ECS-Induced mossy fiber sprouting and BDNF expression are attenuated by ketamine pretreatment

Targeting metaplasticity mechanisms to promote sustained antidepressant actions

The discovery that subanesthetic doses of (R, S)-ketamine (ketamine) and (S)-ketamine (esketamine) rapidly induce antidepressant effects and promote sustained actions following drug clearance in depressed patients who are treatment-resistant to other therapies has resulted in a paradigm shift in the conceptualization of how rapidly and effectively depression can be treated. Consequently, the mechanism(s) that next generation antidepressants may engage to improve pathophysiology and resultant symptomology are being reconceptualized. Impaired excitatory glutamatergic synapses in mood-regulating circuits are likely a substantial contributor to the pathophysiology of depression. Metaplasticity is the process of regulating future capacity for plasticity by priming neurons with a stimulation that alters later neuronal plasticity responses. Accordingly, the development of treatment modalities that specifically modulate the duration, direction, or magnitude of glutamatergic synaptic plasticity events such as long-term potentiation (LTP), defined here as metaplastogens, may be an effective approach to reverse the pathophysiology underlying depression and improve depression symptoms. We review evidence that the initiating mechanisms of pharmacologically diverse rapid-acting antidepressants (i.e., ketamine mimetics) converge on consistent downstream molecular mediators that facilitate the expression/maintenance of increased synaptic strength and resultant persisting antidepressant effects. Specifically, while the initiating mechanisms of these therapies may differ (e.g., cell type-specificity, N-methyl-D-aspartate receptor (NMDAR) subtype-selective inhibition vs activation, metabotropic glutamate receptor 2/3 antagonism, AMPA receptor potentiation, 5-HT receptor-activating psychedelics, etc.), the sustained therapeutic mechanisms of putative rapid-acting antidepressants will be mediated, in part, by metaplastic effects that converge on consistent molecular mediators to enhance excitatory neurotransmission and altered capacity for synaptic plasticity. We conclude that the convergence of these therapeutic mechanisms provides the opportunity for metaplasticity processes to be harnessed as a druggable plasticity mechanism by next-generation therapeutics. Further, targeting metaplastic mechanisms presents therapeutic advantages including decreased dosing frequency and associated diminished adverse responses by eliminating the requirement for the drug to be continuously present.

Serial electroconvulsive Seizure alters dendritic complexity and promotes cellular proliferation in the mouse dentate gyrus; a role for Egr3

BACKGROUND

Despite being one of the safest, most effective treatments for severe mood disorders, the therapeutic mechanisms of electroconvulsive therapy remain unknown. Electroconvulsive seizure (ECS) induces rapid, high-level expression of immediate early genes (IEGs) and brain-derived neurotrophic factor (BDNF), in addition to stimulation of neurogenesis and dendritic remodeling of dentate gyrus (DG) neurons. We have previously shown that this upregulation of BDNF fails to occur in the hippocampus of mice lacking the IEG Egr3. Since BDNF influences neurogenesis and dendritic remodeling, we hypothesized that Egr3-/- mice will exhibit deficits in neurogenesis and dendritic remodeling in response to ECS.

OBJECTIVE

To test this hypothesis, we examined dendritic remodeling and cellular proliferation in the DG of Egr3-/- and wild-type mice following repeated ECS.

METHODS

Mice received 10 daily ECSs. Dendritic morphology was examined in Golgi-Cox-stained tissue and cellular proliferation was analyzed through bromodeoxyuridine (BrdU) immunohistochemistry and confocal imaging.

RESULTS

Serial ECS in mice results in dendritic remodeling, increased spine density, and cellular proliferation in the DG. Loss of Egr3 alters the dendritic remodeling induced by serial ECS but does not change the number of dendritic spines or cellular proliferation consequences of ECS.

CONCLUSION

Egr3 influences the dendritic remodeling induced by ECS but is not required for ECS-induced proliferation of hippocampal DG cells.

Exploring the Therapeutic Effect of Neurotrophins and Neuropeptides in Neurodegenerative Diseases: at a Glance

Neurotrophins and neuropeptides are the essential regulators of peripheral nociceptive nerves that help to induce, sensitize, and maintain pain. Neuropeptide has a neuroprotective impact as it increases trophic support, regulates calcium homeostasis, and reduces excitotoxicity and neuroinflammation. In contrast, neurotrophins target neurons afflicted by ischemia, epilepsy, depression, and eating disorders, among other neuropsychiatric conditions. Neurotrophins are reported to inhibit neuronal death. Strategies maintained for "brain-derived neurotrophic factor (BDNF) therapies" are to upregulate BDNF levels using the delivery of protein and genes or compounds that target BDNF production and boosting BDNF signals by expanding with BDNF mimetics. This review discusses the mechanisms of neurotrophins and neuropeptides against acute neural damage as well as highlighting neuropeptides as a potential therapeutic agent against Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), and Machado-Joseph disease (MJD), the signaling pathways affected by neurotrophins and their receptors in both standard and diseased CNS systems, and future perspectives that can lead to the potent application of neurotrophins and neuropeptides in neurodegenerative diseases (NDs).

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.

Reduced Synaptic Plasticity Contributes to Resistance Against Constant-Stimulus Electroconvulsive Treatment in a Rat Model of Stress-Induced Depression

PURPOSE

Depression is a common mood disorder in humans worldwide. Electroconvulsive therapy (ECT) remains the most effective treatment for patients with drug-resistant or severe depression; however, during ECT, electrical resistance can occur, antagonizing ECT efficacy. We aimed to investigate how depressed patients develop resistance to electric shocks during ECT.

METHODS

Rats exposed to chronic unpredictable stress exert similar impairments in hippocampal synaptic plasticity as those in depressed humans, including hippocampal neuronal atrophy and reduced synaptic function and synapse-related proteins. Therefore, a rat model was used to model depressive-like behaviors in the current study. Depression-like behavior was stimulated in Sprague Dawley (SD) rats that were then randomized into six groups: control group (C); a rat model of stress-induced depression group (D); and four groups in which a rat model of stress-induced depression received one, three, five, or seven electroconvulsive shocks (ECS; DE1, DE3, DE5, and DE7). The sucrose preference test (SPT) and Morris water maze (MWM) were utilized to evaluate anhedonia and spatial learning and memory in rats, respectively. Synaptic plasticity was recorded electrophysiologically in terms of field excitatory postsynaptic potential (fEPSP) and long-term potentiation (LTP).

