of reward deficits in the context of depression, and has implicated mesocorticolimbic reward circuitry comprising the nucleus accumbens, ventral pallidum, ventral tegmental area, amygdala, hippocampus, anterior cingulate, insula, orbitofrontal cortex, and other prefrontal cortex regions. Dopamine modulates several reward facets including anticipation, motivation, effort, and learning. As well, serotonin, norepinephrine, opioids, glutamate, Gamma aminobutyric acid (GABA), and acetylcholine are also involved in anhedonia, and medications targeting these systems may also potentially normalize reward processing in depression. Unfortunately, whereas reward anticipation and reward outcome are extensively explored by both preclinical and clinical studies, translational gaps remain in reward motivation, effort, valuation, and learning, where clinical neuroimaging studies are in the early stages. This review aims to synthesize the neurobiological mechanisms underlying anhedonia in MDD uncovered by preclinical and clinical research. The translational difficulties in studying the neural basis of reward are also discussed.

The effect of intravenous ketamine on cognitive functions in adults with treatment-resistant major depressive or bipolar disorders: Results from the Canadian rapid treatment center of excellence (CRTCE)

Ketamine may exert pro-cognitive effects on select measures of cognition in adults with mood disorders. We evaluated the effectiveness of intravenous (IV) ketamine on cognition in 68 adult outpatients with treatment-resistant depression (TRD) at the Canadian Rapid Treatment Center of Excellence between July 3, 2018 and April 16, 2020 (NCT04209296). Eligibility criteria for the present retrospective study included: primary diagnosis of major depressive or bipolar disorder; currently depressed; and insufficient response to two or more prior treatments. Participants received four infusions of ketamine hydrochloride (0.5-0.75 mg/kg) over 1-2 weeks. We assessed objective and subjective measures of cognition before and after two infusions, i.e., Digit Symbol Substitution Test (DSST), Trail Making Test-B (TMT-B), Patient Deficits Questionnaire, 5-item (PDQ-5-D). Ketamine significantly improved DSST (effect size [ES]=0.60), TMT-B (ES=0.84), as well as PDQ-5-D scores (ES=0.63), indicative of a moderate-to-large effect size. Improvements in DSST and PDQ-5-D with ketamine were mediated by reductions in depressive symptoms, whereas improvements in TMT-B were independent of changes in depressive symptoms. Our results support the independent, rapid-onset, pro-cognitive effects with IV ketamine in adults with TRD. Larger, randomized, controlled trials with ketamine wherein cognition is the primary outcome measure in mood and non-mood disorder samples are warranted.

Transcranial magnetic stimulation as a translational biomarker for AMPA receptor modulation

TAK-653 is a novel α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-positive allosteric modulator being developed as a potential therapeutic for major depressive disorder (MDD). Currently, there are no translational biomarkers that evaluate physiological responses to the activation of glutamatergic brain circuits available. Here, we tested whether noninvasive neurostimulation, specifically single-pulse or paired-pulse motor cortex transcranial magnetic stimulation (spTMS and ppTMS, respectively), coupled with measures of evoked motor response captures the pharmacodynamic effects of TAK-653 in rats and healthy humans. In the rat study, five escalating TAK-653 doses (0.1-50 mg/kg) or vehicle were administered to 31 adult male rats, while measures of cortical excitability were obtained by spTMS coupled with mechanomyography. Twenty additional rats were used to measure brain and plasma TAK-653 concentrations. The human study was conducted in 24 healthy volunteers (23 males, 1 female) to assess the impact on cortical excitability of 0.5 and 6 mg TAK-653 compared with placebo, measured by spTMS and ppTMS coupled with electromyography in a double-blind crossover design. Plasma TAK-653 levels were also measured. TAK-653 increased both the mechanomyographic response to spTMS in rats and the amplitude of motor-evoked potentials in humans at doses yielding similar plasma concentrations. TAK-653 did not affect resting motor threshold or paired-pulse responses in humans. This is the first report of a translational functional biomarker for AMPA receptor potentiation and indicates that TMS may be a useful translational platform to assess the pharmacodynamic profile of glutamate receptor modulators.

Effect of neuropsychiatric medications on mitochondrial function: For better or for worse

Individuals with mitochondrial disease often present with psychopathological comorbidity, and mitochondrial dysfunction has been proposed as the underlying pathobiology in various psychiatric disorders. Several studies have suggested that medications used to treat neuropsychiatric disorders could directly influence mitochondrial function. This review provides a comprehensive overview of the effect of these medications on mitochondrial function. We collected preclinical information on six major groups of antidepressants and other neuropsychiatric medications and found that the majority of these medications either positively influenced mitochondrial function or showed mixed effects. Only amitriptyline, escitalopram, and haloperidol were identified as having exclusively adverse effects on mitochondrial function. In the absence of formal clinical trials, and until such trials are completed, the data from preclinical studies reported and discussed here could inform medication prescribing practices for individuals with psychopathology and impaired mitochondrial function in the underlying pathology.

Hippocampal volume, function, and related molecular activity in anorexia nervosa: A scoping review

INTRODUCTION

Anorexia nervosa (AN) is a serious and persistent eating disorder, characterized by severe dietary restriction and weight loss, with a third of patients developing a  severe-enduring form. The factors contributing to this progression are poorly understood, although there is evidence for impairments in neural structures such as the hippocampus, an area particularly affected by malnutrition and chronic stress.

AREAS COVERED

This study aimed to map the evidence for alterations in hippocampal volume, function, and related molecular activity in anorexia nervosa. PubMed, PsycINFO, and Web of Science were searched for studies related to hippocampal function and integrity using a range of methodologies, such as neuropsychological paradigms, structural and functional magnetic resonance imaging, and analysis of blood components.

