Lateral habenula in the pathophysiology of depression

Efficacy and safety of esketamine for smoking cessation among patients diagnosed with lung cancer and major depression disorder: A randomized, placebo-controlled clinical trial

This multicenter, randomized, placebo-controlled, clinical trial was designed to investigate the efficacy and safety of esketamine (ESK) for smoking cessation. The study enrolled a sample of 236 patients diagnosed with lung cancer and major depression disorder (MDD). Treatment included intranasal delivery of ESK or placebo once a week for 8 sessions. The primary outcomes were self-reported and biologically verified continuous abstinence rates at the end of 6 months follow-up visit. The second outcomes were the severity changes of depression and anxiety. The cognitive function, the nicotine dependence, urge to smoke, respiratory symptoms and adverse events were also examined. We found that 8 sessions of ESK treatments significantly improved the self-reported (44.1 %) and biologically verified (28.8 %) continuous abstinence rates. Additionally, the severity of both depression and anxiety was also significantly relieved by ESK delivery. Furthermore, ESK was capable of improving cognitive function of the participants. Finally, the nicotine dependence, urge to smoke and smoking related respiratory symptoms of ESK group were also alleviated at the completion of follow-up. No serious adverse events were observed throughout the study. This clinical trial provides evidence that ESK treatment is efficacious and safe for quitting cigarette smoking among patients with lung cancer and MDD.

The habenula-interpeduncular nucleus-median raphe pathway regulates the outcome of social dominance conflicts in mice

The habenula (Hb) to interpeduncular nucleus (IPN) projection is highly conserved across vertebrates and, in zebrafish, has been shown to regulate the decision between continuing to fight and surrender during social conflict. We have recently shown that, in loser zebrafish, habenular acetylcholine release acts on postsynaptic α7 nicotinic receptors to induce the expression of Ca2+-permeable AMPA receptors on the silent synapses of the IPN neurons that project to the median raphe (MnR). Leveraging this evolutionary conservation, we demonstrate that the disruption of cholinergic transmission from the Hb to the IPN biases mice toward winning social conflicts, whereas optogenetic activation has the opposite effect of biasing toward losing. Further circuit dissection revealed that the losing bias is likely to be mediated via inhibition of serotonin (5-hydroxytryptamine [5-HT]) neurons in the MnR by the IPN.

From memory disorders to the development of depression: A system approach

In this review, a hypothesis explaining the origin and genesis of depression development from the perspective of a holistic functional system of behavioral control is proposed. The core of the functional system is the memory apparatus, on which all other key components of the behavioral control system (sensory information, motivation, reinforcement, and motor activity) are interlocked. In the organization of memory traces (engrams) there are two inputs, sensory and motivational, through which the stimulus-stimulus (S-S) and stimulus-motor (S-R) engrams are formed. These engrams are organized and actualized by means of forward and backward conditional connections between cortical representations of sensory information and motivational structures of the brain. Through feedback connections from reinforcing (emotional) input to the memory apparatus, the S-S and S-R engrams are consolidated or weakened depending on the strength of reward or negative events. Depression begins with a breakdown in memory mechanisms. These breakdowns are related to problems with the three mentioned memory inputs: sensory, motivational, and reinforcing (emotional). Disruptions in sensory and motivational input lead to an inability to form new memory engrams, their actualization and retrieval. This creates difficulty in solving current and past unresolved problems, eliciting more accumulation and increasing difficulties in their solving. Unresolved tasks lead to weakening of the reinforcing input, and further impairment of consolidation of the acting engrams. Another reason for the weakening of reinforcing input is excessive action of directly harmful events or constant chronic stress. The review presents the current literature and some data from our laboratory in favor of each memory input's contribution and their impact on the development of depression, when they are problematic.

Aberrant aversive learning signals in the habenula in remitted patients with recurrent depression

BACKGROUND

Hypersensitivity to punishment is one of the core features of major depressive disorder. Hypersensitivity to punishment has been proposed to originate from aberrant aversive learning. One of the key areas in aversive learning is the habenula. Although evidence for dysfunctional aversive learning in depressed patients is well established, it remains largely unexplored whether this dysfunction and its neural correlates persists during symptomatic remission of depression.

METHODS

Functional MRI data from 36 medication-free remitted patients with recurrent major depressive disorder (MDD) and 27 healthy control subjects participating in a Pavlovian classical conditioning task, were assessed within a computational modeling framework to evaluate temporal difference related activation of the habenula during aversive learning. Furthermore, generalized psychophysiological interaction analyses were performed to assess functional connectivity of the temporal difference signal with the habenula as an a priori region of interest.

RESULTS

Relative to healthy controls, patients showed significantly increased temporal difference related aversive learning activation in the bilateral habenula. This activation was correlated with residual symptoms in the remitted MDD group. Furthermore, patients exhibited decreased functional connectivity between the habenula and the ventral tegmental area compared to controls.

CONCLUSIONS

The increased habenula activity during aversive learning, particularly during the expectation of punishment, along with decreased functional habenula-ventral tegmental area connectivity in remitted MDD patients, reflect hypersensitivity to, and/or inability to regulate, the impact of aversive environmental cues and punishment.

TRIAL REGISTRATION

NTR3768.

A rare variant in GPR156 associated with depression in a Mennonite pedigree causes habenula hyperactivity and stress sensitivity in mice

Major depressive disorder (MDD) is a leading cause of disability worldwide. Risk for MDD is heritable, and the genetic structure of founder populations enables investigation of rare susceptibility alleles with large effect. In an extended Old Order Mennonite family cohort, we identified a rare missense variant in GPR156 (c.1599G>T, p.Glu533Asp) associated with a two-fold increase in the relative risk of MDD. GPR156 is an orphan G protein-coupled receptor localized in the medial habenula, a region implicated in mood regulation. Insertion of a human sequence containing c.1599G>T into the murine Gpr156 locus induced medial habenula hyperactivity and abnormal stress-related behaviors. This work reveals a human variant that is associated with depression, implicates GPR156 as a target for mood regulation, and introduces informative murine models for investigating the pathophysiology and treatment of affective disorders.

Sex-specific habenular dysconnectivity in patients with late-life depression

There are significant sex differences in the prevalence, symptom presentation, treatment response and brain abnormalities of patients with late-life depression (LLD). The functional connectivity of the habenula has been associated with depressive symptoms and cognitive impairments in patients with LLD. However, sex differences in habenular functional connectivity patterns among LLD patients remain unclear. One hundred and fourteen patients with LLD and 75 healthy controls (HCs) were included in the present study. Resting-state functional magnetic resonance imaging was used to analyse the static and dynamic functional connectivity (sFC and dFC) of the habenula. There were significant interactions between diagnosis (LLD vs. HCs) and sex for the dFC of the left habenula with the left insula, precentral gyrus, angular gyrus, and middle frontal gyrus and for the right habenula with the right middle temporal gyrus. Pairwise comparisons revealed a trend of HC males > HC females and LLD males < HC males for the connections between the left habenula and the left precentral gyrus, angular gyrus and middle frontal gyrus. Conversely, a trend of HC males < HC females and LLD males > HC males was found for the connections between the right habenula and right middle temporal pole. Furthermore, there was a significant interaction for the sFC of the right habenula with the right fusiform gyrus, with trends of HC males > HC females, LLD males < HC males, and LLD females > HC females. Regression analysis revealed that left habenular-left insular dFC was associated with long-delay memory in females and working memory in males; right habenular-right middle temporal pole dFC was associated with information processing speed in females. Sex moderated the relationships between cognitive function (global cognition, delay-recalled memory and working memory) and dFC between the left habenula and left insula. In conclusions, this study revealed sex-specific alterations in the functional connectivity patterns of the habenula in LLD patients, and these alterations were associated with various cognitive functions in a sex-specific manner. These findings provide a neurobiological basis for understanding sex differences in LLD patients.

