The role of dopamine in bipolar disorder

Immature dentate gyrus: an endophenotype of neuropsychiatric disorders

Adequate maturation of neurons and their integration into the hippocampal circuit is crucial for normal cognitive function and emotional behavior, and disruption of this process could cause disturbances in mental health. Previous reports have shown that mice heterozygous for a null mutation in α -CaMKII, which encodes a key synaptic plasticity molecule, display abnormal behaviors related to schizophrenia and other psychiatric disorders. In these mutants, almost all neurons in the dentate gyrus are arrested at a pseudoimmature state at the molecular and electrophysiological levels, a phenomenon defined as "immature dentate gyrus (iDG)." To date, the iDG phenotype and shared behavioral abnormalities (including working memory deficit and hyperlocomotor activity) have been discovered in Schnurri-2 knockout, mutant SNAP-25 knock-in, and forebrain-specific calcineurin knockout mice. In addition, both chronic fluoxetine treatment and pilocarpine-induced seizures reverse the neuronal maturation, resulting in the iDG phenotype in wild-type mice. Importantly, an iDG-like phenomenon was observed in post-mortem analysis of brains from patients with schizophrenia/bipolar disorder. Based on these observations, we proposed that the iDG is a potential endophenotype shared by certain types of neuropsychiatric disorders. This review summarizes recent data describing this phenotype and discusses the data's potential implication in elucidating the pathophysiology of neuropsychiatric disorders.

Treatment of bipolar disorder

We review recent developments in the acute and long-term treatment of bipolar disorder and identify promising future routes to therapeutic innovation. Overall, advances in drug treatment remain quite modest. Antipsychotic drugs are effective in the acute treatment of mania; their efficacy in the treatment of depression is variable with the clearest evidence for quetiapine. Despite their widespread use, considerable uncertainty and controversy remains about the use of antidepressant drugs in the management of depressive episodes. Lithium has the strongest evidence for long-term relapse prevention; the evidence for anticonvulsants such as divalproex and lamotrigine is less robust and there is much uncertainty about the longer term benefits of antipsychotics. Substantial progress has been made in the development and assessment of adjunctive psychosocial interventions. Long-term maintenance and possibly acute stabilisation of depression can be enhanced by the combination of psychosocial treatments with drugs. The development of future treatments should consider both the neurobiological and psychosocial mechanisms underlying the disorder. We should continue to repurpose treatments and to recognise the role of serendipity. We should also investigate optimum combinations of pharmacological and psychotherapeutic treatments at different stages of the illness. Clarification of the mechanisms by which different treatments affect sleep and circadian rhythms and their relation with daily mood fluctuations is likely to help with the treatment selection for individual patients. To be economically viable, existing psychotherapy protocols need to be made briefer and more efficient for improved scalability and sustainability in widespread implementation.

Major channels involved in neuropsychiatric disorders and therapeutic perspectives

Voltage-gated ion channels are important mediators of physiological functions in the central nervous system. The cyclic activation of these channels influences neurotransmitter release, neuron excitability, gene transcription, and plasticity, providing distinct brain areas with unique physiological and pharmacological response. A growing body of data has implicated ion channels in the susceptibility or pathogenesis of psychiatric diseases. Indeed, population studies support the association of polymorphisms in calcium and potassium channels with the genetic risk for bipolar disorders (BPDs) or schizophrenia. Moreover, point mutations in calcium, sodium, and potassium channel genes have been identified in some childhood developmental disorders. Finally, antibodies against potassium channel complexes occur in a series of autoimmune psychiatric diseases. Here we report recent studies assessing the role of calcium, sodium, and potassium channels in BPD, schizophrenia, and autism spectrum disorders, and briefly summarize promising pharmacological strategies targeted on ion channels for the therapy of mental illness and related genetic tests.

Genetic and neurocognitive foundations of emotion abnormalities in bipolar disorder

INTRODUCTION

Bipolar Disorder (BD) is a serious mood disorder, the aetiology of which is still unclear. The disorder is characterised by extreme mood variability in which patients fluctuate between markedly euphoric, irritable, and elevated states to periods of severe depression. The current research literature shows that BD patients demonstrate compromised neurocognitive ability in addition to these mood symptoms. Viable candidate genes implicated in neurocognitive and socioemotional processes may explain the development of these core emotion abnormalities. Additionally, links between faulty neurocognition and impaired socioemotional ability complement genetic explanations of BD pathogenesis. This review examines associations between cognition indexing prefrontal neural regions and socioemotional impairments including emotion processing and regulation. A review of the effect of COMT and TPH2 on these functions is also explored.

METHODS

Major computer databases including PsycINFO, Google Scholar, and Medline were consulted in order to conduct a comprehensive review of the genetic and cognitive literature in BD.

RESULTS

This review determines that COMT and TPH2 genetic variants contribute susceptibility to abnormal prefrontal neurocognitive function which oversees the processing and regulation of emotion. This provides for greater understanding of some of the emotional and cognitive symptoms in BD.

CONCLUSIONS

Current findings in this direction show promise, although the literature is still in its infancy and further empirical research is required to investigate these links explicitly.

Human mild traumatic brain injury decreases circulating branched-chain amino acids and their metabolite levels

The pathophysiology of traumatic brain injury (TBI) is complex and not well understood. Because pathophysiology has ramifications for injury progression and outcome, we sought to identify metabolic cascades that are altered after acute human mild and severe TBI. Because catabolism of branched-chain amino acids (BCAAs; i.e., valine, isoleucine, and leucine) leads to glucose and energy metabolism, and neurotransmitter synthesis and availability, we investigated BCAA metabolites in plasma samples collected within 24 h of injury from mild TBI (Glasgow Coma Scale [GCS] score >12), severe TBI (GCS ≤8), orthopedic injury, and healthy volunteers. We report decreased levels of all three BCAAs in patients with mild TBI relative to healthy volunteers, while these BCAAs levels in patients with severe TBI were further reduced compared with all groups. Orthopedic patients exhibited reductions in BCAA comparable to those in patients with mild TBI. The decrease in patients with mild and severe TBI persisted for derivatives of BCAA catabolic intermediates. Only plasma levels of methylglutarylcarnitine, a derivative of a leucine metabolite, were increased in patients with severe TBI compared with all other groups. Notably, logistic regression combination of three BCAA metabolites whose levels were changed by 24 h post-injury provided prognostic value (area under the curve=0.92) in identifying patients with severe TBI in whom elevated intracranial pressure (≥25 mm Hg) developed. These changes suggest alteration of BCAA metabolism after TBI may contribute to decreased energy production and neurotransmitter synthesis and may contribute to TBI pathophysiology. Supplementation of BCAAs and/or their metabolites may reduce TBI pathology and improve outcome.

Neuropsychiatric adverse events of varenicline: a systematic review of published reports

INTRODUCTION

Over the past years, the impact of varenicline in patients with mental illness has been debated as serious neuropsychiatric adverse events (AEs) have been reported with varenicline use.

