Antidepressant efficacy of ketamine in treatment-resistant major depression: a two-site randomized controlled trial

Ketamine's Altered States Meta-Analysis: The Relationship Between Psychomimetic and Clinical Effects With Focus in Depression

BACKGROUND

In recent years, there has been a significant focus on exploring the potential therapeutic impact of altered states of consciousness on treatment outcomes for mental illness, with the goal of enhancing therapeutic strategies and patient results.

METHODS

This meta-analysis was designed to investigate the potential link between the psychomimetic effects of ketamine and clinical outcomes in mental health, which adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Eleven studies were selected for meta-analysis, and the main result did not find a significant correlation between the psychoactive effects of ketamine and clinical outcomes either in mental illness (n = 11; n's = 27; r = 0.06 [-0.05, 0.17]; P = 0.268) or depression exclusively (n = 10; n's = 25; r = 0.03 [-0.07, 0.13]; P = 0.561). High heterogeneity was found for general analysis ( I2 = 80.78). Egger's regression did not indicate publication bias (intercept = 1.57; SE = 1.49, P = 0.30). No significant Kendall's rank correlation coefficient was observed ( τ = 0.02, P = 0.88) indicating funnel plot symmetry. The sub-analyses, aimed at minimizing study variability by specifically examining factors such as patient disorders (limited to depression), methods of administration (exclusively intravenous), types of assessment instruments, and the timing of evaluations, also yielded no significant findings.

CONCLUSION

This meta-analysis suggests that the altered states of consciousness experienced during ketamine sessions are not directly linked to clinical outcomes. However, it is important to acknowledge that the limited number of studies and their heterogeneity render this conclusion preliminary, warranting further investigation over time.

Redefining Ketamine Pharmacology for Antidepressant Action: Synergistic NMDA and Opioid Receptor Interactions?

Ketamine is a racemic compound and medication comprised of (S)-ketamine and (R)-ketamine enantiomers and its metabolites. It has been used for decades as a dissociative anesthetic, analgesic, and recreational drug. More recently, ketamine, its enantiomers, and its metabolites have been used or are being investigated for the treatment of refractory depression, as well as for comorbid disorders such as anxiety, obsessive-compulsive, and opioid use disorders. Despite its complex pharmacology, ketamine is referred to as an N-methyl-d-aspartate (NMDA) receptor antagonist. In this review, the authors argue that ketamine's pharmacology should be redefined to include opioid receptors and the endogenous opioid system. They also highlight a potential mechanism of action of ketamine for depression that is attributed to bifunctional, synergistic interactions involving NMDA and opioid receptors.

Molecular mechanism of programmed cell death in drug-induced neuronal damage: A special focus on ketamine-induced neurotoxicity

In recent years, the abuse of ketamine as a recreational drug has been growing, and has become one of the most widely abused drugs. Continuous using ketamine poses a risk of drug addiction and complications such as attention deficit disorder, memory loss and cognitive decline. Ketamine-induced neurotoxicity is thought to play a key role in the development of these neurological complications. In this paper, we focus on the molecular mechanisms of ketamine-induced neurotoxicity. According to our analyses, drugs in causing neurotoxicity are closely associated with programmed cell death (PCD) such as apoptosis, autophagy, necroptosis, pyroptosis, and Ferroptosis. Therefore, this review will collate the existing mechanisms of programmed death in ketamine-induced neurotoxicity as well as explore the possible mechanisms by outlining the mechanisms of programmed death in other drug-induced neurotoxicity, which may be helpful in identifying potential therapeutic targets for neurotoxicity induced by ketamine abuse.

Classification of psychedelics and psychoactive drugs based on brain-wide imaging of cellular c-Fos expression

Psilocybin, ketamine, and MDMA are psychoactive compounds that exert behavioral effects with distinguishable but also overlapping features. The growing interest in using these compounds as therapeutics necessitates preclinical assays that can accurately screen psychedelics and related analogs. We posit that a promising approach may be to measure drug action on markers of neural plasticity in native brain tissues. We therefore developed a pipeline for drug classification using light sheet fluorescence microscopy of immediate early gene expression at cellular resolution followed by machine learning. We tested male and female mice with a panel of drugs, including psilocybin, ketamine, 5-MeO-DMT, 6-fluoro-DET, MDMA, acute fluoxetine, chronic fluoxetine, and vehicle. In one-versus-rest classification, the exact drug was identified with 67% accuracy, significantly above the chance level of 12.5%. In one-versus-one classifications, psilocybin was discriminated from 5-MeO-DMT, ketamine, MDMA, or acute fluoxetine with >95% accuracy. We used Shapley additive explanation to pinpoint the brain regions driving the machine learning predictions. Our results suggest a unique approach for characterizing and validating psychoactive drugs with psychedelic properties.

Protocol of an open-label safety and feasibility pilot study of ketamine-assisted psychotherapy for methamphetamine use disorder (the KAPPA trial)

INTRODUCTION

Methamphetamine use disorder is a significant public health concern. No pharmacological treatment options currently exist for methamphetamine use disorder, and psychotherapy is only moderately effective. Preliminary evidence suggests that ketamine-assisted psychotherapy produces sustained improvements in substance use and mental health symptomatology. In addition to direct antidepressant properties, ketamine is hypothesised to increase synaptogenesis and facilitate neuroplasticity, in turn prolonging and enhancing the effects of psychotherapy. Given the withdrawal-associated dysphoria and neurocognitive impairments characterising methamphetamine use disorder, ketamine-assisted psychotherapy may improve the efficacy of psychotherapy alone by addressing these features and facilitating therapeutic engagement. This pilot study aims to investigate the safety and feasibility (time taken to recruit sample, proportion of ineligible participants at pre-screening and screening, number of participants who complete four sessions of psychotherapy, retention rate over full duration of study, acceptability of the intervention) of subanaesthetic ketamine in combination with psychotherapy (cognitive behavioural therapy) for adults with methamphetamine use disorder. Changes in methamphetamine use, cravings and withdrawal, quality of life, and treatment satisfaction will also be explored.

METHODS AND ANALYSIS

This is an open-label, single-arm clinical trial. 20 adults meeting DSM-5-TR criteria for methamphetamine use disorder who are seeking to reduce or cease methamphetamine use will be enrolled in the study through a single-site specialist outpatient stimulant treatment service in inner Sydney (St Vincent's Hospital, Sydney). A 4-week course with three subcutaneous ketamine doses (0.75 mg/kg to 0.9 mg/kg, titrated according to tolerability) at weekly intervals and four sessions of cognitive behavioural therapy (one at treatment initiation and three within 24-48 hours following each ketamine administration session) will be delivered. Safety and feasibility will be assessed over an 8-week period. Secondary outcomes (changes in methamphetamine use, cravings, withdrawal, quality of life and treatment satisfaction) will be assessed over a 24-week period.

ETHICS AND DISSEMINATION

This study has been approved by the St Vincent's Hospital Human Research Ethics Committee, reference 2023/ETH00530. Study findings will be disseminated through articles in scientific, peer-reviewed journals, and at national and international conferences.

TRIAL REGISTRATION NUMBER

ANZCTR: ACTRN12624000895583.

PROTOCOL VERSION

The trial protocol (Version 4.0) was approved on 24 June 2024.

Efficacy and safety of ketamine and esketamine in reducing the incidence of postpartum depression: an updated systematic review and meta-analysis

BACKGROUND

Postpartum depression (PPD) is categorized by the Disorders-Fifth Edition as depression that begins during pregnancy or within the first month after giving birth. Ketamine and esketamine have shown promising results in the treatment of several depressive disorders, which suggests that they may have a role in the prevention of PPD. This systematic review and meta-analysis aim to update evidence about the efficacy and safety of using ketamine and esketamine to reduce PPD incidence.

METHODS

We searched four databases, PubMed, Scopus, Web of Science, and Cochrane, to collect relevant studies. We included studies which investigated the preventive effect of ketamine or esketamine on PPD among women after giving birth through caesarean or vaginal delivery. We extracted PPD occurrence rate, PPD score, pain score and side effects. Finally, a meta-analysis was conducted using RevMan software.

RESULTS

Twenty-one eligible studies were incorporated in the current systematic review and meta-analysis involving 4,389 pregnant women. Esketamine was the intervention in 14 studies, and ketamine was used in 7 studies. In subgroup analysis, both ketamine and esketamine were significantly effective in reducing the incidence of short-term PPD (ketamine: RR = 0.72, 95% CI [0.56, 0.93], P = 0.01; esketamine: RR = 0.43, P < 0.0001). Esketamine only significantly reduced the incidence of long-term PPD (RR = 0.44, P < 0.00001). Low doses and high doses were effective in reducing the incidence of both short-term (high dose: RR = 0.48, P = 0.0005; low dose: RR = 0.46, P = 0.002) and long-term PPD (high dose: RR = 0.54, P < 0.0001; low dose: RR = 0.61, P = 0.009). Regarding the risk of side effects, patients in the Ketamine/esketamine group showed statistically significant higher rates of developing dizziness (P = 0.0007), blurred vision (P = 0.02), vomiting (P = 0.004) and hallucinations (P = 0,002) than women in the control group.

CONCLUSION

Both ketamine and esketamine are effective in lowering the incidence of short-term PPD. On the other hand, only esketamine is effective in reducing the incidence of long-term PPD. It is recommended to use smaller doses for a more tolerable treatment period since doses less than 0.5 mg are significantly effective. Temporary side effects such as dizziness, blurred vision, vomiting and hallucinations were reported.

