Intracellular calcium signaling systems in the pathophysiology of affective disorders

A Systematic Review of the Clinical Use of Gabapentin and Pregabalin in Bipolar Disorder

Despite its prevalence and disease burden, several chasms still exist with regard to the pharmacotherapy of bipolar disorder (BD). Polypharmacy is commonly encountered as a significant proportion of patients remain symptomatic, and the management of the depressive phase of the illness is a particular challenge. Gabapentin and pregabalin have often been prescribed off-label in spite of a paucity of evidence and clinical practice guidelines to support its use. This systematic review aimed to synthesize the available human clinical trials and inform evidence-based pharmacological approaches to BD management. A total of six randomized, controlled trials (RCTs) and 13 open-label trials involving the use of gabapentin and pregabalin in BD patients were reviewed. Overall, the studies show that gabapentin and its related drug pregabalin do not have significant clinical efficacy as either monotherapy or adjunctive therapy for BD. Gabapentin and pregabalin are probably ineffective for acute mania based on the findings of RCT, with only small open-label trials to support its potential adjunctive role. However, its effects on the long-term outcomes of BD remain to be elucidated. The evidence base was significantly limited by the generally small sample sizes and the trials also had heterogeneous designs and generally high risk of bias.

Biological rationale and potential clinical use of gabapentin and pregabalin in bipolar disorder, insomnia and anxiety: protocol for a systematic review and meta-analysis

INTRODUCTION

Gabapentin has been extensively prescribed off-label for psychiatric indications, with little established evidence of efficacy. Gabapentin and pregabalin, a very similar drug with the same mechanism of action, bind to a subunit of voltage-dependent calcium channels which are implicated in the aetiopathogenesis of bipolar disorder, anxiety and insomnia. This systematic review and meta-analysis aims to collect and critically appraise all the available evidence about the efficacy and tolerability of gabapentin and pregabalin in the treatment of bipolar disorder, insomnia and anxiety.

METHODS AND ANALYSIS

We will include all randomised controlled trials (RCTs) reported as double-blind and comparing gabapentin or pregabalin with placebo or any other active pharmacological treatment (any preparation, dose, frequency, route of delivery or setting) in patients with bipolar disorder, anxiety or insomnia. For consideration of adverse effects (tolerability), single-blind or open-label RCTs and non-randomised evidence will also be summarised. The main outcomes will be efficacy (measured as dichotomous and continuous outcome) and acceptability (proportion of patients who dropped out of the allocated treatment). Published and unpublished studies will be sought through relevant database searches, trial registries and websites; all reference selection and data extraction will be conducted by at least 2 independent reviewers. We will conduct a random-effects meta-analysis to synthesise all evidence for each outcome. Heterogeneity between studies will be investigated by the I² statistic. Data from included studies will be entered into a funnel plot for investigation of small-study effects. No subgroup analysis will be undertaken, but we will carry out sensitivity analyses about combination treatment, psychiatric comorbidity, use of rescue medications and fixed versus random-effects model.

ETHICS AND DISSEMINATION

This review does not require ethical approval. This protocol has been registered on PROSPERO (CRD42016041802). The results of the systematic review will be disseminated via publication in a peer-reviewed journal.

Enhanced calcium responses to serotonin receptor stimulation in T-lymphocytes from schizophrenic patients--a pilot study

