Elevated platelet intracellular calcium concentration in bipolar depression

Differentially Altered Metabolic Pathways in the Amygdala of Subjects with Schizophrenia, Bipolar Disorder and Major Depressive Disorder

Background and hypothesis

A growing number of studies implicate a key role for metabolic processes in psychiatric disorders. Recent studies suggest that ketogenic diet may be therapeutically effective for subgroups of people with schizophrenia (SCZ), bipolar disorder (BPD) and possibly major depressive disorder (MDD). Despite this promise, there is currently limited information regarding brain energy metabolism pathways across these disorders, limiting our understanding of how brain metabolic pathways are altered and who may benefit from ketogenic diets. We conducted gene expression profiling on the amygdala, a key region involved in in the regulation of mood and appetitive behaviors, to test the hypothesis that amygdala metabolic pathways are differentially altered between these disorders.

Study Design

We used a cohort of subjects diagnosed with SCZ, BPD or MDD, and non-psychiatrically ill control subjects (n=15/group), together with our bioinformatic 3-pod analysis consisting of full transcriptome pathway analysis, targeted pathway analysis, leading-edge gene analysis and iLINCS perturbagen analysis.

Study Results

We identified differential expression of metabolic pathways in each disorder. Subjects with SCZ displayed downregulation of mitochondrial respiration and nucleotide metabolism pathways. In comparison, we observed upregulation of mitochondrial respiration pathways in subjects with MDD, while subjects with BPD displayed enrichment of pathways involved in carbohydrate metabolism. Several pathways associated with brain metabolism including immune system processes and calcium ion transport were also differentially altered between diagnosis groups.

Conclusion

Our findings suggest metabolic pathways are differentially altered in the amygdala in these disorders, which may impact approaches for therapeutic strategies.

Calcium Channel Antagonists for Mood Disorders

PURPOSE

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

METHOD

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

FINDINGS

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

IMPLICATIONS

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

Cellular calcium in bipolar disorder: systematic review and meta-analysis

Calcium signalling has long been implicated in bipolar disorder, especially by reports of altered intracellular calcium ion concentrations ([Ca²⁺]). However, the evidence has not been appraised critically. We carried out a systematic review and meta-analysis of studies of cellular calcium indices in bipolar disorder. 2281 records were identified and 117 screened, of which 32 were eligible and 21 were suitable for meta-analyses. The latter each involved up to 642 patients and 404 control subjects. We found that basal free intracellular [Ca²⁺] is increased in bipolar disorder, both in platelets and in lymphocytes. The effect size is 0.55, with an estimated elevation of 29%. It is observed in medication-free patients. It is present in mania and bipolar depression, but data are equivocal for euthymia. Cells from bipolar disorder individuals also show an enhanced [Ca²⁺] response to stimulation with 5-HT or thrombin, by an estimated 25%, with an effect size of 0.63. In studies which included other diagnoses, intracellular basal [Ca²⁺] was higher in bipolar disorder than in unipolar depression, but not significantly different from schizophrenia. Functional parameters of cellular Ca²⁺ (e.g. calcium transients), and neuronal [Ca²⁺], have been much less investigated, and no firm conclusions can be drawn. In summary, there is a robust, medium effect size elevation of basal and stimulated free intracellular [Ca²⁺] in bipolar disorder. The results suggest altered calcium functioning in the disorder, and encourage further investigations into the underlying mechanisms, and the implications for pathophysiology and therapeutics.

A Role for SERCA Pumps in the Neurobiology of Neuropsychiatric and Neurodegenerative Disorders

Calcium (Ca²⁺) is a fundamental regulator of cell fate and intracellular Ca²⁺ homeostasis is crucial for proper function of the nerve cells. Given the complexity of neurons, a constellation of mechanisms finely tunes the intracellular Ca²⁺ signaling. We are focusing on the sarco/endoplasmic reticulum (SR/ER) calcium (Ca²⁺)-ATPase (SERCA) pump, an integral ER protein. SERCA's well established role is to preserve low cytosolic Ca²⁺ levels ([Ca²⁺]_cyt), by pumping free Ca²⁺ ions into the ER lumen, utilizing ATP hydrolysis. The SERCA pumps are encoded by three distinct genes, SERCA1-3, resulting in 12 known protein isoforms, with tissue-dependent expression patterns. Despite the well-established structure and function of the SERCA pumps, their role in the central nervous system is not clear yet. Interestingly, SERCA-mediated Ca²⁺ dyshomeostasis has been associated with neuropathological conditions, such as bipolar disorder, schizophrenia, Parkinson's disease and Alzheimer's disease. We summarize here current evidence suggesting a role for SERCA in the neurobiology of neuropsychiatric and neurodegenerative disorders, thus highlighting the importance of this pump in brain physiology and pathophysiology.