Ketamine effects on resting state functional brain connectivity in major depressive disorder patients: a hypothesis-driven analysis based on a network model of depression

Introduction

Ketamine demonstrates robust and rapidly occurring antidepressant effects in patients with difficult-to-treat major depressive disorder. Ketamine's antidepressant effects and its impact on functional networks in non-resistant forms of major depressive disorder are expected to provide valuable insight into ketamine's mechanism of action related to depression.

Methods

This study employs an existing network model of major depressive disorder to investigate the effects of ketamine on resting state connectivity in a therapy-non-resistant major depressive disorder population. In a randomized, double-blind, placebo-controlled, cross-over study, 0.5 mg/kg racemic ketamine or 0.9%NaCl was administered intravenously in 16 MDD patients. We applied resting-state functional magnetic resonance imaging (rs-fMRI) to explore changes in functional brain connectivity directly at 50, 80 and 165 min (acute) and 24 h (delayed) following ketamine administration. A clinician-rated 10-item scale (MADRS) was administered at 165 min and 24 h after ketamine administration. Connections-of-interest (COIs) were based on the previously published corticolimbic-insular-striatalpallidal-thalamic (CLIPST) circuitry model of major depressive disorder.

Results

Compared with placebo, ketamine significantly (p < 0.0014) reduced the mean (SD) MADRS total score from 21.2 (5.9) pre-dose to 10.3 (4.6) 24 h post-dose. At both acute (p < 0.0172) and delayed (p < 0.0488) time points, significant rs-fMRI connectivity changes occurred only in MDD-related COIs as proposed by the CLIPST model. No changes in functional connectivity were found in non-CLIPST connections.

Discussion

This study demonstrates that ketamine specifically affects depression-related circuitry. Analyzing functional connectivity based on a neurocircuitry model of a specific CNS disease and drug action may be an effective approach that could result in a more targeted analysis in future pharmaco-fMRI studies in CNS drug development.

Safety outcomes of ketamine for treatment-resistant depression in clinical settings and development of the ketamine side effect tool-revised (KSET-R)

BACKGROUND

Ketamine and its derivates (e.g. esketamine) are increasingly used in clinical settings for treatment-resistant depression (TRD). Ketamine can give rise to acute, cumulative and longer-term side effects (SEs) across a treatment course. The Ketamine Side Effect Tool (KSET) examines adverse effects though its length has affected feasibility for use in clinical settings.

OBJECTIVE

To estimate the frequency of ketamine SEs occurring in real-world settings using the KSET, additional validated scales and laboratory measures. Utilising this naturalistic data, to develop a shorter, more feasible and validated tool (KSET-Revised; KSET-R).

METHODS

Retrospective patient and safety data from three outpatient services were collected which included KSET symptom questions, standardised scales and laboratory measures. We calculated frequency of SEs occurring intra-session, intersession and at follow-up. Revision of the KSET included removal of items based on a priori criteria. Construct and concurrent validity were examined by comparison of specific KSET items and the overall tolerability rating with standardised scales.

RESULTS

Descriptive statistics including SE frequencies are reported and the KSET-R is detailed: a shorter tool with construct and concurrent validity for specific items, along with the overall tolerability rating.

LIMITATIONS

small sample size for follow-up data; predominantly subcutaneous racemic and intranasal esketamine analysed - other routes and formulations not examined; and subjective not objective cognition measured.

CONCLUSIONS

Naturalistic data gives an estimate of frequency of ketamine SEs within session, between sessions and at follow-up. The KSET-R has improved feasibility and clinical utility and is recommended for use in clinical practice where ketamine is prescribed.

Is there a risk of esketamine misuse in clinical practice?

In 2019, intranasal esketamine gained approval as a promising therapy for those individuals grappling with treatment-resistant depression. Both clinical trials and real-world studies have underscored its efficacy in alleviating and remitting depressive symptoms, with sustained benefits observed for nearly 4.5 years. As the S-enantiomer of ketamine, esketamine's dosing guidelines and strict medical supervision stem from prior research on ketamine's use in depression and history as a recreational drug. Despite initial concerns, long-term clinical studies have not documented instances of abuse, misuse, addiction or withdrawal, and the same was found in case reports or subsamples of high-risk populations with comorbidities such as substance use disorder or alcohol use disorder. Esketamine has proven to be safe and well tolerated without fostering new-onset substance use in vulnerable groups. Real-world studies reinforced these observations, reporting no adverse events (AEs) related to pharmacological interactions of esketamine with any other substance, and no new-onset drug or alcohol misuse, craving, misuse or diversion of use. Reports of esketamine craving remain rare, with only one case report documented in 2022. Most drug-related AEs reported in pharmacovigilance databases are those identified in the product's technical data sheet and with known reported frequency. More importantly, no register of illicit acquisition of esketamine or its tampering for obtaining ketamine or other altered products was found in our search. Overall, our review confirms esketamine's safety across diverse patient populations, reassuring its responsible use and the scarcity of reports of abuse or misuse since its introduction to the market.

Visual analysis of research hotspots and trends in traditional Chinese medicine for depression in the 21st century: A bibliometric study based on citespace and VOSviewer

Background and objectives

Depression long been a key concern for scholars worldwide; however, the field of depression has not received sufficient attention in traditional Chinese medicine. It was not until the 21st century that research into depression gradually entered a period of rapid development, with an increasing number of academic studies published in major journals. However, one limitation of this field is that no scholars have yet summarised the development process and key research issues. Therefore, the present study aimed to summarise the research trends and progress in this field, providing relevant information and presenting potential future research directions for subsequent researchers.

Methods

Literature in this field was searched from January 1, 2000 to April 20, 2024 in the Web of Science Core Collection database, to analyse the current status of the literature and publication trends. Bibliographic information, including study authors, organisations, keywords, countries, references, citations, and co-citations, was extracted using CiteSpace and VOSviewer software for quantitative analysis, visual mapping, and scientific evaluation.

Results

A total of 921 papers were included, with a significant increase in the number of publications from 2017 to 2021, and a stable number of more than 140 publications between 2022 and 2023, with publications in these two years accounting for 31.38 % of the total. The Journal of Ethnopharmacology had the highest number of publications (97) and citations (2067), as well as the highest number of co-citations (1369). China (847 publications, 13256 citations), Beijing University of Chinese Medicine (90 publications, 1232 citations), and Qin Xuemei (30 publications, 759 citations) were the most prolific and influential countries, organisations, and authors in the field, respectively. Keyword clustering co-occurrence analysis revealed nine different clusters with good homogeneity. The top three clusters were randomised controlled trials, traditional Chinese medicine, and hippocampal neurogenesis. In the timeline analysis of keywords, from 2000 to 2010, keywords in this field were concentrated on hippocampal neurology and forced swimming test as clustering axes of Traditional Chinese Medicine. From 2010 to 2020, the research hotspots focused on randomised controlled trials and hippocampal neurogenesis. After 2020, keywords became more focused on network pharmacology. In addition, the occurrence time of explosive keywords were distributed before 2010 and after 2020. Before 2010, these keywords included the forced swimming test, Tail Suspension Test, Chronic Cold Stress, Neural Regeneration, and Banxia Houpu Decoction. Conversely, network Pparmacology and Molecular Docking arose as key buzzwords starting in 2020.

Conclusions

This study comprehensively analysed and summarised the research hotspots and trends in this field of research in the 21st century from a bibliometric perspective, further generating a series of visual graphs to help researchers understand the current research status, potential collaborators, collaborating institutions, and potential future research hotspots in this field.

Repeated subcutaneous esketamine on treatment-resistant depression: An open-label dose titration study

BACKGROUND

Ketamine has gained prominence as one of the most effective therapeutic options in unipolar treatment-resistant depression (TRD). However, most studies related to the antidepressant action of ketamine used intravenous (IV) or intranasal (IN) administration. The subcutaneous (SC) route of administration is a promising alternative, as it results in plasma levels comparable to IV, causes fewer side effects, and is easier and cheaper to administer than both IV and/or IN routes.

METHODS

In this context, we conducted an open-label clinical trial for investigating the efficacy and safety of 8 weekly sessions of SC esketamine in TRD patients (n = 30).

RESULTS

At the end of the treatment, a partial response rate of 26.09 %, a response rate of 52.17 % and remission rate of 34.78 % were observed, assessed by Montgomery-Åsberg Depression Rating Scale. Moreover, the self-reported depressive symptoms, as measured by the Beck Depression Inventory II (BDI-II), significantly decreased from the baseline to the final session, and the improvements were sustained throughout the week. Follow-up evaluations (BDI-II) up to the sixth month consistently showed scores lower than the baseline.

LIMITATIONS

The small sample size and the drop-out during the follow-up phase may limit the generalizability of the findings. Additionally, the absence of a control group necessitates cautious interpretation of causality.

CONCLUSIONS

This groundbreaking study, which addresses SC esketamine treatment for TRD, reported promising response and remission rates, as well as sustained antidepressant effects. It highlights the need for further research to improve and expand our knowledge of this innovative, more accessible, and cost-effective therapeutic approach.

Proteomic patterns associated with ketamine response in major depressive disorders

BACKGROUND

Major depressive disorder (MDD) is characterized by persistent feelings of sadness and loss of interest. Ketamine has been widely used to treat MDD owing to its rapid effect in relieving depressive symptoms. Importantly, not all patients respond to ketamine treatment. Identifying sub-populations who will benefit from ketamine, as well as those who may not, prior to treatment initiation, would significantly advance precision medicine in patients with MDD.

METHODS

Here, we used mass spectrometry-based plasma proteomics to analyze matched pre- and post-ketamine treatment samples from a cohort of 30 MDD patients whose treatment outcomes and demographic and clinical characteristics were considered.

