Memantine reduces mania-like symptoms in animal models

Effects of memantine on mania-like phenotypes exhibited by Drosophila Shaker mutants

INTRODUCTION

Increased glutamate levels and electrolytic fluctuations have been observed in acutely manic patients. Despite some efficacy of the non-competitive NMDA receptor antagonist memantine (Mem), such as antidepressant-like and mood-stabilizer drugs in clinical studies, its specific mechanisms of action are still uncertain. The present study aims to better characterize the Drosophila melanogaster fly Shaker mutants (SH), as a translational model of manic episodes within bipolar disorder in humans, and to investigate the potential anti-manic properties of Mem.

METHODS AND RESULTS

Our findings showed typical behavioral abnormalities in SH, which mirrored with the overexpression of NMDAR-NR1 protein subunit, matched well to glutamate up-regulation. Such molecular features were associated to a significant reduction of SH brain volume in comparison to Wild Type strain flies (WT). Here we report on the ability of Mem treatment to ameliorate behavioral aberrations of SH (similar to that of Lithium), and its ability to reduce NMDAR-NR1 over-expression.

CONCLUSIONS

Our results show the involvement of the glutamatergic system in the SH, given the interaction between the Shaker channel and the NMDA receptor, suggesting this model as a promising tool for studying the neurobiology of bipolar disorders. Moreover, our results show Mem as a potential disease-modifying therapy, providing insight on new mechanisms of action.

CYFIP1 Dosages Exhibit Divergent Behavioral Impact via Diametric Regulation of NMDA Receptor Complex Translation in Mouse Models of Psychiatric Disorders

BACKGROUND

Gene dosage imbalance caused by copy number variations (CNVs) is a prominent contributor to brain disorders. In particular, 15q11.2 CNV duplications and deletions have been associated with autism spectrum disorder and schizophrenia, respectively. The mechanism underlying these diametric contributions remains unclear.

METHODS

We established both loss-of-function and gain-of-function mouse models of Cyfip1, one of four genes within 15q11.2 CNVs. To assess the functional consequences of altered CYFIP1 levels, we performed systematic investigations on behavioral, electrophysiological, and biochemical phenotypes in both mouse models. In addition, we utilized RNA immunoprecipitation sequencing (RIP-seq) analysis to reveal molecular targets of CYFIP1 in vivo.

RESULTS

Cyfip1 loss-of-function and gain-of function mouse models exhibited distinct and shared behavioral abnormalities related to autism spectrum disorder and schizophrenia. RIP-seq analysis identified messenger RNA targets of CYFIP1 in vivo, including postsynaptic NMDA receptor (NMDAR) complex components. In addition, these mouse models showed diametric changes in levels of postsynaptic NMDAR complex components at synapses because of dysregulated protein translation, resulting in bidirectional alteration of NMDAR-mediated signaling. Importantly, pharmacological balancing of NMDAR signaling in these mouse models with diametric Cyfip1 dosages rescues behavioral abnormalities.

CONCLUSIONS

CYFIP1 regulates protein translation of NMDAR and associated complex components at synapses to maintain normal synaptic functions and behaviors. Our integrated analyses provide insight into how gene dosage imbalance caused by CNVs may contribute to divergent neuropsychiatric disorders.

No NLRP3 Inflammasome Expression in the Ouabain Animal Model of Bipolar Disorder

Introduction

Inflammation is believed to play a role in both bipolar illness and unipolar depression. Markers of inflammation are elevated during acute mood episodes. Specifically, gene expressions of the nucleotide-binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3)-related proteins in peripheral blood have been purported to be upregulated in patients with bipolar disorder. We examined the elaboration of NLRP3 in the ouabain animal model of bipolar disorder. 

Methods

The frontal cortex, hippocampus, and basal ganglia tissue from young, male Sprague-Dawley rats who received intracerebroventricular (ICV) ouabain as a model of bipolar disorder or artificial cerebrospinal fluid (aCSF) were examined for NLRP3 utilizing protein immunoblot (Western) analysis. 

Results

We could not demonstrate any NLRP3 in rat brain, but NLRP3 was detected in control from mouse brain and lung.

Discussion

This study demonstrates that the manifestation of manic behavior in rats treated with ICV ouabain is not accompanied by elaboration of NLRP3 inflammasome. This raises the question of the primacy of inflammation in the pathophysiology of mania. If these findings are reproduced in this and other animal models of mania, they would raise important questions about whether inflammation is a primary or secondary phenomenon in the brains of subjects with bipolar disorder.

