Effects of repeated electroconvulsive shocks on catecholamine systems: Electrophysiological studies in the rat brain

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.

Electroconvulsive therapy in treatment resistant depression

Electroconvulsive therapy (ECT) is a treatment modality for patients with treatment resistant depression (TRD), defined as failure of two adequate antidepressant medication trials. We provide a qualitative review of ECT's effectiveness for TRD, methods to optimize ECT parameters to improve remission rates and side effect profiles, and ECT's proposed neurobiological mechanisms. Right unilateral (RUL) electrode placement has been shown to be as effective for major depression as bilateral ECT, and RUL is associated with fewer cognitive side effects. There is mixed evidence on how to utilize ECT to sustain remission (i.e., continuation ECT, psychotropic medications alone, or a combination of ECT and psychotropic medications). Related to neurobiological mechanisms, an increase in gray matter volume in the hippocampus-amygdala complex is reported post-ECT. High connectivity between the subgenual anterior cingulate and the middle temporal gyrus before ECT is associated with better treatment response. Rodent models have implicated changes in neurotransmitters including glutamate, GABA, serotonin, and dopamine in ECT's efficacy; however, findings in humans are limited. Altogether, while ECT remains a highly effective therapy, the neurobiological underpinnings associated with improvement of depression remain uncertain.

Molecular Biomarkers of Electroconvulsive Therapy Effects and Clinical Response: Understanding the Present to Shape the Future

Electroconvulsive therapy (ECT) represents an effective intervention for treatment-resistant depression (TRD). One priority of this research field is the clarification of ECT response mechanisms and the identification of biomarkers predicting its outcomes. We propose an overview of the molecular studies on ECT, concerning its course and outcome prediction, including also animal studies on electroconvulsive seizures (ECS), an experimental analogue of ECT. Most of these investigations underlie biological systems related to major depressive disorder (MDD), such as the neurotrophic and inflammatory/immune ones, indicating effects of ECT on these processes. Studies about neurotrophins, like the brain-derived neurotrophic factor (BDNF) and the vascular endothelial growth factor (VEGF), have shown evidence concerning ECT neurotrophic effects. The inflammatory/immune system has also been studied, suggesting an acute stress reaction following an ECT session. However, at the end of the treatment, ECT produces a reduction in inflammatory-associated biomarkers such as cortisol, TNF-alpha and interleukin 6. Other biological systems, including the monoaminergic and the endocrine, have been sparsely investigated. Despite some promising results, limitations exist. Most of the studies are concentrated on one or few markers and many studies are relatively old, with small sample sizes and methodological biases. Expression studies on gene transcripts and microRNAs are rare and genetic studies are sparse. To date, no conclusive evidence regarding ECT molecular markers has been reached; however, the future may be just around the corner.

Effects of repeated electroconvulsive shocks on dopamine supersensitivity psychosis model rats

While the long-term administration of antipsychotics is known to cause dopamine supersensitivity psychosis (DSP), recent studies revealed that DSP helps form the foundation of treatment resistance. Electroconvulsive shock (ES) is one of the more effective treatments for treatment-resistant schizophrenia. The objective of this study was to examine whether repeated ES can release rats from dopamine supersensitivity states such as striatal dopamine D2 receptor (DRD2) up-regulation and voluntary hyperlocomotion following chronic administration of haloperidol (HAL). HAL (0.75 mg/kg/day) was administered for 14 days via mini-pumps implanted in rats, and DRD2 density and voluntary locomotion were measured one day after drug cessation to confirm the development of dopamine supersensitivity. The rats with or without dopamine supersensitivity received repeated ES or sham treatments, and then DRD2 density was assessed and a voluntary locomotion test was performed. Chronic treatment with HAL led to the up-regulation of striatal DRD2 and hyperlocomotion in the rats one day after drug cessation. We thus confirmed that these rats experienced a dopamine supersensitivity state. Moreover, after repeated ES, locomotor activity and DRD2 density in the DSP model rats fell to the control level, while an ES sham operation had no effect on the dopamine supersensitivity state. The present study suggests that repeated ES could release DSP model rats from dopamine supersensitivity states. ES may be helpful for patients with DSP.

