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

A Systematic Review of Neuromodulation Treatment Effects on Suicidality

Introduction: Neuromodulation is an important group of therapeutic modalities for neuropsychiatric disorders. Prior studies have focused on efficacy and adverse events associated with neuromodulation. Less is known regarding the influence of neuromodulation treatments on suicidality. This systematic review sought to examine the effects of various neuromodulation techniques on suicidality. Methods: A systematic review of the literature from 1940 to 2020 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline was conducted. Any reported suicide-related outcome, including suicidal ideation, suicide intent, suicide attempt, completed suicide in reports were considered as a putative measure of treatment effect on suicidality. Results: The review identified 129 relevant studies. An exploratory analysis of a randomized controlled trial comparing the effects of sertraline and transcranial direct-current stimulation (tDCS) for treating depression reported a decrease in suicidal ideation favoring tDCS vs. placebo and tDCS combined with sertraline vs. placebo. Several studies reported an association between repetitive transcranial magnetic stimulation and improvements in suicidal ideation. In 12 of the studies, suicidality was the primary outcome, ten of which showed a significant improvement in suicidal ideation. Electroconvulsive therapy (ECT) and magnetic seizure therapy was also shown to be associated with lower suicidal ideation and completed suicide rates. There were 11 studies which suicidality was the primary outcome and seven of these showed an improvement in suicidal ideation or suicide intent and fewer suicide attempts or completed suicides in patients treated with ECT. There was limited literature focused on the potential protective effect of vagal nerve stimulation with respect to suicidal ideation. Data were mixed regarding the potential effects of deep brain stimulation on suicidality. Conclusions: Future prospective studies of neuromodulation that focus on the primary outcome of suicidality are urgently needed. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=125599, identifier: CRD42019125599.

Fronto-limbic neuroimaging biomarkers for diagnosis and prediction of treatment responses in major depressive disorder

The neuroimaging is an important tool for understanding the biomarkers and predicting treatment responses in major depressive disorder (MDD). The potential biomarkers and prediction of treatment response in MDD will be addressed in the review article. The brain regions of cognitive control and emotion regulation, such as the frontal and limbic regions, might represent the potential targets for MDD biomarkers. The potential targets of frontal lobes might include anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC). For the limbic system, hippocampus and amygdala might be the potentially promising targets for MDD. The potential targets of fronto-limbic regions have been found in the studies of several major neuroimaging modalities, such as the magnetic resonance imaging, near-infrared spectroscopy, electroencephalography, positron emission tomography, and single-photon emission computed tomography. Additional regions, such as brainstem and midbrain, might also play a part in the MDD biomarkers. For the prediction of treatment response, the gray matter volumes, white matter tracts, functional representations and receptor bindings of ACC, DLPFC, OFC, amygdala, and hippocampus might play a role in the prediction of antidepressant responses in MDD. For the response prediction of psychotherapies, the fronto-limbic, reward regions, and insula will be the potential targets. For the repetitive transcranial magnetic stimulation, the DLPFC, ACC, limbic, and visuospatial regions might represent the predictive targets for treatment. The neuroimaging targets of MDD might be focused in the fronto-limbic regions. However, the neuroimaging targets for the prediction of treatment responses might be inconclusive and beyond the fronto-limbic regions.

Recent Updates on Electro-Convulsive Therapy in Patients with Depression

OBJECTIVE

Electro-convulsive therapy (ECT) has been established as a treatment modality for patients with treatment-resistant depression and with some specific subtypes of depression. This narrative review intends to provide psychiatrists with the latest findings on the use of ECT in depression, devided into total eight sub-topics.

METHODS

We searched PubMed for English-language articles using combined keywords and tried to analyze journals published from 1995-2020.

RESULTS

Pharmacotherapy such as antidepressants or maintenance ECT is more effective than a placebo as prevention of recurrence after ECT. The use of ECT in treatment-resistant depression, depressed patients with suicidal risks, elderly depression, bipolar depression, psychotic depression, and depression during pregnancy or postpartum have therapeutic benefits. As possible mechanisms of ECT, the role of neurotransmitters such as serotonin, dopamine, gamma-aminobutyric acid (GABA), and other findings in the field of neurophysiology, neuro-immunology, and neurogenesis are also supported.

CONCLUSION

ECT is evolving toward reducing cognitive side effects and maximizing therapeutic effects. If robust evidence for ECT through randomized controlled studies are more established and the mechanism of ECT gets further clarified, the scope of its use in the treatment of depression will be more expanded in the future.