Review of animal models of bipolar disorder that alter ion regulation

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Applications of calcium channel blockers in psychiatry: pharmacokinetic and pharmacodynamic aspects of treatment of bipolar disorder

Introduction: Calcium channel blockers (CCBs) comprise a heterogeneous group of medications that reduce calcium influx and attenuate cellular hyperactivity. Evidence of hyperactive intracellular calcium ion signaling in multiple peripheral cells of patients with bipolar disorder, calcium antagonist actions of established mood stabilizers, and a relative dearth of treatments have prompted research into potential uses of CCBs for this common and disabling condition. Areas covered: This review provides a comprehensive overview of intracellular calcium signaling in bipolar disorder, structure and function of calcium channels, pharmacology of CCBs, evidence of efficacy of CCBs in bipolar disorder, clinical applications, and directions for future research. Expert opinion: Despite mixed evidence of efficacy, CCBs are a promising novel approach to a demonstrated cellular abnormality in both poles of bipolar disorder. Potential advantages include low potential for sedation and weight gain, and possible usefulness for pregnant and neurologically impaired patients. Further research should focus on markers of a preferential response, studies in specific bipolar subtypes, development of CCBs acting preferentially in the central nervous system and on calcium channels that are primarily involved in neuronal signaling and plasticity.

Unraveling the biology of bipolar disorder using induced pluripotent stem-derived neurons

OBJECTIVES

Bipolar disorder has been studied from numerous angles, from pathological studies to large-scale genomic studies, overall making moderate gains toward an understanding of the disorder. With the advancement of induced pluripotent stem (iPS) cell technology, in vitro models based on patient samples are now available that inherently incorporate the complex genetic variants that largely are the basis for this disorder. A number of groups are starting to apply iPS technology to the study of bipolar disorder.

METHODS

We selectively reviewed the literature related to understanding bipolar disorder based on using neurons derived from iPS cells.

RESULTS

So far, most work has used the prototypical iPS cells. However, others have been able to transdifferentiate fibroblasts directly to neurons. Others still have utilized olfactory epithelium tissue as a source of neural-like cells that do not need reprogramming. In general, iPS and related cells can be used for studies of disease pathology, drug discovery, or stem cell therapy.

CONCLUSIONS

Published studies have primarily focused on understanding bipolar disorder pathology, but initial work is also being done to use iPS technology for drug discovery. In terms of disease pathology, some evidence is pointing toward a differentiation defect with more ventral cell types being prominent. Additionally, there is evidence for a calcium signaling defect, a finding that builds on the genome-wide association study results. Continued work with iPS cells will certainly help us understand bipolar disorder and provide a way forward for improved treatments.

Levetiracetam, Calcium Antagonism, and Bipolar Disorder

Hyperactive intracellular calcium ion (Ca) signaling in peripheral cells has been a reliable finding in bipolar disorder. Some established mood stabilizing medications, such as lithium and carbamazepine, have been found to normalize elevated intracellular Ca concentrations ([Ca]i) in platelets and lymphocytes from bipolar disorder patients, and some medications the primary effect of which is to attenuate increased [Ca]i have been reported to have mood stabilizing properties.Hyperactive intracellular Ca signaling has also been implicated in epilepsy, and some anticonvulsants have calcium antagonist properties. This study demonstrated that levetiracetam, an anticonvulsant that has been shown to block N and P/Q-type calcium channels in animal studies does not alter elevated [Ca]i in blood platelets of patients with bipolar disorder. Review of published clinical trials revealed no controlled evidence of efficacy as a mood stabilizer.This study underscores the possibility that pharmacologic actions of a medication in animals and normal subjects may not necessarily predict its pharmacologic or clinical effects in actual patients. Effects of treatments on pathophysiology that is demonstrated in clinical subtypes may be more likely to predict effectiveness in those subtypes than choosing medications based on structural similarities to established treatments.

Increased platelet intracellular calcium ion concentration is specific to bipolar disorder

BACKGROUND

Increased baseline ([Ca(2+)]B) and agonist-stimulated ([Ca(2+)]s) free intracellular calcium ion concentrations ([Ca(2+)]i) are well-replicated findings in bipolar disorder, but whether this finding is specific to that condition and if so, whether it is a marker of the mood disorder or a feature seen in other disorders such as psychosis has remained unclear.

METHODS

Platelet [Ca(2+)]i was assessed in 15 inpatients with psychotic and nonpsychotic mania, 17 schizophrenia inpatients, and 17 matched controls.

RESULTS

Platelet [Ca(2+)]B and [Ca(2+)]s were significantly higher than controls in bipolar disorder but not schizophrenia. Variability of [Ca(2+)]B was significantly increased in bipolar disorder regardless of the presence of psychosis, but not in schizophrenia.

LIMITATIONS

Use of antipsychotic drugs by the majority of both patient groups may have obscured elevated [Ca(2+)]i in schizophrenia, or may have masked a difference between psychotic and nonpsychotic bipolar disorder. Measurement of [Ca(2+)]i is too labor intensive to become a routine test for diagnosis or prediction of treatment response.

CONCLUSIONS

Elevated intracellular Ca(2+) signaling may be a marker of primary cellular hyperactivity that could contribute to comorbid conditions such as hypertension and neuronal apoptosis. Since lithium and carbamazepine attenuate increased [Ca(2+)]i, further research may demonstrate a correlation between normalization of [Ca(2+)]i and response to one of these medications, and further research may clarify whether a subgroup of patients may respond well to calcium channel antagonists.

