Electroconvulsive seizures increase hippocampal neurogenesis after chronic corticosterone treatment

Shared effects of electroconvulsive shocks and ketamine on neuroplasticity: A systematic review of animal models of depression

Electroconvulsive shocks (ECS) and ketamine are antidepressant treatments with a relatively fast onset of therapeutic effects compared to conventional medication and psychotherapy. While the exact neurobiological mechanisms underlying the antidepressant response of ECS and ketamine are unknown, both interventions are associated with neuroplasticity. Restoration of neuroplasticity may be a shared mechanism underlying the antidepressant efficacy of these interventions. In this systematic review, literature of animal models of depression is summarized to examine the possible role of neuroplasticity in ECS and ketamine on a molecular, neuronal, synaptic and functional level, and specifically to what extent these mechanisms are shared between both interventions. The results highlight that hippocampal neurogenesis and brain-derived neurotrophic factor (BDNF) levels are consistently increased after ECS and ketamine. Moreover, both interventions positively affect glutamatergic neurotransmission, astrocyte and neuronal morphology, synaptic density, vasculature and functional plasticity. However, a small number of studies investigated these processes after ECS. Understanding the shared fundamental mechanisms of fast-acting antidepressants can contribute to the development of novel therapeutic approaches for patients with severe depression.

Use of ECT in Autism Spectrum Disorder and/or Intellectual Disability: A Single Site Retrospective Analysis

Autism spectrum disorder (ASD) and intellectual disability (ID) are heterogenous and prevalent conditions which may occur in isolation or as a co-morbidity. Psychiatric co-morbidity is common with limited treatment options. Preliminary research into electroconvulsive therapy (ECT) for these conditions has been encouraging. Thus, further research in this patient population is warranted. We conducted a 10-year retrospective review of the electronic medical record and identified intellectually capable individuals with ASD (IC-ASD), and those with ASD+ID or ID who received at least three ECT treatments. 32 patients were identified of which 30 (94%) experienced positive clinical response, defined as a clinical global impression-improvement (CGI-I) score of 3 or less. The average retrospective CGI-I score across all groups was 1.97, and results of a t-test performed on CGI-I scores indicated improvement across all groups [t = - 16.54, df = 31, p < 0.001, 95% CI = (1.72, 2.22)]. No significant adverse events were identified based on clinical documentation. Our findings further support previous ECT research in this patient population.

Molecular basis underlying changes of brain entropy and functional connectivity in major depressive disorders after electroconvulsive therapy

INTRODUCTION

Electroconvulsive therapy (ECT) is widely used for treatment-resistant depression. However, it is unclear whether/how ECT can be targeted to affect brain regions and circuits in the brain to dynamically regulate mood and cognition.

METHODS

This study used brain entropy (BEN) to measure the irregular levels of brain systems in 46 major depressive disorder (MDD) patients before and after ECT treatment. Functional connectivity (FC) was further adopted to reveal changes of functional couplings. Moreover, transcriptomic and neurotransmitter receptor data were used to reveal genetic and molecular basis of the changes of BEN and functional connectivities.

RESULTS

Compared to pretreatment, the BEN in the posterior cerebellar lobe (PCL) significantly decreased and FC between the PCL and the right temporal pole (TP) significantly increased in MDD patients after treatment. Moreover, we found that these changes of BEN and FC were closely associated with genes' expression profiles involved in MAPK signaling pathway, GABAergic synapse, and dopaminergic synapse and were significantly correlated with the receptor/transporter density of 5-HT, norepinephrine, glutamate, etc. CONCLUSION: These findings suggest that loops in the cerebellum and TP are crucial for ECT regulation of mood and cognition, which provides new evidence for the antidepressant effects of ECT and the potential molecular mechanism leading to cognitive impairment.

Identification of the antidepressant effect of electroconvulsive stimulation-related genes in hippocampal astrocyte

Major depressive disorder (MDD) remains a significant global health concern, with limited and slow efficacy of existing antidepressants. Electroconvulsive therapy (ECT) has superior and immediate efficacy for MDD, but its action mechanism remains elusive. Therefore, the elucidation of the action mechanism of ECT is expected to lead to the development of novel antidepressants with superior and immediate efficacy. Recent studies suggest a potential role of hippocampal astrocyte in MDD and ECT. Hence, we investigated antidepressant effect of electroconvulsive stimulation (ECS), an animal model of ECT, -related genes in hippocampal astrocyte with a mouse model of MDD, in which corticosterone (CORT)-induced depression-like behaviors were recovered by ECS. In this model, both of CORT-induced depression-like behaviors and the reduction of hippocampal astrocyte were recovered by ECS. Following it, astrocytes were isolated from the hippocampus of this model and RNA-seq was performed with these isolated astrocytes. Interestingly, gene expression patterns altered by CORT were reversed by ECS. Additionally, cell proliferation-related signaling pathways were inhibited by CORT and recovered by ECS. Finally, serum and glucocorticoid kinase-1 (SGK1), a multi-functional protein kinase, was identified as a candidate gene reciprocally regulated by CORT and ECS in hippocampal astrocyte. Our findings suggest a potential role of SGK1 in the antidepressant effect of ECS via the regulation of the proliferation of astrocyte and provide new insights into the involvement of hippocampal astrocyte in MDD and ECT. Targeting SGK1 may offer a novel approach to the development of new antidepressants which can replicate superior and immediate efficacy of ECT.

Altered in vivo early neurogenesis traits in patients with depression: Evidence from neuron-derived extracellular vesicles and electroconvulsive therapy

BACKGROUND

The neurogenesis hypothesis is a promising candidate etiologic hypothesis for depression, and it is associated with electroconvulsive therapy (ECT). However, human in vivo molecular-level evidence is lacking.

OBJECTIVE

We used neuron-derived extracellular vesicles (NDEVs) as a "window to the neurons" to explore the in vivo neurogenesis status associated with ECT in patients with treatment-resistant depression (TRD).

METHODS

In this study, we enrolled 40 patients with TRD and 35 healthy controls (HCs). We isolated NDEVs from the plasma of each participant to test the levels of doublecortin (DCX), a marker of neurogenesis, and cluster of differentiation (CD) 81, a marker of EVs. We also assessed the plasma levels of brain-derived neurotrophic factor (BDNF), a protein that is known to be associated with ECT and neuroplastic processes.

RESULTS

Our findings indicated that both the levels of DCX in NDEVs and BDNF in plasma were significantly lower in TRD patients compared to HCs at baseline, but increased following ECTs. Conversely, levels of CD81 in NDEVs were found higher in TRD patients at baseline, but did not change after the ECT treatments. Exploratory analyses revealed that lower levels of BDNF in plasma and DCX in NDEVs, along with higher CD81 levels in NDEVs, were associated with more severe depressive symptoms and reduced cognitive function at baseline. Furthermore, higher baseline CD81 concentrations in NDEVs were correlated with greater decreases in depression symptoms.

CONCLUSIONS

We first present human in vivo evidence of early neurogenesis using DCX through NDEVs: decreased in TRD patients, increased after ECTs.

Reviewing the neurobiology of electroconvulsive therapy on a micro- meso- and macro-level

BACKGROUND

Electroconvulsive therapy (ECT) remains the one of the most effective of biological antidepressant interventions. However, the exact neurobiological mechanisms underlying the efficacy of ECT remain unclear. A gap in the literature is the lack of multimodal research that attempts to integrate findings at different biological levels of analysis METHODS: We searched the PubMed database for relevant studies. We review biological studies of ECT in depression on a micro- (molecular), meso- (structural) and macro- (network) level.

RESULTS

ECT impacts both peripheral and central inflammatory processes, triggers neuroplastic mechanisms and modulates large scale neural network connectivity.

CONCLUSIONS

Integrating this vast body of existing evidence, we are tempted to speculate that ECT may have neuroplastic effects resulting in the modulation of connectivity between and among specific large-scale networks that are altered in depression. These effects could be mediated by the immunomodulatory properties of the treatment. A better understanding of the complex interactions between the micro-, meso- and macro- level might further specify the mechanisms of action of ECT.