Advances in the psychopharmacotherapy of bipolar disorder type I

INTRODUCTION

Research into the pharmacologic management of bipolar type I illness continues to progress.

AREAS COVERED

Randomized clinical trials performed with type I bipolar disorder in the years 2015 to August 2020 are reviewed. There are new indications for the use of cariprazine, for bipolar mania and depression, and a long-acting injectable formulation of aripiprazole has also been approved for relapse prevention in bipolar illness. Most of the randomized clinical trials are effectiveness studies.

EXPERT OPINION

Over the 20 years from 1997 through 2016, the use of lithium and other mood stabilizers has declined by 50%, while the use of both second-generation antipsychotics (SGAs) and antidepressants has increased considerably. Over the same time period (1990-2017), disability-adjusted life years (DALYs) increased by 54.4%, from 6.02 million in 1990 to 9.29 million in 2017 which is greater than the 47.74% increase in incidence of the disease, suggesting that the changes in prescribing patterns have not been helpful for our patients. Furthermore, recent effectiveness studies continue to confirm the superiority of lithium and other mood stabilizers in the management of bipolar illness for both psychiatric and medical outcomes, reaffirming their role as foundational treatments in the management of type I bipolar disorder. Clinicians need to reassess their prescribing habits.

Review of animal models of bipolar disorder that alter ion regulation

BACKGROUND

Accurate modeling of psychiatric disorders in animals is essential for advancement in our understanding and treatment of the severe mental illnesses. Of the multiple models available for bipolar illness, the ones that disrupt ion flux are currently the only ones that meet the three criteria for validity: face validity, construct validity, and predictive validity.

METHODS

A directed review was performed to evaluate animal models for mania in which ion dysregulation was the key intervention.

RESULTS

Three models are identified. All focus on disruption of the sodium potassium pump. One is pharmacologic and requires surgical insertion of an intracerebroventricular (ICV) cannula and subsequent administration of ouabain. Two are genetic and are based on heterozygote knockout (KO) of the alpha2 or alpha3 subunits of the sodium pump. Alpha2 KOs are believed to have altered glial function, and they do not appear to have a full array of manic symptoms. Alpha3 KOs appear to be the best characterized animal model for bipolar disorder currently available.

CONCLUSION

Animal models that disrupt ion regulation are more inclined to model both mania and depression; and are thus the most promising models available. However, other models are important for demonstrating mechanisms in important pathophysiologic aspect of bipolar disorder.

Evaluation of the Effect of Memantine Supplementation in the Treatment of Acute Phase of Mania in Bipolar Disorder of Elderly Patients: A Double-blind Randomized Controlled Trial

Background:

This study aimed to evaluate the efficacy of memantine in the acute treatment of geriatric with bipolar disorder (BD) hospitalized for mania.

Materials and Methods:

This study conducted on 70 patients older than 60 years with BD in the acute phase of mania. Oral sodium valproate was prescribed in both groups. The intervention group received memantine tablet and the placebo group received a placebo tablet based on a same procedure. Severity of mania, cognitive changes, and quality of life (QoL) were assessed and recorded 4 and 8 weeks after the beginning of the study. The collected data were analyzed with SPSS (version 20) using independent samples t-test, analysis of variance in repeated observations, Chi-squared test, and Fisher's exact test.

Results:

Mania severity score had no significant difference at the beginning of the study, but 4 and 8 weeks after the intervention, it was reduced significantly in both groups (P < 0.001) that was higher in memantine group (P = 0.038). The mean increase in score of cognitive variations was 6.74 in the memantine group and 3.62 in the placebo group with a nonsignificant difference (P = 0.125). The scores of each dimension of QoL in the two groups showed that in all four dimensions, the patient's physical, psychological, social, and environmental status increased significantly by time (P < 0.001).

Conclusions:

According to the results of this study, memantine as an adjuvant to administration of sodium valproate may have a significant effect on decreasing the intensity of mania in the long run.