Chronic fluoxetine reverses the effects of chronic corticosterone treatment on α2-adrenoceptors in the rat frontal cortex but not locus coeruleus

Disruption of the hypothalamic-pituitary-adrenal axis is an established finding in patients with anxiety and/or depression. Chronic corticosterone administration in animals has been proposed as a model for the study of these stress-related disorders and the antidepressant action. Alterations of the central noradrenergic system and specifically of inhibitory α₂-adrenoceptors seem to be part of the pathophysiology of depression and contribute to the antidepressant activity. The present study evaluates in male rats the effect of chronic corticosterone treatment during 35 days (16-20 mg kg^-1 day^-1) on the sensitivity of α₂-adrenoceptors expressed in the somatodendritic and terminal noradrenergic areas locus coeruleus (LC) and prefrontal cortex (PFC), respectively. Further, the effect of chronic fluoxetine treatment (5 mg kg^-1, i.p., since the 15th day) on the sensitivity of α₂-adrenoceptors was examined under control conditions and in corticosterone-treated rats. The α₂-adrenoceptor functionality was analysed in vitro by agonist-mediated [³⁵S]GTPγS binding stimulation and in vivo through the modulation of noradrenaline (NA) release evaluated by dual-probe microdialysis. The concentration-effect curves of the [³⁵S]GTPγS binding stimulation by the agonist UK14304 (5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine) demonstrated a desensitization of cortical α₂-adrenoceptors induced by corticosterone (-logEC₅₀ = 6.7 ± 0.2 vs 8.2 ± 0.3 in controls) that was reverted by fluoxetine treatment (-logEC₅₀ = 7.5 ± 0.3). Local administration of the α₂-adrenoceptor antagonist RS79948 ((8aR,12aS,13aS)-5,8,8a,9,10,11,12,12a,13,13a-decahydro-3-methoxy-12-(ethylsulfonyl)-6H-isoquino[2,1-g][1,6]naphthyridine) (0.1-100 μmol L^-1) into the LC induced a concentration-dependent NA increase in the PFC of the control group (E_max = 191 ± 30%) but non-significant effect was observed in corticosterone-treated rats (E_max = 133 ± 46%), reflecting a desensitization of α₂-adrenoceptors that control the firing of noradrenergic neurons. Fluoxetine treatment did not alter the corticosterone-induced desensitization in this area (E_max = 136 ± 19%). No effect of fluoxetine on α₂-adrenoceptor functionality was observed in control animals (E_max = 223 ± 30%). In PFC, the local administration of RS79948 increased NA in controls (E_max = 226 ± 27%) without effect in the corticosterone group (E_max = 115 ± 26%), suggesting a corticosterone-induced desensitization of terminal α₂-adrenoceptors. Fluoxetine administration prevented the desensitization induced by corticosterone in the PFC (E_max = 233 ± 33%) whereas desensitized α₂-adrenoceptors in control animals (E_max = -24 ± 10%). These data indicate that chronic corticosterone increases noradrenergic activity by acting at different α₂-adrenoceptor subpopulations. Treatment with the antidepressant fluoxetine seems to counteract these changes by acting mainly on presynaptic α₂-adrenoceptors expressed in terminal areas.

Cortical and striatal serotonin transporter binding in a genetic rat model of depression and in response to electroconvulsive stimuli

Depression is a debilitating mental illness and two thirds of patients respond insufficiently to conventional antidepressants. Electroconvulsive therapy (ECT) remains the most effective treatment to alleviate drug-refractory depression, however the neurobiological mechanisms are mostly unknown. The serotonergic system plays an important role in depression and alterations in the serotonin transporter (SERT) are seen both in depression and response to antidepressant pharmacotherapies. The first aim of this study was to investigate SERT density in a genetic rat model of depression, Flinders Sensitive Line (FSL), compared to control Flinders Resistant Line (FRL) and Sprague-Dawley (SD) rats. The second aim was to investigate SERT density in response to electroconvulsive stimuli (ECS), an animal model of ECT. Female rats of each strain were treated with ECS or sham (ear-clip placement with no current) for 10 days before brains were removed, frozen and cut into 20 µm thick sections. SERT density was measured in striatal and cortical regions by quantitative in vitro autoradiography using the SERT-radioligand, [³H]-DASB. Higher SERT density was observed in FSL rats compared to SD rats by 36-48% in motor cortex and striatum under sham conditions. In response to ECS, SD rats displayed a significant effect of treatment, whereas no changes were observed in FRL and FSL rats. Increased SERT binding in FSL rats compared to SD supports a dysfunction of the serotonergic system in depression. The increased SERT density after ECS, seen in SD rats but not FSL rats, suggests a different mechanism of action between depressive-like rats and controls.