Electroconvulsive shock increases neurotrophy and neurogenesis: Time course and treatment session effects

Increasing evidence suggests that hippocampal neurotrophy may be related to the development of major depressive disorders. Neurogenesis, which can be regulated by neurotrophic factors, is also involved in antidepressant efficacy. This paper reviewed literature on neurotrophic signaling and cell proliferation after electroconvulsive shock (ECS) treatment. All articles were from PubMed, Web of Science, and Scopus databases between 2000 and 2020. The keywords used in the literature search are: "ECS," "ECT," "electroconvulsive seizure," "electroconvulsive shock," "electroconvulsive therapy," "neurotrophic factor," "nerve growth factor," "neurotrophins," "neurogenesis," and "cell proliferation." Eighty-two articles were included in the final analysis. It was shown that compared with acute ECS, repeated ECS increased neurotrophin expression in more brain regions at higher levels and was maintained for a longer time. Similarly, ECS increased cell proliferation in a dose- and time-dependent manner. The increase in cell proliferation was positively correlated with the amount of ECS administered and the newly born cells survived for a long time. The effects of ECS in inducing increases in neurotrophin levels and neurogenesis may contribute to brain function changes and antidepressant effects. Future research may focus on optimal sessions of ECT treatment to obtain the best therapeutic effect.

Microvascular changes associated with epilepsy: A narrative review

The blood-brain barrier (BBB) is dysfunctional in temporal lobe epilepsy (TLE). In this regard, microvascular changes are likely present. The aim of this review is to provide an overview of the current knowledge on microvascular changes in epilepsy, and includes clinical and preclinical evidence of seizure induced angiogenesis, barriergenesis and microcirculatory alterations. Anatomical studies show increased microvascular density in the hippocampus, amygdala, and neocortex accompanied by BBB leakage in various rodent epilepsy models. In human TLE, a decrease in afferent vessels, morphologically abnormal vessels, and an increase in endothelial basement membranes have been observed. Both clinical and experimental evidence suggests that basement membrane changes, such as string vessels and protrusions, indicate and visualize a misbalance between endothelial cell proliferation and barriergenesis. Vascular endothelial growth factor (VEGF) appears to play a crucial role. Following an altered vascular anatomy, its physiological functioning is affected as expressed by neurovascular decoupling that subsequently leads to hypoperfusion, disrupted parenchymal homeostasis and potentially to seizures". Thus, epilepsy might be a condition characterized by disturbed cerebral microvasculature in which VEGF plays a pivotal role. Additional physiological data from patients is however required to validate findings from models and histological studies on patient biopsies.

Electroconvulsive Shock, but Not Transcranial Magnetic Stimulation, Transiently Elevates Cell Proliferation in the Adult Mouse Hippocampus

Hippocampal plasticity is hypothesized to play a role in the etiopathogenesis of depression and the antidepressant effect of medications. One form of plasticity that is unique to the hippocampus and is involved in depression-related behaviors in animal models is adult neurogenesis. While chronic electroconvulsive shock (ECS) strongly promotes neurogenesis, less is known about its acute effects and little is known about the neurogenic effects of other forms of stimulation therapy, such as repetitive transcranial magnetic stimulation (rTMS). Here, we investigated the time course of acute ECS and rTMS effects on markers of cell proliferation and neurogenesis in the adult hippocampus. Mice were subjected to a single session of ECS, 10 Hz rTMS (10-rTMS), or intermittent theta burst stimulation (iTBS). Mice in both TMS groups were injected with BrdU 2 days before stimulation to label immature cells. One, 3, or 7 days later, hippocampi were collected and immunostained for BrdU + cells, actively proliferating PCNA + cells, and immature DCX + neurons. Following ECS, mice displayed a transient increase in cell proliferation at 3 days post-stimulation. At 7 days post-stimulation there was an elevation in the number of proliferating neuronal precursor cells (PCNA + DCX +), specifically in the ventral hippocampus. iTBS and rTMS did not alter the number of BrdU + cells, proliferating cells, or immature neurons at any of the post-stimulation time points. Our results suggest that neurostimulation treatments exert different effects on hippocampal neurogenesis, where ECS may have greater neurogenic potential than iTBS and 10-rTMS.

Altered acoustic startle, prepulse facilitation, and object recognition memory produced by corticosterone withdrawal in male rats

The symptoms of human depression often include cognitive deficits. However, cognition is not frequently included in the behavioral assessments conducted in preclinical models of depression. For example, it is well known that repeated corticosterone (CORT) injections in rodents produce depression-like behavior as measured by the forced swim test, sucrose preference test, and tail suspension test, but the cognitive impairments produced by repeated CORT have not been thoroughly examined. The purpose of this experiment was to assess the effect of repeated CORT injections on several versions of object recognition memory and modulation of the acoustic startle response by relatively low intensity prepulses, along with the more traditional assessment of depression-like behavior using the forced swim test. Rats received 21 days of CORT (40 mg/kg) or vehicle injections followed by a battery of behavioral tests. Importantly, during behavioral testing CORT treatment did not occur (CORT withdrawal). Corticosterone decreased body weight, increased immobility in the forced swim test, lowered startle amplitudes, and facilitated responding to trials with a short interval (30 ms) between the prepulse and pulse. Corticosterone also impaired both object location and object-in-place recognition memory, while sparing performance on object recognition memory. Collectively, our data suggest that CORT produces selective disruptions in prepulse facilitation, object location, and object-in-place recognition memory, and that these impairments should be considered as part of the phenotype produced by repeated CORT, and perhaps chronic stress.

Volume of hippocampal subregions and clinical improvement following electroconvulsive therapy in patients with depression

It is thought that the hippocampal neurogenesis is an important mediator of the antidepressant effect of electroconvulsive therapy (ECT). However, most previous studies failed to demonstrate the relationship between the increase in the hippocampal volume and the antidepressant effect. We reinvestigated this relationship by looking at distinct hippocampal subregions and applying repeated measures correlation. Using a 3 Tesla MRI-scanner, we scanned 22 severely depressed in-patients at three time points: before the ECT series, after the series, and at six-month follow-up. The depression severity was assessed by the 17-item Hamilton Rating Scale for Depression (HAMD-17). The hippocampus was segmented into subregions using Freesurfer software. The dentate gyrus (DG) was the primary region of interest (ROI), due to the role of this region in neurogenesis. The other major hippocampal subregions were the secondary ROIs (n = 20). The general linear mixed model and the repeated measures correlation were used for statistical analyses. Immediately after the ECT series, a significant volume increase was present in the right DG (Cohen's d = 1.7) and the left DG (Cohen's d = 1.5), as well as 15 out of 20 secondary ROIs. The clinical improvement, i.e., the decrease in HAMD-17 score, was correlated to the increase in the right DG volume (r_rm = -0.77, df = 20, p < .001), and the left DG volume (r_rm = -0.75, df = 20, p < .001). Similar correlations were observed in 14 out of 20 secondary ROIs. Thus, ECT induces an increase not only in the volume of the DG, but also in the volume of other major hippocampal subregions. The volumetric increases may reflect a neurobiological process that may be related to the ECT's antidepressant effect. Further investigation of the relationship between hippocampal subregions and the antidepressant effect is warranted. A statistical approach taking the repeated measurements into account should be preferred in the analyses.

Inflammation, Hippocampal Volume, and Therapeutic Outcome following Electroconvulsive Therapy in Depressive Patients: A Pilot Study

INTRODUCTION

Electroconvulsive therapy (ECT) influences the concentration of peripheral inflammatory markers, such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). In which way this immune effect contributes to the impact of ECT on the central nervous system in depression remains unknown.

OBJECTIVE

The aim of this study was to examine whether the hippocampal volumetric increase in depressed patients treated with ECT is related to changes in peripheral IL-6 and TNF-α levels.

METHODS

IL-6 and TNF-α plasma levels were measured in 62 patients 1 week before and after an acute course of ECT. Hippocampal volumes were analyzed in a magnetic resonance imaging (MRI) subsample of 13 patients at the same time points.

RESULTS

A significant decrease in IL-6 levels was observed in the total sample and a significant increase in hippocampal volume in the MRI subsample. The reduction of peripheral IL-6 correlated with an increase in total hippocampal volume. A more limited decrease of TNF-α correlated with a more limited increase of both the total and left hippocampus volumes.

CONCLUSION

This pilot study is the first to highlight the link between peripheral immune changes and hippocampal volume increase following ECT. Further research is required to conclude whether ECT indeed exerts its central effect on the brain via changes of peripheral inflammatory markers.

