Attenuation of mania-like behavior in Na+,K+-ATPase α3 mutant mice by prospective therapies for bipolar disorder: Melatonin and exercise

Phenotype Distinctions in Mice Deficient in the Neuron-Specific α3 Subunit of Na,K-ATPase: Atp1a3tm1Ling/+ and Atp1a3 +/D801Y

ATP1A3 is a Na,K-ATPase gene expressed specifically in neurons in the brain. Human mutations are dominant and produce an unusually wide spectrum of neurological phenotypes, most notably rapid-onset dystonia parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). Here we compared heterozygotes of two mouse lines, a line with little or no expression (Atp1a3tm1Ling/+) and a knock-in expressing p.Asp801Tyr (D801Y, Atp1a3 +/D801Y). Both mouse lines had normal lifespans, but Atp1a3 +/D801Y had mild perinatal mortality contrasting with D801N mice (Atp1a3 +/D801N), which had high mortality. The phenotypes of Atp1a3tm1Ling/+ and Atp1a3 +/D801Y were different, and testing of each strain was tailored to its symptom range. Atp1a3tm1Ling/+ mice displayed little at baseline, but repeated ethanol intoxication produced hyperkinetic motor abnormalities not seen in littermate controls. Atp1a3 +/D801Y mice displayed robust phenotypes: hyperactivity, diminished posture consistent with hypotonia, and deficiencies in beam walk and wire hang tests. Symptoms also included qualitative motor abnormalities that are not well quantified by conventional tests. Paradoxically, Atp1a3 +/D801Y showed sustained better performance than wild type on the accelerating rotarod. Atp1a3 +/D801Y mice were overactive in forced swimming and afterward had intense shivering, transient dystonic postures, and delayed recovery. Remarkably, Atp1a3 +/D801Y mice were refractory to ketamine anesthesia, which elicited hyperactivity and dyskinesia even at higher dose. Neither mouse line exhibited fixed dystonia (typical of RDP patients), spontaneous paroxysmal weakness (typical of AHC patients), or seizures but had consistent, measurable neurological abnormalities. A gradient of variation supports the importance of studying multiple Atp1a3 mutations in animal models to understand the roles of this gene in human disease.

Calcium Channel Antagonists for Mood Disorders

PURPOSE

Development of new thymoleptic medications has primarily centered on anticonvulsants and antipsychotic drugs. Based on our studies of intracellular calcium ion signaling in mood disorders, we were interested in the use of novel medications that act on this mechanism of neuronal activation as potential mood stabilizers.

METHOD

We reviewed the dynamics of the calcium second messenger system and the international body of data demonstrating increased baseline and stimulated intracellular calcium levels in peripheral cells of patients with bipolar mood disorders. We then examined studies of the effect of established mood stabilizers on intracellular calcium ion levels and on mechanisms of mobilization of this second messenger. After summarizing studies of calcium channel blocking agents, whose primary action is to attenuate hyperactive intracellular calcium signaling, we considered clinical experience with this class of medications and the potential for further research.

FINDINGS

Established mood stabilizers normalize increased intracellular calcium ion levels in bipolar disorder patients. Most case series and controlled studies suggest an antimanic and possibly mood stabilizing effect of the calcium channel blocking medications verapamil and nimodipine, with fewer data on isradipine. A relatively low risk of teratogenicity and lack of cognitive adverse effects or weight gain suggest possible applications in pregnancy and in patients for whom these are considerations.

IMPLICATIONS

Medications that antagonize hyperactive intracellular signaling warrant more interest than they have received in psychiatry. Further experience will clarify the applications of these medications alone and in combination with more established mood stabilizers.

