Dexmedetomidine protects against learning and memory impairments caused by electroconvulsive shock in depressed rats: Involvement of the NMDA receptor subunit 2B (NR2B)-ERK signaling pathway

Perioperative intravenous infusion of dexmedetomidine for alleviating postpartum depression after cesarean section: A meta-analysis and systematic review

The efficacy of perioperative dexmedetomidine (DEX) infusion as a precaution against postpartum depression (PPD) in women undergoing cesarean section has not been substantiated systematically. A literature search for RCTs on DEX against PPD was retrieved in the following databases from inception to January 3, 2024: PubMed, Embase, Web of Science, the Cochrane Library, CNKI, Wanfang, CBM, VIP, etc. A total of 13 RCTs with 1711 participants were included. Meta-analysis was performed by RevMan5.3 and Stata16 using a random-effects model. EPDS scores were significantly decreased in the DEX group within one week or over one week postpartum compared to the control group (SMD = -1.25, 95 %CI: -1.73 to -0.77; SMD = -1.08, 95 %CI: -1.43 to -0.73). The prevalence of PPD was significantly inferior to the control at both time points (RR = 0.36, 95 %CI: 0.24 to 0.54; RR = 0.39, 95 %CI: 0.26 to 0.57). Univariate meta-regression suggested that age influenced the heterogeneity of the EPDS scores (P = 0.039), and DEX infusion dose was a potential moderator (P = 0.074). The subgroup analysis results of PPD scores at both time points were consistent, showing that: ① Mothers younger than 30 years old had better sensitivity to DEX for treating PPD. ② The anti-PPD efficacy of continuous infusion of DEX by PCIA was superior to both single infusion and combined infusion. ③ DEX showed a better anti-PPD effect when the total infusion dose was ≤ 2 μg/kg. Moreover, DEX improved analgesia and sleep quality, provided appropriate sedation, and reduced the incidence of nausea, vomiting, and chills. The current evidence confirmed the prophylaxis and superiority of DEX for PPD. More high-quality, large-scale RCTs are required for verifying the reliability and formulating administration methods.

Antidepressant effects of dexmedetomidine compared with ECT in patients with treatment-resistant depression

OBJECTIVE

This pilot study was designed to investigate the antidepressant effects of dexmedetomidine (DEX), a selective α2-adrenergic receptor agonist, in patients with treatment-resistant depression (TRD). The antidepressant effects of dexmedetomidine was compared with ECT, which is widely used in clinical practice for treatment of patients with TRD.

METHODS

Seventy six patients with TRD were randomly assigned to receive 10 sessions of DEX infusions or electroconvulsive therapy (ECT) treatment. The primary outcome was the changes of depression severity determined by the improvement of 24-item Hamilton Depression Rating Scale (HDRS-24). The second outcomes were the rates of therapeutic response (reduction in HDRS-24 ≥ 50 %) and remission (HDRS-24 ≤ 10 and reduction in HDRS-24 ≥ 60 %) at posttreatment and after 3 months of follow-up visits.

RESULTS

We found that 10 sessions of DEX infusions or ECT treatments significantly improved HDRS-24 scores at posttreatment and after 3 months of follow-up visits compared with the baseline. In addition, there was no significant difference between DEX infusions and ECT treatments regarding HDRS-24 at these evaluating points. Furthermore, the depression severity dropped to mild after 2 sessions of DEX infusion. In contrast, at least 6 sessions of ECT treatment were needed to achieve a same level. Finally, the rates of therapeutic response and remission were comparable between the two groups. No serious adverse events were observed.

CONCLUSIONS

Based on current published evidence, we conclude that DEX exhibits rapid and durable antidepressant properties similar to ECT but with fewer side effects.