Blues in the Brain and Beyond: Molecular Bases of Major Depressive Disorder and Relative Pharmacological and Non-Pharmacological Treatments

Despite the extensive research conducted in recent decades, the molecular mechanisms underlying major depressive disorder (MDD) and relative evidence-based treatments remain unclear. Various hypotheses have been successively proposed, involving different biological systems. This narrative review aims to critically illustrate the main pathogenic hypotheses of MDD, ranging from the historical ones based on the monoaminergic and neurotrophic theories, through the subsequent neurodevelopmental, glutamatergic, GABAergic, inflammatory/immune and endocrine explanations, until the most recent evidence postulating a role for fatty acids and the gut microbiota. Moreover, the molecular effects of established both pharmacological and non-pharmacological approaches for MDD are also reviewed. Overall, the existing literature indicates that the molecular mechanisms described in the context of these different hypotheses, rather than representing alternative ones to each other, are likely to contribute together, often with reciprocal interactions, to the development of MDD and to the effectiveness of treatments, and points at the need for further research efforts in this field.

Brief isoflurane anesthesia regulates striatal AKT-GSK3β signaling and ameliorates motor deficits in a rat model of early-stage Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder primarily affecting the nigrostriatal dopaminergic system. The link between heightened activity of glycogen synthase kinase 3β (GSK3β) and neurodegene-rative processes has encouraged investigation into the potential disease-modifying effects of novel GSK3β inhibitors in experimental models of PD. Therefore, the intriguing ability of several anesthetics to readily inhibit GSK3β within the cortex and hippocampus led us to investigate the effects of brief isoflurane anesthesia on striatal GSK3β signaling in naïve rats and in a rat model of early-stage PD. Deep but brief (20-min) isoflurane anesthesia exposure increased the phosphorylation of GSK3β at the inhibitory Ser9 residue, and induced phosphorylation of AKTThr308 (protein kinase B; negative regulator of GSK3β) in the striatum of naïve rats and rats with unilateral striatal 6-hydroxydopamine (6-OHDA) lesion. The 6-OHDA protocol produced gradual functional deficiency within the nigrostriatal pathway, reflected as a preference for using the limb ipsilateral to the lesioned striatum at 2 weeks post 6-OHDA. Interestingly, such motor impairment was not observed in animals exposed to four consecutive isoflurane treatments (20-min anesthesia every 48 h; treatments started 7 days after 6-OHDA delivery). However, isoflurane had no effect on striatal or nigral tyrosine hydroxylase (a marker of dopaminergic neurons) protein levels. This brief report provides promising results regarding the therapeutic potential and neurobiological mechanisms of anesthetics in experimental models of PD and guides development of novel disease-modifying therapies.

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.

Rapid and lasting enhancement of dopaminergic modulation at the hippocampal mossy fiber synapse by electroconvulsive treatment

Electroconvulsive therapy (ECT) is an established effective treatment for medication-resistant depression with the rapid onset of action. However, its cellular mechanism of action has not been revealed. We have previously shown that chronic antidepressant drug treatments enhance dopamine D₁-like receptor-dependent synaptic potentiation at the hippocampal mossy fiber (MF)-CA3 excitatory synapse. In this study we show that ECT-like treatments in mice also have marked effects on the dopaminergic synaptic modulation. Repeated electroconvulsive stimulation (ECS), an animal model of ECT, strongly enhanced the dopamine-induced synaptic potentiation at the MF synapse in hippocampal slices. Significant enhancement was detectable after the second ECS, and further repetition of ECS up to 11 times monotonously increased the magnitude of enhancement. After repeated ECS, the dopamine-induced synaptic potentiation remained enhanced for more than 4 wk. These synaptic effects of ECS were accompanied by increased expression of the dopamine D₁ receptor gene. Our results demonstrate that robust neuronal activation by ECS induces rapid and long-lasting enhancement of dopamine-induced synaptic potentiation at the MF synapse, likely via increased expression of the D₁ receptor, at least in part. This rapid enhancement of dopamine-induced potentiation at the excitatory synapse may be relevant to the fast-acting antidepressant effect of ECT.

