Glutamatergic receptor and neuroplasticity in depression: Implications for ketamine and rapastinel as the rapid-acting antidepressants

Efficacy of mangiferin, kaempferol, and diosgenin on models of depression: A systematic review and network meta-analysis of rodent studies

BACKGROUND

Mangiferin (MGF), kaempferol (KMP), and diosgenin (DIO) are active compounds extracted from the dried rhizomes of Anemarrhena asphodeloides Bunge. that are proven to have antidepressant activity. However, no studies comprehensively compare and analyze the efficacy of MGF, KMP, and DIO.

METHODS

We searched electronic databases (e.g., Cochrane Library, Embase, Scopus, and PubMed) for studies of three compounds in rodents from inception to October 2024, performing a systematic review and network meta-analysis. We used animal behavioral tests as outcome indicators, including the forced swimming test, tail suspension test, and sucrose preference test.

RESULTS

A total of ten studies were included, involving 440 animals and six interventions. In the forced swimming test, the efficacy of fluoxetine was superior to KMP, MGF, and DIO. In the tail suspension test, DIO was more effective than fluoxetine, MGF, and KMP. In the sucrose preference test, the efficacy of fluoxetine was superior to MGF, DIO, and KMP. Specifically, MGF, KMP, and DIO significantly reduced the immobility time of the FST or TST and increased the sucrose preference index.

CONCLUSIONS

MGF, KMP, and DIO significantly improved depression-like behaviors of rodents, providing evidence for further development of new clinical antidepressants. Also, MGF, KMP, and DIO exert antidepressant effects primarily through anti-inflammatory, anti-oxidative stress, and regulation of neurotrophic factor and neurotransmitter levels.

Berberine: An isoquinoline alkaloid targeting the oxidative stress and gut-brain axis in the models of depression

Depression seriously affects people's quality of life, and there is an urgent need to find novel drugs to cure treatment-resistant depression. Berberine (BBR), extracted from Coptis chinensis Franch., Phellodendron bark, Berberis vulgaris, and Berberis petiolaris, could be a potential multi-target drug for depression. To summarize the effects of BBR on depression in terms of in vitro or in vivo experiments, we searched electronic databases, such as PubMed, Web of Science, Google Scholar, Wanfang Database, and China National Knowledge Infrastructure, from inception until May 2024. Then, we summarize that BBR has indirect antidepressant properties to improve depressive symptoms, manifesting in modulating the gut microbial community, strengthening the intestinal barrier, increasing the abundance of short-chain fatty acid-producing bacteria, and regulating tryptophan metabolism. BBR also exerts antidepressant-like effects via remodulating nuclear factor-erythroid 2-related factor 2/antioxidant response element pathway, hypothalamic-pituitary-adrenal axis, and peroxisome proliferators-activated receptor-delta. Nevertheless, further clinical trials and more high-quality animal studies are needed to show the actual clinical value of BBR for depression.

Mangiferin: A natural neuroprotective polyphenol with anti-inflammatory and anti-oxidant properties for depression

Depression is a severe global health problem accompanied by persistent low mood that harms the physical and mental health of people and places a substantial economic burden on society. Mangiferin (MGF), a natural polyphenol in the traditional Chinese herb Anemarrhena asphodeloides Bge., can improve neuronal damage, memory, and cognitive deficits, implicating the therapeutic potential of MGF for depression. MGF has a unique C-glycosyl and phenolic structure that endows it with multiple biological properties, e.g., anti-oxidant, anti-inflammatory, and anti-mitochondrial dysfunction. However, the pharmacological role of MGF in depression remains unclear. Therefore, this review describes the neuroprotective effects and the antidepressant mechanisms of MGF in preclinical depression studies. MGF ameliorates cognitive deficits in depression and neurodegenerative diseases animal models by reducing amyloid-beta deposition, ameliorating cholinergic dysfunction, and increasing neurotrophic factors. Also, MGF regulates molecular mechanisms in depressed animals mainly through anti-inflammation (by inhibiting NLRP3 inflammasome activation, mitogen-activated protein kinase phosphorylation and its downstream nuclear factor-кB signaling pathway, and indoleamine 2,3-dioxygenase activity), anti-oxidant (by increasing levels of anti-oxidant enzymes and inhibiting lipid peroxidation). Notably, the potential mechanisms of MGF in treating depression by modulating neurotransmission (e.g., glutamate, dopamine, norepinephrine, and serotonin) need to be further explored. It is hoped to explore further the potential molecular mechanisms of MGF's biological activity in depression and provide directions for further clinical applications.

Efficacy of ginsenoside Rg1 on rodent models of depression: A systematic review and meta-analysis

RATIONALE

Depression is a prevalent psychiatric disease, and ginsenoside Rg1 is a bioactive compound extracted from the root of Panax ginseng C.A.Mey. To systematically investigate the effectiveness of Rg1 in rodent models of depression and provide evidence-based references for treating depression.