The role of neurotrophic factors in novel, rapid psychiatric treatments

Neurotrophic factors are a family of growth factors that modulate cellular growth, survival, and differentiation. For many decades, it has been generally believed that a lack of neurotrophic support led to the decreased neuronal synaptic plasticity, death, and loss of non-neuronal supportive cells seen in neuropsychiatric disorders. Traditional psychiatric medications that lead to immediate increases in neurotransmitter levels at the synapse have been shown also to elevate synaptic neurotrophic levels over weeks, correlating with the time course of the therapeutic effects of these drugs. Recent advances in psychiatric treatments, such as ketamine and psychedelics, have shown a much faster onset of therapeutic effects (within minutes to hours). They have also been shown to lead to a rapid release of neurotrophins into the synapse. This has spurred a significant shift in understanding the role of neurotrophins and how the receptor tyrosine kinases that bind neurotrophins may work in concert with other signaling systems. In this review, this renewed understanding of synaptic receptor signaling interactions and the clinical implications of this mechanistic insight will be discussed within the larger context of the well-established roles of neurotrophic factors in psychiatric disorders and treatments.

Dexmedetomidine in the Treatment of Depression: An Up-to-date Narrative Review

Depressive disorders (DD) are common, and their prevalence is expected to rise over the next decade. Depressive disorders are linked to significant morbidity and mortality. The clinical conundrum of depressive disorders lies in the heterogeneity of their phenomenology and etiology. Further, the currently available antidepressants have several limitations, including a delayed onset of action, limited efficacy, and an unfavorable side effect profile. In this review, Dexmedetomidine (DEX), a highly selective and potent α2-adrenergic receptor (α2-AR) agonist, is proposed as a potentially novel antidepressant with multiple mechanisms of action targeting various depression pathophysiological processes. These mechanisms include modulation of the noradrenergic system, regulation of neuroinflammation and oxidative stress, influence on the Brain-Derived Neurotrophic Factor (BDNF) levels, and modulation of neurotransmitter systems, such as glutamate. The review begins with an introduction before moving on to a discussion of DEX's pharmacological features. The pathophysiological and phenomenological targets of DD are also explored, along with the review of the existing preclinical and clinical evidence for DEX's putative anti-depressant effects. Finally, the review ends by presenting the pertinent conclusions and future directions.

Clinical Improvement in Depression and Cognitive Deficit Following Electroconvulsive Therapy

Electroconvulsive therapy (ECT) is a long-standing treatment choice for disorders such as depression when pharmacological treatments have failed. However, a major drawback of ECT is its cognitive side effects. While numerous studies have investigated the therapeutic effects of ECT and its mechanism, much less research has been conducted regarding the mechanism behind the cognitive side effects of ECT. As both clinical remission and cognitive deficits occur after ECT, it is possible that both may share a common mechanism. This review highlights studies related to ECT as well as those investigating the mechanism of its outcomes. The process underlying these effects may lie within BDNF and NMDA signaling. Edema in the astrocytes may also be responsible for the adverse cognitive effects and is mediated by metabotropic glutamate receptor 5 and the protein Homer1a.

Memory impairments in rodent depression models: A link with depression theories

More than 80% of depressed patients struggle with learning new tasks, remembering positive events, or concentrating on a single topic. These neurocognitive deficits accompanying depression may be linked to functional and structural changes in the prefrontal cortex and hippocampus. However, their mechanisms are not yet completely understood. We conducted a narrative review of articles regarding animal studies to assess the state of knowledge. First, we argue the contribution of changes in neurotransmitters and hormone levels in the pathomechanism of cognitive dysfunction in animal depression models. Then, we used numerous neuroinflammation studies to explore its possible implication in cognitive decline. Encouragingly, we also observed a positive correlation between increased oxidative stress and a depressive-like state with concomitant memory deficits. Finally, we discuss the undeniable role of neurotrophin deficits in developing cognitive decline in animal models of depression. This review reveals the complexity of depression-related memory impairments and highlights the potential clinical importance of gathered findings for developing more reliable animal models and designing novel antidepressants with procognitive properties.