AIM

To identify and summarize published case reports of neuropsychiatric AEs ascribed to varenicline and to determine potential risk factors for these AEs.

METHODS

A literature search of MEDLINE, the Cochrane Library, EMBASE, and PsychInfo database was conducted for case reports concerning the neuropsychiatric AEs of varenicline published in English from 2006 (approval year by the US Food and Drug Administration and the Dutch Medicines Evaluation Board) to January 1, 2012.

RESULTS

We identified 25 published cases. In most reports, patients had been admitted to psychiatric hospitals with serious neuropsychiatric AEs due to varenicline. The average patient age was 46.4 years, and 56% were men; 68% of patients had a psychiatric history. The onset of symptoms started 2 days to 3 months after the initiation of varenicline. One report described completed suicide in a man with no psychiatric history. In most cases (84%), the neuropsychiatric symptoms resolved after the discontinuation of varenicline. Analysis of all reports using the Naranjo causality scale, a method for estimating the probability of adverse drug reactions, indicated probable causality in 76% of the cases and definite causality in 12% of cases.

CONCLUSION

Varenicline is associated with an increased risk of serious neuropsychiatric AEs, especially in patients with a psychiatric illness. It is strongly recommended that varenicline be administered only to mentally stable patients and under close monitoring.

Potential mechanisms of action of lithium in bipolar disorder. Current understanding

Lithium has been used for over half a century for the treatment of bipolar disorder as the archetypal mood stabilizer, and has a wealth of empirical evidence supporting its efficacy in this role. Despite this, the specific mechanisms by which lithium exerts its mood-stabilizing effects are not well understood. Given the inherently complex nature of the pathophysiology of bipolar disorder, this paper aims to capture what is known about the actions of lithium ranging from macroscopic changes in mood, cognition and brain structure, to its effects at the microscopic level on neurotransmission and intracellular and molecular pathways. A comprehensive literature search of databases including MEDLINE, EMBASE and PsycINFO was conducted using relevant keywords and the findings from the literature were then reviewed and synthesized. Numerous studies report that lithium is effective in the treatment of acute mania and for the long-term maintenance of mood and prophylaxis; in comparison, evidence for its efficacy in depression is modest. However, lithium possesses unique anti-suicidal properties that set it apart from other agents. With respect to cognition, studies suggest that lithium may reduce cognitive decline in patients; however, these findings require further investigation using both neuropsychological and functional neuroimaging probes. Interestingly, lithium appears to preserve or increase the volume of brain structures involved in emotional regulation such as the prefrontal cortex, hippocampus and amygdala, possibly reflecting its neuroprotective effects. At a neuronal level, lithium reduces excitatory (dopamine and glutamate) but increases inhibitory (GABA) neurotransmission; however, these broad effects are underpinned by complex neurotransmitter systems that strive to achieve homeostasis by way of compensatory changes. For example, at an intracellular and molecular level, lithium targets second-messenger systems that further modulate neurotransmission. For instance, the effects of lithium on the adenyl cyclase and phospho-inositide pathways, as well as protein kinase C, may serve to dampen excessive excitatory neurotransmission. In addition to these many putative mechanisms, it has also been proposed that the neuroprotective effects of lithium are key to its therapeutic actions. In this regard, lithium has been shown to reduce the oxidative stress that occurs with multiple episodes of mania and depression. Further, it increases protective proteins such as brain-derived neurotrophic factor and B-cell lymphoma 2, and reduces apoptotic processes through inhibition of glycogen synthase kinase 3 and autophagy. Overall, it is clear that the processes which underpin the therapeutic actions of lithium are sophisticated and most likely inter-related.

Mood stabilizer lithium inhibits amphetamine-increased 4-hydroxynonenal-protein adducts in rat frontal cortex

Recent studies indicate that bipolar disorder is associated with mitochondrial dysfunction and oxidative stress. Previous studies in our laboratory have shown that the mood stabilizer lithium inhibits oxidative stress. The α,β-unsaturated aldehyde 4-hydroxy-2-nonenal (4-HNE), a major product of lipid peroxidation, is able to exert cytotoxicity and disturb cellular function by forming protein adducts. The purpose of this study is to determine whether chronic lithium treatment prevents 4-HNE-protein adduction in an amphetamine-induced hyperactive mania-like model. We found that repeated amphetamine stimulation significantly induced hyperactive behaviour, decreased activities of mitochondrial complexes I and III, and increased 4-HNE-protein adducts in rat frontal cortex, and that chronic lithium treatment inhibited both amphetamine-induced hyperactivity and 4-HNE-protein adduction. Monoamine neurotransmitters are involved in the aetiology and pathology of bipolar disorder and other psychiatric diseases, and also contribute significantly to amphetamine-induced behavioural effects. Vesicular monoamine transporter 2 (VMAT2) is critical in packaging monoamine neurotransmitters. We found that 4-HNE can form protein adducts with VMAT2. Repeated amphetamine stimulation significantly increased 4-HNE-VMAT2 adducts, while chronic lithium treatment reduced amphetamine-increased 4-HNE-VMAT2 adducts in rat frontal cortex. Our findings suggest that chronic lithium treatment may inhibit amphetamine-induced hyperactive mania-like behaviour by preventing 4-HNE-VMAT2 adduction. This finding also indicates that prevention of 4-HNE-VMAT2 adduction may contribute in part to the pharmacological action of lithium for the treatment of bipolar disorder.

Polymorphisms in AKR1C4 and HSD3B2 and differences in serum DHEAS and progesterone are associated with paranoid ideation during mania or hypomania in bipolar disorder

Paranoia is commonly a mood-incongruent psychotic symptom of mania which may be related to dopamine dysregulation. Progesterone and its metabolite allopregnanolone (ALLO) have been found in animals to antagonize the effects of dopamine. We therefore examined serum progesterone, its endogenous antagonist DHEAS and polymorphisms of the genes coding for certain steroidogenetic enzymes (AKR1C4, HSD3B2, and SRD5A1) in 64 males and 96 females with bipolar 1 or 2 disorder with or without paranoid ideation during mood elevation. Euthymic morning serum progesterone, DHEAS and cortisol concentrations were measured in males and in premenopausal women who were in follicular phase and not taking oral contraceptives. In women only, SNPs in AKR1C4 reduced the likelihood of having exhibited paranoid ideation by circa 60%. The haplotype of all 4 SNPs in the AKR1C4 gene reduced the risk of exhibiting paranoia by 80% (OR 0.19, 95% CI 0.06-0.61, p=0.05). A history of paranoid ideation was not, however, related to progesterone or DHEAS concentration. Serum DHEAS and progesterone concentrations were lower in men who had shown paranoid ideation during mania/hypomania compared with those who had not (F=7.30, p=0.006) however this was not coupled to polymorphisms in the selected genes. The ancestral G in rs4659174 in HSD3B2 was in men associated with a lower risk of paranoid ideation (likelihood ratio χ(2) 3.97, p=0.046, OR 0.31 (95% CI 0.10-0.96)) but did not correlate with hormone concentrations. Hence, gene variants in the steroidogenetic pathway and steroids concentration differences may be involved in the susceptibility to paranoia during mood elevation.