Even if more extensively investigated in affective disorders, the serotonergic system is likely to be also implicated in modulating the pathogenesis of schizophrenia, where it closely interacts with the dopaminergic and glutamatergic system. To substantiate this notion, we studied the intensity and dynamics of cellular Ca(2+) responses to serotonin (5-hydoxytryptamine, 5-HT) in peripheral lymphocytes taken from currently non-psychotic schizophrenic patients. To this aim, peripheral lymphocytes were freshly obtained from healthy controls and a naturalistic collective of patients with schizophrenia in remission. Intracellular Ca(2+) responses were recorded in real-time by ratiometric fluorometry after 5-HT or phythaemagglutinin (PHA) stimulation, which served as an internal reference for Ca(2+) responsivity to non-specific stimulation. The intracellular Ca(2+) peak early after applying the 5-HT trigger was significantly elevated in schizophrenic patients. No significant differences of Ca(2+) peak levels were seen in response to stimulation with the mitogenic agent PHA, although responses to 5-HT and PHA were positively correlated in individual patients or controls. In conclusion, the serotonergic response patterns in peripheral lymphocytes from schizophrenic patients seem to be elevated, if employing sensitive tools like determination of intracellular Ca(2+) responses. Our observations suggest that the participation of serotonergic neurotransmitter system in the pathogenesis of schizophrenia may deserve more interest, even if it should only act as a modulator on the main pathology in the dopaminergic and glutamatergic systems. We hope that this pilot study will prompt further studies with larger patient collectives to revisit this question.

Essential elements in depression and anxiety. Part I

Essential elements are very important for the proper functioning of the human body. They are required for fundamental life processes such as cell division and differentiation and protein synthesis. Thus a deficiency of these essential elements is associated with an enormous health risk that can ultimately lead to death. In recent years, studies have provided valuable information on the involvement of essential elements in psychiatric disorders, in particular depression and anxiety. There is strong evidence indicating that deficiency of essential elements can lead to the development of depressive and/or anxiogenic behaviour and supplementation can enhance therapeutic effect of antidepressants and anxiolytics. This review presents the most important results from preclinical and clinical studies showing involvement of essential elements such as zinc, magnesium, lithium, iron, calcium and chromium in depression and anxiety. From these studies it is evident that different types of depression and anxiety respond to treatment at different receptors indicating that the underlying mechanisms are slightly different. Furthermore, administration of low dose antidepressants supplemented with an element is effective and can reduce unwanted side effects in different types of depression/anxiety.

Emerging synergisms between drugs and physiologically-patterned weak magnetic fields: implications for neuropharmacology and the human population in the twenty-first century

Synergisms between pharmacological agents and endogenous neurotransmitters are familiar and frequent. The present review describes the experimental evidence for interactions between neuropharmacological compounds and the classes of weak magnetic fields that might be encountered in our daily environments. Whereas drugs mediate their effects through specific spatial (molecular) structures, magnetic fields mediate their effects through specific temporal patterns. Very weak (microT range) physiologically-patterned magnetic fields synergistically interact with drugs to strongly potentiate effects that have classically involved opiate, cholinergic, dopaminergic, serotonergic, and nitric oxide pathways. The combinations of the appropriately patterned magnetic fields and specific drugs can evoke changes that are several times larger than those evoked by the drugs alone. These novel synergisms provide a challenge for a future within an electromagnetic, technological world. They may also reveal fundamental, common physical mechanisms by which magnetic fields and chemical reactions affect the organism from the level of fundamental particles to the entire living system.

Mitochondrial DNA haplogroup analysis in patients with bipolar disorder

Several lines of evidence support mitochondrial dysfunction in bipolar disorder. Elevated calcium level in platelets is reported in this disease. To verify mitochondrial DNA (mtDNA) haplogroups characteristic to bipolar disorder, we sequenced mtDNA of seven regions and performed haplogroup analysis in 195 patients with bipolar disorder and 255 controls. They belonged to 16 major mtDNA haplogroups, A, B4, B5, C, D4, D5, F, G, M7, M8, M9, M10-12, N9a, N9b, Y, and Z. The logistic regression analysis revealed that the haplogroup N9a was over-represented in bipolar disorder. We also performed a case-control study for two functional mtDNA polymorphisms, mtDNA5460G > A and 12358A > G, that altered intracellular calcium dynamics. While the mtDNA5460G > A polymorphism was not associated with bipolar disorder, the mtDNA12358A > G polymorphism was associated with bipolar disorder in 199 patients with bipolar disorder and 260 controls. However, this association was not replicated in an independent sample set. Possible significances of these findings are discussed.

