Rapid-onset Antidepressant Effects Research Articles

Pharmacological inhibition of Kir4.1 evokes rapid-onset antidepressant responses.

Major depressive disorder, a prevalent and severe psychiatric condition, necessitates development of new and fast-acting antidepressants. Genetic suppression of astrocytic inwardly rectifying potassium channel 4.1 (Kir4.1) in the lateral habenula ameliorates depression-like phenotypes in mice. However, Kir4.1 remains an elusive drug target for depression. Here, we discovered a series of Kir4.1 inhibitors through high-throughput screening. Lys05, the most potent one thus far, effectively suppressed native Kir4.1 channels while displaying high selectivity against established targets for rapid-onset antidepressants. Cryogenic-electron microscopy structures combined with electrophysiological characterizations revealed Lys05 directly binds in the central cavity of Kir4.1. Notably, a single dose of Lys05 reversed the Kir4.1-driven depression-like phenotype and exerted rapid-onset (as early as 1 hour) antidepressant actions in multiple canonical depression rodent models with efficacy comparable to that of (S)-ketamine. Overall, we provided a proof of concept that Kir4.1 is a promising target for rapid-onset antidepressant effects.

Subcutaneous ketamine infusion in palliative patients for major depressive disorder (SKIPMDD)-Phase II single-arm open-label feasibility study.

Ketamine at subanaesthetic dosages (≤0.5mg/kg) exhibits rapid onset (over hours to days) antidepressant effects against major depressive disorder in people who are otherwise well. However, its safety, tolerability and efficacy are not known for major depressive disorder in people with advanced life-limiting illnesses. To determine the feasibility, safety, tolerability, acceptability and any antidepressant signal/activity to justify and inform a fully powered study of subcutaneous ketamine infusions for major depressive disorder in the palliative setting. This was a single arm, open-label, phase II feasibility study (Australian New Zealand Clinical Trial Registry Number-ACTRN12618001586202). We recruited adults (≥ 18-years-old) with advanced life-limiting illnesses referred to four palliative care services in Sydney, Australia, diagnosed with major depressive disorder from any care setting. Participants received weekly subcutaneous ketamine infusion (0.1-0.4mg/kg) over two hours using individual dose-titration design. Outcomes assessed were feasibility, safety, tolerability and antidepressant activity. Out of ninety-nine referrals, ten participants received ketamine and were analysed for responses. Accrual rate was 0.54 participants/month across sites with 50% of treated participants achieving ≥ 50% reduction in baseline Montgomery-Åsberg Depression Rating Scale, meeting feasibility criteria set a priori. There were no clinically relevant harms encountered. A future definitive trial exploring the effectiveness of subcutaneous infusion of ketamine for major depressive disorder in the palliative care setting may be feasible by addressing identified study barriers. Individual dose-titration of subcutaneous ketamine infusions over two hours from 0.1mg/kg can be well-tolerated and appears to produce transient antidepressant signals over hours to days.

Exosome-sheathed ROS-responsive nanogel to improve targeted therapy in perimenopausal depression

The development of natural membranes as coatings for nanoparticles to traverse the blood-brain barrier (BBB) presents an effective approach for treating central nervous system (CNS) disorders. In this study, we have designed a nanogel loaded with PACAP and estrogen (E2), sheathed with exosomes and responsive to reactive oxygen species (ROS), denoted as HA NGs@exosomes. The objective of this novel design is to serve as a potent drug carrier for the targeted treatment of perimenopausal depression. The efficient cellular uptake and BBB penetration of HA NGs@exosomes has been demonstrated in vitro and in vivo. Following intranasal intervention with HA NGs@exosomes, ovariectomized mice under chronic unpredictable mild stress (CUMS) have shown improved behavioral performance, indicating that HA NGs@exosomes produced a rapid-onset antidepressant effect. Moreover, HA NGs@exosomes exhibit notable antioxidant and anti-inflammatory properties and may regulate the expression of pivotal proteins in the PACAP/PAC1 pathway to promote synaptic plasticity. Our results serve as a proof-of-concept for the utility of exosome-sheathed ROS-responsive nanogel as a promising drug carrier for the treatment of perimenopausal depression.Graphical

Sigma-1 receptor agonist properties that mediate the fast-onset antidepressant effect of hypidone hydrochloride (YL-0919)