Database of genetic studies of bipolar disorder

This study describes the construction and preliminary analysis of a database of summary level genetic findings for bipolar disorder from the literature. The database is available for noncommercial use at http://bioprogramming.bsd.uchicago.edu/BDStudies/. This may be the first complete collection of published gene-specific linkage and association findings on bipolar disorder, including genome-wide association studies. Both the positive and negative findings have been incorporated so that the statistical and contextual significance of each finding may be compared semi-quantitatively and qualitatively across studies of mixed technologies. The database is appropriate for searching a literature populated by mainly underpowered studies, and if 'hits' are viewed as tentative knowledge for future hypothesis generation. It can serve as the basis for a mega-analysis of candidate genes. Herein, we discuss the most robust and best replicated gene findings to date in a contextual manner.

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.

Effect of ouabain on sodium pump alpha-isoform expression in an animal model of mania

While the pathophysiologic mechanisms of bipolar illness are unknown, a dysregulation of electrolytes, particularly intracellular sodium (Na) and calcium (Ca), are thought to contribute to the illness. Ouabain, a potent Na pump inhibitor, administered intracerebroventricularly (ICV), has been used previously to model mania. The current study evaluates the effect of ICV ouabain on Na pump isoform expression in rat brain. Animals received 5 microl ICV of either 10(-3) M ouabain or artificial cerebrospinal fluid (aCSF). They were then sacrificed 7 days after the ICV injection and specific brain areas were dissected and frozen until the assay (frontal cortex, hippocampus, and basal ganglia). The three isoforms of the alpha subunit of the Na pump that are expressed in the brain were quantified with immunoblot analysis with actin serving as internal control. The behavioral hyperactivity seen in rats receiving ICV ouabain is associated with an increase of expression of the glial-specific alpha2 isoform in the basal ganglia, and the neuron-specific alpha3 isoforms in the frontal cortex. These findings, in association with human post mortem studies finding that alpha2 is underexpressed in the temporal cortex of bipolar subjects, suggest that Na pump isoform expression may be of interest in the pathophysiology of mania.

Mitochondrially mediated plasticity in the pathophysiology and treatment of bipolar disorder

Bipolar disorder (BPD) has traditionally been conceptualized as a neurochemical disorder, but there is mounting evidence for impairments of cellular plasticity and resilience. Here, we review and synthesize the evidence that critical aspects of mitochondrial function may play an integral role in the pathophysiology and treatment of BPD. Retrospective database searches were performed, including MEDLINE, abstract booklets, and conference proceedings. Articles were also obtained from references therein and personal communications, including original scientific work, reviews, and meta-analyses of the literature. Material regarding the potential role of mitochondrial function included genetic studies, microarray studies, studies of intracellular calcium regulation, neuroimaging studies, postmortem brain studies, and preclinical and clinical studies of cellular plasticity and resilience. We review these data and discuss their implications not only in the context of changing existing conceptualizations regarding the pathophysiology of BPD, but also for the strategic development of improved therapeutics. We have focused on specific aspects of mitochondrial dysfunction that may have major relevance for the pathophysiology and treatment of BPD. Notably, we discuss calcium dysregulation, oxidative phosphorylation abnormalities, and abnormalities in cellular resilience and synaptic plasticity. Accumulating evidence from microarray studies, biochemical studies, neuroimaging, and postmortem brain studies all support the role of mitochondrial dysfunction in the pathophysiology of BPD. We propose that although BPD is not a classic mitochondrial disease, subtle deficits in mitochondrial function likely play an important role in various facets of BPD, and that enhancing mitochondrial function may represent a critical component for the optimal long-term treatment of the disorder.

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.

Mitochondrial DNA-dependent effects of valproate on mitochondrial calcium levels in transmitochondrial cybrids

Calcium plays important roles in various cellular processes. Using transmitochondrial hybrid cells (cybrids) carrying fluorescent calcium indicators, we previously found two mitochondrial DNA (mtDNA) polymorphism sites, 8701 and 10398, that alter intracellular calcium signalling and mitochondrial pH. The 10398A polymorphism is reportedly associated with bipolar disorder, Parkinson's disease, Alzheimer's disease, and cancer, whereas 10398G is associated with longevity. In bipolar disorder, elevation of intracellular calcium levels in the platelets and lymphocytes is a well-replicated finding. Thus, we examined whether two mood stabilizers, lithium and valproate, affect the intracellular calcium signalling in cybrids with these mtDNA polymorphisms. After cybrids with 8701A/10398A and 8701G/10398G (three cell lines for each) derived from healthy controls were pretreated with lithium (0.75 mm or 1.5 mm) or valproate (0.6 mm or 1.2 mm) for 7 d, they were stimulated by 10 mum histamine. Valproate decreased mitochondrial calcium levels, compared with untreated cybrids, only in cybrids with 8701A/10398A. Moreover, valproate decreased cytosolic calcium levels at plateau after stimulation in cybrids with 8701A/10398A. These finding suggest that valproate may stabilize intracellular calcium only in cells with high mitochondrial calcium levels.