Overlapping prefrontal systems involved in cognitive and emotional processing in euthymic bipolar disorder and following sleep deprivation: a review of functional neuroimaging studies

Prefrontal cortex (PFC) mediated cognitive and emotional processing deficits in bipolar disorder lead to functional limitations even during periods of mood stability. Alterations of sleep and circadian functioning are well-documented in bipolar disorder, but there is little research directly examining the mechanistic role of sleep and/or circadian rhythms in the observed cognitive and emotional processing deficits. We systematically review the cognitive and emotional processing deficits reliant upon PFC functioning of euthymic patients with bipolar disorder and in healthy individuals deprived of sleep. The evidence from two parallel lines of investigation suggests that sleep and circadian rhythms may be involved in the cognitive and emotional processing deficits seen in bipolar disorder through overlapping neurobiological systems. We discuss current models of bipolar highlighting the PFC-limbic connections and discuss inclusion of sleep-related mechanisms. Sleep and circadian dysfunction is a core feature of bipolar disorder and models of neurobiological abnormalities should incorporate chronobiological measures. Further research into the role of sleep and circadian rhythms in cognition and emotional processing in bipolar disorder is warranted.

Brain glutamate levels measured by magnetic resonance spectroscopy in patients with bipolar disorder: a meta-analysis

OBJECTIVES

Bipolar disorder (BD) is a common and highly disabling disease characterized by substantial cognitive and functional impairment. The exact neurobiological mechanisms underlying the expression of symptoms in this condition remain unknown but there is growing evidence that glutamate might play an important role. Using proton magnetic resonance spectroscopy (¹H-MRS), a number of studies have examined brain glutamate/glutamine levels in patients with bipolar disorder, but they have produced conflicting results. The objective of this paper was to conduct a systematic review and meta-analysis of the literature on brain glutamate/glutamine in BD as measured by ¹H-MRS.

METHODS

A Medline search for the period January 1980-April 2010 was conducted to identify published studies that used ¹H-MRS to measure glutamate + glutamine (Glx), the Glx/creatine (Cr) ratio, glutamate (Glu), or the Glu/Cr ratio in any brain region in adult or child/adolescent patients with BD and healthy subjects. A meta-analysis of the pooled data was conducted.

RESULTS

BD patients were found to have increased Glx compared to healthy subjects when all brain areas were combined. This finding remained true in medicated and non-medicated patients, and in frontal brain areas in adults. There was a non-significant trend (p = 0.09) for an increase in whole-brain Glx/Cr and Glu in patients compared with healthy subjects. No significant difference was found in Glu/Cr.

CONCLUSIONS

The results of this meta-analysis suggest that brain Glx levels are elevated in BD patients and support the idea that glutamate might play an important role in the pathophysiology of BD.

COMT polymorphisms as predictors of cognitive dysfunction during manic and mixed episodes in bipolar I disorder

OBJECTIVE

The dopaminergic system plays an important role in the prefrontal cortex (PFC) and is believed to mediate cognitive dysfunction (CD) in bipolar disorder (BD). The enzyme catechol-O-methyltransferase (COMT) is involved in the catabolism of dopamine in the PFC, and an association between COMT single nucleotide polymorphisms (SNPs) and BD has been reported. COMT SNPs have also been associated with executive and working memory performance in healthy subjects, patients with schizophrenia, and euthymic BD patients. The objective of this study was to investigate the association between COMT SNPs and acute CD during BD mood episodes.

METHODS

Seventy-two symptomatic, medication-free subjects with bipolar I disorder (BD-I) and 76 healthy controls were evaluated using neuropsychological tests, and genotyped for COMT SNPs rs4680 and rs165599.

RESULTS

Patients undergoing mania and mixed episodes carrying the COMT allele G had better performance on executive function, memory, verbal fluency, and intelligence tests. Moreover, an interaction was detected between the COMT allele G and the Young Mania Rating Scale in BD CD.

CONCLUSIONS

Allele G from COMT SNPs rs4680 and rs165599 may represent reliable state-dependent predictors of global CD during manic and mixed episodes in BD. Further studies in larger samples are necessary to confirm these findings.

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.

Memory mood congruency phenomenon in bipolar I disorder and major depression disorder patients

The objective of the present study was to evaluate memory performance in tasks with and without affective content (to confirm the mood congruency phenomenon) in acutely admitted patients with bipolar I disorder (BD) and major depression disorder (MDD) and in healthy participants. Seventy-eight participants (24 BD, 29 MDD, and 25 healthy controls) were evaluated. Three word lists were used as the memory task with affective content (positive, negative and indifferent). Psychiatric symptoms were also evaluated with rating scales (Young Mania Rating Scale for mania and Hamilton Depression Rating Scale for depression). Patients were selected during the first week of hospitalization. BD patients showed higher scores in the word span with positive tone than MDD patients and healthy controls (P = 0.002). No other difference was observed for tests with affective tone. MDD patients presented significantly lower scores in the Mini-Mental State Exam, logical memory test, visual recognition span, and digit span, while BD patients presented lower scores in the visual recognition test and digit span. Mood congruency effect was found for word span with positive tone among BD patients but no similar effect was observed among MDD patients for negative items. MDD patients presented more memory impairment than BD patients, but BD patients also showed memory impairment.

The double-edged sword of goal engagement: consequences of goal pursuit in bipolar disorder

A series of studies suggest that bipolar disorder is related to high sensitivity to incentives and that incentive sensitivity (or sensitivity of the approach system) can predict the course of mania. Incentive sensitivity in bipolar disorder seems to be related to two processes: a tendency to invest in difficult-to-attain goals and an over-reactivity to cues of goal progress versus thwarting. Both of those processes appear relevant to symptom generation. Hence, bipolar disorder seems related to a greater emphasis on reaching goals and also a problematic reactivity to reaching those highly desired goals. We suggest directions for treatment development focused on these issues in goal regulation.

Interpreting magnetic resonance imaging findings in bipolar disorder

The episodic nature of bipolar disorder together with the ostensibly polar extremes of mania and depression have favored the acceptance of a functional model postulating regionally disturbed brain activity returning to normal with time or treatment. Seemingly contrary to that view, anatomical imaging studies have demonstrated abnormalities in brain structure which could reflect neurodegeneration or represent disturbed neuronal development. Resolution may come from an appreciation of adult neurogenesis, especially given the neuroprotective properties of drugs, such as lithium and their effects on brain volume. The brain regions vulnerable to structural changes also show evidence of dysfunction, giving rise to corticolimbic dysregulation interpretations of bipolar disorder. This article reviews the structural and functional magnetic resonance imaging data in bipolar disorder. Its focus is on the interpretation of findings in light of recent developments in the fields of neurobiology and image analysis, with particular attention paid to both the confounding effects of medication and the baseline energy state of the brain.