EXPERT OPINION

Thirty-nine studies were included in this review. The majority were neuroimaging studies, which found hippocampus-specific volumetric and functional impairments. Neuropsychological studies showed evidence for a specific memory and learning impairments. There was some evidence for molecular abnormalities (e.g. cortisol), although these were few studies. Taken together, our review suggests that the hippocampus might be a particular region of interest when considering neurobiological approaches to understanding AN. These findings warrant further investigation and may lead to novel treatment approaches.

Copper and anti-anhedonic effect of ketamine in treatment-resistant depression

Treatment-resistant depression (TRD) remains one of the major psychiatric challenges worldwide. Search for non-monoaminergic agents, possibly effective in treatment of TRD is of prime importance. One of those agents is ketamine - a dissociative, anesthetic drug exhibiting a fast antidepressant action in patients with TRD. Concurrently, anhedonia appears to be significant symptom domain with far-reaching impact on course of treatment. There is data demonstrating that abnormal copper levels might be associated with symptoms of depression. As there is common denominator in ketamine and copper role in neurotransmission this paper is to explore the associations of blood copper levels and psychometric measures in patients with TRD in course of major depressive disorder (MDD) and bipolar disorder (BP), focusing on anhedonia measured with Snaith-Hamilton Pleasure Scale (SHAPS) score.

The neurophysiology of ketamine: an integrative review

The drug ketamine has been extensively studied due to its use in anaesthesia, as a model of psychosis and, most recently, its antidepressant properties. Understanding the physiology of ketamine is complex due to its rich pharmacology with multiple potential sites at clinically relevant doses. In this review of the neurophysiology of ketamine, we focus on the acute effects of ketamine in the resting brain. We ascend through spatial scales starting with a complete review of the pharmacology of ketamine and then cover its effects on in vitro and in vivo electrophysiology. We then summarise and critically evaluate studies using EEG/MEG and neuroimaging measures (MRI and PET), integrating across scales where possible. While a complicated and, at times, confusing picture of ketamine’s effects are revealed, we stress that much of this might be caused by use of different species, doses, and analytical methodologies and suggest strategies that future work could use to answer these problems.

Chronic fluoxetine or ketamine treatment differentially affects brain energy homeostasis which is not exacerbated in mice with trait suboptimal mitochondrial function

Antidepressants have been shown to influence mitochondrial function directly, and suboptimal mitochondrial function (SMF) has been implicated in complex psychiatric disorders. In the current study, we used a mouse model for trait SMF to test the hypothesis that chronic fluoxetine treatment in mice subjected to chronic stress would negatively impact brain bioenergetics, a response that would be more pronounced in mice with trait SMF. In contrast, we hypothesized that chronic ketamine treatment would positively impact mitochondrial function in both WT and mice with SMF. We used an animal model for trait SMF, the Ndufs4^GT/GT mice, which exhibit 25% lower mitochondrial complex I activity. In addition to antidepressant treatment, mice were subjected to chronic unpredictable stress (CUS). This paradigm is widely used to model complex behaviours expressed in various psychiatric disorders. We assayed several physiological indices as proxies for the impact of chronic stress and antidepressant treatment. Furthermore, we measured brain mitochondrial complex activities using clinically validated assays as well as established metabolic signatures using targeted metabolomics. As hypothesized, we found evidence that chronic fluoxetine treatment negatively impacted brain bioenergetics. This phenotype was, however, not further exacerbated in mice with trait SMF. Ketamine did not have a significant influence on brain mitochondrial function in either genotype. Here we report that trait SMF could be a moderator for an individual's response to antidepressant treatment. Based on these results, we propose that in individuals with SMF and comorbid psychopathology, fluoxetine should be avoided, whereas ketamine could be a safer choice of treatment.

Appraising esketamine nasal spray for the management of treatment-resistant depression in adults: Number needed to treat, number needed to harm, and likelihood to be helped or harmed

INTRODUCTION

This post hoc study assessed the evidence-base for esketamine nasal spray for management of treatment-resistant depression (TRD) using number needed to treat (NNT), number needed to harm (NNH), and likelihood to be helped or harmed (LHH).

METHODS

Data sources were four phase III randomized, double-blind studies including two positive studies (acute flexible-dose; maintenance) in patients with TRD. Key efficacy study outcomes: acute response (≥50% decrease from baseline on Montgomery-Asberg Depression Rating Scale [MADRS] total score), acute remission (MADRS scores ≤12). NNT, NNH were calculated for esketamine nasal spray+newly initiated oral antidepressant (esketamine+AD) vs. placebo+AD.

RESULTS

In the pivotal acute flexible-dose study, MADRS response (63.4% vs. 49.5%) and remission (48.2% vs. 30.3%) at 4 weeks resulted in NNT of 8 and 6 for esketamine+AD vs. placebo+AD. NNH values <10 included dissociation (26.1% vs. 3.7%), vertigo (26.1% vs. 2.8%), nausea (26.1% vs. 6.4%), dizziness (20.9% vs. 4.6%), and dysgeusia (24.3% vs. 11.9%). Discontinuation rates due to adverse events (AE) (7.0% vs. 0.9%) yielded NNH=17. LHH comparing MADRS remission vs. discontinuation due to AE was 17 vs. 6. Maintenance use of esketamine+AD demonstrated NNT values<10 for relapse and/or maintenance of remission. In maintenance study, discontinuation due to AE (2.6% vs. 2.1%) yielded NNH=178 (non-significant).

LIMITATIONS

Only dichotomous outcomes were included.

CONCLUSION

NNT<10 for efficacy outcomes suggests potential benefit of esketamine+AD for both acute and maintenance use. LHH was favorable: esketamine+AD was 3 times likely to result in acute remission vs. discontinuations due to AE.