The most intriguing characteristic of the sigma-1 receptor is its ability to regulate multiple functional proteins directly via protein-protein interactions, giving the sigma-1 receptor the powerful ability to regulate several survival and metabolic functions in cells, fine tune neuronal excitability, and regulate the transmission of information within brain circuits. This characteristic makes sigma-1 receptors attractive candidates for the development of new drugs. Hypidone hydrochloride (YL-0919), a novel structured antidepressant candidate developed in our laboratory, possess a selective sigma-1 receptor agonist profile, as evidenced by molecular docking, radioligand receptor binding assays, and receptor functional experiments. In vivo studies have revealed that YL-0919 elicits a fast-onset antidepressant activity (within one week) that can be attenuated with pretreatment of the selective sigma-1 receptor antagonist, BD-1047. Taken together, the findings of the current study suggest that YL-0919 activates the sigma-1 receptor to partially mediate the rapid onset antidepressant effects of YL-0919. Thus, YL-0919 is a promising candidate as a fast-onset antidepressant that targets the sigma-1 receptor.

Rapid onset brain plasticity at novel pharmacologic targets hypothetically drives innovations for rapid onset antidepressant actions.

Numerous new agents with rapid onset antidepressant effects are entering clinical trials and clinical practice. Studies focus on either first-line treatment of major depressive disorder or on patients whose major depressive disorder is resistant to prior antidepressant drugs. Novel agents target three very different central nervous system sites: as antagonists of N-methyl-d-aspartate (NMDA) glutamate receptors, as positive allosteric modulators (PAMs) of gamma amino butyric acid (GABA) A neurosteroid and benzodiazepine receptor sites, and as psychedelic agonists of serotonin 2A/2C receptors. Onset of antidepressant action is rapid, sometimes after only one dose whereas traditional agents for depression take several days to weeks to have an antidepressant effect. Although the direct molecular targets of these three classes of agents with rapid antidepressant onset are quite diverse and not clearly related to each other, analysis of the downstream effects of all these agents show that all are "plastogens," namely agents that trigger rapid onset of neuroplasticity that correlates with their rapid onset of antidepressant clinical action. The GABA A PAMs and some of the NMDA antagonists induce neuroplasticity without notable changes in mental status and can be designated "neuroplastogens." Some NMDA antagonists cause mental dissociation, and the psychedelics cause psychotomimetic/hallucinatory experiences and can be designated "psychoplastogens." A great debate exists whether psychoplastogens are effective because of their ability to acutely alter mental state, or whether these acute mental states are unwanted behavioral toxicity. The promise of numerous novel agents with rapid acting antidepressant action and neuroplasticity is set to transform the treatment of major depressive disorder.

Efficacy and safety of nitrous oxide for patients with treatment-resistant depression, a randomized controlled trial

Nitrous oxide (N2O), an N-methyl-D-aspartate glutamate receptor antagonist, has demonstrated a rapid-onset antidepressant effect for treatment-resistant depression (TRD) preliminarily in the United States. This study aimed to test the efficacy and safety of N2O for TRD patients in China. In this double-blinded, placebo-controlled trial, 44 patients with TRD were randomized to receive a one-hour inhalation of a mixture of either 50% N2O/50% oxygen (N2O group) or 50% air/50% oxygen (placebo group). The primary outcome was the change on the 17-item Hamilton Depression Rating Scale (HDRS-17) over a course of two weeks. Using modified intention-to-treat analysis, the between group difference was found in the HDRS-17 score at two hours and 24 h after inhalation treatment, while no significant difference was found in week one and week two. Patients receiving N2O reported a significantly higher number of adverse events. All the adverse events lasted for no more than 24 h. No serious adverse events were reported. A single inhalation of 50% N2O effectively alleviates depression in patients with TRD in China. The efficacy lasts for no more than one week. N2O is safe for patients with TRD.

Time of day influences stress hormone response to ketamine.

Over 50% of depressed patients show hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. Conventional therapy takes weeks to months to improve symptoms. Ketamine has rapid onset antidepressant effects. Yet its action on HPA axis activity is poorly understood. Here, we measured the corticosterone (CORT) response to ketamine administered at different times of day in the Wistar-Kyoto (WKY) rat. In male rats, blood was collected every 10min for 28 h using an automated blood sampling system. Ketamine (5/10/25 mg · kg) was infused through a subcutaneous cannula at two time points-during the active and inactive period. CORT levels in blood were measured in response to ketamine using a radioimmunoassay. WKY rats displayed robust circadian secretion of corticosterone and was not overly different to Sprague Dawley rats. Ketamine (all doses) significantly increased CORT response at both infusion times. However, a dose dependent effect and marked increase over baseline was observed when ketamine was administered during the inactive phase. Ketamine has a robust and rapid effect on HPA axis function. The timing of ketamine injection may prove crucial for glucocorticoid-mediated action in depression.