Memantine induces manic episode in a 73-year-old patient with vascular neurocognitive disorder: a case report

Memantine, an N-methyl-d-aspartate receptor antagonist, is a well-established treatment option for moderate-to-severe cognitive impairment related to Alzheimer disease. Recently, growing evidence has indicated memantine might also be effective in treatment of affective disorders. The common drug-induced adverse events of memantine include confusion, dizziness, drowsiness, headache, insomnia, and agitation. Herein, we presented a case of a 73-year-old female patient with vascular neurocognitive disorder, who developed a manic episode after taking memantine.

Cognitive flexibility impairment and reduced frontal cortex BDNF expression in the ouabain model of mania

Central infusion of the Na+/K+-ATPase inhibitor, ouabain in rats serves as an animal model of mania because it leads to hyperactivity, as well as reproduces ion dysregulation and reduced brain-derived neurotrophic factor (BDNF) levels similar to that observed in bipolar disorder. Bipolar disorder is also associated with cognitive inflexibility and working memory deficits. It is unknown whether ouabain treatment in rats leads to similar cognitive flexibility and working memory deficits. The present study examined the effects of an intracerebral ventricular infusion of ouabain in rats on spontaneous alternation, probabilistic reversal learning and BDNF expression levels in the frontal cortex. Ouabain treatment significantly increased locomotor activity, but did not affect alternation performance in a Y-maze. Ouabain treatment selectively impaired reversal learning in a spatial discrimination task using an 80/20 probabilistic reinforcement procedure. The reversal learning deficit in ouabain-treated rats resulted from an impaired ability to maintain a new choice pattern (increased regressive errors). Ouabain treatment also decreased sensitivity to negative feedback during the initial phase of reversal learning. Expression of BDNF mRNA and protein levels was downregulated in the frontal cortex which also negatively correlated with regressive errors. These findings suggest that the ouabain model of mania may be useful in understanding the neuropathophysiology that contributes to cognitive flexibility deficits and test potential treatments to alleviate cognitive deficits in bipolar disorder.

Memantine in the Treatment of Executive Function Deficits in Adults With ADHD

OBJECTIVE

To evaluate the efficacy and safety of memantine hydrochloride as an adjunct to stimulant pharmacotherapy for treating executive function deficits (EFDs) in adults with ADHD.

METHOD

This was a 12-week, double-blind, placebo-controlled, randomized clinical trial of memantine added to open-label treatment with stimulant medication. Because of the small sample size, we considered a standardized mean difference (equivalent to effect size) of ≥0.5 and odds ratios ≥2 as indicators of trend improvements.

RESULTS

Twelve participants received memantine and 14 received a placebo. Trend improvements favoring memantine were observed on Behavior Rating Inventory of Executive Functions-Adult Inhibition and Self-Monitor subscales when compared with Placebo. No significant changes were noted on the Cambridge Neuropsychological Test Automated Battery.

CONCLUSION

Among adults with ADHD and EFDs, adjunct treatment with memantine to osmotic release oral system-methylphenidate (OROS-MPH) was associated with improvements in selective areas of executive functioning, supporting the need for further research.

Failure of memantine to “reverse” quinpirole-induced hypomotility

AIM: To evaluate antidepressant-like effect of memantine in a rat model.

METHODS: Male Wistar rats were treated intraperitoneally with either vehicle, memantine (10 mg/kg) or imipramine (20 mg/kg), for 3 wk. Twenty-four hour after the last treatment animals were challenged with quinpirole (0.3 mg/kg s.c.) and tested for motor activity. After 1 h habituation to the motility cages, the motor response was recorded for the following 45-min and the data were collected in 5-min time bins.

RESULTS: As expected, chronic treatment with imipramine potentiated the locomotor stimulant effect of quinpirole. On the contrary, chronic memantine administration failed to induce the behavioral supersensitivity to the dopamine agonist.

CONCLUSION: The results show that memantine, at variance with antidepressant treatments, fails to induce dopaminergic behavioral supersensitivity. This observation is consistent with the results of preclinical and clinical studies suggesting that memantine does not have an acute antidepressant action but does have an antimanic and mood-stabilizing effect.

