Ketamine for Treatment-Resistant Mood Disorders

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.

Case report: Effectiveness of brexpiprazole and esketamine/ketamine combination: A novel therapeutic strategy in five cases of treatment-resistant depression

A significant proportion of patients with treatment-resistant depression do not attain functional recovery despite administration of multiple steps of pharmacotherapeutic strategies. This highlights the elusiveness of meeting unmet needs in existing pharmacotherapies for treatment-resistant depression. There is accumulating evidence that antidepressant agents involving the glutamatergic system such as brexpiprazole and esketamine/ketamine have more rapid onset of action and potentially improved effectiveness as an augmentation therapy in treatment-resistant depression. This case series aimed to report five complex cases of unipolar and bipolar treatment-resistant depression where conventional treatment strategies were inadequate in managing high risk suicidal behavior and achieving functional recovery. We discussed further the possible synergistic mechanisms of the novel combination strategy of brexpiprazole and esketamine/ketamine, clinical and patient factors that influenced treatment response, challenges with this combination strategy and implications for future practice and research.

Gut Microbiota in Depression: A Focus on Ketamine

According to the WHO, major depressive disorder is the leading cause of disability worldwide, and it is a major contributor to the overall global burden of disease. The pathophysiology of this common and chronic disease is still not completely understood. The gut microbiome is an increasingly recognized environmental factor that can have a role in depression, acting through the gut-microbiota-brain axis. The available treatment for depression is still insufficient since 30% of patients are treatment-resistant. There is an unquestionable need for novel strategies. Ketamine is an effective antidepressant in treatment-resistant patients. It is suggested that the antidepressant effect of ketamine may be partially mediated by the modification of gut microbiota. In this study, we presented a review of data on gut microbiota in depression with special attention to the effect of ketamine on the microbiome in animal models of depression. Earlier reports are preliminary and are still insufficient to draw firm conclusion, but further studies in this field might help to understand the role of the gut-brain axis in the treatment of depression and might be the ground for developing new effective treatment strategies.

Co-administration of cannabidiol and ketamine induces antidepressant-like effects devoid of hyperlocomotor side-effects

BACKGROUND AND PURPOSE

Although useful as a rapid-acting antidepressant drug, ketamine is known to induce psychotomimetic effects, which may interfere with its therapeutic use. Cannabidiol (CBD) is a non-psychostimulant compound from Cannabis sativa, which has shown promising antidepressant effects without inducing hyperlocomotion. AMPA receptor activation is involved in the antidepressant effect induced by ketamine, but its relevance for the effects of CBD is not known. Moreover, given that CBD has antipsychotic and antidepressant properties, it is unknown whether adding CBD to ketamine could potentiate the antidepressant properties of ketamine while also attenuating its psychostimulant effects.

EXPERIMENTAL APPROACH

S-Ketamine (2.5, 3, 5, 10, 30 mg/kg) and cannabidiol (3, 10, 30 mg/kg) were administered alone or in combination to male Swiss mice. Independent groups received NBQX (AMPA receptor antagonist) 5 min before administration of CBD or S-ketamine. The antidepressant-like effect was assessed in the forced swimming test (FST), and the open field test (OFT) evaluated the psychostimulant effect.

KEY RESULTS

CBD induced significant dose-dependent antidepressant effects without causing hyperlocomotion in the OFT. S-ketamine produced an antidepressant effect associated with hyperlocomotion in the higher dose. NBQX inhibited the antidepressant effect of both ketamine and CBD. Pretreatment with CBD (10 mg/kg) attenuated the ketamine-induced hyperlocomotion while preserving its antidepressant effect.

CONCLUSION

AND IMPLICATIONS: Similar to ketamine, the antidepressant-like effect elicited by CBD involves AMPA receptor activation. Additionally, CBD prevents the hyperlocomotion induced by S-ketamine without affecting its antidepressant-like effect. Our findings suggest that CBD and ketamine's combined administration can be a promising therapeutic strategy for achieving an appropriate antidepressant effect without unwanted side-effects. This article is part of the special issue on 'Cannabinoids'.