Pharmacological Comparative Characterization of REL-1017 (Esmethadone-HCl) and Other NMDAR Channel Blockers in Human Heterodimeric N-Methyl-D-Aspartate Receptors.

Excessive Ca2+ currents via N-methyl-D-aspartate receptors (NMDARs) have been implicated in many disorders. Uncompetitive NMDAR channel blockers are an emerging class of drugs in clinical use for major depressive disorder (MDD) and other neuropsychiatric diseases. The pharmacological characterization of uncompetitive NMDAR blockers in clinical use may improve our understanding of NMDAR function in physiology and pathology. REL-1017 (esmethadone-HCl), a novel uncompetitive NMDAR channel blocker in Phase 3 trials for the treatment of MDD, was characterized together with dextromethorphan, memantine, (±)-ketamine, and MK-801 in cell lines over-expressing NMDAR subtypes using fluorometric imaging plate reader (FLIPR), automated patch-clamp, and manual patch-clamp electrophysiology. In the absence of Mg2+, NMDAR subtypes NR1-2D were most sensitive to low, sub-μM glutamate concentrations in FLIPR experiments. FLIPR Ca2+ determination demonstrated low μM affinity of REL-1017 at NMDARs with minimal subtype preference. In automated and manual patch-clamp electrophysiological experiments, REL-1017 exhibited preference for the NR1-2D NMDAR subtype in the presence of 1 mM Mg2+ and 1 μM L-glutamate. Tau off and trapping characteristics were similar for (±)-ketamine and REL-1017. Results of radioligand binding assays in rat cortical neurons correlated with the estimated affinities obtained in FLIPR assays and in automated and manual patch-clamp assays. In silico studies of NMDARs in closed and open conformation indicate that REL-1017 has a higher preference for docking and undocking the open-channel conformation compared to ketamine. In conclusion, the pharmacological characteristics of REL-1017 at NMDARs, including relatively low affinity at the NMDAR, NR1-2D subtype preference in the presence of 1 mM Mg2+, tau off and degree of trapping similar to (±)-ketamine, and preferential docking and undocking of the open NMDAR, could all be important variables for understanding the rapid-onset antidepressant effects of REL-1017 without psychotomimetic side effects.

Pharmacogenetic and drug interaction aspects on ketamine safety in its use as antidepressant ‐ implications for precision dosing in a global perspective

Ketamine and its enantiomer S-ketamine (esketamine) are known to produce rapid-onset antidepressant effects in major depression. Intranasal esketamine has recently come onto the market as an antidepressant. Besides experience from short-term use in anaesthesia and analgesia, the experience with ketamine as long-term medication is rather low. The use of ketamine and esketamine is limited due to potential neurotoxicity, psychotomimetic side effects, potential abuse and interindividual variability in treatment response including cessation of therapy. Therefore, taking a look at individual patient risks and potential underlying variability in pharmacokinetics may improve safety and dosing of these new antidepressant drugs in clinical practice. Differential drug metabolism due to polymorphic cytochrome P450 (CYP) enzymes and gene-drug interactions are known to influence the efficacy and safety of many drugs. Ketamine and esketamine are metabolized by polymorphic CYP enzymes including CYP2B6, CYP3A4, CYP2C9 and CYP2A6. In antidepressant drug therapy, usually multiple drugs are administered which are substrates of CYP enzymes, increasing the risk for drug-drug interactions. We reviewed the potential impact of polymorphic CYP variants and common drug-drug interactions in antidepressant drug therapy affecting ketamine pharmacokinetics, and the role for dose optimization. The use of ketamine or intranasal esketamine as antidepressants demands a better understanding of the factors that may impact its metabolism and efficacy in long-term use. In addition to other clinical and environmental confounders, prior information on the pharmacodynamic and pharmacokinetic determinants of response variability to ketamine and esketamine may inform on dose optimization and identification of individuals at risk of adverse drug reactions.

Rapid-Onset Antidepressant-Like Effect of Nelumbinis semen in Social Hierarchy Stress Model of Depression.