Modeling mania in preclinical settings: A comprehensive review

The current pathophysiological understanding of mechanisms leading to onset and progression of bipolar manic episodes remains limited. At the same time, available animal models for mania have limited face, construct, and predictive validities. Additionally, these models fail to encompass recent pathophysiological frameworks of bipolar disorder (BD), e.g. neuroprogression. Therefore, there is a need to search for novel preclinical models for mania that could comprehensively address these limitations. Herein we review the history, validity, and caveats of currently available animal models for mania. We also review new genetic models for mania, namely knockout mice for genes involved in neurotransmission, synapse formation, and intracellular signaling pathways. Furthermore, we review recent trends in preclinical models for mania that may aid in the comprehension of mechanisms underlying the neuroprogressive and recurring nature of BD. In conclusion, the validity of animal models for mania remains limited. Nevertheless, novel (e.g. genetic) animal models as well as adaptation of existing paradigms hold promise.

Memantine ameliorates autistic behavior, biochemistry & blood brain barrier impairments in rats

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, commonly characterized by altered social behavior, communication, biochemistry and pathological conditions. One percent of the worldwide population suffers from autism and males suffer more than females. NMDA receptors have the important role in neurodevelopment, neuropsychiatric and neurodegenerative disorders. This study has been designed to investigate the role of memantine, a NMDA receptor modulator, in prenatal valproic acid-induced autism in rats. Animals with prenatal valproic acid have shown the reduction in social interaction (three-chamber social behavior apparatus), spontaneous alternation (Y-Maze), exploratory activity (Hole board test), intestinal motility, serotonin levels (both in prefrontal cortex and ileum) and prefrontal cortex mitochondrial complex activity (complex I, II, IV). Furthermore, prenatal valproic acid-treated animals have shown an increase in locomotion (actophotometer), anxiety (elevated plus maze), brain oxidative stress (thiobarbituric acid reactive species, glutathione, catalase), nitrosative stress (nitrite/nitrate), inflammation (both in brain and ileum myeloperoxidase activity), calcium and blood-brain barrier permeability. Treatment with memantine has significantly attenuated prenatal valproic acid-induced reduction in social interaction, spontaneous alteration, exploratory activity intestinal motility, serotonin levels and prefrontal cortex mitochondrial complex activity. Furthermore, memantine has also attenuated the prenatal valproic acid-induced increase in locomotion, anxiety, brain oxidative and nitrosative stress, inflammation, calcium and blood-brain barrier permeability. Thus, it may be concluded that prenatal valproic acid has induced autistic behavior, biochemistry and blood-brain barrier impairment in animals, which were significantly attenuated by memantine. NMDA receptor modulators like memantine should be explored further for the therapeutic benefits in autism.

Cardiotonic Steroids as Modulators of Neuroinflammation

Cardiotonic steroids (CTS) are a class of specific ligands of the Na(+), K(+)- ATPase (NKA). NKA is a P-type ATPase that is ubiquitously expressed and although well known to be responsible for the maintenance of the cell electrochemical gradient through active transport, NKA can also act as a signal transducer in the presence of CTS. Inflammation, in addition to importantly driving organism defense and survival mechanisms, can also modulate NKA activity and memory formation, as well as being relevant to many chronic illnesses, neurodegenerative diseases, and mood disorders. The aim of the current review is to highlight the recent advances as to the role of CTS and NKA in inflammatory process, with a particular focus in the central nervous system.

Cariprazine delays ouabain-evoked epileptiform spikes and loss of activity in rat hippocampal slices

In the only bipolar cycling in vitro model, rat hippocampal slices are treated with the sodium pump inhibitor ouabain, which induces epileptiform activity, followed by refractory activity loss that recovers and cycles back to epileptiform activity. Thus, clinical cycling seen in patients with bipolar disorder is modeled on a cellular level as alternating hyperactivity and hypoactivity interspersed with normal activity. In this study, we tested the ability of cariprazine a new antipsychotic candidate to block ouabain-induced changes in rat hippocampal slices. Cycling of population spikes and epileptiform bursts was evoked using an extracellular stimulation electrode located in the Schaeffer collaterals of 400-µm-thick rat hippocampal slices treated with ouabain (3.3μM) alone or in combination with cariprazine (1, 5, 25, and 50µM). Responses were recorded using an extracellular electrode placed in the cell body layer of the CA1 region. Cariprazine 25 and 50µM delayed ouabain-induced epileptiform burst onset and subsequent activity loss. Lower cariprazine concentrations were ineffective. Cariprazine delays the onset of ouabain-induced epileptiform bursts and the loss of spiking activity similarly to that previously demonstrated with the mood stabilizer lithium. These results suggest that cariprazine may have therapeutic potential for treatment of bipolar disorder.