Melatonin stabilizes age-dependent alterations in erythrocyte membrane induced by 'Artificial Light at Night' in a chronodisrupted model of rat

Growing evidence has shown that Artificial light at night (ALAN) is one of the threatening risk factors which disrupt circadian homeodynamics of cellular processes. The chronobiological role of melatonin seems to represent an important aspect of its contribution to healthy aging. In the present study, we examined the age dependent effect of melatonin on erythrocyte membrane transporters and oxidative stress biomarkers against ALAN to understand the degree of photo-oxidative damage in chronodisrupted rat model. Young (3 months) and old (24 months) male Wistar rats were subdivided in the following four young groups (n = 4) ; (i) control (ii) melatonin (10 mg/kg) (iii) ALAN (500 lx) (iv) ALAN (500 lx) + melatonin (10 mg/kg) and four old groups (n = 4); (v) control (vi) melatonin (10 mg/kg) (vii) ALAN (500 lx) (viii) ALAN (500 lx) + melatonin (10 mg/kg) to the experimental conditions for 10 days. Our findings demonstrated that ALAN significantly enhanced erythrocyte membrane lipid hydroperoxides (LHPs), protein carbonyl (PCO) while reduced total thiol (T-SH), and sialic acid (SA) level with higher amplitude in old ALAN group is restored by exogenous supplementation of melatonin. Activity of membrane transporters, sodium potassium ATPase (NKA) and plasma membrane calcium ion ATPase (PMCA) is significantly reduced meanwhile sodium hydrogen exchanger (NHE) activity is enhanced under the influence of ALAN with higher extent in old groups is effectively ameliorated by melatonin treatment. Further melatonin reduced osmotic fragility of erythrocyte in both young and old rats. It has been concluded from results that ALAN provoked redox insult and disrupt transporters activity more prominently in erythrocyte membrane of aged groups. Exogenous supplementation of melatonin is one of the possible therapeutic approaches to reinforce circadian modulations against ALAN in aged populations.

Role of endogenous ouabain in the etiology of bipolar disorder

Background

Bipolar disorder is a severe psychiatric illness with poor prognosis and problematic and suboptimal treatments. Understanding the pathoetiologic mechanisms may improve treatment and outcomes.

Discussion

Dysregulation of cationic homeostasis is the most reproducible aspect of bipolar pathophysiology. Correction of ionic balance is the universal mechanism of action of all mood stabilizing medications. Recent discoveries of the role of endogenous sodium pump modulators (which include ‘endogenous ouabain’) in regulation of sodium and potassium distribution, inflammation, and activation of key cellular second messenger systems that are important in cell survival, and the demonstration that these stress-responsive chemicals may be dysregulated in bipolar patients, suggest that these compounds may be candidates for the coupling of environmental stressors and illness onset. Specifically, individuals with bipolar disorder appear to be unable to upregulate endogenous ouabain under conditions that require it, and therefore may experience a relative deficiency of this important regulatory hormone. In the absence of elevated endogenous ouabain, neurons are unable to maintain their normal resting potential, become relatively depolarized, and are then susceptible to inappropriate activation. Furthermore, sodium pump activity appears to be necessary to prevent inflammatory signals within the central nervous system. Nearly all available data currently support this model, but additional studies are required to solidify the role of this system.

Conclusion

Endogenous ouabain dysregulation appears to be a reasonable candidate for understanding the pathophysiology of bipolar disorder.

Antimania-Like Effect of Panax ginseng Regulating the Glutamatergic Neurotransmission in REM-Sleep Deprivation Rats

Previous studies have shown the therapeutic properties of ginseng and ginsenosides on hyperactive and impulsive behaviors in several psychiatric diseases. Herein, we investigated the effect of Panax ginseng Meyer (PG) on hyperactive/impulsive behaviors in a manic-like animal model, sleep deprivation (SD) rats. Male rats were sleep-deprived for 48 h, and PG (200 mg/kg) was administered for 4 days, from 2 days prior to the start of SD to the end date of SD. The elevated plus maze (EPM) test showed that PG alleviated the increased frequency of entries into and spent time within open arms by SD. In order to investigate the molecular mechanism on this effect of PG, we assessed differentially expressed genes (DEGs) in the prefrontal cortex of PG-treated SD rats using RNA sequencing (RNA-seq) and performed gene-enrichment analysis for DEGs. The gene-enrichment analysis showed that PG most prominently affected the glutamatergic synapse pathway. Among the glutamatergic synapse pathway genes, particularly, PG enhanced the expressions of glutamate transporter Slc1a3 and Slc1a2 reduced in SD rats. Moreover, we found that PG could inhibit the SD-induced phosphorylation of the NR2A subunit of the NMDA receptor. These results suggested that PG might have a therapeutic effect against the manic-like behaviors, regulating the glutamatergic neurotransmission.

