Neuroplasticity and cellular resilience in mood disorders

Research Progress on NMDA Receptor Enhancement Drugs for the Treatment of Depressive Disorder

Major depressive disorder (MDD) is a severe mental illness with a complex etiology. Currently, many medications employed in clinical treatment exhibit limitations such as delayed onset of action and a high incidence of adverse reactions. Therefore, there is a pressing need to develop antidepressants that exhibit enhanced efficacy and safety. The N-methyl-D-aspartate receptor (NMDAR), a distinctive glutamate-gated ion channel receptor, has been implicated in the onset and progression of depressive disorder, as evidenced by both preclinical and clinical research. The NMDAR antagonist, ketamine, exhibits rapid and sustained antidepressant effects, holding promise as a novel therapeutic approach for depressive disorder. However, its psychotomimetic impact and potential for addiction have restricted its widespread clinical application. Notably, over the past decade, studies have suggested that enhancing NMDAR functionality can produce antidepressant effects with improved safety, especially with the emergence of NMDAR-positive allosteric modulators (PAMs). We view this as a potential novel strategy for treating depression, forming the basis for the narrative review that follows.

An open label pilot trial of low-dose lithium for young people at ultra-high risk for psychosis

AIM

Lithium, even at low doses, appears to offer neuroprotection against a wide variety of insults. In this controlled pilot, we examined the safety (i.e., side-effect profile) of lithium in a sample of young people identified at ultra-high risk (UHR) for psychosis. The secondary aim was to explore whether lithium provided a signal of clinical efficacy in reducing transition to psychosis compared with treatment as usual (TAU).

METHODS

Young people attending the PACE clinic at Orygen, Melbourne, were prescribed a fixed dose (450 mg) of lithium (n = 25) or received TAU (n = 78). The primary outcome examined side-effects, with transition to psychosis, functioning and measures of psychopathology assessed as secondary outcomes.

RESULTS

Participants in both groups were functionally compromised (lithium group GAF = 56.6; monitoring group GAF = 56.9). Side-effect assessment indicated that lithium was well-tolerated. 64% (n = 16) of participants in the lithium group were lithium-adherent to week 12. Few cases transitioned to psychosis across the study period; lithium group 4% (n = 1); monitoring group 7.7% (n = 6). There was no difference in time to transition to psychosis between the groups. No group differences were observed in other functioning and symptom domains, although all outcomes improved over time.

CONCLUSIONS

With a side-effect profile either comparable to, or better than UHR antipsychotic trials, lithium might be explored for further research with UHR young people. A definitive larger trial is needed to determine the efficacy of lithium in this cohort.

Chronic psychosocial stress triggers microglial-/macrophage-induced inflammatory responses leading to neuronal dysfunction and depressive-related behavior

Chronic environmental stress and traumatic social experiences induce maladaptive behavioral changes and is a risk factor for major depressive disorder (MDD) and various anxiety-related psychiatric disorders. Clinical studies and animal models of chronic stress have reported that symptom severity is correlated with innate immune responses and upregulation of neuroinflammatory cytokine signaling in brain areas implicated in mood regulation (mPFC; medial Prefrontal Cortex). Despite increasing evidence implicating impairments of neuroplasticity and synaptic signaling deficits into the pathophysiology of stress-related mental disorders, how microglia may modulate neuronal homeostasis in response to chronic stress has not been defined. Here, using the repeated social defeat stress (RSDS) mouse model we demonstrate that microglial-induced inflammatory responses are regulating neuronal plasticity associated with psychosocial stress. Specifically, we show that chronic stress induces a rapid activation and proliferation of microglia as well as macrophage infiltration in the mPFC, and these processes are spatially related to neuronal activation. Moreover, we report a significant association of microglial inflammatory responses with susceptibility or resilience to chronic stress. In addition, we find that exposure to chronic stress exacerbates phagocytosis of synaptic elements and deficits in neuronal plasticity. Importantly, by utilizing two different CSF1R inhibitors (the brain penetrant PLX5622 and the non-penetrant PLX73086) we highlight a crucial role for microglia (and secondarily macrophages) in catalyzing the pathological manifestations linked to psychosocial stress in the mPFC and the resulting behavioral deficits usually associated with depression.

The impact of placental genomic risk for schizophrenia and birth asphyxia on brain development

The placenta plays a role in fetal brain development, and pregnancy and birth complications can be signs of placental dysfunction. Birth asphyxia is associated with smaller head size and higher risk of developing schizophrenia (SZ), but whether birth asphyxia and placental genomic risk factors associated with SZ are related and how they might impact brain development is unclear. 433 adult patients with SZ and 870 healthy controls were clinically evaluated and underwent brain magnetic resonance imaging. Pregnancy and birth information were obtained from the Medical Birth Registry of Norway. Polygenic risk scores (PRS) from the latest genome-wide association study in SZ were differentiated into placental PRS (PlacPRS) and non-placental PRS. If the interaction between PRSs and birth asphyxia on case-control status was significant, neonatal head circumference (nHC) and adult intracranial volume (ICV) were further evaluated with these variables using multiple regression. PlacPRS in individuals with a history of birth asphyxia was associated with a higher likelihood of being a patient with SZ (t = 2.10, p = 0.018). We found a significant interaction between PlacPRS and birth asphyxia on nHC in the whole sample (t = -2.43, p = 0.008), with higher placental PRS for SZ associated with lower nHC in those with birth asphyxia. This relationship was specific to males (t = -2.71, p = 0.005) and also found with their adult ICV (t = -1.97, p = 0.028). These findings suggest that placental pathophysiology and birth asphyxia may affect early and late trajectories of brain development, particularly in males with a higher vulnerability to SZ. This knowledge might lead to new strategies of treatment and prevention in SZ.

An update on potential pharmacotherapies for cognitive impairment in bipolar disorder

INTRODUCTION

Cognitive impairment is a core feature of bipolar disorder (BD) that impedes recovery by preventing the return to optimal socio-occupational functioning and reducing quality of life. Presently, there are no efficacious treatments for cognitive impairment in BD, but many pharmacological interventions are being considered as they have the potential to target the underlying pathophysiology of the disorder.

AREAS COVERED

This review summarizes the available evidence for pharmacological interventions for cognitive impairment in bipolar disorder. We searched PubMed, MedLine, and PsycInfo from inception to December 1^st, 2022. Traditional treatments, such as lithium, anticonvulsants (lamotrigine), antipsychotics (aripiprazole, asenapine, cariprazine, lurasidone, and olanzapine), antidepressants (vortioxetine, fluoxetine, and tianeptine) and psychostimulants (modafinil), and emerging interventions, such as acetylcholinesterase inhibitors (galantamine and donepezil), dopamine agonists (pramipexole), erythropoietin, glucocorticoid receptor antagonists (mifepristone), immune modulators (infliximab, minocycline and doxycycline), ketamine, metabolic agents (insulin, metformin, and liraglutide), probiotic supplements, and Withania somnifera are discussed.

EXPERT OPINION

The investigation of interventions for cognitive impairment in BD is a relatively under-researched area. In the past, methodological pitfalls in BD cognition trials have also been a critical limiting factor. Expanding on the existing literature and identifying novel pharmacological and non-pharmacological treatments for cognitive impairment in BD should be a priority.

Role of group II metabotropic glutamate receptors in ketamine's antidepressant actions

Major Depressive Disorder (MDD) is a serious neuropsychiatric disorder afflicting around 16-17 % of the global population and is accompanied by recurrent episodes of low mood, hopelessness and suicidal thoughts. Current pharmacological interventions take several weeks to even months for an improvement in depressive symptoms to emerge, with a significant percentage of individuals not responding to these medications at all, thus highlighting the need for rapid and effective next-generation treatments for MDD. Pre-clinical studies in animals have demonstrated that antagonists of the metabotropic glutamate receptor subtype 2/3 (mGlu_2/3 receptor) exert rapid antidepressant-like effects, comparable to the actions of ketamine. Therefore, it is possible that mGlu₂ or mGlu₃ receptors to have a regulatory role on the unique antidepressant properties of ketamine, or that convergent intracellular mechanisms exist between mGlu_2/3 receptor signaling and ketamine's effects. Here, we provide a comprehensive and critical evaluation of the literature on these convergent processes underlying the antidepressant action of mGlu_2/3 receptor inhibitors and ketamine. Importantly, combining sub-threshold doses of mGlu_2/3 receptor inhibitors with sub-antidepressant ketamine doses induce synergistic antidepressant-relevant behavioral effects. We review the evidence supporting these combinatorial effects since sub-effective dosages of mGlu_2/3 receptor antagonists and ketamine could reduce the risk for the emergence of significant adverse events compared with taking normal dosages. Overall, deconvolution of ketamine's pharmacological targets will give critical insights to influence the development of next-generation antidepressant treatments with rapid actions.