Glucocorticoid-mediated mechanisms of hippocampal damage: Contribution of subgranular neurogenesis

A comprehensive overview of the interplay between glucocorticoids (GCs) and adult hippocampal neurogenesis (AHN) is presented, particularly, in the context of a diseased brain. The effectors of GCs in the dentate gyrus neurogenic niche of the hippocampal are reviewed, and the consequences of the GC signaling on the generation and integration of new neurons are discussed. Recent findings demonstrating how GC signaling mediates impairments of the AHN in various brain pathologies are overviewed. GC-mediated effects on the generation and integration of adult-born neurons in the hippocampal dentate gyrus depend on the nature, severity, and duration of the acting stress factor. GCs realize their effects on the AHN primarily via specific glucocorticoid and mineralocorticoid receptors. Disruption of the reciprocal regulation between the hypothalamic-pituitary-adrenal (HPA) axis and the generation of the adult-born granular neurons is currently considered to be a key mechanism implicating the AHN into the pathogenesis of numerous brain diseases, including those without a direct hippocampal damage. These alterations vary from reduced proliferation of stem and progenitor cells to increased cell death and abnormalities in morphology, connectivity, and localization of young neurons. Although the involvement of the mutual regulation between the HPA axis and the AHN in the pathogenesis of cognitive deficits and mood impairments is evident, several unresolved critical issues are stated. Understanding the details of GC-mediated mechanisms involved in the alterations in AHN could enable the identification of molecular targets for ameliorating pathology-induced imbalance in the HPA axis/AHN mutual regulation to conquer cognitive and psychiatric disturbances.

Effects of electroconvulsive shock on neuro-immune responses: Does neuro-damage occur?

Electroconvulsive therapy (ECT) is one of the most effective treatments for treatment-resistant depression. However, this treatment may produce memory impairment. The mechanisms of the cognitive adverse effects are not known. Neuroimmune response is related to the cognitive deficits. By reviewing the available animal literature, we examined the glia activation, inflammatory cytokines, neuron oxidative stress responses, and neural morphological changes following electroconvulsive shock (ECS) treatment. The studies showed that ECS activates microglia, upregulates neuro-inflammatory cytokines, and increases oxidative stress responses. But these effects are rapid and may be transient. They normalize as ECS treatment continues, suggesting endogenous neuroprotection may be mobilized. The transient changes are well in line with the clinical observations that ECT usually does not cause significant long-lasting retrograde amnesia. The longitudinal studies will be particularly important to explore the dynamic changes of neuroplasticity following ECT (Jonckheere et al., 2018). Investigating the neuroplasticity changes in animals that suffered chronic stress may also be crucial to giving support to the translation of preclinical research.

Glucocorticoids as Mediators of Adverse Outcomes of Prenatal Stress

A number of prenatal experiences are associated with adverse outcomes after birth, ranging from cardiovascular problems to psychiatric disease. Prenatal stress is associated with neurodevelopmental alterations that persist after birth and manifest at the behavioral level, for example, increased fearfulness, and at the physiological one, that is, brain structural and functional changes. Understanding the mechanisms that drive these lasting effects may help in preventing long-term negative outcomes of prenatal stress. Elevated glucocorticoid signaling in utero may be one of the key mediators of prenatal stress effects on the offspring. In this review, we summarize how prenatal glucocorticoids may impact the activity of the fetal hypothalamic-pituitary-adrenal (HPA) axis, disrupt neurodevelopmental processes and alter the epigenetic landscape of the fetus. We also discuss the need to take into consideration the interaction of these processes with the offspring's genetic landscape.

Structural changes in amygdala nuclei, hippocampal subfields and cortical thickness following electroconvulsive therapy in treatment-resistant depression: longitudinal analysis

BACKGROUND

Electroconvulsive therapy (ECT) is the treatment of choice for severe mental illness including treatment-resistant depression (TRD). Increases in volume of the hippocampus and amygdala following ECT have consistently been reported.AimsTo investigate neuroplastic changes after ECT in specific hippocampal subfields and amygdala nuclei using high-resolution structural magnetic resonance imaging (MRI) (trial registration: clinicaltrials.gov - NCT02379767).

METHOD

MRI scans were carried out in 14 patients (11 women, 46.9 years (s.d. = 8.1)) with unipolar TRD twice before and once after a series of right unilateral ECT in a pre-post study design. Volumes of subcortical structures, including subfields of the hippocampus and amygdala, and cortical thickness were extracted using FreeSurfer. The effect of ECT was tested using repeated-measures ANOVA. Correlations of imaging and clinical parameters were explored.

RESULTS

Increases in volume of the right hippocampus by 139.4 mm3 (s.d. = 34.9), right amygdala by 82.3 mm3 (s.d. = 43.9) and right putamen by 73.9 mm3 (s.d. = 77.0) were observed. These changes were localised in the basal and lateral nuclei, and the corticoamygdaloid transition area of the amygdala, the hippocampal-amygdaloid transition area and the granule cell and molecular layer of the dentate gyrus. Cortical thickness increased in the temporal, parietal and insular cortices of the right hemisphere.

CONCLUSIONS

Following ECT structural changes were observed in hippocampal subfields and amygdala nuclei that are specifically implicated in the pathophysiology of depression and stress-related disorders and retain a high potential for neuroplasticity in adulthood.Declaration of interestS.K. has received grants/research support, consulting fees and/or honoraria within the past 3 years from Angelini, AOP Orphan Pharmaceuticals AG, AstraZeneca, Celegne GmbH, Eli Lilly, Janssen-Cilag Pharma GmbH, KRKA-Pharma, Lundbeck A/S, Neuraxpharm, Pfizer, Pierre Fabre, Schwabe and Servier. R.L. received travel grants and/or conference speaker honoraria from Shire, AstraZeneca, Lundbeck A/S, Dr. Willmar Schwabe GmbH, Orphan Pharmaceuticals AG, Janssen-Cilag Pharma GmbH, and Roche Austria GmbH.

Electroconvulsive Therapy Induces Cortical Morphological Alterations in Major Depressive Disorder Revealed with Surface-Based Morphometry Analysis

Although electroconvulsive therapy (ECT) is one of the most effective treatments for major depressive disorder (MDD), the mechanism underlying the therapeutic efficacy and side effects of ECT remains poorly understood. Here, we investigated alterations in the cortical morphological measurements including cortical thickness (CT), surface area (SA), and local gyrification index (LGI) in 23 MDD patients before and after ECT. Furthermore, multivariate pattern analysis using linear support vector machine (SVM) was applied to investigate whether the changed morphological measurements can be effective indicators for therapeutic efficacy of ECT. Surface-based morphometry (SBM) analysis found significantly increased vertex-wise and regional cortical thickness (CT) and surface area (SA) in widespread regions, mainly located in the left insula (INS) and left fusiform gyrus, as well as hypergyrification in the left middle temporal gyrus (MTG) in MDD patients after ECT. Partial correlational analyses identified associations between the morphological properties and depressive symptom scores and impaired memory scores. Moreover, SVM result showed that the changed morphological measurements were effective to classify the MDD patients before and after ECT. Our findings suggested that ECT may enhance cortical neuroplasticity to facilitate neurogenesis to remit depressive symptoms and to impair delayed memory. These findings indicated that the cortical morphometry is a good index for therapeutic efficacy of ECT.

Electroconvulsive therapy selectively enhanced feedforward connectivity from fusiform face area to amygdala in major depressive disorder

Electroconvulsive therapy (ECT) has been widely used to treat the major depressive disorder (MDD), especially for treatment-resistant depression. However, the neuroanatomical basis of ECT remains an open problem. In our study, we combined the voxel-based morphology (VBM), resting-state functional connectivity (RSFC) and granger causality analysis (GCA) to identify the longitudinal changes of structure and function in 23 MDD patients before and after ECT. In addition, multivariate pattern analysis using linear support vector machine (SVM) was applied to classify 23 depressed patients from 25 gender, age and education matched healthy controls. VBM analysis revealed the increased gray matter volume of left superficial amygdala after ECT. The following RSFC and GCA analyses further identified the enhanced functional connectivity between left amygdala and left fusiform face area (FFA) and effective connectivity from FFA to amygdala after ECT, respectively. Moreover, SVM-based classification achieved an accuracy of 83.33%, a sensitivity of 82.61% and a specificity of 84% by leave-one-out cross-validation. Our findings indicated that ECT may facilitate the neurogenesis of amygdala and selectively enhance the feedforward cortical-subcortical connectivity from FFA to amygdala. This study may shed new light on the pathological mechanism of MDD and may provide the neuroanatomical basis for ECT.