RAGE signaling pathway is involved in CUS-induced depression-like behaviors by regulating the expression of NR2A and NR2B in rat hippocampus DG

NMDA receptors play pivotal roles in the neurobiology of chronic stress-induced mood disorders. But the mechanism for chronic stress to disturb the expression of NMDA receptor subunits is still unclear. Recent researches indicated the involvement RAGE signaling pathway in regulation of glutamate system functions. In this study, we hypothesized RAGE signaling pathway mediated chronic stress-induced alteration in the expression of NMDA receptor subunits, leading to depressive-like behaviors. CUS decreased the expression of RAGE, NR2A, and NR2B, inhibited the phosphorylation of transcript factor ERK and CREB in rat hippocampus DG. RAGE knockdown in hippocampus DG by RAGE shRNA lentiviral particles induced depressive-like behaviors, reduced the mRNA and protein expression of NR2A and NR2B, and inhibited the phosphorylation of ERK and CREB. RAGE over-expression in hippocampus DG by RAGE adenovirus particles reversed the effects of CUS on depressive-like behaviors, ERK and CREB phosphorylation, and NR2A and NR2B expression. Our findings suggests that RAGE signaling pathway at least partially participates in the regulation of NR2A and NR2B expression, which mediates the effects of chronic stress on the depressive-like behaviors. These data provide evidence for RAGE signaling as a possible new pathway through which chronic stress results in the maladaptation of NMDA receptors.

Dexmedetomidine suppresses the isoflurane-induced neurological damage by upregulating Heme Oxygenase-1 via activation of the mitogen-activated protein kinase kinase 1/extracellular regulated protein kinases 1/nuclear factor erythroid 2-related factor 2 axis in aged rats

Dexmedetomidine (DEX) displays a neuroprotective role in aged rats with isoflurane (ISO)-induced cognitive impairment through antioxidant, and anti-inflammatory, and anti-apoptotic effects. Therefore, the present study was performed to define the molecular mechanism of DEX on ISO-induced neurological impairment in aged rats in relation to the MEK1/ERK1/Nrf2/HO-1 axis. The study enrolled elderly patients undergoing ISO anesthesia. Patient cognitive function following treatment with DEX was evaluated using mini-mental state examination (MMSE). The results revealed that DEX supplementation of anesthesia contributed to higher MMSE scores in patients one week post treatment. Rat model of neurological impairment was also induced in 18-month-age Wistar rats by ISO, followed by DEX treatment. Based on the results of Morris water maze experiment, ELISA, and TUNEL and hematoxylin-eosin staining, in vivo experiments confirmed that DEX could reduce the oxidative stress and neurological damage induced by ISO in rats. DEX activated the nuclear factor erythroid 2-related factor (Nrf2)/Heme Oxygenase 1 (HO-1) pathway. DEX upregulated the expression of Nrf2 and HO-1 by activating the MEK1/ERK1 pathway, whereby attenuating the ISO-caused oxidative stress and neurological damage in rats. Collectively, DEX suppresses the ISO-induced neurological impairment in the aged rats by promoting HO-1 through activation of the MEK1/ERK1/Nrf2 axis.

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.

Role of NR2B/ERK signaling in the neuroprotective effect of dexmedetomidine against sevoflurane induced neurological dysfunction in the developing rat brain

Dexmedetomidine (DEX) is a potent α‑2 adrenergic receptor agonist and has been widely applied in clinic. The present study explored the protective effect of DEX on sevoflurane‑induced learning and cognitive impairment and examined its underlying mechanism. Sprague‑Dawley rat pups were exposed to 0.85% sevoflurane for 6 h and injected with DEX in different doses. The Morris water maze test was performed to evaluate the learning and memory function of rats. Western blot was used for the measurement of protein levels. The water maze results indicated that sevoflurane treatment increased the escape latency but reduced the time spent in the original quadrant of rats. The protein levels of NR2B, phosphorylated ERK were significantly influenced by sevoflurane. Ifenprodil administration alleviated sevoflurane‑induced neurological impairment. DEX treatment reversed the effect of sevoflurane on both escape latency and time in original quadrant in a dose manner, and pretreatment with DEX had the most dramatic effect. DEX regulated the NR2B/ERK signaling in sevoflurane treated rats. NR2B/ERK signaling is involved in sevoflurane induced neurological impairment. DEX may protect against sevoflurane induced neurological dysfunction in the developing rat brain via regulating the NR2B/ERK signaling.

