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Major depressive disorder is one of the most prevalent mental health disorders, posing a global socioeconomic burden. Conventional antidepressant treatments have a slow onset of action, and 30% of patients show no clinically significant treatment response. The recently approved fast‐acting antidepressant S‐ketamine, an N‐methyl‐D‐aspartate receptor antagonist, provides a new approach for treatment‐resistant patients. However, knowledge of S‐ketamine's mechanism of action is still being established. Depressed human subjects have lower striatal dopamine transporter (DAT) availability compared to healthy controls. Rodent studies report increased striatal dopamine concentration in response to acute ketamine administration. In vivo [18F]FE‐PE2I ([18F]‐(E)‐N‐(3‐iodoprop‐2‐enyl)‐2β‐carbofluoroethoxy‐3β‐(4′‐methyl‐phenyl) nortropane) positron emission tomography (PET) imaging of the DAT has not previously been applied to assess the effect of acute subanesthetic S‐ketamine administration on DAT availability. We applied translational in vivo [18F]FE‐PE2I PET imaging of the DAT in healthy female rats to evaluate whether an acute subanesthetic intraperitoneal dose of 15 mg/kg S‐ketamine alters DAT availability. We also performed [3H]GBR‐12935 autoradiography on postmortem brain sections. We found no effect of acute S‐ketamine administration on striatal DAT binding using [18F]FE‐PE2I PET or [3H]GBR‐12935 autoradiography. This negative result does not support the hypothesis that DAT changes are associated with S‐ketamine's rapid antidepressant effects, but additional studies are warranted. [ABSTRACT FROM AUTHOR]

The available treatments for depression have substantial limitations, including low response rates and substantial lag time before a response is achieved. We applied deep brain stimulation (DBS) to the lateral habenula (LHb) of two rat models of depression (Wistar Kyoto rats and lipopolysaccharide-treated rats) and observed an immediate (within seconds to minutes) alleviation of depressive-like symptoms with a high-response rate. Simultaneous functional MRI (fMRI) conducted on the same sets of depressive rats used in behavioral tests revealed DBS-induced activation of multiple regions in afferent and efferent circuitry of the LHb. The activation levels of brain regions connected to the medial LHb (M-LHb) were correlated with the extent of behavioral improvements. Rats with more medial stimulation sites in the LHb exhibited greater antidepressant effects than those with more lateral stimulation sites. These results indicated that the antidromic activation of the limbic system and orthodromic activation of the monoaminergic systems connected to the M-LHb played a critical role in the rapid antidepressant effects of LHb-DBS. This study indicates that M-LHb-DBS might act as a valuable, rapid-acting antidepressant therapeutic strategy for treatment-resistant depression and demonstrates the potential of using fMRI activation of specific brain regions as biomarkers to predict and evaluate antidepressant efficacy.

Esketamine is a non-selective, competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor in the brain. Through NMDA receptor antagonism, esketamine causes a transient increase in glutamate release, leading to increases in neurotrophic signaling and restoration of synaptic function in brain regions involved in mood regulation and emotional behavior. Several randomized clinical trials have shown its effectiveness in reducing the symptoms of depression in some people, despite its short-term side effects that include mainly disorientation, dizziness, nausea, and increased blood pressure. In 2019, the United States Food and Drug Administration (FDA) as well as the European Medicines Agency approved the use of esketamine nasal spray in combination with an oral antidepressant for treatment-resistant depression in adults. Our study aimed to evaluate the effectiveness of this new therapeutic proposal in a case series of five Greek patients with treatment- resistant depression. Intranasal esketamine was administered under medical supervision in combination with an oral antidepressant. Depressive symptoms were evaluated at three time points (baseline, end of treatment, and one-year post-treatment) using the Montgomery-Åsberg Depression Rating Scale (MADRS), the Patient Health Questionnaire (PHQ-9), the CGI Clinical Global Impression Scale, and the Perceived Deficits Questionnaire for Depression (PDQ-D). Possible side effects were assessed using the Richmond Suppression Agitation Scale (RASS), the Sheehan Disability Scale (SDS), the CADSS Disruptive States Scale, and a predefined list of adverse events (AEs) and serious adverse events (SAEs). Patients followed an individualized treatment plan for seven to twelve months depending on the achievement of an adequate response. Statistical analysis of the results revealed a significant improvement (p<0.05) on all scales used. All participants maintained their level of improvement at follow-up after twelve months. Adverse effects were found to be mild and tolerable. It is worth noting that significant side effects were reported only by the two patients with comorbid personality disorder. The results, despite limited to a small sample, indicate the positive effect of esketamine on the stable reduction of depressive symptoms among patients with resistant depression, even after the completion of treatment.