METHODS

Electronic searches for rodent studies were performed from inception to October 2022, e.g., PUBMED and EMBASE. Data extraction and quality evaluation were performed for the references, and meta-analysis was performed on the selected data using Review Manager 5.3.5. The outcomes were analyzed via a random-effect model and presented as mean difference (MD) with 95% confidence intervals (CIs).

RESULTS

A total of 24 studies and 678 animals were included in this meta-analysis. Rg1 remarkably improved depressive-like symptoms of depressed rodents, including the sucrose preference test (25.08, 95% CI: 20.17-30.00, Z = 10.01, P < 0.00001), forced swimming test (MD = -37.69, 95% CI: (-45.18, -30.2); Z = 9.86, P < 0.00001), and the tail suspension test (MD = -22.93, seconds, 95% CI: (-38.49, -7.37); Z = 2.89, P = 0.004).

CONCLUSIONS

The main antidepressant mechanism of Rg1 was concluded to be the neurotransmitter system, oxidant stress system, and inflammation. Conclusively, this study indicated the possible protective and therapeutic effects of Rg1 for treating depression via multiple mechanisms.

Emerging Viral Infections (ZIKV, SARS-CoV-2, and MPXV) and Depression: Ketamine and (S, R)-Ketamine as Promising Antidepressants

Emerging viral pathogens, newly reported or rapidly evolving viruses, are a significant public health concern worldwide. Beyond their characteristic clinical presentations, emerging viruses, such as monkeypox virus (MPXV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have been increasingly implicated in the development of various neuropsychiatric complications including depression, mainly due to their ability to induce neuroinflammation, immune dysfunction, and neurotransmitter imbalances. Depression is a common mental health condition characterised by continuous low mood or sadness, pessimism, anxiety, and even a tendency to suicide as the main symptoms. Post viral depression commonly shows significant challenges, as traditional antidepressant agents exhibit suboptimal efficacy and prolonged onset of action. Regarding this, ketamine and its enantiomers, S-ketamine and R-ketamine, have recently received increasing attention as potential options in light of their potent and effective antidepressant properties. The present review describes the underlying pathophysiological mechanisms of depression associated with emerging viruses, highlighting the role of neuroinflammation and disturbances inneurotransmitter systems. It also discusses the antidepressant mechanisms of ketamine and its enantiomers, the current clinical evidence demonstrating their effectiveness and safety, especially in the case of treatment-resistant depression, and their growing relevance for mood complications linked to emerging viral infections, including depression. Although preliminary reports propose effectiveness, additional studies are needed to present optimal treatment strategies, long-term safety, and incorporation into clinical practice. Addressing these challenges will be critical for optimising the effectiveness of ketamine- and (S, R)-ketamine-containing therapeutic protocols in treating depression linked to emerging viral infections.

Adjunctive ketamine vs. buprenorphine in co-occurring major depressive disorder and opioid use disorder: a randomized, double-blind clinical trial assessing anxiety symptom severity and craving intensity

BACKGROUND

The concomitant presence of major depressive disorder (MDD) and opioid use disorder (OUD) poses a formidable clinical challenge, warranting effective interventions that address both psychiatric and addictive components.

AIMS

This study sought to compare the efficacy of adjunctive ketamine and buprenorphine in mitigating anxiety symptom severity and craving intensity in individuals with co-occurring MDD and OUD.

METHODS

A randomized, double-blind clinical trial was conducted, involving individuals meeting diagnostic criteria for both MDD and OUD. Participants were randomly assigned to receive adjunctive ketamine or buprenorphine, in conjunction with standard psychiatric and addiction treatments. Anxiety symptom severity and craving intensity were assessed using Hamilton Anxiety Rating Scale (HAM-A), and the Opioid Craving Scale after 2 h, 24 h, and 7 days.

RESULTS

The findings revealed distinct treatment trajectories, with ketamine demonstrating rapid and substantial reduction in anxiety symptom severity within hours of administration, accompanied by a pronounced decline in opioid craving intensity. In contrast, buprenorphine was associated with a more gradual but sustained improvement in anxiety symptoms over several days, paralleled by a modest initial reduction in opioid craving, followed by persistent attenuation.

CONCLUSIONS

In conclusion, this randomized clinical trial provides evidence supporting the efficacy of adjunctive Ketamine and Buprenorphine in reducing anxiety symptoms and craving intensity in patients with co-occurring MDD and OUD.

TRIAL REGISTRATION

IRCT20211214053411N1.