Blockade of mGluR1 and mGluR5 in the lateral habenula produces the opposite effects in the regulation of depressive-like behaviors in the hemiparkinsonian rats

Depression is one of the most common non-motor symptoms in Parkinson's disease (PD) and the hyperactivity of the lateral habenula (LHb) may contribute to depression. The present study was performed to investigate the effects and mechanisms of group I metabotropic glutamate receptors (mGluRs) in the LHb on PD-related depressive-like behaviors. Unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc) were used to establish the PD rat model. The group I mGluRs agonist and antagonists for mGluR1 and mGluR5 were microinjected into the LHb to observe their effects on PD-related depressive-like behaviors, electrical activities of the LHb, release of monoamines in the medial prefrontal cortex (mPFC) in sham and the lesioned rats. Lesions of the SNc induced depressive-like behaviors and hyperactivity of LHb neurons. Activation of group I mGluRs by 3,5-DHPG induced or enhanced depressive-like behaviors, increased the firing rate of the LHb neurons, and decreased dopamine (DA) and serotonin (5-HT) levels in the mPFC in the two groups of rats. Blockade of mGluR1 by YM298198 also produced similar effects with 3,5-DHPG, however, blockade of mGluR5 by MTEP produced opposite effects. Western blotting data showed that lesions of the SNc in rats down-regulated the expression of mGluR1 and mGluR5 in the LHb. These results suggest that mGluR1 and mGluR5 in the LHb induce opposite effects on depressive-like behaviors, which may attribute to the changed firing rate of LHb neurons by the presynaptic and postsynaptic mechanisms, and the changes in the monoamine levels.

Microglia Sing the Prelude of Neuroinflammation-Associated Depression

Major depressive disorder (MDD) is a psychiatric condition characterized by sadness and anhedonia and is closely linked to chronic low-grade neuroinflammation, which is primarily induced by microglia. Nonetheless, the mechanisms by which microglia elicit depressive symptoms remain uncertain. This review focuses on the mechanism linking microglia and depression encompassing the breakdown of the blood-brain barrier, the hypothalamic-pituitary-adrenal axis, the gut-brain axis, the vagus and sympathetic nervous systems, and the susceptibility influenced by epigenetic modifications on microglia. These pathways may lead to the alterations of microglia in cytokine levels, as well as increased oxidative stress. Simultaneously, many antidepressant treatments can alter the immune phenotype of microglia, while anti-inflammatory treatments can also have antidepressant effects. This framework linking microglia, neuroinflammation, and depression could serve as a reference for targeting microglia to treat depression.

Role of phospholipase Cη1 in lateral habenula astrocytes in depressive-like behavior in mice

Phospholipase C (PLC) enzymes play crucial roles in intracellular calcium-signaling transduction. Several brain PLC subtypes have been extensively studied, implicating them in psychiatric disorders such as depression, epilepsy and schizophrenia. However, the role of the recently identified PLCη remains largely unknown. We found that PLCη1 is prominently expressed in lateral habenula (LHb) astrocytes. Here, to investigate its physiological role, we generated astrocyte-specific PLCη1 conditional knockout (cKO) mice (Plch1f/f; Aldh1l1-CreERT2). In these cKO mice, we observed a reduction in cellular morphological complexity metrics, such as total process length, as well as a decrease in the passive membrane conductance of LHb astrocytes. Additionally, neuronal function was impacted by the cKO, as the synaptic efficacy and firing rates of LHb neurons increased, while extrasynaptic long-term depression was impaired. Both tonic α-amino-3-hydroxy-5-methyl-4-isoxazolepdlropionic acid receptor/N-methyl-D-aspartate receptor (AMPAR/NMDAR) currents and extracellular glutamate levels were reduced. Interestingly, chemogenetic activation of astrocytes restored the reduced tonic AMPAR/NMDAR currents in cKO mice. Furthermore, LHb astrocyte-specific deletion of PLCη1 via AAV-GFAP-Cre injection induced depressive-like behaviors in mice, which were reversed by chemogenetic activation of LHb astrocytes. Finally, we found that restraint stress exposure decreased Plch1 mRNA expression in the LHb. These findings suggest that PLCη1 could be a potential therapeutic target for depression and highlight the critical role of astrocytes in the etiology of neuropsychiatric disorders.

Neural circuits mediating chronic stress: Implications for major depressive disorder

Major depressive disorder (MDD), also known as depression, is a prevalent mental disorder that leads to severe disease burden worldwide. Over the past two decades, significant progress has been made in understanding the pathogenesis and developing novel treatments for MDD. Among the complicated etiologies of MDD, chronic stress is a major risk factor. Exploring the underlying brain circuit mechanisms of chronic stress regulation has been an area of active research for recent years. A growing body of preclinical and clinical research has revealed that abnormalities in the brain circuits are closely associated with failures in coping with stress in depressed individuals. Nevertheless, neural circuit mechanisms underlying chronic stress processing and the onset of depression remain a major puzzle. Here, we review recent literature focusing on circuit- and cell-type-specific dissection of depression-like behaviors in chronic stress-related animal models of MDD and outline the key questions.

Quercetin inhibited chronic unpredictable mild stress-induced mouse depressive behaviors through attenuating lateral Habenula neuronal activities

As a flavonoid, quercetin has shown anti-tumor, anti-inflammation, and anti-depressant effects. However, the exact anti-depressant mechanism of quercetin remains unclear. In this study, a combination of behavioral tests and neuropharmacological methods were used to investigate whether the endocannabinoid (eCB) system in the lateral habenula (LHb) mediated the anti-depressant pathogenesis of quercetin. Depressive model was prepared by chronic unpredictable mild stress (CUMS) in C57 mice. The CUMS exposure led to depressive-like behaviors and an increase of the miniature excitatory postsynaptic current (mEPSC) frequency in the LHb neurons, which were blocked by quercetin intragastrically administered for 14 days. As quercetin has been shown to upregulate the mRNA expression of cannabinoid receptor 1 (CB1) in cultured tumor cells, and the inhibitory effect of eCB system activation is related to glutamatergic neurons, depolarization-induced suppression of excitation (sDSE) was detected. The results showed that presynaptic inhibitory effect of eCB system was significantly down-regulated in the LHb of CUMS model, and the down-regulation was abolished by quercetin. Blocking eCB system in the LHb with CB1 antagonist AM251 rescued the neuroprotective effects of quercetin in CUMS mice. Taken together, the results suggested that eCB system in the LHb was involved in the anti-depressant effects of quercetin.

Optogenetics and chemogenetics: key tools for modulating neural circuits in rodent models of depression

Optogenetics and chemogenetics are emerging neuromodulation techniques that have attracted significant attention in recent years. These techniques enable the precise control of specific neuronal types and neural circuits, allowing researchers to investigate the cellular mechanisms underlying depression. The advancement in these techniques has significantly contributed to the understanding of the neural circuits involved in depression; when combined with other emerging technologies, they provide novel therapeutic targets and diagnostic tools for the clinical treatment of depression. Additionally, these techniques have provided theoretical support for the development of novel antidepressants. This review primarily focuses on the application of optogenetics and chemogenetics in several brain regions closely associated with depressive-like behaviors in rodent models, such as the ventral tegmental area, nucleus accumbens, prefrontal cortex, hippocampus, dorsal raphe nucleus, and lateral habenula and discusses the potential and challenges of optogenetics and chemogenetics in future research. Furthermore, this review discusses the potential and challenges these techniques pose for future research and describes the current state of research on sonogenetics and odourgenetics developed based on optogenetics and chemogenetics. Specifically, this study aimed to provide reliable insights and directions for future research on the role of optogenetics and chemogenetics in the neural circuits of depressive rodent models.

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.