Ketamine has rapid and robust antidepressant effects. However, unwanted psychotomimetic effects limit its widespread use. Hence, several studies examined whether GluN2B-subunit selective NMDA antagonists would exhibit a better therapeutic profile. Although preclinical work has revealed some of the mechanisms of action of ketamine at cellular and molecular levels, the impact on brain circuitry is poorly understood. Several neuroimaging studies have examined the functional changes in the brain induced by acute administration of ketamine and Ro 25-6981 (a GluN2B-subunit selective antagonist), but the changes in the microstructure of gray and white matter have received less attention. Here, the effects of ketamine and Ro 25-6981 on gray and white matter integrity in male Sprague–Dawley rats were determined using diffusion-weighted magnetic resonance imaging (DWI). In addition, DWI-based structural brain networks were estimated and connectivity metrics were computed at the regional level. Immunohistochemical analyses were also performed to determine whether changes in myelin basic protein (MBP) and neurofilament heavy-chain protein (NF200) may underlie connectivity changes. In general, ketamine and Ro 25-6981 showed some opposite structural alterations, but both compounds coincided only in increasing the fractional anisotropy in infralimbic prefrontal cortex and dorsal raphe nucleus. These changes were associated with increments of NF200 in deep layers of the infralimbic cortex (together with increased MBP) and the dorsal raphe nucleus. Our results suggest that the synthesis of NF200 and MBP may contribute to the formation of new dendritic spines and myelination, respectively. We also suggest that the increase of fractional anisotropy of the infralimbic and dorsal raphe nucleus areas could represent a biomarker of a rapid antidepressant response. [ABSTRACT FROM AUTHOR]

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Abstract Background Major depressive disorder (MDD) is a common psychiatric disorder. With systematic antidepressant treatment, 50–75% of patients have a treatment response but require 4–6 weeks to have their symptoms alleviated. Therefore, researchers anticipate the development of novel fast-acting antidepressants. Previous studies have revealed that the decrease of bio-energetic metabolism may contribute to the occurrence of depression, while our team has found adenosine triphosphate (ATP) and phosphocreatine (PCr) to be fast-acting antidepressants in the depressed-animal model. ATP and PCr have already been widely prescribed clinically as energy supplements for cells. This will be the first clinical attempt of the intravenous administration of ATP and PCr combined with orally administered fluoxetine in MDD. Methods This is a single-center, randomized, double-blind, placebo-controlled pilot study. A total of 42 patients will be divided randomly into three groups. Patients will receive an intravenous administration of ATP or PCr or saline twice daily combined with orally administered fluoxetine (20 mg/day) for the first 2 weeks and fluoxetine monotherapy for the following 4 weeks. Follow-up assessment will be completed at week 10. Feasibility outcomes will include percentages of patient eligibility, intention to use medication, willingness to participate, drug adherence, completion of the scheduled assessment, retention, drop-out, etc. Physical examination results, Side Effect Rating Scale, adverse events, results from blood tests, electroencephalogram, and electrocardiograph will be recorded for safety evaluation of the augmentation therapy. The trends of efficacy will be evaluated by the reduction rate of the Hamilton Depression Rating Scale, the mean change of the Clinical Global Impression Scale, and the Patients Health Questionaire-9 items. Discussion In our study, ATP and PCr will be given by intravenous infusion. Thus patients will be hospitalized for the initial 2 weeks for safety concern. Hospitalization will be an impact factor for the recruitment, participation, drop-out, efficacy, results, etc. The evaluation of our feasibility outcomes, study setting, safety of augmentation therapy and possible efficacy trends among groups, will facilitate a full-scale trial design and sample size calculation. Trial registration NCT03138681. Registered on 3 May 2017. First patient: 4 May 2017.