Memantine prevents "bipolar-like" behavior induced by chronic treatment with imipramine in rats

A great deal of evidence suggests that virtually all antidepressant treatments induce a dopaminergic behavioral supersensitivity. We have suggested that this effect may play a key role not only in the antidepressant effect of these treatments, but also in their ability to induce a switch from depression to mania. In 2003-4 we found that the sensitization of dopamine receptors induced by imipramine is followed, after imipramine withdrawal, by a desensitization of these receptors associated with a depressive-like behavior assessed in the forced swimming test. The dopamine receptor sensitization can be prevented by MK-801, an NMDA receptor antagonist, but not by currently used mood stabilizers (lithium, carbamazepine, valproate). These observations led us to suggest - and later confirm - with preliminary clinical observations that memantine may have an acute antimanic and a long-lasting mood-stabilizing effect in treatment-resistant bipolar disorder patients. Here we present data showing that memantine prevents not only the dopamine receptor sensitization induced by imipramine, as observed with MK-801, but also the ensuing desensitization and the associated depressive-like behaviorq observed after antidepressant withdrawal.

Memantine: New prospective in bipolar disorder treatment

We review preclinical and clinical evidences strongly suggesting that memantine, an old drug currently approved for Alzheimer's dementia, is an effective treatment for acute mania and for the prevention of manic/hypomanic and depressive recurrences of manic-depressive illness. Lithium remains the first line for the treatment and prophylaxis of bipolar disorders, but currently available treatment alternatives for lithium resistant patients are of limited and/or questionable efficacy. Thus, research and development of more effective mood stabilizer drugs is a leading challenge for modern psychopharmacology. We have demonstrated that 21 d administration of imipramine causes a behavioural syndrome similar to a cycle of bipolar disorder, i.e., a mania followed by a depression, in rats. Indeed, such treatment causes a behavioural supersensitivity to dopamine D2 receptor agonists associated with an increase sexual activity and aggressivity (mania). The dopamine receptor sensitization is followed, after imipramine discontinuation, by an opposite phenomenon (dopamine receptor desensitization) and an increased immobility time (depression) in the forced swimming test of depression. Memantine blocks the development of the supersensitivity and the ensuing desensitization associated with the depressive like behavior. On the basis of these observations we have suggested the use of memantine in the treatment of mania and in the prophylaxis of bipolar disorders. To test this hypothesis we performed several naturalistic studies that showed an acute antimanic effect and a long-lasting and progressive mood-stabilizing action (at least 3 years), without clinically relevant side effects. To confirm the observations of our naturalistic trials we are now performing a randomized controlled clinical trial. Finally we described the studies reporting the efficacy of memantine in manic-like symptoms occurring in psychiatric disorders other than bipolar.

LIMITATIONS

A randomized controlled clinical trial is needed to confirm our naturalistic observations.

CONCLUSION

We believe that this review presents enough pharmacological and clinical information to consider the administration of memantine in the treatment of bipolar disorders that no respond to standard mood stabilizers.

Cariprazine exerts antimanic properties and interferes with dopamine D2 receptor β-arrestin interactions

Activation of dopamine D₂ receptors (D₂R) modulates G protein/cAMP-dependent signaling and also engages Akt-GSK-3 signaling through D₂R/β-arrestin 2 scaffolding of Akt and PP2A. This G protein-independent pathway may be important in mediating the antimanic effects of mood stabilizers and antipsychotics. The mood stabilizer lithium influences behavior and Akt/GSK-3 signaling in mice and many antipsychotics have been shown to more potently antagonize the activity of the β-arrestin-2 pathway relative to the G protein-dependent pathway. Cariprazine, an antipsychotic with potent D₃R/D₂R partial agonist activity and preferential binding to D₃R, was investigated for its effects on the mediators of D₂R pathways in vitro and its efficacy in animal models of mania. Effects on G protein-dependent activity were measured via inhibition of isoproterenol-induced cAMP production; effects on D₂R/β-arrestin 2 signaling were determined using bioluminescence resonance energy transfer (BRET). Cariprazine was tested in vivo for antimanic-like activity, using the ouabain-induced hyperactivity model in rats. Cariprazine was more potent than aripiprazole in inhibiting isoproterenol-induced cAMP although both compounds showed similar maximum efficacy. In assays of D₂R/β-arrestin 2-dependent interactions, cariprazine showed very weak partial agonist activity, unless the levels of receptor kinase were increased; as an antagonist it showed similar potency to haloperidol and ∼fivefold greater potency than aripiprazole. In an animal model of mania, cariprazine showed similar efficacy as lithium in attenuating the effects of ouabain-induced hyperactivity. In summary, the differential effects of cariprazine on D₂R G protein and β-arrestin 2 mediators of signal transduction pathways could contribute to its potent antimanic-like activity.