A case-control study on the driving factors of childhood brain volume loss: What pediatricians must explore

BACKGROUND

The brain volume loss also known as brain atrophy is increasingly observed among children in the course of performing neuroimaging using CT scan and MRI brains. While severe forms of brain volume loss are frequently associated with neurocognitive changes due to effects on thought processing speed, reasoning and memory of children that eventually alter their general personality, most clinicians embark themselves in managing the neurological manifestations of brain atrophy in childhood and less is known regarding the offending factors responsible for developing pre-senile brain atrophy. It was therefore the goal of this study to explore the factors that drive the occurrence of childhood brain volume under the guidance of brain CT scan quantitative evaluation.

METHODS

This study was a case-control study involving 168 subjects with brain atrophy who were compared with 168 age and gender matched control subjects with normal brains on CT scan under the age of 18 years. All the children with brain CT scan were subjected to an intense review of their birth and medical history including laboratory investigation reports.

RESULTS

Results showed significant and influential risk factors for brain atrophy in varying trends among children including age between 14-17(OR = 1.1), male gender (OR = 1.9), birth outside facility (OR = 0.99), immaturity (OR = 1.04), malnutrition (OR = 0.97), head trauma (OR = 1.02), maternal alcoholism (OR = 1.0), antiepileptic drugs & convulsive disorders (OR = 1.0), radiation injury (OR = 1.06), space occupying lesions and ICP (OR = 1.01) and birth injury/asphyxia (OR = 1.02).

CONCLUSIONS

Pathological reduction of brain volume in childhood exhibits a steady trend with the increase in pediatric age, with space occupying lesions & intracranial pressure being the most profound causes of brain atrophy.

Machine learning algorithms revealed distorted retinal vascular branching in individuals with bipolar disorder

BACKGROUND

Converging evidence designate vascular vulnerability in bipolar disorder. The predisposition progresses into distortion in time, thus detection of the vascular susceptibility may help reducing morbidity and mortality. It was aimed to assess retinal fundus vasculature in cardiovascular risk-free patients with bipolar disorder.

METHODS

Total of 68 individuals (38 patients with bipolar disorder, 30 healthy controls) were enrolled. In order to avoid from degenerative processes, participants were between 18 and 45 years of age, vascular risk factors were eliminated. Microscopic retinal fundus images were processed with machine learning algorithms (multilayer perceptron and support vector machine) and artificial neural network approaches.

RESULTS

In comparison to the healthy control group, the bipolar disorder group had lower number of breaking points (P < 0.001), lower number of curved vessel segments (P < 0.001). Total length of smooth vessels was longer (P = 0.040), and total length of curved vessel segments was significantly shorter (P < 0.001) than the control group. Vascular endothelial growth factor levels and gender were the confounders. There were significant correlations between vascular measures and serum lipid levels.

LIMITATIONS

Sample size was small and patients were on various medications.

CONCLUSIONS

These results indicate distortion in retinal vascular branching in bipolar disorder. Disrupted branching may reflect disturbed prosperity of retinal vascular plexus in patients with bipolar disorder. Alterations in the retinal vessels might be indicators of disruption in cerebral vascular system efficiency and thus neurovascular unit dysfunction in bipolar disorder.

Targeting NMDA Receptors in Emotional Disorders: Their Role in Neuroprotection

Excitatory glutamatergic neurotransmission mediated through N-methyl-D-Aspartate (NMDA) receptors (NMDARs) is essential for synaptic plasticity and neuronal survival. While under pathological states, abnormal NMDAR activation is involved in the occurrence and development of psychiatric disorders, which suggests a directional modulation of NMDAR activity that contributes to the remission and treatment of psychiatric disorders. This review thus focuses on the involvement of NMDARs in the pathophysiological processes of psychiatric mood disorders and analyzes the neuroprotective mechanisms of NMDARs. Firstly, we introduce NMDAR-mediated neural signaling pathways in brain function and mood regulation as well as the pathophysiological mechanisms of NMDARs in emotion-related mental disorders such as anxiety and depression. Then, we provide an in-depth summary of current NMDAR modulators that have the potential to be developed into clinical drugs and their pharmacological research achievements in the treatment of anxiety and depression. Based on these findings, drug-targeting for NMDARs might open up novel territory for the development of therapeutic agents for refractory anxiety and depression.

The Actions of Lithium on Glaucoma and Other Senile Neurodegenerative Diseases Through GSK-3 Inhibition: A Narrative Review

Glaucoma can be described as a set of progressive optic neuropathies. They cause a gradual, irreversible loss of the field of view, which concludes in complete blindness. Evidence suggests that patients who have glaucoma face a greater risk of suffering from senile dementia. Dementia is a group of conditions that occur in old age individuals. Neurodegeneration is a characteristic pathological feature of dementia, the progression of which causes a decline in cognition, which may be accompanied by memory loss. Severe dementia in old individuals usually presents as Alzheimer’s disease, which significantly contributes to a load of dementia in India. Parkinsonism is another common neurodegenerative disease that is known to occur in the elderly.

The WNT (Wingless-related integration site)/β-catenin pathway is a multistep process that is responsible for the regulation of various cellular functions. Lithium can up-regulate this pathway by disrupting Glycogen synthase kinase-3β (GSK-3β). This action of Lithium can effectively counteract neuroinflammation and neurodegeneration. The current use of Lithium remains majorly confined to its use for episodes of mania in bipolar disorder (BD). However, recent literature gives insight into how Lithium can improve the visual field in glaucomatous eyes. Symptomatic improvement after lithium administration is seen as it has neuroprotective actions on the retinal ganglion cells (RGCs). Prolonged lithium use improves axonal regeneration and neuronal survival. Lithium also improves the worsening of symptoms in other dementia-related neurodegenerative diseases like Alzheimer’s and Parkinsonism. The physiological actions of Lithium can be utilized in providing effective, holistic therapy options in pathologically related senile degenerative disorders. Significantly better results can be obtained if Lithium therapy is given in conjunction with the drugs used to manage these disorders.

A Double-Blind Placebo-Controlled, Randomized Trial of Divalproex Sodium for Posttraumatic Irritability Greater Than 1 Year After Mild to Moderate Traumatic Brain Injury

OBJECTIVE

Posttraumatic irritability after traumatic brain injury (TBI) may become a chronic problem and contribute to impaired everyday function, either alone or in combination with alcohol use disorder. The authors hypothesized that divalproex sodium (VPA) would improve posttraumatic irritability and result in lessened alcohol use.

METHODS

This randomized, placebo-controlled double-blind clinical trial recruited participants with an index TBI occurring 1 or more years prior to enrollment, a history of alcohol use disorder, and posttraumatic irritability corroborated by a knowledgeable informant. An 8-item subset of the Agitated Behavior Scale served as the primary outcome measure of VPA efficacy. Doses of VPA were titrated to standard serum concentrations of 50 µg/ml to 100 µg/ml.

RESULTS

Forty-eight persons completed this clinical trial (VPA, N=22; placebo, N=26). At baseline, participants rated their posttraumatic irritability as less severe than did their informants (p<0.05). During the trial, informants reported significant and sustained reduction of posttraumatic irritability (p=0.03) in the study participants. Biweekly averages during drug exposure confirmed this (p<0.03, Cohen's d=0.44). Treatment efficacy was not related to measures of anxiety, posttraumatic stress disorder, sedation, or veteran versus nonveteran status. Alcohol use did not change as a result of treatment. There were no serious adverse events.

CONCLUSIONS

This study demonstrated an effect of VPA on posttraumatic irritability, and VPA was well tolerated. Further definition of treatment efficacy and safety requires a large-scale multisite trial, using a randomized, double-blind placebo-controlled design.

Predictive Value of Acute Neuroplastic Response to rTMS in Treatment Outcome in Depression: A Concurrent TMS-fMRI Trial

OBJECTIVE

The study objective was to investigate the predictive value of functional connectivity changes induced by acute repetitive transcranial magnetic stimulation (rTMS) for clinical response in treatment-resistant depression.

METHODS

Cross-sectional changes in functional connectivity induced by a single concurrent rTMS-fMRI session were assessed in 38 outpatients with treatment-resistant depression (26 of them female; mean age, 41.87 years) who subsequently underwent a 4-week course of rTMS. rTMS was delivered at 1 Hz over the right dorsolateral prefrontal cortex. Acute rTMS-induced functional connectivity changes were computed and subjected to connectome-based predictive modeling to test their association with changes in score on the Montgomery-Åsberg Depression Rating Scale (MADRS) after rTMS treatment.

RESULTS

TMS-fMRI induced widespread, acute, and transient alterations in functional connectivity. The rTMS-induced connectivity changes predicted about 30% of the variance of improvement in the MADRS score. The most robust predictive associations involved connections between prefrontal regions and motor, parietal, and insular cortices and between bilateral regions of the thalamus.

