Electroconvulsive stimulations prevent stress-induced morphological changes in the hippocampus

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.

Amygdala and hippocampal substructure volumes and their association with improvement in mood symptoms in patients with mood disorders undergoing electroconvulsive therapy

Electroconvulsive therapy (ECT) demonstrates favorable outcomes in the management of severe depressive disorders. ECT has been consistently associated with volumetric increases in the amygdala and hippocampus. However, the underlying mechanisms of these structural changes and their association to clinical improvement remains unclear. In this cross-sectional structural MRI study, we assessed the difference in amygdala subnuclei and hippocampus subfields in n = 37 patients with either unipolar or bipolar disorder immediately after eighth ECT sessions compared to (n = 40) demographically matched patients in partial remission who did not receive ECT (NoECT group). Relative to NoECT, the ECT group showed significantly larger bilateral amygdala volumes post-treatment, with the effect originating from the lateral, basal, and paralaminar nuclei and the left corticoamydaloid transition area. No significant group differences were observed for the hippocampal or cortical volumes. ECT was associated with a significant decrease in depressive symptoms. However, there were no significant correlations between amygdala subnuclei volumes and symptom improvement. Our study corroborates previous reports on increased amygdalae volumes following ECT and further identifies the subnuclei driving this effect. However, the therapeutic effect of ECT does not seem to be directly related to structural changes in the amygdala.

Neural correlates of episodic memory decline following electroconvulsive therapy: An exploratory functional magnetic resonance imaging study

BACKGROUND

Electroconvulsive therapy (ECT) is an efficient and rapid-acting treatment indicated for severe depressive disorders. While ECT is commonly accompanied by transient memory decline, the brain mechanisms underlying these side effects remain unclear.

AIMS

In this exploratory functional magnetic resonance (fMRI) study, we aimed to compare effects of ECT versus pharmacological treatment on neural response during episodic memory encoding in patients with affective disorders.

METHODS

This study included 32 ECT-treated patients (major depressive disorder (MDD), n = 23; bipolar depression, n = 9) and 40 partially remitted patients in pharmacological treatment (MDD, n = 24; bipolar disorder, n = 16). Participants underwent neuropsychological assessment, a strategic picture encoding fMRI scan paradigm, and mood rating. The ECT group was assessed before ECT (pre-ECT) and 3 days after their eighth ECT session (post-ECT).

RESULTS

Groups were comparable on age, gender, and educational years (ps ⩾ 0.05). Within-group analyses revealed a selective reduction in verbal learning and episodic memory pre- to post-ECT (p = 0.012) but no decline in global cognitive performance (p = 0.3). Functional magnetic resonance imaging analyses adjusted for mood symptoms revealed greater activity in ECT-treated patients than pharmacologically treated No-ECT patients across left precentral gyrus (PCG), right dorsomedial prefrontal cortex (dmPFC), and left middle frontal gyrus (MFG). In ECT-treated patients, greater decline in verbal learning and memory performance from pre- to post-ECT correlated with higher PCG response (r = -0.46, p = 0.008), but not with dmPFC or MFG activity (ps ⩾ 0.1), post-ECT.

CONCLUSIONS

Episodic memory decline was related to greater neural activity in the left PCG, but unrelated to increased dmPFC and MFG activity, immediately after ECT.

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.

Targeting the Endoplasmic Reticulum Stress-Linked PERK/GRP78/CHOP Pathway with Magnesium Sulfate Attenuates Chronic-Restraint-Stress-Induced Depression-like Neuropathology in Rats

Magnesium sulfate has demonstrated marked neuroprotection in eclampsia, hypoxia, stroke, and post-traumatic brain injury rodent models. However, its potential impact against chronic-restraint-stress (CRS)-induced depression-like neuropathology and associated alterations in endoplasmic reticulum (ER) stress have not been adequately examined. The present study aimed to investigate the neuroprotective potential of magnesium sulfate in a rat model of CRS-triggered depression-like behavioral disturbance and the underlying molecular mechanisms. Herein, CRS was induced by placing rats into restraining tubes for 6 h/day for 21 days and the animals were intraperitoneally injected with magnesium sulfate (100 mg/kg/day) during the study period. After stress cessation, the depression-like behavior was examined by the open-field test, sucrose preference test, and forced swimming test. The present data demonstrated that CRS triggered typical depression-like behavioral changes which were confirmed by the Z-normalization scores. Mechanistically, serum circulating corticosterone levels spiked, and the hippocampi of CRS-exposed animals demonstrated a significant decline in serotonin, norepinephrine, and dopamine neurotransmitters. At the molecular level, the hippocampal pro-inflammatory TNF-alpha and IL-1β cytokines and the oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-HG) increased in stressed animals. In tandem, enhancement of hippocampal ER stress was evidenced by the activation of iNOS/PERK/GRP78/CHOP axis seen by increased protein expression of iNOS, PERK, GRP78, and CHOP signal proteins in the hippocampi of stressed rats. Interestingly, magnesium sulfate administration attenuated the depression-like behavioral outcomes and the histopathological changes in the brain hippocampi. These favorable actions were driven by magnesium sulfate's counteraction of corticosterone spike, and hippocampal neurotransmitter decline, alongside the attenuation of neuroinflammation, pro-oxidation, and ER stress. In conclusion, the current results suggest the promising neuroprotective/antidepressant actions of magnesium sulfate in CRS by dampening inflammation, ER stress, and the associated PERK/GRP78/CHOP pathway.