Single Administration of HBK-15-a Triple 5-HT1A, 5-HT7, and 5-HT3 Receptor Antagonist-Reverses Depressive-Like Behaviors in Mouse Model of Depression Induced by Corticosterone

Studies suggest that the blockade of 5-HT1A, 5-HT7, and 5-HT3 receptor may increase the speed of antidepressant response. 1-[(2,6-Dimethylphenoxy)ethoxyethyl]-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-14) and 1-[(2-chloro-6-methylphenoxy)ethoxyethyl]-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-15), dual 5-HT1A and 5-HT7 antagonists, showed significant antidepressant- and anxiolytic-like properties in our previous tests in rodents. In this study, we aimed to investigate their antidepressant potential using mouse model of corticosterone-induced depression. We chose sucrose preference test, forced swim test, and elevated plus maze to determine anhedonic-, antidepressant-, and anxiolytic-like activities. We also evaluated the influence of the active compound on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) levels in the hippocampus. Moreover, for both compounds, we performed biofunctional (5-HT3 receptor) and pharmacokinetic studies. We found that HBK-14 and HBK-15 were potent 5-HT3 receptor antagonists. HBK-14 (2.5 mg/kg) and HBK-15 (1.25 mg/kg) after intravenous (i.v.) and intraperitoneal (i.p.) administration permeated the blood-brain barrier with brain/plasma ratio lower than 1. The bioavailability of studied compounds after i.p. administration was 15% for HBK-14 and 54% for HBK-15. Chronic administration of HBK-15 (1.25 mg/kg) and fluoxetine (10 mg/kg) protected corticosterone-treated mice from anhedonic-, depressive-, and anxiety-like behaviors, as well as decreases in BDNF and NGF levels in the hippocampus. HBK-14 (2.5 mg/kg) counteracted anxiety-like behaviors in corticosterone-treated mice. Single administration of HBK-15 (1.25 mg/kg) and ketamine (1 mg/kg) reversed depression-like behavior and regulated decreased BDNF level in the hippocampus in corticosterone-treated mice. Our results suggest that simultaneous blockade of serotonergic 5-HT1A, 5-HT7, and 5-HT3 receptors might accelerate antidepressant response.

Predicting individual responses to the electroconvulsive therapy with hippocampal subfield volumes in major depression disorder

Electroconvulsive therapy (ECT) is one of the most effective treatments for major depression disorder (MDD). ECT can induce neurogenesis and synaptogenesis in hippocampus, which contains distinct subfields, e.g., the cornu ammonis (CA) subfields, a granule cell layer (GCL), a molecular layer (ML), and the subiculum. It is unclear which subfields are affected by ECT and whether we predict the future treatment response to ECT by using volumetric information of hippocampal subfields at baseline? In this study, 24 patients with severe MDD received the ECT and their structural brain images were acquired with magnetic resonance imaging before and after ECT. A state-of-the-art hippocampal segmentation algorithm from Freesurfer 6.0 was used. We found that ECT induced volume increases in CA subfields, GCL, ML and subiculum. We applied a machine learning algorithm to the hippocampal subfield volumes at baseline and were able to predict the change in depressive symptoms (r = 0.81; within remitters, r = 0.93). Receiver operating characteristic analysis also showed robust prediction of remission with an area under the curve of 0.90. Our findings provide evidence for particular hippocampal subfields having specific roles in the response to ECT. We also provide an analytic approach for generating predictions about clinical outcomes for ECT in MDD.

Voluntary Wheel Running Reverses the Decrease in Subventricular Zone Neurogenesis Caused by Corticosterone

Adult neurogenesis within the dentate gyrus (DG) of the hippocampus can be increased by voluntary exercise but is suppressed under stress, such as with corticosterone (CORT). However, the effects of exercise and CORT on the cell proliferation of the other traditional neurogenic site, the subventricular zone (SVZ), have been reported with controversial results. In addition, the cotreatment effects of voluntary exercise and CORT have not been investigated. This study aims to determine whether CORT can suppress cell proliferation in the SVZ and whether this can be reversed by voluntary exercise. In the present study, the effect of chronic (4 weeks) CORT treatment and wheel running simultaneously on the SVZ cell proliferation of adult Sprague-Dawley rats was examined. The results showed that cell proliferation indicated by bromodeoxyuridine (BrdU) was increased by voluntary wheel running, whereas it was decreased by CORT treatment within the SVZ of the rats without running. For the rats with both CORT treatment and wheel running, it was found that the number of BrdU-labeled cells was approximately at the same level as the vehicle control group. Furthermore, these proliferating cells expressed doublecortin (DCX), a migrating neuroblast marker. Wheel running increased the percentage of BrdU-labeled cells expressing DCX in the SVZ, whereas CORT treatment decreased this percentage. Thus, chronic injection of CORT can decrease the number of proliferating cells, while wheel running can reverse the decrease in cell proliferation within the SVZ to normal levels. In addition, CORT can suppress the cell differentiation within the SVZ, and this was alleviated by wheel running as indicated by the double labeling of BrdU and DCX.

Nicotine alleviates chronic stress-induced anxiety and depressive-like behavior and hippocampal neuropathology via regulating autophagy signaling

Recently, we reported that chronic nicotine significantly improved chronic stress-induced impairments of cognition and the hippocampal synaptic plasticity in mice, however, the underlying mechanism still needs to be explored. In the present study, 32 male C57BL/6 mice were divided into four groups: control (CON), stress (CUS), stress with chronic nicotine administration (CUS + Nic) and chronic nicotine administration (Nic). The anxiety-like behavior and neuropathological alteration of DG neurons were examined. Moreover, PC12 cells were examined with corticosterone in the presence or absence of nicotine. Both cell viability and apoptosis were determined. When treated simultaneously with an unpredictable chronic mild stress (CUS), nicotine (0.2 mg/kg/d) attenuated behavioral deficits and neuropathological alterations of DG neurons. Moreover, Western blotting showed that chronic nicotine also elevated the level of autophagy makers including Beclin-1 and LC3 II triggered by CUS. In addition, concomitant treatment with nicotine (10 μM) significantly attenuated the loss of PC12 cell viability (p < .01) and apoptosis compared to that of corticosterone treatment alone. Besides, chronic nicotine also enhanced the protein and RNA expression levels of autophagy makers triggered by corticosterone, such as Beclin-1, LC3 II and p62/SQSTM1. However, the above improvements were significantly blocked by autophagy inhibitor 3-MA. Importantly, the activation of the PI3K/Akt/mTOR signaling was carefully tested to illuminate the effects of chronic nicotine. Consequently, chronic nicotine played a role of neuroprotection in either CUS mice or corticosterone cells associating with the enhancement of the autophagy signaling, which was involved in activating the PI3K/Akt/mTOR signaling.

Chronic corticosterone administration reduces dendritic complexity in mature, but not young granule cells in the rat dentate gyrus

Background: Our previous work has shown that exposure to the stress hormone corticosterone (40 mg/kg CORT) for two weeks induces dendritic atrophy of pyramidal neurons in the hippocampal CA3 region and behavioral deficits. However, it is unclear whether this treatment also affects the dentate gyrus (DG), a subregion of the hippocampus comprising a heterogeneous population of young and mature neurons.

Objective: We examined the effect of CORT treatment on the dendritic complexity of mature and young granule cells in the DG.

Methods: We utilized a Golgi staining method to investigate the dendritic morphology and spine density of young neurons in the inner granular cell layer (GCL) and mature neurons in the outer GCL in response to CORT application. The expressions of glucocorticoid receptors during neuronal maturation were examined using Western blot analysis in a primary hippocampal neuronal culture.

Results: Sholl analysis revealed that CORT treatment decreased the number of intersections and shortened the dendritic length in mature, but not young, granule cells. However, the spine density of mature and young neurons was not affected. Western blot analysis showed a progressive increase in the protein levels of glucocorticoid receptors (GRs) in the cultured primary hippocampal neurons during neuronal maturation.

Conclusion: These data suggest that mature neurons are likely more vulnerable to chronic exposure to CORT; this may be due to their higher expression of GRs when compared to younger DG neurons.

How Electroconvulsive Therapy Works?: Understanding the Neurobiological Mechanisms

Electroconvulsive therapy (ECT) is a time tested treatment modality for the management of various psychiatric disorders. There have been a lot of modifications in the techniques of delivering ECT over decades. Despite lots of criticisms encountered, ECT has still been used commonly in clinical practice due to its safety and efficacy. Research evidences found multiple neuro-biological mechanisms for the therapeutic effect of ECT. ECT brings about various neuro-physiological as well as neuro-chemical changes in the macro- and micro-environment of the brain. Diverse changes involving expression of genes, functional connectivity, neurochemicals, permeability of blood-brain-barrier, alteration in immune system has been suggested to be responsible for the therapeutic effects of ECT. This article reviews different neurobiological mechanisms responsible for the therapeutic efficacy of ECT.