Depression is a disease with increasing prevalence worldwide, and it is necessary to develop a therapeutic agent with better efficacy than existing antidepressant drugs. Antidepressants that act on the glutamatergic nervous system, such as ketamine, have a rapid-onset antidepressant effect and are effective against treatment-resistant depression. However, because of the addictive potential of ketamine, alternative substances without psychological side effects are recommended. In particular, many natural compounds have been tested for their antidepressant effects. The antidepressant effects of Nelumbinis semen (NS) have been tested in many studies, along with the various actions of NS on the glutamatergic system. Thus, it was expected that NS might have a rapid-onset antidepressant effect. To test the antidepressant potential, despair and anhedonic behaviors were measured after administering NS to mice exposed to social hierarchy stress (SHS), and biochemical changes in the prefrontal cortex and hippocampus were analyzed. NS reduced despair-like responses in the forced swim test and tail suspension test. Mice exposed to SHS showed depression-like responses such as increased despair, reduced hedonia, and an anxiety-like response in the novelty suppressed feeding test. NS, but not fluoxetine, improved those depression-like behaviors after acute treatment, and NBQX, an AMPA receptor blocker, inhibited the antidepressant-like effects of NS. The antidepressant-like effect of NS was related to enhanced phosphorylation of mTOR in the prefrontal cortex and dephosphorylation of GluR1 S845 in the hippocampus. Since NS has shown antidepressant-like potential in a preclinical model, it may be considered as a candidate for the development of antidepressants in the future.

Prophylactic efficacy of ketamine, but not the low-trapping NMDA receptor antagonist AZD6765, against stress-induced maladaptive behavior and 4E-BP1-related synaptic protein synthesis impairment

Ketamine enhances the resilience against stress-induced depressive-like behavior, but its prophylactic efficacy in anxiety-related behaviors remains to be elucidated. Moreover, there is a need for developing novel preventive strategies against depressive- and anxiety-like behavior. AZD6765, a low-trapping NMDA receptor antagonist, shares with ketamine common molecular targets and produces rapid-onset antidepressant effects, suggesting that it could be a prophylactic agent. Therefore, this study investigated the prophylactic effect of ketamine against the depressive- and anxiety-like behavior induced by chronic restraint stress (2 h/day, for 10 days) in mice. We also investigated if AZD6765 exerts a resilience-enhancing response against these maladaptive behaviors. The contribution of 4E-BP1-related synaptic proteins synthesis (PSD-95/GluA1) in the possible pro-resilience efficacy of ketamine and AZD6765 was investigated. A single administration of ketamine (5 mg/kg, i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.), given 1 week before the stress protocol, was effective in preventing stress-induced depressive-like behavior in the tail suspension test and splash test. Ketamine administered at 1 and 5 mg/kg (i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.), prevented stress-induced anxiety-related self-grooming alterations. Stress-induced reduction on 4E-BP1 phosphorylation and PSD-95 and GluA1 immunocontent in the prefrontal cortex was prevented by ketamine (5 mg/kg, i.p.), but not AZD6765 (1 or 5 mg/kg, i.p.). The results indicate that ketamine, but not AZD6765, exerts a pro-resilience response against stress-induced maladaptive behavior, reinforcing that it could be a prophylactic agent to manage individuals at-risk to develop MDD and anxiety.

#3095 Rapid anti-obsessive treatments of obsessive-compulsive disorder: reviewing effects of ketamine in OCD