Efficacy of melatonin as an adjunct in the treatment of acute mania: a double-blind and placebo-controlled trial

This is a double-blind, placebo-controlled, parallel-grouped clinical trial, which was designed to investigate the potential effects of melatonin add-on treatment with lithium and risperidone on acute manic episodes in patients with bipolar disorder (BD). A total of 54 patients were included and randomly assigned into two groups of melatonin and placebo. The trial group received 3 mg/day risperidone, 900 mg/day lithium, and 6 mg/day melatonin. The placebo group received the same dose of risperidone and lithium plus placebo. The participants were evaluated at four sessions, consisting of baseline, weeks 1, 4, and 6. The manic symptoms and overall clinical improvement of the patients were assessed using the Young Mania Rating Scale (YMRS) and Clinical Global Impressions-Improvement (CGI-I), respectively. Two trial groups were matched based on all baseline characteristics. The patients in two trial groups had comparable serum lithium levels at weeks 1, 4, and 6. Our results from the general linear model repeated measures analysis showed a significant effect for time × treatment interaction on YMRS scores (P = 0.021 and F-value = 3.7). Furthermore, outcomes of the CGI-I rating scale demonstrated that patients in the melatonin group had better clinical improvements compared to the placebo group (P = 0.018). Our results provided preliminary evidence supporting melatonin as an effective adjunctive treatment leading to significant improvements in manic symptoms and overall clinical status in acute episodes of mania.

Brain-Derived Neurotrophic Factor in Brain Disorders: Focus on Neuroinflammation

Brain-derived neurotrophic factor (BDNF) is one of the most studied neurotrophins in the healthy and diseased brain. As a result, there is a large body of evidence that associates BDNF with neuronal maintenance, neuronal survival, plasticity, and neurotransmitter regulation. Patients with psychiatric and neurodegenerative disorders often have reduced BDNF concentrations in their blood and brain. A current hypothesis suggests that these abnormal BDNF levels might be due to the chronic inflammatory state of the brain in certain disorders, as neuroinflammation is known to affect several BDNF-related signaling pathways. Activation of glia cells can induce an increase in the levels of pro- and antiinflammatory cytokines and reactive oxygen species, which can lead to the modulation of neuronal function and neurotoxicity observed in several brain pathologies. Understanding how neuroinflammation is involved in disorders of the brain, especially in the disease onset and progression, can be crucial for the development of new strategies of treatment. Despite the increasing evidence for the involvement of BDNF and neuroinflammation in brain disorders, there is scarce evidence that addresses the interaction between the neurotrophin and neuroinflammation in psychiatric and neurodegenerative diseases. This review focuses on the effect of acute and chronic inflammation on BDNF levels in the most common psychiatric and neurodegenerative disorders and aims to shed some light on the possible biological mechanisms that may influence this effect. In addition, this review will address the effect of behavior and pharmacological interventions on BDNF levels in these disorders.

Circadian Disruptions in the Myshkin Mouse Model of Mania Are Independent of Deficits in Suprachiasmatic Molecular Clock Function

BACKGROUND

Alterations in environmental light and intrinsic circadian function have strong associations with mood disorders. The neural origins underpinning these changes remain unclear, although genetic deficits in the molecular clock regularly render mice with altered mood-associated phenotypes.