Intra-prefrontal cyclosporine potentiates ketamine-induced fear extinction in rats

Several brain regions, including the medial prefrontal cortex (mPFC), are important in the process of fear extinction learning. Ketamine is a glutamate N-methyl-D-aspartate (NMDA) receptor antagonist, which is shown to play a role in extinction modulation. Ketamine and calcineurin (CN), an intracellular protein phosphatase, have several common targets in the cells. Therefore, in the present study, our aim is to investigate the possible role of calcineurin in the mPFC on the enhancing effects of ketamine in fear extinction. First, different doses of a CN inhibitor, cyclosporine-A (CsA), were micro-injected into the infralimbic (IL) region of the mPFC prior to extinction training in a classical conditioning model in rats. Next, sub-effective doses of CsA (Intra-mPFC) and ketamine (i.p.) were co-administered in another cohort of rats to find their possible interactions. Enzymatic activity of calcineurin was measured in the IL-mPFC following drug administration. We used the elevated plus-maze (EPM) and open field (OF) test for further behavioral assessments. The results showed that CsA can enhance the extinction of conditioned fear and inhibit the enzyme CN at a dose of 20 nM. The combination of sub-effective doses of CsA (5 nM) and ketamine (10 mg/kg) could again enhance the extinction of fear and reduce CN activity in the region. Our results propose that inhibition of CN in the IL-mPFC is involved in the extinction of fear and ketamine enhancement of extinction is probably mediated by reducing CN activity in this part of the brain.

The Immunology of Stress and the Impact of Inflammation on the Brain and Behavior

Exposure to acute versus chronic stressors and threats activates the immune system in adaptive and maladaptive manners, respectively. While acute activation of the immune system in response to threat is homeostatically regulated by glucocorticoid negative feedback, chronic activation of the immune system arising from persistent stress exposure can contribute to an allostatic load with an inflammatory diathesis that has been implicated in stress-related psychopathology, including of depression and anxiety. Increased inflammation in the periphery and in the brain arising from chronic stress exposure can alter neurotransmitter metabolism and impact activation of brain regions to increase adverse behavioral health symptoms (e.g. anhedonia, anxiety, fatigue) and emotion dysregulation. While interventions targeting the immune system and its downstream effects on the brain for the treatment of depression and other psychiatric disorders has been of great interest as they have shown some efficacy in treating stress-related behavioral health disorders, future studies are necessary to better characterize the contexts under which anti-inflammatory agents should be used to treat stress-related psychopathology.

Functional connectivity between the amygdala and subgenual cingulate gyrus predicts the antidepressant effects of ketamine in patients with treatment-resistant depression

Aim

Approximately one‐third of patients with major depressive disorder develop treatment‐resistant depression. One‐third of patients with treatment‐resistant depression demonstrate resistance to ketamine, which is a novel antidepressant effective for this disorder. The objective of this study was to examine the utility of resting‐state functional magnetic resonance imaging for the prediction of treatment response to ketamine in treatment‐resistant depression.

Methods

An exploratory seed‐based resting‐state functional magnetic resonance imaging analysis was performed to examine baseline resting‐state functional connectivity differences between ketamine responders and nonresponders before treatment with multiple intravenous ketamine infusions.

Results

Fifteen patients with treatment‐resistant depression received multiple intravenous subanesthetic (0.5 mg/kg/40 minutes) ketamine infusions, and nine were identified as responders. The exploratory resting‐state functional magnetic resonance imaging analysis identified a cluster of significant baseline resting‐state functional connectivity differences associating ketamine response between the amygdala and subgenual anterior cingulate gyrus in the right hemisphere. Using anatomical region of interest analysis of the resting‐state functional connectivity, ketamine response was predicted with 88.9% sensitivity and 100% specificity. The resting‐state functional connectivity of significant group differences between responders and nonresponders retained throughout the treatment were considered a trait‐like feature of heterogeneity in treatment‐resistant depression.

Conclusion

This study suggests the possible clinical utility of resting‐state functional magnetic resonance imaging for predicting the antidepressant effects of ketamine in treatment‐resistant depression patients and implicated resting‐state functional connectivity alterations to determine the trait‐like pathophysiology underlying treatment response heterogeneity in treatment‐resistant depression.