Towards an expanded neurocognitive account of ketamine's rapid antidepressant effects

Ketamine is an N-methyl-D-aspartate receptor antagonist that has shown effectiveness as a rapidly acting treatment for depression. Although advances have been made in understanding ketamine's antidepressant pharmacological and molecular mechanisms of action, the large-scale neurocognitive mechanisms driving its therapeutic effects are less clearly understood. To help provide such a framework, we provide a synthesis of current evidence linking ketamine treatment to the modulation of brain systems supporting reward processing, interoception, and self-related cognition. We suggest that ketamine's antidepressant effects are, at least in part, driven by dynamic multi-level influences across these key functional domains.

Regulation of the microglial polarization for alleviating neuroinflammation in the pathogenesis and therapeutics of major depressive disorder

Major depressive disorder (MDD), as a multimodal neuropsychiatric and neurodegenerative illness with high prevalence and disability rates, has become a burden to world health and the economy that affects millions of individuals worldwide. Neuroinflammation, an atypical immune response occurring in the brain, is currently gaining more attention due to its association with MDD. Microglia, as immune sentinels, have a vital function in regulating neuroinflammatory reactions in the immune system of the central nervous system. From the perspective of steady-state branching states, they can transition phenotypes between two extremes, namely, M1 and M2 phenotypes are pro-inflammatory and anti-inflammatory, respectively. It has an intermediate transition state characterized by different transcriptional features and the release of inflammatory mediators. The timing regulation of inflammatory cytokine release is crucial for damage control and guiding microglia back to a steady state. The dysregulation can lead to exorbitant tissue injury and neuronal mortality, and targeting the cellular signaling pathway that serves as the regulatory basis for microglia is considered an essential pathway for treating MDD. However, the specific intervention targets and mechanisms of microglial activation pathways in neuroinflammation are still unclear. Therefore, the present review summarized and discussed various signaling pathways and effective intervention targets that trigger the activation of microglia from its branching state and emphasizes the mechanism of microglia-mediated neuroinflammation associated with MDD.

MicroRNA-specific targets for neuronal plasticity, neurotransmitters, neurotrophic factors, and gut microbes in the pathogenesis and therapeutics of depression

Depression is of great concern because of the huge burden, and it is impacted by various epigenetic modifications, e.g., histone modification, covalent modifications in DNA, and silencing mechanisms of non-coding protein genes, e.g., microRNAs (miRNAs). MiRNAs are a class of endogenous non-coding RNAs. Alternations in specific miRNAs have been observed both in depressive patients and experimental animals. Also, miRNAs are highly expressed in the central nervous system and can be delivered to different tissues via tissue-specific exosomes. However, the mechanism of miRNAs' involvement in the pathological process of depression is not well understood. Therefore, we summarized and discussed the role of miRNAs in depression. Conclusively, miRNAs are involved in the pathology of depression by causing structural and functional changes in synapses, mediating neuronal regeneration, differentiation, and apoptosis, regulating the gut microbes and the expression of various neurotransmitters and BDNF, and mediating inflammatory and immune responses. Moreover, miRNAs can predict the efficacy of antidepressant medications and explain the mechanism of action of antidepressant drugs and aerobic exercise to prevent and assist in treating depression.

Identification of mitophagy-related genes and analysis of immune infiltration in the astrocytes based on machine learning in the pathogenesis of major depressive disorder

BACKGROUNDS

Major depressive disorder (MDD) is a pervasive mental and mood disorder with complicated and heterogeneous etiology. Mitophagy, a selective autophagy of cells, specifically eliminates dysfunctional mitochondria. The mitochondria dysfunction in the astrocytes is regarded as a critical pathogenetic mechanism of MDD. However, studies on the mitophagy of astrocytes in MDD are scarce. To explore the impact of mitophagy on the astrocytes, we used bioinformatic methods to analyze the correlation between astrocyte-related genes and mitophagy-related genes in MDD.

METHODS

The microarray dataset of MDD was downloaded from the Gene Expression Omnibus database and identified astrocyte- and mitophagy-related differentially expressed genes (AMRDEGs). We used three machine learning algorithms to identify hub AMRDEGs and constructed a diagnostic prediction model. Also, we analyzed transcription factor-gene and gene-microRNA interaction networks, and the immune infiltration in MDD and healthy controls. Besides, we performed consensus clustering analysis, immune infiltration analysis, and gene set variation analysis of MDD samples.

RESULTS

The present research identified 3 hub AMRDEGs (GRN, NDUFAF4, and SNCA), and a good diagnostic model with potential clinical applications was constructed and validated. Besides, we identified 6 transcription factors and 14 microRNAs. The immune infiltration analysis showed that MDD was closely related to immune cells. Gene set variant analysis showed that MDD was related to immune and mitochondrial metabolism and inflammatory signaling pathways.

CONCLUSIONS

We identified 3 hub AMRDEGs, new biomarkers for treating and diagnosing MDD and associated with immuno-inflammation. Our research provides new insights into the early diagnosis and treatment of MDD.