RESULTS

Ketamine responders and non-responders were identified according to their individual outcomes after two weeks of treatment. We analyzed proteomic alterations in post-treatment samples from responders and non-responders and identified a collection of six proteins pivotal to the antidepressive effect of ketamine. Subsequent co-regulation analysis revealed that pathways related to immune response were involved in ketamine response. By comparing the proteomic profiles of samples from the same individuals at the pre- and post-treatment time points, dynamic proteomic rearrangements induced by ketamine revealed that immune-related processes were activated in association with its antidepressive effect. Furthermore, receiver operating characteristic curve analysis of pre-treatment samples revealed three proteins with strong predictive performance in determining the response of patients to ketamine before receiving treatment.

CONCLUSIONS

These findings provide valuable knowledge about ketamine response, which will ultimately lead to more personalized and effective treatments for patients.

TRIAL REGISTRATION

The study was registered in the Chinese Clinical Trials Registry (ChiCTR-OOC-17012239) on May 26, 2017.

Association of intravenous ketamine with change in depressive symptoms in a large integrated health care system

OBJECTIVE

Racemic ketamine intravenous treatments (KIT) are widely used in community clinics for treatment resistant depression (TRD), but we lack studies on symptom improvement during standardized delivery to clinically complex patients with TRD. We aimed to assess depression symptom change for patients receiving standardized KIT for TRD in a large integrated health care delivery system relative to similar patients receiving standard medication management.

METHODS

In this retrospective cohort study (n = 570), depression symptom change measured by the 9-item Patient Health Questionnaire (PHQ-9) was examined in 143 adults with TRD receiving 0.5mg/kg 40-minute KIT infusion twice weekly for 3 weeks from 01/01/2018 to 12/31/2022 and 427 contemporaneous patients with medication management (MM) matched on variables including sex, race, age, and baseline depression symptom score. We excluded patients with major neurocognitive disorder, schizophrenia, or pregnancy.

RESULTS

The KIT group was more likely to achieve depression response (PHQ-9 reduction >50 %) compared to MM (adjusted risk ratio [aRR]= 1.72, 95 % CI = 1.17 - 2.53; P = 0.006). The KIT group (8 % vs 5 %) was more likely to achieve depression remission (i.e. PHQ-9 < 5); however, the adjusted risk with KIT vs MM was not statistically significant. Baseline depression symptoms were associated with higher depression symptoms at follow up, as were co-occurring anxiety and personality disorders.

CONCLUSIONS

KIT was significantly associated with depression response and symptom improvement compared to MM. Clinicians should consider comorbid personality disorder, anxiety disorders, and baseline depression severity as potential predictors of KIT and other treatment response in TRD.

Psychedelics for the Treatment of Psychiatric Disorders: Interpreting and Translating Available Evidence and Guidance for Future Research

During the past decade, there has been extraordinary public, media, and medical research interest in psychedelics as promising therapeutics for difficult-to-treat psychiatric disorders. Short-term controlled trial data suggest that certain psychedelics are effective and safe in the treatment of major depressive disorder, treatment-resistant depression, and posttraumatic stress disorder. Preliminary evidence also supports efficacy in other psychiatric disorders (e.g., tobacco and alcohol use disorders). Notwithstanding the interest and promise of psychedelics, concerns have arisen with respect to the interpretability and translatability of study results. For example, aspects related to short- and long-term safety, abuse liability, and the essentiality of the psychedelic "trip" and psychological support are, inter alia, insufficiently characterized with psychedelic agents. The overarching aims in this overview are 1) to review methodological aspects that affect inferences and interpretation of extant psychedelic studies in psychiatric disorders, and 2) to provide guidance for future research and development of psychedelic treatment in psychiatry, critical to study interpretation and clinical implementation.

Ketamine use in a large global sample: Characteristics, patterns of use and emergency medical treatment

BACKGROUND

Ketamine's popularity has surged globally in the past decade, especially among young men. Emergency department visits due to its toxicity remain relatively rare, often linked to co-occurring use of other substances.

AIMS

Using data from the Global Drug Survey (GDS) 2018, this study explored the correlates associated with lifetime and past-year ketamine use, and estimated the socio-demographic characteristics, usage patterns and experiences of respondents seeking emergency medical treatment (EMT) after ketamine use.

METHODS

Secondary analysis of GDS 2018, an online cross-sectional survey on drug use patterns conducted between November 2017 and January 2018.

RESULTS

The survey received 130,761 valid responses, with 5.93% reporting lifetime ketamine use, of which 57.70% used ketamine within the past year. Predominantly, respondents were from Germany, England and Denmark. Within the past year, 8.55% met the criteria for ketamine dependence. Respondents who used ketamine in their lifetime tended to be young (mean (x̄) = 27.37 years), men, heterosexual and of white ethnicity. Younger age (x̄ = 24.84 years), gay sexual orientation, student status, past-year use of other drugs and no lifetime mental health diagnosis were associated with past-year ketamine use. Among 4477 respondents reporting past-year ketamine use, 120 adverse events were reported, with less than 0.10% prompting EMT seeking.

CONCLUSION

The study reveals frequent ketamine use but low harm occurrence, underscoring the complex interplay between ketamine use, substance use and dependence, and related factors. This underscores the need to reassess EMT priorities, implement tailored harm reduction strategies and incorporate comprehensive screening for addressing ketamine and substance dependence challenges.

Aberrant glutamatergic systems underlying impulsive behaviors: Insights from clinical and preclinical research

Impulsivity is a broad construct that often refers to one of several distinct behaviors and can be measured with self-report questionnaires and behavioral paradigms. Several psychiatric conditions are characterized by one or more forms of impulsive behavior, most notably the impulsive/hyperactive subtype of attention-deficit/hyperactivity disorder (ADHD), mood disorders, and substance use disorders. Monoaminergic neurotransmitters are known to mediate impulsive behaviors and are implicated in various psychiatric conditions. However, growing evidence suggests that glutamate, the major excitatory neurotransmitter of the mammalian brain, regulates important functions that become dysregulated in conditions like ADHD. The purpose of the current review is to discuss clinical and preclinical evidence linking glutamate to separate aspects of impulsivity, specifically motor impulsivity, impulsive choice, and affective impulsivity. Hyperactive glutamatergic activity in the corticostriatal and the cerebro-cerebellar pathways are major determinants of motor impulsivity. Conversely, hypoactive glutamatergic activity in frontal cortical areas and hippocampus and hyperactive glutamatergic activity in anterior cingulate cortex and nucleus accumbens mediate impulsive choice. Affective impulsivity is controlled by similar glutamatergic dysfunction observed for motor impulsivity, except a hyperactive limbic system is also involved. Loss of glutamate homeostasis in prefrontal and nucleus accumbens may contribute to motor impulsivity/affective impulsivity and impulsive choice, respectively. These results are important as they can lead to novel treatments for those with a condition characterized by increased impulsivity that are resistant to conventional treatments.

Effects of Ketamine vs. Midazolam in Adolescent Treatment Resistant Depression

Background: Adolescent treatment resistant depression (TRD) is increasing in recent years. While ketamine showed rapid antidepressant effects in adult TRD studies, research on its effectiveness in adolescents is limited. Methods: This study examines the effects of intravenous ketamine vs. midazolam on depressive and anxiety symptomatology assessed by the Montgomery-Åsberg Depression Rating Scale (MADRS), Hamilton Anxiety Rating Scale (HAM-A), and Children's Depression Inventory (CDI) at two time points-2 h after initial infusion (T0+2h) and 24 h after the end of the treatment (Te+24h) in a sample of 55 adolescent TRD females (27 receiving ketamine, 28 midazolam). Results: At T0+2h, within-group comparisons revealed a significant reduction in MADRS and HAM-A scores compared to baseline in the ketamine and midazolam groups. At Te+24h, both groups demonstrated similar significant reductions in MADRS, HAM-A, and CDI scores compared to baseline. The MADRS assessment in the ketamine group showed 33% and 59% responders, and in the midazolam group, 14% and 46% responders at T0+2h and Te+24h, respectively. HAM-A evaluation in the ketamine group revealed 33% and 56% responders, and in the midazolam group, 11% and 39% responders at T0+2h and at Te+24h, respectively. CDI rating discovered 11% and 44% responders in the ketamine group and 4% and 21% responders in the midazolam group at T0+2h and Te+24h, respectively. Moreover, inner tension significantly decreased in ketamine compared to the midazolam group at Te+24h. Conclusions: Ketamine showed a reduction in depressive and anxiety symptoms during a short-term period with particular efficacy in alleviating inner tension over midazolam, suggesting its potential advantages in specific symptom relief in rarely studied adolescent TRD.

Learning how to make use of dissociative therapies

Dissociative therapies are being increasingly explored for their psychiatric applications, although questions remain about how they work and how best to use them. In exploring these questions, this review highlights six key areas of clinical relevance: (1) The possible contributions of functional unblinding when interpreting efficacy data; (2) The degree to which the therapeutic effects of dissociative therapies can be distinguished from the transient forms of relief seen with recreational drug use; (3) Understanding the construct of dissociation as it is tasked with describing the function of dissociative drugs; (4) The investigation of subjective drug effects as predictors of therapeutic outcome; (5) Similarities and differences in the effects of dissociative and classic psychedelics; and (6) The anticipated need for judicious prescribing/deprescribing resources as dissociative therapies proliferate.

Efficacy and safety of intravenous ketamine treatment in Japanese patients with treatment-resistant depression: A double-blind, randomized, placebo-controlled trial

AIM

Although the antidepressant effect of ketamine on treatment-resistant depression (TRD) has been frequently reported in North American and European countries, evidence is scarce among the Asian population. We aimed to evaluate the efficacy and safety of intravenous ketamine in Japanese patients with TRD.