Mitogen-activated protein kinase dependent presynaptic potentiation in the lateral habenula mediates depressive-like behaviors in rats

Emerging evidence suggests that the enhanced activity of lateral habenula (LHb) is involved in depressive disorders. This abnormal potentiation of LHb neurons was shown to originate from presynaptic alterations; however, the mechanisms underlying this presynaptic enhancement and physiological consequences are yet to be elucidated. Previously, we reported that presynaptic transmission in the LHb is temporally rhythmic, showing greater activity in the afternoon than in the morning. Here, we used a learned helpless rodent model of depression to show that exposure to a stressor or incubation with the stress hormone, corticosterone, abolished the presynaptic temporal variation in the LHb. In addition, selective inhibition of mitogen-activated protein kinase (MAPK) kinase (MAPKK, MEK) activity in the LHb restored the presynaptic alteration even after stress exposure. Moreover, we observed a slight increase in phosphorylated synapsin I after stress exposure. Finally, we found that a blockade of MAPK signaling before stress exposure successfully prevented the depression-like behaviors, including behavioral despair and helplessness, in an acute learned helpless animal model of depression. Our study delineates the cellular and molecular mechanisms responsible for the abnormal presynaptic enhancement of the LHb in depression, which may mediate depressive behaviors.

5-HT1B receptor activation produces rapid antidepressant-like effects in rodents

Ketamine is noted for its rapid onset antidepressant response and effectiveness in patients with treatment resistant depression. While most research has focused on glutamatergic mechanisms, recent studies show that antidepressant-like effects in rodents are dependent upon the serotonergic (5-HT) system and suggest a potential contribution of the 5-HT1B receptor. In this study we utilized CP-94253 to examine whether 5-HT1B receptor agonism produces rapid and sustained antidepressant-like effects, focusing on rodent models and treatment approaches commonly used to demonstrate the differentiated response to ketamine. We first confirmed that CP-94253 is a potent 5-HT1B agonist in vitro and that CP-94253 occupies brain 5-HT1B receptors at the doses tested. CP-94253 reduced immobility in the mouse forced swim test (FST) and exhibited a prominent antidepressant signature in the mouse-behavior phenotyping platform SmartCube®. When examined 24 h after acute treatment, CP-94253 reduced FST immobility in both naïve rats and in rats receiving chronic interferon alpha treatment. Ex vivo hippocampal long-term potentiation was also enhanced in naïve rats receiving acute CP-94253 treatment, 24 h prior to the recordings. In mice exposed to chronic social defeat stress, antidepressant-like effects in the tail suspension and sucrose preference tests were seen 1 h and 24 h after acute treatment, respectively. Finally, whole brain c-fos imaging in mice showed that CP-94253 modulates neuronal activity in discrete brain regions including the lateral habenula circuit implicated in depression and the ketamine treatment response. Collectively these results support the further investigation of 5-HT1B agonism as a novel treatment approach for major depressive disorder.

Pituitary adenylyl cyclase-activating polypeptide modulates the stress response: the involvement of different brain areas and microglia

Stress is necessary for survival. However, chronic unnecessary stress exposure leads to cardiovascular, gastrointestinal and neuropsychiatric disorders. Thus, understanding the mechanisms involved in the initiation and maintenance of the stress response is essential since it may reveal the underpinning pathophysiology of these disorders and may aid in the development of medication to treat stress-mediated diseases. Pituitary adenylyl cyclase activating polypeptide (PACAP) and its receptors (PAC1, VPAC1 and VPAC2) are expressed in the hypothalamus and other brain areas as well as in the adrenal gland. Previous research has shown that this peptide/receptor system serves as a modulator of the stress response. In addition to modulating the stress response, this system may also be connected to its emerging role as neuroprotective against hypoxia, ischemia, and neurodegeneration. This article aims to review the literature regarding the role of PACAP and its receptors in the stress response, the involvement of different brain regions and microglia in PACAP-mediated modulation of the stress response, and the long-term adaptation to stress recognizable clinically as survival with resilience while manifested in anxiety, depression and other neurobehavioral disorders.

Does lateral habenula mediate effects of gestational stress on rat maternal behavior?

This exploratory study investigated the neural substrate underlying the effect of gestational stress on rat maternal behavior. We tested the hypothesis that the lateral habenula (LHb)-centered neural circuitry (e.g., raphe, ventral tegmental area, nucleus accumbens, etc.) mediates the maternal disruptive effect of gestational stress. Pregnant Sprague-Dawley rats were subjected to daily 30-min restraining stress from approximately gestation day (GD) 5 to 21, white noise from GD 5 to 12 and mild foot shock from GD 13 to 21. Maternal behavior in the home cage and pup retrieval on an elevated plus maze (EPM) were observed during the first postpartum week. The gestational stress reduced body weight gain of stressed females, and reduced time that they spent outside of the nest, a sign of increased maternal anxiety and hypervigilant parenting style. On the open arms of EPM, the stressed dams showed higher frequently sniffing pups than non-stressed ones. Testing with pups (pup exposure) on the EPM decreased c-Fos expression in the LHb in the non-stressed control dams, but it increased c-Fos expression in the dorsal and medial raphe regions of the control dams. Gestational stress reduced this pup effect in all three regions, implying that gestational stress attenuated the ability of pup exposure to activate the maternally relevant brain regions. Our findings indicate that gestational stress may act upon the LHb (as a putative center that mediates negative emotion) and its downstream projection sites (i.e., dorsal and median raphe) to compromise the quality of maternal care.

Lactic acid contributes to the emergence of depression-like behaviors triggered by blue light exposure during sleep

The threat posed by light pollution to human health is increasing remarkably. As demand for high-efficiency and bright lighting increases, so does the blue light content from artificial sources. Although animal studies suggested blue light induced depression-like behaviors, human evidence remained limited, and the mechanisms by which blue light affects depression remained elusive. This study aimed to investigate the association between blue light exposure and depression in humans, and explored the underlying mechanisms that driving depression-like behaviors induced by blue light. Our population findings showed that the high-blue-light exposure at night was positively associated with depressive symptoms. Lactic acid was relevant to depression with Mendelian randomization analysis. Moreover, animal studies demonstrated that exposure to blue light during sleep (BLS) induced depression-like behaviors in the animals. Metabolomics and colorimetric analyses revealed elevated levels of lactic acid in the cerebrospinal fluid and lateral habenula (LHb) of rats with depression-like behaviors induced by BLS. The administration of a lactate inhibitor (Oxamate) alleviated these behaviors, along with changes in neuronal excitability, synaptic function, and morphology in the LHb. Overall, our study suggests that excessive exposure to high blue light-content artificial light at night links to increased depressive symptoms, revealing possible molecular mechanisms and prevention strategies, which are crucial for addressing environmentally related mental health issues.

A New Augmentation Strategy against Depression Combining SSRIs and the N-terminal Fragment of Galanin (1-15)

Depression is one of the most disabling mental disorders, with the second highest social burden; its prevalence has grown by more than 27% in recent years, affecting 246 million in 2021. Despite the wide range of antidepressants available, more than 50% of patients show treatment-resistant depression. In this review, we summarized the progress in developing a new augmentation strategy based on combining the N-terminal fragment of Galanin (1-15) and SSRI-type antidepressants in animal models.

The Potential Role of Dopamine Pathways in the Pathophysiology of Depression: Current Advances and Future Aspects

Depression is a serious mental health disorder that impacts more than 350 million individuals globally. While the roles of serotonin and norepinephrine in depression have been extensively studied, the importance of dopaminergic pathways-essential for mood, cognition, motor control, and endocrine function-often gets overlooked. This review focuses on four major dopamine (DA) circuits: the mesolimbic (MLP), mesocortical (MCP), nigrostriatal (NSP), and thalamictuberoinfundibular pathways (TTFP), and their roles in depression. The MLP, which is key to reward processing, is linked to anhedonia, a primary depression symptom. The MCP, projecting to the prefrontal cortex, affects cognitive issues like impaired attention and decision-making. The NSP, mainly responsible for motor control, is related to psychomotor retardation in depression, while the TTFP manages neuroendocrine responses, which are often disrupted in stress-related depressive conditions. Current antidepressant treatments mainly target serotonin and norepinephrine systems but tend to be less effective for patients with DArgic dysfunction, leading to treatment resistance. This review underscores emerging evidence that suggests targeting DArgic pathways could improve treatment outcomes, especially for symptoms like anhedonia and cognitive deficits that conventional therapies often fail to address. Future research should aim to combine advancements in neuroimaging, optogenetics, and genetic studies to better map DArgic pathways and create personalized treatment plans. This review highlights the potential for new therapies that focus on DA systems, which could pave the way for more effective and tailored approaches to treating depression.