Metabolic Syndrome Rather Than Body Mass Index Is Associated With Treatment Response to Ketamine Infusions

PURPOSE

There is a practical need for the identification of pretreatment clinical and epidemiological response predictors to repeat ketamine infusions. Response predictors can serve to guide clinical inclusion of patients and weigh risks versus benefits for those receiving maintenance ketamine. Previous studies indicate a link between obesity, depression, and treatment response. We sought to investigate if body mass index (BMI) or metabolic syndrome could predict treatment response to ketamine.

METHODS

Patients aged 18 to 72 years who were electroconvulsive therapy nonresponders were given a subanesthetic ketamine hydrochloride dose of 0.5 mg/kg delivered intravenously for 40 minutes for an acute series of 3 to 6 infusions every other day. If patients reported at least a 50% decrease in depression symptoms after the acute series, they were moved to a maintenance series of infusions, on an individualized basis. To assess if BMI or metabolic syndrome could predict response, logistic regression models were run to analyze initial responders, sustained responders, and nonresponders. Models were adjusted for age, sex, and baseline depression severity.

RESULTS

Of the 150 patients analyzed, 56 did not respond to the acute phase, 38 initially responded to the acute phase but relapsed during the maintenance phase, and 56 sustained their response for 1 year. In unadjusted models, BMI was not shown to be a predictor of initial or sustained response. Alternatively, metabolic syndrome defined by a diagnosis of hypertension, hyperglycemia, or hyperlipidemia was determined to be significantly associated with diminished initial response but not sustained response.

CONCLUSIONS

In our patient group, results support the literature that outcome in antidepressant therapy is affected by the presence of metabolic syndrome rather than obesity itself. Although BMI did not predict initial response to ketamine, the presence of metabolic syndrome was significantly negatively associated with the initial response to an acute series of ketamine infusions.

Repurposing Potential of Ketamine: Opportunities and Challenges

Ketamine is a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor which also interacts with various other receptors that account for its myriad actions. Originally approved as a general anesthetic, it is being explored to be repurposed for numerous other indications such as depressive disorders, suicidal ideation, substance-use disorders, anxiety disorders, chronic pain, refractory status epilepticus, and bronchial asthma exacerbations. Numerous trials are ongoing for the same. The nasal spray of esketamine, a more potent S (+) enantiomer of ketamine, has been approved by the United States Food and Drug Administration (USFDA) for treatment-resistant depression along with the oral antidepressants. However, there are concerns about its safety on long term use, given its psychedelic effects and potential abuse. In this review, we discuss repurposing ketamine for potential therapeutic use and about the safety concerns related to ketamine and esketamine.

The NEO-FFI domain of openness to experience moderates ketamine response in treatment resistant depression

BACKGROUND

There are many putative mechanisms by which ketamine has its effect and many unanswered questions about risks and benefits of long-term ketamine therapy. A research imperative is the identification of predictors of response to intravenous ketamine, especially a sustained response to maintenance ketamine. Temperament is an inherited aspect of personality and is a predictive factor for outcome in treatment resistant depressed (TRD) patients.

METHODS

We analyzed which domains of personality impacted initial and sustained ketamine response. Utilizing the Neuroticism Extraversion Openness Five Factor Inventory (NEO-FFI) on 125 participants with TRD, we tested (1) whether the degree of neuroticism predicted initial and/or sustained response to ketamine; and (2) whether extraversion, agreeableness, openness to experience, and conscientiousness had an impact on response.

RESULTS

Our findings confirmed previous literature that elevated neuroticism, low conscientiousness, and low extraversion was the pattern of our TRD population regardless of response. Openness was the only factor to significantly predict sustained treatment outcome.

LIMITATIONS

Our findings are limited by the lack of placebo control, small sample size, non- standardized infusion intervals, polypharmacy rather than ketamine monotherapy, a select TRD population in that they had all failed ECT, and a primarily Caucasian population.

CONCLUSIONS

Our registry adds to the literature that factors making up temperament may have predictive value in regard to treatment response, specifically the outcome for TRD patients receiving long-term ketamine infusion therapy. If confirmed, assessing for Openness could reduce inappropriate exposure to ketamine with its attendant unknown long-term risks.

MicroRNA-Based Biomarkers in the Diagnosis and Monitoring of Therapeutic Response in Patients with Depression

Depression is a debilitating mental illness that affects up to 120 million people worldwide; it is currently determined based on subjective diagnostic schemes that are limited by high uncertainty. Hence, there is an urgent need to identify effective and reliable biomarkers to increase diagnostic accuracy. MicroRNAs (miRNAs) constitute a recently discovered class of non-coding RNAs that play a key role in the regulation of gene expression by modulating translation, messenger RNA (mRNA) degradation, or stability of mRNA targets. Dysregulated expression of miRNAs is being investigated as a clinical biomarker for a variety of diseases, including depression. Accumulating evidence has shown that miRNAs participate in many aspects of neural plasticity, neurogenesis, and the stress response. This is supported by more direct studies based on human postmortem brain tissue that strongly indicate that miRNAs not only play a key role in the pathogenesis of major depressive disorder, but also present potential for the development of therapeutic targets. miRNAs in the peripheral and central nervous system are being considered as potential biomarkers in the diagnosis of depression and in monitoring the therapeutic response to antidepressants, owing to their stability, tissue-specificity, and disease-specific expression. In this review, we focus on various miRNAs in tissues and fluids that could be employed as diagnostic and therapeutic biomarkers in patients with depression.