Effects of N-Methyl-D-aspartate receptor (NMDAR) and Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) on learning and memory impairment in depressed rats with different charge by modified electroconvulsive shock

Background

With the development of modified electroshock therapy (MECT), it has become necessary to increase the electric quantity in order to achieve a good antidepressant effect, but this increase will lead to more serious learning and memory impairment. The purpose of this study was to investigate the intrinsic mechanism of cognitive impairment induced by high-energy electroconvulsive shock (MECS, an animal model of MECT).

Methods

Rats were randomly divided into 6 groups: control (C, n=6), M0, M60, M120, M180, and M240 groups (MECS at 0, 60, 120, 180, and 240 mC stimulation intensity after 80 mg/kg propofol, with 12 rats in each group). Their depression-like behavior and learning and memory ability were evaluated by sucrose preference test (SPT), open field test (OFT), and Morris water maze test (MWM). The expression of phospho-NMDA receptor 1 (GluN1), GluN2A, GluN2B, Ca²⁺/calmodulin-dependent protein kinase IIα (CaMKIIα), p-T305-CaMKII, and postsynaptic densities-95 (PSD-95) in hippocampus were detected by western blot. The co-expression of CaMKIIα and GluN2B subunit was detected by co-immunoprecipitation (CO-IP).

Results

The chronic unpredictable mild stresses (CUMS) procedure successfully induced depression-like behavior in rats, which was improved in varying degrees after MECS. The results showed that the expression of GluN1, GluN2A, GluN2B, and PSD-95 decreased with the increase of charge, while p-T305-CaMKII increased, which led to the deterioration of learning and memory ability, but the expression change of CaMKIIα was not statistically significant.

Conclusions

Increase in the MECS charge adjusts the synaptic plasticity by changing the binding amount of CaMKIIα and its subunit GluN2B and the level of CaMKII autophosphorylation, thereby impairing learning and memory functions.

Effects of Alpha-2 Adrenergic Agonist Mafedine on Brain Electrical Activity in Rats after Traumatic Brain Injury

The search for and development of new neuroprotective (or cerebroprotective) drugs, as well as suitable methods for their preclinical efficacy evaluation, are priorities for current biomedical research. Alpha-2 adrenergic agonists, such as mafedine and dexmedetomidine, are a highly appealing group of drugs capable of reducing neurological deficits which result from brain trauma and vascular events in both experimental animals and human patients. Thus, our aim was to assess the effects of mafedine and dexmedetomidine on the brain’s electrical activity in a controlled cortical-impact model of traumatic brain injury (TBI) in rats. The functional status of the animals was assessed by electrocorticography (ECoG), using ECoG electrodes which were chronically implanted in different cortical regions. The administration of intraperitoneal mafedine sodium at 2.5 mg∙kg⁻¹ at 1 h after TBI induction, and daily for the following 6 days, restored interhemispheric connectivity in remote brain regions and intrahemispheric connections within the unaffected hemisphere at post-TBI day 7. Animals that had received mafedine sodium also demonstrated an improvement in cortical responses to photic and somatosensory stimulation. Dexmedetomidine at 25 μg∙kg⁻¹ did not affect the brain’s electrical activity in brain-injured rats. Our results confirm the previously described neuroprotective effects of mafedine sodium and suggest that ECoG registration and analysis are a viable method evaluating drug efficacy in experimental animal models of TBI.

Antidepressant-like effects of Z-ligustilide on chronic unpredictable mild stress-induced depression in rats

Depression is a significant public health issue and its neuropathogenesis is associated with the dysfunction of progesterone and allopregnanolone biosynthesis. Z-ligustilide (LIG), one of the main components of the herb Angelica sinensis (Oliv.) Diels (AS), is reported to have antidepressant activities. The present study aimed to evaluate the antidepressant-like effects of LIG via behavioral tests and to measure the levels of progesterone and allopregnanolone in the prefrontal cortex and hippocampus. The results demonstrated that LIG (20 and 40 mg/kg) exerted antidepressant-like effects, confirmed by increased mobility, locomotion, rearing frequency and preference to sucrose. Furthermore, the levels of progesterone and allopregnanolone in the prefrontal cortex and hippocampus were markedly increased following treatment with LIG (20 and 40 mg/kg), indicating that both neurosteroids could serve a significant role in the antidepressant-like effects of LIG.