METHODS

In this double-blind randomized placebo-controlled trial, 34 Japanese patients with TRD were randomized to receive either intravenous ketamine (0.5 mg/kg) or placebo, administered over 40 min, twice a week, for 2 weeks. The primary outcome was the change in the Montgomery Åsberg Depression Rating Scale (MADRS) total score from baseline to post-treatment. Secondary outcomes included changes in other depressive symptomatology scores and remission, response, and partial response rates. We also examined the association between baseline clinical demographic characteristics and changes in the MADRS total score.

RESULTS

Intention-to-treat analysis indicated no significant difference in the decrease in MADRS total score between the groups (-8.1 ± 10.0 vs -2.5 ± 5.2, t[32] = 2.02, P = 0.052), whereas per-protocol analysis showed a significant reduction in the ketamine group compared to the placebo group (-9.1 ± 10.2 vs -2.7 ± 5.3, t[29] = 2.22, P = 0.034). No significant group differences were observed in other outcomes. Adverse events were more frequent in the ketamine group than in the placebo group, and no serious adverse events were reported. A higher baseline MADRS total score and body mass index were associated with a greater reduction in the MADRS total score.

CONCLUSION

Intravenous ketamine outperformed placebo in Japanese patients with TRD who completed the study, suggesting that ketamine could alleviate depressive symptoms of TRD across diverse ethnic populations.

Ketamine differentially affects implicit and explicit memory processes in rats

RATIONALE

Ketamine, a non-competitive NMDA receptor antagonist, produces antidepressant effects at subanesthetic doses. The therapeutic effect, however, is often accompanied by cognitive side effects, including memory impairments. Yet, the specific effects of ketamine on different processes of implicit and explicit memory remain to be elucidated.

OBJECTIVES

We examined the effect of an antidepressant dose of ketamine (10 mg/kg, IP) on the encoding, retrieval, and modulation processes of fear memory and spatial memory in adult Wistar rats.

METHODS

Ketamine was administered before the fear acquisition, retrieval, or extinction procedures in a Pavlovian fear conditioning task. In another set of experiments, it was administered before the training, probe trial, or reversal training phases of the Morris Water Maze (MWM).

RESULTS

The antidepressant dose of ketamine partially impaired fear extinction when administered before the acquisition or retrieval. In contrast, it facilitated memory modulation and decreased the escape latency in the first day of reversal training in the MWM when administered before the training or reversal training sessions. Encoding or retrieval performance in either type of memory was not affected.

CONCLUSIONS

These findings show that ketamine does not impair the acquisition or retrieval processes of cued fear or spatial memory; but exerts differential effects on memory modulation of these implicit and explicit memory paradigms, by disrupting fear extinction and facilitating reversal spatial learning.

Classification of psychedelics and psychoactive drugs based on brain-wide imaging of cellular c-Fos expression

Psilocybin, ketamine, and MDMA are psychoactive compounds that exert behavioral effects with distinguishable but also overlapping features. The growing interest in using these compounds as therapeutics necessitates preclinical assays that can accurately screen psychedelics and related analogs. We posit that a promising approach may be to measure drug action on markers of neural plasticity in native brain tissues. We therefore developed a pipeline for drug classification using light sheet fluorescence microscopy of immediate early gene expression at cellular resolution followed by machine learning. We tested male and female mice with a panel of drugs, including psilocybin, ketamine, 5-MeO-DMT, 6-fluoro-DET, MDMA, acute fluoxetine, chronic fluoxetine, and vehicle. In one-versus-rest classification, the exact drug was identified with 67% accuracy, significantly above the chance level of 12.5%. In one-versus-one classifications, psilocybin was discriminated from 5-MeO-DMT, ketamine, MDMA, or acute fluoxetine with >95% accuracy. We used Shapley additive explanation to pinpoint the brain regions driving the machine learning predictions. Our results support a novel approach for characterizing and validating psychoactive drugs with psychedelic properties.

Esketamine-Induced Dissociation: A Case Report

Esketamine, the isolated S-enantiomer of ketamine, has been a recent breakthrough as a non-monoaminergic treatment for treatment-resistant depression (TRD). This case report explores a rare adverse event in a 41-year-old female with TRD, who, despite experiencing significant depressive improvement with esketamine, encountered a severe dissociative episode accompanied by hallucinogenic-like phenomena. While esketamine's efficacy in TRD is well-documented, this pronounced dissociation should be taken into consideration by researchers and clinicians before prescribing. As esketamine continues to aid TRD treatment, comprehension of its safety profile becomes essential for informed decision-making, ensuring optimized patient care in the vast development of antidepressant therapies.

Simulated synapse loss induces depression-like behaviors in deep reinforcement learning

Deep Reinforcement Learning is a branch of artificial intelligence that uses artificial neural networks to model reward-based learning as it occurs in biological agents. Here we modify a Deep Reinforcement Learning approach by imposing a suppressive effect on the connections between neurons in the artificial network-simulating the effect of dendritic spine loss as observed in major depressive disorder (MDD). Surprisingly, this simulated spine loss is sufficient to induce a variety of MDD-like behaviors in the artificially intelligent agent, including anhedonia, increased temporal discounting, avoidance, and an altered exploration/exploitation balance. Furthermore, simulating alternative and longstanding reward-processing-centric conceptions of MDD (dysfunction of the dopamine system, altered reward discounting, context-dependent learning rates, increased exploration) does not produce the same range of MDD-like behaviors. These results support a conceptual model of MDD as a reduction of brain connectivity (and thus information-processing capacity) rather than an imbalance in monoamines-though the computational model suggests a possible explanation for the dysfunction of dopamine systems in MDD. Reversing the spine-loss effect in our computational MDD model can lead to rescue of rewarding behavior under some conditions. This supports the search for treatments that increase plasticity and synaptogenesis, and the model suggests some implications for their effective administration.

Ketamine-induced altered states of consciousness: a systematic review of implications for therapeutic outcomes in psychiatric practices

This systematic review aims to elucidate the nexus between ketamine's psychoactive properties and its efficacy in treating a broad spectrum of psychiatric disorders. We searched three databases and used citation tracking to include 29 studies. Predominantly, mood disorders, including bipolar disorder (BD) and major depressive disorder (MDD) (MDD + BD: + n = 25 studies), a large part of them involve treatment-resistant patients (n = 14 studies), substance use disorder (SUD, n = 3 studies), and social anxiety disorder (SAD, n = 1 study). From all included studies (n = 29), 15 (51.72%) of them identified a positive relation between ketamine-induced altered states of consciousness and clinical outcomes, while 13 studies (44.83%) showed no linkage between them, and one study (3.45%) delineated a negative association. Focusing solely on intravenous (IV) ketamine infusions (n = 25), 14 studies (56%) reported a positive modulation of ketamine's psychoactive effects and therapeutic benefits, whereas 10 studies (40%) confirmed no relationship, and one study (4%) showed a negative association. The single study (33.34%) involving subcutaneous ketamine and all three studies (66.6%) intranasal administration did not demonstrate a significant interaction between ketamine's psychoactive effects and therapeutic response. All three SUD studies reported a positive correlation between ketamine's psychoactive effects and therapeutic response. In contrast, the single SAD study did not find a relationship between these parameters. For studies involving mood disorders (n = 25), 12 studies (48%) reported a positive relationship between psychoactive effects and therapeutic response. Others 12 studies (48%) identified a null relationship, and one study (4%) found a significant negative association. Although we have found a larger association than previous studies between ketamine's psychoactive properties and its efficacy in treating a broad spectrum of psychiatric disorders, its topic remains indeterminate, mainly due to the high heterogeneity.

Effect of different doses of esketamine on the median effective concentration of propofol for inhibiting body movement during hysteroscopy

The objective of this study is to investigate the effects of various doses of esketamine on the median effective concentration (EC50) of propofol required for inhibiting body movement during hysteroscopy. Additionally, this research aims to explore the pharmacodynamic interactions between esketamine and propofol. Prospective, double-blind, up-down sequential allocation study. Operating room, post-anesthesia care unit (PACU), and general ward. A total of 90 patients were allocated into three groups in a randomized, double-blinded manner as follows: 0.1 mg/kg esketamine combined with propofol intravenous injection (EP0.1) group, 0.2 mg/kg esketamine combined with propofol intravenous injection (EP0.2) group, 0.3 mg/kg esketamine combined with propofol of intravenous injection (EP0.3) group. For the initial patient in each group, the starting effector target concentration of propofol was set at 4 µg/ml. Each patient received an initial intravenous injection of 0.04 mg/kg midazolam, followed by the administration of the appropriate dose of esketamine. Ten seconds after the esketamine injection, propofol was administered intravenously to achieve the target concentration. In accordance with the sequential method principle, the concentration of propofol for the subsequent patient was adjusted based on the response of the previous patient. Effective inhibition of body movement was defined as the absence of any involuntary body movements throughout the entire surgical process. If the previous patient exhibited body movements, the propofol concentration for the next patient was increased by 0.5 µg/ml; conversely, if no movements were observed, it was decreased by 0.5 µg/ml. The up-down sequential allocation method and probit regression were used to calculate the EC50 of propofol. Hospital Anxiety and Depression Scale-Anxiety (HADS-A) and Depression (HADS-D) score, adverse events, hemodynamic changes, demographic data and clinical characteristics. The EC50 of propofol was 3.849 μg/ml (95% CI: 3.419-4.281) in the EP0.1 group, 3.641 μg/ml (95% CI: 2.807-4.200) in the EP0.2 group, and 3.417 μg/ml (95% CI: 2.845-3.852) in the EP0.3 group. These findings suggest that esketamine can dose-dependently reduce the EC50 of propofol. Esketamine can dose-dependently reduce the EC50 of propofol in hysteroscopy, while concurrently lowering patients' HADS-A and HADS-D scores 24 h post-operation. It is concluded that the optimal dose of esketamine, when combined with propofol for hysteroscopy, is 0.3 mg/kg.