CONCLUSIONS

Acute rTMS-induced connectivity changes in patients with treatment-resistant depression may index macro-level neuroplasticity, relevant to interindividual variability in rTMS treatment response. Large-scale network phenomena occurring during rTMS might be used to inform prospective clinical trials.

Neuromolecular Etiology of Bipolar Disorder: Possible Therapeutic Targets of Mood Stabilizers

Bipolar disorder is a mental illness that causes extreme mood swings and has a chronic course. However, the mechanism by which mood episodes with completely opposite characteristics appear repeatedly, or a mixture of symptoms appears, in patients with bipolar disorder remains unknown. Therefore, mood stabilizers are indicated only for single mood episodes, such as manic episodes and depressive episodes, and no true mood-stabilizing drugs effective for treating both manic and depressive episodes currently exist. Therefore, in this review, therapeutic targets that facilitate the development of mood stabilizers were examined by reviewing the current understanding of the neuromolecular etiology of bipolar disorder.

Effects of photoperiod and diet on BDNF daily rhythms in diurnal sand rats

Brain-derived neurotrophic factor (BDNF), its receptors and epigenetic modulators, are implicated in the pathophysiology of affective disorders, T2DM and the circadian system function. We used diurnal sand rats, which develop type 2 diabetes (T2DM), anxiety and depressive-like behavior under laboratory conditions. The development of these disorders is accelerated when animals are maintained under short photoperiod (5:19L:D, SP) compared to neutral photoperiod (12:12L:D, NP). We compared rhythms in plasma BDNF as well as BDNF and PER2 expression in the frontal cortex and suprachiasmatic nucleus (SCN) of sand rats acclimated to SP and NP. Acclimation to SP resulted in higher insulin levels, significantly higher glucose levels in the glucose tolerance test, and significantly higher anxiety- and depression-like behaviors compared with animals acclimated to NP. NP Animals exhibited a significant daily rhythm in plasma BDNF levels with higher levels during the night, and in BDNF expression levels in the frontal cortex and SCN. No significant BDNF rhythm was found in the plasma, frontal cortex or SCN of SP acclimated animals. We propose that in sand rats, BDNF may, at least in part, mediate the effects of circadian disruption on the development of anxiety and depressive-like behavior and T2DM.

Beyond New Neurons in the Adult Hippocampus: Imipramine Acts as a Pro-Astrogliogenic Factor and Rescues Cognitive Impairments Induced by Stress Exposure

Depression is a prevalent, socially burdensome disease. Different studies have demonstrated the important role of astrocytes in the pathophysiology of depression as modulators of neurotransmission and neurovascular coupling. This is evidenced by astrocyte impairments observed in brains of depressed patients and the appearance of depressive-like behaviors upon astrocytic dysfunctions in animal models. However, little is known about the importance of de novo generated astrocytes in the mammalian brain and in particular its possible involvement in the precipitation of depression and in the therapeutic actions of current antidepressants (ADs). Therefore, we studied the modulation of astrocytes and adult astrogliogenesis in the hippocampal dentate gyrus (DG) of rats exposed to an unpredictable chronic mild stress (uCMS) protocol, untreated and treated for two weeks with antidepressants—fluoxetine and imipramine. Our results show that adult astrogliogenesis in the DG is modulated by stress and imipramine. This study reveals that distinct classes of ADs impact differently in the astrogliogenic process, showing different cellular mechanisms relevant to the recovery from behavioral deficits induced by chronic stress exposure. As such, in addition to those resident, the newborn astrocytes in the hippocampal DG might also be promising therapeutic targets for future therapies in the neuropsychiatric field.

TGF-β/Smad Signalling in Neurogenesis: Implications for Neuropsychiatric Diseases

TGF-β/Smad signalling has been the subject of extensive research due to its role in the cell cycle and carcinogenesis. Modifications to the TGF-β/Smad signalling pathway have been found to produce disparate effects on neurogenesis. We review the current research on canonical and non-canonical TGF-β/Smad signalling pathways and their functions in neurogenesis. We also examine the observed role of neurogenesis in neuropsychiatric disorders and the relationship between TGF-β/Smad signalling and neurogenesis in response to stressors. Overlapping mechanisms of cell proliferation, neurogenesis, and the development of mood disorders in response to stressors suggest that TGF-β/Smad signalling is an important regulator of stress response and is implicated in the behavioural outcomes of mood disorders.

Lithium and Atypical Antipsychotics: The Possible WNT/β Pathway Target in Glaucoma

Glaucoma is a progressive neurodegenerative disease that represents the major cause of irreversible blindness. Recent findings have shown which oxidative stress, inflammation, and glutamatergic pathway have main roles in the causes of glaucoma. Lithium is the major commonly used drug for the therapy of chronic mental illness. Lithium therapeutic mechanisms remain complex, including several pathways and gene expression, such as neurotransmitter and receptors, circadian modulation, ion transport, and signal transduction processes. Recent studies have shown that the benefits of lithium extend beyond just the therapy of mood. Neuroprotection against excitotoxicity or brain damages are other actions of lithium. Moreover, recent findings have investigated the role of lithium in glaucoma. The combination of lithium and atypical antipsychotics (AAPs) has been the main common choice for the treatment of bipolar disorder. Due to the possible side effects gradually introduced in therapy. Currently, no studies have focused on the possible actions of AAPs in glaucoma. Recent studies have shown a down regulation of the WNT/β-catenin pathway in glaucoma, associated with the overactivation of the GSK-3β signaling. The WNT/β-catenin pathway is mainly associated with oxidative stress, inflammation and glutamatergic pathway. Lithium is correlated with upregulation the WNT/β-catenin pathway and downregulation of the GSK-3β activity. Thus, this review focuses on the possible actions of lithium and AAPs, as possible therapeutic strategies, on glaucoma and some of the presumed mechanisms by which these drugs provide their possible benefit properties through the WNT/β-catenin pathway.

Akkouh I, Hughes T, Frei E, A. Andreassen O, Djurovic S. Using iPSC Models to Understand the Role of Estrogen in Neuron-Glia Interactions in Schizophrenia and Bipolar Disorder

Schizophrenia (SCZ) and bipolar disorder (BIP) are severe mental disorders with a considerable disease burden worldwide due to early age of onset, chronicity, and lack of efficient treatments or prevention strategies. Whilst our current knowledge is that SCZ and BIP are highly heritable and share common pathophysiological mechanisms associated with cellular signaling, neurotransmission, energy metabolism, and neuroinflammation, the development of novel therapies has been hampered by the unavailability of appropriate models to identify novel targetable pathomechanisms. Recent data suggest that neuron-glia interactions are disturbed in SCZ and BIP, and are modulated by estrogen (E2). However, most of the knowledge we have so far on the neuromodulatory effects of E2 came from studies on animal models and human cell lines, and may not accurately reflect many processes occurring exclusively in the human brain. Thus, here we highlight the advantages of using induced pluripotent stem cell (iPSC) models to revisit studies of mechanisms underlying beneficial effects of E2 in human brain cells. A better understanding of these mechanisms opens the opportunity to identify putative targets of novel therapeutic agents for SCZ and BIP. In this review, we first summarize the literature on the molecular mechanisms involved in SCZ and BIP pathology and the beneficial effects of E2 on neuron-glia interactions. Then, we briefly present the most recent developments in the iPSC field, emphasizing the potential of using patient-derived iPSCs as more relevant models to study the effects of E2 on neuron-glia interactions.

Me, myself, bye: regional alterations in glutamate and the experience of ego dissolution with psilocybin

There is growing interest in the therapeutic utility of psychedelic substances, like psilocybin, for disorders characterized by distortions of the self-experience, like depression. Accumulating preclinical evidence emphasizes the role of the glutamate system in the acute action of the drug on brain and behavior; however this has never been tested in humans. Following a double-blind, placebo-controlled, parallel group design, we utilized an ultra-high field multimodal brain imaging approach and demonstrated that psilocybin (0.17 mg/kg) induced region-dependent alterations in glutamate, which predicted distortions in the subjective experience of one's self (ego dissolution). Whereas higher levels of medial prefrontal cortical glutamate were associated with negatively experienced ego dissolution, lower levels in hippocampal glutamate were associated with positively experienced ego dissolution. Such findings provide further insights into the underlying neurobiological mechanisms of the psychedelic, as well as the baseline, state. Importantly, they may also provide a neurochemical basis for therapeutic effects as witnessed in ongoing clinical trials.