Role of mitochondrial DNA in calcium signaling abnormality in bipolar disorder

Altered intracellular calcium levels are a consistent finding in studies of bipolar disorder, and recent studies point to the role of mitochondrial dysfunction, leading to the possibility that mitochondrial calcium dysregulation is involved in the pathophysiology of the disease. Although the mitochondrion is a key organelle for calcium accumulation, initial calcium signaling studies in bipolar disorder did not focus on the role of mitochondria. Later, neuroimaging and molecular genetic studies suggested the possibility that altered mitochondrial calcium regulation due to mitochondrial DNA (mtDNA) polymorphisms/mutations might be involved in the pathophysiology of bipolar disorder. Recent studies show that certain mtDNA polymorphisms alter mitochondrial calcium levels. Mutant mtDNA polymerase (Polg) transgenic mice carrying mtDNA mutations in forebrain cells show an increased calcium uptake rate in isolated mitochondria. This was found to be mediated by downregulation of cyclophilin D, a component of the mitochondrial permeability transition pore. In addition, agonist-stimulated calcium response is attenuated in hippocampal neurons of these transgenic mice. The finding that mtDNA polymorphisms and mutations affect mitochondrial calcium regulation supports the idea that mitochondrial calcium dysregulation may be involved in the pathophysiology of bipolar disorder. In this review, the history and recent findings of studies elucidating the role of mitochondrial calcium signaling in bipolar disorder are summarized.

Comprehensive gene expression analysis in bipolar disorder

OBJECTIVE

To review recent findings by DNA microarray in bipolar disorder (BD).

METHOD

A literature search was performed.

RESULTS

Comprehensive gene expression analysis in the brain, peripheral blood cells, and olfactory neuroepithelium would be a promising strategy for the research of BD. To date, alterations in glutamate receptors (GR), mitochondria-related genes, chaperone genes, oligodendrocyte genes, and markers of gamma amino butyric acidergic (GABAergic) neurons in postmortem brains are replicated by several different strategies. However, alterations in mitochondria-related genes are associated with agonal factors, sample pH, and effects of drugs. Analysis of blood cells showed altered endoplasmic reticulum stress pathway and other molecular cascades. Analysis of olfactory epithelium showed altered expression of genes associated with apoptosis.

CONCLUSIONS

These findings warrant that comprehensive gene expression analysis by DNA microarray will be useful to identify the molecular cascades responsible for BD.

Mitochondrial dysfunction as the molecular basis of bipolar disorder: therapeutic implications

Multiple lines of evidence, such as impaired energy metabolism in the brain detected by magnetic resonance spectroscopy, a possible role of maternal inheritance, co-morbidity with mitochondrial diseases, the effects of mood stabilisers on mitochondria, increased mitochondrial DNA (mtDNA) deletion in the brain, and association with mtDNA mutations/polymorphisms or nuclear-encoded mitochondrial genes, suggest that mitochondrial dysfunction is an important component of bipolar disorder. Global reduction of mitochondria-related gene expression in the postmortem brains of patients with bipolar disorder may also be an indicator, but such findings are affected by sample pH and thus need to be interpreted with caution. A recently developed animal model carrying mtDNA deletion in neurons suggested that accumulation of mtDNA deletions causes bipolar disorder-like phenotypes. The next step in the study of mitochondrial dysfunction in bipolar disorder should be clarification of how mitochondrial dysfunction, a nonspecific risk factor, can cause specific symptoms of bipolar disorder. Two hypothetical mechanisms are mtDNA neuroplasticity and nonvisual photoreception impairment. Further study of mitochondrial dysfunction in bipolar disorder is expected to be useful for the development of new mood stabilisers.