METHODS

A detailed circadian and light-associated behavioral characterization of the Na+/K+-ATPase α3 Myshkin (Myk/+) mouse model of mania was performed. Na+/K+-ATPase α3 does not reside within the core circadian molecular clockwork, but Myk/+ mice exhibit concomitant disruption in circadian rhythms and mood. The neural basis of this phenotype was investigated through molecular and electrophysiological dissection of the master circadian pacemaker, the suprachiasmatic nuclei (SCN). Light input and glutamatergic signaling to the SCN were concomitantly assessed through behavioral assays and calcium imaging.

RESULTS

In vivo assays revealed several circadian abnormalities including lengthened period and instability of behavioral rhythms, and elevated metabolic rate. Grossly aberrant responses to light included accentuated resetting, accelerated re-entrainment, and an absence of locomotor suppression. Bioluminescent recording of circadian clock protein (PERIOD2) output from ex vivo SCN revealed no deficits in Myk/+ molecular clock function. Optic nerve crush rescued the circadian period of Myk/+ behavior, highlighting that afferent inputs are critical upstream mediators. Electrophysiological and calcium imaging SCN recordings demonstrated changes in the response to glutamatergic stimulation as well as the electrical output indicative of altered retinal input processing.

CONCLUSIONS

The Myshkin model demonstrates profound circadian and light-responsive behavioral alterations independent of molecular clock disruption. Afferent light signaling drives behavioral changes and raises new mechanistic implications for circadian disruption in affective disorders.

Na+, K+-ATPase inhibition causes hyperactivity and impulsivity in mice via dopamine D2 receptor-mediated mechanism

Hyperactivity and impulsivity are common symptoms in several psychiatric disorders. Although dysfunction of Na⁺, K⁺-ATPase has been reported to be associated with the psychiatric disorders, it is not clear whether inhibition of Na⁺, K⁺-ATPase causes behavioral effects, including hyperactivity and impulsivity, in mice. Here, we evaluated the effect of intracerebroventricular (icv) injection of ouabain, an inhibitor of Na⁺, K⁺-ATPase, on hyperactivity and impulsivity in mice. At seven days after icv injection, ouabain-injected mice displayed the increase in the distance traveled in the open field arena in the open field test and the increase in the number of head-dipping behavior in the cliff avoidance test. Chlorpromazine or haloperidol, typical antipsychotics, reduced the hyperactivity and impulsivity in ouabain-injected mice. On the other hand, neither lithium carbonate nor valproate, established mood-stabilizing drugs, improved hyperactivity and impulsivity in our mouse model. Furthermore, ouabain-injected mice exhibited the increase in the number of c-fos-positive cells in the nucleus accumbens and the prefrontal cortex but not in the ventral tegmental area, which was reduced by haloperidol. These results suggest that the dysfunction of Na⁺, K⁺-ATPase causes hyperactivity and impulsivity via hyperactivation of dopamine D2 receptor-mediated signaling pathway, causing disturbed neuronal circuits in mice.

Na⁺, K⁺-ATPase Signaling and Bipolar Disorder

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Although in past decades the "monoamine hypothesis" has dominated our understanding of both the pathophysiology of depressive disorders and the action of pharmacological treatments, recent studies focus on the involvement of additional neurotransmitters/neuromodulators systems and cellular processes in BD. Here, evidence for the participation of Na⁺, K⁺-ATPase and its endogenous regulators, the endogenous cardiac steroids (ECS), in the etiology of BD is reviewed. Proof for the involvement of brain Na⁺, K⁺-ATPase and ECS in behavior is summarized and it is hypothesized that ECS-Na⁺, K⁺-ATPase-induced activation of intracellular signaling participates in the mechanisms underlying BD. We propose that the activation of ERK, AKT, and NFκB, resulting from ECS-Na⁺, K⁺-ATPase interaction, modifies neuronal activity and neurotransmission which, in turn, participate in the regulation of behavior and BD. These observations suggest Na⁺, K⁺-ATPase-mediated signaling is a potential target for drug development for the treatment of BD.