RESULTS

The rat model of stress-induced depression triggered a decrease in the sucrose preference percentage (SPP) and the baseline fEPSP slope relative to those observed for the C group, and these changes were significantly rescued by ECT in a shock number-dependent manner within five shocks. However, the rat model of stress-induced depression displayed an increase in the escape latency and a decrease in space exploration time, in addition to decreased LTP relative to those in the C group, which was further augmented by ECT in a shock number-dependent manner within five shocks.

CONCLUSION

Changes in synaptic plasticity might be responsible for the development of resistance against constant-stimulus ECT in a rat model of stress-induced depression.

Hippocampal volume change following ECT is mediated by rs699947 in the promotor region of VEGF

Several studies have shown that electroconvulsive therapy (ECT) results in increased hippocampal volume. It is likely that a multitude of mechanisms including neurogenesis, gliogenesis, synaptogenesis, angiogenesis, and vasculogenesis contribute to this volume increase. Neurotrophins, like vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF) seem to play a crucial mediating role in several of these mechanisms. We hypothesized that two regulatory SNPs in the VEGF and BDNF gene influence the changes in hippocampal volume following ECT. We combined genotyping and brain MRI assessment in a sample of older adults suffering from major depressive disorder to test this hypothesis. Our results show an effect of rs699947 (in the promotor region of VEGF) on hippocampal volume changes following ECT. However, we did not find a clear effect of rs6265 (in BDNF). To the best of our knowledge, this is the first study investigating possible genetic mechanisms involved in hippocampal volume change during ECT treatment.

Effect of voluntary running on expression of myokines in brains of rats with depression

This study aimed to demonstrate the histopathology and immunoexpression of exercise-derived myokines in dentate gyrus (DG), medial prefrontal cortex (mPFC) and cerebellum of depressed Wistar rats during depression and after practising voluntary running. Depression was developed by forced swimming for 2 weeks. Voluntary running was performed by voluntary running for 3 weeks. Brain sections were processed and immunostained to detect brain-derived neurotrophic factor (BDNF), macrophage migration inhibitory factor (MIF), vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6). ImageJ software was used to measure the optical density (OD). BDNF was expressed in neurons in DG, mPFC and granular and Purkinje cells in cerebellum. MIF was expressed in neurons of sub-granular zone in DG, mPFC and Purkinje cells. VEGF was expressed in many neurons in DG, mPFC and Purkinje cells. IL-6 was expressed in some neurons in DG, in neuropil of mPFC and in Purkinje cells. In depression, the OD of studied myokines significantly decreased in all examined areas. After voluntary running, the OD of myokines significantly increased in all areas. This study defines the immunohistochemical expression of myokines in brain areas in depression and after voluntary running and reveals the involvement of the mPFC and cerebellum in the pathophysiology of depression.

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.

Neuroprotective Effect of Modified Electroconvulsive Therapy for Schizophrenia: A Proton Magnetic Resonance Spectroscopy Study

The underlying mechanism of modified electroconvulsive therapy (MECT) treatment for drug-resistant and catatonic schizophrenia remains unclear. Here, we aim to investigate whether MECT exerts its antipsychotic effects through elevating N-acetylaspartate (NAA) concentration measured by proton magnetic resonance spectroscopy (H-MRS). Multiple-voxel H-MRS was acquired in the bilateral prefrontal cortex (PFC) and thalamus to obtain measures of neurochemistry in 32 MECT, 34 atypical antipsychotic-treated schizophrenic patients, and 34 healthy controls. We found that both MECT and atypical antipsychotic treatments showed significant antipsychotic efficacy. MECT and atypical antipsychotic treatments reversed the reduced NAA/creatine ratio (NAA/Cr) in the left PFC and left thalamus in schizophrenic patients compared with healthy controls. Furthermore, the NAA/Cr ratio after treatments was significant higher in the MECT group, but not in the medication group. Our findings demonstrate that eight times of MECT elevated the relative NAA concentration to display neuroprotective effect, which may be the underlying mechanism of rapid antipsychotic efficacy.

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.

Identifying fast-onset antidepressants using rodent models

Depression is a leading cause of disability worldwide and a major contributor to the burden of suicide. A major limitation of classical antidepressants is that 2-4 weeks of continuous treatment is required to elicit therapeutic effects, prolonging the period of depression, disability and suicide risk. Therefore, the development of fast-onset antidepressants is crucial. Preclinical identification of fast-onset antidepressants requires animal models that can accurately predict the delay to therapeutic onset. Although several well-validated assay models exist that predict antidepressant potential, few thoroughly tested animal models exist that can detect therapeutic onset. In this review, we discuss and assess the validity of seven rodent models currently used to assess antidepressant onset: olfactory bulbectomy, chronic mild stress, chronic forced swim test, novelty-induced hypophagia (NIH), novelty-suppressed feeding (NSF), social defeat stress, and learned helplessness. We review the effects of classical antidepressants in these models, as well as six treatments that possess fast-onset antidepressant effects in the clinic: electroconvulsive shock therapy, sleep deprivation, ketamine, scopolamine, GLYX-13 and pindolol used in conjunction with classical antidepressants. We also discuss the effects of several compounds that have yet to be tested in humans but have fast-onset antidepressant-like effects in one or more of these antidepressant onset sensitive models. These compounds include selective serotonin (5-HT)_2C receptor antagonists, a 5-HT₄ receptor agonist, a 5-HT₇ receptor antagonist, NMDA receptor antagonists, a TREK-1 receptor antagonist, mGluR antagonists and (2R,6R)-HNK. Finally, we provide recommendations for identifying fast-onset antidepressants using rodent behavioral models and molecular approaches.

Spatial memory impairment in Morris water maze after electroconvulsive seizures

OBJECTIVE

Electroconvulsive therapy (ECT) is one of the most efficient treatments for severe major depression, but some patients suffer from retrograde memory loss after treatment. Electroconvulsive seizures (ECS), an animal model of ECT, have repeatedly been shown to increase hippocampal neurogenesis, and multiple ECS treatments cause retrograde amnesia in hippocampus-dependent memory tasks. Since recent studies propose that addition of newborn hippocampal neurons might degrade existing memories, we investigated whether the memory impairment after multiple ECS treatments is a cumulative effect of repeated treatments, or if it is the result of a delayed effect after a single ECS.

METHODS

We used the hippocampus-dependent memory task Morris water maze (MWM) to evaluate spatial memory. Rats were exposed to an 8-day training paradigm before receiving either a single ECS or sham treatment and tested in the MWM 24 h, 72 h, or 7 days after this treatment, or multiple (four) ECS or sham treatments and tested 7 days after the first treatment.