Defects of parvalbumin-positive interneurons are implicated in psychiatric disorders

Psychiatric disorders are a common cause of severe long-term disability and socioeconomic burden worldwide. Although our understanding of these disorders has advanced substantially over the last few years, little has changed the standards of care for these illnesses. Fast-spiking parvalbumin-positive interneurons (PVIs), a subpopulation of gamma-aminobutyric acid (GABA)ergic interneurons, are widely distributed in the hippocampus and have been reported to play an important role in various mental disorders. However, the mechanisms underlying the regulation of the molecular networks relevant to depression and schizophrenia (SCZ) are unknown. Here, we discuss the functions of PVIs in psychiatric disorders, including depression and SCZ. After reviewing several studies, we concluded that dysfunction in PVIs could cause depression-like behavior, as well as cognitive categories in SCZ, which might be mediated in large part by greater synaptic variability. In summary, this scientific review aims to discuss the current knowledge regarding the function of PVIs in depression and SCZ. Moreover, we highlight the importance of neurogenesis and synaptic plasticity in the pathogenesis of depression and SCZ, which seem to be mediated by PVIs activity. These findings provide a better understanding of the role of PVIs in psychiatric disorders.

Nighttime-specific differential gene expression in suprachiasmatic nucleus and habenula is associated with resilience to chronic social stress

The molecular mechanisms that link stress and biological rhythms still remain unclear. The habenula (Hb) is a key brain region involved in regulating diverse types of emotion-related behaviours while the suprachiasmatic nucleus (SCN) is the body's central clock. To investigate the effects of chronic social stress on transcription patterns, we performed gene expression analysis in the Hb and SCN of stress-naïve and stress-exposed mice. Our analysis revealed a large number of differentially expressed genes and enrichment of synaptic and cell signalling pathways between resilient and stress-naïve mice at zeitgeber 16 (ZT16) in both the Hb and SCN. This transcriptomic signature was nighttime-specific and observed only in stress-resilient mice. In contrast, there were relatively few differences between the stress-susceptible and stress-naïve groups across time points. Our results reinforce the functional link between circadian gene expression patterns and differential responses to stress, thereby highlighting the importance of temporal expression patterns in homoeostatic stress responses.

The involvement of K+ channels in depression and pharmacological effects of antidepressants on these channels

Depression is a common and complex psychiatric illness with multiple clinical symptoms, even leading to the disability and suicide. Owing to the partial understanding of the pathogenesis of depressive-like disorders, available pharmacotherapeutic strategies are developed mainly based on the "monoamine hypothesis", resulting in a limited effectiveness and a number of adverse effects in the clinical practice. The concept of multiple pathogenic factors be helpful for clarifying the etiology of depression and developing the antidepressants. It is well documented that K+ channels serve crucial roles in modulating the neuronal excitability and neurotransmitter release in the brain, and abnormality of these channels participated in the pathogenic process of diverse central nervous system (CNS) pathologies, such as seizure and Alzheimer's disease (AD). The clinical and preclinical evidence also delineates that the involvement of several types of K+ channels in depressive-like behaviors appear to be evident, suggesting these channels being one of the multiple factors in the etiology of this debilitating disorder. Emerging data manifest that diverse antidepressants impact distinct K+ channels, such as Kv, Kir and K2P, meaning the functioning of these drug via a "multi-target" manner. On the other hand, the scenario of antidepressants impinging K+ channels could render an alternative interpretation for the pharmacological effectiveness and numerous side effects in clinical trials. Furthermore, these channels serve to be considered as a "druggable target" to develop novel therapeutic compound to antagonize this psychiatry.

Exploratory studies of the antidepressant effect of Cordyceps sinensis polysaccharide and its potential mechanism

Cordyceps sinensis, a traditionally prized medicinal fungus, contains polysaccharides as one of its main bioactive constituents, known for their significant immunomodulatory properties. In this study, we systematically investigated the composition and structure of Cordyceps sinensis polysaccharide, followed by an evaluation of its therapeutic effect on depression using a chronic restraint stress-induced depression model. The polysaccharide CSWP-2, extracted via hot water, precipitated with ethanol, and purified using DEAE-cellulose column chromatography from Cordyceps sinensis, is primarily composed of glucose, mannose, and galactose, with α-1,4-D-glucan as its major structural component. Behavioral tests, immunological profiling, metabolomics, and gut microbiota analyses indicated a notable ameliorative effect of CSWP-2 on depressive-like symptoms in mice. Furthermore, the action of CSWP-2 may be attributed to the modulation of the gut microbiome's abundance and its metabolic impacts, thereby transmitting signals to the host immune system and exerting immunomodulatory activity, ultimately contributing to its antidepressant effects.

Dysregulation of kappa opioid receptor neuromodulation of lateral habenula synaptic function following a repetitive mild traumatic brain injury

Mild traumatic brain injury (mTBI) increases the risk of affective disorders, anxiety and substance use disorder. The lateral habenula (LHb) plays an important role in pathophysiology of psychiatric disorders. Recently, we demonstrated a causal link between mTBI-induced LHb hyperactivity due to excitation/inhibition (E/I) imbalance and motivational deficits in male mice using a repetitive closed head injury mTBI model. A major neuromodulatory system that is responsive to traumatic brain injuries, influences affective states and also modulates LHb activity is the dynorphin/kappa opioid receptor (Dyn/KOR) system. However, the effects of mTBI on KOR neuromodulation of LHb function are unknown. Here, we first used retrograde tracing in male and female Cre mouse lines and identified several major KOR-expressing and two prominent Dyn-expressing inputs projecting to the mouse LHb, highlighting the medial prefrontal cortex (mPFC) and the ventromedial nucleus of the hypothalamus (VMH) as the main LHb-projecting Dyn inputs that regulate KOR signaling to the LHb. We then functionally evaluated the effects of in vitro KOR modulation of spontaneous synaptic activity within the LHb of male and female sham and mTBI mice at 4 week post-injury. We observed sex-specific differences in spontaneous release of glutamate and GABA from presynaptic terminals onto LHb neurons with higher levels of presynaptic glutamate and GABA release in females compared to male mice. However, KOR effects on the spontaneous E/I ratios and synaptic drive ratio within the LHb did not differ between male and female sham and mTBI mice. KOR activation generally suppressed spontaneous glutamatergic transmission without altering GABAergic transmission, resulting in a significant but sex-similar reduction in net spontaneous E/I and synaptic drive ratios in LHb neurons of sham mice. Following mTBI, while responses to KOR activation at LHb glutamatergic synapses remained intact, LHb GABAergic synapses acquired an additional sensitivity to KOR-mediated inhibition where we observed a reduction in GABA release probability in response to KOR stimulation in LHb neurons of mTBI mice. Further analysis of percent change in spontaneous synaptic ratios induced by KOR activation revealed that independent of sex mTBI switches KOR-driven synaptic inhibition of LHb neurons (normally observed in sham mice) in a subset of mTBI mice toward synaptic excitation resulting in mTBI-induced divergence of KOR actions within the LHb. Overall, we uncovered the sources of major Dyn/KOR-expressing synaptic inputs projecting to the mouse LHb. We demonstrate that an engagement of intra-LHb Dyn/KOR signaling provides a global KOR-driven synaptic inhibition within the mouse LHb independent of sex. The additional engagement of KOR-mediated action on LHb GABAergic transmission by mTBI could contribute to the E/I imbalance after mTBI, with Dyn/KOR signaling serving as a disinhibitory mechanism for LHb neurons of a subset of mTBI mice.