Recent Studies on Anti-Depressant Bioactive Substances in Selected Species from the Genera Hemerocallis and Gladiolus: A Systematic Review

Herbal therapy is a potential alternative applied to pharmacological alleviation of depression symptoms and treatment of this disorder, which is predicted by the World Health Organization (WHO) to be the most serious health problem worldwide over the next several years. It has been well documented that many herbs with psychotropic effects have far fewer side effects than a variety of pharmaceutical agents used by psychiatrists for the treatment of depression. This systematic review presents literature data on the antidepressant activity of representatives of the genera Hemerocallis (H. fulva and H. citrina Baroni, family Xanthorrhoeaceae) and Gladiolus (G. dalenii, family Iridaceae) and on biologically active compounds and their mechanisms of action to consider the application of herbal preparations supporting the treatment of depression.

Antidepressant effects of ketamine on depression-related phenotypes and dopamine dysfunction in rodent models of stress

Depression, the most prevalent psychiatric disorder, is characterized by increased negative affect (i.e. depressed mood) and reduced positive affect (i.e. anhedonia). Stress is a risk factor for depression in humans, and animal models of chronic stress are typically used to study neurobehavioral alterations relevant to depression. Common behavioral outcomes in rodent models of chronic stress include anhedonia, social dysfunction and behavioral despair. For example, chronically stressed rodents exhibit reduced reward preference, as measured by a loss of preference for sucrose solutions and time spent interacting with a novel conspecific, while also exhibiting less time struggling against inescapable stressors (e.g. forced swim, tail suspension). In both humans and rodents, anhedonia is associated with dysfunction of the dopamine (DA) system. Unlike traditional antidepressants, which are limited by inadequate efficacy and delayed therapeutic response, acute ketamine administration rapidly alleviates depressive symptoms in humans and reverses stress-induced changes in animal models. These effects are partially mediated via actions on the DA system. This review summarizes the clinical effects of ketamine, the neurobiological underpinnings of depression with a focus on DA dysfunction, as well as antidepressant effects of ketamine on depression-related endophenotypes (i.e. anhedonia, despair) and ventral tegmental area (VTA) activity in rodent models of repeated stress. Moreover, we discuss evidence regarding sex differences in ketamine's antidepressant effects, wherein females appear to be more sensitive to lower dose ketamine, as well as novel findings suggesting that ketamine has prophylactic effects with regard to protection against the neurobehavioral impact of future stressors.

The Biology of Human Resilience: Opportunities for Enhancing Resilience Across the Life Span

Recent scientific and technological advances have brought us closer to being able to apply a true biopsychosocial approach to the study of resilience in humans. Decades of research have identified a range of psychosocial protective factors in the face of stress and trauma. Progress in resilience research is now advancing our understanding of the biology underlying these protective factors at multiple phenotypic levels, including stress response systems, neural circuitry function, and immune responses, in interaction with genetic factors. It is becoming clear that resilience involves active and unique biological processes that buffer the organism against the impact of stress, not simply involve a reversal of pathological mechanisms. Here, we provide an overview of recent progress in the field, highlighting key psychosocial milestones and accompanying biological changes during development, and into adulthood and old age. Continued advances in our understanding of psychological, social, and biological determinants of resilience will contribute to the development of novel interventions and help optimize the type and timing of intervention for those most at risk, resulting in a possible new framework for enhancing resilience across the life span.

Adult Cancer Pain, Version 3.2019, NCCN Clinical Practice Guidelines in Oncology

In recent years, the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Adult Cancer Pain have undergone substantial revisions focusing on the appropriate and safe prescription of opioid analgesics, optimization of nonopioid analgesics and adjuvant medications, and integration of nonpharmacologic methods of cancer pain management. This selection highlights some of these changes, covering topics on management of adult cancer pain including pharmacologic interventions, nonpharmacologic interventions, and treatment of specific cancer pain syndromes. The complete version of the NCCN Guidelines for Adult Cancer Pain addresses additional aspects of this topic, including pathophysiologic classification of cancer pain syndromes, comprehensive pain assessment, management of pain crisis, ongoing care for cancer pain, pain in cancer survivors, and specialty consultations.

Temperament and character influence on depression treatment outcome

BACKGROUND

personality features have been repeatedly associated with depression treatment outcome in Major Depressive Disorder (MDD), however conclusive results are still lacking. Moreover, as for Bipolar Disorder (BD), results are only few and preliminary.

AIM

the aim of the present study was to perform an exploratory investigation of the influence of personality traits as assessed by the Temperament and Character Inventory (TCI), on principal depression treatment outcomes (non remission, non response and resistance).

METHODS

743 mood disorders patients (455 MDD (61.24%) and 288 BD (38.76%)) were recruited in the context of 6 European studies. Generalized logit models were performed to test the effects of TCI dimensions on treatment outcomes, considering possible confounders such as age, gender and education. Positive results were controlled for comorbidities (anxiety and substance use disorders) as well.

RESULTS

MDD Non-Remitters showed high Harm Avoidance (HA) and Self Transcendence (ST) (p = 0.0004, d = 0.40; p = 0.007, d = 0.36 respectively) and low Persistence (P) and Self Directedness (SD) (p = 0.05; d = 0.18; p = 0.002, d = 0.40, respectively); MDD Non-Responders showed a slightly different profile with high HA and low Reward Dependence (RD) and SD; finally, MDD Resistants showed low RD, P and Cooperativeness (C). In BD patients, only higher HA in non response was observed.

LIMITATIONS

the retrospective cross-sectional design, the TCI assessment regardless of the mood state and the small number of bipolar patients represent the main limitations.

CONCLUSION

specific TCI personality traits are associated with depression treatment outcome in MDD patients. The inclusion of such personality traits, together with other socio-demographic and clinical predictors, could ameliorate the accuracy of the prediction models available to date.