Deficits in social behavioral tests in a mouse model of alternating hemiplegia of childhood

Social behavioral deficits have been observed in patients diagnosed with alternating hemiplegia of childhood (AHC), rapid-onset dystonia-parkinsonism and CAPOS syndrome, in which specific missense mutations in ATP1A3, encoding the Na⁺, K⁺-ATPase α3 subunit, have been identified. To test the hypothesis that social behavioral deficits represent part of the phenotype of Na⁺, K⁺-ATPase α3 mutations, we assessed the social behavior of the Myshkin mouse model of AHC, which has an I810N mutation identical to that found in an AHC patient with co-morbid autism. Myshkin mice displayed deficits in three tests of social behavior: nest building, pup retrieval and the three-chamber social approach test. Chronic treatment with the mood stabilizer lithium enhanced nest building in wild-type but not Myshkin mice. In light of previous studies revealing a broad profile of neurobehavioral deficits in the Myshkin model – consistent with the complex clinical profile of AHC – our results suggest that Na⁺, K⁺-ATPase α3 dysfunction has a deleterious, but nonspecific, effect on social behavior. By better defining the behavioral profile of Myshkin mice, we identify additional ATP1A3-related symptoms for which the Myshkin model could be used as a tool to advance understanding of the underlying neural mechanisms and develop novel therapeutic strategies.

Physical Activity Modulates Common Neuroplasticity Substrates in Major Depressive and Bipolar Disorder

Mood disorders (MDs) are chronic, recurrent mental diseases that affect millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility, a need remains to better understand the interrelated mechanisms that contribute to neuroplasticity deficits in MDs and the means by which various therapeutics mitigate them. Of those therapeutics being investigated, physical activity (PA) has shown clear and consistent promise. Accordingly, the aims of this review are to (1) explicate key modulators, processes, and interactions that impinge upon multiple susceptibility points to effectuate neuroplasticity deficits in MDs; (2) explore the putative mechanisms by which PA mitigates these features; (3) review protocols used to induce the positive effects of PA in MDs; and (4) highlight implications for clinicians and researchers.

Progressive Brain Atrophy in Alternating Hemiplegia of Childhood

Background

Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disorder that includes involuntary movements, paroxysmal symptoms, and various severities of nonparoxysmal symptoms.

Objective

To investigate the occurrence of structural brain abnormalities in patients with AHC during clinical courses.

Methods

Conventional brain magnetic resonance imaging findings and clinical courses were retrospectively investigated in 14 patients with AHC confirmed by ATP1A3 mutations.

Results

Progressive frontal dominant cerebral, diffuse cerebellar cortical, and severe hippocampal atrophy were observed in seven patients with irreversible severe motor and intellectual deterioration. All of these seven patients exhibited status epilepticus and required transient respiratory care. Isolated diffuse cerebellar cortical atrophy was observed in two adult patients with mild motor regression. Five patients without apparent deterioration displayed almost normal brain findings.

Conclusions

The areas of atrophy were consistent with the areas of increased expression of the Na⁺/K⁺-ATPase α3 subunit encoded by ATP1A3. Some of paroxysmal and nonparoxysmal neurological symptoms are considered as related to the areas of brain atrophy.

Exercise in bipolar patients: A systematic review

BACKGROUND

Sedentary lifestyle is frequent in psychiatric disorders, however the directions of this association and benefits of physical activity are unclear. This is a systematic review about exercise in patients with bipolar disorder.

METHODS

We performed a systematic literature search of studies published in English (1995 Jan to 2016 Jan) in PubMed, and Cochrane Library combining the medical terms 'physical activity' or 'sedentary' or 'physical exercise' with 'bipolar disorder' or 'mania' or 'bipolar depression'.

RESULTS

Thirty-one studies were selected and included 15,587 patients with bipolar disorder. Sedentary lifestyle varied from 40% to 64.9%. Physical activity was associated with less depressive symptoms, better quality of life and increased functioning. Some evidence indicates a relationship between vigorous exercises and mania. Three prospective cohorts were reported; and no prospective randomized controlled trial was identified. Three studies focused on biomarkers in bipolar patients; and one reported the relationship between exercise and sleep in this group. Two assessed physical exercise in adolescents.