Effects of calmodulin and protein kinase C modulators on transient Ca2+ increase and capacitative Ca2+ entry in human platelets: relevant to pathophysiology of bipolar disorder

Disturbed intracellular calcium (Ca(2+)) homeostasis has been implicated in bipolar disorder, which mechanisms may be involved in the dysregulation of protein kinase C (PKC) and calmodulin systems. In this study, we investigated a transient intracellular Ca(2+) increase induced by thapsigargin, an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase pump (SERCA), and a capacitative Ca(2+) entry followed by addition of extracellular Ca(2+), in the presence or absence of PKC/calmodulin modulators in the platelets of healthy subjects in order to elucidate the role of SERCA in Ca(2+) homeostasis and to assess how both PKC and calmodulin systems regulate the two Ca(2+) responses. Moreover, we also examined the thapsigargin-elicited transient Ca(2+) increase and capacitative Ca(2+) entry in patients with mood disorders. PKC and calmodulin systems have opposite regulatory effects on the transient Ca(2+) increase and capacitative Ca(2+) entry in the platelets of normal subjects. The inhibitory effect of PKC activation on capacitative Ca(2+) entry is significantly increased and the stimulatory effect of PKC inhibition is significantly decreased in bipolar disorder compared to major depressive disorder and normal controls. These results suggest the possibility that increased PKC activity may activate the inhibitory effect of capacitative Ca(2+) entry in bipolar disorder. However, this is a preliminary study using a small sample, thus further studies are needed to examine the PKC and calmodulin modulators on the capacitative Ca(2+) entry in a larger sample.

Mimicking human bipolar ion dysregulation models mania in rats

Psychiatric diseases in general, and bipolar illness in particular, are difficult to model in animals since the subjective nature of the core symptoms appears to preclude objective observation of behavioral changes. An adequate animal model of a psychiatric condition must fulfill three core criteria: share pathophysiological characteristics of the human condition (face validity), have similar behavioral manifestations as the human disease (construct validity), and improve with medications that improve the symptoms seen in afflicted humans (predictive validity). The ouabain model for bipolar illness mimics a widely reproduced biologic abnormality in mania: reduced sodium pump activity. An intracerebroventricular (ICV) administration of 5microL 10(-3)M ouabain induces motoric hyperactivity preventable by lithium, carbamazepine, and haloperidol. ICV ouabain may also produce environmentally dependent hypoactivity. The model, however, has not yet been examined for other potential manic behavior in rats such as reduced need for sleep, increased sexual activity, or increased irritability. While additional characterization of the model is required, the ouabain model for bipolar illness is the only available animal model that fulfills the three criteria for an adequate animal model for bipolar illness.

Modulation of phosphoinositide-protein kinase C signal transduction by omega-3 fatty acids: implications for the pathophysiology and treatment of recurrent neuropsychiatric illness

The phosphoinositide (PI)-protein kinase C (PKC) signal transduction pathway is initiated by pre- and postsynaptic Galphaq-coupled receptors, and regulates several clinically relevant neurochemical events, including neurotransmitter release efficacy, monoamine receptor function and trafficking, monoamine transporter function and trafficking, axonal myelination, and gene expression. Mounting evidence for PI-PKC signaling hyperactivity in the peripheral (platelets) and central (premortem and postmortem brain) tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, coupled with evidence that PI-PKC signal transduction is down-regulated in rat brain following chronic, but not acute, treatment with antipsychotic, mood-stabilizer, and antidepressant medications, suggest that PI-PKC hyperactivity is central to an underlying pathophysiology. Evidence that membrane omega-3 fatty acids act as endogenous antagonists of the PI-PKC signal transduction pathway, coupled with evidence that omega-3 fatty acid deficiency is observed in peripheral and central tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, support the hypothesis that omega-3 fatty acid deficiency may contribute to elevated PI-PKC activity in these illnesses. The data reviewed in this paper outline a potential molecular mechanism by which omega-3 fatty acids could contribute to the pathophysiology and treatment of recurrent neuropsychiatric illness.

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.

Treatment of bipolar depression

This article discusses current practices in the treatment of bipolar depression. In the absence of more definitive research, the treatment of bipolar depression is guided by clinical experience and expert opinion, and sometimes by marketing and popular trends, as much as it is by hard data. Considering the limitations of current knowledge is an essential component of the scientific practice of psychiatry.

Lack of association between XBP1 genotype and calcium signaling in the platelets of healthy subjects

Dysregulations of calcium (Ca) homeostasis may be involved in the pathophysiology of bipolar disorder. Enhanced Ca response to various agonists in peripheral blood cells is one of a few confirmed biological markers for bipolar disorder. Recently, a polymorphism of XBP1, a pivotal gene in the endoplasmic reticulum (ER) stress response, was shown to contribute to the genetic risk factor for bipolar disorder. Thus, in this study, we examined the relationship between the XBP1 gene polymorphism and the Ca signaling in the platelets of healthy controls. The present results suggest no significant difference in the basal Ca level or 5-HT-induced Ca mobilization among normal subjects with -116C/C, C/G, and G/G genotypes. Further investigations are necessary to examine the relationship in the different peripheral blood cells and/or in larger samples from patients with bipolar disorder.