The long-term effects of single and repeated subanaesthetic ketamine administration on regional cerebral blood flow in healthy dogs measured with 99mTc-HMPAO SPECT

Subanaesthetic ketamine has recently been established as an effective and rapid treatment for major depressive disorder showing antidepressant effects for up to 1 week on average. The use of repeated ketamine infusions has been put forward to augment and to prolong the antidepressant response and increase the remission rates. The underlying neurobiological mechanisms responsible for ketamine's antidepressant effects remain unclear. Nevertheless, it has been shown, both in dogs and humans, that ketamine can alter neuronal perfusion and therefore neuronal function in brain regions involved in psychiatric and behavioural disorders. Consequently, the aim of the current placebo controlled study was to assess the long-term effects on cerebral perfusion of single and repeated subanaesthetic ketamine infusions in dogs. Twelve healthy, laboratory dogs were scanned at six different time points following single and repeated ketamine administration, using Single Photon Emission Computed Tomography with the radiotracer ^99mTc-hexamethylpropylene amine oxime. We hypothesised that repeated infusions could lead to more prolonged perfusion alterations in brain regions critical for behaviour regulation. We found that repeated subanaesthetic ketamine administration did not result in more prolonged cerebral perfusion alterations compared to a single ketamine administration.

MTOR-Mediated Autophagy Is Involved in the Protective Effect of Ketamine on Allergic Airway Inflammation

Unresolved inflammation underpins the pathogenesis of allergic airway diseases, such as asthma. Ketamine, accepted as a promising therapy for resistant asthma, has been demonstrated to attenuate allergic airway inflammation. However, the anti-inflammatory mechanism by ketamine in this setting is largely unknown. We aimed to investigate whether autophagy was involved in the protective effect of ketamine on allergic airway inflammation. Female C57BL/6 mice were sensitized to ovalbumin (OVA) and treated with ketamine at 25, 50, or 100 mg/kg prior to OVA challenge. In this model, the pulmonary morphological findings and airway inflammation were significantly inhibited at 50 mg/kg but not at 25 or 100 mg/kg. Moreover, 50 mg/kg ketamine abrogated the increased concentrations of inflammatory cytokines in bronchoalveolar lavage fluid (BALF) of allergic mice, as well as activated the expression of phosphorylated mammalian target of rapamycin (p-MTOR) and inhibited autophagy in allergic mice. To confirm whether the effect of 50 mg/kg ketamine on asthma was mediated by inhibiting autophagy, rapamycin was administered to mice sensitized to OVA and exposed to 50 mg/kg ketamine. All of the effect of 50 mg/kg ketamine was reversed by rapamycin treatment, including increased p-MTOR and decreased autophagy. Taken together, the present study demonstrates that 50 mg/kg ketamine inhibits allergic airway inflammation by suppressed autophagy, and this effect is mediated by the activation of MTOR in the lungs of allergic mice.

The influence of subanaesthetic ketamine on regional cerebral blood flow in healthy dogs measured with 99mTc-HMPAO SPECT

Subanaesthetic ketamine has recently been proven to be a highly effective and fast acting alternative treatment for several psychiatric disorders. The mechanisms responsible for ketamine's antidepressant effects remain unclear, but a possible explanation could be that ketamine interacts with regional cerebral blood flow (rCBF). Therefore, the effects of two subanaesthetic ketamine doses on rCBF were evaluated. Twelve dogs were randomly assigned to one of the three treatment conditions (condition saline, condition 0.5 mg/kg ketamine or condition 2 mg/kg ketamine) and received in total five saline or ketamine infusions, with one week interval. Single Photon Emission Computed Tomography (SPECT) scans with the radiotracer 99mTc-hexamethylpropylene amine oxime were performed before the start of the infusions (baseline) and 24 hours after the first (single) and last (multiple) infusion. After a wash out period of 3 months, the animals were again assigned to one of the three treatment conditions described above and the infusion/scan protocol was repeated. During the infusions, cardiovascular parameters were evaluated every ten minutes. A one-way repeated measure ANOVA was set up to assess perfusion index for each ketamine dose for the left frontal cortex (alpha = 0.05). The remaining 11 brain regions were post hoc assessed. Perfusion index was significantly increased in the left frontal cortex and in the thalamus 24 hours after single and multiple ketamine infusions compared to baseline in the 2 mg/kg condition. No clinically relevant cardiovascular effects were observed during the ketamine infusions. This study shows that subanaesthetic ketamine can increase neuronal perfusion and therefore alter neuronal function in brain regions involved in depression and anxiety disorders. These perfusion increases may possibly contribute to ketamine's beneficial effects in these psychiatric disorders.

Ketamine as a rapid antidepressant: the debate and implications

Ketamine, a synthetic derivative of phencyclidine, is a commonly misused party drug that is restricted in high-income countries because of its addictive potential. Ketamine is also used as an anaesthetic in human and veterinary medicine. In the 1990s, research using ketamine to study the pathophysiology of schizophrenia was terminated owing to ethical concerns. Recently, controversy surrounding the drug has returned, as researchers have demonstrated that intravenous ketamine infusion has a rapid antidepressant effect and have therefore proposed ketamine as a novel antidepressant. This article debates the question of ketamine as an antidepressant, considering the drug's addictive potential, ethical concerns about prescribing a hallucinogen, the evidence base and motives behind ketamine trials.

General Anesthetics to Treat Major Depressive Disorder: Clinical Relevance and Underlying Mechanisms

Major depressive disorder is a frequent and devastating psychological condition with tremendous public health impact. The underlying pathophysiological mechanisms involve abnormal neurotransmission and a relatedly impaired synaptic plasticity. Since general anesthetics are potent modulators of neuronal activity and, thereby, can exert long-term context-dependent impact on neural networks, an intriguing hypothesis is that these drugs could enhance impaired neural plasticity associated with certain psychiatric diseases. Clinical observations over the past few decades appear to confirm this possibility. Indeed, equipotency of general anesthesia alone in comparison with electroconvulsive therapy under general anesthesia has been demonstrated in several clinical trials. Importantly, in the past 15 years, intravenous administration of subanesthetic doses of ketamine have also been demonstrated to have rapid antidepressant effects. The molecular, cellular, and network mechanisms underlying these therapeutic effects have been partially identified. Although several important questions remain to be addressed, the ensemble of these experimental and clinical observations opens new therapeutic possibilities in the treatment of depressive disorders. Importantly, they also suggest a new therapeutic role for anesthetics that goes beyond their principal use in the perioperative period to facilitate surgery.