RESULTS

A single ECS treatment was not sufficient to cause retrograde amnesia whereas multiple ECS treatments strongly disrupted spatial memory in the MWM.

CONCLUSION

The retrograde amnesia after multiple ECS is a cumulative effect of repeated treatments rather than a delayed effect after a single ECS.

Significant treatment effect of add-on ketamine anesthesia in electroconvulsive therapy in depressive patients: A meta-analysis

Add-on ketamine anesthesia in electroconvulsive therapy (ECT) has been studied in depressive patients in several clinical trials with inconclusive findings. Two most recent meta-analyses reported insignificant findings with regards to the treatment effect of add-on ketamine anesthesia in ECT in depressive patients. The aim of this study is to update the current evidence and investigate the role of add-on ketamine anesthesia in ECT in depressive patients via a systematic review and meta-analysis. We performed a thorough literature search of the PubMed and ScienceDirect databases, and extracted all relevant clinical variables to compare the antidepressive outcomes between add-on ketamine anesthesia and other anesthetics in ECT. Total 16 articles with 346 patients receiving add-on ketamine anesthesia in ECT and 329 controls were recruited. We found that the antidepressive treatment effect of add-on ketamine anesthesia in ECT in depressive patients was significantly higher than that of other anesthetics (p<0.001). This significance persisted in both short-term (1-2 weeks) and moderate-term (3-4 weeks) treatment courses (all p<0.05). However, the side effect profiles and recovery time profiles were significantly worse in add-on ketamine anesthesia group than in control group. Our meta-analysis highlights the significantly higher antidepressive treatment effect of add-on ketamine in depressive patients receiving ECT compared to other anesthetics. However, clinicians need to take undesirable side effects into consideration when using add-on ketamine anesthesia in ECT in depressive patients.

Hippocampal VEGF is necessary for antidepressant-like behaviors but not sufficient for antidepressant-like effects of ketamine in rats

We investigated the effects of ketamine on both the temporal and spatial profiles of neural precursor cells located in the hippocampus, and on antidepressant-like behaviors in rats. A single dose of ketamine resulted in a significant increase in the number of 5-bromo-2-deoxyuridine-positive (BrdU(+)) cells in the dentate gyrus (DG) of rats at 24h, but not at 28days, after treatment completion. Ketamine caused antidepressant-like behaviors in the forced swim test (FST) and novelty suppressed feeding test (NSFT). Viral-mediated hippocampal knockdown of vascular endothelial growth factor (VEGF) produced depressive-like behaviors in the FST and NSFT, which were partially recovered by ketamine to the level observed in the control group. The behavioral effects of VEGF knock down were accompanied by a decrease in hippocampal neurogenesis, which was also partially recovered by ketamine. Our results suggest that basal hippocampal VEGF expression is necessary for ketamine-induced antidepressant-like behaviors in rats, but ketamine-induced VEGF expression only partially contributes to hippocampal neurogenesis and the antidepressant-like effects of ketamine.

Seizure-Induced Regulations of Amyloid-β, STEP61, and STEP61 Substrates Involved in Hippocampal Synaptic Plasticity

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline. Pathologic accumulation of soluble amyloid-β (Aβ) oligomers impairs synaptic plasticity and causes epileptic seizures, both of which contribute to cognitive dysfunction in AD. However, whether seizures could regulate Aβ-induced synaptic weakening remains unclear. Here we show that a single episode of electroconvulsive seizures (ECS) increased protein expression of membrane-associated STriatal-Enriched protein tyrosine Phosphatase (STEP₆₁) and decreased tyrosine-phosphorylation of its substrates N-methyl D-aspartate receptor (NMDAR) subunit GluN2B and extracellular signal regulated kinase 1/2 (ERK1/2) in the rat hippocampus at 2 days following a single ECS. Interestingly, a significant decrease in ERK1/2 expression and an increase in APP and Aβ levels were observed at 3-4 days following a single ECS when STEP₆₁ level returned to the baseline. Given that pathologic levels of Aβ increase STEP₆₁ activity and STEP₆₁-mediated dephosphorylation of GluN2B and ERK1/2 leads to NMDAR internalization and ERK1/2 inactivation, we propose that upregulation of STEP₆₁ and downregulation of GluN2B and ERK1/2 phosphorylation mediate compensatory weakening of synaptic strength in response to acute enhancement of hippocampal network activity, whereas delayed decrease in ERK1/2 expression and increase in APP and Aβ expression may contribute to the maintenance of this synaptic weakening.

Brain-Derived Neurotrophic Factor and Antidepressive Effect of Electroconvulsive Therapy: Systematic Review and Meta-Analyses of the Preclinical and Clinical Literature

Emerging data suggest that Electro-Convulsive Treatment (ECT) may reduce depressive symptoms by increasing the expression of Brain-Derived Neurotrophic Factor (BDNF). Yet, conflicting findings have been reported. For this reason we performed a systematic review and meta-analysis of the preclinical and clinical literature on the association between ECT treatment (ECS in animals) and changes in BDNF concentrations and their effect on behavior. In addition, regional brain expression of BDNF in mouse and human brains were compared using Allen Brain Atlas. ECS, over sham, increased BDNF mRNA and protein in animal brain (effect size [Hedge’s g]: 0.38―0.54; 258 effect-size estimates, N = 4,284) but not in serum (g = 0.06, 95% CI = -0.05―0.17). In humans, plasma but not serum BDNF increased following ECT (g = 0.72 vs. g = 0.14; 23 effect sizes, n = 281). The gradient of the BDNF increment in animal brains corresponded to the gradient of the BDNF gene expression according to the Allen brain atlas. Effect-size estimates were larger following more ECT sessions in animals (r = 0.37, P < .0001) and in humans (r = 0.55; P = 0.05). There were some indications that the increase in BDNF expression was associated with behavioral changes in rodents, but not in humans. We conclude that ECS in rodents and ECT in humans increase BDNF concentrations but this is not consistently associated with changes in behavior.