Cardiovascular Effects of High-Frequency Magnetic Seizure Therapy Compared With Electroconvulsive Therapy

BACKGROUND

Magnetic seizure therapy (MST) is a novel convulsive therapy that has been shown to have antidepressant efficacy comparable to electroconvulsive therapy (ECT) with fewer cognitive side effects. However, the cardiovascular (CVS) effects of high frequency MST in comparison to ECT have not been investigated.

MATERIALS AND METHODS

Forty-five patients with depression received 6 treatment sessions of 100 Hz MST versus 6 bifrontal ECT treatments in a nonrandomized comparative clinical design. Data on CVS function including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and rate pressure product (RPP) were collected at baseline (T0), after the induction of anesthesia but before the electrical stimulation (T1), during convulsion (T2), 2 minutes after cessation of motor seizure (T3), 5 minutes after cessation of motor seizure (T4), and 10 minutes after cessation of motor seizure (T5). Comparisons were made with baseline data and between MST and ECT groups.

RESULTS

There were statistically significant elevations in the maximum HR, SBP, DBP, and RPP in patients receiving ECT compared with MST both in the initial and sixth treatments (all P < 0.05). Particularly, at T2, the ECT group had significantly higher HR, SBP, DBP, and RPP than those in MST group both in initial and sixth treatment (all P < 0.001). At the sixth treatment, the ECT group had significantly higher SBP, DBP, and RPP during the treatment than in the MST group (all P < 0.001).

LIMITATIONS

The anesthetic choices for this study may limit the generalizability of our findings. The sample size was relatively small.

CONCLUSIONS

Compared with ECT, high-frequency MST has fewer CVS side effects and may be a safer option for depression patients with CVS disorders.

Lentiviral delivery of human erythropoietin attenuates hippocampal atrophy and improves cognition in the R6/2 mouse model of Huntington's disease

Huntington's disease (HD) is an incurable neurodegenerative disorder caused by a trinucleotide (CAG) repeat expansion in the huntingtin gene (HTT). The R6/2 transgenic mouse model of HD expresses exon 1 of the human HTT gene with approximately 150 CAG repeats. R6/2 mice develop progressive behavioural abnormalities, impaired neurogenesis, and atrophy of several brain regions. In recent years, erythropoietin (EPO) has been shown to confer neuroprotection and enhance neurogenesis, rendering it a promising molecule to attenuate HD symptoms. In this study, the therapeutic potential of EPO was evaluated in female R6/2 transgenic mice. A single bilateral injection of a lentivirus encoding human EPO (LV-hEPO) was performed into the lateral ventricles of R6/2 mice at disease onset (8 weeks of age). Control groups were either untreated or injected with a lentivirus encoding green fluorescent protein (LV-GFP). Thirty days after virus administration, hEPO mRNA and protein were present in injected R6/2 brains. Compared to control R6/2 mice, LV-hEPO-treated R6/2 mice exhibited reduced hippocampal atrophy, increased neuroblast branching towards the dentate granular cell layer, and improved spatial cognition. Our results suggest that LV-hEPO administration may be a promising strategy to reduce cognitive impairment in HD.

Impact of pretreatment interhemispheric hippocampal asymmetry on improvement in verbal learning following erythropoietin treatment in mood disorders: a randomized controlled trial

BACKGROUND

Treatment development that targets cognitive impairment is hampered by a lack of biomarkers that can predict treatment efficacy. Erythropoietin (EPO) improves verbal learning and memory in mood disorders, and this scales with an increase in left hippocampal volume. This study investigated whether pretreatment left hippocampal volume, interhemisphere hippocampal asymmetry or both influenced EPO treatment response with respect to verbal learning.

METHODS

Data were available for 76 of 83 patients with mood disorders from our previous EPO trials (EPO = 37 patients; placebo = 39 patients). We performed cortical reconstruction and volumetric segmentation using FreeSurfer. We conducted multiple linear regression and logistic regression to assess the influence of left hippocampal volume and hippocampal asymmetry on EPO-related memory improvement, as reflected by change in Rey Auditory Verbal Learning Test total recall from baseline to post-treatment. We set up a corresponding exploratory general linear model in FreeSurfer to assess the influence of prefrontal cortex volume on verbal learning improvement, controlling for age, sex and total intracranial volume.

RESULTS

At baseline, more rightward (left < right) hippocampal asymmetry — but not left hippocampal volume per se — was associated with greater effects of EPO versus placebo on verbal learning (p ≤ 0.05). Exploratory analysis indicated that a larger left precentral gyrus surface area was also associated with improvement of verbal learning in the EPO group compared to the placebo group (p = 0.002).