Post-Operative Cognitive Dysfunction: An exploration of the inflammatory hypothesis and novel therapies

Post-Operative Cognitive Dysfunction (POCD) is a highly prevalent condition with significant clinical, social and financial impacts for patients and their communities. The underlying pathophysiology is becoming increasingly understood, with the role of neuroinflammation and oxidative stress secondary to surgery and anaesthesia strongly implicated. This review aims to describe the putative mechanisms by which surgery-induced inflammation produces cognitive sequelae, with a focus on identifying potential novel therapies based upon their ability to modify these pathways.

Ketamine Inhibition of the Pentameric Ligand-Gated Ion Channel GLIC

Ketamine inhibits pentameric ligand-gated ion channels (pLGICs), including the bacterial pLGIC from Gloeobacter violaceus (GLIC). The crystal structure of GLIC shows R-ketamine bound to an extracellular intersubunit cavity. Here, we performed molecular dynamics simulations of GLIC in the absence and presence of R- or S-ketamine. No stable binding of S-ketamine in the original cavity was observed in the simulations, largely due to its unfavorable access to residue D154, which provides important electrostatic interactions to stabilize R-ketamine binding. Contrary to the symmetric binding shown in the crystal structure, R-ketamine moved away from some of the binding sites and was bound to GLIC asymmetrically at the end of simulations. The asymmetric binding is consistent with the experimentally measured negative cooperativity of ketamine binding to GLIC. In the presence of R-ketamine, all subunits showed changes in structure and dynamics, irrespective of binding stability; the extracellular intersubunit cavity expanded and intersubunit electrostatic interactions involved in channel activation were altered. R-ketamine binding promoted a conformational shift toward closed GLIC. Conformational changes near the ketamine-binding site were propagated to the interface between the extracellular and transmembrane domains, and further to the pore-lining TM2 through two pathways: pre-TM1 and the β1-β2 loop. Both signaling pathways have been predicted previously using the perturbation-based Markovian transmission model. The study provides a structural and dynamics basis for the inhibitory modulation of ketamine on pLGICs.

Anhedonia as a clinical correlate of suicidal thoughts in clinical ketamine trials

BACKGROUND

Identifying clinical correlates associated with reduced suicidal ideation may highlight new avenues for the treatment of suicidal thoughts. Anhedonia occurs across psychiatric diagnoses and has been associated with specific neural circuits in response to rapid-acting treatments, such as ketamine. This analysis sought to evaluate whether reductions in suicidal ideation after ketamine administration were related to reduced levels of anhedonia, independent of depressive symptoms.

METHODS

This post-hoc analysis included treatment-resistant patients with either major depressive disorder (MDD) or bipolar disorder (BD) from several clinical trials of ketamine. Anhedonia was assessed using a subscale of the Beck Depression Inventory (BDI) and the Snaith-Hamilton Pleasure Scale (SHAPS). The outcome of interest was suicidal ideation, as measured by a subscale of the Scale for Suicide Ideation (SSI5), one day post-ketamine administration.

RESULTS

Anhedonia, as measured by the SHAPS, was associated with suicidal thoughts independent of depressive symptoms both before and after ketamine administration. One day post-ketamine administration, improvements on the SHAPS accounted for an additional 13% of the variance in suicidal thought reduction, beyond the influence of depressive symptoms. The BDI anhedonia subscale was not significantly associated with suicidal thoughts after adjusting for depressive symptoms.

LIMITATIONS

Data were limited to patients experiencing a major depressive episode and may not be generalizable to patients experiencing an active suicidal crisis.

CONCLUSIONS

Suicidal thoughts may be related to symptoms of anhedonia independent of other depressive symptoms. These results have implications for the potential mechanisms of action of ketamine on suicidal thoughts.

Glutamatergic regulation of cognition and functional brain connectivity: insights from pharmacological, genetic and translational schizophrenia research

The pharmacological modulation of glutamatergic neurotransmission to improve cognitive function has been a focus of intensive research, particularly in relation to the cognitive deficits seen in schizophrenia. Despite this effort, there has been little success in the clinical use of glutamatergic compounds as procognitive drugs. Here, we review a selection of the drugs used to modulate glutamatergic signalling and how they impact on cognitive function in rodents and humans. We highlight how glutamatergic dysfunction, and NMDA receptor hypofunction in particular, is a key mechanism contributing to the cognitive deficits observed in schizophrenia and outline some of the glutamatergic targets that have been tested as putative procognitive targets for this disorder. Using translational research in this area as a leading exemplar, namely, models of NMDA receptor hypofunction, we discuss how the study of functional brain network connectivity can provide new insight into how the glutamatergic system impacts on cognitive function. Future studies characterizing functional brain network connectivity will increase our understanding of how glutamatergic compounds regulate cognition and could contribute to the future success of glutamatergic drug validation. Linked Articles This article is part of a themed section on Pharmacology of Cognition: a Panacea for Neuropsychiatric Disease? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.19/issuetoc.