Effects of (+)-8-OH-DPAT on the duration of immobility during the forced swim test and hippocampal cell proliferation in ACTH-treated rats

In the present study, we examined the effect of ACTH on the immobilization of rats in the forced swim test and hippocampal cell proliferation after administration of the 5-HT1A receptor agonist, R-(+)-8-hydroxy-2-di-n-propylamino tetralin ((+)-8-OH-DPAT). Chronic treatment with (+)-8-OH-DPAT (0.01-0.1 mg/kg, s.c.) significantly decreased the duration of immobility in saline- and ACTH-treated rats. Chronic administration of ACTH caused a significant decrease in hippocampal cell proliferation. However, (+)-8-OH-DPAT significantly normalized cell proliferation in ACTH-treated rats. We then investigated the effects of (+)-8-OH-DPAT on the expression of brain-derived neurotrophic factor (BDNF) and cyclin D1 (elements of cyclic adenosine monophosphate response element-binding protein (CREB)-BDNF and Wnt signaling pathways, respectively) in the hippocampus of saline- and ACTH-treated rats. ACTH treatment significantly decreased the expression of cyclin D1, while treatment with (+)-8-OH-DPAT normalized the expression of cyclin D1 in ACTH-treated rats. However, the expression of BDNF did not change in either saline- or ACTH-treated rats. These findings suggest that the antidepressant effects of (+)-8-OH-DPAT in treatment-resistant animals may be attributed to an enhancement of hippocampal cell proliferation, at least in part due to an enhancement of cyclin D1 expression.

Neurotrophins in mesial temporal lobe epilepsy with and without psychiatric comorbidities

Despite the strong association between epilepsy and psychiatric comorbidities, data on clinicopathologic correlations are scant. We previously reported differential mossy fiber sprouting (MFS) in mesial temporal lobe epilepsy (MTLE) patients with psychosis (MTLE + P) and major depression (MTLE + D). Because neurotrophins (NTs) can promote MFS, here, we investigated MFS, neuronal density and immunoreactivity for the NT nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT3) in hippocampi of 14 MTLE patients without a psychiatric history, 13 MTLE + D, 13 MTLE + P, and 10 control necropsies. Mossy fiber sprouting correlated with granular layer NGF immunoreactivity and seizure frequency. Patients with secondarily generalized seizures exhibited less NGF immunoreactivity versus patients with complex partial seizures. There was greater NT immunoreactivity in MTLE versus control groups but lesser NT immunoreactivity in MTLE + P versus MTLE patients; these findings correlated with neuropsychologic scores. Patients with MTLE + D taking fluoxetine showed greater BDNF immunoreactivity than those not taking fluoxetine; MTLE + P patients taking haloperidol had decreased neuronal density and immunoreactivity for NGF and BDNF in specific subfields versus those not taking haloperidol. There were no differences in NT3 immunoreactivity among the groups. These findings support a close association between MFS and NT expression in the hippocampi of MTLE patients and suggest that distinct structural and neurochemical milieu may contribute to the genesis or maintenance of psychiatric comorbidities in MTLE.

microRNAs as novel antidepressant targets: converging effects of ketamine and electroconvulsive shock therapy in the rat hippocampus

Early-life stress is a main contributory factor to the onset of depression. Treatments remain inadequate and as such, a large unmet medical need for novel therapeutics remains. Impeding advancement is the poor understanding of the molecular pathology. microRNAs (miRNAs) are novel regulators of gene expression. A paucity of information regarding their role in depressive pathology and antidepressant action remains. This study investigated changes to hippocampal miRNA levels induced via early-life stress in Sprague-Dawley rats and whether antidepressant treatments could reverse these changes. Investigated were the selective serotonin reuptake inhibitor fluoxetine, the rapid acting N-methyl-d-aspartate receptor antagonist ketamine and electroconvulsive shock therapy (ECT). Microarray analysis revealed early-life stress affected the expression of multiple hippocampal miRNAs. Antidepressant treatments reversed some of these effects including a stress-induced change to miR-451. Ketamine and ECT possessed the highest number of common targets suggesting convergence on common pathways. Interestingly all three treatments possessed miR-598-5p as a common target. This demonstrates that changes to hippocampal miRNA expression may represent an important component of stress-induced pathology and antidepressant action may reverse these.

Neuronal plasticity and antidepressant actions

Antidepressant treatments enhance plasticity and increase neurogenesis in the adult brain, but it has been unclear how these effects influence mood. We propose that, like environmental enrichment and exercise, antidepressant treatments enhance adaptability by increasing structural variability within the nervous system at many levels, from proliferating precursors to immature synaptic contacts. Conversely, sensory deprivation and chronic stress reduce this structural variability. Activity-dependent competition within the mood-related circuits, guided by rehabilitation, then selects for the survival and stabilization of those structures that best represent the internal or external milieu. Increased variability together with competition-mediated selection facilitates normal function, such as pattern separation within the dentate gyrus and other mood-related circuits, thereby enhancing adaptability toward novel experiences.

Disruption of component processes of spatial working memory by electroconvulsive shock but not magnetic seizure therapy

Self-ordered spatial working memory measures provide important information regarding underlying cognitive strategies, such as stereotypy. This strategy is based on repetitive sequential selection of a spatial pattern once a correct sequence has been identified. We previously reported that electroconvulsive shock (ECS) but not magnetic seizure therapy (MST) impaired performance on a spatial working memory task in a preclinical model. Here we tested the hypothesis that ECS disrupted stereotyped patterns in the selection of spatial stimuli. In a within-subject study design, we assessed the effects of ECS, MST, and sham on stereotypy and reaction time in a preclinical model. Stereotypy was assessed by the correlation of actual and predicted response patterns of spatial stimuli. Predicted patterns were based on performance during baseline sessions. ECS resulted in lower correlations between predicted and actual responses to spatial stimuli in two of the three subjects, and it also disrupted stereotypy. For one subject, there was change in the predictability of the spatial locus of responses between experimental conditions. For all three subjects, reaction time was significantly longer in ECS, relative to MST and sham. This is the first study to examine the effect of ECS, and to contrast the effects of ECS and MST, on spatial working memory component processes. Our preliminary findings show that ECS, but not MST decreased stereotypy and increased reaction time. This line of investigation may have significant implications in our understanding cognitive component processes of memory function and impairment.

Differential aberrant sprouting in temporal lobe epilepsy with psychiatric co-morbidities

Psychiatric co-morbidities in epilepsy are common in patients with temporal lobe epilepsy (TLE). Pathological alterations in TLE are well characterised; however, neuropathologic data are relatively scale regarding the association between psychiatric diseases and epilepsy. Our objective was to evaluate the clinical data of 46 adult TLE patients with and without psychiatric co-morbidities and to correlate the data with hippocampal neuronal density and mossy fiber sprouting. Accordingly, patients were grouped as follows: TLE patients without history of psychiatric disorder (TLE, n=16), TLE patients with interictal psychosis (TLE+P, n=14), and TLE patients with major depression (TLE+D, n=16). Hippocampi from autopsies served as non-epileptic controls (n=10). TLE+P exhibited significantly diminished mossy fiber sprouting and decreased neuronal density in the entorhinal cortex when compared with TLE. TLE+P showed significantly poorer results in verbal memory tasks. TLE+D exhibited significantly increased mossy fiber sprouting length when compared with TLE and TLE+P. Further, a higher proportion of TLE+D and TLE+P presented secondarily generalised seizures than did TLE. Our results indicate that TLE patients with psychiatric disorders have distinct features when compared with TLE patients without psychiatric co-morbidities and that these changes may be involved in either the manifestation or the maintenance of psychiatric co-morbidities in epilepsy.