Deep brain stimulation targeted at lateral hypothalamus-medial forebrain bundle reverses depressive-like symptoms and related cognitive deficits in rat: Role of serotoninergic system

The aim of the study is to understand the rationale behind the application of deep brain stimulation (DBS) in the treatment of depression. Male Wistar rats, rendered depressive with chronic unpredictable mild stress (CUMS) were implanted with electrode in the lateral hypothalamus-medial forebrain bundle (LH-MFB) and subjected to deep brain stimulation (DBS) for 4 h each day for 14 days. DBS rats, as well as controls, were screened for a range of parameters indicative of depressive state. Symptomatic features noticed in CUMS rats like the memory deficit, anhedonia, reduction in body weight and 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in mPFC and elevated plasma corticosterone were reversed in rats subjected to DBS. DBS arrested CUMS induced degeneration of 5-HT cells in interfascicular region of dorsal raphe nucleus (DRif) and fibers in LH-MFB and induced dendritic proliferation in mPFC neurons. MFB is known to serve as a major conduit for the DRif-mPFC serotoninergic pathway. While the density of serotonin fibers in the LH-MFB circuit was reduced in CUMS, it was upregulated in DBS-treated rats. Furthermore, microinjection of 5-HT1A receptor antagonist, WAY100635 into mPFC countered the positive effects of DBS like the antidepressant and memory-enhancing action. In this background, we suggest that DBS at LH-MFB may exercise positive effect in depressive rats via upregulation of the serotoninergic system. While these data drawn from the experiments on rat provide meaningful clues, we suggest that further studies aimed at understanding the usefulness of DBS at LH-MFB in humans may be rewarding.

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.

Sexual dimorphic distribution of G protein-coupled receptor 30 in pain-related regions of the mouse brain

Sex differences in pain sensitivity have contributed to the fact that medications for curing chronic pain are unsatisfactory. However, the underlying mechanism remains to be elucidated. Brain-derived estrogen participates in modulation of sex differences in pain and related emotion. G protein-coupled receptor 30 (GPR30), identified as a novel estrogen receptor with a different distribution than traditional receptors, has been proved to play a vital role in regulating pain affected by estrogen. However, the contribution of its distribution to sexually dimorphic pain-related behaviors has not been fully explored. In the current study, immunofluorescence assays were applied to mark the neurons expressing GPR30 in male and female mice (in metestrus and proestrus phase) in pain-related brain regions. The neurons that express CaMKIIα or VGAT were also labeled to observe overlap with GPR30. We found that females had more GPR30-positive (GPR30+) neurons in the primary somatosensory (S1) and insular cortex (IC) than males. In the lateral habenula (LHb) and the nucleus tractus solitarius (NTS), males had more GPR30+ neurons than females. Moreover, within the LHb, the expression of GPR30 varied with estrous cycle phase; females in metestrus had fewer GPR30+ neurons than those in proestrus. In addition, females had more GPR30+ neurons, which co-expressed CaMKIIα in the medial preoptic nucleus (mPOA) than males, while males had more than females in the basolateral complex of the amygdala (BLA). These findings may partly explain the different modulatory effects of GPR30 in pain and related emotional phenotypes between sexes and provide a basis for comprehension of sexual dimorphism in pain related to estrogen and GPR30, and finally provide new targets for exploiting new treatments of sex-specific pain.

Distinct populations of lateral preoptic nucleus neurons jointly contribute to depressive-like behaviors through divergent projections in male mice

The lateral preoptic area (LPO) is a component of the hypothalamus involved in various physiological functions including sleep-wakefulness transition, thermoregulation, and water-salt balance. In this study, we discovered that distinct LPO excitatory neurons project separately to the aversive processing center lateral habenula (LHb) and the reward processing hub ventral tegmental area (VTA). Following chronic restraint stress (CRS), the LHb-projecting and VTA-projecting LPO neurons exhibited increased and decreased neuronal activities, respectively. Optogenetic activation of LHb-projecting LPO excitatory neurons and LPO excitatory neuronal terminals within LHb evoked aversion and avoidance behaviors, while activation of VTA-projecting LPO excitatory neurons and LPO excitatory neuronal terminals within VTA produced preference and exploratory behaviors in mice. Furthermore, either optogenetic inhibition of LHb-projecting LPO excitatory neurons or activation of VTA-projecting LPO excitatory neurons during CRS effectively prevented the development of depressive-like behaviors. Our study unveils, for the first-time, divergent pathways originating from LPO that regulate opposite affective states in mice and implicates that an imbalance of their activities could lead to depressive-like behaviors. These circuitries represent promising therapeutic targets to relieve emotional dysfunctions in neuropsychiatric disorders.

Adolescent stress differentially modifies dopamine and norepinephrine release in the medial prefrontal cortex of adult rats

Adolescent stress (AS) has been associated with higher vulnerability to psychiatric disorders such as schizophrenia, depression, or drug dependence. Moreover, the alteration of brain catecholamine (CAT) transmission in the medial prefrontal cortex (mPFC) has been found to play a major role in the etiology of psychiatric disturbances. We investigated the effect of adolescent stress on CAT transmission in the mPFC of freely moving adult rats because of the importance of this area in the etiology of psychiatric disorders, and because CAT transmission is the target of a relevant group of drugs used in the therapy of depression and psychosis. We assessed basal dopamine (DA) and norepinephrine (NE) extracellular concentrations (output) by brain microdialysis in in the mPFC of adult rats that were exposed to chronic mild stress in adolescence. To ascertain the role of an altered release or reuptake, we stimulated DA and NE output by administering either different doses of amphetamine (0.5 and 1.0 mg / kg s.c.), which by a complex mechanism determines a dose dependent increase in the CAT output, or reboxetine (10 mg/kg i.p.), a selective NE reuptake inhibitor. The results showed the following: (i) basal DA output in AS rats was lower than in controls, while no difference in basal NE output was observed; (ii) amphetamine, dose dependently, stimulated DA and NE output to a greater extent in AS rats than in controls; (iii) reboxetine stimulated NE output to a greater extent in AS rats than in controls, while no difference in stimulated DA output was observed between the two groups. These results show that AS determines enduring effects on DA and NE transmission in the mPFC and might lead to the occurrence of psychiatric disorders or increase the vulnerability to drug addiction.

Burst firing in Output-Defined Parallel Habenula Circuit Underlies the Antidepressant Effects of Bright Light Treatment

Research highlights the significance of increased bursting in lateral habenula (LHb) neurons in depression and as a focal point for bright light treatment (BLT). However, the precise spike patterns of LHb neurons projecting to different brain regions during depression, their roles in depression development, and BLT's therapeutic action remain elusive. Here, LHb neurons are found projecting to the dorsal raphe nucleus (DRN), ventral tegmental area (VTA), and median raphe nucleus (MnR) exhibit increased bursting following aversive stimuli exposure, correlating with distinct depressive symptoms. Enhanced bursting in DRN-projecting LHb neurons is pivotal for anhedonia and anxiety, while concurrent bursting in LHb neurons projecting to the DRN, VTA, and MnR is essential for despair. Remarkably, reducing bursting in distinct LHb neuron subpopulations underlies the therapeutic effects of BLT on specific depressive behaviors. These findings provide valuable insights into the mechanisms of depression and the antidepressant action of BLT.

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'.

A Light-Responsive Neural Circuit Suppresses Feeding

Light plays an essential role in a variety of physiological processes, including vision, mood, and glucose homeostasis. However, the intricate relationship between light and an animal's feeding behavior has remained elusive. Here, we found that light exposure suppresses food intake, whereas darkness amplifies it in male mice. Interestingly, this phenomenon extends its reach to diurnal male Nile grass rats and healthy humans. We further show that lateral habenula (LHb) neurons in mice respond to light exposure, which in turn activates 5-HT neurons in the dorsal Raphe nucleus (DRN). Activation of the LHb→5-HTDRN circuit in mice blunts darkness-induced hyperphagia, while inhibition of the circuit prevents light-induced anorexia. Together, we discovered a light-responsive neural circuit that relays the environmental light signals to regulate feeding behavior in mice.