Noninvasive Evaluation of Cellular Proliferative Activity in Brain Neurogenic Regions in Rats under Depression and Treatment by Enhanced [18F]FLT-PET Imaging

Neural stem cells in two neurogenic regions, the subventricular zone and the subgranular zone (SGZ) of the hippocampal dentate gyrus, can divide and produce new neurons throughout life. Hippocampal neurogenesis is related to emotions, including depression/anxiety, and the therapeutic effects of antidepressants, as well as learning and memory. The establishment of in vivo imaging for proliferative activity of neural stem cells in the SGZ might be used to diagnose depression and to monitor the therapeutic efficacy of antidepressants. Positron emission tomography (PET) imaging with 3'-deoxy-3'-[(18)F]fluoro-l-thymidine ([(18)F]FLT) has been studied to allow visualization of proliferative activity in two neurogenic regions of adult mammals; however, the PET imaging has not been widely used because of lower accumulation of [(18)F]FLT, which does not allow quantitative assessment of the decline in cellular proliferative activity in the SGZ under the condition of depression. We report the establishment of an enhanced PET imaging method with [(18)F]FLT combined with probenecid, an inhibitor of drug transporters at the blood-brain barrier, which can allow the quantitative visualization of neurogenic activity in rats. Enhanced PET imaging allowed us to evaluate reduced cell proliferation in the SGZ of rats with corticosterone-induced depression, and further the recovery of proliferative activity in rats under treatment with antidepressants. This enhanced [(18)F]FLT-PET imaging technique with probenecid can be used to assess the dynamic alteration of neurogenic activity in the adult mammalian brain and may also provide a means for objective diagnosis of depression and monitoring of the therapeutic effect of antidepressant treatment.

SIGNIFICANCE STATEMENT

Adult hippocampal neurogenesis may play a role in major depression and antidepressant therapy. Establishment of in vivo imaging for hippocampal neurogenic activity may be useful to diagnose depression and monitor the therapeutic efficacy of antidepressants. Positron emission tomography (PET) imaging has been studied to allow visualization of neurogenic activity; however, PET imaging has not been widely used due to the lower accumulation of the PET tracer in the neurogenic regions. Here, we succeeded in establishing highly quantitative PET imaging for neurogenic activity in adult brain with an inhibitor for drug transporter. This enhanced PET imaging allowed evaluation of the decline of neurogenic activity in the hippocampus of rats with depression and the recovery of neurogenic activity by antidepressant treatment.

Hippocampal bone morphogenetic protein signaling mediates behavioral effects of antidepressant treatment

Many antidepressants stimulate adult hippocampal neurogenesis, but the mechanisms by which they increase neurogenesis and modulate behavior are incompletely understood. Here we show that hippocampal bone morphogenetic protein (BMP) signaling is modulated by antidepressant treatment, and that the changes in BMP signaling mediate effects of antidepressant treatment on neural progenitor cell proliferation and behavior. Treatment with the selective serotonin reuptake inhibitor fluoxetine suppressed BMP signaling in the adult mouse hippocampus both by decreasing levels of BMP4 ligand and increasing production of the BMP inhibitor noggin. Increasing BMP signaling in the hippocampus via viral overexpression of BMP4 blocked the effects of fluoxetine on proliferation in the dentate gyrus and on depressive behavior. Conversely, inhibiting BMP signaling via viral overexpression of noggin in the hippocampus or infusion of noggin into the ventricles exerted antidepressant and anxiolytic activity along with an increase in hippocampal neurogenesis. Similarly, conditional genetic deletion of the type II BMP receptor in Ascl1-expressing cells promoted neurogenesis and reduced anxiety- and depression-like behaviors, suggesting that neural progenitor cells contribute to the effects of BMP signaling on affective behavior. These observations indicate that BMP signaling in the hippocampus regulates depressive behavior, and that decreasing BMP signaling may be required for the effects of some antidepressants. Thus BMP signaling is a new and powerful potential target for the treatment of depression.

Hippocampal volume changes following electroconvulsive therapy: a systematic review and meta-analysis

INTRODUCTION

Reduced hippocampal volume is one of the most consistent morphological findings in Major Depressive Disorder (MDD). Electroconvulsive therapy (ECT) is the most effective therapy for MDD, yet its mechanism of action remains poorly understood. Animal models show that ECT induces several neuroplastic processes, which lead to hippocampal volume increases. We conducted a meta-analysis of ECT studies in humans to investigate its effects on hippocampal volume.

METHODS

PubMed was searched for studies examining hippocampal volume before and after ECT. A random-effects model was used for meta-analysis with standardized mean difference (SMD) of the change in hippocampal volume before and after ECT as the primary outcome. Nine studies involving 174 participants were included.

RESULTS

Total hippocampal volumes increased significantly following ECT compared to pre-treatment values (SMD=1.10; 95% CI 0.80-1.39; z=7.34; p<0.001; k=9). Both right (SMD=1.01; 95% CI 0.72-1.30; z=6.76; p<0.001; k=7) and left (SMD=0.87; 95% CI 0.51-1.23; z=4.69; p<0.001; k=7) hippocampal volumes were also similarly increased significantly following ECT. We demonstrated no correlation between improvement in depression symptoms with ECT and change in total hippocampal volume (beta=-1.28, 95% CI -4.51-1.95, z=-0.78, p=0.44).

CONCLUSION

We demonstrate fairly consistent increases in hippocampal volume bilaterally following ECT treatment. The relationship among these volumetric changes and clinical improvement and cognitive side effects of ECT should be explored by larger, multisite studies with harmonized imaging methods.

Electroconvulsive Therapy-Induced Brain Structural and Functional Changes in Major Depressive Disorders: A Longitudinal Study

Background

This study aimed to study the brain structural and functional changes after 8 courses of electroconvulsive therapy (ECT) on patients with major depressive disorder (MDD).

Material/Methods

MRI scans were performed on 12 depressive patients before and after 8 courses of ECT and compared with those of 15 normal controls. Data were analyzed by voxel-based morphometry (VBM) using SPM8 software. Functional MRI (fMRI) and regional homogeneity (ReHo) analyses were used to assess the functional changes after ECT.

Results

Grey matter volumes were smaller in the right cingulate gyrus of depressive patients before ECT compared with normal controls. After false discovery rate (FDR) correction, post-ECT grey matter volumes were increased in bilateral amygdala and hippocampus compared with pre-ECT. Resting-state ReHo maps showed significant differences in brain activity pre- and post-ECT. Compared with healthy controls, MDD patients treated with 8 courses of ECT showed higher ReHo values in the bilateral frontal lobe, bilateral parietal lobe, and right caudate nucleus. Decreased ReHo values were observed in the right medial temporal gyrus, right superior temporal gyrus, right cingulate gyrus, and left anterior cerebellar lobe.

Conclusions

Results suggested that there were both structural and functional differences between the brains of MDD patients and healthy controls. After ECT, both structural and functional changes occurred, but without complete recovery to normal. ECT may display effects through regulating other brain regions to compensate for the original defects.

M30 Antagonizes Indoleamine 2,3-Dioxygenase Activation and Neurodegeneration Induced by Corticosterone in the Hippocampus

Monoamine oxidases (MAO), downstream targets of glucocorticoid, maintain the turnover and homeostasis of monoamine neurotransmitters; yet, its pathophysiological role in monoamine deficiency, oxidative stress and neuroinflammation remains controversial. Protective effects of M30, a brain selective MAO inhibitor with iron-chelating antioxidant properties, have been shown in models of neurodegenerative diseases. This study aims to examine the neuroprotective mechanism of M30 against depressive-like behavior induced by corticosterone (CORT). Sprague-Dawley rats were given CORT subcutaneous injections with or without concomitant M30 administration for two weeks. CORT-treated rats exhibited depressive-like behavior with significant elevated levels of MAO activities, serotonin turnover, oxidative stress, neuroinflammation and apoptosis in the hippocampus with significant losses of synaptic proteins when compared to the control. The expression and activity of cytokine-responsive indoleamine 2,3-dioxygenase (IDO-1), a catabolic enzyme of serotonin and tryptophan, was significantly increased in the CORT-treated group with lowered levels of serotonin. Besides, CORT markedly reduced dendritic length and spine density. Remarkably, M30 administration neutralized the aberrant changes in the hippocampus and prevented the induction of depressive-like behavior induced by CORT. Our results suggest that M30 is neuroprotective against CORT-induced depression targeting elevated MAO activities that cause oxidative stress and neuroinflammation, resulting in IDO-1 activation, serotonin deficiency and neurodegeneration.