Clinically favourable effects of ketamine as an anaesthetic for electroconvulsive therapy: a retrospective study

In a retrospective chart review, we examined the effects of ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, as electroconvulsive therapy (ECT) anaesthetic in patients suffering from therapy-resistant depression. We included 42 patients who received ECT treatment with either ketamine (n = 16) or the barbiturate thiopental (n = 26). We analysed the number of sessions until completion of ECT treatment (used as a surrogate parameter for outcome), psychopathology as assessed by pre- and post-ECT Mini-Mental State Examination (MMSE) and Hamilton Rating Scale for Depression (HAM-D) scores as well as ECT and seizure parameters (stimulation dose, seizure duration and concordance, urapidil dosage for post-seizure blood pressure management). The ketamine group needed significantly fewer ECT sessions and had significantly lower HAM-D and higher MMSE scores afterwards. As expected, the ketamine group needed more urapidil for blood pressure control. Taking into account the limits inherent in a retrospective study design and the rather small sample size, our results nonetheless point towards synergistic effects of ECT and ketamine anaesthesia, less cognitive side effects and good tolerability of ketamine.

Electroconvulsive therapy-induced persistent retrograde amnesia: could it be minimised by ketamine or other pharmacological approaches?

BACKGROUND

Certain pharmacological agents administered during electroconvulsive therapy may have the potential to prevent persistent retrograde amnesia induced during electroconvulsive therapy. This review examines mechanisms for electroconvulsive therapy-induced retrograde amnesia, and evaluates the suitability of the anaesthetic ketamine for preventing this amnestic outcome.

METHODS

A review of human studies, animal models and theoretical models in light of memory dysfunction following electroconvulsive therapy was conducted. MEDLINE was searched from 1950 to April 2009 using the MeSH terms "electroconvulsive therapy", "memory", "memory short term", "memory disorders", "excitatory amino acid antagonists", and "ketamine". PREMEDLINE was searched using the terms "electroconvulsive therapy", "amnesia" and "ketamine". Additional keyword and reference list searches were performed. No language, date constraints or article type constraints were used.

RESULTS

Disruption of long term potentiation as a mechanism for electroconvulsive therapy-induced retrograde amnesia is well supported. Based on this putative mechanism, an N-methyl-D-aspartate receptor antagonist would appear suitable for preventing the retrograde amnesia. Available evidence in animals and humans supports the prediction that ketamine, an anaesthetic agent and N-methyl-D-aspartate receptor antagonist, could effectively prevent electroconvulsive therapy-induced persistent retrograde amnesia. Whilst there are concerns about the use of ketamine with electroconvulsive therapy, such as possible psychotomimetic effects, on balance this anaesthetic agent may improve or hasten clinical response to electroconvulsive therapy.

CONCLUSIONS

A clinical trial is warranted to determine if ketamine anaesthesia during electroconvulsive therapy can lessen persistent retrograde amnesia and improve therapeutic response. Electroconvulsive therapy with ketamine anaesthesia may provide effective antidepressant action with minimal side effects.

Risperidone and haloperidol promote survival of stem cells in the rat hippocampus

Altered neuroplasticity contributes to the pathophysiology of schizophrenia. However, the idea that antipsychotics may act, at least in part, by normalizing neurogenesis has not been consistently supported. Our study seeks to determine whether hippocampal cell proliferation is altered in adult rats pretreated with ketamine, a validated model of schizophrenia, and whether chronic administration with neuroleptic drugs (haloperidol and risperidone) affect changes of cell genesis/survival. Ketamine per se has no effect on cell proliferation. Its withdrawal, however, significantly induced cell proliferation/survival in the hippocampus. Risperidone and haloperidol supported cell genesis/survival as well. During ketamine withdrawal, however, their application did not affect cell proliferation/survival additionally. TUNEL staining indicated a cell-protective potency of both neuroleptics with respect to a ketamine-induced cell death. As RT-PCR and Western blot revealed that the treatment effects of risperidone and haloperidol seemed to be mediated through activation of VEGF and MMP2. The mRNA expression of NGF, BDNF, and NT3 was unaffected. From the respective receptors, only TrkA was enhanced when ketamine withdrawal was combined with risperidone or haloperidol. Risperidone also induced BCL-2. Ketamine withdrawal has no effect on the expression of VEGF, MMP2, or BCL-2. It activated the expression of BDNF. This effect was normalized by risperidone or haloperidol. The findings indicate a promoting effect of risperidone and haloperidol on survival of young neurons in the hippocampus by enhancing the expression of the anti-apoptotic protein BCL-2 and by activation of VEGF/MMP2, whereby an interference with ketamine and thus a priority role of the NMDA system was not evident.

Neurophysiological mechanisms of electroconvulsive therapy for depression

The neurobiological foundation of electroconvulsive therapy (ECT) remains fragile. How ECT affects neural activities in the brain of depressives is largely unknown. There has been accumulating knowledge on genes and molecules induced by the animal model of ECT. Exact functions of those molecules in the context of mood disorder remain unknown. Among the dozens of molecules highly expressed by ECT, one that shows an especially prominent induction (>6-fold) is Homer 1a, a member of the intracellular scaffold protein family Homer. We have examined effects of Homer 1a in ECT-subjected cortical pyramidal cells, on the basis of which two neurobiological consequences of ECT are proposed. First, Homer 1a either injected intracellularly or induced by ECT was shown to reduce neuronal excitability. This agrees with diverse lines of mutually consistent clinical investigations, which unanimously point to an enhanced excitability in the cerebral cortex of depressive patients. The GABAergic dysfunction hypothesis of depression was thus revitalized. Second, again by relying on Homer 1a, we have proposed a molecular mechanism by which ECT affects a form of long-term depression (LTD). The possibility is discussed that clinical effects of ECT are exerted at least partly by reducing neural excitability and modifying synaptic plasticity.