The Wistar-Kyoto rat model of endogenous depression: A tool for exploring treatment resistance with an urgent need to focus on sex differences

Major depressive disorder (MDD) is one of the leading causes of years lived with disability and contributor to the burden of disease worldwide. The incidence of MDD has increased by ~20% in the last decade. Currently antidepressant drugs such as the popular selective serotonin reuptake inhibitors (SSRIs) are the leading form of pharmaceutical intervention for the treatment of MDD. SSRIs however, are inefficient in ameliorating depressive symptoms in ~50% of patients and exhibit a prolonged latency of efficacy. Due to the burden of disease, there is an increasing need to understand the neurobiology underpinning MDD and to discover effective treatment strategies. Endogenous models of MDD, such as the Wistar-Kyoto (WKY) rat provide a valuable tool for investigating the pathophysiology of MDD. The WKY rat displays behavioural and neurobiological phenotypes similar to that observed in clinical cases of MDD, as well as resistance to common antidepressants. Specifically, the WKY strain exhibits increased anxiety- and depressive-like behaviours, as well as alterations in Hypothalamic Pituitary Adrenal (HPA) axis, serotonergic, dopaminergic and neurotrophic systems with emerging studies suggesting an involvement of neuroinflammation. More recent investigations have shown evidence for reduced cortical and hippocampal volumes and altered glutamatergic signalling in the WKY strain. Given the growing interest in therapeutics targeting the glutamatergic system, the WKY strain presents itself as a potentially useful tool for screening novel antidepressant drugs and their efficacy against treatment resistant depression. However, despite the sexual dimorphism present in the pathophysiology and aetiology of MDD, sex differences in the WKY model are rarely investigated, with most studies focusing on males. Accordingly, this review highlights what is known regarding sex differences and where further research is needed. Whilst acknowledging that investigation into a range of depression models is required to fully elucidate the underlying mechanisms of MDD, here we review the WKY strain, and its relevance to the clinic.

Assessment of glutamatergic synaptic transmission and plasticity in brain slices: relevance to bioelectronic approaches

Background

Glutamatergic neurons represent the largest neuronal class in the brain and are responsible for the bulk of excitatory synaptic transmission and plasticity. Abnormalities in glutamatergic neurons are linked to several brain disorders and their modulation represents a potential opportunity for emerging bioelectronic medicine (BEM) approaches. Here, we have used a set of electrophysiological assays to identify the effect of the pyrimidine nucleoside uridine on glutamatergic systems in ex vivo brain slices. An improved understanding of glutamatergic synaptic transmission and plasticity, through this type of examination, is critical to the development of potential neuromodulation strategies.

Methods

Ex vivo hippocampal slices (400 μm thick) were prepared from mouse brain. We recorded field excitatory postsynaptic potentials (fEPSP) in the CA1’s stratum radiatum by stimulation of the CA3 Schaeffer collateral/commissural axons. Uridine was applied at concentrations (3, 30, 300 μM) representing the physiological range present in brain tissue. Synaptic function was studied with input-output (I-O) functions, as well as paired-pulse facilitation (PPF). Synaptic plasticity was studied by applying tetanic stimulation to induce post-tetanic potentiation (PTP), short-term potentiation (STP) and long-term potentiation (LTP). Additionally, we determined whether uridine affected synaptic responses carried solely by n-methyl-d-aspartate receptors (NMDARs), particularly during the oxygen-glucose deprivation (OGD) paradigm.

Results

The presence of uridine altered glutamatergic synaptic transmission and plasticity. We found that uridine affected STP and LTP in a concentration-dependent manner. Low-dose uridine (3 μM) had no effect, but higher doses (30 and 300 μM) impaired STP and LTP. Moreover, uridine (300 μM) decreased NMDAR-mediated synaptic responses. Conversely, uridine (at all concentrations tested) had a negligible effect on PPF and basal synaptic transmission, which is mediated primarily by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). In addition, uridine (100 μM) exerted a protective effect when the hippocampal slices were challenged with OGD, a widely used model of cerebral ischemia.

Conclusions

Using a wide set of electrophysiological assays, we identify that uridine interacts with glutamatergic neurons to alter NMDAR-mediated responses, impair synaptic STP and LTP in a dose-dependent manner, and has a protective effect against OGD insult. This work outlines a strategy to identify deficits in glutamatergic mechanisms for signaling and plasticity that may be critical for targeting these same systems with BEM device-based approaches. To improve the efficacy of potential neuromodulation approaches for treating brain dysfunction, we need to improve our understanding of glutamatergic systems in the brain, including the effects of modulators such as uridine.

Antidepressant-like effects of ketamine in a mouse model of serotonergic dysfunction

Traditional monoaminergic treatments of depression frequently exhibit suboptimal tolerability and effectiveness. The 'short' (s) allele variant of 5-HTTLPR is known to compromise transcriptional efficacy of the serotonin transporter (5-HTT) and can reduce treatment response to traditional antidepressants (e.g. selective serotonin reuptake inhibitors or SSRIs). This study sought to establish the 5-HTT knock-out (KO) line as a mouse model of SSRI-resistant depression and assess its response to a novel glutamatergic antidepressant, ketamine, a non-competitive N-methyl-d-aspartate receptor (NMDAR) antagonist. Following acute antidepressant treatment, 5-HTT KO mice and wild-type (WT) controls were subjected to the forced-swim test (FST), one of the most widely used techniques to detect acute antidepressant response. As hypothesised, when assessed 30 min after administration in the FST, the SSRI sertraline (20 mg/kg, i.p.) produced antidepressant-like effects in WT control but not in 5-HTT KO mice. In contrast, ketamine (20 mg/kg, i.p.) induced antidepressant-like effects in both genotypes. 5-HTT KO mice also exhibited a reduced locomotor response to both MK-801 (another NMDAR antagonist) and ketamine, and reduced GluN2A protein levels in the hippocampus, suggesting glutamatergic dysfunction in this model. These results highlight the utility of 5-HTT KO mice as a relevant model of SSRI-resistant depression and demonstrate that ketamine can produce acute antidepressant-like effects in conditions of 5-HTT deficiency. These findings extend existing literature that indicates ketamine is effective in ameliorating symptoms of treatment-resistant depression and may have implications for understanding the cellular and molecular mechanisms underlying the antidepressant effects of ketamine. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

Current understandings of the trajectory and emerging correlates of cognitive impairment in bipolar disorder: An overview of evidence

OBJECTIVES

Cognitive dysfunction affects a significant proportion of people with bipolar disorder (BD), but the cause, trajectory and correlates of such dysfunction remains unclear. Increased understanding of these factors is required to progress treatment development for this symptom dimension.

METHODS

This paper provides a critical overview of the literature concerning the trajectories and emerging correlates of cognitive functioning in BD. It is a narrative review in which we provide a qualitative synthesis of current evidence concerning clinical, molecular, neural and lifestyle correlates of cognitive impairment in BD across the lifespan (in premorbid, prodromal, early onset, post-onset, elderly cohorts).

RESULTS

There is emerging evidence of empirical links between cognitive impairment and an increased inflammatory state, brain structural abnormalities and reduced neuroprotection in BD. However, evidence regarding the progressive nature of cognitive impairment is mixed, since consensus between different cross-sectional data is lacking and does not align to the outcomes of the limited longitudinal studies available. Increased recognition of cognitive heterogeneity in BD may help to explain some inconsistencies in the extant literature.

CONCLUSIONS

Large, longitudinally focussed studies of cognition and its covariation alongside biological and lifestyle factors are required to better define cognitive trajectories in BD, and eventually pave the way for the application of a precision medicine approach for individual patients in clinical practice.

Neuroinflammation in Bipolar Depression

Bipolar disorder (BD) is a leading cause of worldwide disability among mood disorders. Pathological mechanisms are still vastly unclear, and current treatments with conventional medications are often unsatisfactory in maintaining symptoms control and an adequate quality of life. Consequently, current research is focusing on shedding new light on disease pathogenesis, to improve therapeutic effectiveness. Recent evidence has suggested a prominent role of inflammation in mood disorders. Elevated levels of peripheral proinflammatory mediators have been reported in BD, as well as in other mood disorders, and people with systemic autoimmune diseases have an increased risk of developing BD. These immunological alterations are stable, and current medications are unable to alter peripheral concentrations even when clinical improvement is evident. These findings have also been replicated in the central nervous system (CNS) milieu, whereas genetic studies have shown that these immune alterations are not due to the disorder itself, being detectable before the illness onset. Moreover, these inflammatory modifications seem to be affected by and linked to other biomarkers of the disorder, such as alterations of white matter (WM) microstructure, metabolism, kynurenine pathway, and circadian rhythmicity. Finally, these immune variations seem to be useful as predictors of therapeutic responsiveness to medications, and in discriminating between clinically different outcomes. The objective of this review is to summarize available evidence on the connection between inflammation and BD, focusing on peripheral inflammatory markers and recent findings on their connection with other typical features of BD, to outline a general overview of the disorder. Moreover, it is meant to analyze the issues with data gathering and interpretation, given the partially contradictory and inconsistent nature of results.

CACNA1C Gene rs11832738 Polymorphism Influences Depression Severity by Modulating Spontaneous Activity in the Right Middle Frontal Gyrus in Patients With Major Depressive Disorder

OBJECTIVES

This study aimed to examine whether the CACNA1C gene rs11832738 polymorphism and major depressive disorder (MDD) have an interactive effect on the untreated regional amplitude of low-frequency fluctuation (ALFF) and to determine whether regional ALFF mediates the association between CACNA1C rs11832738 and MDD.