The emerging role of dopamine-glutamate interaction and of the postsynaptic density in bipolar disorder pathophysiology: Implications for treatment

Aberrant synaptic plasticity, originating from abnormalities in dopamine and/or glutamate transduction pathways, may contribute to the complex clinical manifestations of bipolar disorder (BD). Dopamine and glutamate systems cross-talk at multiple levels, such as at the postsynaptic density (PSD). The PSD is a structural and functional protein mesh implicated in dopamine and glutamate-mediated synaptic plasticity. Proteins at PSD have been demonstrated to be involved in mood disorders pathophysiology and to be modulated by antipsychotics and mood stabilizers. On the other side, post-receptor effectors such as protein kinase B (Akt), glycogen synthase kinase-3 (GSK-3) and the extracellular signal-regulated kinase (Erk), which are implicated in both molecular abnormalities and treatment of BD, may interact with PSD proteins, and participate in the interplay of the dopamine-glutamate signalling pathway. In this review, we describe emerging evidence on the molecular cross-talk between dopamine and glutamate signalling in BD pathophysiology and pharmacological treatment, mainly focusing on dysfunctions in PSD molecules. We also aim to discuss future therapeutic strategies that could selectively target the PSD-mediated signalling cascade at the crossroads of dopamine-glutamate neurotransmission.

Role of convergent activation of glutamatergic and dopaminergic systems in the nucleus accumbens in the development of methamphetamine psychosis and dependence

Methamphetamine (Meth) abuse can result in long-lasting psychosis and dependence. The nucleus accumbens (NAc), which controls psychomotor and reward behaviours, is an important interface between the limbic system and receives convergent projections from dopaminergic and glutamatergic terminals. This study investigated the involvements of dopaminergic and glutamatergic transmission in the development of Meth psychosis and dependence by using tyrosine hydroxylase heterozygous mutant (TH+/-) mice and N-methyl-d-aspartate receptor knockout (NR2A-/-) mice. Repeated treatment with Meth (1 mg/kg s.c.) for 7 d in wild-type mice led to the development of behavioural abnormalities such as hyperactivity, sensory motor gating deficits and place preference. Associated with the behavioural changes, repeated treatment with Meth led to protein kinase A activation and phosphorylation of Ca2+/calmodulin kinase II and cyclic AMP response element binding protein in the NAc. In contrast, TH+/- and NR2A-/- mice displayed neither behavioural abnormalities nor activation of intracellular signalling pathways in the NAc. These results suggest that both dopaminergic and glutamatergic transmission play a crucial role in the development of Meth psychosis and dependence, which are associated with convergent activation of intracellular signalling pathways in the NAc.

Hyperactivity: glycogen synthase kinase-3 as a therapeutic target

The diagnosis of hyperactivity-associated disorders has increased within the past few years. The prevalence of hyperactivity-associated disorders is indicative of the need to more fully understand the underlying causes and to develop improved therapeutic interventions. There is increasing evidence that glycogen synthase kinase-3 (GSK3) mediates locomotor hyperactivity in a number of animal models, and therefore may be a potential target for therapeutic intervention in hyperactivity-associated behaviors. In this review, we discuss 1) the effect of manipulations of GSK3 in the absence of drugs and disorders on locomotor activity, 2) the role of GSK3 in drug-induced hyperactivity in rodents, and 3) regulation of locomotor activity by GSK3 in transgenic mouse models related to specific disorders. These studies link GSK3 regulation and activity to hyperactivity-associated behaviors and disease pathologies.