Target identification for CNS diseases by transcriptional profiling

Gene expression changes in neuropsychiatric and neurodegenerative disorders, and gene responses to therapeutic drugs, provide new ways to identify central nervous system (CNS) targets for drug discovery. This review summarizes gene and pathway targets replicated in expression profiling of human postmortem brain, animal models, and cell culture studies. Analysis of isolated human neurons implicates targets for Alzheimer's disease and the cognitive decline associated with normal aging and mild cognitive impairment. In addition to tau, amyloid-beta precursor protein, and amyloid-beta peptides (Abeta), these targets include all three high-affinity neurotrophin receptors and the fibroblast growth factor (FGF) system, synapse markers, glutamate receptors (GluRs) and transporters, and dopamine (DA) receptors, particularly the D2 subtype. Gene-based candidates for Parkinson's disease (PD) include the ubiquitin-proteosome system, scavengers of reactive oxygen species, brain-derived neurotrophic factor (BDNF), its receptor, TrkB, and downstream target early growth response 1, Nurr-1, and signaling through protein kinase C and RAS pathways. Increasing variability and decreases in brain mRNA production from middle age to old age suggest that cognitive impairments during normal aging may be addressed by drugs that restore antioxidant, DNA repair, and synaptic functions including those of DA to levels of younger adults. Studies in schizophrenia identify robust decreases in genes for GABA function, including glutamic acid decarboxylase, HINT1, glutamate transport and GluRs, BDNF and TrkB, numerous 14-3-3 protein family members, and decreases in genes for CNS synaptic and metabolic functions, particularly glycolysis and ATP generation. Many of these metabolic genes are increased by insulin and muscarinic agonism, both of which are therapeutic in psychosis. Differential genomic signals are relatively sparse in bipolar disorder, but include deficiencies in the expression of 14-3-3 protein members, implicating these chaperone proteins and the neurotransmitter pathways they support as possible drug targets. Brains from persons with major depressive disorder reveal decreased expression for genes in glutamate transport and metabolism, neurotrophic signaling (eg, FGF, BDNF and VGF), and MAP kinase pathways. Increases in these pathways in the brains of animals exposed to electroconvulsive shock and antidepressant treatments identify neurotrophic and angiogenic growth factors and second messenger stimulation as therapeutic approaches for the treatment of depression.

Neuropeptides in depression: role of VGF

The monoamine hypothesis of depression is increasingly called into question by newer theories that revolve around changes in neuronal plasticity, primarily in the hippocampus, at both the structural and the functional levels. Chronic stress negatively regulates hippocampal function while antidepressants ameliorate the effects of stress on neuronal morphology and activity. Both stress and antidepressants have been shown to affect levels of brain-derived neurotrophic factor (BDNF) whose transcription is dependent on cAMP response element binding protein (CREB). BDNF itself has antidepressant-like actions and can induce transcription of a number of molecules. One class of genes regulated by both BDNF and serotonin (5-HT) are neuropeptides including VGF (non-acryonimic) which has a novel role in depression. Neuropeptides are important modulators of neuronal function but their role in affective disorders is just emerging. Recent studies demonstrate that VGF, which is also a CREB-dependent gene, is upregulated by antidepressant drugs and voluntary exercise and is reduced in animal models of depression. VGF enhances hippocampal synaptic plasticity as well as neurogenesis in the dentate gyrus but the mechanisms of antidepressant-like actions of VGF in behavioral paradigms are not known. We summarize experimental data describing the roles of BDNF, VGF and other neuropeptides in depression and how they may be acting through the generation of new neurons and altered synaptic activity. Understanding the molecular and cellular changes that underlie the actions of neuropeptides and how these adaptations result in antidepressant-like effects will aid in developing drugs that target novel pathways for major depressive disorders.

Electroconvulsive therapy, brain-derived neurotrophic factor, and possible neurorestorative benefit of the clinical application of electroconvulsive therapy

Treatment-resistant depression (TRD) is a growing problem in psychiatry. A recent meta-analysis has estimated TRD to be as high as 40%. Just over a decade ago, TRD was estimated to be as low as 10% to 15%. The causes of TRD are not fully understood. Finding ways to bring patients to remission faster may be part of the solution, but increasing our understanding of how depression works and how the brain responds to treatment may shed some light on this growing problem. Patients with TRD have been shown to have decreased volumes in gray matter structures, particularly in the hippocampus. Hippocampal volumes are correlated with decreased expression of neurotrophic factors (most notably, brain-derived neurotrophic factor [BDNF]), and decreased expression of BDNF correlates with the presence of depression. Increased expression of BDNF has a strong association with increased volumes in the hippocampus. Electroconvulsive therapy (ECT), a safe and effective treatment of severe depression, has been shown to be effective in TRD. Patients who undergo ECT have also had measurable increases in BDNF, indicating that ECT may be modulating intracellular processes in the patients with depression. Taken together, ECT may have a positive effect on restoring gray matter volume in patients with depression and especially TRD.

Neurobiological factors linking personality traits and major depression

OBJECTIVE

To examine the neurobiological basis of personality and depression.

METHOD

We examined preclinical and clinical studies related to neuroanatomy, neuroendocrine, molecular, and genetic alterations in depressed patients. We considered whether common neurobiological factors might be shared between personality and depression.

RESULTS

Preclinical studies provide insights into the neurobiological mechanisms underlying the pathophysiology of depression including neuroendocrine alterations in hypothalamic-pituitary-adrenal (HPA) function, neuroanatomical alterations in key brain regions, and alterations in neurotrophin and serotonergic signalling systems. Clinical studies show similar alterations in depressed patients. Evidence suggests that neuroendocrine alterations in HPA function may contribute to personality traits. Brain regions implicated in depression, including the hippocampus and the anterior cingulate cortex, might play a role in personality. Key molecules implicated in depression have been extensively studied with reference to personality traits, particularly neuroticism. To date, physiological measures (serum and positron emission tomography) provide the strongest evidence implicating brain-derived neurotrophic factor and serotonin in personality, while genetic evidence is less convincing.

CONCLUSIONS

A neurobiological link exists between personality and depression; however, more work is needed to provide an understanding of the nature of this relation and to link this work with clinical studies examining the influence of personality factors on depression.