Effects of lithium and valproate on agonist-induced platelet intracellular calcium mobilization: relevance to myosin light chain kinase

Serotonin (5-HT)- or thrombin-stimulated platelet intracellular calcium (Ca) mobilization has been reported to be enhanced in patients with bipolar disorders. However, the mechanism of this enhancement is unknown. As a preliminary study, the authors examined the effects of a myosin light chain kinase (MLCK) inhibitor, 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9), and two drugs that are mainstays of treatment for bipolar disorder, lithium and valproate, on 5-HT- or thrombin-induced Ca increase in the platelets of normal subjects. When preincubated with 30 microM ML-9, Ca responses to both agonists were enhanced. Valproate showed a dose-dependent attenuation of agonist-induced intracellular Ca rise, both in the absence and presence of ML-9. Although lithium alone had no significant effect on the Ca increase, a high concentration of lithium significantly decreased Ca mobilization only in the presence of ML-9. These results suggest that the enhanced Ca response observed in bipolar disorder might be relevant to decreased function of MLCK and that the mechanism of action of lithium may include a compensatory effect on MLCK modulation.

The platelet window: examining receptor regulated second messenger processes in psychosis and depression

Peripheral markers of psychiatric illness provide a potentially important window into the pathophysiology of a number of psychiatric illnesses. Direct access to pathophysiological processes is fraught with difficulty. However, receptor-regulated second messenger-mediated calcium shifts are an accessible and practical method by which to examine changes in a clinical population. This is possible because platelets and neurons share some physiological features. The platelet intracellular calcium response to receptor stimulation has previously been used as a peripheral marker of psychiatric illness across a range of neurotransmitters, including serotonin, dopamine and glutamate. This review considers the specificity and selectivity of this response and its use in psychotic and mood disorders.

Intracerebroventricular administration of ouabain as a model of mania in rats

BACKGROUND

Human bipolar illness is characterized by mood state- and diagnosis-associated abnormalities of cellular cation distribution and transport. These include reduced sodium pump activity and expression and increased intracellular sodium. If these alterations are related to the pathophysiology of the disease, rather than secondary or ancillary abnormalities, then one would expect that modeling of these changes in vivo would produce lithium-preventable behavioral abnormalities.

METHODS

Ouabain, a potent inhibitor of the sodium pump, was administered intracerebroventricularly to male rats previously fed lithium-containing food or plain rat chow. Locomotion was then quantified in an open field.

RESULTS

Ouabain increased locomotion 300% over baseline. Lithium pretreatment prevented the ouabain-induced hyperlocomotion response.

CONCLUSION

Inhibition of central nervous system sodium pump with ouabain produces a plausible animal model of mania. This model may be useful for preclinical screening of potential mood stabilizers.

Altered 5-HT-induced calcium response in the presence of staurosporine in blood platelets from bipolar disorder patients

We have reported that the platelet intracellular calcium (Ca) mobilization after stimulation by serotonin (5-HT) is specifically enhanced in bipolar disorder among various psychiatric disorders, compared with that in normal control. To explore the mechanisms of enhanced Ca response to 5-HT in the platelets, we first examined the relation between the 5HT-elicited Ca mobilization and 5-HT(2A) receptor density using the platelets from 13 normal subjects. From this study, we found no significant correlation between two measures. Then, we investigated the effects of staurosporine, a protein kinase C (PKC) inhibitor, on Ca response to 5-HT in platelets from patients with major depressive disorder (unipolar), bipolar disorder, and normal controls. While 5-HT-induced Ca mobilization, in the presence of 100 nM staurosporine, was significantly attenuated in normal controls and patients with major depressive disorder, the inhibitory effect of staurosporine was not observed in bipolar disorder. These results suggest that the failure in inhibiting the platelet intracellular Ca response to 5-HT in bipolar disorder may be related to increased activity of PKC rather than increased 5-HT(2A) receptor number. Moreover, the trend of the Ca response towards staurosporine may become a specific biological marker for unipolar-bipolar dichotomy.

Effect of ethacrynic acid on sodium pump alpha isoforms in SH-SY5Y cells

BACKGROUND

Ethacrynic acid (ECA), a diuretic that has several cellular actions, increases expression of the sodium and potassium-activated adenosine triphosphatase (Na, K-ATPase or Na pump) in normal lymphocytes, but not in lymphocytes of bipolar patients. While this has been proposed to be important in the pathophysiology of bipolar illness, the response of neural tissues to ECA is unknown.

METHODS

Human neuroblastoma SH-SY5Y cells differentiated with 10-microM retinoic acid were treated with various ECA concentrations for 3 days, and changes in Na-pump alpha-isoform expression were quantified with densitometric analysis of Western bands.

RESULTS

Expression of alpha1 and alpha3 Na pump isoforms significantly increased with 10-5 M ECA. Cells treated with 10-6 or 10-7 M ECA showed no change in Na-pump expression, while cells treated with 10-4 M ECA died. The alpha2 isoform could not be detected in differentiated SH-SY5Y cells.