Inhibition of CB1 receptor alleviates electroconvulsive shock-induced memory impairment by regulating hippocampal synaptic plasticity in depressive rats

Electroconvulsive therapy (ECT) is one of the most effective treatments for depression, but it can cause cognitive deficit. Unfortunately, effective preventive measures are still lacking. The endocannabinoid system is thought to play a key role in regulation of cognitive process. Whether the endocannabinoid system is involved in the learning and memory impairment caused by ECS remain unclear. In this work, we first found that cannabinoid receptor type 1 (CB1R) and 2-arachidonoylglycerol (2-AG) were strongly expressed in hippocampus by electroconvulsive shock (ECS) in a rat depression model established by chronic mild stress (CMS). Pharmacological inhibition of CB1R using AM251 in vivo resulted in a pronounced relief in ECS-induced spatial learning and memory impairment as well as in a marked reversal of impaired hippocampal long-term potentiation (LTP), and reduced synapse-related proteins expression. Furthermore, results of sucrose preference test (SPT) and open-field test (OFT) showed that AM251 had no significant impact on the therapeutic effects of ECS on pleasure and psychomotor activity. Taken together, we identified that CB1R is involved in the ECS-induced spatial learning and memory impairment and Inhibition of CB1R facilitates the recovery of memory impairment and hippocampal synaptic plasticity, without interfering with the therapeutic effects of ECS in depressed rats.

Dexmedetomidine Mediates Neuroglobin Up-Regulation and Alleviates the Hypoxia/Reoxygenation Injury by Inhibiting Neuronal Apoptosis in Developing Rats

Background

Exploring the effective therapy for neonatal hypoxic-ischemic brain injury is an important goal. This study was designed to investigate how dexmedetomidine (DEX) contribute to hypoxic brain injury.

Methods

Developing Sprague-Dawley rat models of hypoxia/reoxygenation (H/R) injury were constructed to simulate neonatal hypoxic brain injury for DEX treatment. Immunohistochemistry and western blot were performed to measure neuroglobin (Ngb) protein expression in hippocampal tissues. Hippocampal neuron injury and apoptosis were detected by Nissl staining and TUNEL assay, respectively. A Morris water maze (MWM) test was performed to evaluate the long-term learning and memory function.

Results

The expression of Ngb was increased following H/R model establishment and up-regulated by medium and high doses of DEX, but not up-regulated by low doses of DEX. Medium and high doses of DEX alleviated the H/R injury as well as induced the reduction of Nissl bodies and apoptosis. Besides, medium and high doses of DEX down-regulated cytosolic Cyt-c, Apaf-1, and caspase-3 in H/R injury model. MWM test showed that medium and high doses of DEX significantly shortened the escape latency and enhanced the number of platform crossings. However, low doses of DEX have no effect on Nissl bodies, mitochondrial apoptosis, expression of apoptosis-related proteins and long-term learning functions.

Conclusions

DEX induced Ngb expression in H/R rat models. The neuroprotection of DEX-mediated Ngb up-regulation may be achieved by inhibiting neuronal apoptosis through the mitochondrial pathway. Findings indicated that DEX may be useful as an effective therapy for neonatal hypoxic brain injury.

Effect of dexmedetomidine for sedation and cognitive function in patients with preoperative anxiety undergoing carotid artery stenting

Objective

This study was performed to examine the effect of dexmedetomidine for intraoperative sedation and postoperative cognitive function in patients with preoperative anxiety undergoing carotid artery stenting.