METHODS

A total of 116 patients with MDD and 66 normal controls (NCs) were recruited. The MDD and NC groups were further divided into two groups according to genotype: carriers of the G allele (G-carrier group, GG/GA genotypes; MDD, n = 61; NC, n = 26) and AA homozygous group (MDD, n = 55; NC, n = 40). MDD was diagnosed based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Depression severity was assessed using the Hamilton Depression Scale-24 (HAMD-24) at baseline and follow-up (after 2 and 8 weeks of treatment). All subjects underwent functional MRI (fMRI) scans at baseline, and the ALFF was calculated to reflect spontaneous brain activity. The interactions between MDD and CACNA1C single nucleotide polymorphism rs11832738 were determined using two-way factorial analysis of covariance, with age, sex, education, and head motion as covariates. We performed mediation analysis to further determine whether regional ALFF strength could mediate the associations between rs11832738 and depression severity, MDD treatment efficacy.

RESULTS

MDD had a main effect on regional ALFF distribution in three brain areas: the right medial frontal gyrus (MFG_R), the left anterior cingulate cortex (ACC_L), and the right cerebellum posterior lobe (CPL_R); CACNA1C showed a significant interactive effect with MDD on the ALFF of MFG_R. For CACNA1C G allele carriers, the ALFF of MFG_R had a significant positive correlation with the baseline HAMD-24 score. Exploratory mediation analysis revealed that the intrinsic ALFF in MFG_R significantly mediated the association between the CACNA1C rs11832738 polymorphism and baseline HAMD-24 score.

CONCLUSIONS

A genetic variant in CACNA1C rs11832738 may influence depression severity in MDD patients by moderating spontaneous MFG_R activity.

S100 calcium-binding protein B in older patients with depression treated with electroconvulsive therapy

BACKGROUND

Increasing evidence suggests that glial mediated disruption of neuroplasticity contributes to depression. S100 calcium-binding protein B (S100B) promotes neuronal protection in nanomolar concentrations. Studies on its possible role as a treatment outcome marker in affective disorders are limited. Recent evidence suggests a putative role for S100B as a state marker of illness activity as it is found elevated in episodes of major depression.

AIM

To investigate whether higher S100B is associated with favourable treatment outcome following electroconvulsive therapy (ECT) and to further explore whether S100B reflects a state marker of depression activity.

METHODS

Serum S100B samples, at baseline and post-ECT and clinical assessments including Montgomery Åsberg Rating scales were collected in 91 older depressed patients (mean age: 73.0 years), referred for ECT. Change in pre- and post-ECT S100B was compared between remitters and nonremitters. Logistic and Cox regression analyses were used to determine whether S100B was associated with remission of depression.

RESULTS

Patients with S100B levels in the intermediate tertile, that is, between 33 ng/L and 53 ng/L, had higher odds on remission, odds ratio: 5.5 (95%Confidence Interval (CI): 1.55-19.20, p = <0.01), and were more likely to remit from depression over time, hazard ratio: 1.96 (95%CI: 1.04-3.72, p = 0.04), compared with patients in the lowest tertile. There was no significant decrease in levels of S100B after ECT in both remitters and nonremitters.

CONCLUSION

Our findings demonstrate that patients with higher S100B levels at baseline were more likely to remit from depression suggesting an association between higher S100B and responsiveness to ECT. Next, S100B levels do not decrease after remission, suggesting S100B is not a state marker of depression. S100B is not capable of predicting treatment outcome by itself, further research may combine outcome markers.

Structural variation in the glycogen synthase kinase 3β and brain-derived neurotrophic factor genes in Japanese patients with bipolar disorders

Background

Lithium is the first‐line drug for the treatment of bipolar disorders (BDs); however, not all patients responded. Glycogen synthase kinase (GSK) 3β and brain‐derived neurotrophic factor (BDNF) play a role in the therapeutic action of lithium. Since structural variations were reported in these genes, it is possible that these genomic variations may be involved in the therapeutic responses to lithium.

Method

Fifty patients with BDs and 50 healthy subjects (mean age 55.0 ± 15.0 years; M/F 19/31) participated. We examined structural variation of the GSK3β and BDNF genes by real‐time PCR. We examined the influence of structural variation of these genes on the therapeutic responses to lithium and the occurrence of antidepressant‐emergent affective switch (AEAS). The efficacy of lithium was assessed using the Alda scale, and AEAS was evaluated using Young Mania Rating Scale.

Results

Although we examined structural variations within intron II and VII of the GSK3^® gene and from the end of exon IV to intron IV and within exon IX of the BDNF gene, no structural variation was found in BDs. Whereas 5 of 50 patients exhibited three copies of the genomic region within exon IV of the BDNF gene, all healthy subjects had two copies. No difference in the therapeutic efficacy of lithium was found between patients with three and two copies. No difference in the occurrence of AEAS was found between the two groups.

Conclusion

The amplification of the BDNF gene influenced neither the therapeutic responses to lithium nor the occurrence of AEAS.

Five of 50 patients with bipolar disorders exhibited three copies of the genomic region within exon IV of the BDNF gene. But, 50 healthy subjects had two copies. This amplification did not affect the therapeutic responses to lithium.

Astrocytic plasticity at the dorsal dentate gyrus on an animal model of recurrent depression

Astrocytes are now known to play crucial roles in the central nervous system, supporting and closely interacting with neurons and therefore able to modulate brain function. Both human postmortem studies in brain samples from patients diagnosed with Major Depressive Disorder and from animal models of depression reported numerical and morphological astrocytic changes specifically in the hippocampus. In particular, these studies revealed significant reductions in glial cell density denoted by a decreased number of S100B-positive cells and a decrease in GFAP expression in several brain regions including the hippocampus. To reveal plastic astrocytic changes in the context of recurrent depression, we longitudinally assessed dynamic astrocytic alterations (gene expression, cell densities and morphologic variations) in the hippocampal dentate gyrus under repeated exposure to unpredictable chronic mild stress (uCMS) and upon treatment with two antidepressants, fluoxetine and imipramine. Both antidepressants decreased astrocytic complexity immediately after stress exposure. Moreover, we show that astrocytic alterations, particularly an increased number of S100B-positive cells, are observed after recurrent stress exposure. Interestingly, these alterations were prevented at the long-term by either fluoxetine or imipramine treatment.

Natural killer cells protect white matter integrity in bipolar disorder

BACKGROUND

Bipolar Disorder (BD) associates with disrupted white matter (WM) microstructure and functional connectivity, and with a perturbation of the immune system. Higher cytokines, and reduced T cells, correlated with WM disruption and fMRI responses. A core component of the innate immune system, natural killer (NK) cells were detected in brain parenchyma, but never studied in BD.

METHODS

We studied Diffusion Tensor Imaging (DTI) measures of water diffusion, fMRI corticolimbic functional response and connectivity, and multi-parameter cytofluorometry analysis of NK (CD56⁺) subpopulations, in 30 inpatients with active Bipolar Disorder type I. NK cells were also obtained in 36 healthy controls.

RESULTS

Patients had significantly higher circulating counts of CD56⁺GMCSF⁺, CD56⁺INFγ⁺, and CD56⁺IL17⁺. NK cell levels positively associated to fractional anisotropy (FA) measures. CD56⁺TNFα⁺, CD56⁺INFγ⁺, and CD56⁺GMCSF⁺ directly correlated with FA, and inversely with radial (RD) and mean (MD) diffusivity. Duration of lithium treatment associated with higher CD56⁺TNFα⁺, CD56⁺IL2⁺, and CD56⁺IL4⁺, and positively associated with FA in tracts were NKs had significant effects. A mediation model suggested a partial mediation of CD56⁺TNFα⁺ cells, higher in patients on lithium, on the effects of lithium on FA. Frequencies of the same cytokine-producing NK cells also influenced fMRI cortico-limbic functional connectivity during processing of both, emotional and non-emotional stimuli.

DISCUSSION

Higher circulating cytokine-producing NK cells associated with lithium treatment, and with DTI measures of WM integrity, partially mediating the effect of lithium on WM. The same cells associated with fMRI responses and connectivity, thus suggesting an effect on structural and functional connectomics in BD.

Nitric oxide signalling and antidepressant action revisited

Studies about the pathogenesis of mood disorders have consistently shown that multiple factors, including genetic and environmental, play a crucial role on their development and neurobiology. Multiple pathological theories have been proposed, of which several ultimately affects or is a consequence of dysfunction in brain neuroplasticity and homeostatic mechanisms. However, current clinical available pharmacological intervention, which is predominantly monoamine-based, suffers from a partial and lacking response even after weeks of continuous treatment. These issues raise the need for better understanding of aetiologies and brain abnormalities in depression, as well as developing novel treatment strategies. Nitric oxide (NO) is a gaseous unconventional neurotransmitter, which regulates and governs several important physiological functions in the central nervous system, including processes, which can be associated with the development of mood disorders. This review will present general aspects of the NO system in depression, highlighting potential targets that may be utilized and further explored as novel therapeutic targets in the future pharmacotherapy of depression. In particular, the review will link the importance of neuroplasticity mechanisms governed by NO to a possible molecular basis for the antidepressant effects.