QSPR modeling to predict surface tension of psychoanaleptic drugs using the hybrid DA-SVR algorithm

A robust Quantitative Structure-Property Relationship (QSPR) model was presented to predict the surface tension property of psychoanaleptic (psychostimulant and antidepressant) drugs. A dataset of 112 molecules was utilized, and three feature selection methods were applied: genetic algorithm combined with Ordinary Least Squares (GA-OLS), Partial Least Squares (GA-PLS), and Support Vector Machines (GA-SVM), each identifying ten pertinent AlvaDesc descriptors. The models were constructed using the Dragonfly Algorithm combined with the Support Vector Regressor (DA-SVR), with the GA-SVM-based model emerging as the top performer. Rigorous statistical metrics validate its superior predictive accuracy (R2 = 0.98142, Q2LOO = 0.98142, RMSE = 1.12836, AARD = 0.78746). Furthermore, an external test set of ten compounds was employed for model validation and extrapolation, along with assessing the applicability domain, further underscoring the model's reliability. The selected descriptors (X0Av, VE1sign_B(e), ATSC1e, MATS6v, P_VSA_ppp_A, TDB01u, E1s, R2m+, N-067, SssO) collectively elucidate the key structural factors influencing surface tension in the studied drugs. The model provides excellent predictions and can be used to determine the surface tension of new psychoanaleptic drugs. Its outcomes will guide the design of novel medications with targeted surface tension properties.

A refined formula derived from Jiawei-Xiaoyao pill exerts rapid antidepressant-like effects in LPS-induced depression by reducing neuroinflammation and restoring neuroplasticity signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Jiawei-Xiaoyao Pill (JWX), a classic formula in traditional Chinese medicine, is derived from Xiaoyao Pill by adding significant amounts of Gardeniae Fructus (GF) and Moutan Cortex (MC). It is frequently used for the treatment of depression. JWX has been demonstrated to uniquely elicit rapid antidepressant-like effects within the prescribed dosage range. To date, GF has been shown to have rapid antidepressant-like effects, but a much higher dose is required than its proportion in JWX. It is assumed that the synergism of GF with a minimum number of other herbs in JWX serves as a refined formula that exerts these rapid antidepressant-like effects. Identification of a refined formula is important for prioritizing the herbs and ingredients to optimize the quality control of JWX. However, such a refined formula for JWX has not been identified yet.

AIM OF THE STUDY

Here we aimed to identify a refined formula derived from JWX for optimized rapid antidepressant-like effects. Since the neuroinflammation mechanism involving in depression treatment has not been previously investigated for JWX, we tested the mechanism for both JWX and the refined formula.

MATERIALS AND METHODS

Individual herbs (MC; ASR, Angelica Sinensis Radix; Bupleuri Radix; Paeonia Radix Alba) that show antidepressant-like responses were mixed with GF at the proportional dosage in JWX to identify the refined formula. Rapid antidepressant-like effects were assessed by using NSF (Novelty Suppressed Feeding Test) and other behavioral tests following a single administration. The identified formula was further tested in a lipopolysaccharide (LPS)-induced depressive model, and the molecular signaling mechanisms were investigated using Western blot analysis, immunofluorescence, and pharmacological inhibition of mTOR signaling. Scopolamine (Scop) was used as a positive control for induction of rapid antidepressant effects.

RESULTS

A combination of GF, MC and ASR (GMA) at their dosages proportional to JWX induced behavioral signs of rapid antidepressant-like responses in both normal and LPS-treated mice, with the antidepressant-like effects sustained for 5 d. Similar to JWX or Scop, GMA rapidly reduced the neuroinflammation signaling of Iba-1-NF-кB, enhanced neuroplasticity signaling of CaMKII-mTOR-BDNF, and attenuated the upregulated expressions of the NMDAR sub-units GluN1 and GluN2B in the hippocampus of LPS-treated mice. GMA, JWX and Scop rapidly restored the number of BDNF-positive cells reduced by LPS treatment in the CA3 region of the hippocampus. Furthermore, rapamycin, a selective inhibitor of mTOR, blunted the rapid antidepressant-like effects and hippocampal BDNF signaling upregulation by GMA.

CONCLUSION

GMA may serve as a refined formula from JWX, capable of inducing rapid antidepressant-like effects. In the LPS-induced depression model, the effects of GMA were mediated via rapidly alleviating neuroinflammation and enhancing neuroplasticity.