Methods

Eighty patients were randomly divided into two groups: the dexmedetomidine group and the control group. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). Anxiety was evaluated using the Amsterdam Preoperative Anxiety and Information Scale. Routine monitoring indices were recorded during surgery, and cognitive function indices were recorded before drug infusion (T₀), 10 minutes after drug infusion (T₁), at the end of surgery (T₂), and 6 hours after surgery (T₃).

Results

The anxiety scores were not significantly different between the two groups at T0, but they became significantly different at T_1–3. The MMSE scores in both groups increased at 1 and 7 days postoperatively; although the increase in the dexmedetomidine group was sharper, there was no significant difference. In both groups, the MMSE scores at 1 and 7 days after surgery were not significantly different from those at 1 day before surgery.

Conclusion

Dexmedetomidine can improve patients’ anxiety and achieve a sufficient sedation effect without causing postoperative cognitive dysfunction.

The potential anti-depressant properties of dexmedetomidine infusion: a review of mechanistic, preclinical, and clinical evidence

Major depressive disorder (MDD) is a highly prevalent and disabling condition for which the currently available treatments are not fully effective. Existing unmet needs include rapid onset of action and optimal management of concurrent agitation. Dexmedetomidine (DEX) is a selective and potent α2-adrenergic receptor (α2-AR) agonist, with unique pharmacokinetic and pharmacodynamic properties. In this review, we discuss pre-clinical and clinical studies which focused on DEX in the context of its putative antidepressant effects for the management of MDD. Preliminary data support DEX as an antidepressant with fast onset of action, which would be especially helpful for patients experiencing treatment resistant depression, and agitation. We further explore the mechanistic and clinical implications of considering DEX as a putative antidepressant agent, and the next steps to explore the efficacy of low dose DEX infusion among patients with treatment resistant depression.

Successful Treatment of Refractory Cancer Pain and Depression with Continuous Intrathecal Administration of Dexmedetomidine and Morphine: A Case Report

Patients who have refractory cancer pain suffer both physically and psychologically. Cancer pain management has improved over the past few decades. However, the treatment of refractory cancer pain is still challenging all over the world. Intraspinal analgesia has become an effective strategy to treat refractory pain in patients with cancer. In this report, we present a patient receiving a large dose of intrathecal opioids for refractory cancer pain, and who is also afflicted with pain-induced depression. Dexmedetomidine (DEX) was used as part of a multimodal analgesic regimen that successfully alleviated both the patient's pain and depression. An intrathecal infusion of DEX may serve as an adjuvant drug in the treatment of cancer pain and pain-related depression.

Dexmedetomidine Attenuates Neurotoxicity in Developing Rats Induced by Sevoflurane through Upregulating BDNF-TrkB-CREB and Downregulating ProBDNF-P75NRT-RhoA Signaling Pathway

To investigate the mechanism dexmedetomidine in relieving the neurotoxicity of a developing brain induced by sevoflurane. Sprague-Dawley rats, 6 days old, were randomly divided into three groups. Rats in the control group were inhaled with air after injection of normal saline; rats in the sevoflurane group were injected with normal saline and inhaled with 3% sevoflurane for 2 h in three consecutive day; rats in the dexmedetomidine group were inhaled with 3% sevoflurane after intraperitoneal injection of dexmedetomidine 25 μg/kg. WB results showed that mBDNF, pTrkB/TrkB, and CREB were significantly decreased in the hippocampus of the sevoflurane group, which are significantly upregulated in the dexmedetomidine group. In the sevoflurane group, proBDNF, P75NRT, and RhoA were significantly increased, which were significantly lower than those in the dexmedetomidine group than those in the sevoflurane group. The expression BDNF was downregulated in the sevoflurane group, while the proBDNF was upregulated in the sevoflurane group. In the Morris water maze test, the escape latency of the sevoflurane group was significantly prolonged. In sevoflurane groups, the number of crossing platform was significantly reduced, the synaptic protein decreased significantly, and this effect was reversed in rats of the dexmedetomidine group. Dexmedetomidine could reduce synaptic plasticity decline in developing rats induced by sevoflurane, through downregulating the proBDNF-p75NTR-RhoA pathway and upregulating BDNF-TrkB-CREB.