Investigational drugs in recent clinical trials for treatment-resistant depression

INTRODUCTION

The authors describe the medications for treatment-resistant depression (TRD) in phase II/III of clinical development in the EU and USA and provide an opinion on how current treatment can be improved in the near future. Areas covered: Sixty-two trials were identified in US and EU clinical trial registries that included six investigational compounds in recent phase III development and 12 others in recent phase II clinical trials. Glutamatergic agents have been the focus of many studies. A single intravenous dose of the glutamatergic modulator ketamine produces a robust and rapid antidepressant effect in persons with TRD; this effect continues to remain significant for 1 week. This observation was a turning point that opened the way for other, more selective glutamatergic modulators (intranasal esketamine, AVP-786, AVP-923, AV-101, and rapastinel). Of the remaining compounds, monoclonal antibodies open highly innovative therapeutic options, based on new pathophysiological approaches to depression. Expert commentary: Promising new agents are emerging for TRD treatment. Glutamatergic modulators likely represent a very promising alternative to monoaminergic antidepressant monotherapy. We could see the arrival of the first robust and rapid acting antidepressant drug in the near future, which would strongly facilitate the ultimate goal of recovery in persons with TRD.

Social defeat models in animal science: What we have learned from rodent models

Studies on stress and its impacts on animals are very important in many fields of science, including animal science, because various stresses influence animal production and animal welfare. In particular, the social stresses within animal groups have profound impact on animals, with the potential to induce abnormal behaviors and health problems. In humans, social stress induces several health problems, including psychiatric disorders. In animal stress models, social defeat models are well characterized and used in various research fields, particularly in studies concerning mental disorders. Recently, we have focused on behavior, nutrition and metabolism in rodent models of social defeat to elucidate how social stresses affect animals. In this review, recent significant progress in studies related to animal social defeat models are described. In the field of animal science, these stress models may contribute to advances in the development of functional foods and in the management of animal welfare.

Childhood neglect predicts the course of major depression in a tertiary care sample: a follow-up study

BACKGROUND

The course of depression is poorer in clinical settings than in the general population. Several predictors have been studied and there is growing evidence that a history of childhood maltreatment consistently predicts a poorer course of depression.

METHODS

Between 2008 and 2012, we assessed 238 individuals suffering from a current episode of major depression. Fifty percent of these (N = 119) participated in a follow-up study conducted between 2012 and 2014 that assessed sociodemographic and clinical variables, the history of childhood abuse and neglect (using the Adverse Childhood Experience questionnaire), and the course of depression between baseline and follow-up interview (using the Life Chart method). The Structured Clinical Interview for DSM-IV-TR was used to assess diagnosis at baseline and follow-up interview. Statistical analyses used the life table survival method and Cox proportional hazard regression tests.

RESULTS

Among 119 participants, 45.4% did not recover or remit during the follow-up period. The median time to remission or recovery was 28.9 months and the median time to the first recurrence was 25.7 months. Not being married, a chronic index depressive episode, comorbidity with an anxiety disorder, and a childhood history of physical neglect independently predicted a slower time to remission or recovery. The presence of three or more previous depression episodes and a childhood history of emotional neglect were independent predictors of depressive recurrences.

CONCLUSIONS

Childhood emotional and physical neglect predict a less favorable course of depression. The effect of childhood neglect on the course of depression was independent of sociodemographic and clinical variables.

What is the mechanism of Ketamine's rapid-onset antidepressant effect? A concise overview of the surprisingly large number of possibilities

WHAT IS KNOWN AND OBJECTIVE

Abundant clinical data now confirm that ketamine produces a remarkable rapid-onset antidepressant effect - hours or days - in contrast to the delayed onset (typically weeks) of current antidepressant drugs. This surprising and revolutionary finding may lead to the development of life-saving pharmacotherapy for depressive illness by reducing the high suicide risk associated with the delayed onset of effect of current drugs. As ketamine has serious self-limiting drawbacks that restrict its widespread use for this purpose, a safer alternative is needed. Our objective is to review the proposed mechanism(s) of ketamine's rapid-onset antidepressant action for new insights into the physiological basis of depressive illness that may lead to new and novel targets for antidepressant drug discovery.

METHODS

A search was conducted on published literature (e.g. PubMed) and Internet sources to identify information relevant to ketamine's rapid-acting antidepressant action and, specifically, to the possible mechanism(s) of this action. Key search words included 'ketamine', 'antidepressant', 'mechanism of action', 'depression' and 'rapid acting', either individually or in combination. Information was sought that would include less well-known, as well as well-known, basic pharmacologic properties of ketamine and that identified and evaluated the several hypotheses about ketamine's mechanism of antidepressant action.

RESULTS

Whether the mechanistic explanation for ketamine's rapid-onset antidepressant action is related to its well-known antagonism of the NMDA (N-Methyl-d-aspartate) subtype of glutamate receptor or to something else has not yet been fully elucidated. The evidence from pharmacologic, medicinal chemistry, animal model and drug-discovery sources reveals a wide variety of postulated mechanisms.

WHAT IS NEW AND CONCLUSION

The surprising discovery of ketamine's rapid-onset antidepressant effect is a game-changer for the understanding and treatment of depressive illness. There is some convergence on NMDA receptor antagonism as a likely, but to date unproven, common mechanism. The surprising number of other mechanisms, and the several novel biochemical aetiologies of depression proposed, suggests exciting new drug-discovery targets.

Role of brain-derived neurotrophic factor in the molecular neurobiology of major depressive disorder

Major depressive disorder (MDD) is one of the most common neuropsychiatric disorders, which affects up to 20% of people in their lifetime in the United States. The exact neurobiological mechanisms of MDD remain elusive, and the diagnostics are still uncertain. Basic and clinical research from recent years demonstrated that the etiology of MDD might be associated with genetic changes of neurotrophins, particularly brain-derived neurotrophic factor (BDNF). BDNF plays a key role in neuronal development and neurogenesis. However, the detailed mechanisms related to depression and antidepressant responses are not fully understood. This review summarizes the current knowledge of the causal relationship between BDNF and MDD, and describes the important role of BDNF in the progress of depression in animal models and patients with depressive disorders.