Desipramine-induced Ca2+ movement and cytotoxicity in PC3 human prostate cancer cells

The effect of the antidepressant desipramine on intracellular Ca(2+) movement and viability in prostate cancer cells has not been explored previously. The present study examined whether desipramine could alter Ca(2+) handling and viability in human prostate PC3 cancer cells. Cytosolic free Ca(2+) levels ([Ca(2+)](i)) in populations of cells were measured using fura-2 as a probe. Desipramine at concentrations above 10 microM increased [Ca(2+)](i) in a concentration-dependent manner. The responses saturated at 300 microM desipramine. The Ca(2+) signal was reduced by half by removing extracellular Ca(2+), but was unaffected by nifedipine, nicardipine, nimodipine, diltiazem or verapamil. In Ca(2+)-free medium, after treatment with 300 microM desipramine, 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) failed to release Ca(2+) from endoplasmic reticulum. Conversely, desipramine failed to release more Ca(2+) after thapsigargin treatment. Inhibition of phospholipase C with U73122 did not affect desipramine-induced Ca(2+) release. Overnight incubation with 10-800 microM desipramine decreased viability in a concentration-dependent manner. Chelation of cytosolic Ca(2+) with BAPTA did not reverse the decreased cell viability. Collectively, the data suggest that in PC3 cells, desipramine induced a [Ca(2+)](i) increase by causing Ca(2+) release from endoplasmic reticulum in a phospholipase C-independent fashion and by inducing Ca(2+) influx. Desipramine decreased cell viability in a concentration-dependent, Ca(2+)-independent manner.

Animal models of bipolar disorder

Animal models of human diseases should meet three sets of criteria: construct validity, face validity, and predictive validity. To date, several putative animal models of bipolar disorder have been reported. They are classified into various categories: pharmacological models, nutritional models, environmental models, and genetic models. None of them, however, totally fulfills the three validity criteria, and thus may not be useful for drug development. Mounting evidence suggests that mitochondrial dysfunction has a role in bipolar disorder. To test whether accumulation of mtDNA deletions in the brain can cause bipolar disorder, we generated transgenic mice with neuron-specific expression of mutant Polg (D181A). These mice showed altered diurnal activity rhythm and periodic activity change associated with the estrous cycle. These phenotypes were worsened by administration of a tricyclic antidepressant, but improved after lithium treatment. This mouse model of bipolar disorder potentially fulfills the three validity criteria, and therefore might be used for future drug development studies.

Abnormal Ca2+ dynamics in transgenic mice with neuron-specific mitochondrial DNA defects

Maintenance of mitochondrial DNA (mtDNA) depends on nuclear-encoded proteins such as mtDNA polymerase (POLG), whose mutations are involved in the diseases caused by mtDNA defects including mutation and deletion. The defects in mtDNA and in intracellular Ca2+ ([Ca2+]i) homeostasis have been reported in bipolar disorder (BD). To understand the relevance of the mtDNA defects to BD, we studied transgenic (Tg) mice in which mutant POLG (mutPOLG) was expressed specifically in neurons. mtDNA defects were accumulated in the brains of mutPOLG Tg mice in an age-dependent manner and the mutant mice showed BD-like behavior. However, the molecular and cellular basis for the abnormalities has not been clarified. In this study, we investigated Ca2+ regulation by isolated mitochondria and [Ca2+]i dynamics in the neurons of mutPOLG Tg mice. Mitochondria from the mutant mice sequestered Ca2+ more rapidly, whereas Ca2+ retention capacity and membrane potential, a driving force of Ca2+ uptake, of mitochondria were unaffected. To elucidate the molecular mechanism of the altered Ca2+ uptake, we performed DNA microarray analysis and found that the expression of cyclophilin D (CyP-D), a component of the permeability transition pore, was downregulated in the brains of mutPOLG Tg mice. Cyclosporin A, an inhibitor of CyP-D, mimicked the enhanced Ca2+ uptake in mutant mice. Furthermore, G-protein-coupled receptor-mediated [Ca2+]i increase was attenuated in hippocampal neurons of the mutant mice. These findings suggest that mtDNA defects lead to enhancement of Ca2+ uptake rate via CyP-D downregulation and alter [Ca2+]i dynamics, which may be involved in the pathogenesis of BD.