The role of memantine in the treatment of psychiatric disorders other than the dementias: a review of current preclinical and clinical evidence

Memantine, a non-competitive NMDA receptor antagonist approved for Alzheimer's disease with a good safety profile, is increasingly being studied in a variety of non-dementia psychiatric disorders. We aimed to critically review relevant literature on the use of the drug in such disorders. We performed a PubMed search of the effects of memantine in animal models of psychiatric disorders and its effects in human studies of specific psychiatric disorders. The bulk of the data relates to the effects of memantine in major depressive disorder and schizophrenia, although more recent studies have provided data on the use of the drug in bipolar disorder as an add-on. Despite interesting preclinical data, results in major depression are not encouraging. Animal studies investigating the possible usefulness of memantine in schizophrenia are controversial; however, interesting findings were obtained in open studies of schizophrenia, but negative placebo-controlled, double-blind studies cast doubt on their validity. The effects of memantine in anxiety disorders have been poorly investigated, but data indicate that the use of the drug in obsessive-compulsive disorder and post-traumatic stress disorder holds promise, while findings relating to generalized anxiety disorder are rather disappointing. Results in eating disorders, catatonia, impulse control disorders (pathological gambling), substance and alcohol abuse/dependence, and attention-deficit hyperactivity disorder are inconclusive. In most psychiatric non-Alzheimer's disease conditions, the clinical data fail to support the usefulness of memantine as monotherapy or add-on treatment However, recent preclinical and clinical findings suggest that add-on memantine may show antimanic and mood-stabilizing effects in treatment-resistant bipolar disorder.

New drugs for bipolar disorder

Bipolar disorder (BD) is one of the most potentially severe mental disorders. Literature data indicate that despite the current available treatments, a large proportion of patients do not achieve complete remission, with consequent residual symptoms and chronic impairment. We carried out a comprehensive review of new pharmacologic treatments for BD. Even though the core treatment of BD likely will not likely undergo substantial changes over the next few years, many promising results with respect to new augmentation strategies were identified. New treatments for bipolar depression and for BD-related cognitive impairment seem to represent particularly fertile areas of research.

Glycogen synthase kinase-3 in the etiology and treatment of mood disorders

The mood disorders major depressive disorder and bipolar disorder are prevalent, are inadequately treated, and little is known about their etiologies. A better understanding of the causes of mood disorders would benefit from improved animal models of mood disorders, which now rely on behavioral measurements. This review considers the limitations in relating measures of rodent behaviors to mood disorders, and the evidence from behavioral assessments indicating that glycogen synthase kinase-3 (GSK3) dysregulation promotes mood disorders and is a potential target for treating mood disorders. The classical mood stabilizer lithium was identified by studying animal behaviors and later was discovered to be an inhibitor of GSK3. Several mood-relevant behavioral effects of lithium in rodents have been identified, and most have now been shown to be due to its inhibition of GSK3. An extensive variety of pharmacological and molecular approaches for manipulating GSK3 are discussed, the results of which strongly support the proposal that inhibition of GSK3 reduces both depression-like and manic-like behaviors. Studies in human postmortem brain and peripheral cells also have identified correlations between alterations in GSK3 and mood disorders. Evidence is reviewed that depression may be associated with impaired inhibitory control of GSK3, and mania by hyper-stimulation of GSK3. Taken together, these studies provide substantial support for the hypothesis that inhibition of GSK3 activity is therapeutic for mood disorders. Future research should identify the causes of dysregulated GSK3 in mood disorders and the actions of GSK3 that contribute to these diseases.

Current and emerging therapies for the management of bipolar disorders

Bipolar disorder is a complex condition to treat because agents that may be effective for a specific phase may not be effective for other phases, or may even worsen the overall course of the illness. Over the last decade there has been an increase in research activity in the treatment of bipolar illness. There are now several agents that are well established for the treatment of acute mania (lithium, divalproex, carbamazepine, nearly all antipsychotics), acute bipolar depression (lamotrigine, quetiapine, olanzapine/fluoxetine combination), and relapse prevention (lithium, lamotrigine, divalproex, most second generation antipsychotics). There are also novel treatments that are being studied for all three phases. These include eslicarbazepine, cariprazine, MEM-1003, memantine, tamoxifen and pentazocine for acute mania; pramipexole, modafinil, armodafinil, divalproex, lurasidone, agomelatine, cariprazine, lisedexamfetamine, riluzole, RG-2417, bifeprunox, ropinirole, GSK1014802, and magnetic stimulation for bipolar depression; and asenapine, lurasidone, and cariprazine for relapse prevention. Additionally, there are accumulating data that antidepressants, particularly serotoninergic ones, are not particularly effective in acute bipolar depression and may worsen the course of the illness.