Effects of Electroconvulsive Therapy on Depression and Its Potential Mechanism

Depression is one of the most common disorders causing mortality around the world. Although electroconvulsive therapy (ECT) is, along with antidepressants and psychotherapy, one of the three major treatments of depression, it is still considered as the last resort for depressed patients. This situation is partially due to limited studies and uncertainty regarding its mechanism. However, decades of increased research have focused on the effects of ECT on depression and its potential mechanism. Furthermore, these investigations may suggest that ECT should be a first-line therapy for depression due to its profound effects in relieving desperation in certain situations. Here, we outline recent clinical and preclinical studies and summarize the advantages and disadvantages of ECT. Thus, this review may provide some hints for clinical application.

Baicalin ameliorates chronic mild stress-induced depression-like behaviors in mice and attenuates inflammatory cytokines and oxidative stress

The natural flavonoid glycoside baicalin (BA) produces a variety of pharmaceutical effects, particularly for psychiatric/neurological disorders. This study evaluated the behavioral and neuroprotective effects of BA in mice subjected to chronic unpredictable mild stress, a model of depression. BA (25 and 50 mg/kg) significantly increased sucrose consumption and reduced immobility times in the tail suspension and forced swim tests, demonstrating that BA alleviated depression-like behaviors. Moreover, BA reduced the levels of inflammatory cytokines, such as interleukin 1β, interleukin 6, and tumor necrosis factor α, in serum and in the hippocampus. BA also abrogated increases in NMDAR/NR2B and Ca²⁺/calmodulin-dependent protein kinase II, and the decrease in phosphorylated ERK and reactive oxygen species production in mice subjected to chronic unpredictable mild stress. These findings suggested that the antidepressive effects of BA are due to the regulation of an NMDAR/NR2B-ERK1/2-related pathway and inhibition of inflammatory cytokines and oxidative stress. Thus, BA represents a potential candidate drug for patients suffering from depression.

Inhibition of activated astrocyte ameliorates lipopolysaccharide- induced depressive-like behaviors

BACKGROUND

Numerous studies indicate that inflammation plays important roles in the development of depression. Astrocytes are crucial regulators of immune response in the central nervous system, and strongly activated by pro-inflammatory cytokines. We hypothesized that inhibition of activated astrocytes contributed to ameliorate depressive-like symptoms.

METHODS

This study evaluated the antidepressant-like effect of inhibition of activated astrocytes, by a well-established astrocyte inactivator fluorocitrate (FC), on a lipopolysaccharide (LPS)-induced model of depression. Forced swim test (FST), tail suspension test (TST) and sucrose preference test were used to assess depressive-like behaviors. The expression of fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF) and neuroinflammation were determined in the hippocampus and cortex.

RESULTS

The results demonstrated that LPS increased immobility time in the TST and FST, reduced sucrose preference as well. LPS also enhanced the expression of IL-1β, TNF-α, iNOS and GFAP, accompanying with decreased expression of BDNF in the hippocampus and cortex. Inhibition of activated astrocytes by FC significantly prevented LPS- induced alteration in the FST, TST and sucrose preference test. Moreover, in the hippocampus and cortex, inhibition of activated astrocytes by FC significantly attenuated increases of neuroinflammation and GFAP whereas reversed decrease of BDNF in LPS- challenged depression.

CONCLUSIONS

Taken together, the results suggest that inhibition of activated astrocytes ameliorates LPS-induced depressive-like behavior, providing the first evidence that inhibition of activated astrocytes might represent a novel therapeutic target for depression.

Changes in synaptic plasticity are associated with electroconvulsive shock-induced learning and memory impairment in rats with depression-like behavior

BACKGROUND

Accompanied with the effective antidepressant effect, electroconvulsive shock (ECS) can induce cognitive impairment, but the mechanism is unclear. Synaptic plasticity is the fundamental mechanism of learning and memory. This study aimed to investigate the effect of ECS on synaptic plasticity changes in rats with depression-like behavior.