Objectives/AimsObsessive-Compulsive Disorder (OCD) is a common neuropsychiatric condition characterised by persistent endogenous repetitive and intrusive anxiogenic thoughts, feelings, or images often followed by anxiolytic mental or physical actions. Serotonin reuptake inhibitors (SRIs) are the mainstay of OCD treatment, used both as first line (SSRIs) and second line (Clomipramine) approaches. Despite their effectiveness in treatment of OCD, their anti-obsessive effects only start at eight to 12 weeks into treatment (Pittenger & Bloch, 2014), leaving an effectiveness time gap between diagnosis and treatment. Various treatment strategies have been tried but there is no consensus on the most effective approach. A single pharmacological agent with rapid anti-obsessive action would be an ideal candidate to manage this treatment gap. One such agent may be ketamine with its novel mechanism of action.Ketamine is assumed to increase neuroplasticity by synthesising neurotrophins in the cortex and has demonstrated to have rapid-onset anti-depressant effects (Bjrkholm & Monteggia, 2016). We reviewed the state of evidence for similar rapidly emerging anti- obsessive effects and report our findings here.MethodsEmbase, MEDLINE(R), and PsycINFO were searched to identify studies investigating rapid anti-obsessive effects of ketamine in humans, available in English. ClinicalTrials.org was further searched for grey literature. Other reviews were excluded.Results181 studies were identified after deduplication of which nine studies met inclusion criteria. Eight studies revealed rapid anti-obsessive effects, five of which display statistical significance. Combined, OCD scores decline by approximately 49.7% during the first hour following intravenous ketamine administration. Furthermore, a significant reduction of depressive symptoms and suicidality were reported in studies further investigating comorbid depression. Contrary to depression scores, anti-obsessive effects were not sustained. OCD scores increased within three hours post-administration and reversed back to baseline within seven days. One trial reported an extended length and margin of effect when combined with cognitive behavioural therapy.All studies were of small scale as the literature search primarily yielded pilot trials and case reports, suggesting statistical imprecision and reflecting the topics novelty.ConclusionsOur review points out the presence of preliminary research evidence to support the presence of anti-obsessive effects of ketamine and a potential for its usefulness as a rapidly acting intervention for OCD, thereby plugging an important gap in clinical management of OCD. However, as such effects are unsustained, their potential to complement existing pharmacological strategies may be limited.Greater awareness and randomised controlled trials are required before recommending the use of ketamine in OCD treatment.References Bjrkholm C, Monteggia LM. BDNF a key transducer of antidepressant effects. Neuropharmacology 2016;102. doi:10.1016/j.neuropharm.2015.10.034 Pittenger C, Bloch MH. Pharmacological treatment of obsessive-compulsive disorder. The Psychiatric clinics of North America 2014;37(3):375391. doi:10.1016/j.psc.2014.05.006

A systematic review of ketamine for the treatment of depression among older adults

<h3>Introduction</h3> Depression is the second most prevalent mental health disorder among older adults after anxiety disorders. It effects 7% of the general older population globally 5.6% of US older adults. Suicide rates also increase between ages of 60-90 in both men and women around the world. A large body of literature shows increased association of late life depression with increased morbidity and mortality in this age group. Evidence for depression as a risk factor for physical and cognitive decline that results in lower quality of life and function among older adults underlines the importance of early recognition and prompt treatment of this serious condition. The most common modalities currently used for treatment of late life depression include pharmacotherapy, psychotherapy and electroconvulsive therapy (ECT). Pharmacotherapy mostly consists of antidepressants targeting the monoaminergic system. Ketamine has recently emerged as a novel, rapid acting option for treatment resistant depression in adults. Ketamine is a N-methyl-D-aspartate (NMDA) receptor antagonist, which has been used primarily as an anesthetic since the 1960s. In 1990s preclinical studies demonstrated the role of NMDA receptor antagonists in treatment of depression, which was later confirmed in a pilot clinical study. Berman et al administered subanaesthetic doses of Ketamine (0.5mg/kg) vs. placebo to 7 study participants which resulted in robust decreases in Hamilton Depression Rating Scale scores within 4 hours of the infusion in all participants. The effect was sustained for 3 days followed by diminution of the scores and relapse of symptoms. This rapid onset anti-depressant effect of ketamine compared to conventional antidepressants attracted considerable interest and these findings have since been reliably replicated in multiple different studies, using different protocols and routes of administration of ketamine. This systematic review evaluates randomized controlled trials completed in the older adult population with depression to appraise the efficacy and tolerability of ketamine specifically in this population. <h3>Methods</h3> The authors followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) On November 09, 2019 the authors conducted a comprehensive search of multiple databases: PubMed (through November 09, 2019), MEDLINE (Ovid ALL 1946 to November 08, 2019), Embase (Ovid 1974 to 2019 November 08), PsycINFO (Ovid 1806 to October Week 4 2019), Web of Science Core Collection (through November 09, 2019), and Cochrane Central Register of Controlled Trials (Issue 11 of 12, November 2019). The search strategy was filtered for human studies in PubMed, MEDLINE, and Embase using controlled vocabulary terms in the search strategy. On December 13, 2019 an updated search was completed. The search repeated the controlled vocabulary terms and free text terms. <h3>Results</h3> A total of 1699 citations were deduplicated to 1005 and uploaded to Covidence for screening by two separate screeners. Two studies were found to meet the inclusion criteria for this review. The first study showed a significant reduction in depression symptoms with use of repeated subcutaneous ketamine administration among older adults with depression. The second study failed to achieve significance on its primary outcome measure but did show a decrease in MADRS scores with intranasal ketamine. This study also showed a higher response and remission rates in esketamine group when compared to the placebo group. Both the studies showed relapse in symptoms after a week of last treatment, but the benefits were better sustained with repeated treatments. The adverse effects from ketamine generally lasted only lasted a few hours and abated spontaneously without any additional intervention. No cognitive adverse effects were noted in either trial from the use of ketamine. <h3>Conclusions</h3> The current evidence for use of ketamine among older adults with depression indicates some benefits with one positive and one negative trial. Although one of the trails did not achieve significance on primary outcome measure, it still showed benefit of ketamine in reducing depressive symptoms. Both studies show longer sustenance of antidepressant effects at higher doses and with repeated treatments. One of the studies showed better ketamine efficacy in younger old subjects (65 to 74 years) when compared to older old (³75 years) subjects. Ketamine was well tolerated in both studies with adverse-effects being mild and transient. Additionally, there were no negative cognitive effects of ketamine noted among any of the study participants. Based on the limited current evidence, it is our opinion that ketamine shows some benefit in relieving depressive symptoms in older adults. However, there is dearth of randomized controlled trials and we need more well designed studies to arrive at a reliable conclusion regarding ketamine's benefit in treating depression among older adults. <h3>Funding</h3> None