This study illustrates that the alteration in the RSFC within the right AN in TRD patients reflects the antidepressant response to ketamine at baseline. The alteration remained throughout the 2‐week treatment with multiple ketamine infusions and seemed to reflect the trait‐like features underlying treatment heterogeneity in TRD. By employing an anatomical ROI of the sc/sgACC, the present study also suggests the possible clinical utility of the rsfMRI to predict the treatment response to ketamine in TRD patients.

Case Report: Unexpected Remission From Extreme and Enduring Bulimia Nervosa With Repeated Ketamine Assisted Psychotherapy

Background: Bulimia nervosa is a disabling psychiatric disorder that considerably impairs physical health, disrupts psychosocial functioning, and reduces overall quality of life. Despite available treatment, less than half of sufferers achieve recovery and approximately a third become chronically ill. Extreme and enduring cases are particularly resistant to first-line treatment, namely antidepressants and cognitive behavioral therapy, and have the highest rate of premature mortality. Here, we demonstrate that in such cases, repeated sessions of ketamine assisted psychotherapy (KAP) is an effective treatment alternative for improving symptoms. Case Presentation: A 21-year-old woman presented with extreme and enduring bulimia nervosa. She reported recurrent binge-eating and purging by self-induced vomiting 40 episodes per day, which proved refractory to both pharmacological and behavioral treatment at the outpatient, residential, and inpatient level. Provided this, her physician recommended repeated KAP as an exploratory and off-label intervention for her eating disorder. The patient underwent three courses of KAP over 3 months, with each course consisting of six sessions scheduled twice weekly. She showed dramatic reductions in binge-eating and purging following the first course of treatment that continued with the second and third. Complete cessation of behavioral symptoms was achieved 3 months post-treatment. Her remission has sustained for over 1 year to date. Conclusions: To our knowledge, this is the first report of repeated KAP used to treat bulimia nervosa that led to complete and sustained remission, a rare outcome for severe and enduring cases, let alone extreme ones. Additionally, it highlights the degree to which KAP can be tailored at the individual level based on symptom severity and treatment response. While its mechanism of action is unclear, repeated KAP is a promising intervention for bulimia nervosa that warrants future research and clinical practice consideration.

The Emerging Role of SGK1 (Serum- and Glucocorticoid-Regulated Kinase 1) in Major Depressive Disorder: Hypothesis and Mechanisms

Major depressive disorder (MDD) is a heterogeneous psychiatric disease characterized by persistent low mood, diminished interests, and impaired cognitive and social functions. The multifactorial etiology of MDD is still largely unknown because of the complex genetic and environmental interactions involved. Therefore, no established mechanism can explain all the aspects of the disease. In this light, an extensive research about the pathophysiology of MDD has been carried out. Several pathogenic hypotheses, such as monoamines deficiency and neurobiological alterations in the stress-responsive system, including the hypothalamic-pituitary-adrenal (HPA) axis and the immune system, have been proposed for MDD. Over time, remarkable studies, mainly on preclinical rodent models, linked the serum- and glucocorticoid-regulated kinase 1 (SGK1) to the main features of MDD. SGK1 is a serine/threonine kinase belonging to the AGK Kinase family. SGK1 is ubiquitously expressed, which plays a pivotal role in the hormonal regulation of several ion channels, carriers, pumps, and transcription factors or regulators. SGK1 expression is modulated by cell stress and hormones, including gluco- and mineralocorticoids. Compelling evidence suggests that increased SGK1 expression or function is related to the pathogenic stress hypothesis of major depression. Therefore, the first part of the present review highlights the putative role of SGK1 as a critical mediator in the dysregulation of the HPA axis, observed under chronic stress conditions, and its controversial role in the neuroinflammation as well. The second part depicts the negative regulation exerted by SGK1 in the expression of both the brain-derived neurotrophic factor (BDNF) and the vascular endothelial growth factor (VEGF), resulting in an anti-neurogenic activity. Finally, the review focuses on the antidepressant-like effects of anti-oxidative nutraceuticals in several preclinical model of depression, resulting from the restoration of the physiological expression and/or activity of SGK1, which leads to an increase in neurogenesis. In summary, the purpose of this review is a systematic analysis of literature depicting SGK1 as molecular junction of the complex mechanisms underlying the MDD in an effort to suggest the kinase as a potential biomarker and strategic target in modern molecular antidepressant therapy.