LIMITATIONS

This was a secondary analysis of our original EPO trials.

CONCLUSION

Rightward hippocampal asymmetry may convey a positive effect of EPO treatment efficacy on verbal learning.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov NCT00916552

The effect of erythropoietin on electroconvulsive stimulation induced cognitive impairment in rats

Electroconvulsive therapy (ECT) is the most effective and fast-acting treatment for severe depression but associated with troublesome cognitive side-effects. Systemically administered erythropoietin (EPO) crosses the blood-brain-barrier and is a promising treatment for cognitive dysfunction in a wide array of neuropsychiatric and neurological disorders. In this study we trained rats to locate a submerged platform in a water maze and then subjected them to electroconvulsive stimulations (ECS, the rodent equivalent to ECT) and EPO treatment. We then analysed their ability to remember and relearn the location of the platform. In addition, we examined "wall-clinging" (thigmotaxis), a behavioural indicator of stress. ECS caused significant deficit in a probe trial administered after three weeks (nine stimulations) as well as one week (six stimulations) of treatment, indicative of induction of retrograde amnesia. ECS had no effect on relearning of the water maze task or performance in a subsequent probe trial. EPO treatment did not ameliorate the ECS-induced retrograde amnesia, but after nine ECS stimulations the animals that had received EPO relearned the position of the hidden platform faster than the animals that had not. We also found EPO to decrease "wall-clinging" behaviour, suggesting an effect of EPO on the stress response in rats. Thus, we establish the Morris Water Maze as a suitable model for ECS-induced memory loss in rats and provide some evidence for potential beneficial effects of EPO.

Markers of HPA-axis activity and nucleic acid damage from oxidation after electroconvulsive stimulations in rats

OBJECTIVE

Oxidative stress has been suggested to increase after electroconvulsive therapy (ECT), a treatment which continues to be the most effective for severe depression. Oxidative stress could potentially be mechanistically involved in both the therapeutic effects and side effects of ECT.

METHODS

We measured sensitive markers of systemic and central nervous system (CNS) oxidative stress on DNA and RNA (urinary 8-oxodG/8-oxoGuo, cerebrospinal fluid 8-oxoGuo, and brain oxoguanine glycosylase mRNA expression) in male rats subjected to electroconvulsive stimulations (ECS), an animal model of ECT. Due to the previous observations that link hypothalamic-pituitary-adrenal (HPA)-axis activity and age to DNA/RNA damage from oxidation, groups of young and middle-aged male animals were included, and markers of HPA-axis activity were measured.

RESULTS

ECS induced weight loss, increased corticosterone (only in middle-aged animals), and decreased cerebral glucocorticoid receptor mRNA expression, while largely leaving the markers of systemic and CNS DNA/RNA damage from oxidation unaltered.

CONCLUSION

These results suggest that ECS is not associated with any lasting effects on oxidative stress on nucleic acids neither in young nor middle-aged rats.

Structural changes in the hippocampus as a biomarker for cognitive improvements in neuropsychiatric disorders: A systematic review

Cognitive impairments are a core feature of several neuropsychiatric disorders. A common biomarker for pro-cognitive effects may provide a much-needed tool to select amongst candidate treatments targeting cognition. The hippocampus is a promising biomarker for target-engagement due to the illness-associated morphological hippocampal changes across unipolar disorder (UD), bipolar disorder (BD) and schizophrenia (SCZ). Following the PRISMA guidelines, we searched PubMed and Embase, for clinical trials targeting cognition across neuropsychiatric disorders, with longitudinal structural magnetic resonance imaging (MRI) measures of the hippocampus. Five randomized and three open-label trials were included. Hippocampal volume increases were associated with treatment-related cognitive improvement following treatment with erythropoietin across UD, BD and SCZ, lithium treatment in BD and aerobic exercise in SCZ. Conversely, an exercise intervention in UD showed no effect on hippocampal volume or cognition. Together, these observations point to hippocampal volume change as a putative biomarker-model for cognitive improvement. Future cognition trials are encouraged to include MRI assessments pre- and post-treatment to assess the validity of hippocampal changes as a biomarker for pro-cognitive effects.

Electroconvulsive treatment prevents chronic restraint stress-induced atrophy of the hippocampal formation-A stereological study

INTRODUCTION

Electroconvulsive therapy (ECT) is one of the most efficient treatments of major depressive disorder (MDD), although the underlying neurobiology remains poorly understood. There is evidence that ECT and MDD exert opposing effects on the hippocampal formation with respect to volume and number of neurons. However, there has been a paucity of quantitative data in experimental models of ECT and MDD.

METHODS

Using design-based stereology, we have measured the effects of a stress-induced depression model (chronic restraint stress, CRS) and ECS on the morphology of the hippocampus by estimating the volume and total number of neurons in the hilus, CA1, and CA2/3, as well as in the entire hippocampus.