NO-sGC-cGMP signaling influence the anxiolytic like effect of lithium in mice in light and dark box and elevated plus maze

Glutamate is an excitatory neurotransmitter implicated in the pathogenesis of psychiatric disorders. Glutamate results in the activation of an enzyme called glycogen synthase kinase-3 (GSK-3) acting through N-methyl-d-aspartate (NMDA) receptors. Impaired expression of GSK-3 affects behavior and neurochemicals level in the brain responsible for the pathogenesis of mood disorders. It has been reported that lithium acts as an inhibitor of GSK-3 and inhibit the enzyme GSK-3 in an uncompetitive manner. In the present study, anxiolytic like effect of lithium in mice is investigated through light and dark box (LDB) and elevated plus maze (EPM). Lithium (50, 100 and 200 mg/kg, i.p.) was administered to the mice to determine the anxiety related behavior. Results obtained suggests that the administration of lithium (100 mg/kg, i.p.) reversed the anxiety related behavior of mice and decreased the levels of glutamate and nitrite as compared to control. Glutamate acting through the NMDA receptor has been found to regulate the expression of enzyme neuronal nitric oxide synthase (nNOS), which is responsible for the release of nitric oxide (NO), suggesting a possible link between NO and GSK-3 also. Therefore, to determine the possible interaction with NO, sub-effective dose of lithium was administered in combination with NO donor i.e. l-Arginine (50 mg/kg, i.p.), NOS and soluble guanylate cyclase (sGC) inhibitor i.e. methylene blue (1 mg/kg, i.p.) and phosphodiesterase inhibitor i.e. sildenafil (1 mg/kg, i.p.). The results obtained demonstrated that the anxiolytic like effect of lithium was abolished by the pretreatment with NO donor and potentiated by the pretreatment with NOS inhibitor. Therefore, it is suggested that NO signaling pathway influence the anxiolytic like activity of lithium in mice, further suggesting the link between the GSK-3 and NO signaling in the regulation of anxiety related behavior.

Toxicity, recovery, and resilience in a 3D dopaminergic neuronal in vitro model exposed to rotenone

To date, most in vitro toxicity testing has focused on acute effects of compounds at high concentrations. This testing strategy does not reflect real-life exposures, which might contribute to long-term disease outcome. We used a 3D-human dopaminergic in vitro LUHMES cell line model to determine whether effects of short-term rotenone exposure (100 nM, 24 h) are permanent or reversible. A decrease in complex I activity, ATP, mitochondrial diameter, and neurite outgrowth were observed acutely. After compound removal, complex I activity was still inhibited; however, ATP levels were increased, cells were electrically active and aggregates restored neurite outgrowth integrity and mitochondrial morphology. We identified significant transcriptomic changes after 24 h which were not present 7 days after wash-out. Our results suggest that testing short-term exposures in vitro may capture many acute effects which cells can overcome, missing adaptive processes, and long-term mechanisms. In addition, to study cellular resilience, cells were re-exposed to rotenone after wash-out and recovery period. Pre-exposed cells maintained higher metabolic activity than controls and presented a different expression pattern in genes previously shown to be altered by rotenone. NEF2L2, ATF4, and EAAC1 were downregulated upon single hit on day 14, but unchanged in pre-exposed aggregates. DAT and CASP3 were only altered after re-exposure to rotenone, while TYMS and MLF1IP were downregulated in both single-exposed and pre-exposed aggregates. In summary, our study shows that a human cell-based 3D model can be used to assess cellular adaptation, resilience, and long-term mechanisms relevant to neurodegenerative research.

Early Life Stress Associated With Increased Striatal N-Acetyl-Aspartate: Cerebrospinal Fluid Corticotropin-Releasing Factor Concentrations, Hippocampal Volume, Body Mass and Behavioral Correlates

Introduction

Using proton magnetic resonance spectroscopy imaging, the effects of early life stress on nonhuman primate striatal neuronal integrity were examined as reflected by N-acetyl aspartate (NAA) concentrations. NAA measures were interrogated through examining their relationship to previously documented early life stress markers—cerebrospinal fluid corticotropin-releasing factor concentrations, hippocampal volume, body mass, and behavioral timidity. Rodent models of depression exhibit increases in neurotrophic effects in the nucleus accumbens. We hypothesized that rearing under conditions of early life stress (variable foraging demand, VFD) would produce persistent elevations of NAA concentrations (in absolute or ratio form) in ventral striatum/caudate nucleus (VS/CN) with altered correlation to early life stress markers.

Methods

Eleven bonnet macaque males reared under VFD conditions and seven age-matched control subjects underwent proton magnetic resonance spectroscopy imaging during young adulthood. Voxels were placed over VS/CN to capture nucleus accumbens. Cisternal cerebrospinal fluid corticotropin-releasing factor concentrations, hippocampal volume, body mass, and response to a human intruder had been previously determined.

Results

VFD-reared monkeys exhibited significantly increased NAA/creatine concentrations in right VS/CN in comparison to normally reared controls, controlling for multiple comparisons. In comparison to controls, VFD cerebrospinal fluid corticotropin-releasing factor concentrations were directly associated with right VS/CN absolute NAA. Left hippocampal volume was inversely associated with left VS/CN NAA/creatine in VFD reared but not in controls. Disruption of a normative inverse correlation between left VS/CN NAA and body mass was noted in VFD. Only non-VFD subjects exhibited a direct relationship between timidity response to an intruder and right VS/CN NAA.

Conclusion

Early life stress produced persistent increases in VS/CN NAA, which demonstrated specific patterns of association (or lack thereof) to early life stress markers in comparison to non-VFD subjects. The data are broadly consistent with a stable nonhuman primate phenotype of anxiety and mood disorder vulnerability whereby in vivo indicators of neuronal integrity, although reduced in hippocampus, are increased in striatum. The findings may provide a catalyst for further studies in humans and other species regarding a reciprocal hippocampal/nucleus accumbens relationship in affective disorders.

Convergent Mechanisms Underlying Rapid Antidepressant Action

Traditional pharmacological treatments for depression have a delayed therapeutic onset, ranging from several weeks to months, and there is a high percentage of individuals who never respond to treatment. In contrast, ketamine produces rapid-onset antidepressant, anti-suicidal, and anti-anhedonic actions following a single administration to patients with depression. Proposed mechanisms of the antidepressant action of ketamine include N-methyl-D-aspartate receptor (NMDAR) modulation, gamma aminobutyric acid (GABA)-ergic interneuron disinhibition, and direct actions of its hydroxynorketamine (HNK) metabolites. Downstream actions include activation of the mechanistic target of rapamycin (mTOR), deactivation of glycogen synthase kinase-3 and eukaryotic elongation factor 2 (eEF2), enhanced brain-derived neurotrophic factor (BDNF) signaling, and activation of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors (AMPARs). These putative mechanisms of ketamine action are not mutually exclusive and may complement each other to induce potentiation of excitatory synapses in affective-regulating brain circuits, which results in amelioration of depression symptoms. We review these proposed mechanisms of ketamine action in the context of how such mechanisms are informing the development of novel putative rapid-acting antidepressant drugs. Such drugs that have undergone pre-clinical, and in some cases clinical, testing include the muscarinic acetylcholine receptor antagonist scopolamine, GluN2B-NMDAR antagonists (i.e., CP-101,606, MK-0657), (2R,6R)-HNK, NMDAR glycine site modulators (i.e., 4-chlorokynurenine, pro-drug of the glycineB NMDAR antagonist 7-chlorokynurenic acid), NMDAR agonists [i.e., GLYX-13 (rapastinel)], metabotropic glutamate receptor 2/3 (mGluR2/3) antagonists, GABAA receptor modulators, and drugs acting on various serotonin receptor subtypes. These ongoing studies suggest that the future acute treatment of depression will typically occur within hours, rather than months, of treatment initiation.