N-methyl-D-aspartate Receptors and Depression: Linking Psychopharmacology, Pathology and Physiology in a Unifying Hypothesis for the Epigenetic Code of Neural Plasticity

Uncompetitive NMDAR (N-methyl-D-aspartate receptor) antagonists restore impaired neural plasticity, reverse depressive-like behavior in animal models, and relieve major depressive disorder (MDD) in humans. This review integrates recent findings from in silico, in vitro, in vivo, and human studies of uncompetitive NMDAR antagonists into the extensive body of knowledge on NMDARs and neural plasticity. Uncompetitive NMDAR antagonists are activity-dependent channel blockers that preferentially target hyperactive GluN2D subtypes because these subtypes are most sensitive to activation by low concentrations of extracellular glutamate and are more likely activated by certain pathological agonists and allosteric modulators. Hyperactivity of GluN2D subtypes in specific neural circuits may underlie the pathophysiology of MDD. We hypothesize that neural plasticity is epigenetically regulated by precise Ca2+ quanta entering cells via NMDARs. Stimuli reach receptor cells (specialized cells that detect specific types of stimuli and convert them into electrical signals) and change their membrane potential, regulating glutamate release in the synaptic cleft. Free glutamate binds ionotropic glutamatergic receptors regulating NMDAR-mediated Ca2+ influx. Quanta of Ca2+ via NMDARs activate enzymatic pathways, epigenetically regulating synaptic protein homeostasis and synaptic receptor expression; thereby, Ca2+ quanta via NMDARs control the balance between long-term potentiation and long-term depression. This NMDAR Ca2+ quantal hypothesis for the epigenetic code of neural plasticity integrates recent psychopharmacology findings into established physiological and pathological mechanisms of brain function.

Novel insight into astrocyte-mediated gliotransmission modulates the synaptic plasticity in major depressive disorder

Major depressive disorder (MDD) is a form of glial cell-based synaptic dysfunction disease in which glial cells interact closely with neuronal synapses and perform synaptic information processing. Glial cells, particularly astrocytes, are active components of the brain and are responsible for synaptic activity through the release gliotransmitters. A reduced density of astrocytes and astrocyte dysfunction have both been identified the brains of patients with MDD. Furthermore, gliotransmission, i.e., active information transfer mediated by gliotransmitters between astrocytes and neurons, is thought to be involved in the pathogenesis of MDD. However, the mechanism by which astrocyte-mediated gliotransmission contributes to depression remains unknown. This review therefore summarizes the alterations in astrocytes in MDD, including astrocyte marker, connexin 43 (Cx43) expression, Cx43 gap junctions, and Cx43 hemichannels, and describes the regulatory mechanisms of astrocytes involved in synaptic plasticity. Additionally, we investigate the mechanisms acting of the glutamatergic, gamma-aminobutyric acidergic, and purinergic systems that modulate synaptic function and the antidepressant mechanisms of the related receptor antagonists. Further, we summarize the roles of glutamate, gamma-aminobutyric acid, d-serine, and adenosine triphosphate in depression, providing a basis for the identification of diagnostic and therapeutic targets for MDD.

Art therapy and neuroscience: evidence, limits, and myths

The evidence base for the effectiveness of art therapy continues to grow, even as a mechanistic understanding of how art therapy works remains limited. One promising avenue for increasing our understanding of how and why art therapy works is through the lens of neuroscience. A neuroscience-based approach to art therapy provides opportunities for improving understanding of the neural processes that underlie the complex interaction between perception, cognition, emotion and behavior that play out in the art therapy process. Understanding how therapeutic change occurs can result in improved treatment and better outcomes for clients. However, it can be tricky to connect art therapy and psychological theory directly to neural responses. The purposes of this perspective are to provide an overview of the current evidence and limits of neurobiological concepts of neuroplasticity, mirror systems, and interoception as applied to art therapy practice, and to provide updated information about outdated concepts that are still actively used in clinical practice. Critical analysis and understanding of the current scientific knowledge base can then be used to guide art therapy practice and support the development of hypothesis-based research to determine the primary mechanisms that drive the observed effects of art therapy interventions.

Parkin, a Parkinson's disease-associated protein, mediates the mitophagy that plays a vital role in the pathophysiology of major depressive disorder

Depression is a complex mood disorder with multifactorial etiology and is also the most frequent non-motor symptom of Parkinson's disease. Emerging research suggests a potential link between mitochondrial dysfunction and the pathophysiology of major depressive disorder. By synthesizing current knowledge and research findings, this review sheds light on the intricate relationship between Parkin, a protein classically associated with Parkinson's disease, and mitochondrial quality control mechanisms (e.g., mitophagy, mitochondrial biogenesis, and mitochondrial dynamic), specifically focusing on their relevance in the context of depression. Additionally, the present review discusses therapeutic strategies targeting Parkin-medicated mitophagy and calls for further research in this field. These findings suggest promise for the development of novel depression treatments through modulating Parkin-mediated mitophagy.