Adult Neurogenesis and Psychiatric Disorders

Psychiatric disorders continue to be among the most challenging disorders to diagnose and treat because there is no single genetic or anatomical locus that is causative for the disease. Current treatments are often blunt tools used to ameliorate the most severe symptoms, at the risk of disrupting functional neural systems. There is a critical need to develop new therapeutic strategies that can target circumscribed functional or anatomical domains of pathology. Adult hippocampal neurogenesis may be one such domain. Here, we review the evidence suggesting that adult hippocampal neurogenesis plays a role in emotional regulation and forms of learning and memory that include temporal and spatial memory encoding and context discrimination, and that its dysregulation is associated with psychiatric disorders, such as affective disorders, schizophrenia, and drug addiction. Further, adult neurogenesis has proven to be an effective model to investigate basic processes of neuronal development and converging evidence suggests that aberrant neural development may be an etiological factor, even in late-onset diseases. Constitutive neurogenesis in the hippocampus of the mature brain reflects large-scale plasticity unique to this region and could be a potential hub for modulation of a subset of cognitive and affective behaviors that are affected by multiple psychiatric disorders.

EFFICACY AND LONG-TERM CLINICAL OUTCOME OF COMORBID POSTTRAUMATIC STRESS DISORDER AND MAJOR DEPRESSIVE DISORDER AFTER ELECTROCONVULSIVE THERAPY

BACKGROUND

Many patients fulfill criteria for both posttraumatic stress disorder (PTSD) and major depressive disorder (MDD). Electroconvulsive therapy (ECT) is generally acknowledged to be the most-effective treatment for refractory MDD. This study investigated the efficacy of ECT on long-term clinical outcome of comorbid PTSD and MDD.

METHODS

This retrospective nested matched case-control study is inclusive of 22,164 subjects [3,485 with comorbid MDD and PTSD (92 with ECT and 3,393 without ECT) and 18,679 without MDD and PTSD].

RESULTS

Using the clinical global impression scale (CGI) to assess efficacy, more-robust improvement of PTSD and MDD symptoms was observed with ECT (90%), compared to antidepressant-treatment alone(50%) (P = 0.001). During the median of 8 years of follow-up, the death-rate was 8% in subjects without PTSD and MDD, 9.7% in PTSD and MDD treated with ECT and 18% in PTSD and MDD without ECT (P < 0.05). The suicide-rate was 2.2 and 5.9% in PTSD and MDD with and without ECT-treatment, respectively (P < 0.05). Survival-analyses revealed that the relative-risk of cardiovascular and all-cause mortality is not significantly different in patients with comorbid MDD and PTSD treated with ECT, compared to a matched-cohort without PTSD and MDD (P > 0.05). The relative risk of suicidality, all-cause, and cardiovascular mortality was reduced 64, 65, and 46% in MDD and PTSD patients treated with ECT, compared to those without ECT (P < 0.05).

CONCLUSION

ECT is associated with a significant reduction of symptoms of PTSD and MDD, as well as reduction in risk of suicidality, cardiovascular, and all-cause mortality in MDD and PTSD, an effect more robust than antidepressant-therapy alone.

Electroconvulsive therapy and structural neuroplasticity in neocortical, limbic and paralimbic cortex

Electroconvulsive therapy (ECT) is a highly effective and rapidly acting treatment for severe depression. To understand the biological bases of therapeutic response, we examined variations in cortical thickness from magnetic resonance imaging (MRI) data in 29 patients scanned at three time points during an ECT treatment index series and in 29 controls at two time points. Changes in thickness across time and with symptom improvement were evaluated at high spatial resolution across the cortex and within discrete cortical regions of interest. Patients showed increased thickness over the course of ECT in the bilateral anterior cingulate cortex (ACC), inferior and superior temporal, parahippocampal, entorhinal and fusiform cortex and in distributed prefrontal areas. No changes across time occurred in controls. In temporal and fusiform regions showing significant ECT effects, thickness differed between patients and controls at baseline and change in thickness related to therapeutic response in patients. In the ACC, these relationships occurred in treatment responders only, and thickness measured soon after treatment initiation predicted the overall ECT response. ECT leads to widespread neuroplasticity in neocortical, limbic and paralimbic regions and changes relate to the extent of antidepressant response. Variations in ACC thickness, which discriminate treatment responders and predict response early in the course of ECT, may represent a biomarker of overall clinical outcome. Because post-mortem studies show focal reductions in glial density and neuronal size in patients with severe depression, ECT-related increases in thickness may be attributable to neuroplastic processes affecting the size and/or density of neurons and glia and their connections.

Sex hormones and adult hippocampal neurogenesis: Regulation, implications, and potential mechanisms

Neurogenesis within the adult hippocampus is modulated by endogenous and exogenous factors. Here, we review the role of sex hormones in the regulation of adult hippocampal neurogenesis in males and females. The review is framed around the potential functional implications of sex hormone regulation of adult hippocampal neurogenesis, with a focus on cognitive function and mood regulation, which may be related to sex differences in incidence and severity of dementia and depression. We present findings from preclinical studies of endogenous fluctuations in sex hormones relating to reproductive function and ageing, and from studies of exogenous hormone manipulations. In addition, we discuss the modulating roles of sex, age, and reproductive history on the relationship between sex hormones and neurogenesis. Because sex hormones have diverse targets in the central nervous system, we overview potential mechanisms through which sex hormones may influence hippocampal neurogenesis. Lastly, we advocate for a more systematic consideration of sex and sex hormones in studying the functional implications of adult hippocampal neurogenesis.

Creatine, Similar to Ketamine, Counteracts Depressive-Like Behavior Induced by Corticosterone via PI3K/Akt/mTOR Pathway

Ketamine has emerged as a novel strategy to treat refractory depression, producing rapid remission, but elicits some side effects that limit its use. In an attempt to investigate a safer compound that may afford an antidepressant effect similar to ketamine, this study examined the effects of the ergogenic compound creatine in a model of depression, and the involvement of phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway in its effect. In order to induce a depressive-like behavior, mice were administered with corticosterone (20 mg/kg, per os (p.o.)) for 21 days. This treatment increased immobility time in the tail suspension test (TST), an effect abolished by a single administration of creatine (10 mg/kg, p.o.) or ketamine (1 mg/kg, i.p.), but not by fluoxetine (10 mg/kg, p.o., conventional antidepressant). Treatment of mice with wortmannin (PI3K inhibitor, 0.1 μg/site, intracerebroventricular (i.c.v.)) or rapamycin (mTOR inhibitor, 0.2 nmol/site, i.c.v.) abolished the anti-immobility effect of creatine and ketamine. None of the treatments affected locomotor activity of mice. The immunocontents of p-mTOR, p-p70S6 kinase (p70S6K), and postsynaptic density-95 protein (PSD95) were increased by creatine and ketamine in corticosterone or vehicle-treated mice. Moreover, corticosterone-treated mice presented a decreased hippocampal brain-derived neurotrophic factor (BDNF) level, an effect abolished by creatine or ketamine. Altogether, the results indicate that creatine shares with ketamine the ability to acutely reverse the corticosterone-induced depressive-like behavior by a mechanism dependent on PI3K/AKT/mTOR pathway, and modulation of the synaptic protein PSD95 as well as BDNF in the hippocampus, indicating the relevance of targeting these proteins for the management of depressive disorders. Moreover, we suggest that creatine should be further investigated as a possible fast-acting antidepressant.

Antidepressant-like Effects of Electroconvulsive Seizures Require Adult Neurogenesis in a Neuroendocrine Model of Depression

BACKGROUND

Neurogenesis continues throughout life in the hippocampal dentate gyrus. Chronic treatment with monoaminergic antidepressant drugs stimulates hippocampal neurogenesis, and new neurons are required for some antidepressant-like behaviors. Electroconvulsive seizures (ECS), a laboratory model of electroconvulsive therapy (ECT), robustly stimulate hippocampal neurogenesis.

HYPOTHESIS

ECS requires newborn neurons to improve behavioral deficits in a mouse neuroendocrine model of depression.

METHODS

We utilized immunohistochemistry for doublecortin (DCX), a marker of migrating neuroblasts, to assess the impact of Sham or ECS treatments (1 treatment per day, 7 treatments over 15 days) on hippocampal neurogenesis in animals receiving 6 weeks of either vehicle or chronic corticosterone (CORT) treatment in the drinking water. We conducted tests of anxiety- and depressive-like behavior to investigate the ability of ECS to reverse CORT-induced behavioral deficits. We also determined whether adult neurons are required for the effects of ECS. For these studies we utilized a pharmacogenetic model (hGFAPtk) to conditionally ablate adult born neurons. We then evaluated behavioral indices of depression after Sham or ECS treatments in CORT-treated wild-type animals and CORT-treated animals lacking neurogenesis.

RESULTS

ECS is able to rescue CORT-induced behavioral deficits in indices of anxiety- and depressive-like behavior. ECS increases both the number and dendritic complexity of adult-born migrating neuroblasts. The ability of ECS to promote antidepressant-like behavior is blocked in mice lacking adult neurogenesis.