Prophylactic (R,S)-ketamine and (2S,6S)-hydroxynorketamine Decrease Fear Expression by Differentially Modulating Fear Neural Ensembles

BACKGROUND

We previously reported that a single injection of (R,S)-ketamine or its metabolite (2S,6S)-hydroxynorketamine (HNK) prior to stress attenuated learned fear. However, whether these drugs attenuate learned fear through divergent or convergent effects on neural activity remains to be determined.

METHODS

129S6/SvEv male mice were injected with saline, (R,S)-ketamine, or (2S,6S)-HNK 1 week before a 3-shock contextual fear conditioning paradigm. Five days later, mice were re-exposed to the aversive context and euthanized 1 hour later to quantify active cells. Brains were processed for c-fos immunoreactivity, and neural networks were built with a novel, wide-scale imaging pipeline.

RESULTS

We found that (R,S)-ketamine and (2S,6S)-HNK attenuated learned fear. Fear-related neural activity was altered in dorsal CA3 following (2S,6S)-HNK; ventral CA3 and CA1, infralimbic and prelimbic regions, insular cortex, retrosplenial cortex, piriform cortex, nucleus reuniens, and periaqueductal gray following both (R,S)-ketamine and (2S,6S)-HNK; and in the paraventricular nucleus of the thalamus (PVT) following (R,S)-ketamine. Dorsal CA3 and ventral hippocampus activation correlated with freezing in the (R,S)-ketamine group, and retrosplenial cortex activation correlated with freezing in both (R,S)-ketamine and (2S,6S)-HNK groups. (R,S)-ketamine increased connectivity between cortical and subcortical regions while (2S,6S)-HNK increased connectivity within these regions.

CONCLUSIONS

This work identifies novel nodes in fear networks that involve the nucleus reuniens, piriform cortex, insular cortex, periaqueductal gray, and retrosplenial cortex that can be targeted with neuromodulatory strategies or pharmaceutical compounds to treat fear-induced disorders. This approach could be used to optimize target engagement and dosing strategies of existing medications.

Evidence for the Contribution of the miR-206/BDNF Pathway in the Pathophysiology of Depression

Depression is a complex disorder with substantial impacts on individual health and has major public health implications. Depression results from complex interactions between genetic and environmental factors. Epigenetic mechanisms, including DNA methylation, microRNAs (miRNAs), and histone modifications, can produce heritable phenotypic changes without a change in DNA sequence and recently were proven to mediate lasting increases in the risk of depression following exposure to adverse life events. Of these, miRNAs are gaining attention for their role in the pathogenesis of many stress-associated mental disorders, including depression. One such miRNA is microRNA-206 (miR-206), which is a critical candidate for increasing the susceptibility to stress. Although miR-206 is thought to be a typical muscle-specific miRNA, it is expressed throughout the brain, particularly in the hippocampus and prefrontal cortex. Until now, only a few studies have been conducted on rodents to understand the role of miR-206 in stress-related abnormalities in neurogenesis. However, the precise underlying molecular mechanism of miR-206-mediated depression-like behaviors remains largely unknown. Here, we reviewed recent advances in the field of biomedical and clinical research on the role of miR-206 in the pathogenesis of depression from studies using different tissues and various experimental designs and described how abnormalities in miR-206 expression in these tissues can affect neuronal functions. Moreover, we focused on studies investigating the brain-derived neurotrophic factor (BDNF) as a functional target of miR-206, where miR-206 has been implicated in the pathogenesis of depression by suppressing the expression of the BDNF. In summary, these studies confirm the existence of a tight correlation between the pathogenesis of depression and the miR-206/BDNF pathway.

Ketamine Prevents Inflammation-Induced Reduction of Human Hippocampal Neurogenesis via Inhibiting the Production of Neurotoxic Metabolites of the Kynurenine Pathway

BACKGROUND

Understanding the precise mechanisms of ketamine is crucial for replicating its rapid antidepressant effects without inducing psychomimetic changes. Here, we explore whether the antidepressant-like effects of ketamine enantiomers are underscored by protection against cytokine-induced reductions in hippocampal neurogenesis and activation of the neurotoxic kynurenine pathway in our well-established in vitro model of depression in a dish.

METHODS

We used the fetal hippocampal progenitor cell line (HPC0A07/03C) to investigate ketamine's impact on cytokine-induced reductions in neurogenesis in vitro. Cells were treated with interleukin- 1beta (IL-1b) (10 ng/mL) or IL-6 (50 pg/mL), alone or in combination with ketamine enantiomers arketamine (R-ketamine, 400 nM) or esketamine (S-ketamine, 400 nM) or antidepressants sertraline (1 mM) or venlafaxine (1 mM).

RESULTS

Resembling the effect of antidepressants, both ketamine enantiomers prevented IL-1b- and IL-6-induced reduction in neurogenesis and increase in apoptosis. This was mediated by inhibition of IL-1b-induced production of IL-2 and IL-13 by R-ketamine and of IL-1b-induced tumor necrosis factor-alpha by S-ketamine. Likewise, R-ketamine inhibited IL-6-induced production of IL-13, whereas S-ketamine inhibited IL-6-induced IL-1b and IL-8. Moreover, both R- and S-ketamine prevented IL-1b-induced increases in indoleamine 2,3-dioxygenase expression as well as kynurenine production, which in turn was shown to mediate the detrimental effects of IL-1b on neurogenesis and apoptosis. In contrast, neither R- nor S-ketamine prevented IL-6-induced kynurenine pathway activation.

CONCLUSIONS

Results suggest that R- and S-ketamine have pro-neurogenic and anti-inflammatory properties; however, this is mediated by inhibition of the kynurenine pathway only in the context of IL-1b. Overall, this study enhances our understanding of the mechanisms underlying ketamine's antidepressant effects in the context of different inflammatory phenotypes, ultimately leading to the development of more effective, personalized therapeutic approaches for patients suffering from depression.

Therapeutic Protocols Using Ketamine and Esketamine for Depressive Disorders: A Systematic Review

Depression is one of the most prevalent mental health disorders globally, causing severe emotional suffering, reducing life expectancy and increasing the risk of suicide. Recently, the use of dissociative psychedelic substances such as ketamine and esketamine for depressive disorders has expanded treatment options. We sought to analyze, through a systematic review, the existing protocols for the treatment of depression with ketamine and esketamine. The search adopted PRISMA criteria and was performed using PubMed and Web of Science databases. Procedures in each study were compared, focusing on the sample recruited, therapeutic approaches, including the clinical team and professionals engaged in treatment, medical procedures, description of the setting (including music) and factors such as specific medication (ketamine or esketamine), route of administration and dosage employed. Results indicated the predominance of a medical approach, with a limited number of studies on ketamine assisted psychotherapy (KAP) and other modalities of psychedelic assisted therapy. Additionally, there is limited information on psychosocial elements such as preparation, psychological support during session and integration of experience. Altogether these findings suggest that treatment of depression with ketamine or esketamine diverges in relation to the practices employed with psychedelic substances. This is discussed considering future research directions in the field.

Efficacy of ketamine versus esketamine in the treatment of perioperative depression: A review

Depression is a significant factor contributing to postoperative occurrences, and patients diagnosed with depression have a higher risk for postoperative complications. Studies on cardiovascular surgery extensively addresses this concern. Several studies report that people who undergo coronary artery bypass graft surgery have a 20% chance of developing postoperative depression. A retrospective analysis of medical records spanning 21 years, involving 817 patients, revealed that approximately 40% of individuals undergoing coronary artery bypass grafting (CABG) were at risk of perioperative depression. Patients endure prolonged suffering from illness because each attempt with standard antidepressants requires several weeks to be effective. In addition, multi-drug combination adjuvants or combination medication therapy may alleviate symptoms for some individuals, but they also increase the risk of side effects. Conventional antidepressants primarily modulate the monoamine system, whereas different therapies target the serotonin, norepinephrine, and dopamine systems. Esketamine is a fast-acting antidepressant with high efficacy. Esketamine is the S-enantiomer of ketamine, a derivative of phencyclidine developed in 1956. Esketamine exerts its effect by targeting the glutaminergic system the glutaminergic system. In this paper, we discuss the current depression treatment strategies with a focus on the pharmacology and mechanism of action of esketamine. In addition, studies reporting use of esketamine to treat perioperative depressive symptoms are reviwed, and the potential future applications of the drug are presented.

The Relationship of Immune Markers with Severity and Heritability of Depressive Disorder: A Cross-Sectional Hospital-Based Study from North India

Background

Inflammatory response plays a pivotal role in the pathophysiology of depression. With this background, we planned this study to see if immune markers, interleukin 6 (IL-6), and erythrocyte sedimentation rate (ESR) are raised in subjects with major depressive disorder (MDD) and compare its level with healthy controls and first-degree relatives of subjects. We also explored if variation in the level of these markers was related to the severity of depression.

Methods

This comparative observational study included 120 subjects, who were divided into three groups of 40 individuals each. Group 1 was the MDD group, group 2 was the healthy first-degree relative group, and group 3 was the healthy control group. All the subjects were then made to undergo estimation of IL-6 (pg/mL) and ESR (mm/h) from our hospital biochemistry lab. The patients in group 1 were additionally screened for the severity of depression.