Transmitter receptors reveal segregation of the arcopallium/amygdala complex in pigeons (Columba livia)

At the beginning of the 20th century it was suggested that a complex group of nuclei in the avian posterior ventral telencephalon is comparable to the mammalian amygdala. Subsequent findings, however, revealed that most of these structures share premotor characteristics, while some indeed constitute the avian amygdala. These developments resulted in 2004 in a change of nomenclature of these nuclei, which from then on were named arcopallial or amygdala nuclei and referred to as the arcopallium/amygdala complex. The structural basis for the similarities between avian and mammalian arcopallial and amygdala subregions is poorly understood. Therefore, we analyzed binding site densities for glutamatergic AMPA, NMDA and kainate, GABAergic GABA_A , muscarinic M₁ , M₂ and nicotinic acetylcholine (nACh; α₄ β₂ subtype), noradrenergic α₁ and α₂ , serotonergic 5-HT_1A and dopaminergic D_1/5 receptors using quantitative in vitro receptor autoradiography combined with a detailed analysis of the cyto- and myelo-architecture. Our approach supports a segregation of the pigeon's arcopallium/amygdala complex into the following subregions: the arcopallium anterius (AA), the arcopallium ventrale (AV), the arcopallium dorsale (AD), the arcopallium intermedium (AI), the arcopallium mediale (AM), the arcopallium posterius (AP), the nucleus posterioris amygdalopallii pars basalis (PoAb) and pars compacta (PoAc), the nucleus taeniae amgygdalae (TnA) and the area subpallialis amygdalae (SpA). Some of these subregions showed further subnuclei and each region of the arcopallium/amygdala complex are characterized by a distinct multi-receptor density expression. Here we provide a new detailed map of the pigeon's arcopallium/amygdala complex and compare the receptor architecture of the subregions to their possible mammalian counterparts.

How Electroconvulsive Therapy Works?: Understanding the Neurobiological Mechanisms

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

Effects of anti-depressant treatments on FADD and p-FADD protein in rat brain cortex: enhanced anti-apoptotic p-FADD/FADD ratio after chronic desipramine and fluoxetine administration

RATIONALE

Fas-associated death domain (FADD) is an adaptor of death receptors that can also induce anti-apoptotic actions through its phosphorylated form (p-FADD). Activation of monoamine receptors, indirect targets of classic anti-depressant drugs (ADs), reduced FADD and increased p-FADD and p-FADD/FADD ratio in brain.

OBJECTIVES

To ascertain whether ADs, which indirectly regulate monoamine receptors, modulate FADD protein forms to promote anti-apoptotic actions.

METHODS

The effects of selected norepinephrine transporter (NET), serotonin transporter (SERT), monoamine oxidase (MAO) inhibitors, atypical ADs, and electroconvulsive shock (ECS) or behavioral procedures (forced swim test, FST) on FADD forms and pro-survival FADD-like interleukin-1β-converting enzyme-inhibitory protein (FLIP-L) and phosphoprotein enriched in astrocytes of 15 kDa (p-PEA-15) contents were assessed in rat brain cortex by western blot analysis.

RESULTS

Acute NET (e.g., nisoxetine) but not SERT (e.g., fluoxetine) inhibitors decreased cortical FADD (up to 37 %) and increased p-FADD/FADD ratio (up to 1.9-fold). Nisoxetine effects were prevented by α2-antagonist RX-821002, suggesting the involvement of presynaptic α2-autoreceptors. Immobility time in the FST correlated with increases of pro-apoptotic FADD and decreases of anti-apoptotic p-FADD. The MAO-A/B inhibitor phenelzine decreased FADD (up to 33 %) and increased p-FADD (up to 65 %) and p-FADD/FADD (up to 2.4-fold). Other MAO inhibitors (clorgyline, Ro 41-1049, rasagiline), atypical ADs (ketamine and mirtazapine), or ECS did not modulate cortical FADD. Chronic (14 days) desipramine and fluoxetine, but not phenelzine, increased p-FADD (up to 59 %), p-FADD/FADD ratio (up to 1.8-fold), and pro-survival p-PEA-15 (up to 46 %) in rat brain cortex.

CONCLUSIONS

Multifunctional FADD protein, through an increased p-FADD/FADD ratio, could participate in the mechanisms of anti-apoptotic actions induced by ADs.

α2-adrenoceptor binding in Flinders-sensitive line compared with Flinders-resistant line and Sprague-Dawley rats

OBJECTIVES

Disturbances in the noradrenergic system, including alterations in the densities of α2-adrenoceptors, are posited to be involved in the pathophysiology of depression. In this study, we investigate the binding of α2-adrenoceptors in regions relevant to depression in an animal model of depression.

METHODS

Using in vitro autoradiography techniques and the selective α2-ligand, [3H]RX 821002, we investigated the density of α2-adrenoceptors in female Flinders-sensitive line (FSL) rats, a validated model of depression, and in two traditional control groups - female Flinders-resistant line (FRL) and Sprague-Dawley (SD) rats.

RESULTS

The α2-adrenoceptor density was increased in most regions of the FSL rat brain when compared with SD rats (10% across regions). Moreover, the α2-adrenoceptor density was further increased in the FRL rats compared with both FSL (10% across regions) and SD rats (24% across regions).

CONCLUSIONS

The increase in α2-adrenoceptor binding in cortical regions in the FSL strain compared with the SD control strain is in accord with α2-adrenoceptor post-mortem binding data in suicide victims with untreated major depression. However, the differences in binding observed in the two control groups were unexpected and suggest the need for further studies in a larger cohort of animals of both sexes.