CONCLUSION

ECS ameliorates a number of anxiety- and depressive-like behaviors caused by chronic exposure to CORT. ECS requires intact hippocampal neurogenesis for its efficacy in these behavioral indices.

Molecular mechanisms in the regulation of adult neurogenesis during stress

Coping with stress is fundamental for mental health, but understanding of the molecular neurobiology of stress is still in its infancy. Adult neurogenesis is well known to be regulated by stress, and conversely adult neurogenesis regulates stress responses. Recent studies in neurogenic cells indicate that molecular pathways activated by glucocorticoids, the main stress hormones, are modulated by crosstalk with other stress-relevant mechanisms, including inflammatory mediators, neurotrophic factors and morphogen signalling pathways. This Review discusses the pathways that are involved in this crosstalk and thus regulate this complex relationship between adult neurogenesis and stress.

Post-training corticosterone inhibits the return of fear evoked by platform stress and a subthreshold conditioning procedure in Sprague-Dawley rats

The return of fear is an important issue in anxiety disorder research. Each time a fear memory is reactivated, it may further strengthen overactivation of the fear circuit, which may contribute to long-term maintenance of the fear memory. Recent evidence indicates that glucocorticoids may help attenuate pathological fear, but its role in the return of fear is unclear. In the present study, systemic corticosterone (CORT; 25mg/kg) administration 1h after fear conditioning did not impair the consolidation process but significantly suppressed the return of fear evoked by a subthreshold conditioning (SC) procedure and elevated platform (EP) stress. Compared with the SC-induced return of fear, acute stress-induced return was state-dependent. In addition, post-training CORT treatment increased the adrenocorticotropic response after EP stress, which indicates that the drug-induced suppression of the return of fear may possibly derive from its regulation effect of the hypothalamic-pituitary-adrenal axis reactivity to stress. These results suggest that post-training CORT administration may help inhibit the return of fear evoked by EP or SC stress. The possible mechanisms involved in the high-dose CORT-induced suppression of the SC- and EP-induced return of fear are discussed.

Electroconvulsive shocks decrease α2-adrenoceptor binding in the Flinders rat model of depression

Despite years of drug development, electroconvulsive therapy (ECT) remains the most effective treatment for severe depression. The exact therapeutic mechanism of action of ECT is still unresolved and therefore we tested the hypothesis that the beneficial effect of ECT could in part be the result of increased noradrenergic neurotransmission leading to a decrease in α2-adrenoceptor binding. We have previously shown that both the Flinders sensitive line (FSL) and Flinders resistant line (FRL) rats had altered α2-adrenoceptor binding compared to control Sprague-Dawley (SD) rats. In this study, we treated female FSL, FRL and SD rats with electroconvulsive shock (ECS), an animal model of ECT, or sham stimulation for 10 days before brains were removed and cut into 20µm thick sections. Densities of α2-adrenoceptors were measured by quantitative autoradiography in the hippocampus, thalamic nucleus, hypothalamus, amygdala, frontal cortex, insular cortex, and perirhinal cortex using the α2-adrenoceptor antagonist, [(3)H]RX 821002. ECS decreased the binding of α2-adrenoceptors in cortical regions in the FSL and cortical and amygdaloid regions in the control FRL rats compared to their respective sham treated group. The normal SD controls showed no significant response to ECS treatment. Our data suggest that the therapeutic effect of ECS may be mediated through a decrease of α2-adrenoceptors, probably due to a sustained increase in noradrenaline release. These data confirm the importance of the noradrenergic system and the α2-adrenoceptor in depression and in the mechanism of antidepressant treatments.

Neuroprotective effect of water extract of Panax ginseng on corticosterone-induced apoptosis in PC12 cells and its underlying molecule mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Panax ginseng C.A. Meyer (Family Araliaceae) is an important medicinal plant which has been employed as a panacea for more than 2,000 years in China. It has the actions of invigorating primordial qi, recovering pulse and desertion, engendering liquid, and calming spirit. The water extract of Panax ginseng (WEG) has been used to treat kinds of central nervous system disorders, such as depression, insomnia, Alzheimer׳s disease and Parkinson׳s disease. Our previous work has demonstrated that WEG possessed antidepressant-like activities in both acute and chronic stress models of depression. Nevertheless, there are no studies on the cytoprotection and potential mechanisms of WEG on corticosterone-induced apoptosis. The present study focuses on cytoprotection against corticosterone-induced neurotoxicity in PC12 cells and its underlying molecule mechanisms of the antidepressant-like effect of WEG.

MATERIALS AND METHODS

The PC12 cells were treated with 250 μmol/L corticosterone in the absence or presence of WEG for 24h, then 3-(4,5-dimethy thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) detection, Hoechst33342 staining and TUNEL staining were investigated to confirm the neuroprotection of WEG. Then, mitochondrial permeability transition pore (mPTP), mitochondrial membrane potential (MMP), intracellular Ca(2+) ([Ca(2+)]i), reactive oxygen species (ROS) concentration, and the expression level of glucocorticoid receptor (GR), heat shock protein 90 (Hsp90), histone deactylase 6 (HDAC6), glucose-regulated protein 78 (GRP78), growth arrest and DNA damage inducible protein 153 (GADD153), X-box DNA-binding protein-1 (XBP-1), caspase-12, cytochrome C, inhibitor of caspase-activated deoxyribonuclease (ICAD), caspase-3 and caspase-9 were assessed by Western Blot analysis to understand the molecule mechanisms of neuroprotection of WEG.

RESULTS

WEG partly reversed corticosterone-induced damage in PC12 cells, which increased cell viability, decreased LDH release, and attenuated corticosterone-induced apoptosis as compared with the corticosterone-treated group. Mechanistically, compared with the corticosterone-treated group, WEG strongly attenuated [Ca(2+)]i overload and ROS level, and restored mitochondrial function, including mPTP and MMP. Furthermore, WEG strongly up-regulated the expression of GR and HDAC6, and down-regulated the expression of Hsp90, cytochrome C, ICAD, caspase-3, caspase-9 as well as endoplasmic reticulum (ER) stress-related proteins, such as GADD153, GRP78, XBP-1, and caspase-12.

CONCLUSION

WEG possessed neuroprotection against corticosterone-induced damage in PC12 cells, and the underlying molecule mechanisms was depended on the intervening of HDAC6 and HSP90 of the GR-related function proteins, and subsequent restoration of ER and mitochondria functions.

Electroconvulsive therapy treatment in patients with somatic symptom and related disorders

OBJECTIVE

Medically unexplained somatic complaints are highly prevalent, and lead to significant impairment and disability. The number of effective treatment modalities for somatic symptom and related disorders (SSDs) or somatoform disorders (SDs) remains limited. To date, there is no formal indication for electroconvulsive therapy (ECT) in SSD or SD. We report on the largest case series to date regarding the effectiveness of ECT in patients with SSD and SD.

METHODS

A retrospective chart review of all patients treated with an index course of ECT at the Neuropsychiatric Program at the University of British Columbia Hospital from 2000 to 2010 was conducted. The primary outcomes consisted of changes in pseudoneurologic symptoms, pain symptoms, cardiopulmonary symptoms, and gastrointestinal symptoms. Complaints were examined pre- and post-ECT.

RESULTS

Twenty-eight participants were included in this study. Twenty-one participants received right unilateral ECT. Six received bifrontal ECT. One received bitemporal ECT. Eighteen of 21 participants reported improvement in pseudoneurologic symptoms; eleven of 14 participants reported improvement in pain symptoms; one participant reported improvement in cardiopulmonary symptoms; and one of two participants reported improvement in gastrointestinal symptoms. This paper discusses the putative mechanism of action of ECT in the treatment of SD/SSD.

CONCLUSION

This retrospective study suggests that ECT could be included as part of the existing treatment for refractory SSD and SD, particularly in refractory cases with comorbid mood disorders.

Roles of olfactory system dysfunction in depression

The olfactory system is involved in sensory functions, emotional regulation and memory formation. Olfactory bulbectomy in rat has been employed as an animal model of depression for antidepressant discovery studies for many years. Olfaction is impaired in animals suffering from chronic stress, and patients with clinical depression were reported to have decreased olfactory function. It is believed that the neurobiological bases of depression might include dysfunction in the olfactory system. Further, brain stimulation, including nasal based drug delivery could provide novel therapies for management of depression.