Blockade of intracellular calcium release induces an antidepressant-like effect in the mouse forced swimming test

The role of intracellular calcium in the modulation of a depressant-like condition was investigated in the mouse forced swimming test. I.c.v. administration of TMB-8 (0.23-46.3 nmol per mouse), a blocker of Ca2+ release from intracellular stores, decreased the mouse immobility time. I.c.v. injection of thapsigargin (0.003-3 nmol per mouse), compound which selectively inhibits Ca2+ uptake into the endoplasmic reticulum, produced, 60 min after administration, a depressant-like condition. Xestospongin C (1-100 pmol per mouse i.c.v.), an InsP3-receptor antagonist, decreased the mouse immobility time. By contrast, d-myo-inositol (5.4-540 pmol per mouse i.c.v.), compound which produces InsP3, resulted in a depressant-like effect. Similarly, ryanodine (0.1-600 pmol per mouse i.c.v.), an RyR antagonist, decreased the immobility time values whereas the administration of 4-chloro-m-cresol (0.1-100 pmol per mouse i.c.v.), an RyR agonist, showed an opposite effect. The antidepressant-like effects observed with TMB-8, xestospongin C and ryanodine were comparable to that produced by the antidepressant drugs amitriptyline and clomipramine. The treatments employed did not produce any behavioural impairment of mice as revealed by the rota-rod and hole board tests indicating that the antidepressant- and depressant-like effects were not due to a compromised locomotor activity and spontaneous motility of the treated animals. These results indicate that a central variation in intracellular calcium contents is involved in the modulation of a depressive-like condition in the mouse forced swimming test. In particular, the blockade of both InsP3Rs and RyRs appears to play an important role in the induction of an antidepressant-like effect, whereas the stimulation of these receptors is involved in a depressant-like response of mice.

Mitochondrial dysfunction in bipolar disorder: evidence from magnetic resonance spectroscopy research

Magnetic resonance spectroscopy (MRS) affords a noninvasive window on in vivo brain chemistry and, as such, provides a unique opportunity to gain insight into the biochemical pathology of bipolar disorder. Studies utilizing proton ((1)H) MRS have identified changes in cerebral concentrations of N-acetyl aspartate, glutamate/glutamine, choline-containing compounds, myo-inositol, and lactate in bipolar subjects compared to normal controls, while studies using phosphorus ((31)P) MRS have examined additional alterations in levels of phosphocreatine, phosphomonoesters, and intracellular pH. We hypothesize that the majority of MRS findings in bipolar subjects can be fit into a more cohesive bioenergetic and neurochemical model of bipolar illness that is both novel and yet in concordance with findings from complementary methodological approaches. In this review, we propose a hypothesis of mitochondrial dysfunction in bipolar disorder that involves impaired oxidative phosphorylation, a resultant shift toward glycolytic energy production, a decrease in total energy production and/or substrate availability, and altered phospholipid metabolism.

The effects of desmethylimipramine on cyclic AMP-stimulated gene transcription in a model cell system

The present study utilised an in vitro cell model of the cAMP signalling pathway to investigate the actions of desipramine (DMI) and other psychoactive agents on cAMP-driven gene transcription. The model comprised CHObeta2 SPAP cells; Chinese hamster ovary cells expressing human beta2 adrenoceptors and a secreted placental alkaline phosphatase (SPAP) reporter gene with multiple cAMP response elements (CREs) in its promoter region. SPAP assays showed DMI to inhibit isoprenaline or forskolin-enhanced gene transcription in a time and concentration-dependent manner (IC50=16.6+/-2.0 microM after 18 h). This effect of DMI was not dependent upon activity at the levels of the beta2 receptor, cAMP accumulation or phosphorylation of the transcription factor, cAMP response element binding protein (CREB). The inhibitory effects were maintained in the presence of DMI for at least 3 weeks and were mimicked by exposure to norfluoxetine (the major metabolite of fluoxetine; IC50=7.2+/-1.8 microM) and the neuroleptics, chlorpromazine and clozapine, all at a concentration of 10 microM. Amphetamine (10 microM, 18 h) enhanced SPAP gene transcription. Ca2+ imaging experiments ruled out an inhibitory effect of DMI on Ca2+ influx as concluded by previous studies. The results suggest a molecular target for DMI that lies downstream of CREB phosphorylation. Whether the inhibitory action of DMI is common to naturally expressed CRE-driven genes involved in adaptive responses to antidepressants in vivo remains to be determined.