Results

The mean IL-6 and ESR measure within the MDD group was 9.20 ± 13.40 (pg/mL) and 5.90 ± 5.35 (mm/h), respectively. We found that the mean and median values of both IL-6 and ESR were highest in the MDD group as compared to other groups, which were statistically significant (p <0.05). A pairwise comparison found no significant difference in the IL-6 and ESR scores among the healthy controls and healthy first-degree relatives. The mean of IL-6 was highest in individuals with moderate severity of depression, while the mean of ESR was highest in individuals with severe depression.

Conclusion

The immune markers, IL-6 and ESR, were significantly raised in the MDD group; however, the levels did not correlate significantly with the differential severity of the depressive disorder as per Hamilton depression rating scale (HAM-D) scores.

Intravenous patient-controlled analgesia with esketamine improves early depressive symptoms in patients with postherpetic neuralgia: a single-center retrospective cohort study

OBJECTIVE

Patients with Postherpetic Neuralgia (PHN) often exhibit depressive-like symptoms, significantly impacting their quality of life. Esketamine, known for its analgesic properties, has also been recognized for its rapid antidepressant effects. However, its efficacy in the treatment of PHN requires further exploration. This study aims to evaluate the impact of intravenous patient-controlled analgesia(PICA) with esketamine on depressive mood in PHN patients.

METHODS

This retrospective study analyzed PHN patients hospitalized and treated at the affiliated hospital of Southwest Medical University from June 2021 to March 2023. Patients were divided into the esketamine group (E group) and the sufentanil group (S group) based on their treatment regimens. Primary outcomes included pain numerical rating scale(NRS), depression patient health questionaire-9(PHQ-9), and anxiety generalized anxiety disorder-7(GAD-7) scores measured before treatment, and at 3 days, 7 days, 1 month, 2 months, and 3 months post-treatment.

RESULTS

A total of 83 patients were included in the analysis. Before treatment, there were no statistically significant differences in pain NRS, depression PHQ-9, and anxiety GAD-7 scores between the two groups (P > 0.05). Compared to before treatment, significant reductions in pain NRS scores were observed at all post-treatment time points in both groups (P < 0.05), with no differences between groups (P > 0.05). The E group exhibited significantly lower depression PHQ-9 scores than the S group at 3 days and 7 days post-treatment (P < 0.05), but no significant differences were observed at 1 month, 2 months, and 3 months (P > 0.05). Anxiety GAD-7 scores were significantly lower in the E group compared to the S group at 3 days, 7 days post-treatment (P < 0.05), with no statistical differences at 1 month, 2 months, and 3 months post-treatment (P > 0.05).

CONCLUSION

Both PICA with esketamine and sufentanil alleviated pain equally in PHN patients. However, PICA with esketamine specifically improved early symptoms of anxiety and depression.

Participation of Ca2+-Calmodulin-Dependent Protein Kinase II in the Antidepressant-Like Effects of Melatonin

Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine secreted by the pineal gland during the dark phase of the photoperiod. Its main function is the synchronization of different body rhythms with the dark-light cycle. Research on melatonin has significantly advanced since its discovery and we now know that it has considerable significance in various physiological processes, including immunity, aging, and reproduction. Moreover, in recent years evidence of the pharmacological possibilities of melatonin has increased. Indoleamine, on the other hand, has antidepressant-like effects in rodents, which may be mediated by the activation of calcium-calmodulin-dependent kinase II (CaMKII) and are also related to the regulation of neuroplasticity processes, including neurogenesis, synaptic maintenance, and long-term potentiation. Remarkably, patients with major depression show decreased levels of circulating melatonin in plasma. This review presents evidence of the antidepressant-like effects of melatonin in preclinical models and the participation of CaMKII in these actions. CaMKII's role in cognition and memory processes, which are altered in depressive states, are part of the review, and the effects of melatonin in these processes are also reviewed. Furthermore, participation of CaMKII on structural and synaptic plasticity and the effects of melatonin are also described. Finally, the advantages of using melatonin in combination with other antidepressants such as ketamine for neuroplasticity are described. Evidence supports that CaMKII is activated by melatonin and downstream melatonin receptors and may be the common effector in the synergistic effects of melatonin with other antidepressants. SIGNIFICANCE STATEMENT: This review compiled evidence supporting that melatonin causes antidepressant-like effects in mice through calmodulin kinase II stimulation of downstream melatonin receptors as well as the participation of this enzyme in neuroplasticity, memory, and cognition. Finally, we describe evidence about the effectiveness of antidepressant-like effects of melatonin in combination with ketamine.

Predicting treatment response to ketamine in treatment-resistant depression using auditory mismatch negativity: Study protocol

BACKGROUND

Ketamine has recently attracted considerable attention for its rapid effects on patients with major depressive disorder, including treatment-resistant depression (TRD). Despite ketamine's promising results in treating depression, a significant number of patients do not respond to the treatment, and predicting who will benefit remains a challenge. Although its antidepressant effects are known to be linked to its action as an antagonist of the N-methyl-D-aspartate (NMDA) receptor, the precise mechanisms that determine why some patients respond and others do not are still unclear.

OBJECTIVE

This study aims to understand the computational mechanisms underlying changes in the auditory mismatch negativity (MMN) response following treatment with intravenous ketamine. Moreover, we aim to link the computational mechanisms to their underlying neural causes and use the parameters of the neurocomputational model to make individual treatment predictions.

METHODS

This is a prospective study of 30 patients with TRD who are undergoing intravenous ketamine therapy. Prior to 3 out of 4 ketamine infusions, EEG will be recorded while patients complete the auditory MMN task. Depression, suicidality, and anxiety will be assessed throughout the study and a week after the last ketamine infusion. To translate the effects of ketamine on the MMN to computational mechanisms, we will model changes in the auditory MMN using the hierarchical Gaussian filter, a hierarchical Bayesian model. Furthermore, we will employ a conductance-based neural mass model of the electrophysiological data to link these computational mechanisms to their neural causes.

CONCLUSION

The findings of this study may improve understanding of the mechanisms underlying response and resistance to ketamine treatment in patients with TRD. The parameters obtained from fitting computational models to EEG recordings may facilitate single-patient treatment predictions, which could provide clinically useful prognostic information.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05464264. Registered June 24, 2022.

Preoperative ketamine administration for prevention of postoperative neurocognitive disorders after major orthopedic surgery in elderly patients: A multicenter randomized blinded placebo-controlled trial

BACKGROUND

Preventive anesthetic impact on the high rates of postoperative neurocognitive disorders in elderly patients is debated. The Prevention of postOperative Cognitive dysfunction by Ketamine (POCK) study aimed to assess the effect of ketamine on this condition.

METHODS

This is a multicenter, randomized, double-blind, interventional study. Patients ≥60 years undergoing major orthopedic surgery were randomly assigned in a 1:1 ratio to receive preoperative ketamine 0.5 mg/kg as an intravenous bolus (n = 152) or placebo (n = 149) in random blocks stratified according to the study site, preoperative cognitive status and age. The primary outcome was the proportion of objective delayed neurocognitive recovery (dNR) defined as a decline of one or more neuropsychological assessment standard deviations on postoperative day 7. Secondary outcomes included a three-month incidence of objective postoperative neurocognitive disorder (POND), as well as delirium, anxiety, and symptoms of depression seven days and three months after surgery.

RESULTS

Among 301 patients included, 292 (97%) completed the trial. Objective dNR occurred in 50 (38.8%) patients in the ketamine group and 54 (40.9%) patients in the placebo group (OR [95% CI] 0.92 [0.56; 1.51], p = 0.73) on postoperative day 7. Incidence of objective POND three months after surgery did not differ significantly between the two groups nor did incidence of delirium, anxiety, apathy, and fatigue. Symptoms of depression were less frequent in the ketamine group three months after surgery (OR [95% CI] 0.34 [0.13-0.86]).

CONCLUSIONS

A single preoperative bolus of intravenous ketamine does not prevent the occurrence of dNR or POND in elderly patients scheduled for major orthopedic surgery. (Clinicaltrials.gov NCT02892916).

The N-methyl-d-aspartate receptor hypothesis of ketamine's antidepressant action: evidence and controversies

Substantial clinical evidence has unravelled the superior antidepressant efficacy of ketamine: in comparison to traditional antidepressants targeting the monoamine systems, ketamine, as an N-methyl-d-aspartate receptor (NMDAR) antagonist, acts much faster and more potently. Surrounding the antidepressant mechanisms of ketamine, there is ample evidence supporting an NMDAR-antagonism-based hypothesis. However, alternative arguments also exist, mostly derived from the controversial clinical results of other NMDAR inhibitors. In this article, we first summarize the historical development of the NMDAR-centred hypothesis of rapid antidepressants. We then classify different NMDAR inhibitors based on their mechanisms of inhibition and evaluate preclinical as well as clinical evidence of their antidepressant effects. Finally, we critically analyse controversies and arguments surrounding ketamine's NMDAR-dependent and NMDAR-independent antidepressant action. A better understanding of ketamine's molecular targets and antidepressant mechanisms should shed light on the future development of better treatment for depression. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.

Major challenges in youth psychopathology: treatment-resistant depression. A narrative review

Major depressive disorder (MDD) represents a major health issue in adolescents and young adults, leading to high levels of disability and profoundly impacting overall functioning. The clinical presentation of MDD in this vulnerable age group may slightly differ from what can be observed in adult populations, and psychopharmacological strategies do not always lead to optimal response. Resistance to antidepressant treatment has a prevalence estimated around 40% in youths suffering from MDD and is associated with higher comorbidity rates and suicidality. Several factors, encompassing biological, environmental, and clinical features, may contribute to the emergence of treatment-resistant depression (TRD) in adolescents and young adults. Furthermore, TRD may underpin the presence of an unrecognized bipolar diathesis, increasing the overall complexity of the clinical picture and posing major differential diagnosis challenges in the clinical practice. After summarizing current evidence on epidemiological and clinical correlates of TRD in adolescents and young adults, the present review also provides an overview of possible treatment strategies, including novel fast-acting antidepressants. Despite these pharmacological agents are promising in this population, their usage is expected to rely on risk-benefit ratio and to be considered in the context of integrated models of care.