Imaging brain signal transduction and metabolism via arachidonic and docosahexaenoic acid in animals and humans

The polyunsaturated fatty acids (PUFAs), arachidonic acid (AA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3), important second messengers in brain, are released from membrane phospholipid following receptor-mediated activation of specific phospholipase A(2) (PLA(2)) enzymes. We developed an in vivo method in rodents using quantitative autoradiography to image PUFA incorporation into brain from plasma, and showed that their incorporation rates equal their rates of metabolic consumption by brain. Thus, quantitative imaging of unesterified plasma AA or DHA incorporation into brain can be used as a biomarker of brain PUFA metabolism and neurotransmission. We have employed our method to image and quantify effects of mood stabilizers on brain AA/DHA incorporation during neurotransmission by muscarinic M(1,3,5), serotonergic 5-HT(2A/2C), dopaminergic D(2)-like (D(2), D(3), D(4)) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors, and effects of inhibition of acetylcholinesterase, of selective serotonin and dopamine reuptake transporter inhibitors, of neuroinflammation (HIV-1 and lipopolysaccharide) and excitotoxicity, and in genetically modified rodents. The method has been extended for the use with positron emission tomography (PET), and can be employed to determine how human brain AA/DHA signaling and consumption are influenced by diet, aging, disease and genetics.

Varenicline-induced psychotic depressive episode in a patient with bipolar disorder

Varenicline is a relatively novel medication for smoking cessation. Increased neuropsychiatric symptoms have been reported with its use and it is listed among drugs with a black box warning. History of a psychiatric diagnosis is suggested to be a vulnerability factor for the development of some psychiatric side effects with its use. However, empirical evidence to support this point is very limited. Here, we report the case of a bipolar patient who developed a depressive episode with psychotic features immediately after varenicline use. Clinicians should be careful about the varenicline-induced neuropsychiatric effects. Healthcare professionals can provide an important role in helping to prevent and manage worsening psychiatric symptoms.

Structural studies of the hypothalamus and its nuclei in mood disorders

A large body of evidence indicates that the hypothalamus is involved in pathogenetic mechanisms of mood disorders. It has been suggested that functional abnormalities of the hypothalamus are associated with structural hypothalamic changes. Structural neuroimaging allows in vivo investigation of the hypothalamus that may shed light on the underlying pathogenetic mechanisms of unipolar and bipolar disorder. Clearly, the detection of subtle structural cerebral changes depends on the limitations of the neuroimaging technique used. Making a comprehensive database search, we reviewed the literature on hypothalamic macrostructure in affective disorders, addressing the specific question of what structural magnetic resonance imaging might be expected to show. Studies with convincing methodology, although rare, suggest a global volume decrease in the hypothalamus in affective disorders, a decrease which is not shown by the two specific nuclei investigated, the paraventricular and supraoptic nuclei. We discuss the implications of these findings and provide directions for future research.

Antipsychotics in the treatment of bipolar disorder

Atypical antipsychotics have an important role in the acute and maintenance treatment of bipolar disorder. While robust evidence supports the efficacy of these agents in the treatment of mania and in the prevention of manic relapse, few atypical antipsychotics have shown efficacy in the treatment or prevention of depressive episodes. These agents pose a lower risk of extrapyramidal side effects compared to typical neuroleptics, but carry a significant liability for weight gain and other metabolic side effects such as hyperglycemia and hyperlipidemia. More comparative effectiveness studies are needed to assess the optimal treatment regimens, including the relative benefits and risks of antipsychotics versus mood stabilizers. The exploration of the molecular mechanisms of antipsychotics has helped to shed further light on the underlying neurobiology of bipolar disorder, since these compounds target systems thought to be key to the pathophysiology of bipolar disorder. In addition to modulating monoaminergic neurotransmission, atypical antipsychotics appear to share properties with mood-stabilizing agents known to alter intracellular signal transduction leading to changes in neuronal activity and gene expression. Atypical antipsychotic drugs have been shown to exhibit neuroprotective properties that are mediated by upregulation of trophic and cellular resilience factors. Building on our understanding of existing therapeutics, especially as it relates to underlying disease pathology, newer "plasticity enhancing" strategies hold promise for future treatments of bipolar disorder.

Underlying neurobiology and clinical correlates of mania status after subthalamic nucleus deep brain stimulation in Parkinson's disease: a review of the literature

Deep brain stimulation (DBS) is a novel and effective surgical intervention for refractory Parkinson's disease (PD). The authors review the current literature to identify the clinical correlates associated with subthalamic nucleus (STN) DBS-induced hypomania/mania in PD patients. Ventromedial electrode placement has been most consistently implicated in the induction of STN DBS-induced mania. There is some evidence of symptom amelioration when electrode placement is switched to a more dorsolateral contact. Additional clinical correlates may include unipolar stimulation, higher voltage (>3 V), male sex, and/or early-onset PD. STN DBS-induced psychiatric adverse events emphasize the need for comprehensive psychiatric presurgical evaluation and follow-up in PD patients. Animal studies and prospective clinical research, combined with advanced neuroimaging techniques, are needed to identify clinical correlates and underlying neurobiological mechanisms of STN DBS-induced mania. Such working models would serve to further our understanding of the neurobiological underpinnings of mania and contribute valuable new insight toward development of future DBS mood-stabilization therapies.

Mitochondria, oligodendrocytes and inflammation in bipolar disorder: evidence from transcriptome studies points to intriguing parallels with multiple sclerosis

Gene expression studies of bipolar disorder (BPD) have shown changes in transcriptome profiles in multiple brain regions. Here we summarize the most consistent findings in the scientific literature, and compare them to data from schizophrenia (SZ) and major depressive disorder (MDD). The transcriptome profiles of all three disorders overlap, making the existence of a BPD-specific profile unlikely. Three groups of functionally related genes are consistently expressed at altered levels in BPD, SZ and MDD. Genes involved in energy metabolism and mitochondrial function are downregulated, genes involved in immune response and inflammation are upregulated, and genes expressed in oligodendrocytes are downregulated. Experimental paradigms for multiple sclerosis demonstrate a tight link between energy metabolism, inflammation and demyelination. These studies also show variabilities in the extent of oligodendrocyte stress, which can vary from a downregulation of oligodendrocyte genes, such as observed in psychiatric disorders, to cell death and brain lesions seen in multiple sclerosis. We conclude that experimental models of multiple sclerosis could be of interest for the research of BPD, SZ and MDD.