LIMITATIONS

(1) Differences between studies preventing a unified analysis; (2) most studies were cross-sectional; (3) motivation for exercising is a selection bias in most studies; (4) no intervention study assessing only physical exercise; (5) lack of studies comparing exercise across mood states.

CONCLUSION

Generally, exercise was associated with improved health measures including depressive symptoms, functioning and quality of life. Evidence was insufficient to establish a cause-effect relationship between mood and physical exercise. Future research including randomized trials is needed to clarify the role of physical activity in bipolar patients.

Differential melatonin alterations in cerebrospinal fluid and serum of patients with major depressive disorder and bipolar disorder

BACKGROUND

Melatonin, which plays an important role for regulation of circadian rhythms and the sleep/wake cycle has been linked to the pathophysiology of major depressive and bipolar disorder. Here we investigated melatonin levels in cerebrospinal fluid (CSF) and serum of depression and bipolar patients to elucidate potential differences and commonalities in melatonin alterations across the two disorders.

METHODS

Using enzyme-linked immunosorbent assays, CSF and serum melatonin levels were measured in 108 subjects (27 healthy volunteers, 44 depressed and 37 bipolar patients). Covariate adjusted multiple regression analysis was used to investigate group differences in melatonin levels.

RESULTS

In CSF, melatonin levels were significantly decreased in bipolar (P<0.001), but not major depressive disorder. In serum, we observed a significant melatonin decrease in major depressive (P=0.003), but not bipolar disorder. No associations were found between serum and CSF melatonin levels or between melatonin and measures of symptom severity or sleep disruptions in either condition.

CONCLUSION

This study suggests the presence of differential, body fluid specific alterations of melatonin levels in bipolar and major depressive disorder. Further, longitudinal studies are required to explore the disease phase dependency of melatonin alterations and to mechanistically explore the causes and consequences of site-specific alterations.

The Influence of Na(+), K(+)-ATPase on Glutamate Signaling in Neurodegenerative Diseases and Senescence

Decreased Na(+), K(+)-ATPase (NKA) activity causes energy deficiency, which is commonly observed in neurodegenerative diseases. The NKA is constituted of three subunits: α, β, and γ, with four distinct isoforms of the catalytic α subunit (α1-4). Genetic mutations in the ATP1A2 gene and ATP1A3 gene, encoding the α2 and α3 subunit isoforms, respectively can cause distinct neurological disorders, concurrent to impaired NKA activity. Within the central nervous system (CNS), the α2 isoform is expressed mostly in glial cells and the α3 isoform is neuron-specific. Mutations in ATP1A2 gene can result in familial hemiplegic migraine (FHM2), while mutations in the ATP1A3 gene can cause Rapid-onset dystonia-Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC), as well as the cerebellar ataxia, areflexia, pescavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome. Data indicates that the central glutamatergic system is affected by mutations in the α2 isoform, however further investigations are required to establish a connection to mutations in the α3 isoform, especially given the diagnostic confusion and overlap with glutamate transporter disease. The age-related decline in brain α2∕3 activity may arise from changes in the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG) pathway. Glutamate, through nitric oxide synthase (NOS), cGMP and PKG, stimulates brain α2∕3 activity, with the glutamatergic N-methyl-D-aspartate (NMDA) receptor cascade able to drive an adaptive, neuroprotective response to inflammatory and challenging stimuli, including amyloid-β. Here we review the NKA, both as an ion pump as well as a receptor that interacts with NMDA, including the role of NKA subunits mutations. Failure of the NKA-associated adaptive response mechanisms may render neurons more susceptible to degeneration over the course of aging.