Engaging Mood Brain Circuits with Psilocybin (EMBRACE): a study protocol for a randomized, placebo-controlled and delayed-start, neuroimaging trial in depression

BACKGROUND

Major depressive disorder (MDD) is a leading cause of disability worldwide across domains of health and cognition, affecting overall quality of life. Approximately one third of individuals with depression do not fully respond to treatments (e.g., conventional antidepressants, psychotherapy) and alternative strategies are needed. Recent early phase trials suggest psilocybin may be a safe and efficacious intervention with rapid-acting antidepressant properties. Psilocybin is thought to exert therapeutic benefits by altering brain network connectivity and inducing neuroplastic changes that endure for weeks post-treatment. Although early clinical results are encouraging, psilocybin's acute neurobiological effects on neuroplasticity have not been fully investigated. We aim to examine for the first time how psilocybin acutely (intraday) and subacutely (weeks) alters functional brain networks implicated in depression.

METHODS

Fifty participants diagnosed with MDD or persistent depressive disorder (PDD) will be recruited from a tertiary mood disorders clinic and undergo 1:1 randomization into either an experimental or control arm. Participants will be given either 25 mg psilocybin or 25 mg microcrystalline cellulose (MCC) placebo for the first treatment. Three weeks later, those in the control arm will transition to receiving 25 mg psilocybin. We will investigate whether treatments are associated with changes in arterial spin labelling and blood oxygenation level-dependent contrast neuroimaging assessments at acute and subacute timepoints. Primary outcomes include testing whether psilocybin demonstrates acute changes in (1) cerebral blood flow and (2) functional brain activity in networks associated with mood regulation and depression when compared to placebo, along with changes in MADRS score over time compared to placebo. Secondary outcomes include changes across complementary clinical psychiatric, cognitive, and functional scales from baseline to final follow-up. Serum peripheral neurotrophic and inflammatory biomarkers will be collected at baseline and follow-up to examine relationships with clinical response, and neuroimaging measures.

DISCUSSION

This study will investigate the acute and additive subacute neuroplastic effects of psilocybin on brain networks affected by depression using advanced serial neuroimaging methods. Results will improve our understanding of psilocybin's antidepressant mechanisms versus placebo response and whether biological measures of brain function can provide early predictors of treatment response.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT06072898. Registered on 6 October 2023.

Ketamine and electroconvulsive therapy for severe depression: A network meta-analysis of efficacy and safety

BACKGROUND

Ketamine, electroconvulsive therapy (ECT), and their combination are effective for treating severe depression, but few large-scale studies have compared these.

METHODS

We searched databases for randomized controlled trials (RCTs) using ketamine, ECT, ketamine + ECT, or placebo for severe depression. Standardized measures were efficacy outcomes. Risk of bias was assessed. Stata and ADDIS were used for network meta-analysis (NMA) comparing efficacy and adverse reactions post-treatment. This study was registered on PROSPERO (CRD42023476740).

RESULTS

17 RCTs with 1370 patients were included. NMA showed ECT and ketamine improved Hamilton Depression Rating Scale (HDRS) versus placebo; other comparisons not significant. Rank probabilities showed highest probability for ECT, followed by ketamine + ECT, ketamine, placebo. No differences in Montgomery-Asberg Depression Rating Scale (MADRS); highest rank probability again for ECT, followed by ketamine + ECT, ketamine, placebo.

CONCLUSIONS

Analysis suggests ECT superior to ketamine and their combination for improving depressive severity, but individualized treatment selection warranted. Higher adverse reactions with ketamine + ECT need further study for optimized combined use.

Efficacy of intravenous ketamine and intranasal esketamine with dose escalation for Major depression: A systematic review and meta-analysis

OBJECTIVE

Intravenous (IV) racemic ketamine and intranasal (IN) esketamine have demonstrated rapid antidepressant effects in treatment-resistant depression (TRD). This systematic review aims to evaluate the efficacy and safety of ketamine and esketamine at various dosages for depression.

METHODS

We included randomized controlled trials (RCTs) with parallel group dose comparison of ketamine and esketamine for depression/TRD. Ovid Medline, Embase, PsycINFO, Scopus and Cochrane databases were searched. Standardized mean differences were calculated using Hedges'-g to complete random effects meta-analysis. The efficacy outcomes were changes in depression outcomes for IV ketamine and IN esketamine respectively. Safety was assessed by reported adverse effects.

RESULTS

A random effects meta-analysis of studies (n = 12) showed efficacy in reducing depression symptoms with IV ketamine (Hedges'g = 1.52 [0.98-2.22], Z = 4.23, p < 0.001) and IN esketamine (Hedges' g = 0.31 [0.18-0.44], Z = 4.53, P < 0.001) compared to control/placebo. Treatment response was observed at IV ketamine doses ≤0.2 mg/kg, >0.2-0.5 mg/kg and > 0.5 mg/kg. Higher IV ketamine doses (>0.5 mg/kg) did not lead to greater treatment response. Esketamine doses of 56-84 mg were superior to 28 mg dose.

LIMITATIONS

Overall quality of evidence was low and limited by small number of studies. Publication bias was high.

CONCLUSIONS

This meta-analysis suggests that IV ketamine may be efficacious at doses as low as 0.2 mg/kg, with increasing dose response at 0.5 mg/kg, without demonstrable increased benefit at 1 mg/kg, based on a small number of studies. Efficacy for IN esketamine increases with doses above 28 mg with best response being found between 56 and 84 mg for reducing depressive symptoms.

Subanesthetic S-ketamine does not acutely alter striatal dopamine transporter binding in healthy Sprague Dawley female rats

Major depressive disorder is one of the most prevalent mental health disorders, posing a global socioeconomic burden. Conventional antidepressant treatments have a slow onset of action, and 30% of patients show no clinically significant treatment response. The recently approved fast-acting antidepressant S-ketamine, an N-methyl-D-aspartate receptor antagonist, provides a new approach for treatment-resistant patients. However, knowledge of S-ketamine's mechanism of action is still being established. Depressed human subjects have lower striatal dopamine transporter (DAT) availability compared to healthy controls. Rodent studies report increased striatal dopamine concentration in response to acute ketamine administration. In vivo [18F]FE-PE2I ([18F]-(E)-N-(3-iodoprop-2-enyl)-2β-carbofluoroethoxy-3β-(4'-methyl-phenyl) nortropane) positron emission tomography (PET) imaging of the DAT has not previously been applied to assess the effect of acute subanesthetic S-ketamine administration on DAT availability. We applied translational in vivo [18F]FE-PE2I PET imaging of the DAT in healthy female rats to evaluate whether an acute subanesthetic intraperitoneal dose of 15 mg/kg S-ketamine alters DAT availability. We also performed [3H]GBR-12935 autoradiography on postmortem brain sections. We found no effect of acute S-ketamine administration on striatal DAT binding using [18F]FE-PE2I PET or [3H]GBR-12935 autoradiography. This negative result does not support the hypothesis that DAT changes are associated with S-ketamine's rapid antidepressant effects, but additional studies are warranted.

Experiences of Awe Mediate Ketamine's Antidepressant Effects: Findings From a Randomized Controlled Trial in Treatment-Resistant Depression

Background

Ketamine, an NMDA receptor antagonist, provides rapid antidepressant effects. Although much research has focused on neural and molecular mechanisms of action, it is critical to also consider psychological mechanisms that may contribute to its therapeutic efficacy. The construct of an awe-inducing experience, which is a well-validated psychological phenomenon tied to emotional well-being, had not been applied previously in ketamine research.

Methods

One hundred sixteen participants with depression, 77 of whom received a ketamine infusion (0.5 mg/kg over 40 minutes) and 39 patients who received saline placebo, completed a validated measure of awe (the Awe Experience Scale [AWE-S]) at 40 minutes postinfusion. AWE-S scores were examined as potential mediators of depression outcomes (% improvement in Montgomery-Åsberg Depression Rating Scale score) at 5 postinfusion time points (24 hours and 5, 12, 21, and 30 days). Dissociative effects, measured by Clinician-Administered Dissociative States Scale scores, were tested in parallel mediation models for comparison.

Results

We found that the psychological experience of awe was strongly reported by participants during ketamine infusion, but not saline infusion, and there were significant associations between total AWE-S scores and Montgomery-Åsberg Depression Rating Scale score improvement (% change) in the ketamine arm at all 5 time points. Furthermore, at all 5 time points, total AWE-S scores statistically mediated the relationship between ketamine and Montgomery-Åsberg Depression Rating Scale scores. By contrast, Clinician-Administered Dissociative States Scale scores did not mediate outcomes at any time point.

Conclusions

Ketamine infusion strongly induced heightened feelings of awe, and these experiences consistently mediated depression outcomes over a 1- to 30-day period, unlike general dissociative side effects. The specific awe-inspiring properties of ketamine may contribute to its antidepressant effects.

Number needed to treat (NNT) for ketamine and esketamine in adults with treatment-resistant depression: A systematic review and meta-analysis

BACKGROUND

Ketamine has been established as efficacious in adults living with Treatment-resistant Depression (TRD). Toward providing a quantifiable estimate of the clinical meaningfulness of the therapeutic benefit of ketamine, herein, we conduct a systematic review that aims to report the Number Needed to Treat (NNT) and the Number Needed to Harm (NNH).