Characterization of human and mouse TRPM2 genes: Identification of a novel N-terminal truncated protein specifically expressed in human striatum

Transient receptor potential melastatin 2 (TRPM2) is a calcium-permeable cation channel activated by ADP-ribose or reactive oxygen species. In human, a major transcript of 6.5 kb is expressed in various tissues, whereas a minor transcript of 5.5 kb is detected only in striatum (caudate nucleus and putamen). We found that the 5.5-kb shorter transcript is transcribed from the intron 4 of the TRPM2 gene and encodes the striatum short form protein (SSF-TRPM2) with 1289 amino acid residues as compared to the long form protein (LF-TRPM2), in which the N-terminal 214 amino acid residues are removed. The SSF-TRPM2 protein still maintained H2(O2)-induced Ca2+ influx activity. In addition, we found that the major transcripts in human and mouse start from a novel 5' non-coding exon; however, we could not detect any striatum short transcript in mouse brain. These new findings are invaluable to further study the regulation of TRPM2 gene expression and to examine the possible involvement of the TRPM2 gene in the pathophysiology of bipolar disorder.

Neurobiological findings in bipolar II disorder compared with findings in bipolar I disorder

OBJECTIVE

To determine whether there are consistent neurobiological differences between patients with bipolar I disorder (BD I) and those with bipolar II disorder (BD II).

METHOD

We reviewed the literature in areas where the most consistent neurobiological findings have been reported for bipolar disorder, specifically, neuroimaging and brain metabolism. The imaging studies reviewed examined structure, using magnetic resonance imaging (MRI), and function, using functional MRI, positron emission tomography, and single photon emission computed tomography. We used magnetic resonance spectroscopy to examine brain chemistry. We reviewed those metabolic studies that examined cell calcium, 3-methoxy-4-hydroxyphenylglycol, and protein kinase C.

RESULTS

Some genetic studies suggest that there may be differences between BD II and BD I patients. However, our review of the imaging and metabolic studies identified few studies directly comparing these 2 groups. In those studies, there were few differences, if any, and these were not consistent.

CONCLUSIONS

While genetic data suggest there may be differences between BD II patients and BD I patients, the neurobiological findings to date do not provide support. However, this may be owing to the small number of studies directly comparing the 2 groups and also to the fact that those carried out have not been adequately powered to detect possible small true differences. This is an important issue because, if there are no neurobiological differences, it would be anticipated that similar treatments would be similarly effective in both groups. Given the importance of understanding whether there are neurochemical differences between these groups, further research in this area is clearly needed.

Expression of HSPF1 and LIM in the lymphoblastoid cells derived from patients with bipolar disorder and schizophrenia

We have previously reported the altered expressions of HSPF1 and LIM in the lymphoblastoid cell lines (LCLs) derived from Japanese patients with bipolar disorder (bipolar I disorder). The altered expression at the LCL level would be useful for developing diagnostic markers as well as a cellular model for bipolar disorder. In this study, we extended our previous study by measuring their expressions using the following samples: (1) larger number of LCLs from Japanese subjects, (2) LCLs from Caucasian subjects, and (3) LCLs from patients with bipolar II disorder or schizophrenia. We confirmed the increased expression of HSPF1 (P=0.009) and decreased expression of LIM (P=0.001) in the LCLs from patients with Japanese bipolar I disorder. These altered expressions were also observed in those from patients with Japanese bipolar II disorder (P= 0.002 for HSPF1 and P = 0.072 for LIM). We also found the altered expressions of HSPF1 in LCLs from Caucasian patients with bipolar II disorder (P=0.011) and LIM in those from patients with schizophrenia (P = 0.001).

The neurobiology and control of anxious states

Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.