Pre- and Post-Synaptic protein in the major depressive Disorder: From neurobiology to therapeutic targets

Major depressive disorder (MDD) has demonstrated its negative impact on various aspects of the lives of those affected. Although several therapies have been developed over the years, it remains a challenge for mental health professionals. Thus, understanding the pathophysiology of MDD is necessary to improve existing treatment options or seek new therapeutic alternatives. Clinical and preclinical studies in animal models of depression have shown the involvement of synaptic plasticity in both the development of MDD and the response to available drugs. However, synaptic plasticity involves a cascade of events, including the action of presynaptic proteins such as synaptophysin and synapsins and postsynaptic proteins such as postsynaptic density-95 (PSD-95). Additionally, several factors can negatively impact the process of spinogenesis/neurogenesis, which are related to many outcomes, including MDD. Thus, this narrative review aims to deepen the understanding of the involvement of synaptic formations and their components in the pathophysiology and treatment of MDD.

Pediatric suicide: Review of a preventable tragedy

Concepts of suicide are explored in this issue with a focus on suicide in children and adolescents. The epidemiology of pediatric suicide in the United States is reviewed; also, risk and protective factors, as well as prevention strategies, are discussed. Suicide in the pediatric athlete and the potential protective effect of exercise are examined. In addition, this analysis addresses the beneficial role of psychological management as well as current research on pharmacologic treatment and brain stimulation procedures as part of comprehensive pediatric suicide prevention. Though death by suicide in pediatric persons has been and remains a tragic phenomenon, there is much that clinicians, other healthcare professionals, and society itself can accomplish in the prevention of pediatric suicide as well as the management of suicidality in our children and adolescents.

Impacts of microbiota and its metabolites through gut-brain axis on pathophysiology of major depressive disorder

Major depressive disorder (MDD) is characterized by a high rate of recurrence and disability, which seriously affects the quality of life of patients. That's why a deeper understanding of the mechanisms of MDD pathology is an urgent task, and some studies have found that intestinal symptoms accompany people with MDD. The microbiota-gut-brain axis is the bidirectional communication between the gut microbiota and the central nervous system, which was found to have a strong association with the pathogenesis of MDD. Previous studies have focused more on the communication between the gut and the brain through neuroendocrine, neuroimmune and autonomic pathways, and the role of gut microbes and their metabolites in depression is unclear. Metabolites of intestinal microorganisms (e.g., tryptophan, kynurenic acid, indole, and lipopolysaccharide) can participate in the pathogenesis of MDD through immune and inflammatory pathways or by altering the permeability of the gut and blood-brain barrier. In addition, intestinal microbes can communicate with intestinal neurons and glial cells to affect the integrity and function of intestinal nerves. However, the specific role of gut microbes and their metabolites in the pathogenesis of MDD is not well understood. Hence, the present review summarizes how gut microbes and their metabolites are directly or indirectly involved in the pathogenesis of MDD.

New perspective on sustained antidepressant effect: focus on neurexins regulating synaptic plasticity

Depression is highly prevalent globally, however, currently available medications face challenges such as low response rates and short duration of efficacy. Additionally, depression mostly accompany other psychiatric disorders, further progressing to major depressive disorder without long-term effective management. Thus, sustained antidepressant strategies are urgently needed. Recently, ketamine and psilocybin gained attention as potential sustained antidepressants. Review of recent studies highlights that synaptic plasticity changes as key events of downstream long-lasting changes in sustained antidepressant effect. This underscores the significance of synaptic plasticity in sustained antidepressant effect. Moreover, neurexins, key molecules involved in the regulation of synaptic plasticity, act as critical links between synaptic plasticity and sustained antidepressant effects, involving mechanisms including protein level, selective splicing, epigenetics, astrocytes, positional redistribution and protein structure. Based on the regulation of synaptic plasticity by neurexins, several drugs with potential for sustained antidepressant effect are also discussed. Focusing on neurexins in regulating synaptic plasticity promises much for further understanding underlying mechanisms of sustained antidepressant and the next step in new drug development. This research represents a highly promising future research direction.

Efficacy of Chinese herbal formula Kai-Xin-San on rodent models of depression: A systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Kai-Xin-San (KXS, or Happy Feeling Powder), a typical Chinese herbal prescription, is frequently used for treating depression by the multi-level and multi-target mechanism.

AIM OF THE STUDY

To systematically investigate the efficacy and safety of KXS on depression in preclinic trials.

MATERIALS AND METHODS

We independently searched for preclinical animal studies of KXS on depression from inception to June 28, 2022, using electronic databases, e.g., PUBMED. The measurements were performed to assess the outcomes of behavioral tests.