Creativity and executive function across manic, mixed and depressive episodes in bipolar I disorder

INTRODUCTION

Creativity is a complex construct involving affective and cognitive components. Bipolar Disorder (BD) has been associated with creativity and is characterized by a wide range of affective and cognitive symptoms. Although studies of creativity in BD have tended to focus on creativity as a trait variable in medicated euthymic patients, it probably fluctuates during symptomatic states of BD. Since creativity is known to involve key affective and cognitive components, it is plausible to speculate that cognitive deficits and symptoms present in symptomatic BD could interfere with creativity.

MATERIAL AND METHODS

Sixty-seven BD type I patients medication free, age 18-35 years and experiencing a maniac, mixed, or depressive episodes, were assessed for creativity, executive functioning, and intelligence.

RESULTS

Manic and mixed state patients had higher creativity scores than depressive individuals. Creativity was influenced by executive function measures only in manic patients. Intelligence did not influence creativity for any of the mood episode types.

CONCLUSION

We propose that creativity in BD might be linked to the putative hyperdopaminergic state of mania and be dependent on intact executive function. Future studies should further explore the role of dopaminergic mechanisms in creativity in BD.

Chronic valproate treatment blocks D2-like receptor-mediated brain signaling via arachidonic acid in rats

BACKGROUND AND OBJECTIVE

Hyperdopaminergic signaling and an upregulated brain arachidonic acid (AA) cascade may contribute to bipolar disorder (BD). Lithium and carbamazepine, FDA-approved for the treatment of BD, attenuate brain dopaminergic D(2)-like (D(2), D(3), and D(4)) receptor signaling involving AA when given chronically to awake rats. We hypothesized that valproate (VPA), with mood-stabilizing properties, would also reduce D(2)-like-mediated signaling via AA.

METHODS

An acute dose of quinpirole (1 mg/kg) or saline was administered to unanesthetized rats that had been treated for 30 days with a therapeutically relevant dose of VPA (200 mg/kg/day) or vehicle. Regional brain AA incorporation coefficients, k*, and incorporation rates, J(in), markers of AA signaling and metabolism, were measured by quantitative autoradiography after intravenous [1-(14)C]AA infusion. Whole brain concentrations of prostaglandin (PG)E(2) and thromboxane (TX)B(2) also were measured.

RESULTS

Quinpirole compared to saline significantly increased k* in 40 of 83 brain regions, and increased brain concentrations of PGE(2) in chronic vehicle-treated rats. VPA treatment by itself reduced concentrations of plasma unesterified AA and whole brain PGE(2) and TXB(2), and blocked the quinpirole-induced increments in k* and PGE(2).

CONCLUSION

These results further provide evidence that mood stabilizers downregulate brain dopaminergic D(2)-like receptor signaling involving AA.

Dopamine sudden depletion as a model for mixed depression

Up to date research on Bipolar Disorders' phenomenology is in keeping with early descriptions made by E. Kraëpelin regarding the overlap in clinical presentation of both manic and depressive symptoms, namely, mixed states. The latter constitute a highly prevalent and characteristic clinical presentation of Bipolar Disorders' and entail therapeutic difficulties, prognostic implications and increased suicidal risk. Notwithstanding, mixed states', more specifically mixed depression, have been underestimated and bypassed to the point where currently neither diagnostic criteria nor specific therapeutic recommendations are provided. In addition to the lack of agreement on nosography and diagnostic criteria, mixed depression is usually excluded from Bipolar Disorders' neurobiological models. Furthermore, renewed interest in the role of dopamine in Bipolar Disorders' physiopathology has left aside hypothesis that may account for the aforementioned clinical presentation. Interestingly enough, other syndromes arising from sudden dopamine depletion such as neuroleptic dysphoria or withdrawal syndromes from dopaminergic drugs, bear remarkable clinical similarities with mixed depression. These syndromes have been subject of further research and may thus provide a model for mixed states' physiopathology. Indeed, this article accounts for clinical similarities between mixed depression, neuroleptic induced dysphoria, and other behavioural syndromes arising from sudden dopamine depletion. After reviewing neurochemical basis of such syndromes we present, to the best of our knowledge, the first neurobiological hypothesis for mixed depression. Specifically, such hypothesis regards over activation symptoms as auto regulatory attempts to compensate for sudden dopaminergic depletion. This hypothesis provides with a beginning step for the neglected problem of mixed depression, a non-antithetic link between the dopaminergic hypothesis for both manic and depressive symptoms, a plausible explanation regarding inter individual variability to mixed depression susceptibility, and suggests new approaches for the development of novel treatments in which dopamine dysregulation should be targeted.

Therapeutic use of omega-3 fatty acids in bipolar disorder

Bipolar disorder (BD) is a severe, chronic affective disorder, associated with significant disability, morbidity and premature mortality. Omega-3 polyunsaturated fatty acids (PUFAs) play several important roles in brain development and functioning. Evidence from animal models of dietary omega-3 (n-3) PUFA deficiency suggest that these fatty acids are relevant to promote brain development and to regulate behavioral and neurochemical aspects related to mood disorders, such as stress responses, depression and aggression, as well as dopaminergic content and function. Preclinical and clinical evidence suggests roles for PUFAs in BD. n-3 PUFAs seem to be an effective adjunctive treatment for unipolar and bipolar depression, but further large-scale, well-controlled trials are needed to examine its clinical utility in BD. The use of n-3 as a mood stabilizer among BD patients is discussed here. This article summarizes the molecular pathways related to the role of n-3 as a neuroprotective and neurogenic agent, with a specific focus on BDNF. It is proposed that the n-3-BDNF association is involved in the pathophysiology of BD and represents a promising target for developing a novel class of rationally devised therapies.

Neurochemical characterization of the tree shrew dorsal striatum

The striatum is a major component of the basal ganglia and is associated with motor and cognitive functions. Striatal pathologies have been linked to several disorders, including Huntington’s, Tourette’s syndrome, obsessive–compulsive disorders, and schizophrenia. For the study of these striatal pathologies different animal models have been used, including rodents and non-human primates. Rodents lack on morphological complexity (for example, the lack of well defined caudate and putamen nuclei), which makes it difficult to translate data to the human paradigm. Primates, and especially higher primates, are the closest model to humans, but there are ever-increasing restrictions to the use of these animals for research. In our search for a non-primate animal model with a striatum that anatomically (and perhaps functionally) can resemble that of humans, we turned our attention to the tree shrew. Evolutionary genetic studies have provided strong data supporting that the tree shrews (Scadentia) are one of the closest groups to primates, although their brain anatomy has only been studied in detail for specific brain areas. Morphologically, the tree shrew striatum resembles the primate striatum with the presence of an internal capsule separating the caudate and putamen, but little is known about its neurochemical composition. Here we analyzed the expression of calcium-binding proteins, the presence and distribution of the striosome and matrix compartments (by the use of calbindin, tyrosine hydroxylase, and acetylcholinesterase immunohistochemistry), and the GABAergic system by immunohistochemistry against glutamic acid decarboxylase and Golgi impregnation. In summary, our results show that when compared to primates, the tree shrew dorsal striatum presents striking similarities in the distribution of most of the markers studied, while presenting some marked divergences when compared to the rodent striatum.