RESULTS

We find that CRS induces a significant decrease in volume exclusively of the hilus and that ECS (CRS + ECS) blocks this reduction. Furthermore, ECS alone does not change the volume or total number of neurons in the entire hippocampus or any hippocampal subdivision in our rat model.

Electro convulsive therapy: Modification of its effect on the autonomic nervous system using anti-cholinergic drugs

The antidepressant efficacy of electroconvulsive therapy (ECT) is correlated to the quality of the seizure as measured by EEG but has also been linked to the magnitude of changes in hemodynamic variables. Muscarinic receptor antagonists are frequently used in the treatment, and are known to affect the hemodynamic response. We hypothesized that atropine and glycopyrrolate alter the hemodynamic and autonomic hormonal response to ECT. In a randomized, cross-over study design 23 patients received either atropine, glycopyrrolate or placebo before ECT. Hemodynamic variable, EEG and EMG, and blood adrenaline, noradrenaline and pancreatic polypeptide was determined. No geriatric patients were included. Hemodynamic changes with ECT can be divided into three phases: Drop in blood pressure and pulse rate in 1st post-stimulus phase was less when using 1 mg atropine. In 2nd post-stimulus phase atropine gave a higher systolic blood pressure. No differences were seen in hormone levels after ECT in the three interventions. A significant longer tonic clonic seizure was seen in the glycopyrrolate group and a tendency of the same was seen with atropine. The study found that the changes in hemodynamic variables induced by ECT can be altered by concomitant administration of muscarinic receptor antagonist.

Electroconvulsive seizures influence dendritic spine morphology and BDNF expression in a neuroendocrine model of depression

BACKGROUND

Electroconvulsive therapy (ECT) is a rapid and effective treatment for major depressive disorder. Chronic stress-induced depression causes dendrite atrophy and deficiencies in brain-derived neurotrophic factor (BDNF), which are reversed by anti-depressant drugs. Electroconvulsive seizures (ECS), an animal model of ECT, robustly increase BDNF expression and stimulate dendritic outgrowth.

OBJECTIVE

The present study aims to understand cellular and molecular plasticity mechanisms contributing to the efficacy of ECS following chronic stress-induced depression.

METHODS

We quantify Bdnf transcript levels and dendritic spine density and morphology on cortical pyramidal neurons in mice exposed to vehicle or corticosterone and receiving either Sham or ECS treatment.

RESULTS

ECS rescues corticosterone-induced defects in spine morphology and elevates Bdnf exon 1 and exon 4-containing transcripts in cortex.

CONCLUSIONS

Dendritic spine remodeling and induction of activity-induced BDNF in the cortex represent important cellular and molecular plasticity mechanisms underlying the efficacy of ECS for treatment of chronic stress-induced depression.

Erythropoietin prevents the effect of chronic restraint stress on the number of hippocampal CA3c dendritic terminals-relation to expression of genes involved in synaptic plasticity, angiogenesis, inflammation, and oxidative stress in male rats

Stress-induced allostatic load affects a variety of biological processes including synaptic plasticity, angiogenesis, oxidative stress, and inflammation in the brain, especially in the hippocampus. Erythropoietin (EPO) is a pleiotropic cytokine that has shown promising neuroprotective effects. Recombinant human EPO is currently highlighted as a new candidate treatment for cognitive impairment in neuropsychiatric disorders. Because EPO enhances synaptic plasticity, attenuates oxidative stress, and inhibits generation of proinflammatory cytokines, EPO may be able to modulate the effects of stress-induced allostatic load at the molecular level. The aim of this study was therefore to investigate how EPO and repeated restraint stress, separately and combined, influence (i) behavior in the novelty-suppressed feeding test of depression/anxiety-related behavior; (ii) mRNA levels of genes encoding proteins involved in synaptic plasticity, angiogenesis, oxidative stress, and inflammation; and (iii) remodeling of the dendritic structure of the CA3c area of the hippocampus in male rats. As expected, chronic restraint stress lowered the number of CA3c apical dendritic terminals, and EPO treatment reversed this effect. Interestingly, these effects seemed to be mechanistically distinct, as stress and EPO had differential effects on gene expression. While chronic restraint stress lowered the expression of spinophilin, tumor necrosis factor α, and heat shock protein 72, EPO increased expression of hypoxia-inducible factor-2α and lowered the expression of vascular endothelial growth factor in hippocampus. These findings indicate that the effects of treatment with EPO follow different molecular pathways and do not directly counteract the effects of stress in the hippocampus.

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.