Role of electrophysiological activity and interactions of lateral habenula in the development of depression-like behavior in a chronic restraint stress model

Closed-loop deep brain stimulation (DBS) system offers a promising approach for treatment-resistant depression, but identifying universally accepted electrophysiological biomarkers for closed-loop DBS systems targeting depression is challenging. There is growing evidence suggesting a strong association between the lateral habenula (LHb) and depression. Here, we took LHb as a key target, utilizing multi-site local field potentials (LFPs) to study the acute and chronic changes in electrophysiology, functional connectivity, and brain network characteristics during the formation of a chronic restraint stress (CRS) model. Furthermore, our model combining the electrophysiological changes of LHb and interactions between LHb and other potential targets of depression can effectively distinguish depressive states, offering a new way for developing effective closed-loop DBS strategies.

Static and dynamic functional connectivity of the habenula in late-life depression patient with suicidal ideation

BACKGROUND

Suicide is one of the most lethal complications of late-life depression (LLD), and habenular dysfunction may be involved in depression-related suicidality and may serve as a potential target for alleviating suicidal ideation. This study aimed to investigate abnormal functional connectivity of the habenula in LLD patients with suicidal ideation.

METHODS

One hundred twenty-seven patients with LLD (51 with suicidal ideation (LLD-S) and 76 without suicidal ideation (LLD-NS)) and 75 healthy controls (HCs) were recruited. The static functional connectivity (sFC) and dynamic functional connectivity (dFC) between the habenula and the whole brain were compared among the three groups, and correlation and moderation analyses were applied to investigate whether suicidal ideation moderated the relationships of habenular FC with depressive symptoms and cognitive impairment.

RESULTS

The dFC between the right habenula and the left orbitofrontal cortex (OFC) increased in the following order: LLD-S > LLD-NS > control. No significant difference in the habenular sFC was found among the LLD-S, LLD-NS and control groups. The dFC between the right habenula and the left OFC was positively associated with global cognitive function and visuospatial skills, and the association between this dFC and visuospatial skills was moderated by suicidal ideation in patients with LLD.

CONCLUSION

The increased variability in dFC between the right habenula and left OFC was more pronounced in the LLD-S group than in the LLD-NS group, and the association between habenular-OFC dFC and visuospatial skills was moderated by suicidal ideation in patients with LLD.

Foxg1 Modulation of the Prkcd Gene in the Lateral Habenula Mediates Trigeminal Neuralgia-Associated Anxiety-Like Behaviors in Mice

Trigeminal Neuralgia (TN) is a debilitating disorder frequently accompanied by mood complications such as depression and anxiety. The current study sought to elucidate the molecular underpinnings that contribute to the pathogenesis of TN and its associated anxiety. Employing a partial transection of the infraorbital nerve (pT-ION) in a murine model, we successfully induced sustained primary and secondary orofacial allodynia alongside anxiety-like behavioral manifestations. Transcriptome-wide gene microarray analyses revealed a marked upregulation of Foxg1 subsequent to pT-ION. Targeted knockdown of Foxg1, achieved through bilateral microinjection of adeno-associated virus harboring Foxg1-specific shRNA into the lateral habenula (LHb), resulted in a significant attenuation of both orofacial pain and anxiety-like behaviors. Subsequent RNA sequencing implicated Prkcd as a downstream effector gene modulated by Foxg1. Pharmacological inhibition of protein kinase C delta, encoded by Prkcd, within the LHb markedly ameliorated pT-ION-induced symptomatology. The dual luciferase assay revealed that Foxg1 substantially enhances the transcriptional activity of the Prkcd gene. Collectively, these findings indicate that trigeminal nerve injury leads to Foxg1 upregulation in the LHb, which in turn elevates the expression of Prkcd, culminating in the manifestation of orofacial pain and anxiety-like behaviors. This work offers promising therapeutic targets and a conceptual framework for the clinical management of TN and its psychological comorbidities.

Pain in Parkinson's disease: a neuroanatomy-based approach

Parkinson's disease is a progressive neurodegenerative disorder characterized by the deposition of misfolded alpha-synuclein in different regions of the central and peripheral nervous system. Motor impairment represents the signature clinical expression of Parkinson's disease. Nevertheless, non-motor symptoms are invariably present at different stages of the disease and constitute an important therapeutic challenge with a high impact for the patients' quality of life. Among non-motor symptoms, pain is frequently experienced by patients, being present in a range of 24-85% of Parkinson's disease population. Moreover, in more than 5% of patients, pain represents the first clinical manifestation, preceding by decades the exordium of motor symptoms. Pain implies a complex biopsychosocial experience with a downstream complex anatomical network involved in pain perception, modulation, and processing. Interestingly, all the anatomical areas involved in pain network can be affected by a-synuclein pathology, suggesting that pathophysiology of pain in Parkinson's disease encompasses a 'pain spectrum', involving different anatomical and neurochemical substrates. Here the various anatomical sites recruited in pain perception, modulation and processing are discussed, highlighting the consequences of their possible degeneration in course of Parkinson's disease. Starting from peripheral small fibres neuropathy and pathological alterations at the level of the posterior laminae of the spinal cord, we then describe the multifaceted role of noradrenaline and dopamine loss in driving dysregulated pain perception. Finally, we focus on the possible role of the intertwined circuits between amygdala, nucleus accumbens and habenula in determining the psycho-emotional, autonomic and cognitive experience of pain in Parkinson's disease. This narrative review provides the first anatomically driven comprehension of pain in Parkinson's disease, aiming at fostering new insights for personalized clinical diagnosis and therapeutic interventions.

Addiction-Prone Personality and Creative Cognitive Styles: A Moderated Mediation Model of Novelty Seeking and Depression Tendency

This study attempted to examine the mechanism of the impact of Addiction-Prone Personality (APP) on creative cognitive styles (idea generation, idea selection), especially to explore the mediating role of novelty seeking and the moderating role of depression tendency on the relationship between APP and creative cognitive styles. College students (N = 576, 79% female) participated in and completed measures of APP, idea generation and selection, novelty seeking, and depression tendency. Results showed that (1) APP was positively related with idea generation while negatively related with idea selection; (2) novelty seeking played a partial mediating role in the relationship between APP and idea generation and a suppressing effect between APP and idea selection; (3) depression tendency moderated the indirect relationship between APP and creative cognitive styles through novelty seeking. Therefore, APP has different indirect effects on idea generation and idea selection via novelty seeking. When there was a higher depression tendency, there was a stronger indirect effect. The study highlights the significant importance of the underlying processes between APP and creative cognitive styles and offers implications for rethinking the relationship between addiction and creativity.

Optogenetic activation of the lateral habenulaD1R-ventral tegmental area circuit induces depression-like behavior in mice

A number of different receptors are distributed in glutamatergic neurons of the lateral habenula (LHb). These glutamatergic neurons are involved in different neural pathways, which may identify how the LHb regulates various physiological functions. However, the role of dopamine D1 receptor (D1R)-expressing habenular neurons projecting to the ventral tegmental area (VTA) (LHbD1R-VTA) remains not well understood. In the current study, to determine the activity of D1R-expressing neurons in LHb, D1R-Cre mice were used to establish the chronic restraint stress (CRS) depression model. Adeno-associated virus was injected into bilateral LHb in D1R-Cre mice to examine whether optogenetic activation of the LHb D1R-expressing neurons and their projections could induce depression-like behavior. Optical fibers were implanted in the LHb and VTA, respectively. To investigate whether optogenetic inhibition of the LHbD1R-VTA circuit could produce antidepressant-like effects, the adeno-associated virus was injected into the bilateral LHb in the D1R-Cre CRS model, and optical fibers were implanted in the bilateral VTA. The D1R-expressing neuronal activity in the LHb was increased in the CRS depression model. Optogenetic activation of the D1R-expressing neurons in LHb induced behavioral despair and anhedonia, which could also be induced by activation of the LHbD1R-VTA axons. Conversely, optogenetic inhibition of the LHbD1R-VTA circuit improved behavioral despair and anhedonia in the CRS depression model. D1R-expressing glutamatergic neurons in the LHb and their projections to the VTA are involved in the occurrence and regulation of depressive-like behavior.