CONCLUSIONS

The effect of ECA on alpha1-isoform in neural tissue is similar to that observed in lymphocytes. As alpha3 isoform is not expressed in lymphocytes, however, we conclude that lymphocytes are an incomplete model of neural tissue.

Calcium homeostasis in long-term lithium-treated women with bipolar affective disorder

The authors investigated the effect of long-term lithium administration on intracellular calcium mobilization. The subjects were 13 women with bipolar affective disorder stabilized on lithium and 12 matched healthy controls. Total and ionized serum calcium, intracellular calcium ion concentration, plasma parathyroid hormone (PTH) and tyrotropin (TSH), serum electrolytes and cyclic AMP (cAMP) activity in platelets were measured. The serum electrolytes sodium, potassium and creatinine and plasma PTH and TSH were all within normal ranges in patients and controls and no differences were found between the two groups. No difference was found in basal and prostaglandin E1 (PGE1)-stimulated cAMP generation in platelets between patients and controls. However, total serum calcium and ionized serum calcium levels were higher in patients than in controls and there was a significant correlation between these two measures. In the patient group, serum lithium concentration correlated positively with stimulated levels of intracellular calcium in platelets. In the present study, no distinct hyperparathyroidism was found in lithium-treated patients. However, our findings indicate that lithium administration affects calcium metabolism in patients with bipolar affective disorder inducing mild hypercalcemia and a dose-dependent normalized calcium mobilization. Furthermore, our results did not support the hypothesis that lithium's primary site of action in bipolar illness may be on signal transduction mechanisms.

Evaluation of neuroprotection by lithium and valproic acid against ouabain-induced cell damage

BACKGROUND

The pathophysiology of manic-depression may be associated with dysregulation of ion homeostasis. Ouabain is a potent inhibitor of the sodium-potassium adenosine triphosphatase and has been purported to mimic abnormalities seen in acute mania. As manic episodes are believed to be neurotoxic and mood stabilizers have recently been implicated as neuroprotectants, it is of interest to determine if lithium and valproic acid antagonize ouabain-induced neurotoxicity.

METHODS

Human neuroblastoma SH-SY5Y cells were differentiated for 12 days then pretreated with lithium or valproic acid for 24 h and then challenged with a 10 microM ouabain insult. Cellular damage was assessed with lactate dehydrogenase (LDH) release, and apoptotic potential of ouabain was evaluated with DNA fragmentation.

RESULTS

Ouabain significantly increased LDH release after 72 h of treatment. Lithium pretreatment at 1 mM diminished ouabain-induced LDH release. Valproic acid alone at 100 and 1000 micrograms/mL significantly increased LDH release from the cells. Furthermore, it significantly potentiated ouabain-induced LDH release. DNA fragmentation suggests that ouabain induces apoptosis.

CONCLUSIONS

Lithium at the therapeutic level of 1 mM limits the extent of cellular damage caused by 10 microM ouabain in SH-SY5Y cells as measured by LDH release. Valproic acid alone at the therapeutic concentration of 100 micrograms/mL induces LDH release and does not prevent ouabain-induced LDH release.

Endophenotypes in bipolar disorder

The search for genes in bipolar disorder has provided numerous genetic loci that have been linked to susceptibility to developing the disorder. However, because of the genetic heterogeneity inherent in bipolar disorder, additional strategies may need to be employed to fully dissect the genetic underpinnings. One such strategy involves reducing complex behaviors into their component parts (endophenotypes). Abnormal neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, and neuropsychological findings are characteristics that often accompany psychiatric illness. It is possible that some of these may eventually be useful in subdefining complex genetic disorders, allowing for improvements in diagnostic assessment, genetic linkage studies, and development of animal models. Findings in patients with bipolar disorder that may eventually be useful as endophenotypes include abnormal regulation of circadian rhythms (the sleep/wake cycle, hormonal rhythms, etc.), response to sleep deprivation, P300 event-related potentials, behavioral responses to psychostimulants and other medications, response to cholinergics, increase in white matter hyperintensities (WHIs), and biochemical observations in peripheral mononuclear cells. Targeting circadian rhythm abnormalities may be a particularly useful strategy because circadian cycles appear to be an inherent evolutionarily conserved function in all organisms and have been implicated in the pathophysiology of bipolar disorder. Furthermore, lithium has been shown to regulate circadian cycles in diverse species, including humans, possibly through inhibition of glycogen synthase kinase 3-beta (GSK-3beta), a known target of lithium.

The neurobiology of bipolar disorder: focus on signal transduction pathways and the regulation of gene expression

OBJECTIVE

This article presents an overview of signal transduction pathways and reviews the research undertaken to study these systems in clinically relevant samples from patients with bipolar disorder (BD).

METHOD

We reviewed the published findings from studies of postmortem brain tissue and blood samples from patients with BD.

RESULTS

Although the exact biochemical abnormalities have yet to be identified, the presented findings strongly suggest that BD may be due, at least in part, to abnormalities in signal transduction mechanisms. In particular, altered levels or function, or both, of G-protein alpha subunits and effector molecules such as protein kinase A (PKA) and protein kinase C (PKC) have consistently been associated with BD both in peripheral cells and in postmortem brain tissue, while more recent studies implicate disruption in novel second-messenger cascades, such as the ERK/MAPK pathway.