A chronic increase of corticosterone age-dependently reduces systemic DNA damage from oxidation in rats

Stress and depression are associated with an acceleration of brain and bodily aging; effects which have been attributed to chronic elevations of glucocorticoids. We tested the hypothesis that a three week administration of stress-associated levels of corticosterone (CORT, the principal rodent glucocorticoid) would increase systemic and CNS DNA and RNA damage from oxidation; a phenomenon known to be centrally involved in the aging process. We also hypothesized that older individuals would be more sensitive to this effect and that the chronic CORT administration would exacerbate age-related memory decline. Young and old male Sprague-Dawley rats were non-invasively administered CORT by voluntary ingestion of nut paste containing either CORT (25mg/kg) or vehicle for a total of 22 days. CORT increased the 24h urinary excretion of the hormone to the levels previously observed after experimental psychological stress and caused a downregulation of the glucocorticoid receptor in the CA1 area of the hippocampus. Contrary to our hypothesis, 24h excretion of 8-oxodG/8-oxoGuo (markers of DNA/RNA damage from oxidation) was reduced in CORT-treated young animals, whereas old animals showed no significant differences. In old animals, CORT caused a borderline significant reduction of RNA oxidation in CNS, which was paralleled by a normalization of performance in an object location memory test. To our knowledge, this is the first demonstration that chronic stress-associated levels of CORT can reduce nucleic acid damage from oxidation. These findings contradict the notion of elevated CORT as a mediator of the accelerated aging observed in stress and depression.

Chronic stress and hippocampal dendritic complexity: Methodological and functional considerations

The current understanding of how chronic stress impacts hippocampal dendritic arbor complexity and the subsequent relationship to hippocampal-dependent spatial memory is reviewed. A surge in reports investigating hippocampal dendritic morphology is occurring, but with wide variations in methodological detail being reported. Consequently, this review systematically outlines the basic neuroanatomy of relevant hippocampal features to help clarify how chronic stress or glucocorticoids impact hippocampal dendritic complexity and how these changes occur in parallel with spatial cognition. Chronic stress often leads to hippocampal CA3 apical dendritic retraction first with other hippocampal regions (CA3 basal dendrites, CA1, dentate gyrus, DG) showing dendritic retraction when chronic stress is sufficiently robust or long lasting. The stress-induced reduction in hippocampal CA3 apical dendritic arbor complexity often coincides with impaired hippocampal function, such as spatial learning and memory. Yet, when chronic stress ends and a post-stress recovery period ensues, the atrophied dendritic arbors and poor spatial abilities often improve. However, this process differs from a simple reversal of chronic stress-induced deficits. Recent reports suggest that this return to baseline-like functioning is uniquely different from non-stressed controls, emphasizing the need for further studies to enhance our understanding of how a history of stress subsequently alters an organism's spatial abilities. To provide a consistent framework for future studies, this review concludes with an outline for a quick and easy reference on points to consider when planning chronic stress studies with the goal of measuring hippocampal dendritic complexity and spatial ability.

Regional brain volumes, diffusivity, and metabolite changes after electroconvulsive therapy for severe depression

OBJECTIVE

To investigate the role of hippocampal plasticity in the antidepressant effect of electroconvulsive therapy (ECT).

METHOD

We used magnetic resonance (MR) imaging including diffusion tensor imaging (DTI) and proton MR spectroscopy (¹ H-MRS) to investigate hippocampal volume, diffusivity, and metabolite changes in 19 patients receiving ECT for severe depression. Other regions of interest included the amygdala, dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex, and hypothalamus. Patients received a 3T MR scan before ECT (TP1), 1 week (TP2), and 4 weeks (TP3) after ECT.

RESULTS

Hippocampal and amygdala volume increased significantly at TP2 and continued to be increased at TP3. DLPFC exhibited a transient volume reduction at TP2. DTI revealed a reduced anisotropy and diffusivity of the hippocampus at TP2. We found no significant post-ECT changes in brain metabolite concentrations, and we were unable to identify a spectral signature at ≈1.30 ppm previously suggested to reflect neurogenesis induced by ECT. None of the brain imaging measures correlated to the clinical response.

CONCLUSION

Our findings show that ECT causes a remodeling of brain structures involved in affective regulation, but due to their lack of correlation with the antidepressant effect, this remodeling does not appear to be directly underlying the antidepressant action of ECT.

Effects of Erythropoietin on Hippocampal Volume and Memory in Mood Disorders

BACKGROUND

Persistent cognitive dysfunction in depression and bipolar disorder (BD) impedes patients' functional recovery. Erythropoietin (EPO) increases neuroplasticity and reduces cognitive difficulties in treatment-resistant depression (TRD) and remitted BD. This magnetic resonance imaging study assessed the neuroanatomical basis for these effects.

METHODS

Patients with TRD who were moderately depressed or BD in partial remission were randomized to 8 weekly EPO (40,000 IU) or saline infusions in a double-blind, parallel-group design. Patients underwent magnetic resonance imaging, memory assessment with the Rey Auditory Verbal Learning Test, and mood ratings with the Beck Depression Inventory, Hamilton Depression Rating Scale, and Young Mania Rating Scale at baseline and week 14. Hippocampus segmentation and analysis of hippocampal volume, shape, and gray matter density were conducted with FMRIB Software Library tools. Memory change was analyzed with repeated-measures analysis of covariance adjusted for depression symptoms, diagnosis, age, and gender.