Animal models of bipolar mania: The past, present and future

Bipolar disorder (BD) is the sixth leading cause of disability in the world according to the World Health Organization and affects nearly six million (∼2.5% of the population) adults in the United State alone each year. BD is primarily characterized by mood cycling of depressive (e.g., helplessness, reduced energy and activity, and anhedonia) and manic (e.g., increased energy and hyperactivity, reduced need for sleep, impulsivity, reduced anxiety and depression), episodes. The following review describes several animal models of bipolar mania with a focus on more recent findings using genetically modified mice, including several with the potential of investigating the mechanisms underlying 'mood' cycling (or behavioral switching in rodents). We discuss whether each of these models satisfy criteria of validity (i.e., face, predictive, and construct), while highlighting their strengths and limitations. Animal models are helping to address critical questions related to pathophysiology of bipolar mania, in an effort to more clearly define necessary targets of first-line medications, lithium and valproic acid, and to discover novel mechanisms with the hope of developing more effective therapeutics. Future studies will leverage new technologies and strategies for integrating animal and human data to reveal important insights into the etiology, pathophysiology, and treatment of BD.

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.

Dorsal raphe neuroinflammation promotes dramatic behavioral stress dysregulation

Impulsivity, risk-taking behavior, and elevated stress responsivity are prominent symptoms of mania, a behavioral state common to schizophrenia and bipolar disorder. Though inflammatory processes activated within the brain are involved in the pathophysiology of both disorders, the specific mechanisms by which neuroinflammation drives manic behavior are not well understood. Serotonin cell bodies originating within the dorsal raphe (DR) play a major role in the regulation of behavioral features characteristic of mania. Therefore, we hypothesized that the link between neuroinflammation and manic behavior may be mediated by actions on serotonergic neurocircuitry. To examine this, we induced local neuroinflammation in the DR by viral delivery of Cre recombinase into interleukin (IL)-1β(XAT) transgenic male and female mice, resulting in overexpressing of the proinflammatory cytokine, IL-1β. For assertion of brain-region specificity of these outcomes, the prefrontal cortex (PFC), as a downstream target of DR serotonergic projections, was also infused. Inflammation within the DR, but not the PFC, resulted in a profound display of manic-like behavior, characterized by increased stress-induced locomotion and responsivity, and reduced risk-aversion/fearfulness. Microarray analysis of the DR revealed a dramatic increase in immune-related genes, and dysregulation of genes important in GABAergic, glutamatergic, and serotonergic neurotransmission. Behavioral and physiological changes were driven by a loss of serotonergic neurons and reduced output as measured by high-performance liquid chromatography, demonstrating inflammation-induced serotonergic hypofunction. Behavioral changes were rescued by acute selective serotonin reuptake inhibitor treatment, supporting the hypothesis that serotonin dysregulation stemming from neuroinflammation in the DR underlies manic-like behaviors.

The role of brain-derived neurotrophic factor in comorbid depression: possible linkage with steroid hormones, cytokines, and nutrition

Increasing evidence demonstrates a connection between growth factor function (including brain-derived neurotrophic factor, BDNF), glucocorticoid levels (one of the steroid hormones), and the pathophysiology of depressive disorders. Because both BDNF and glucocorticoids regulate synaptic function in the central nervous system, their functional interaction is of major concern. Interestingly, alterations in levels of estrogen, another steroid hormone, may play a role in depressive-like behavior in postpartum females with fluctuations of BDNF-related molecules in the brain. BDNF and cytokines, which are protein regulators of inflammation, stimulate multiple intracellular signaling cascades involved in neuropsychiatric illness. Pro-inflammatory cytokines may increase vulnerability to depressive symptoms, such as the increased risk observed in patients with cancer and/or autoimmune diseases. In this review, we discuss the possible relationship between inflammation and depression, in addition to the cross-talk among cytokines, BDNF, and steroids. Further, since nutritional status has been shown to affect critical pathways involved in depression through both BDNF function and the monoamine system, we also review current evidence surrounding diet and supplementation (e.g., flavonoids) on BDNF-mediated brain functions.