Ketamine Rapidly Enhances Glutamate-Evoked Dendritic Spinogenesis in Medial Prefrontal Cortex Through Dopaminergic Mechanisms

BackgroundKetamine elicits rapid onset antidepressant effects in patients with clinical depression through mechanisms hypothesized to involve the genesis of neocortical dendritic spines and synapses. Yet, the observed changes in dendritic spine morphology usually emerge well after ketamine clearance, raising questions about the link between rapid behavioral effects of ketamine and plasticity. MethodsHere, we used two-photon glutamate uncaging/imaging to focally induce spinogenesis in the medial prefrontal cortex, directly interrogating baseline and ketamine-associated plasticity of deep layer pyramidal neurons in C57BL/6 mice. We combined pharmacological, genetic, optogenetic, and chemogenetic manipulations to interrogate dopaminergic mechanisms underlying ketamine-induced rapid enhancement in evoked plasticity and associated behavioral changes. ResultsWe found that ketamine rapidly enhances glutamate-evoked spinogenesis in the medial prefrontal cortex, with timing that matches the onset of its behavioral efficacy and precedes changes in dendritic spine density. Ketamine increases evoked cortical spinogenesis through dopamine Drd1 receptor (Drd1) activation that requires dopamine release, compensating blunted plasticity in a learned helplessness paradigm. The enhancement in evoked spinogenesis after Drd1 activation or ketamine treatment depends on postsynaptic protein kinase A activity. Furthermore, ketamine’s behavioral effects are blocked by chemogenetic inhibition of dopamine release and mimicked by activating presynaptic dopaminergic terminals or postsynaptic Gαs-coupled cascades in the medial prefrontal cortex. ConclusionsOur findings highlight dopaminergic mediation of rapid enhancement in activity-dependent dendritic spinogenesis and behavioral effects induced by ketamine.

Glycine/NMDA Receptor Pathway Mediates the Rapid-onset Antidepressant Effect of Alkaloids From Trichilia Monadelpha.

Introduction:Major depressive disorder is often associated with suicidal tendencies, and this condition accentuates the need for rapid-acting antidepressants. We previously reported that Alkaloids (ALK) from Trichilia monadelpha possess antidepressant action in acute animal models of depression and that this effect is mediated through the monoamine and L-arginine-NO-cGMP pathways. This study investigated the possible rapid-onset antidepressant effect of ALK from T. monadelpha and its connection with the glycine/NMDA receptor pathway.Methods:The onset of ALK action from T. monadelpha was evaluated using the Open Space Swim Test (OSST), a chronic model of depression. The modified forced swimming and tail suspension tests were used to assess the effect of the ALK on the glycine/NMDA receptor pathway. The Instutute of Cancer Research (ICR) mice were treated with either ALK (30–300 mg/kg, orally [PO]), imipramine (3–30 mg/kg, PO), fluoxetine (3–30 mg/kg, PO), or saline. To identify the role of glycine/NMDA receptor pathway in the effect of ALK, we pretreated mice with a partial agonist of the glycine/NMDA receptor, D-cycloserine (2.5 mg/kg, intraperitoneally [IP]), and an agonist of glycine/NMDA receptor, D-serine (600 mg/kg, IP), before ALK administration.Results:ALK reversed immobility in mice after the second day of drug treatment in the OSST. In contrast, there was a delay in the effects induced by fluoxetine and imipramine. ALK also increased mean swimming and climbing scores in mice. ALK was more efficacious than imipramine and fluoxetine in reducing immobility and increasing distance traveled. It is noteworthy that ALK was less potent than fluoxetine and imipramine. D-cycloserine potentiated mobility observed in the ALK- and fluoxetine-treated mice. In contrast, D-serine decreased mobility in the ALK-treated mice.Conclusion:The study results suggest that ALK from T. monadelpha exhibits rapid antidepressant action in mice, and the glycine/NMDA receptor pathway possibly mediates the observed effect.