RESULTS

Eighty-four patients were randomized; 1 patient withdrew and data collection was incomplete for 14 patients; data were thus analyzed for 69 patients (EPO: n = 35, saline: n = 34). Compared with saline, EPO was associated with mood-independent memory improvement and reversal of brain matter loss in the left hippocampal cornu ammonis 1 to cornu ammonis 3 and subiculum. Using the entire sample, memory improvement was associated with subfield hippocampal volume increase independent of mood change.

CONCLUSIONS

EPO-associated memory improvement in TRD and BD may be mediated by reversal of brain matter loss in a subfield of the left hippocampus. EPO may provide a therapeutic option for patients with mood disorders who have impaired neuroplasticity and cognition.

Potential roles for Homer1 and Spinophilin in the preventive effect of electroconvulsive seizures on stress-induced CA3c dendritic retraction in the hippocampus

Electroconvulsive therapy (ECT) remains the treatment of choice for patients with severe or drug-resistant depressive disorders, yet the mechanism behind its efficacy remains poorly characterized. In the present study, we used electroconvulsive seizures (ECS), an animal model of ECT, to identify proteins possibly involved in the preventive effect of ECS on stress-induced neuronal atrophy in the hippocampus. Rats were stressed daily using the 21-day 6h daily restraint stress paradigm and subjected to sham seizures, a single ECS on the last day of the restraint period or daily repeated seizures for 10 consecutive days during the end of the restraint period. Consistent with previous findings, dendritic atrophy was observed in the CA3c hippocampal region of chronically stressed rats. In addition, we confirmed our recent findings of increased spine density in the CA1 region following chronic restraint stress. The morphological alterations in the CA3c area were prevented by treatment with ECS. On the molecular level, we showed that the synaptic proteins Homer1 and Spinophilin are targeted by ECS. Repeated ECS blocked stress-induced up-regulation of Spinophilin protein levels and further increased the stress-induced up-regulation of Homer1. Given the roles of Spinophilin in the regulation of AMPA receptors and Homer1 in the regulation of metabotropic glutamate receptors (mGluRs), our data imply the existence of a mechanism where ECS regulate cell excitability by modulating AMPA receptor function and mGluR related calcium homeostasis. These molecular changes could potentially contribute to the mechanism induced by ECS which prevents the stress-induced morphological changes in the CA3c region.

Electroconvulsive therapy as a treatment for protracted refractory delirium in the intensive care unit--five cases and a review

PURPOSE

Delirium in the intensive care unit (ICU) is conventionally treated pharmacologically but can progress into a protracted state refractory to medical treatment--a potentially life-threatening condition in itself.

METHODS

We treated 5 cases of severe protracted delirium in our ICU with electroconvulsive therapy (ECT) after failure of conventional medical therapy.

RESULTS

The delirious state of long standing agitation, anxiety, and discomfort was controlled in all patients. Electroconvulsive therapy was effective in controlling delirium in 4 patients. The last patient became calm, relieved of stress, and able to cooperate with the ventilator but remained in a state of posttraumatic amnesia after a head trauma.

CONCLUSION

Although controversial, ECT is nevertheless recognized as an efficient and safe treatment for various psychiatric illnesses including delirium. Considering the significantly increased mortality and severe cognitive decline associated with delirium in the ICU, we find ECT to be a valuable treatment option for this vulnerable patient population. It can be considered when agitation cannot be controlled with medical treatment, when agitation and delirium make weaning impossible, or prolonged deep sedation the only alternative.

Effects of fluoxetine on CRF and CRF1 expression in rats exposed to the learned helplessness paradigm

RATIONALE

Stress is a common antecedent reported by people suffering major depression. In these patients, extrahypothalamic brain areas, like the hippocampus and basolateral amygdala (BLA), have been found to be affected. The BLA synthesizes CRF, a mediator of the stress response, and projects to hippocampus. The main hippocampal target for this peptide is the CRF subtype 1 receptor (CRF1). Evidence points to a relationship between dysregulation of CRF/CRF1 extrahypothalamic signaling and depression.

OBJECTIVE

Because selective serotonin reuptake inhibitors (SSRIs) are the first-line pharmacological treatment for depression, we investigated the effect of chronic treatment with the SSRI fluoxetine on long-term changes in CRF/CRF1 signaling in animals showing a depressive-like behavior.

METHODS

Male Wistar rats were exposed to the learned helplessness paradigm (LH). After evaluation of behavioral impairment, the animals were treated with fluoxetine (10 mg/kg i.p.) or saline for 21 days. We measured BLA CRF expression with RT-PCR and CRF1 expression in CA3 and the dentate gyrus of the hippocampus with in situ hybridization. We also studied the activation of one of CRF1's major intracellular signaling targets, the extracellular signal-related kinases 1 and 2 (ERK1/2) in CA3.