Four mood stabilizers commonly induce FEZ1 expression in human astrocytes

OBJECTIVES

  Mood stabilizers influence the morphology, chemotaxis, and survival of neurons, which are considered to be related to the mood-stabilizing effects of these drugs. Although previous studies suggest glial abnormalities in patients with bipolar disorder and an effect of mood stabilizers on certain genes in astrocytes, less is known about the effects of mood stabilizers in astrocytes than in neurons. The present study identifies a common underlying response to mood stabilizers in astrocytes.

METHODS

  Human astrocyte-derived cells (U-87 MG) were treated with the four most commonly used mood stabilizers (lithium, valproic acid, carbamazepine, and lamotrigine) and subjected to microarray gene expression analyses. The most prominently regulated genes were validated by qRT-PCR and western blot analysis. The intercellular localization of one of these regulated genes, fasciculation and elongation protein zeta 1 (FEZ1), was evaluated by immunofluorescence staining.

RESULTS

  The microarray data indicated that FEZ1 was the only gene commonly induced by the four mood stabilizers in human astrocyte-derived cells. An independent experiment confirmed astrocytic FEZ1 induction at both the transcript and protein levels following mood stabilizer treatments. FEZ1 localized to the cytoplasm of transformed and primary astrocytes from the human adult brain.

CONCLUSIONS

  Our data suggest that FEZ1 may play important roles in human astrocytes, and that mood stabilizers might exert their cytoprotective and mood-stabilizing effects by inducing FEZ1 expression in astrocytes.

Sensory gating deficit is associated with catechol-O-methyltransferase polymorphisms in bipolar disorder

OBJECTIVES. Recent studies have evidenced that bipolar patients show a sensory gating deficit (P50). Among the neural systems that could be influencing this electrophysiological phenotype, dopamine seems to play an important role. We hypothesize that catechol-O-methyltransferase (COMT), the main metabolizer of dopamine in prefrontal cortex, is related to this deficit. METHODS. We selected three polymorphisms in COMT gene: rs2075507 (Promoter 2 region), Val158Met (rs4680) and rs165599 (3' region). A case-control study was performed in 784 controls and 238 bipolar patients. Besides, 122 euthymic bipolar subjects and 95 healthy subjects carried out a sensory gating task (P50). RESULTS. Polymorphism rs165599 in the COMT gene was associated with susceptibility to bipolar disorder (BD), mainly in women (AG: OR = 1.46; GG: OR = 1.84; P = 0.03). In the female group, haplotype AAG was associated with an OR = 7.6. Subjects who carried Val158 allele evidenced a deficit in suppression (P = 0.046) and rs165599 allele G carriers (mainly in homozygosis) had a bigger S2 amplitude and a higher S2/S1 ratio (1.6(e-5) < P < 0.01). Not a single association was proven in the control group. CONCLUSIONS. Our results support the association of the COMT gene with BD and with one of its potential endophenotypes, auditory sensory gating deficit, measured by the P50 paradigm.

Cognitive manic symptoms associated with the P2RX7 gene in bipolar disorder

OBJECTIVE

  Several genetic loci have been suggested to be associated with bipolar disorder but results have been inconsistent. Studying associations between bipolar symptoms and candidate genes may better expose this relationship. Here we investigate the association between bipolar key symptoms and the P2RX7 gene.

METHODS

  Key symptoms of mania were rated in two sets of medicated bipolar disorder patients (n=171 and n=475) at two specialized outpatient clinics for affective disorders and three regular psychiatric outpatient units in Sweden. The relationships between all manic symptoms according to DSM-IV were entered in a principal component analysis. We used a case-case model to reduce the genetic heterogeneity and tested associations between four factors related to manic symptoms and their association to four single nucleotide polymorphisms in the P2RX7 gene.

RESULTS

  The combination of the cognitive symptoms, distractibility, talkativeness, and thought disorder was significantly associated with rs1718119 in the P2RX7 gene in Set 1 [odds ratio (OR) = 1.78; p=0.011]. The association was re-tested in the second set (OR = 1.42; p=0.009). In the total sample, the association was even stronger (OR = 1.49; p<0.001). None of the other factors was associated with the P2RX7 gene. Within the first factor, the distractibility symptom accounted for a significant portion of the association to rs1718119 (p=0.016).

CONCLUSION

  There is an association between specific symptoms of bipolar disorder and the P2RX7 gene. This finding may open up new approaches to elucidating the neurobiology behind bipolar symptoms.

Recurrence of bipolar mania is associated with catechol-O-methyltransferase Val(108/158)Met polymorphism

BACKGROUND

Catechol-O-methyltransferase (COMT) inactivates catecholamines, and a G-A transition in the COMT gene (rs4680) influences the enzyme activity and the interaction between cortical and subcortical dopaminergic neurotransmission. In patients affected by bipolar disorder rs4680 can influence antidepressant response and the propensity to develop psychotic symptoms, with the Met/Met genotype exerting a protective role. The same genotype could influence other dopamine-associated psychopathological features, such as mania.

METHODS

We genotyped rs4680 in a sample of 163 patients affected by bipolar disorder type I, and assessed the personal history of recurrence of the illness.

RESULTS

We observed a significant association between homozygosis for the rs4680 COMT low-activity variant and a reduced recurrence of manic, but not depressive, episodes during the course of the illness.

CONCLUSIONS

We suggest that rs4680 could be an inheritable aspect of the mechanisms of dopamine regulation that influence the individual susceptibility of patients with bipolar disorder to develop manic episodes of illness.

Behavioral and pharmacological assessment of a potential new mouse model for mania

Bipolar disorder (BPD) is a devastating long-term disease for which a significant symptom is mania. Rodent models for mania include psychostimulant-induced hyperactivity and single gene alterations, such as in the Clock or DAT genes, but there is still a pressing need for additional models. Recently, our lab isolated a line of mice, termed Madison (MSN), that exhibit behavioral characteristics that may be analogous to symptoms of mania. In this study we quantified possible traits for mania and tested the response to common anti-BPD drugs in altering the behavioral profiles observed in this strain. Relative to other mouse lines, MSN mice showed significant elevations of in-cage hyperactivity levels, significant decreases in daytime sleep, and significant increases in time swimming in the forced swim test. In terms of sexual behavior, the MSN mice showed significantly higher number of mounts and a trend toward higher time mounting. In separate studies, olanzapine and lithium (or respective controls) were administered to MSN mice for at least 2weeks and response to treatments was evaluated. Olanzapine (1mg/kg/day) significantly decreased in-cage hyperactivity and significantly increased time sleeping. Lithium (0.2-0.4% in food) significantly decreased in-cage hyperactivity. Given the behavioral phenotypes and the response to anti-BPD treatments, we propose that MSN mice may provide a possible new model for understanding the neural and genetic basis of phenotypes related to mania and for developing pharmaceutical treatments.