Biological predictors of lithium response in bipolar disorder

In order to prescribe lithium appropriately to patients with bipolar disorder, predictors of lithium response are helpful. The present paper reviews the biological predictors of lithium response. As a positive predictor of lithium response, the following have been reported: strong loudness dependence of the auditory-evoked N1/P2-response; higher brain lithium concentration; lower inositol monophosphatase (IMPase) mRNA expression; higher serotonin-induced calcium mobilization; increased N-acetyl-aspartate peak and decreased myo-inositol peak; white matter hyperintensity; decreased intracellular pH; higher frequency of phospholipase C gamma-1 (PLCG1)-5 repeat and PLCG1-8 repeat; and C973A polymorphism in the inositol polyphosphate 1-phosphatase gene. In contrast the following have been reported as a predictor of negative lithium response: epileptiform abnormality of electroencephalography; human leukocyte antigen type A3; decreased phosphocreatine peak area after photic stimulation; and homozygotes for the short variant of the serotonin transporter gene. Most of the possible biological predictors of better lithium response, such as lower IMPase mRNA levels, white matter hyperintensity, lower brain intracellular pH, enhanced calcium response, and PLCG1-5 repeat had been detected as risk factors for bipolar disorder, suggesting that bipolar disorder responding well to maintenance lithium treatment is a distinct category having a certain neurobiological basis, although these findings need further replication. The search for biological predictors of lithium response is still in its infancy. Most of the laboratory or neuroimaging techniques used in these studies are not easily performed in clinical settings, so the development of an easy and useful laboratory test is needed.

Changes in CREB-phosphorylation during recovery from major depression

For decades psychiatrists have been looking for biological state markers measurable by easy blood test in order to follow up and predict early on treatment response in patients with major depression. In the present study we investigated whether or not measuring CREB (cAMP-response-element-binding-protein) phosphorylation in peripheral blood T lymphocytes is a state marker of treatment response. CREB is an ubiquitous key-element of intracellular signal transduction cascades and its transcriptional activity depends on phosphorylation at Ser-133. Several studies in animals demonstrated that the transcriptional activity of CREB is up-regulated by antidepressant treatment. Therefore, it has been hypothesized that antidepressant treatment exerts its therapeutic effect by this mechanism. In the present study, we investigated CREB-phosphorylation in T-lymphocytes of 20 patients before and in the end of week one and two of either psychopharmacological or psychotherapeutic treatment. After two weeks, 15 patients fulfilled the criteria of treatment response (i.e. 30% reduction in HAMD score compared to baseline), whereas five patients did not. In the end of week two, the responders showed a significant increase in CREB-phosphorylation (P = 0.018) compared to the non-responders. This was true for all patients with either treatment regimen. In conclusion, these results indicate for the first time that the increase in CREB-phosphorylation might be a molecular state marker for the response to antidepressant treatment.

Modulation of serotonin2A receptor function in rats after repeated treatment with dexamethasone and L-type calcium channel antagonist nimodipine

1. It has been conceivable that the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity plays an important role in the pathophysiology of depression. In the present study, we have investigated the effect of repeated treatment with dexamethasone on serotonin (5-HT) 1A, 5-HT2A and alpha1-adrenergic receptors in the rat frontal cortex. Moreover, several studies have suggested the effectiveness of L-type calcium channel antagonist nimodipine for the treatment of depression. We also investigated the effect of repeated treatment with nimodipine on 5-HT2A receptor in rats with repeated dexamethasone treatment. 2. Repeated treatment with dexamethasone (1 mg/kg/day for 14 days) increased the density of 5-HT2A receptor, but not 5-HT1A and alpha1-adrenergic receptors in the rat frontal cortex. 3. The density of 5-HT2A receptor in the rat frontal cortex was significantly increased 1 day after repeated treatment with dexamethasone, but was not increased 7 or 14 days after repeated treatment. Wet dog shakes (WDS) induced by (+/-)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI), a 5-HT2A receptor agonist, in rats were significantly enhanced 1, 7 and 14 days after repeated treatment with dexamethasone, although the frequency of WDS gradually decreased after repeated treatment. 4. Repeated treatment with nimodipine (5 mg/kg/day for 14 days) attenuated DOI-induced WDS enhanced by repeated treatment with dexamethasone (1 mg/kg/day for 14 days), however, it did not change the density of 5-HT2A receptor. Repeated treatment with dexamethasone decreased locomotor activity and body weight, but repeated treatment with nimodipine did not recover these parameters. 5. The results of the present study suggest that repeated treatment with dexamethasone may selectively increase the 5-HT2A receptor in the rat frontal cortex and affect 5-HT2A receptor-mediated signal transduction. In addition, the intracellular calcium homeostasis by blocking calcium influx through L-type calcium channel may play an important role in the regulation of the 5-HT2A receptor function by dexamethasone.