Diffusion MRI and MR spectroscopy reveal microstructural and metabolic brain alterations in chronic mild stress exposed rats: A CMS recovery study

Chronic mild stress (CMS) induced depression elicits several debilitating symptoms and causes a significant economic burden on society. High variability in the symptomatology of depression poses substantial impediment to accurate diagnosis and therapy outcome. CMS exposure induces significant metabolic and microstructural alterations in the hippocampus (HP), prefrontal cortex (PFC), caudate-putamen (CP) and amygdala (AM), however, recovery from these maladaptive changes are limited and this may provide negative effects on the therapeutic treatment and management of depression. The present study utilized anhedonic rats from the unpredictable CMS model of depression to study metabolic recovery in the ventral hippocampus (vHP) and microstructural recovery in the HP, AM, CP, and PFC. The study employed 1H MR spectroscopy (1H MRS) and in-vivo diffusion MRI (d-MRI) at the age of week 18 (week 1 post CMS exposure) week 20 (week 3 post CMS) and week 25 (week 8 post CMS exposure) in the anhedonic group, and at the age of week 18 and week 22 in the control group. The d-MRI data have provided an array of diffusion tensor metrics (FA, MD, AD, and RD), and fast kurtosis metrics (MKT, WL and WT). CMS exposure induced a significant metabolic alteration in vHP, and significant microstructural alterations were observed in the HP, AM, and PFC in comparison to the age match control and within the anhedonic group. A significantly high level of N-acetylaspartate (NAA) was observed in vHP at the age of week 18 in comparison to age match control and week 20 and week 25 of the anhedonic group. HP and AM showed significant microstructural alterations up to the age of week 22 in the anhedonic group. PFC showed significant microstructural alterations only at the age of week 18, however, most of the metrics showed significantly higher value at the age of week 20 in the anhedonic group. The significantly increased NAA concentration may indicate impaired catabolism due to astrogliosis or oxidative stress. The significantly increased WL in the AM and HP may indicate hypertrophy of AM and reduced volume of HP. Such metabolic and microstructural alterations could be useful in disease diagnosis and follow-up treatment intervention in depression and similar disorders.

Differential microstructural alterations in rat cerebral cortex in a model of chronic mild stress depression

Chronic mild stress leads to depression in many cases and is linked to several debilitating diseases including mental disorders. Recently, neuronal tracing techniques, stereology, and immunohistochemistry have revealed persistent and significant microstructural alterations in the hippocampus, hypothalamus, prefrontal cortex, and amygdala, which form an interconnected system known as the stress circuit. Most studies have focused only on this circuit, however, some studies indicate that manipulation of sensory and motor systems may impact genesis and therapy of mood disorders and therefore these areas should not be neglected in the study of brain microstructure alterations in response to stress and depression. For this reason, we explore the microstructural alterations in different cortical regions in a chronic mild stress model of depression. The study employs ex-vivo diffusion MRI (d-MRI) to assess cortical microstructure in stressed (anhedonic and resilient) and control animals. MRI is followed by immunohistochemistry to substantiate the d-MRI findings. We find significantly lower extracellular diffusivity in auditory cortex (AC) of stress groups and a significantly higher fractional anisotropy in the resilient group. Neurite density was not found to be significantly higher in any cortical ROIs in the stress group compared to control, although axonal density is higher in the stress groups. We also report significant thinning of motor cortex (MC) in both stress groups. This is in agreement with recent clinical and preclinical studies on depression and similar disorders where significant microstructural and metabolic alterations were found in AC and MC. Our findings provide further evidence that the AC and MC are sensitive towards stress exposure and may extend our understanding of the microstructural effects of stress beyond the stress circuit of the brain. Progress in this field may provide new avenues of research to help in diagnosis and treatment intervention for depression and related disorders.

Neural systems underlying affective disorders

Three main approaches are used to explore the neural correlates of mood disorder: neuropsychological studies, neuroimaging studies and post-mortem investigations. Lesion studies implicate disturbances in the frontal lobe, basal ganglia, striatum and anterior temporal cortex. Early neurocognitive and neuropathological investigations led to a ‘hypofrontality’ hypothesis of unipolar and bipolar depression, but functional neuroimaging has revealed a more complex picture. Thus, increased metabolism may occur in the subgenual anterior cingulate gyrus in resting-state studies of depression and sad-mood induction. Antidepressants may reduce this activity. Amygdala hyperactivation also is associated with affective disorders. Task-related studies reveal abnormal biases in memory, the experience of pleasure and the perception of emotional facial expressions. There is still little clarity whether the abnormalities in brain activation represent state or trait characteristics of affective disorders.

The Antidepressant and Cognitive Improvement Activities of the Traditional Chinese Herb Cistanche

More than ten percent of people suffer from at least one episode of depression and related mental disorders in a lifetime, and depression and related mental disorders are one of the world's greatest public health problems. A multiple system theory holds that dysregulation of the multiple systems underlies the pathogenesis of depression and related mental disorders, and new therapies based on the multiple system dysregulation theory are urgently needed. In this study, the antidepressant effect of decoction from herb Cistanche deserticola Y.C.Ma and Cistanche tubulosa was examined. Herb Cistanche decoction reduced the immobility period significantly in the mouse tail suspension test. Mice treated with herb decoction showed an improved ability of spatial learning and memory in the Morris water maze test. Groups treated herb decoction displayed a downregulated monoamine oxidase (MAO) activity; the dopamine (DA) concentration in the brain was upregulated, indicating herb Cistanche decoction improved the nerve excitability; the serum concentration of corticosterone (CORT) was downregulated, showing that mice benefited from a reduced stress level. Hence, the antidepressant efficacy and mechanism of traditional Chinese herb Cistanche were explored in this study. Herb Cistanche showed a potential to be developed as a complementary and alternative therapy for depression.

Ketamine Corrects Stress-Induced Cognitive Dysfunction through JAK2/STAT3 Signaling in the Orbitofrontal Cortex

Deficits in cognitive flexibility are prominent in stress-related psychiatric disorders, including depression. Ketamine has rapid antidepressant efficacy, but it is unknown if ketamine improves cognitive symptoms. In rats, 2 weeks chronic intermittent cold (CIC) stress impairs reversal learning, a form of cognitive flexibility mediated by the orbitofrontal cortex (OFC) that we have used previously to model cognitive dysfunction in depression. We have shown that activating JAK2/STAT3 signaling in the OFC rescued the CIC stress-induced reversal learning deficit. Thus, in the present study we determined whether ketamine also corrects the stress-induced reversal learning deficit, and if JAK2/STAT3 signaling is involved in this effect. A single injection of ketamine (10 mg/kg, i.p.) 24 h prior to testing rescued the CIC stress-induced reversal learning deficit. CIC stress decreased JAK2 phosphorylation in the OFC, and ketamine restored pJAK2 levels within 2 h post injection. The JAK2 inhibitor AG490 given systemically or into the OFC at the time of ketamine injection prevented its beneficial effect on reversal learning. We then tested the role of JAK2/STAT3 in ketamine-induced plasticity in the OFC. Ketamine depressed local field potentials evoked in the OFC by excitatory thalamic afferent stimulation, and this was prevented by JAK2 inhibition in the OFC. Further, in both the OFC and primary cortical neurons in culture, ketamine increased expression of the neural plasticity-related protein Arc, and this was prevented by JAK2 inhibition. These results suggest that the JAK2/STAT3 signaling pathway is a novel mechanism by which ketamine exerts its therapeutic effects on stress-induced cognitive dysfunction in the OFC.

Physical Activity Modulates Common Neuroplasticity Substrates in Major Depressive and Bipolar Disorder

Mood disorders (MDs) are chronic, recurrent mental diseases that affect millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility, a need remains to better understand the interrelated mechanisms that contribute to neuroplasticity deficits in MDs and the means by which various therapeutics mitigate them. Of those therapeutics being investigated, physical activity (PA) has shown clear and consistent promise. Accordingly, the aims of this review are to (1) explicate key modulators, processes, and interactions that impinge upon multiple susceptibility points to effectuate neuroplasticity deficits in MDs; (2) explore the putative mechanisms by which PA mitigates these features; (3) review protocols used to induce the positive effects of PA in MDs; and (4) highlight implications for clinicians and researchers.

Serum Brain-derived Neurotrophic Factor Levels among Euthymic Adolescents with Bipolar Disorder Type I

INTRODUCTION

Bipolar disorder (BD) has been increasingly associated with abnormalities in neuroplasticity and cellular resilience in brain regions that are involved in mood and that affect regulation. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family that regulates neuroplasticity. The aims of the current study were to compare serum BDNF levels in euthymic adolescents with BD type I with those in controls and to investigate the relationship between clinical variables and serum BDNF levels in adolescents with BD type I.

METHODS

Twenty-five adolescents diagnosed with BD type I and 17 healthy control subjects within the age range of 15-19 years were recruited. Diagnoses were made by two experienced research clinicians using the Kiddie and Young Adult Schedule for Affective Disorders and Schizophrenia Present and Lifetime Version and the affective module of Washington University in St. Louis Kiddie and Young Adult Schedule for Affective Disorders and Schizophrenia-Present State and Lifetime. Blood samples were taken during euthymia, which was defined as Young Mania Rating Scale and Hamilton Depression Rating Scale scores below 7.

RESULTS

The comparison of BDNF serum levels between the case and healthy control groups revealed no significant differences. In the case group, BDNF levels were significantly lower in patients being currently treated with lithium.