Striatal dopamine transporter availability in unmedicated bipolar disorder

OBJECTIVES

Dopamine transmission abnormalities have been implicated in the etiology of bipolar disorder (BPD). However, there is a paucity of receptor imaging studies in BPD, and little information is available about the dopamine system in BPD. Reuptake of synaptic dopamine by the dopamine transporter (DAT) is the principal mechanism regulating dopamine neurotransmission, and is often used as a marker for presynaptic dopamine function. This positron emission tomography (PET) study investigated whether DAT availability differed between BPD and healthy control subjects.

METHODS

A total of 11 unmedicated BPD patients in either the euthymic or depressed phase and 13 closely matched healthy subjects underwent PET imaging with the DAT-selective radiotracer [(11) C]CFT and a structural magnetic resonance imaging (MRI) scan. Striatal binding potential (BP(ND) ) was estimated using the multilinear reference tissue model. Region of interest and analyses were conducted to test for differences in [(11) C]CFT BP(ND) between groups.

RESULTS

Unmedicated BPD subjects had significantly lower DAT availability relative to healthy controls in bilateral dorsal caudate.

CONCLUSIONS

The results of this study support the hypothesis that there are abnormalities in the dopaminergic system in BPD, and suggest that DAT availability may be related to the neuropathology of BPD. Future studies are needed to determine if DAT availability cycles with disease phase.

The NMDA receptor/nitric oxide pathway: a target for the therapeutic and toxic effects of lithium

Although lithium has largely met its initial promise as the first drug discovered in the modern era of psychopharmacology, to date no definitive mechanism for its effects has been established. It has been proposed that lithium exerts its therapeutic effects by interfering with signal transduction through G-protein-coupled receptor (GPCR) pathways or direct inhibition of specific targets in signaling systems, including inositol monophosphatase and glycogen synthase kinase-3 (GSK-3). Recently, increasing evidence has suggested that N-methyl-D-aspartate receptor (NMDAR)/nitric oxide (NO) signaling could mediate some lithium-induced responses in the brain and peripheral tissues. However, the probable role of the NMDAR/NO system in the action of lithium has not been fully elucidated. In this review, we discuss biochemical, preclinical/behavioral and physiological evidence that implicates NMDAR/NO signaling in the therapeutic effect of lithium. NMDAR/NO signaling could also explain some of side effects of lithium.

A manic episode in a 64-year-old man: an adverse effect of varenicline

Varenicline is a novel treatment for smoking cessation. However, it has not been well studied in patients with medical and psychiatric comorbidity. We report a case of an acute manic episode in a 64-year-old man with a history of bipolar disorder post stroke, who was started on varenicline. This case demonstrates the importance of monitoring neuropsychiatric adverse drug reactions after the start of varenicline therapy in patients with a current or past history of mental illness.

Peripheral biomarkers and illness activity in bipolar disorder

Recent evidence suggests that peripheral markers related to oxidative stress, inflammation and neurotrophins may be altered during mood episodes in bipolar disorder. These can be seen as proxies of peripheral toxicity or markers of illness activity. Here we report an en bloc assessment of a set of previously described biomarkers in different mood states (n = 60) as well as in healthy subjects (n = 80). To make the point that these are ominous changes, we obtained the same measures from a group of septic patients (n = 15) as a "positive" control group. In this sample, we measured serum levels of brain derived neurotrophic factor, neurotrophin 3, tumor necrosis factor α, interleukin 6, interleukin 10, total reactive antioxidant potential, thiobarbituric acid reactive substances and protein carbonyl content. Several of the markers discriminated between the bipolar and control groups, especially when patients were in acute episodes. In some cases, toxicity was as high in bipolar disorder as that seen in patients with sepsis. We believe these findings highlight the potential of using biomarkers to assess illness activity in bipolar disorder.

Paced finger-tapping abnormalities in bipolar disorder indicate timing dysfunction

OBJECTIVES

Theoretical and empirical evidence suggests that impaired time perception and the neural circuitry contributing to internal timing mechanisms may contribute to severe psychiatric disorders, including mood disorders. The structures that are involved in subsecond timing, i.e., cerebellum and basal ganglia, have also been implicated in the pathophysiology of bipolar disorder. However, the timing of subsecond intervals has infrequently been studied in this population.

METHODS

Paced finger-tapping tasks have been used to characterize internal timing processes in neuropsychiatric disorders. A total of 42 bipolar disorder patients (25 euthymic, 17 manic) and 42 age-matched healthy controls completed a finger-tapping task in which they tapped in time with a paced (500-ms intertap interval) auditory stimulus (synchronization), then continued tapping without auditory input while attempting to maintain the same pace (continuation). This procedure was followed using the dominant index finger, then with alternating thumbs.

RESULTS

Bipolar disorder participants showed greater timing variability relative to controls regardless of pacing stimulus (synchronization versus continuation) or condition (dominant index finger versus alternating thumbs). Decomposition of timing variance into internal clock versus motor implementation components using the Wing-Kristofferson model showed higher clock variability in the bipolar disorder groups compared to controls, with no differences between groups on motor implementation variability.

CONCLUSIONS

These findings suggest that internal timing mechanisms are disrupted in bipolar disorder patients, independent of symptom status. Increased clock variability in bipolar disorder may be related to abnormalities in cerebellar function.

Oestradiol and psychosis: clinical findings and biological mechanisms

Female sex steroids easily access the central nervous system and modulate a number of intracerebral processes via their specific receptors. Oestradiol is the biologically dominant female sex steroid and has been implicated in the aetiology and course of psychotic illnesses. There is evidence for interaction between oestradiol and several neurobiological systems that have been implicated in the pathogenesis of psychotic illnesses. Clinical studies have indicated that psychosis, and in particular schizophrenia, is associated with reduced ovarian function and that this may be inherent to the illness itself. In schizophrenia several studies have suggested a therapeutic effect of oestradiol and selective oestrogen modulators although research is still at an early stage. In bipolar disorder, the relationship between childbirth and first onsets or recurrences is one of the most reproducible findings in psychiatric research. Whether or not the rapid fall of oestrogens is the mediating mechanism is not yet clear but preliminary oestrogen treatment studies commenced immediately after childbirth are promising. Outside the perinatal context, tamoxifen, a selective oestrogen receptor modulator, has shown strong antimanic effects although further studies are necessary to test an effect in larger samples. Hormonal treatments should not yet be used in standard care but could be considered in women with treatment resistant psychoses.