NEW & NOTEWORTHY

We show that electroconvulsive therapy (ECT)-like stimulation greatly enhances synaptic potentiation induced by dopamine at the excitatory synapse formed by the hippocampal mossy fiber in mice. The effect of ECT-like stimulation on the dopaminergic modulation was rapidly induced, maintained for more than 4 wk after repeated treatments, and most likely mediated by increased expression of the dopamine D1 receptor. These effects may be relevant to fast-acting strong antidepressant action of ECT.

Cortical electroconvulsive stimulation alleviates breeding-induced prepulse inhibition deficit in rats

In patients with medical-refractory schizophrenia electroconvulsive therapy (ECT), i.e., the induction of therapeutic seizures via cortical surface electrodes, is effectively used. Electroconvulsive stimulation (ECS) in rodents simulates ECT in humans and is applied to investigate the mechanisms underlying this treatment. Experimentally-induced reduced prepulse inhibition (PPI) of the acoustic startle response (ASR), i.e., the reduction of the startle response to an intense acoustic stimulus when this stimulus is shortly preceded by a weaker not-startling stimulus, serves as an endophenotype for neuropsychiatric disorders that are accompanied by disturbed sensorimotor gating, such as schizophrenia. Here we used rats selectively bred for high and low PPI to evaluate whether bifrontal cortical ECS would affect PPI. For this purpose, cortical screw electrodes were stereotactically implanted above the frontal cortex. After recovery ECS was applied for five consecutive days with stimuli of 1 ms pulse-width, 100 pulses/s, 1 s duration, ranging from 5.5 mA to 10 mA. PPI of ASR was measured one day before ECS, and on days 1, 7, and 14 after the last ECS. In rats with breeding-induced low PPI ECS increased PPI one week after stimulation. In contrast, ECS decreased PPI in rats with high PPI on the first day after stimulation. The reaction to the startle impulse was reduced by ECS without difference between groups. This work provides evidence that rats with breeding-induced high or low PPI could be used to further investigate the underlying mechanisms of ECT in neuropsychiatric disorders with disturbed sensorimotor gating like schizophrenia.

Understanding the pharmacogenetics of selective serotonin reuptake inhibitors

INTRODUCTION

The genetic background of antidepressant response represents a unique opportunity to identify biological markers of treatment outcome. Encouraging results alternating with inconsistent findings made antidepressant pharmacogenetics a stimulating but often discouraging field that requires careful discussion about cumulative evidence and methodological issues.

AREAS COVERED

The present review discusses both known and less replicated genes that have been implicated in selective serotonin reuptake inhibitors (SSRIs) efficacy and side effects. Candidate genes studies and genome-wide association studies (GWAS) were collected through MEDLINE database search (articles published till January 2014). Further, GWAS signals localized in promising genetic regions according to candidate gene studies are reported in order to assess the general comparability of results obtained through these two types of pharmacogenetic studies. Finally, a pathway enrichment approach is applied to the top genes (those harboring SNPs with p < 0.0001) outlined by previous GWAS in order to identify possible molecular mechanisms involved in SSRI effect.

EXPERT OPINION

In order to improve the understanding of SSRI pharmacogenetics, the present review discusses the proposal of moving from the analysis of individual polymorphisms to genes and molecular pathways, and from the separation across different methodological approaches to their combination. Efforts in this direction are justified by the recent evidence of a favorable cost-utility of gene-guided antidepressant treatment.