Molecular genetics of bipolar disorder

Alteration of monoaminergic neurotransmission is implicated in the pathophysiology of bipolar disorder (manic-depressive illness). Candidate genes participating in monoaminergic neurotransmission, especially serotonin transporter and monoamine oxidase A, may be associated with bipolar disorder. And the regulating regions of these genes and the molecules participating in intracellular signal transduction are now under investigation. To date, 13 whole genome positional cloning studies have been performed and many candidate loci identified. Using patients from a pedigree in which schizophrenia, depression or bipolar disorder have been linked with a balanced translocation at 1 and 11, candidate pathogenetic genes were cloned as DISC1 (disrupted in schizophrenia-1) and DISC2. Recently, pathogenetic mutations have been identified in two genetic diseases frequently co-morbid with mood disorder; WFS1 for Wolfram syndrome and ATP2A2 (SERCA2) for Darier's disease. Transmission of bipolar disorder may be characterized by anticipation and parent-of-origin effect, and extended CTG repeat at SEF2-1B gene was identified from a bipolar patient. However, its pathogenetic role was not supported by subsequent studies. Association of bipolar disorder with mitochondrial DNA has also been suggested. The role of genomic imprinting is also possible because linkage to 18p11 is limited to paternally transmitted pedigrees. These results warrant further study of molecular genetics of bipolar disorder.

RNA editing of the human serotonin 5-HT(2C) receptor delays agonist-stimulated calcium release

RNA encoding the human 5-HT(2C) receptor undergoes adenosine-to-inosine RNA editing events at five positions in the putative second intracellular loop, with a corresponding reduction in receptor/G-protein coupling. Agonist-stimulated calcium release was examined in NIH-3T3 fibroblasts stably expressing the nonedited human INI (hINI) or the edited hVSV or hVGV variants. We hypothesized that different receptor isoforms would show altered dynamics of agonist-induced calcium release. The three isoforms showed a rightward shift in agonist concentration-response curves for eliciting calcium release (EC(50) values: hINI, 2.2 nM; hVSV, 15 nM; hVGV, 49 nM). Additionally, the hVGV receptor showed a blunted and delayed [Ca(2+)](i) peak compared with the hINI or hVSV receptor isoforms. These distinctions in agonist-induced [Ca(2+)](i) release imply that edited 5-HT(2C) receptors may produce distinct physiological responses within the central nervous system.

Mitochondrial dysfunction in bipolar disorder

Mitochondrial dysfunction is implicated in bipolar disorder based on the following lines of evidence: 1) Abnormal brain energy metabolism measured by 31P-magnetic resonance spectroscopy, that is, decreased intracellular pH, decreased phosphocreatine (PCr), and enhanced response of PCr to photic stimulation. 2) Possible role of maternal inheritance in the transmission of bipolar disorder. 3) Increased levels of the 4977-bp deletion in mitochondrial DNA (mtDNA) in autopsied brains. 4) Comorbidity of affective disorders in certain types of mitochondrial disorders, such as autosomal inherited chronic progressive external ophthalmoplegia and mitochondrial diabetes mellitus with the 3243 mutation. Based on these findings, we searched for mtDNA mutations/ polymorphisms associated with bipolar disorder and found that 5178C and 10398A polymorphisms in mtDNA were risk factors for bipolar disorder. The 5178C genotype was associated with lower brain intracellular pH. mtDNA variations may play a part in the pathophysiology of bipolar disorder through alteration of intracellular calcium signaling systems. The mitochondrial dysfunction hypothesis, which comprehensively accounts for the pathophysiology of bipolar disorder, is proposed.