RESULTS

This systematic review and meta-analysis included twenty-four studies and 608 animals. A remarkable effect of KXS in depression behavioral tests, including sucrose consumption test (SMD: 2.36, 95% CI: (1.81, 2.90); Z = 8.49, P < 0.00001)., forced swimming test (MD = -60.52, 95% CI: (-89.04, -31.99); Z = 4.16, P < 0.0001), rearing times (MD=4.48, 95% CI: (3.39, 5.57); Z = 8.05, P < 0.00001) and crossing times (MD = -33.7, 95% CI: (25.74, 41.67); Z = 8.29, P < 0.00001) in the open field test, showing KXS's excellent efficiency in improving depressive-like symptoms of animals.

CONCLUSIONS

Our meta-analysis showed KXS remarkably relieved animals' depressive-like symptoms, providing evidence that KXS can be a promising drug candidate for depression treatment.

Astroglial Connexin 43-Mediated Gap Junctions and Hemichannels: Potential Antidepressant Mechanisms and the Link to Neuroinflammation

Major depression disorder (MDD) is a neuropsychiatric disorder associated with a high suicide rate and a higher disability rate than any other disease. Evidence suggests that the pathological mechanism of MDD is related to astrocyte dysfunction. Depression is mainly associated with the expression of connexin 43 (Cx43) and the function of Cx43-mediated gap junctions and hemichannels in astrocytes. Moreover, neuroinflammation has been a hotspot in research on the pathology of depression, and Cx43-mediated functions are thought to be involved in neuroinflammation-related depression. However, the specific mechanism of Cx43-mediated functions in neuroinflammation-related depression pathology remains unclear. Therefore, this review summarizes and discusses Cx43 expression, the role of gap junction intercellular communication, and its relationship with neuroinflammation in depression. This review also focuses on the effects of antidepressant drugs (e.g., monoamine antidepressants, psychotropic drugs, and N-methyl-D-aspartate receptor antagonists) on Cx43-mediated function and provides evidence for Cx43 as a novel target for the treatment of MDD. The pathogenesis of MDD is related to astrocyte dysfunction, with reduced Cx43 expression, GJ dysfunction, decreased GJIC and reduced BDNF expression in the depressed brain. The effect of Cx43 on neuroinflammation-related depression involving inflammatory cytokines, glutamate excitotoxicity, and HPA axis dysregulation. Antidepressant drugs targeting Cx43 can effectively relieve depressive symptoms.

Neural plasticity and depression treatment

Depression is one of the most common mental disorders, which can lead to a variety of emotional problems and even suicide at its worst. As this neuropsychiatric disorder causes the patients to suffer a lot and function poorly in everyday life, it is imposing a heavy burden on the affected families and the whole society. Several hypotheses have been proposed to elucidate the pathogenesis of depression, such as the genetic mutations, the monoamine hypothesis, the hypothalamic-pituitary-adrenal (HPA) axis hyperactivation, the inflammation and the neural plasticity changes. Among these models, neural plasticity can occur at multiple levels from brain regions, cells to synapses structurally and functionally during development and in adulthood. In this review, we summarize the recent progresses (especially in the last five years) on the neural plasticity changes in depression under different organizational levels and elaborate different treatments for depression by changing the neural plasticity. We hope that this review would shed light on the etiological studies for depression and on the development of novel treatments.

Mapping metabolite change in the mouse brain after esketamine injection by ambient mass spectrometry imaging and metabolomics

Ketamine is a new, fast, and effective antidepression treatment method; however, the possible dissociation effects, sensory changes, abuse risk, and the inability to accurately identify whether patients have a significant response to ketamine limit its clinical use. Further exploration of the antidepressant mechanisms of ketamine will contribute to its safe and practical application. Metabolites, the products of upstream gene expression and protein regulatory networks, play an essential role in various physiological and pathophysiological processes. In traditional metabonomics it is difficult to achieve the spatial localization of metabolites, which limits the further analysis of brain metabonomics by researchers. Here, we used a metabolic network mapping method called ambient air flow-assisted desorption electrospray ionization (AFADESI)-mass spectrometry imaging (MSI). We found the main changes in glycerophospholipid metabolism around the brain and sphingolipid metabolism changed mainly in the globus pallidus, which showed the most significant metabolite change after esketamine injection. The spatial distribution of metabolic changes was evaluated in the whole brain, and the potential mechanism of esketamine's antidepressant effect was explored in this research.

Ketamine, benzoate, and sarcosine for treating depression

Studies have demonstrated the beneficial therapeutic effects of sarcosine, benzoate, and ketamine (including esketamine and arketamine) on depression. These drugs mainly act by modulating N-methyl-d-aspartate glutamate receptors (NMDARs) and reducing inflammation in the brain. Although ketamine, benzoate, and sarcosine act differently as the antagonists or coagonists of NMDARs, they all have demonstrated efficacy in animal models or human trials. In vitro and in vivo studies have indicated that sarcosine, benzoate, and ketamine exert their anti-inflammatory effects by inhibiting microglial activity. This review summarizes and compares the efficacy of the possible therapeutic mechanisms of sarcosine, benzoate, ketamine, esketamine, and arketamine. These compounds act as both NMDAR modulators and anti-inflammatory drugs and thus can be effective in the treatment of depression.