CONCLUSIONS

Despite the difficulties inherent in biochemical studies of clinically relevant tissue samples, numerous investigations have illuminated the signal transduction mechanisms in patients with BD. These studies also suggest that BD may be due to the interaction of many abnormalities. In this context, novel techniques enabling the study of gene expression promise to assist in untangling these complex interactions, through visualizing the end result of these changes at the level of gene transcription.

Rapid cycling bipolar disease: new concepts and treatments

Having been recognized by Kraeplin at the beginning of the 20th century, rapid cycling was first described as a specific entity by Dunner et al. in 1974. The prevalence of rapid cycling ranges from 12% to 20% in patients with bipolar disorder who are not selected for a high rate of cycling.

Nucleotide sequence analysis of the binding site on the inositol 1,4,5-trisphosphate type-1 receptor in bipolar disorder -- a negative study

Pharmacological studies of bipolar disorder suggest that dysfunction of calcium mobilization via phosphatidylinositol-mediated transduction may be involved in its pathogenesis. The present study tests the hypothesis that dysfunction of calcium mobilization in bipolar disorder is due to the mutation of the nucleotide sequence in the FKBP12 binding site on the inositol 1,4,5-trisphosphate type-1 receptor (IP(3)R1). Nucleotide sequence analysis of the FKBP12 binding site on IP(3)R1 was performed using reverse transcription-polymerase chain reaction and DNA sequencing. The nucleotide sequence in this region was preserved in all subjects. This finding suggests that IP(3)R1 dysfunction through the FKBP12 binding site is not involved in the pathogenesis of bipolar disorder.

Serotonin-induced platelet intracellular calcium mobilization in various psychiatric disorders: is it specific to bipolar disorder?

BACKGROUND

Serotonin (5-HT)-stimulated platelet intracellular calcium (Ca) mobilization has been reported to be enhanced in unmedicated depressive patients compared to those of normal healthy subjects, which suggests increased 5-HT2A receptor function in these patients. It has not been ascertained whether this enhanced response is specific to some type of affective disorders among various mental disorders.

METHODS

We examined 5-HT-induced platelet intracellular Ca response in 152 unmedicated outpatients with various psychiatric disorders including bipolar disorder (BD), major depressive disorder with melancholia (DM), major depressive disorder without melancholia (DN), schizophrenia (SCH), panic disorder (PD), obsessive-compulsive disorder (OCD), social phobia (SP) and bulimia nervosa (BN), and 30 normal controls.

RESULTS

We observed no significant differences in basal intracellular Ca concentration among all patient subgroups and normal controls. While the 5-HT-induced Ca response was significantly and specifically higher in patients with BD than in normal controls, no significant differences were found in the Ca response to 5-HT between patients with DM, DN, SCH, PD, OCD, SP and BN, and normal controls.

LIMITATIONS

The sample sizes of each group are still small. Therefore, they have to be enlarged in the continuation of the study so as to increase the power of the statistical tests.

CONCLUSION

These results indicate the possibility that enhanced signal transduction, mediated by the 5-HT2A receptor, may be specific to bipolar disorder.

Elevated P-selectin on platelets in depression: response to bupropion

Increased platelet activation has been suggested as a possible reason for the increased vulnerability of depressed patients to ischemic heart disease (IHD). Translocation of P-selectin, an integral alpha-granule membrane protein, to the platelet surface is a measure of platelet activation. Herein, western blots of platelet plasma membranes containing P-selectin were quantified in patients with major depression (n=19; mean age=39 +/- 2 years) and healthy comparison subjects (n=17; mean age=36 +/- 2 years). None evidenced clinical signs of IHD, and only two patients had a lifestyle IHD risk factor (smoking). Blood was obtained from all 19 depressed patients before treatment, and 15 returned after 6-8 weeks of open-label bupropion treatment. Bupropion was chosen as the antidepressant because it did not elevate plasma norepinephrine or serotonin, endogenous agonists that can induce platelet degranulation. Western blotting revealed more P-selectin immunoreactivity (75 kD band) in depressed patients compared to healthy controls (P=0.003). After bupropion treatment, P-selectin remained high in depressed patients. beta3-Integrin, a reference plasma membrane protein that does not translocate during activation, was of equivalent density in depressed patients and healthy control subjects, and was unchanged after treatment with bupropion. P-Selectin failed to correlate with severity of illness based on the Hamilton Depression scale, or with the post-treatment plasma concentration of bupropion. The results suggest an elevation in P-selectin on platelet plasma membranes might be a trait marker for depression.