METHODS

Chronic unpredictable mild stress procedure was conducted to establish a model of depression-like behavior. Rats were randomly divided into the following three groups: control group with healthy rats (group C), rats with depression-like behavior (group D), and rats with depression-like behavior undergoing ECS (group DE). Depression-like behavior and spatial learning and memory function were assessed by sucrose preference test and Morris water test, respectively. Synaptic plasticity changes in long-term potentiation (LTP), long-term depression (LTD), depotentiation, and post-tetanic potentiation (PTP) were tested by electrophysiological experiment.

RESULTS

ECS could exert antidepressant effect and also induced spatial learning and memory impairment in rats with depression-like behavior. And, data on electrophysiological experiment showed that ECS induced lower magnitude of LTP, higher magnitude of LTD, higher magnitude of depotentiation, and lower magnitude of PTP.

CONCLUSION

ECS-induced learning and memory impairment may be attributed to postsynaptic mechanism of LTP impairment, LTD and depotentiation enhancement, and presynaptic mechanism of PTP impairment.

Dexmedetomidine Combined With Intravenous Anesthetics in Electroconvulsive Therapy: A Meta-analysis and Systematic Review

OBJECTIVE

The aim of this study was to investigate how the combined use of dexmedetomidine with intravenous anesthetics influences seizure duration and circulatory dynamics in electroconvulsive therapy (ECT).

METHODS

A literature search was performed to identify studies that evaluated the effect of dexmedetomidine on motor- or electroencephalogram (EEG)-based seizure durations and maximum mean arterial pressure (MAP) and heart rate (HR) after ECT. Moreover, recovery time and post-ECT agitation were evaluated.

RESULTS

Six studies enrolling 166 patients in 706 ECT sessions were included. There was no significant difference in motor or EEG seizure duration between dexmedetomidine and nondexmedetomidine groups [motor: 6 studies; mean difference (MD), 1.62; 95% confidence interval (CI), -2.24 to 5.49; P = 0.41; EEG: 3 studies; MD, 2.34; 95% CI, -6.03 to 10.71; P = 0.58]. Both maximum MAP and HR after ECT were significantly reduced in the dexmedetomidine group (MAP: 6 studies; MD, -4.83; 95% CI, -8.43 to -1.22; P = 0.009; HR: 6 studies; MD, -6.68; 95% CI, -10.74 to -2.62; P = 0.001). Moreover, the addition of dexmedetomidine did not significantly prolong recovery time when the reduced-dose propofol was used (4 studies; MD, 63.27; 95% CI, -15.41 to 141.96; P = 0.12).

CONCLUSIONS

The use of dexmedetomidine in ECT did not interfere with motor and EEG seizure durations but could reduce maximum MAP and HR after ECT. Besides, the addition of dexmedetomidine in ECT did not prolong recovery time when reduced-dose propofol was used. It might be worthwhile for patients to receive dexmedetomidine before the induction of anesthesia in ECT.

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.

Neuroprotection and neurotoxicity in the developing brain: an update on the effects of dexmedetomidine and xenon

Growing and consistent preclinical evidence, combined with early clinical epidemiological observations, suggest potentially neurotoxic effects of commonly used anesthetic agents in the developing brain. This has prompted the FDA to issue a safety warning for all sedatives and anesthetics approved for use in children under three years of age. Recent studies have identified dexmedetomidine, the potent α2-adrenoceptor agonist, and xenon, the noble gas, as effective anesthetic adjuvants that are both less neurotoxic to the developing brain, and also possess neuroprotective properties in neonatal and other settings of acute ongoing neurologic injury. Dexmedetomidine and xenon are effective anesthetic adjuvants that appear to be less neurotoxic than other existing agents and have the potential to be neuroprotective in the neonatal and pediatric settings. Although results from recent clinical trials and case reports have indicated the neuroprotective potential of xenon and dexmedetomidine, additional randomized clinical trials corroborating these studies are necessary. By reviewing both the existing preclinical and clinical evidence on the neuroprotective effects of dexmedetomidine and xenon, we hope to provide insight into the potential clinical efficacy of these agents in the management of pediatric surgical patients.