Tyrosine hydroxylase and regulation of dopamine synthesis

Tyrosine hydroxylase is the rate-limiting enzyme of catecholamine biosynthesis; it uses tetrahydrobiopterin and molecular oxygen to convert tyrosine to DOPA. Its amino terminal 150 amino acids comprise a domain whose structure is involved in regulating the enzyme's activity. Modes of regulation include phosphorylation by multiple kinases at four different serine residues, and dephosphorylation by two phosphatases. The enzyme is inhibited in feedback fashion by the catecholamine neurotransmitters. Dopamine binds to TyrH competitively with tetrahydrobiopterin, and interacts with the R domain. TyrH activity is modulated by protein-protein interactions with enzymes in the same pathway or the tetrahydrobiopterin pathway, structural proteins considered to be chaperones that mediate the neuron's oxidative state, and the protein that transfers dopamine into secretory vesicles. TyrH is modified in the presence of NO, resulting in nitration of tyrosine residues and the glutathionylation of cysteine residues.

Is glycogen synthase kinase-3 a central modulator in mood regulation?

Little is known regarding the mechanisms underlying the complex etiology of mood disorders, represented mainly by major depressive disorder and bipolar disorder. The 1996 discovery that lithium inhibits glycogen synthase kinase-3 (GSK3) raised the possibility that impaired inhibition of GSK3 is associated with mood disorders. This is now supported by evidence from animal biochemical, pharmacological, molecular, and behavioral studies and from human post-mortem brain, peripheral tissue, and genetic studies that are reviewed here. Mood disorders may result in part from impairments in mechanisms controlling the activity of GSK3 or GSK3-regulated functions, and disruptions of these regulating systems at different signaling sites may contribute to the heterogeneity of mood disorders. This substantial evidence supports the conclusion that bolstering the inhibitory control of GSK3 is an important component of the therapeutic actions of drugs used to treat mood disorders and that GSK3 is a valid target for developing new therapeutic interventions.

Dopamine and oxytocin interactions underlying behaviors: potential contributions to behavioral disorders

Dopamine is an important neuromodulator that exerts widespread effects on the central nervous system (CNS) function. Disruption in dopaminergic neurotransmission can have profound effects on mood and behavior and as such is known to be implicated in various neuropsychiatric behavioral disorders including autism and depression. The subsequent effects on other neurocircuitries due to dysregulated dopamine function have yet to be fully explored. Due to the marked social deficits observed in psychiatric patients, the neuropeptide, oxytocin is emerging as one particular neural substrate that may be influenced by the altered dopamine levels subserving neuropathologic-related behavioral diseases. Oxytocin has a substantial role in social attachment, affiliation and sexual behavior. More recently, it has emerged that disturbances in peripheral and central oxytocin levels have been detected in some patients with dopamine-dependent disorders. Thus, oxytocin is proposed to be a key neural substrate that interacts with central dopamine systems. In addition to psychosocial improvement, oxytocin has recently been implicated in mediating mesolimbic dopamine pathways during drug addiction and withdrawal. This bi-directional role of dopamine has also been implicated during some components of sexual behavior. This review will discuss evidence for the existence dopamine/oxytocin positive interaction in social behavioral paradigms and associated disorders such as sexual dysfunction, autism, addiction, anorexia/bulimia, and depression. Preliminary findings suggest that whilst further rigorous testing has to be conducted to establish a dopamine/oxytocin link in human disorders, animal models seem to indicate the existence of broad and integrated brain circuits where dopamine and oxytocin interactions at least in part mediate socio-affiliative behaviors. A profound disruption to these pathways is likely to underpin associated behavioral disorders. Central oxytocin pathways may serve as a potential therapeutic target to improve mood and socio-affiliative behaviors in patients with profound social deficits and/or drug addiction.

Activation of Akt signaling in rat brain by intracerebroventricular injection of ouabain: a rat model for mania

Intracerebroventricular (ICV) injection of ouabain, a specific Na-K ATPase inhibitor, induces behavioral changes in rats resembling the manic phenotypes of bipolar disorder. The binding of ouabain to the Na-K ATPase affects signal events in vitro including Akt, a possible molecular target of mood disorders. However, the effects of ouabain on Akt in the brain need further clarification. In this study, we investigated changes in the phosphorylation state of Akt in the rat brain after ICV injection of ouabain. Consistent with our previous report, the locomotor activity of rats within 30 min after ouabain ICV injection changed according to the dose with higher doses of ouabain, 0.5 and 1 mM, inducing significant hyperactivity. In addition, ouabain administration induced a dose-dependent increase in the immunoreactivity of p-Akt (Ser473) in the frontal cortex, striatum, and hippocampus after 30 min, and reached statistical significance with 1mM of ouabain. Phosphorylation of GSK-3beta (Ser9), FOXO1 (Ser256), and eNOS (Ser1177), which are downstream molecules of Akt, was also increased in a dose-dependent manner within the same brain regions. Moreover, hyperactivity was seen for 8h after a single 1mM injection of ouabain and increased phosphorylation of Akt (Ser473), GSK-3beta (Ser9), FOXO1 (Ser256), and eNOS (Ser1177) was also observed in the cortex, striatum, and hippocampus. Thus, intrabrain injection of ouabain induces activation of Akt signaling accompanied by hyperactivity, suggesting the possible role of Akt in ouabain rat model of mania.

Circadian rhythms and sleep in bipolar disorder

OBJECTIVE

Biological rhythm pathways are highlighted in a number of etiological models of bipolar disorder, and the management of circadian instability appears in consensus treatment guidelines. There are, however, significant conceptual and empirical limitations on our understanding of a hypothesised link between circadian, sleep, and emotion regulation processes in bipolar disorder. The aim of this article is to articulate the limits of scientific knowledge in relation to this hypothesis.

METHODS

A critical evaluation of various literatures was undertaken. The basic science of circadian and sleep processes, their involvement in normal emotion regulation, and the types of evidence suggesting circadian/sleep involvement in bipolar disorder are reviewed.

RESULTS

Multiple lines of evidence suggest that circadian and sleep-wake processes are causally involved in bipolar disorder. These processes demonstrably interact with other neurobiological pathways known to be important in bipolar disorder, but are unique in that they are open to behavioural manipulation.

CONCLUSION

Further research into biological rhythm pathways to bipolar disorder is warranted. Person-environment feedback loops are fundamental to circadian adaptation, and models of circadian pathogenesis (and treatment) should recognize this complexity.

The clinical significance of creativity in bipolar disorder

Clinical implications of the high rates of creativity within bipolar disorder (BD) have not been explored. The aim of this review is to outline these implications by (i) reviewing evidence for the link between creativity and BD, (ii) developing a provisional model of mechanisms underpinning the creativity-BD link, (iii) describing unique challenges faced by creative-BD populations, and (iv) systematically considering evidence-based psychosocial treatments in the light of this review. While more research into the creativity-BD nexus is urgently required, treatment outcomes will benefit from consideration of this commonly occurring phenotype.