RESULTS

In saline-treated LH animals, CRF expression in the BLA increased, while hippocampal CRF1 expression and ERK1/2 activation decreased. Treatment with fluoxetine reversed the changes in CRF and CRF1 expressions, but not in ERK1/2 activation.

CONCLUSION

In animals exposed to the learned helplessness paradigm, there are long-term changes in CRF and CRF1 expression that are restored with a behaviorally effective antidepressant treatment.

Chronic restraint stress in rats causes sustained increase in urinary corticosterone excretion without affecting cerebral or systemic oxidatively generated DNA/RNA damage

Increased oxidatively generated damage to nucleic acids (DNA/RNA) may be a common mechanism underlying accelerated aging in psychological stress states and mental disorders. In the present study, we measured the urinary excretion of corticosterone and markers of systemic oxidative stress on nucleic acids, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo), respectively, in rats subjected to chronic restraint stress. To reliably collect 24h urine samples, the full 3-week restraint stress paradigm was performed in metabolism cages. We further determined frontal cortex and hippocampal levels of oxidatively generated nuclear DNA damage, as measured by oxoguanine DNA glycosylase and formamidopyrimidine DNA glycosylase sensitive sites detected by the comet assay, as well as the expression of genes involved in DNA repair (Ogg1 and Nudt1) and inflammation (Ccl2 and Tnf). The metabolism cage housing in itself did not significantly influence a range of biological stress markers. In the restraint stress group, there was a sustained 2.5 fold increase in 24h corticosterone excretion from day 2 after stress initiation. However, neither whole-body nor cerebral measures of nucleic acid damage from oxidation were affected by stress. In contrast, cerebral DNA repair enzymes exhibited a general trend towards an induction, which was significant for hippocampal Nudt1. The results and their implications for stress sensitivity and resilience are discussed.

Remodeling of axo-spinous synapses in the pathophysiology and treatment of depression

Dendritic spines provide a compartment for assembly and functional organization of synaptic machinery that plays a fundamental role in neuronal communication and neuroplasticity. Studies in humans as well as in animal models have demonstrated abnormal spine architecture in several psychiatric disorders, including depression and other stress-related illnesses. The negative impact of stress on the density and organization of spines is thought to contribute to the behavioral deficits caused by stress exposure. Moreover, there is now evidence that medication-induced recovery involves changes in synaptic plasticity and dendrite morphology, including increased expression of pre- and postsynaptic plasticity-related proteins, as well as the density and function of axo-spinous synapses. Here we review the evidence from brain imaging and postmortem studies demonstrating that depression is accompanied by structural and functional alterations of cortical and limbic brain regions, including the prefrontal cortex, hippocampus and amygdala. In addition, we present more direct evidence from basic research studies that exposure to stress alters spine morphology, function and plasticity and that antidepressants, particularly new rapid acting agents, reverse these effects. Elucidation of the signaling pathways and molecular mechanisms that control spine synapse assembly and plasticity will contribute to a better understanding of the pathophysiology of depression and development of novel, more effective therapeutic agents.

Wistar rats subjected to chronic restraint stress display increased hippocampal spine density paralleled by increased expression levels of synaptic scaffolding proteins

The aim of this study was to investigate whether the previously reported effect of chronic restraint stress (CRS) on hippocampal neuron morphology and spine density is paralleled by a similar change in the expression levels of synaptic scaffolding proteins. Adult male Wistar rats were subjected either to CRS (6 h/day) for 21 days or to control conditions. The resulting brains were divided and one hemisphere was impregnated with Golgi-Cox before coronal sectioning and autometallographic development. Neurons from CA1, CA3b, CA3c, and dentate gyrus (DG) area were reconstructed and subjected to Sholl analysis and spine density estimation. The contralateral hippocampus was used for quantitative real-time polymerase chain reaction and protein analysis of genes associated with spine density and morphology (the synaptic scaffolding proteins: Spinophilin, Homer1-3, and Shank1-3). In the CA3c area, CRS decreased the number of apical dendrites and their total length, whereas CA1 and DG spine density were significantly increased. Analysis of the contralateral hippocampal homogenate displayed an increased gene expression of Spinophilin, Homer1, Shank1, and Shank2 and increased protein expression of Spinophilin and Homer1 in the CRS animals. In conclusion, CRS influences hippocampal neuroplasticity by modulation of dendrite branching pattern and spine density paralleled by increased expression levels of synaptic scaffolding proteins.