Rapid and sustained symptom reduction following psilocybin treatment for anxiety and depression in patients with life-threatening cancer: a randomized controlled trial

BACKGROUND

Clinically significant anxiety and depression are common in patients with cancer, and are associated with poor psychiatric and medical outcomes. Historical and recent research suggests a role for psilocybin to treat cancer-related anxiety and depression.

METHODS

In this double-blind, placebo-controlled, crossover trial, 29 patients with cancer-related anxiety and depression were randomly assigned and received treatment with single-dose psilocybin (0.3 mg/kg) or niacin, both in conjunction with psychotherapy. The primary outcomes were anxiety and depression assessed between groups prior to the crossover at 7 weeks.

RESULTS

Prior to the crossover, psilocybin produced immediate, substantial, and sustained improvements in anxiety and depression and led to decreases in cancer-related demoralization and hopelessness, improved spiritual wellbeing, and increased quality of life. At the 6.5-month follow-up, psilocybin was associated with enduring anxiolytic and anti-depressant effects (approximately 60-80% of participants continued with clinically significant reductions in depression or anxiety), sustained benefits in existential distress and quality of life, as well as improved attitudes towards death. The psilocybin-induced mystical experience mediated the therapeutic effect of psilocybin on anxiety and depression.

CONCLUSIONS

In conjunction with psychotherapy, single moderate-dose psilocybin produced rapid, robust and enduring anxiolytic and anti-depressant effects in patients with cancer-related psychological distress.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00957359.

Exposure to Ketamine Anesthesia Affects Rat Impulsive Behavior

Introduction: Ketamine is a general anesthetic (GA) that activates several neurotransmitter pathways in various part of the brain. The acute effects as GA are the most well-known and sought-after: to induce loss of responsiveness and to produce immobility during invasive procedures. However, there is a concern that repeated exposure might induce behavioral changes that could outlast their acute effect. Most research in this field describes how GA affects cognition and memory. Our work is to access if general anesthesia with ketamine can disrupt the motivational behavior trait, more specifically measuring impulsive behavior. Methods: Aiming to evaluate the effects of exposure to repeat anesthetic procedures with ketamine in motivational behavior, we tested animals in a paradigm of impulsive behavior, the variable delay-to-signal (VDS). In addition, accumbal and striatal medium spiny neurons morphology was assessed. Results: Our results demonstrated that previous exposure to ketamine deep-anesthesia affects inhibitory control (impulsive behavior). Specifically, ketamine exposed animals maintain a subnormal impulsive rate in the initial periods of the delays. However, in longer delays while control animals progressively refrain their premature unrewarded actions, ketamine-exposed animals show a different profile of response with higher premature unrewarded actions in the last seconds. Animals exposed to multiple ketamine anesthesia also failed to show an increase in premature unrewarded actions between the initial and final periods of 3 s delays. These behavioral alterations are paralleled by an increase in dendritic length of medium spiny neurons of the nucleus accumbens (NAc). Conclusions: This demonstrates that ketamine anesthesia acutely affects impulsive behavior. Interestingly, it also opens up the prospect of using ketamine as an agent with the ability to modulate impulsivity trait.

MicroRNAs as biomarkers for major depression: a role for let-7b and let-7c

There is a growing emphasis in the field of psychiatry on the need to identify candidate biomarkers to aid in diagnosis and clinical management of depression, particularly with respect to predicting response to specific therapeutic strategies. MicroRNAs are small nucleotide sequences with the ability to regulate gene expression at the transcriptomic level and emerging evidence from a range of studies has highlighted their biomarker potential. Here we compared healthy controls (n=20) with patients diagnosed with major depression (n=40) and who were treatment-resistant to identify peripheral microRNA biomarkers, which could be used for diagnosis and to predict response to electroconvulsive therapy (ECT) and ketamine (KET) infusions, treatments that have previously shown to be effective in treatment-resistant depression (TRD). At baseline and after treatment, blood samples were taken and symptom severity scores rated using the Hamilton Depression Rating Scale (HDRS). Samples were analyzed for microRNA expression using microarray and validated using quantitative PCR. As expected, both treatments reduced HDRS scores. Compared with controls, the baseline expression of the microRNA let-7b was less by ~40% in TRD patients compared with controls. The baseline expression of let-7c was also lower by ~50% in TRD patients who received ECT. Bioinformatic analysis revealed that let-7b and let-7c regulates the expression of 27 genes in the PI3k-Akt-mTOR signaling pathway, which has previously been reported to be dysfunctional in depression. The expression of miR-16, miR-182, miR-451 and miR-223 were similar to that in controls. Baseline microRNA expression could not predict treatment response and microRNAs were unaffected by treatment. Taken together, we have identified let-7b and let-7c as candidate biomarkers of major depression.

Ketamine for treatment-resistant depression: recent developments and clinical applications

Approximately one-third of patients with major depressive disorder (MDD) do not respond to existing antidepressants, and those who do generally take weeks to months to achieve a significant effect. There is a clear unmet need for rapidly acting and more efficacious treatments. We will review recent developments in the study of ketamine, an old anaesthetic agent which has shown significant promise as a rapidly acting antidepressant in treatment-resistant patients with unipolar MDD, focusing on clinically important aspects such as dose, route of administration and duration of effect. Additional evidence suggests ketamine may be efficacious in patients with bipolar depression, post-traumatic stress disorder and acute suicidal ideation. We then discuss the safety of ketamine, in which most neuropsychiatric, neurocognitive and cardiovascular disturbances are short lasting; however, the long-term effects of ketamine are still unclear. We finally conclude with important information about ketamine for primary and secondary physicians as evidence continues to emerge for its potential use in clinical settings, underscoring the need for further investigation of its effects.