Repeated electroconvulsive stimuli have long-lasting effects on hippocampal BDNF and decrease immobility time in the rat forced swim test

Electroconvulsive therapy is considered an effective treatment for severe depression. However, the mechanisms for its long-lasting antidepressant efficacy are poorly understood. In the present study, we investigated changes of the immobility time in the forced swim test and brain-derived neurotrophic factor (BDNF) protein after withdrawal from 14-day repeated electroconvulsive stimuli (ECS, 50 mA, 0.2 s) in rats. Immobility time in the forced swim test was markedly decreased 6 h after withdrawal following 14-day ECS treatment. Thereafter, prolongation of the withdrawal period gradually diminished the decreasing effect of immobility time, but significant effects persisted for up to 3 days after the withdrawal. Locomotor activity in the open-field test increased 6 h after withdrawal from the ECS treatment, and the enhanced effect persisted for at least 7 days. The BDNF protein level in the hippocampus was markedly increased 6 h after the withdrawal, and remained high for at least 7 days. These findings provide further evidence that repeated ECS has long-lasting effect on increase in BDNF and locomotor activity and decrease in immobility time in the forced swim test.

Electroconvulsive seizure increases adult hippocampal angiogenesis in rats

Electroconvulsive seizure has a proven therapeutic application in the treatment of severe depression and treatment-resistant depression. Despite the efficacy of electroconvulsive seizure as a non-chemical antidepressant treatment, the mechanism of action is unclear. Elevation in hippocampal trophic factor expression and concomitant cellular proliferation are thought to play a role in its action. We examined whether the reported induction of angiogenic factors and endothelial cell proliferation leads to an increase in vascular density. Two hippocampal regions, the dentate gyrus and the stratum lacunosum moleculare (SLM), were examined employing a combination of vascular density quantification, angiogenic gene expression analysis and immunohistochemistry. A 6% increase in vascular density was observed in the dentate gyrus but this did not achieve statistical significance. The SLM of the hippocampus exhibited a robust 20-30% increase in vascular density and was accompanied by an increase in expression of inhibitor of differentiation-3. There was also an induction of the angiogenesis markers alphaVbeta3 integrin and Del1. Increases in the vascular density of the SLM could be in response to enhanced metabolic activity in this region. This is supported by the induction of glutamine synthetase and the glutamate transporter GLT1.

Ketamine appears associated with better word recall than etomidate after a course of 6 electroconvulsive therapies

Ten patients treated with electroconvulsive therapy (ECT) for depressive illness received anesthesia with either etomidate or ketamine. Three patients received both etomidate and ketamine anesthesia for ECT during separate episodes of depression. Patients anesthetized with ketamine for ECT had significantly less impairment of short-term memory function than did patients who received ECT with etomidate anesthesia. All patients who received both anesthetics for ECT during 2 different episodes had less memory loss during ECT with ketamine than with etomidate. These results show the importance of studying the effects of all anesthetic agents used during ECT on cognitive functions. The results imply that the effect of ECT on memory may be largely caused by effects mediated by glutamate at N-methyl-d-aspartate receptors and suggest that N-methyl-d-aspartate antagonists may offer protection from memory dysfunction during ECT.

Repeated electroconvulsive stimuli increase brain-derived neurotrophic factor in ACTH-treated rats

Electroconvulsive therapy is considered to be an effective treatment for severe depression. We have already shown that the antidepressant-like effects of tricyclic antidepressants in the rat forced swim test are blocked by repeated treatment with adrenocorticotropic hormone (ACTH). In the present study, we investigated the effect of repeated electroconvulsive stimuli on the forced swim test and on brain-derived neurotrophic factor (BDNF) protein levels in ACTH-treated rats. Electroconvulsive stimuli (50 mA, 0.2 s) was administered 30 min after ACTH treatment (100 microg/rat, s.c.) once daily for 14 days. In both saline and ACTH-treated rats, repeated electroconvulsive stimuli for 6 or 14 days decreased the immobility time in the forced swim test and increased the BDNF protein levels in the hippocampus. However, repeated imipramine administration (10 mg/kg, i.p. for 14 days) had no effect on the hippocampus BDNF protein levels in ACTH-treated rats. These results suggest that electroconvulsive stimuli has decreasing effects of immobility time in the forced swim test in the tricyclic antidepressant-resistant depressive model of rats induced by repeated ACTH treatment, and that increased BDNF may be involved in this phenomenon.

Ketamine pre-treatment dissociates the effects of electroconvulsive stimulation on mossy fibre sprouting and cellular proliferation in the dentate gyrus

Electroconvulsive stimulation (ECS), the experimental analogue of electroconvulsive therapy (ECT), has been shown to produce both functional and structural effects in the hippocampal formation in infrahuman species. These changes may relate to the antidepressant and cognitive effects of ECT observed in patients treated for severe depressive disorders. Recent studies have described both enhanced neurogenesis in the dentate gyrus of the hippocampus and sprouting of mossy fibre projections from granule cells. The behavioural significance of these effects remains uncertain. In this study, we examined whether ketamine, a clinically available non-competitive NMDA receptor channel blocker, could block both of these "trophic" effects. Rats were given a course of eight spaced ECS or sham treatments under either halothane or ketamine anaesthesia. The thymidine analogue bromodeoxyuridine was administered to assess the degree of hippocampal cell proliferation and mossy fibre sprouting was quantified using the Timm staining method. Pre-treatment with ketamine dissociated these effects such that mossy fibre sprouting was attenuated significantly, while cell proliferation was unaffected. This dissociation may prove useful in determining the behavioural significance of these hippocampal changes, if any, for either the antidepressant or cognitive consequences of ECT.

Electroconvulsive shock decreases binding to 5-HT2 receptors in nonhuman primates: an in vivo positron emission tomography study with [18F]setoperone

BACKGROUND

Dysfunction within the serotonin (5-HT) system plays a major role in the etiology of human depression, and treatment with antidepressant drugs downregulates 5-HT(2) receptors in rodents and humans. The consequences of another effective antidepressant treatment, electroconvulsive therapy (ECT), on 5-HT(2) receptors are less established.

METHODS

We studied the effects of a course of electroconvulsive shock (ECS) on 5-HT(2) receptor binding in nonhuman primates in vivo using positron emission tomography (PET) and the radiotracer [(18)F]setoperone. Seven adult male rhesus monkeys received two bilateral ECS treatments per week for 3 weeks; PET scans were performed before treatment, and 24 hours, 1 week, and 4-6 weeks after completion of the course of ECS. Regions of interest were placed throughout the cortex, and the data analyzed as the ratio of specific:nonspecific radioactivity accumulation, with the cerebellum used as a measure of nonspecific binding.

RESULTS

Serotonin 5-HT(2) binding was significantly decreased at 24 hours and 1 week post-ECS, but returned to baseline 4-6 weeks posttreatment.