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Keywords: brexanolone; allopregnanolone (3 ,5 -THP); postpartum depression; fast-acting antidepressant; GABAA receptor; 5 -reduced steroids; 5 -reductase; 3 -HSD EN brexanolone allopregnanolone (3 ,5 -THP) postpartum depression fast-acting antidepressant GABAA receptor 5 -reduced steroids 5 -reductase 3 -HSD 1 6 6 05/18/20 20200514 NES 200514 Introduction Allopregnanolone, today best known as brexanolone and marketed as Zulresso™ for the treatment of postpartum depression is part of only two recently Food and Drug Administration (FDA)-approved fast-acting antidepressants, with esketamine nasal spray, an NMDA receptor antagonist used in treatment-resistant depression with suicidality being the other ([1]). Altogether, stressful condition, hormonal changes, pharmacological treatment (e.g., finasteride, oral contraceptives) may coordinately change GABA SB A sb receptor expression resulting in alterations in receptor function underlying mood disorders. However, it still remains to be clarified the precise treatment targets, including levels of endogenous allopregnanolone, verify altered biosynthetic enzyme expression/function, and GABA SB A sb receptor assembly modifications pre, during, and post-brexanolone treatment. GABA SB A sb receptor expression and neurosteroid biosynthesis in post-partum depression and in general in mood disorders remains underinvestigated. [Extracted from the article]

Major Depressive Disorder (MDD) is a highly debilitating disorder characterized by a persistent feeling of sadness and anhedonia. Traditional antidepressants have a delayed onset of action and lack of efficacy in up to one third of patients, leading to treatment resistant depression (TRD). Recent years have witnessed a revolutionary treatment of TRD with the introduction of the fast-acting antidepressant ketamine. However, ketamine's mechanisms of action are still poorly understood. Here, we used the chronic mild stress animal model of depression on male rats to investigate the involvement of neurotrophic signaling pathways in stress vulnerability/resilience and fast antidepressant response/non-response to acute subanesthetic ketamine. We performed our analysis on both the hippocampus and the prefrontal cortex, two brain areas implicated in stress-related disorders, considering different subcellular fractions. We measured the activation by phosphorylation of protein kinase B (AKT), extracellular signal-regulated kinases (ERKs), glycogen synthase kinase-3 beta (GSK3 β), mammalian target of rapamycin (mTOR), and eukaryotic elongation factor 2 (eEF2), key effectors in the regulation of neuroplasticity and glutamatergic transmission which were previously associated to ketamine's fast antidepressant effect. We showed here for the first time that both stress and ketamine induced brain area and subcellular fraction specific changes in these pathways. Our study represents the first attempt to identify molecular mechanisms underlying the response/non-response to ketamine in an animal model of depression. This approach could give a crucial contribution to the study of etiopathogenetic mechanisms as well as to the identification of novel targets for the development of innovative therapeutic strategies. [Display omitted] • Sucrose preference test allowed to classify the rats stress resilient and vulnerable. • Sucrose preference test allowed to classify the rats ketamine responder/non-responder. • Stress and ketamine induced brain-area and subcellular fraction-specific changes. • Neurotrophic signaling cascades are selectively activated in ketamine responder rats. [ABSTRACT FROM AUTHOR]

Background: Major depressive disorder (MDD) is a common psychiatric disorder. With systematic antidepressant treatment, 50-75% of patients have a treatment response but require 4-6 weeks to have their symptoms alleviated. Therefore, researchers anticipate the development of novel fast-acting antidepressants. Previous studies have revealed that the decrease of bio-energetic metabolism may contribute to the occurrence of depression, while our team has found adenosine triphosphate (ATP) and phosphocreatine (PCr) to be fast-acting antidepressants in the depressed-animal model. ATP and PCr have already been widely prescribed clinically as energy supplements for cells. This will be the first clinical attempt of the intravenous administration of ATP and PCr combined with orally administered fluoxetine in MDD.Methods: This is a single-center, randomized, double-blind, placebo-controlled pilot study. A total of 42 patients will be divided randomly into three groups. Patients will receive an intravenous administration of ATP or PCr or saline twice daily combined with orally administered fluoxetine (20 mg/day) for the first 2 weeks and fluoxetine monotherapy for the following 4 weeks. Follow-up assessment will be completed at week 10. Feasibility outcomes will include percentages of patient eligibility, intention to use medication, willingness to participate, drug adherence, completion of the scheduled assessment, retention, drop-out, etc. Physical examination results, Side Effect Rating Scale, adverse events, results from blood tests, electroencephalogram, and electrocardiograph will be recorded for safety evaluation of the augmentation therapy. The trends of efficacy will be evaluated by the reduction rate of the Hamilton Depression Rating Scale, the mean change of the Clinical Global Impression Scale, and the Patients Health Questionaire-9 items.Discussion: In our study, ATP and PCr will be given by intravenous infusion. Thus patients will be hospitalized for the initial 2 weeks for safety concern. Hospitalization will be an impact factor for the recruitment, participation, drop-out, efficacy, results, etc. The evaluation of our feasibility outcomes, study setting, safety of augmentation therapy and possible efficacy trends among groups, will facilitate a full-scale trial design and sample size calculation.Trial Registration: NCT03138681 . Registered on 3 May 2017. First patient: 4 May 2017. [ABSTRACT FROM AUTHOR]