Electroconvulsive stimulations prevent chronic stress-induced increases in L-type calcium channel mRNAs in the hippocampus and basolateral amygdala

Although affective disorders have high prevalence, morbidity and mortality, we do not fully understand disease etiopathology, nor have we determined the exact mechanisms by which treatment works. Recent research indicates that intracellular calcium ion dysfunction might be involved. Here we use the chronic restraint stress model of affective disorder (6 h restraint per day for 21 days) in combination with electroconvulsive stimulations to examine the effects of stress and an effective antidepressive treatment modality on L-type voltage gated calcium channel subunit mRNA expression patterns in the brain. We find that stress tended to upregulate Ca(v)1.2 and Ca(v)1.3 channels in a brain region specific manner, while ECS tended to normalise this effect. This was more pronounced for Ca(v)1.2 channels, where stress clearly increased expression in both the basolateral amygdala, dentate gyrus and CA3, while stress only upregulated Ca(v)1.3 channel expression significantly in the dentate gyrus. ECS effects on Ca(v)1.2 channel expression were generally specific to stressed animals. Our findings are consistent with and extent previous studies on the involvement of intracellular calcium ion dysfunction in affective disorders. Selective modulation of neuronal L-type voltage gated calcium channels appears to be a promising target for the development of novel antidepressive treatment modalities.

Anterior cingulate pyramidal neurons display altered dendritic branching in depressed suicides

BACKGROUND

It is hypothesized that mood disorders are accompanied by altered wiring and plasticity in key limbic brain regions such as the anterior cingulate cortex (ACC). To test this hypothesis at the cellular level, we analyzed basilar dendritic arborizations extended by layer VI pyramidal neurons in silver-impregnated postmortem ACC samples from well-characterized depressed suicide subjects (n=12) and matched sudden-death controls (n=7).

METHODS

One cm(3) tissue blocks were stained using a Golgi preparation, cut on a microtome, and mounted on slides. Basilar dendritic arbors from 195 neurons were reconstructed, and the number, length, and diameter of branches were determined at each branch order. The size and number of spines borne by these branches were also assessed.

RESULTS

Third-order branches were significantly reduced in number (24% fewer; p=0.00262) in depressed suicides compared to controls. The size and average length of these branches, as well as their number of spines/length were unaltered. On average, for each pyramidal neuron analyzed in depressed subjects, the fewer third-order branches resulted in a significant reduction in branch length (28% shorter; p=0.00976) at this branch order.

CONCLUSIONS

These results provide the first evidence of altered cortical dendritic branching in mood disorders. Given that proximal dendritic branches grow during perinatal development, and that they are generally less plastic at maturity than distal segments, we speculate that these differences in dendritic branching may reflect a biological predisposition to depression and suicide.

Prenatal stress causes dendritic atrophy of pyramidal neurons in hippocampal CA3 region by glutamate in offspring rats

A substantial number of human epidemiological data, as well as experimental studies, suggest that adverse maternal stress during gestation is involved in abnormal behavior, mental, and cognition disorder in offspring. To explore the effect of prenatal stress (PS) on hippocampal neurons, in this study, we observed the dendritic field of pyramidal neurons in hippocampal CA3, examined the concentration of glutamate (Glu), and detected the expression of synaptotagmin-1 (Syt-1) and N-methyl-D-aspartate receptor 1 (NR1) in hippocampus of juvenile female offspring rats. Pregnant rats were divided into two groups: control group (CON) and PS group. Female offspring rats used were 30-day old. The total length of the apical dendrites of pyramidal neurons in hippocampal CA3 of offspring was significantly shorter in PS than that in CON (p < 0.01). The number of branch points of the apical dendrites of pyramidal neurons in hippocampal CA3 of offspring was significantly less in PS (p < 0.01). PS offspring had a higher concentration of hippocampal Glu compared with CON (p < 0.05). PS offspring displayed increased expression of Syt-1 and decreased NR1 in hippocampus compared with CON (p < 0.001 and p < 0.01, respectively). The expression of NR1 in different hippocampus subfields of offspring was significantly decreased in PS than that in CON (p < 0.05-0.01). This study shows that PS increases the Glu in hippocampus and causes apical dendritic atrophy of pyramidal neurons of hippocampal CA3 in offspring rats. The decline of NR1 in hippocampus may be an adaptive response to the increased Glu.

Through the looking glass: examining neuroanatomical evidence for cellular alterations in major depression

Alterations in brain plasticity are increasingly thought to play important roles in major depressive disorder (MDD) and suicide. To gain a better understanding of the gross structural changes observed in the brains of major depressed and suicide subjects, a number of recent investigations have scrutinized the cellular integrity of brain regions implicated in mood disorders. The purpose of this review is to summarize the current knowledge on the microscopic features of neuronal and glial cell populations in these different brain regions, namely the prefrontal cortex, hippocampus, amygdala, raphe nucleus and locus coeruleus. In general, evidence from this burgeoning field supports the hypothesis of altered cell plasticity in MDD and suicide occurring mainly in key fronto-limbic areas. Interestingly, reported morphometric and cell density alterations are generally region-specific and implicate several neuromodulatory systems, notably GABAergic, serotonergic, noradrenergic and glutamatergic pathways. Cell-specific changes involve reductions in densities of astrocytes and oligodendrocytes, while increases in microglial densities have also been reported. Furthermore, increases in neuronal densities have been found in subcortical regions. The implication of such findings for our understanding of the cellular and molecular underpinnings of MDD and suicide are discussed, and the strengths and weaknesses of morphological approaches used to analyse human postmortem brain tissues are evaluated.