CONCLUSIONS

These results show for the first time in a primate species that chronic ECS decreases binding to 5-HT(2) receptors and indicate that 5-HT(2) receptor downregulation may be a common effect of both pharmacologic and nonpharmacologic antidepressant treatments.

Electroconvulsive seizure treatment increases cell proliferation in rat frontal cortex

Recent studies have demonstrated increased neurogenesis in adult hippocampus in response to electroconvulsive seizure (ECS) or antidepressant drug treatment. Adult neurogenesis in the subgranular zone of the hippocampus and the subventricular zone is well established, whereas neuronal proliferation outside of these areas under unstimulated conditions is not observed. Since mood disorders are likely to involve brain regions in addition to hippocampus, particularly the frontal cortex, it is likely that antidepressant treatments produce cellular changes in these brain regions as well. In this study, we have investigated the effect of repeated ECS administration on the proliferation of cells in the frontal cortex, and we have examined the phenotype of these cells 4 weeks after labeling with a cell division marker. We found that ECS treatment increases the number of newly divided cells in the frontal cortex and that these new cells express markers of either endothelial cells or oligodendrocytes, but not neurons. It is possible that increased proliferation of these cell types in the frontal cortex could reverse the loss of glial cell number and the reduced volume that has been reported in the frontal cortex of depressed patients.

Electroconvulsive seizures regulate gene expression of distinct neurotrophic signaling pathways

Electroconvulsive therapy (ECT) remains the treatment of choice for drug-resistant patients with depressive disorders, yet the mechanism for its efficacy remains unknown. Gene transcription changes were measured in the frontal cortex and hippocampus of rats subjected to sham seizures or to 1 or 10 electroconvulsive seizures (ECS), a model of ECT. Among the 3500-4400 RNA sequences detected in each sample, ECS increased by 1.5- to 11-fold or decreased by at least 34% the expression of 120 unique genes. The hippocampus produced more than three times the number of gene changes seen in the cortex, and many hippocampal gene changes persisted with chronic ECS, unlike in the cortex. Among the 120 genes, 77 have not been reported in previous studies of ECS or seizure responses, and 39 were confirmed among 59 studied by quantitative real time PCR. Another 19 genes, 10 previously unreported, changed by <1.5-fold but with very high significance. Multiple genes were identified within distinct pathways, including the BDNF-MAP kinase-cAMP-cAMP response element-binding protein pathway (15 genes), the arachidonic acid pathway (5 genes), and more than 10 genes in each of the immediate-early gene, neurogenesis, and exercise response gene groups. Neurogenesis, neurite outgrowth, and neuronal plasticity associated with BDNF, glutamate, and cAMP-protein kinase A signaling pathways may mediate the antidepressant effects of ECT in humans. These genes, and others that increase only with chronic ECS such as neuropeptide Y and thyrotropin-releasing hormone, may provide novel ways to select drugs for the treatment of depression and mimic the rapid effectiveness of ECT.

Gene profile of electroconvulsive seizures: induction of neurotrophic and angiogenic factors

Electroconvulsive seizure therapy (ECS) is a clinically proven treatment for depression and is often effective even in patients resistant to chemical antidepressants. However, the molecular mechanisms underlying the therapeutic efficacy of ECS are not fully understood. One theory that has gained attention is that ECS and other antidepressants increase the expression of select neurotrophic factors that could reverse or block the atrophy and cell loss resulting from stress and depression. To further address this topic, we examined the expression of other neurotrophic-growth factors and related signaling pathways in the hippocampus in response to ECS using a custom growth factor microarray chip. We report the regulation of several genes that are involved in growth factor and angiogenic-endothelial signaling, including neuritin, stem cell factor, vascular endothelial growth factor (VEGF), VGF (nonacronymic), cyclooxygenase-2, and tissue inhibitor of matrix metalloproteinase-1. Some of these, as well as other growth factors identified, including VEGF, basic fibroblast growth factor, and brain-derived neurotrophic factor, have roles in mediating neurogenesis and cell proliferation in the adult brain. We also examined gene expression in the choroid plexus and found several growth factors that are enriched in this vascular tissue as well as regulated by ECS. These data suggest that an amplification of growth factor signaling combined with angiogenic mechanisms could have an important role in the molecular action of ECS. This study demonstrates the applicability of custom-focused microarray technology in addressing hypothesis-driven questions regarding the action of antidepressants.

Enhancing neuronal plasticity and cellular resilience to develop novel, improved therapeutics for difficult-to-treat depression

There is growing evidence from neuroimaging and ostmortem studies that severe mood disorders, which have traditionally been conceptualized as neurochemical disorders, are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that recent preclinical studies have shown that critical molecules in neurotrophic signaling cascades (most notably cyclic adenosine monophosphate [cAMP] response element binding protein, brain-derived neurotrophic factor, bcl-2, and mitogen activated protein [MAP] kinases) are long-term targets for antidepressant agents and antidepressant potentiating modalities. This suggests that effective treatments provide both trophic and neurochemical support, which serves to enhance and maintainnormal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal affective functioning. For many refractory patients, drugs mimicking "traditional" strategies, which directly or indirectly alter monoaminergic levels, may be of limited benefit. Newer "plasticity enhancing" strategies that may have utility in the treatment of refractory depression include N-methyl-D-aspartate antagonists, alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) potentiators, cAMP phosphodiesterase inhibitors, and glucocorticoid receptor antagonists. Small-molecule agents that regulate the activity f growth factors, MAP kinases cascades, and the bcl-2 family of proteins are also promising future avenues. The development of novel, nonaminergic-based therapeutics holds much promise for improved treatment of severe, refractory mood disorders.

Electroconvulsive stimuli alter the regional concentrations of nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in adult rat brain

In this study we investigated whether electroconvulsive stimuli (ECS) altered the regional brain protein concentrations of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial cell line-derived neurotrophic factor (GDNF) in Sprague Dawley rats. Electroconvulsive stimuli were administered once daily for 8 days. At the end of the experiment, rats were killed, the brains were dissected into five regions, and the neurotrophic factors were extracted and measured by enzyme-linked immunosorbent assay. Electroconvulsive stimuli increased the concentrations of NGF in the frontal cortex and concentrations of BDNF in the hippocampus, the striatum, and the occipital cortex. In contrast, ECS decreased GDNF concentrations in the hippocampus and the striatum. Our data indicate that neurotrophic factors play a role in the mechanism of action of ECS and, by extrapolation, may play a role in the mechanism of action of electroconvulsive treatment.