Influence of formulation and route of administration on ketamine's safety and tolerability: systematic review.

Ketamine has rapid-onset antidepressant effects in patients with treatment-resistant depression. Common side effects include dissociation (a sense of detachment from reality) and increases in systolic and diastolic blood pressure. The objective of this structured review was to examine the effect of ketamine formulation and route of administration on its pharmacokinetics, safety and tolerability, to identify formulation characteristics and routes of administration that might minimise side effects. This was a structured review of published ketamine pharmacokinetics, safety and tolerability data for any ketamine formulation. The ratio of ketamine:norketamine was calculated from reported Cmax values, as a measure of first pass metabolism. The effect of formulation and route of administration on safety was evaluated by measuring mean changes in systolic blood pressure and tolerability by changes in dissociation ratings. Data were correlated using Spearman's method. A total of 41 treatment arms were identified from 21 publications, and included formulation development studies in healthy volunteers, and studies in clinical populations (patients undergoing anaesthesia, or being treated for pain or depression). Ketamine:norketamine ratios were strongly positively correlated with change in dissociation ratings (r= 0.89) and change in blood pressure (r= 0.96), and strongly negatively correlated with ketamine Tmax (r= - 0.87; p< 0.00001 for all). Ketamine Tmax strongly positively correlated with a change in dissociation ratings (r= - 0.96) and change in blood pressure (r= - 0.99; p< 0.00001 for all). Ketamine formulations that maximize first pass metabolism and delay Tmax will be better tolerated and safer than formulations which lack those characteristics.

Molecular mechanisms for the antidepressant-like effects of a low-dose ketamine treatment in a DFP-based rat model for Gulf War Illness

Exposure to organophosphates (OP) during the First Gulf War is among one of the factors for Gulf War Illness (GWI) development in veterans and it has been challenging to treat GWI symptoms with existing therapies. Ketamine produces a rapid-onset and sustained antidepressant response, but there is no evidence whether ketamine treatment is effective for GWI depression. Repeated, low-dose exposure to diisopropyl fluorophosphate (DFP) mimic Gulf War related OP exposures and produces a chronic depressive state in rats. In this study, DFP-exposed rats treated with ketamine (10 mg/kg, i.p.) exhibited antidepressant-like effect on the Forced Swim Test at 1-h. This effect persisted at 24-h post ketamine, a time-point by which it is eliminated from the brain suggesting involvement of mechanisms that affect long-term synaptic plasticity. Western blot analysis showed significantly lower Brain-Derived Neurotrophic Factor (BDNF) levels in DFP rat brains. Ketamine produced a nonsignificant increase in BDNF expression at 1-h but produced a larger, significant (2.2-fold) increase at 24-h in DFP rats. We previously reported chronic hippocampal calcium elevations ([Ca2+]i) in DFP rats. Ketamine-treated DFP rats exhibited significantly lower [Ca2+]i at 1-h but not at 24-h. Interestingly, treatment with ANA-12, a TrkB-BDNF receptor antagonist, in DFP rats blunted ketamine’s antidepressant-like effect at 24-h but not at 1-h. These experiments suggest that in a rat model of DFP-induced depression, inhibition of the NMDAR-Ca2+ contributes to the rapid-onset antidepressant effects of ketamine while the antidepressant actions that persisted at 24-h post ketamine administration involve upregulation of BDNF signaling.