The neuronal and synaptic dynamics underlying post-inhibitory rebound burst related to major depressive disorder in the lateral habenula neuron model

A burst behavior observed in the lateral habenula (LHb) neuron related to major depressive disorder has attracted much attention. The burst is induced from silence by the excitatory N-methyl-D-aspartate (NMDA) synapse or by the inhibitory stimulation, i.e., a post-inhibitory rebound (PIR) burst, which has not been explained clearly. In the present paper, the neuronal and synaptic dynamics for the PIR burst are acquired in a theoretical neuron model. At first, dynamic cooperations between the fast rise of inhibitory γ-aminobutyric acid (GABA) synapse, slow rise of NMDA synapse, and T-type calcium current to evoke the PIR burst are obtained. Similar to the inhibitory pulse stimulation, fast rising GABA current can reduce the membrane potential to a level low enough to de-inactivate the low threshold T-type calcium current to evoke a PIR spike, which can enhance the slow rising NMDA current activated at a time before or after the PIR spike. The NMDA current following the PIR spike exhibits slow decay to induce multiple spikes to form the PIR burst. Such results present a theoretical explanation and a candidate for the PIR burst in real LHb neurons. Then, the dynamical mechanism for the PIR spike mediated by the T-type calcium channel is obtained. At large conductance of T-type calcium channel, the resting state corresponds to a stable focus near Hopf bifurcation and exhibits an "uncommon" threshold curve with membrane potential much lower than the resting membrane potential. Inhibitory modulation induces membrane potential decreased to run across the threshold curve to evoke the PIR spike. At small conductance of the T-type calcium channel, a stable node appears and manifests a common threshold curve with higher membrane potential, resulting in non-PIR phenomenon. The results present the dynamic cooperations between neuronal dynamics and fast/slow dynamics of different synapses for the PIR burst observed in the LHb neuron, which is helpful for the modulations to major depressive disorder.

Modulation of habenular and nucleus accumbens functional connectivity by ketamine in major depression

INTRODUCTION

Major depressive disorder (MDD) is associated with dysfunctional reward processing, which involves functional circuitry of the habenula (Hb) and nucleus accumbens (NAc). Since ketamine elicits rapid antidepressant and antianhedonic effects in MDD, this study sought to investigate how serial ketamine infusion (SKI) treatment modulates static and dynamic functional connectivity (FC) in Hb and NAc functional networks.

METHODS

MDD participants (n = 58, mean age = 40.7 years, female = 28) received four ketamine infusions (0.5 mg/kg) 2-3 times weekly. Resting-state functional magnetic resonance imaging (fMRI) scans and clinical assessments were collected at baseline and 24 h post-SKI. Static FC (sFC) and dynamic FC variability (dFCv) were calculated from left and right Hb and NAc seeds to all other brain regions. Changes in FC pre-to-post SKI, and correlations with changes with mood and anhedonia were examined. Comparisons of FC between patients and healthy controls (HC) at baseline (n = 55, mean age = 32.6, female = 31), and between HC assessed twice (n = 16) were conducted as follow-up analyses.

RESULTS

Following SKI, significant increases in left Hb-bilateral visual cortex FC, decreases in left Hb-left inferior parietal cortex FC, and decreases in left NAc-right cerebellum FC occurred. Decreased dFCv between left Hb and right precuneus and visual cortex, and decreased dFCv between right NAc and right visual cortex both significantly correlated with improvements in mood ratings. Decreased FC between left Hb and bilateral visual/parietal cortices as well as increased FC between left NAc and right visual/parietal cortices both significantly correlated with improvements in anhedonia. No differences were observed between HC at baseline or over time.

CONCLUSION

Subanesthetic ketamine modulates functional pathways linking the Hb and NAc with visual, parietal, and cerebellar regions in MDD. Overlapping effects between Hb and NAc functional systems were associated with ketamine's therapeutic response.

Dysregulation of Kappa Opioid Receptor Neuromodulation of Lateral Habenula Synaptic Function following a Repetitive Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) increases the risk of cognitive deficits, affective disorders, anxiety and substance use disorder in affected individuals. Substantial evidence suggests a critical role for the lateral habenula (LHb) in pathophysiology of psychiatric disorders. Recently, we demonstrated a causal link between persistent mTBI-induced LHb hyperactivity due to synaptic excitation/inhibition (E/I) imbalance and motivational deficits in self-care grooming behavior in young adult male mice using a repetitive closed head injury mTBI model. One of the major neuromodulatory systems that is responsive to traumatic brain and spinal cord injuries, influences affective states and also modulates LHb activity is the dynorphin/kappa opioid receptor (Dyn/KOR) system. However, the effects of mTBI on KOR neuromodulation of LHb function is unknown. To address this, we first used retrograde tracing to anatomically verify that the mouse LHb indeed receives Dyn/KOR expressing projections. We identified several major KOR-expressing and Dyn-expressing synaptic inputs projecting to the mouse LHb. We then functionally evaluated the effects of in vitro KOR modulation of spontaneous synaptic activity within the LHb of male and female sham and mTBI mice at 4week post-injury using the repetitive closed head injury mTBI model. Similar to what we previously reported in the LHb of male mTBI mice, mTBI presynaptically diminished spontaneous synaptic activity onto LHb neurons, while shifting synaptic E/I toward excitation in female mouse LHb. Furthermore, KOR activation in either mouse male/female LHb generally suppressed spontaneous glutamatergic transmission without altering GABAergic transmission, resulting in a significant reduction in E/I ratios and decreased excitatory synaptic drive to LHb neurons of male and female sham mice. Interestingly following mTBI, while responses to KOR activation at LHb glutamatergic synapses were observed comparable to those of sham, LHb GABAergic synapses acquired an additional sensitivity to KOR-mediated inhibition. Thus, in contrast to sham LHb, we observed a reduction in GABA release probability in response to KOR stimulation in mTBI LHb, resulting in a chronic loss of KOR-mediated net synaptic inhibition within the LHb. Overall, our findings uncovered the previously unknown sources of major Dyn/KOR-expressing synaptic inputs projecting to the mouse LHb. Further, we demonstrate that an engagement of intra-LHb Dyn/KOR signaling provides a global suppression of excitatory synaptic drive to the mouse LHb which could act as an inhibitory braking mechanism to prevent LHb hyperexcitability. The additional engagement of KOR-mediated modulatory action on LHb GABAergic transmission by mTBI could contribute to the E/I imbalance after mTBI, with Dyn/KOR signaling serving as a disinhibitory mechanism for LHb neurons in male and female mTBI mice.

Repurposing Ketamine in the Therapy of Depression and Depression-Related Disorders: Recent Advances and Future Potential

Depression represents a prevalent and enduring mental disorder of significant concern within the clinical domain. Extensive research indicates that depression is very complex, with many interconnected pathways involved. Most research related to depression focuses on monoamines, neurotrophic factors, the hypothalamic-pituitary-adrenal axis, tryptophan metabolism, energy metabolism, mitochondrial function, the gut-brain axis, glial cell-mediated inflammation, myelination, homeostasis, and brain neural networks. However, recently, Ketamine, an ionotropic N-methyl-D-aspartate (NMDA) receptor antagonist, has been discovered to have rapid antidepressant effects in patients, leading to novel and successful treatment approaches for mood disorders. This review aims to summarize the latest findings and insights into various signaling pathways and systems observed in depression patients and animal models, providing a more comprehensive view of the neurobiology of anxious-depressive-like behavior. Specifically, it highlights the key mechanisms of ketamine as a rapid-acting antidepressant, aiming to enhance the treatment of neuropsychiatric disorders. Moreover, we discuss the potential of ketamine as a prophylactic or therapeutic intervention for stress-related psychiatric disorders.