Antidepressant effects of the traditional Chinese herbal formula Xiao-Yao-San and its bioactive ingredients

BACKGROUND

Depression is one of the most debilitating and severe psychiatric disorders and a serious public health concern. Currently, many treatments are indicated for depression, including traditional Chinese medicinal formulae such as Xiao-Yao-San (XYS), which has effective antidepressant effects in clinical and animal studies.

PURPOSE

To summarize current evidence of XYS in terms of the preclinical and clinical studies and to identify the multi-level, multi-approach, and multi-target potential antidepressant mechanisms of XYS and active components of XYS by a comprehensive search of the related electronic databases.

METHODS

The following electronic databases were searched from the beginning to April 2022: PubMed, MEDLINE, Web of Science, Google Scholar, and China National Knowledge Infrastructure.

RESULTS

This review summarizes the antidepressant mechanisms of XYS and its active ingredients, which are reportedly correlated with monoamine neurotransmitter regulation, synaptic plasticity, and hypothalamic-pituitary-adrenal axis, etc. CONCLUSION: XYS plays a critical role in the treatment of depression by the regulation of several factors, including the monoaminergic systems, hypothalamic-pituitary-adrenal axis, synaptic plasticity, inflammation, brain-derived neurotrophic factor levels, brain-gut axis, and other pathways. However, more clinical and animal studies should be conducted to further investigate the antidepressant function of XYS and provide more evidence and recommendations for its clinical application. Our review provides an overview of XYS and guidance for future research direction.

ERK/mTOR signaling may underlying the antidepressant actions of rapastinel in mice

Rapastinel as the allosteric modulator of N-methyl-D-aspartate receptor (NMDAR) produces rapid antidepressant-like effects dependent on brain-derived neurotrophic factor (BDNF) and VGF (nonacryonimic) release. Herein, we further explore the molecular mechanisms of the antidepressant effects of repeated administration with rapastinel in mice. Our results showed that continuous 3-day rapastinel (5 and 10 mg/kg, i.v.) produced antidepressant-like actions dependent on the increase in extracellular regulated protein kinase (ERK)/mammalian target of rapamycin (mTOR) signaling and downstream substrates p70S6 kinase (p70S6k) and the eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), which may induce the expression of VGF and BDNF in the hippocampus and prefrontal cortex of mice. Furthermore, compared with a single treatment, our data indicated that 3-day repeated rapastinel treatment produced antidepressant-like actions accompanied by potentiation of ERK/mTOR/VGF/BDNF/tropomyosin-related kinase receptor B (TrkB) signaling. Based on previous and our supplementary data that showed the pivotal role of on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in the rapid release of VGF and BDNF and activation of TrkB by a single dose of rapastinel, we postulate that the antidepressant-like effects of single or repeated administration of rapastinel may result in the rapid release of VGF and BDNF or ERK/mTOR signaling pathway-mediated VGF/BDNF/TrkB autoregulatory feedback loop respectively. Our current work adds new knowledge to the molecular mechanisms that underlie the antidepressant-like actions of rapastinel in mice.

Rapastinel accelerates loss of withdrawal signs after repeated morphine and blunts relapse to conditioned place preference

The purpose of the present study was to evaluate the efficacy of rapastinel, an allosteric modulator of NMDA receptor function, to accelerate the loss of opioid withdrawal symptoms and blunt or prevent relapse to morphine conditioned place preference (CPP) in rats. Two studies were conducted. In study 1, adult and adolescent male and female rats were treated with increasing doses of morphine (5 mg/kg, bid to 25 mg/kg bid) for 5 days. On day 6 animals were treated with naloxone (1 mg/kg) and withdrawal was assessed. They were then treated with saline or rapastinel (5 mg/kg) on days 6 and 8, and withdrawal was assessed on day 9. Rapastinel treated animals exhibited significantly lower levels of withdrawal signs on day 9. No sex or age differences were observed. In Study 2, CPP for morphine was established in adult rats (males and females) by 4 daily pairings with saline and morphine (am/pm alternation). They were tested for CPP on day 5, and then treated with rapastinel (5 mg/kg) or saline daily on days 6-10 of extinction. On day 11 they received a final dose of rapastinel or saline followed by extinction trial. On day 12, animals received 1 mg/kg of morphine and were tested for relapse. Rapastinel did not affect extinction of CPP, but rapastinel-treated animals spent significantly less time in the previously morphine-paired side than saline-treated animals during the relapse trial. These findings of accelerated loss of withdrawal signs and blunted relapse to CPP suggest that rapastinel could provide an adjunctive therapy for opioid dependence during initiation of pharmacotherapy for opioid dependence.