CONCLUSION

Similar to normal BDNF levels in adult patients with BD, the normal BDNF serum levels that we found in the euthymic state in adolescents and early adulthood may be related to the developmental brain stage in our study group. It may also show a common neurobiological basis of pediatric and adult BD. Further investigations evaluating BDNF levels in different mood states could help identify the role of BDNF in the underlying pathophysiology of BD.

The dysregulated brain: consequences of spatial and temporal brain complexity for bipolar disorder pathophysiology and diagnosis

Increasingly, evidence has been accumulating emphasizing the importance of looking at bipolar disorder (BD) from a neurodevelopmental and transdimensional perspective to better understand its origins and its course. In this overview article, the problems facing pathophysiological psychiatric research in BD are addressed and interpreted in the light of brain complexity. Brain complexity can be split into spatial complexity, which constitutes the physiological levels of the central nervous system (i.e., the genetic, molecular, cellular, neuronal circuit and phenomenological levels), and temporal complexity, that is, neurodevelopment. The consequences of this consideration are discussed and suggestions for clinical practice and pathophysiological psychiatric research are made.

Objective methods for the assessment of the spinal and supraspinal effects of opioids

BACKGROUND AND PURPOSE

Opioids are potent analgesics. Opioids exert effects after interaction with opioid receptors. Opioid receptors are present in the peripheral- and central nervous system (CNS), but the analgesic effects are primarily mediated via receptors in the CNS. Objective methods for assessment of opioid effects may increase knowledge on the CNS processes responsible for analgesia. The aim of this review was to provide an overview of the most common objective methods for assessment of the spinal and supraspinal effects of opioids and discuss their advantages and limitations.

METHOD

The literature search was conducted in Pub Med (http://www.ncbi.nlm.nih.gov/pubmed) from November 2014 to June 2016, using free-text terms: "opioid", "morphine" and "oxycodone" combined with the terms "pupillometry," "magnetic resonance spectroscopy," "fMRI," "BOLD," "PET," "pharmaco-EEG", "electroencephalogram", "EEG," "evoked potentials," and "nociceptive reflex". Only original articles published in English were included.

RESULTS

For assessment of opioid effects at the supraspinal level, the following methods are evaluated: pupillometry, proton magnetic resonance spectroscopy, functional resonance magnetic imaging (fMRI), positron emission tomography (PET), spontaneous electroencephalogram (EEG) and evoked potentials (EPs). Pupillometry is a non-invasive tool used in research as well as in the clinical setting. Proton magnetic resonance spectroscopy has been used for the last decades and it is a non-invasive technique for measurement of in vivo brain metabolite concentrations. fMRI has been a widely used non-invasive method to estimate brain activity, where typically from the blood oxygen level-dependent (BOLD) signal. PET is a nuclear imaging technique based on tracing radio labeled molecules injected into the blood, where receptor distribution, density and activity in the brain can be visualized. Spontaneous EEG is typically quantified in frequency bands, power spectrum and spectral edge frequency. EPs are brain responses (assessed by EEG) to a predefined number of short phasic stimuli. EPs are quantified by their peak latencies and amplitudes, power spectrum, scalp topographies and brain source localization. For assessment of opioid effects at the spinal level, the following methods are evaluated: the nociceptive withdrawal reflex (NWR) and spinal EPs. The nociceptive withdrawal reflex can be recorded from all limbs, but it is standard to record the electromyography signal at the biceps femoris muscle after stimulation of the ipsilateral sural nerve; EPs can be recorded from the spinal cord and are typically recorded after stimulation of the median nerve at the wrist.

CONCLUSION AND IMPLICATIONS

The presented methods can all be used as objective methods for assessing the centrally mediated effects of opioids. Advantages and limitations should be considered before implementation in drug development, future experimental studies as well as in clinical settings. In conclusion, pupillometry is a sensitive measurement of opioid receptor activation in the CNS and from a practical and economical perspective it may be used as a biomarker for opioid effects in the CNS. However, if more detailed information is needed on opioid effects at different levels of the CNS, then EEG, fMRI, PET and NWR have the potential to be used. Finally, it is conceivable that information from different methods should be considered together for complementary information.

Inflammatory cytokines influence measures of white matter integrity in Bipolar Disorder

BACKGROUND

Bipolar Disorder (BD) is associated with elevated biomarkers of cell-mediated immune activation and inflammation and with signs of widespread disruption of white matter (WM) integrity in adult life. Consistent findings in animal models link WM damage in inflammatory diseases of the brain and serum levels of cytokines.

METHODS

With an exploratory approach, we tested the effects of 22 serum analytes, including pro- and anti-inflammatory cytokines and neurotrophic/hematopoietic factors, on DTI measures of WM microstructure in a sample of 31 patients with a major depressive episode in course of BD. We used whole brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial (AD), radial (RD), and mean diffusivity (MD), and fractional anisotropy (FA).

RESULTS

The inflammation-related cytokines TNF-α, IL-8, IFN-γ and IL-10, and the growth factors IGFBP2 and PDGF-BB, shared the same significant associations with lower FA, and higher MD and RD, in large overlapping networks of WM fibers mostly located in the anterior part of the brain and including corpus callosum, cingulum, superior and inferior longitudinal fasciculi, inferior fronto-occipital fasciculi, uncinate, forceps, corona radiata, thalamic radiation, internal capsule.

CONCLUSIONS

Higher RD is thought to signify increased space between fibers, suggesting demyelination or dysmyelination. The pattern of higher RD and MD with lower FA suggests that inflammation-related cytokine and growth factor levels inversely associate with integrity of myelin sheaths. The activated inflammatory response system might contribute to BD pathophysiology by hampering structural connectivity in critical cortico-limbic networks.

The burden of HIV-associated neurocognitive disorder (HAND) in the Asia-Pacific region and recommendations for screening

BACKGROUND

HIV-associated neurocognitive disorder incurs a significant burden on HIV patients in Asia-Pacific countries; however, the incidence is difficult to estimate due to a lack of local epidemiological data. The impact of neurocognitive impairment in HIV patients is often underestimated due to a lack of education and awareness, and there are consequently gaps in the provision of screening and diagnosis to enable earlier intervention to limit neurocognitive impairment.

METHOD

This review seeks to redress the imbalance by promoting awareness and education among physicians concerning the neurovirulence of HIV and thereby increase screening efforts to improve diagnosis rates and clinical outcomes for underserved patients in this region. The Asia, Australia, and Middle East (AAME) HAND Advisory Board convened expert regional representatives to review current practice and recommend appropriate measures related to the implementation of standardised screening programmes and treatment recommendations to curb the developing HAND epidemic in the region. In particular, we recommend basic neuropsychological testing protocols that could be efficiently introduced into clinical practice for routine screening.

RESULT

We also propose simple guidelines for the management of HAND. We believe that HAND is a significant and under-reported diagnosis in HIV patients that warrants both greater recognition and further clinical investigation of the underlying pathophysiology and the impact of HIV disease progression, with HAND being associated with worse medication adherence and therefore possibly increased risk of ARV treatment failure.

DISCUSSION

Widespread screening will lead to greater recognition of HAND and earlier intervention, which may lead to improved management strategies in the future.

Biophysical modeling of high field diffusion MRI demonstrates micro-structural aberration in chronic mild stress rat brain

Depression is one of the leading causes of disability worldwide. Immense heterogeneity in symptoms of depression causes difficulty in diagnosis, and to date, there are no established biomarkers or imaging methods to examine depression. Unpredictable chronic mild stress (CMS) induced anhedonia is considered to be a realistic model of depression in studies of animal subjects. Stereological and neuronal tracing techniques have demonstrated persistent remodeling of microstructure in hippocampus, prefrontal cortex and amygdala of CMS brains. Recent developments in diffusion MRI (d-MRI) analyses, such as neurite density and diffusion kurtosis imaging (DKI), are able to capture microstructural changes and are considered to be robust tools in preclinical and clinical imaging. The present study utilized d-MRI analyzed with a neurite density model and the DKI framework to investigate microstructure in the hippocampus, prefrontal cortex, caudate putamen and amygdala regions of CMS rat brains by comparison to brains from normal controls. To validate findings of CMS induced microstructural alteration, histology was performed to determine neurite, nuclear and astrocyte density. d-MRI based neurite density and tensor-based mean kurtosis (MKT) were significantly higher, while mean diffusivity (MD), extracellular diffusivity (Deff) and intra-neurite diffusivity(D_L) were significantly lower in the amygdala of CMS rat brains. Deff was also significantly lower in the hippocampus and caudate putamen in stressed groups. Histological neurite density corroborated the d-MRI findings in the amygdala and reductions in nuclear and astrocyte density further buttressed the d-MRI results. The present study demonstrated that the d-MRI based neurite density and MKT can reveal specific microstructural changes in CMS rat brains and these parameters might have value in clinical diagnosis of depression and for evaluation of treatment efficacy.