METHODS

This systematic review searched Embase, Medline/Pubmed, PsycINFO and ClinicalTrials.gov from inception up to October 15th 2023, for placebo-controlled, Randomized Controlled Trials (RCTs) assessing racemic ketamine or esketamine therapy for unipolar TRD. We calculated NNT and NNH for ketamine treatments over various time points.

RESULTS

A total of 21 studies with 2042 participants were included. Racemic ketamine treatments had pooled NNTs for response of 7 at 4 h, 3 from one day to one week and 9 for studies at four weeks. Esketamine treatment was found to have a similar efficacy with an NNT of 2 at one day and 11 at four weeks. NNH values indicated low risk for ketamine treatments.

LIMITATIONS

Limitations in the data used include the possibility of functional unblinding and selective reporting bias. Moreover, the meta-analysis may have been limited in its precision by including low threshold definitions of treatment resistance (≥ 1 failed antidepressant) and low-dose ketamine treatments.

CONCLUSION

Herein, we determined that the NNT for ketamine treatment in adults living with TRD across different intervals of observation was <10. We conclude that the NNTs observed herein are highly clinically meaningful in this difficult to treat disorder.

Negative emotionality shapes the modulatory effects of ketamine and lamotrigine in subregions of the anterior cingulate cortex

Neuroimaging studies have identified the anterior cingulate cortex (ACC) as one of the major targets of ketamine in the human brain, which may be related to ketamine's antidepressant (AD) mechanisms of action. However, due to different methodological approaches, different investigated populations, and varying measurement timepoints, results are not consistent, and the functional significance of the observed brain changes remains a matter of open debate. Inhibition of glutamate release during acute ketamine administration by lamotrigine provides the opportunity to gain additional insight into the functional significance of ketamine-induced brain changes. Furthermore, the assessment of trait negative emotionality holds promise to link findings in healthy participants to potential AD mechanisms of ketamine. In this double-blind, placebo-controlled, randomized, single dose, parallel-group study, we collected resting-state fMRI data before, during, and 24 h after ketamine administration in a sample of 75 healthy male and female participants who were randomly allocated to one of three treatment conditions (ketamine, ketamine with lamotrigine pre- treatment, placebo). Spontaneous brain activity was extracted from two ventral and one dorsal subregions of the ACC. Our results showed activity decreases during the administration of ketamine in all three ACC subregions. However, only in the ventral subregions of the ACC this effect was attenuated by lamotrigine. 24 h after administration, ACC activity returned to baseline levels, but group differences were observed between the lamotrigine and the ketamine group. Trait negative emotionality was closely linked to activity changes in the subgenual ACC after ketamine administration. These results contribute to an understanding of the functional significance of ketamine effects in different subregions of the ACC by combining an approach to modulate glutamate release with the assessment of multiple timepoints and associations with trait negative emotionality in healthy participants.

Functional changes in sleep-related arousal after ketamine administration in individuals with treatment-resistant depression

The glutamatergic modulator ketamine is associated with changes in sleep, depression, and suicidal ideation (SI). This study sought to evaluate differences in arousal-related sleep metrics between 36 individuals with treatment-resistant major depression (TRD) and 25 healthy volunteers (HVs). It also sought to determine whether ketamine normalizes arousal in individuals with TRD and whether ketamine's effects on arousal mediate its antidepressant and anti-SI effects. This was a secondary analysis of a biomarker-focused, randomized, double-blind, crossover trial of ketamine (0.5 mg/kg) compared to saline placebo. Polysomnography (PSG) studies were conducted one day before and one day after ketamine/placebo infusions. Sleep arousal was measured using spectral power functions over time including alpha (quiet wakefulness), beta (alert wakefulness), and delta (deep sleep) power, as well as macroarchitecture variables, including wakefulness after sleep onset (WASO), total sleep time (TST), rapid eye movement (REM) latency, and Post-Sleep Onset Sleep Efficiency (PSOSE). At baseline, diagnostic differences in sleep macroarchitecture included lower TST (p = 0.006) and shorter REM latency (p = 0.04) in the TRD versus HV group. Ketamine's temporal dynamic effects (relative to placebo) in TRD included increased delta power earlier in the night and increased alpha and delta power later in the night. However, there were no significant diagnostic differences in temporal patterns of alpha, beta, or delta power, no ketamine effects on sleep macroarchitecture arousal metrics, and no mediation effects of sleep variables on ketamine's antidepressant or anti-SI effects. These results highlight the role of sleep-related variables as part of the systemic neurobiological changes initiated after ketamine administration. Clinical Trials Identifier: NCT00088699.

Effects of melancholic features on positive and negative suicidal ideation in patients with treatment-resistant depression and strong suicidal ideation receiving low-dose ketamine infusion

The role of melancholic features on the antisuicidal effect of 0.5 mg/kg ketamine infusion has remained unclear in patients with treatment-resistant depression (TRD) and strong suicidal ideation (SI). Whether ketamine diminishes suicidal ideation in patients with TRD-SI was also unknown. We enrolled 84 patients with TRD-SI, including 27 with melancholic features and 57 without, and then randomly administered a single infusion of 0.5 mg/kg ketamine or 0.045 mg/kg midazolam. The clinician-rated Montgomery-Åsberg Depression Rating Scale (MADRS) item 10, Columbia Suicide Severity Rating Scale-Ideation Severity Subscale (CSSRS-ISS), and self-reported Positive and Negative Suicide Ideation Inventory (PANSI) were used to assess suicidal symptoms from baseline to day 7. Generalized estimating equation models showed that only patients without melancholic features (MADRS item 10: infusion group effect, p = 0.017; CSSRS-ISS: infusion group × time effect, p = 0.008; PANSI-negative suicidal ideation: infusion group effect, p = 0.028) benefited from the antisuicidal effect of low-dose ketamine. The PANSI-positive ideation scores were higher in the ketamine group than in the midazolam group (p = 0.038) for patients with melancholic features. Additional studies are necessary to clarify the neuromechanisms underlying the ketamine-related positive effect against SI and antisuicidal effects among patients with TRD-SI. Additional studies are necessary to clarify the neuromechanisms underlying the ketamine-related positive effect against SI and antisuicidal effects among patients with TRD-SI.

A Multimodal Preclinical Assessment of MDMA in Female and Male Rats: Prohedonic, Cognition Disruptive, and Prosocial Effects

Background

Frontline antidepressants such as selective serotonin reuptake inhibitors (SSRIs) leave many patients with unmet treatment needs. Moreover, even when SSRIs reduce depressive symptoms, anhedonia, the loss of pleasure to previously rewarding activities, often remains unabated. This state of affairs is disheartening and calls for the development of medications to more directly treat anhedonia. The atypical psychedelic 3,4-methylenedioxymethamphetamine (MDMA) might have promise as a prohedonic medication given its efficacious applications for treatment-resistant post-traumatic stress disorder and comorbid depression. However, in addition to its prosocial effects as an entactogen, MDMA is also associated with neurotoxic cognitive deficits. The present studies were designed to examine the relative potency of MDMA in female and male rats across three distinct behavioral domains to assist in defining a preclinical profile of MDMA as a candidate prohedonic therapeutic.

Methods

First, signal detection metrics of reward responsivity were examined using the touchscreen probabilistic reward task (PRT), a reverse-translated assay used to objectively quantify anhedonic phenotypes in humans. Second, to probe potential cognitive deficits, touchscreen-based assays of psychomotor vigilance and delayed matching-to-position were used to examine attentional processes and short-term spatial memory, respectively. Finally, MDMA's entactogenic effects were studied via pairwise assessments of social interaction facilitated by machine-learning analyses.

Results

Findings show (1) dose-dependent increases in reward responsivity as quantified by the PRT, (2) dose-dependent deficits in attention and short-term memory, and (3) dose-dependent increases in aspects of prosocial interaction in male but not female subjects. Neither the desirable (prohedonic) nor undesirable (cognition disruptive) effects of MDMA persisted beyond 24 h.

Conclusions

The present results characterize MDMA as a promising prohedonic treatment, notwithstanding some liability for short-lived cognitive impairment following acute administration.

Molecular signatures of astrocytes and microglia maladaptive responses to acute stress are rescued by a single administration of ketamine in a rodent model of PTSD

Stress affects the brain and alters its neuroarchitecture and function; these changes can be severe and lead to psychiatric disorders. Recent evidence suggests that astrocytes and microglia play an essential role in the stress response by contributing to the maintenance of cerebral homeostasis. These cells respond rapidly to all stimuli that reach the brain, including stressors. Here, we used a recently validated rodent model of post-traumatic stress disorder in which rats can be categorized as resilient or vulnerable after acute inescapable footshock stress. We then investigated the functional, molecular, and morphological determinants of stress resilience and vulnerability in the prefrontal cortex, focusing on glial and neuronal cells. In addition, we examined the effects of a single subanesthetic dose of ketamine, a fast-acting antidepressant recently approved for the treatment of resistant depression and proposed for other stress-related psychiatric disorders. The present results suggest a prompt glial cell response and activation of the NF-κB pathway after acute stress, leading to an increase in specific cytokines such as IL-18 and TNF-α. This response persists in vulnerable individuals and is accompanied by a significant change in the levels of critical glial proteins such as S100B, CD11b, and CX43, brain trophic factors such as BDNF and FGF2, and proteins related to dendritic arborization and synaptic architecture such as MAP2 and PSD95. Administration of ketamine 24 h after the acute stress event rescued many of the changes observed in vulnerable rats, possibly contributing to support brain homeostasis. Overall, our results suggest that pivotal events, including reactive astrogliosis, changes in brain trophic factors, and neuronal damage are critical determinants of vulnerability to acute traumatic stress and confirm the therapeutic effect of acute ketamine against the development of stress-related psychiatric disorders.