Baicalin influences the dendritic morphology of newborn neurons in the hippocampus of chronically stressed rats

Chronic stress models, established in adult Sprague-Dawley rats through a 14-day subcutaneous injection of 40 mg/kg corticosterone, once per day, were given a daily oral feeding of 50 mg/kg baicalin. The study was an attempt to observe the effect of baicalin on neurogenesis in chronically stressed rats. Results showed that subcutaneous injection of corticosterone significantly decreased the total number of doublecortin-positive neurons in the hippocampus. The reduced cell number caused by corticosterone was mainly due to the decrease of class II doublecortin-positive neurons, but the class I doublecortin-positive neurons were unaffected. Baicalin treatment increased the number of both class I and class II doublecortin-positive neurons. In addition, doublecortin-positive neurons showed less complexity in dendritic morphology after corticosterone injection, and this change was totally reversed by baicalin treatment. These findings suggest that baicalin exhibits a beneficial effect on adult neurogenesis.

Effects of brief pulse and ultrabrief pulse electroconvulsive stimulation on rodent brain and behaviour in the corticosterone model of depression

Brief pulse electroconvulsive therapy (BP ECT; pulse width 0.5-1.5 ms) is the most effective treatment available for severe depression. However, its use is associated with side-effects. The stimulus in ultrabrief pulse ECT (UBP ECT; pulse width 0.25-0.3 ms) is more physiological and has been reported to be associated with less cognitive side-effects, but its antidepressant effectiveness is not yet well established. Using electroconvulsive stimulation (ECS), the animal model of ECT, we previously reported UBP ECS to be significantly less effective than well-established BP ECS in eliciting behavioural, molecular and cellular antidepressant-related effects in naïve rats. We have now compared the effects of BP and UBP ECS in an animal model of depression related to exogenous supplementation with the stress-induced glucocorticoid hormone, corticosterone. Corticosterone administration resulted in an increase in immobility time in the forced swim test (FST) (p < 0.01) and decreases in the expression of brain-derived neurotrophic factor (BDNF) (p < 0.05) and glial fibrillary acidic protein (GFAP) (p < 0.001) in the hippocampus and frontal cortex. There was no significant difference in the duration or type of seizure induced by BP (0.5 ms) or UBP (0.3 ms) ECS. UBP ECS proved to be as effective as BP ECS at inducing a behavioural antidepressant response in the FST with a significant decrease (p < 0.001) in immobility seen following administration of ECS. Both forms of ECS also induced significant increases in BDNF protein (p < 0.01) expression in the hippocampus. BP ECS (p < 0.05) but not UBP ECS induced a significant increase in GFAP levels in the hippocampus and frontal cortex. Overall, UBP ECS effectively induced antidepressant-related behavioural and molecular responses in the corticosterone supplementation model, providing the first preclinical data on the potential role of this form of ECS to treat a depression phenotype related to elevated corticosterone.

High-dose corticosterone after fear conditioning selectively suppresses fear renewal by reducing anxiety-like response

Exposure therapy is widely used to treat anxiety disorders, including posttraumatic stress disorder (PTSD). However, preventing the return of fear is still a major challenge after this behavioral treatment. An increasing number of studies suggest that high-dose glucocorticoid treatment immediately after trauma can alleviate the symptoms of PTSD in humans. Unknown is whether high-dose glucocorticoid treatment following fear conditioning suppresses the return of fear. In the present study, a typical fear renewal paradigm (AAB) was used, in which the fear response to an auditory cue can be restored in a novel context (context B) when both training and extinction occur in the same context (context A). We trained rats for auditory fear conditioning and administered corticosterone (CORT; 5 and 25mg/kg, i.p.) or vehicle with different delays (1 and 24h). Forty-eight hours after drug injection, extinction was conducted with no drug in the training context, followed by a test of tone-induced freezing behavior in the same (AAA) or a shifted (AAB) context. Both immediate and delayed administration of high-dose CORT after fear conditioning reduced fear renewal. To examine the anxiolytic effect of CORT, independent rats were trained for cued or contextual fear conditioning, followed by an injection of CORT (5 and 25mg/kg, i.p.) or vehicle at a 1 or 24h delay. One week later, anxiety-like behavior was assessed in the elevated plus maze (EPM) before and after fear expression. We found that high-dose CORT decreased anxiety-like behavior without changing tone- or context-induced freezing. These findings indicate that a single high-dose CORT administration given after fear conditioning may selectively suppress fear renewal by reducing anxiety-like behavior and not by altering the consolidation, retrieval, or extinction of fear memory.

Hippocampal neurogenesis and antidepressive therapy: shocking relations

Speculations on the involvement of hippocampal neurogenesis, a form of neuronal plasticity, in the aetiology of depression and the mode of action of antidepressive therapies, started to arise more than a decade ago. But still, conclusive evidence that adult neurogenesis contributes to antidepressive effects of pharmacological and physical therapies has not been generated yet. This review revisits recent findings on the close relation between the mode(s) of action of electroconvulsive therapy (ECT), a powerful intervention used as second-line treatment of major depression disorders, and the neurogenic response to ECT. Following application of electroconvulsive shocks, intricate interactions between neurogenesis, angiogenesis, and microglia activation, the hypothalamic-pituitary-adrenal axis and the secretion of neurotrophic factors have been documented. Furthermore, considering the fact that neurogenesis strongly diminishes along aging, we investigated the response to electroconvulsive shocks in young as well as in aged cohorts of mice.

Sustained Running in Rats Administered Corticosterone Prevents the Development of Depressive Behaviors and Enhances Hippocampal Neurogenesis and Synaptic Plasticity without Increasing Neurotrophic Factor Levels

We have previously shown that voluntary running acts as an anxiolytic and ameliorates deficits in hippocampal neurogenesis and spatial learning. It also reduces depression-like behaviors that are normally observed in rats that were administered either low (30 mg/kg) or moderate (40 mg/kg) doses of corticosterone (CORT). However, the protective effects of running were absent in rats treated with a high (50 mg/kg) dose of CORT. We examined whether allowing animals to exercise for 2 weeks prior and/or concurrently with the administration of 50 mg/kg CORT treatment could have similar protective effects. We examined hippocampal neurogenesis using immuno-histochemical staining of proliferative and survival cells with the thymidine analogs (BrdU, CIdU, and IdU). In addition, we monitored synaptic protein expression and quantified the levels of neurotrophic factors in these animals as well as performing behavioral analyses (forced swim test and sucrose preference test). Our results indicate that the depressive phenotype and reductions in neurogenesis that normally accompany high CORT administration could only be prevented by allowing animals to exercise both prior to and concurrently with the CORT administration period. These animals also showed increases in both synaptophysin and PSD-95 protein levels, but surprisingly, neither brain-derived neurotrophic factor (BDNF) nor insulin-like growth factor 1 (IGF-1) levels were increased in these animals. The results suggest that persistent exercise can strengthen resilience to stress by promoting hippocampal neurogenesis and increasing synaptic protein levels, thereby reducing the deleterious effects of stress.

Hippocampal volume in relation to clinical and cognitive outcome after electroconvulsive therapy in depression

OBJECTIVE

In a previous magnetic resonance imaging (MRI) study, we found a significant increase in hippocampal volume immediately after electroconvulsive therapy (ECT) in patients with depression. The aim of this study was to evaluate hippocampal volume up to 1 year after ECT and investigate its possible relation to clinical and cognitive outcome.

METHOD

Clinical and cognitive outcome in 12 in-patients with depression receiving antidepressive pharmacological treatment referred for ECT were investigated with the Montgomery-Asberg Depression Rating Scale (MADRS) and a broad neuropsychological test battery within 1 week before and after ECT. The assessments were repeated 6 and 12 months after baseline in 10 and seven of these patients, respectively. Hippocampal volumes were measured on all four occasions with 3 Tesla MRI.

RESULTS

Hippocampal volume returned to baseline during the follow-up period of 6 months. Neither the significant antidepressant effect nor the significant transient decrease in executive and verbal episodic memory tests after ECT could be related to changes in hippocampal volume. No persistent cognitive side effects were observed 1 year after ECT.

CONCLUSION

The immediate increase in hippocampal volume after ECT is reversible and is not related to clinical or cognitive outcome.

Electroconvulsive therapy-induced brain plasticity determines therapeutic outcome in mood disorders

There remains much scientific, clinical, and ethical controversy concerning the use of electroconvulsive therapy (ECT) for psychiatric disorders stemming from a lack of information and knowledge about how such treatment might work, given its nonspecific and spatially unfocused nature. The mode of action of ECT has even been ascribed to a "barbaric" form of placebo effect. Here we show differential, highly specific, spatially distributed effects of ECT on regional brain structure in two populations: patients with unipolar or bipolar disorder. Unipolar and bipolar disorders respond differentially to ECT and the associated local brain-volume changes, which occur in areas previously associated with these diseases, correlate with symptom severity and the therapeutic effect. Our unique evidence shows that electrophysical therapeutic effects, although applied generally, take on regional significance through interactions with brain pathophysiology.