Background The volatile anesthetic isoflurane may exert a rapid and long-lasting antidepressant effect in patients with medication-resistant depression. The mechanism underlying the putative therapeutic actions of the anesthetic have been attributed to its ability to elicit cortical burst suppression, a distinct EEG pattern with features resembling the characteristic changes that occur following electroconvulsive therapy. It is currently unknown whether the antidepressant actions of isoflurane are shared by anesthetics that do not elicit cortical burst suppression. Methods In vivo electrophysiological techniques were used to determine the effects of isoflurane and halothane, 2 structurally unrelated volatile anesthetics, on cortical EEG. The effects of anesthesia with either halothane or isoflurane were also compared on stress-induced learned helplessness behavior in rats and mice. Results Isoflurane, but not halothane, anesthesia elicited a dose-dependent cortical burst suppression EEG in rats and mice. Two hours of isoflurane, but not halothane, anesthesia reduced the incidence of learned helplessness in rats evaluated 2 weeks following exposure. In mice exhibiting a learned helplessness phenotype, a 1-hour exposure to isoflurane, but not halothane, reversed escape failures 24 hours following burst suppression anesthesia. Conclusions These results are consistent with a role for cortical burst suppression in mediating the antidepressant effects of isoflurane. They provide rationale for additional mechanistic studies in relevant animal models as well as a properly controlled clinical evaluation of the therapeutic benefits associated with isoflurane anesthesia in major depressive disorder. [ABSTRACT FROM AUTHOR]

The available treatments for depression have substantial limitations, including low response rates and substantial lag time before a response is achieved. We applied deep brain stimulation (DBS) to the lateral habenula (LHb) of two rat models of depression (Wistar Kyoto rats and lipopolysaccharide-treated rats) and observed an immediate (within seconds to minutes) alleviation of depressive-like symptoms with a high-response rate. Simultaneous functional MRI (fMRI) conducted on the same sets of depressive rats used in behavioral tests revealed DBS-induced activation of multiple regions in afferent and efferent circuitry of the LHb. The activation levels of brain regions connected to the medial LHb (M-LHb) were correlated with the extent of behavioral improvements. Rats with more medial stimulation sites in the LHb exhibited greater antidepressant effects than those with more lateral stimulation sites. These results indicated that the antidromic activation of the limbic system and orthodromic activation of the monoaminergic systems connected to the M-LHb played a critical role in the rapid antidepressant effects of LHb-DBS. This study indicates that M-LHb-DBS might act as a valuable, rapid-acting antidepressant therapeutic strategy for treatment-resistant depression and demonstrates the potential of using fMRI activation of specific brain regions as biomarkers to predict and evaluate antidepressant efficacy., Competing Interests: GL, BB, PW, PQ, ML, YL, CT, KZ, BZ, TJ, ZL, XD No competing interests declared, (© 2023, Li et al.)

Kinase-mediated signaling cascades regulate a number of different molecular mechanisms involved in cellular homeostasis, and are viewed as one of the most common intracellular processes that are robustly dysregulated in the pathophysiology of mood disorders such as depression. Newly emerged, rapid acting antidepressants are able to achieve therapeutic improvement, possibly in part, through stimulating activity of kinase-dependent signaling pathways. Thus, advancements in our understanding of how kinases may contribute to development and treatment of depression seem crucial. However, current investigations are limited to a single or small number of kinases and are unable to detect novel kinases. Here, we review fast developing kinome profiling approaches that allow identification of multiple kinases and kinase network connections simultaneously, analyze technical limitation and challenges, and discuss their future applications to mood disorders and antidepressant treatment. [ABSTRACT FROM AUTHOR]