L-Carnosine combination therapy for major depressive disorder: A randomized, double-blind, placebo-controlled trial

BackgroundEvidence for antidepressant effects of L-Carnosine was shown in some experimental studies. In this study we tried to evaluate the efficacy and tolerability of L-Carnosine combination therapy in treatment of patients with major depressive disorder (MDD). MethodsFifty-eight patients with MDD (DSM-V) and Hamilton Depression Rating Scale (HAM-D) score ≥ 19 were randomized to receive either 400 mg twice daily L-Carnosine or placebo in addition to citalopram (maximum dosage of 40 mg/day) for six weeks in a randomized double-blind, and placebo-controlled study. Patients were assessed using the HAM-D scale at baseline and weeks 2, 4, and 6. ResultsFifty-two patients completed the trial. General linear model repeated measure showed significant difference for time × treatment on HAM-D score [F = 3.17, df = 2.39, p-value = 0.03]. Significantly greater improvement was detected in HAM-D score of the L-Carnosine group compared with the placebo group from baseline to weeks 2, 4 and 6 [Ps = 0.013, 0.028 and 0.023; respectively]. Patients in the L-Carnosine group experienced significantly greater response and remission rate than the placebo group [Ps = 0.023 and 0.012; respectively]. There was no significant difference between the two groups in baseline parameters and frequency of side effects. LimitationsShort follow-up period and small population size were two important limitations of this study. ConclusionsL-Carnosine combination therapy with citalopram can effectively improve symptoms of patients with major depressive disorder. Rapid-onset antidepressant effects of L-Carnosine were also shown which need further investigation.

The emergence of ketamine as a novel treatment for posttraumatic stress disorder.

A serious lack of effective pharmacotherapeutic interventions for posttraumatic stress disorder (PTSD) raises the urgent need for the development of novel treatments. Ketamine-a noncompetitive glutamate N-methyl-d-aspartate (NMDA) receptor antagonist in use for decades as an anesthetic and analgesic agent-has more recently been demonstrated to have rapid-onset antidepressant effects in patients with treatment-resistant depression (TRD). In the present review of ketamine as an emerging novel pharmacotherapeutic intervention for chronic PTSD, we discuss findings from the first proof-of-concept, randomized clinical trial (RCT) of single-dose intravenous ketamine in patients with chronic PTSD, as well as open-label studies and current practice. We introduce ongoing RCTs investigating the efficacy of repeated ketamine infusions in rapidly reducing symptoms and maintaining improvement in samples of individuals with PTSD stemming from civilian and military traumas. Additionally, we discuss mixed findings from published reports on ketamine administration in the acute aftermath of trauma. Studies in animal models of chronic stress have investigated molecular mechanisms underlying ketamine's effects, generating a shift in the conceptualization of PTSD as a disorder of impaired neural connectivity. We review animal studies examining the potential of ketamine to modify the expression of fear by altering memory reconsolidation or enhancing fear extinction, as well as others investigating ketamine administration prophylactically prior to stress exposure. We introduce the need for additional study in humans to evaluate whether ketamine might enhance the efficacy of psychotherapeutic interventions in individuals with chronic PTSD, harnessing a window of ketamine-induced neuroplasticity. While research on ketamine for PTSD is still in its early stages, it brings about the promise of novel and more effective treatments for this disabling condition.

TAK-137, an AMPA receptor potentiator with little agonistic effect, produces antidepressant-like effect without causing psychotomimetic effects in rats

Ketamine produces a rapid-onset antidepressant effect in patients with treatment-resistant depression (TRD), although it concurrently causes undesirable psychotomimetic side effects. Accumulating evidence suggests that ketamine produces antidepressant effects via activation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-R), with consequent activation of the mammalian target of rapamycin (mTOR) pathway and up-regulation of brain-derived neurotrophic factor (BDNF). We previously reported that TAK-137, an AMPA-R potentiator with little agonistic effect, had potent procognitive effects with lower risks of bell-shaped dose-response and seizure induction. In this study, we characterized the potential of TAK-137 as a novel antidepressant in rats. In rat primary cortical neurons, TAK-137 increased the phosphorylated form of Akt, extracellular signal-regulated kinase, mTOR, and p70S6 kinase, and dose-dependently increased the expression level of BDNF protein. The antidepressant-like effects of ketamine and TAK-137 were assessed on the day after final administration using the novelty-suppressed feeding test in rats. A single intraperitoneal administration of ketamine shortened the latency to feed. Under these conditions, oral administration of TAK-137 for 3 days shortened the feeding latency. Ketamine induced hyperlocomotion and reduced prepulse inhibition, which may be associated with psychotomimetic effects, while TAK-137 did not. TAK-137 may be a safer and rapid-onset therapeutic drug for the treatment of major depressive disorder, including TRD.