Whole-brain connections of glutamatergic neurons in the mouse lateral habenula in both sexes

BACKGROUND

The lateral habenula (LHb) is an epithalamus nucleus that is evolutionarily conserved and involved in various physiological functions, such as encoding value signals, integrating emotional information, and regulating related behaviors. The cells in the LHb are predominantly glutamatergic and have heterogeneous functions in response to different stimuli. The circuitry connections of the LHb glutamatergic neurons play a crucial role in integrating a wide range of events. However, the circuitry connections of LHb glutamatergic neurons in both sexes have not been thoroughly investigated.

METHODS

In this study, we injected Cre-dependent retrograde trace virus and anterograde synaptophysin-labeling virus into the LHb of adult male and female Vglut2-ires-Cre mice, respectively. We then quantitatively analyzed the input and output of the LHb glutamatergic connections in both the ipsilateral and contralateral whole brain.

RESULTS

Our findings showed that the inputs to LHbvGlut2 neurons come from more than 30 brain subregions, including the cortex, striatum, pallidum, thalamus, hypothalamus, midbrain, pons, medulla, and cerebellum with no significant differences between males and females. The outputs of LHbvGlut2 neurons targeted eight large brain regions, primarily focusing on the midbrain and pons nuclei, with distinct features in presynaptic bouton across different brain subregions. While correlation and cluster analysis revealed differences in input and collateral projection features, the input-output connection pattern of LHbvGlut2 neurons in both sexes was highly similar.

CONCLUSIONS

This study provides a systematic and comprehensive analysis of the input and output connections of LHbvGlut2 neurons in male and female mice, shedding light on the anatomical architecture of these specific cell types in the mouse LHb. This structural understanding can help guide further investigations into the complex functions of the LHb.

SNORA69 is up-regulated in the lateral habenula of individuals with major depressive disorder

Major depressive disorder (MDD) is a complex and potentially debilitating illness whose etiology and pathology remains unclear. Non-coding RNAs have been implicated in MDD, where they display differential expression in the brain and the periphery. In this study, we quantified small nucleolar RNA (snoRNA) expression by small RNA sequencing in the lateral habenula (LHb) of individuals with MDD (n = 15) and psychiatrically-healthy controls (n = 15). We uncovered five snoRNAs that exhibited differential expression between MDD and controls (FDR < 0.01). Specifically, SNORA69 showed increased expression in MDD and was technically validated via RT-qPCR. We further investigated the expression of Snora69 in the LHb and peripheral blood of an unpredicted chronic mild stress (UCMS) mouse model of depression. Snora69 was specifically up-regulated in mice that underwent the UCMS paradigm. SNORA69 is known to guide pseudouridylation onto 5.8S and 18S rRNAs. We quantified the relative abundance of pseudouridines on 5.8S and 18S rRNA in human post-mortem LHb samples and found increased abundance of pseudouridines in the MDD group. Overall, our findings indicate the importance of brain snoRNAs in the pathology of MDD. Future studies characterizing SNORA69's role in MDD pathology is warranted.

Opportunities and challenges for the use of deep brain stimulation in the treatment of refractory major depression

Major Depressive Disorder continues to remain one of the most prevalent psychiatric diseases globally. Despite multiple trials of conventional therapies, a subset of patients fail to have adequate benefit to treatment. Deep brain stimulation (DBS) is a promising treatment in this difficult to treat population and has shown strong antidepressant effects across multiple cohorts. Nearly two decades of work have provided insights into the potential for chronic focal stimulation in precise brain targets to modulate pathological brain circuits that are implicated in the pathogenesis of depression. In this paper we review the rationale that prompted the selection of various brain targets for DBS, their subsequent clinical outcomes and common adverse events reported. We additionally discuss some of the pitfalls and challenges that have prevented more widespread adoption of this technology as well as future directions that have shown promise in improving therapeutic efficacy of DBS in the treatment of depression.

Clinical impacts of n-3 fatty acids supplementation on depression symptoms: an umbrella review of meta-analyses

Several meta-analyses investigating the efficacy of n-3 PUFA in alleviating depression symptoms have reported conflicting findings. In the present study, we aimed to perform an umbrella meta-analysis to provide a definite conclusion. A comprehensive systematic search of PubMed, Scopus, Embase, Web of Science and Cochrane Central Library was performed up to June 2021. Meta-analysis studies evaluating the effects of n-3 PUFA on depression symptoms were included. The quality of the included meta-analyses was assessed using AMSTAR questionnaire. Out of 101 studies, twenty-two studies with twenty-six effect sizes (ES) were eligible for inclusion. Sixteen ES showed significant improving effect of n-3 supplementation on depression symptoms among which eleven ES had small ES. The other studies observed no significant effect. Available evidence suggests that n-3 PUFA (EPA, DHA) supplementation could be considered as an effective add-on therapeutic approach in relieving depression symptoms.

Recent Advances in Habenula Imaging Technology: A Comprehensive Review

The habenula (Hb) is involved in many natural human behaviors, and the relevance of its alterations in size and neural activity to several psychiatric disorders and addictive behaviors has been presumed and investigated in recent years using magnetic resonance imaging (MRI). Although the Hb is small, an increasing number of studies have overcome the difficulties in MRI. Conventional structural-based imaging also has great defects in observing the Hb contrast with adjacent structures. In addition, more and more attention should be paid to the Hb's functional, structural, and quantitative imaging studies. Several advanced MRI methods have recently been employed in clinical studies to explore the Hb and its involvement in psychiatric diseases. This review summarizes the anatomy and function of the human Hb; moreover, it focuses on exploring the human Hb with noninvasive MRI approaches, highlighting strategies to overcome the poor contrast with adjacent structures and the need for multiparametric MRI to develop imaging markers for diagnosis and treatment follow-up. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 2.

P2X7 receptor of olfactory bulb microglia plays a pathogenic role in stress-related depression in mice with allergic rhinitis

The aim of this study was to explore the role and mechanism of the olfactory bulb (OB) microglial P2X7 receptor (P2X7R) in allergic rhinitis (AR)-related depression, with the objective of identifying a potential clinical target. An AR mouse model was induced using ovalbumin (OVA), while chronic stress was employed to induce depression. The study used P2X7R-specific antagonists and OB microglia-specific P2X7R knockdown mice as crucial tools. The results showed that mice in the OVA + stress group exhibited more pronounced depressive-like phenotypes. Furthermore, there was an observed increase in microglial activation in the OB, followed by a rise in the level of inflammation. The pharmacological inhibition of P2X7R significantly mitigated the depression-like phenotype and the OB inflammatory response in OVA + stress mice. Notably, the specific knockdown of microglial P2X7R in the OB resulted in a similar effect, possibly linked to the regulation of IL-1β via the "ATP-P2X7R-Caspase 1" axis. These findings collectively demonstrate that microglial P2X7R in the OB acts as a direct effector molecule in AR-related depression, and its inhibition may offer a novel strategy for clinical prevention and treatment.

Lateral Habenula Neurons Signal Cold Aversion and Participate in Cold Aversion

The aversion to cold is a fundamental motivated behavior that contributes to the body temperature homeostasis. However, the involvement of the lateral habenula (LHb) as a regulatory hub for negative emotions in this physiological process remains uninvestigated. In this study, we demonstrate an elevation in the population activity of LHb neurons following exposure to cold stimuli. Additionally, we establish the necessity of Vglut2-expressing neurons within the LHb for the encoding of cold aversion behaviors. Furthermore, we have elucidated a neural circuit from excitatory neurons of the dorsomedial hypothalamus (DMH) to LHb that plays a crucial role in this progress. Manipulation of the DMH-LHb circuit has a significant impact on cold aversion behavior in mice. It is worth noting that this circuit does not exhibit any noticeable effects on autonomic thermoregulation or depression-like behavior. The identification of these neural mechanisms involved in behavioral thermoregulation provides a promising avenue for future research.