The ketamine metabolite (2 R ,6 R)-hydroxynorketamine (HNK) has recently been suggested to exert fast-acting antidepressant-relevant actions and was proposed as an ideal next-generation antidepressant. However, the microRNA-mediated mechanism underlying its effects is still unknown. In the present study, we investigated the role of miR-34a in the prelimbic (PL) cortex during (2 R ,6 R)-HNK-mediated antidepressant-like effects. Male (8–10 weeks old) C57BL/6J mice and primary hippocampal cultured neurons were employed. The tests of forced swimming, tail suspension, sucrose preference, and female urine sniffing were used as indices of depressive-like behaviors. (2 R ,6 R)-HNK enhanced miR-34a levels in a time-dependent manner at 1, 24 h, and 3 days in vitro , in a time-dependent manner at 1 and 24 h, and in a dose-dependent manner at 10 and 30 mg/kg in PL. Pretreatment with NBQX or verapamil blocked (2 R ,6 R)-HNK-enhanced miR-34a expression and NBQX pretreatment blocked AMPA-elevated miR-34a levels in vitro. AAV-miR-34a in PL produced antidepression-behavioral effects and rescued stress-induced depressive-like behaviors. Moreover, PL AAV-miR-34a increased the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) and potentiated evoked excitatory postsynaptic currents (EPSCs). Slices incubated with miR-34a mimic acutely enhanced the frequency and amplitude of mEPSCs in the PL. Intra-PL application of miR-34a rapidly produced antidepression-like effects and reversed stress-evoked depressive-like behaviors. Furthermore, intra-PL application of anti-miR-34a attenuated both systemic and local (2 R ,6 R)-HNK-mediated antidepressant-like actions. Collectively, these results suggest that miR-34a in PL plays an antidepression-like role and contributes to the fast-acting antidepressant-relevant actions of (2 R ,6 R)-HNK. The present study provides evidence for a miR-34a-dependent mechanism underlying the fast-acting antidepressant-like actions of (2 R ,6 R)-HNK, indicating a novel role of PL miR-34a in antidepression. • (2 R ,6 R)-HNK enhanced miR-34a expression in vitro and in vivo. • AAV-miR-34a and miR-34a mimic in PL produced antidepressant-related behavioral and synaptic effects. • Anti-miR-34a in PL attenuated the antidepressant-like actions of (2 R ,6 R)-HNK. [ABSTRACT FROM AUTHOR]

Current understanding of the molecular mechanisms underlying ketamine's antidepressant effect remains largely incomplete. Recent imaging studies provide evidence for ketamine effects on amygdalo-hippocampal. This study in mice aimed to investigate acute proteomic changes after ketamine administration in various brain regions including amygdala and hippocampus. One hour after administration of s-ketamine, the brain-region tissues of interest were dissected out and analyzed using label-free shotgun proteomics. The deep proteomic analysis of amygdala and hippocampus identified 89,526 peptides corresponding to 8000 proteins. The analysis revealed a pronounced proteomic signature of the acute ketamine effect in the amygdala. We anticipate that this proteomic dataset will improve understanding of the mechanism of action of ketamine and identification of new drug targets. Major depressive disorder (MDD) is the leading cause of global disability and it presents a significant challenge to human health. S-ketamine has been proposed as a rapid acting antidepressant and, indeed, the FDA recently approved it for treatment of resistant MDD. However, the mechanism of action of s-ketamine as an antidepressant is still elusive. In this context, we investigated the short-term proteomic changes after ketamine administration in mouse brain regions previously related to ketamine effects such as amygdala and hippocampus. We anticipate that this proteomic dataset will provide highly useful information to improve our understanding of the mechanism of action of ketamine and identification of new drug targets. Unlabelled Image • The study investigates s-ketamine induced acute proteomic changes in the murine brain. • It presents a comprehenisve coverage of amygdala and hippocampus proteomes. • It reports on a pronounced rapid effect of s-ketamine on amygdala. • It reveals altered levels of Grm5 and GABA α 1 and ß3. • S-ketamine may affect the balance between excitatory and inhibatory signals. [ABSTRACT FROM AUTHOR]

The available medications for the treatment of major depressive disorder have limitations, particularly their limited efficacy, delayed therapeutic effects, and the side effects associated with treatment. These issues highlight the need for better therapeutic agents that provide more efficacious and faster effects for the management of this disorder. Ketamine, an N-methyl-D-aspartate receptor antagonist, is the prototype for novel glutamate-based antidepressants that has been shown to cause a rapid and sustained antidepressant effect even in severe refractory depressive patients. Considering the importance of these findings, several studies have been conducted to elucidate the molecular targets for ketamine's effect. In addition, efforts are under way to characterize ketamine-like drugs. This review focuses particularly on evidence that endogenous glutamatergic neuromodulators may be able to modulate mood and to elicit fast antidepressant responses. Among these molecules, agmatine and creatine stand out as those with more published evidence of similarities with ketamine, but guanosine and ascorbic acid have also provided promising results. The possibility that these neuromodulators and ketamine have common neurobiological mechanisms, mainly the ability to activate mechanistic target of rapamycin and brain-derived neurotrophic factor signaling, and synthesis of synaptic proteins in the prefrontal cortex and/or hippocampus is presented and discussed. [ABSTRACT FROM AUTHOR]