Serotonin stimulation of calcium mobilisation in human platelets: choice of units of measurement, effects of age and tobacco use, and correlation with serotonin2A receptor density

The calcium responses to serotonin and thrombin, as assessed using the fluorescent indicator Fura-2, have been investigated in platelets taken from 59 non-smokers and 17 smokers. The peak responses above baseline, calculated either as fluorescence ratios or calibrated calcium concentrations, were in the order of magnitude thrombin 520 mU/ml > thrombin 52 mU/ml >> serotonin 1 micromol/l approximately serotonin 100 micromol/l. Multiple regression analyses indicated that the responses to 1 micromol/l serotonin, but not the responses to thrombin, were significantly correlated with the serotonin2A receptor density measured using [3H]LSD as radioligand. No effects of age, gender, smoking habit or the time of year of sampling were seen on the calcium responses to serotonin and thrombin. It is concluded that cellular processes distal to the serotonin2A receptor recognition site may compensate to some extent for the large differences in recognition site expression, thus underlining the importance of providing a functional correlate in addition to [3H]LSD binding site densities when studying platelet serotonin2A receptors in neuropsychiatric disorders. The measurement of Ca2+ responses to serotonin provides a useful such functional correlate.

Elevated basal and thapsigargin-stimulated intracellular calcium of platelets and lymphocytes from bipolar affective disorder patients measured by a fluorometric microassay

BACKGROUND

A number of investigators have reported finding elevated basal and stimulated intracellular calcium levels in the platelets or lymphocytes of bipolar disorder patients.

METHODS

Intracellular calcium was measured by a micro fura-2 fluorometric method in the platelets and lymphocytes of 30 affective disorder patients and 14 control subjects.

RESULTS

We observed significantly elevated basal calcium concentrations in bipolar patient platelets and lymphocytes compared to control subjects. Bipolar patient platelet calcium responses to thrombin, serotonin, and thapsigargin were also significantly greater than control subjects. The peak calcium levels of lymphocytes of bipolar patients were greater than control subjects only when stimulated by thapsigargin. There were significant differences between bipolar and unipolar patients in basal and thapsigargin-stimulated calcium measures but not between bipolar I and bipolar II patients. Unmedicated versus medicated calcium measures were not significantly different. We also found little correlation between calcium measures and the severity of mood rating.

CONCLUSIONS

Using this method, we were able to confirm and extend the work of others, indicating altered intracellular calcium homeostasis in the blood cells of bipolar disorder patients. In addition, our data suggest that storage operated calcium channels may be the source of the elevated intracellular calcium in platelets and lymphocytes of bipolar patients.

Serotonin-induced platelet intracellular Ca2+ responses in untreated depressed patients and imipramine responders in remission

BACKGROUND

Intracellular Ca2+ metabolism in platelets has been investigated as a peripheral marker of affective disorders.

METHODS

We investigated the intracellular free Ca2+ concentration in platelets in both untreated depressed patients with no medications and patients in remission who were treated by imipramine (IMI) (IMI responders) using a Ca(2+)-sensitive fluorescent probe fura-2.

RESULTS

The increases in intracellular free Ca2+ concentration in platelets induced by stimulation with serotonin (5-HT) ([Ca2+] delta) were significantly higher in both the untreated patients and the IMI responders compared with healthy controls; however, there were no significant differences in the basal Ca2+ levels in the platelets ([Ca2+]B) among the three groups. On the other hand, in the IMI responders, we observed positive correlations between the duration of the remission and [Ca2+]B, but not [Ca2+] delta.

CONCLUSIONS

Our present data suggest that the enhancement of 5-HT2A-induced Ca2+ responses persisted after remission in depressed patients, and that the duration of the remission is a factor varying the intracellular basal Ca2+ levels.

Platelet membrane phospholipids in euthymic bipolar disorder patients: are they affected by lithium treatment?

BACKGROUND

Abnormalities in cell membrane processes and intracellular signal transduction pathways may be implicated in the pathophysiology of bipolar disorder. In this study, we attempted to investigate, in euthymic bipolar patients: 1) in vivo signal transduction abnormalities of the phosphatidylinositol pathway in platelets; and 2) possible in vivo effects of lithium treatment on platelet membrane phospholipids.

METHODS

We determined the relative absorbances of eight individual classes of platelet membrane phospholipids, using two-dimensional thin-layer chromatography in high-performance plates, followed by scanning laser densitometry, in a group of 10 lithium-treated euthymic bipolar patients and 11 normal controls.

RESULTS

The mean relative absorbance of phosphatidyl-inositol-4,5-bisphosphate (PIP2) was lower in the patient group (0.29 +/- 0.08% vs. 0.39 +/- 0.12%; t = 2.35, df = 19, p = .03); no significant differences between patients and controls were found for the other phospholipids.

CONCLUSIONS

This study provides in vivo evidence that bipolar patients on lithium treatment exhibit a decreased relative amount of PIP2 in the platelet cell membranes compared to normal controls.

Alpha 2 isoform of the Na,K-adenosine triphosphatase is reduced in temporal cortex of bipolar individuals

BACKGROUND

The pathophysiology of bipolar illness has been associated with changes in transmembrane ion flux and redistribution of biologically active ions. The recent identification of multiple isoforms of Na,K-adenosine triphosphatase (ATPase) alpha and beta subunits raises the possibility of altered pump isoform expression.

METHODS

We determined Na,K-ATPase alpha subunit expression in postmortem temporal cortex gray matter from individuals suffering from bipolar disorder, schizoaffective disorder, schizophrenia, and matched normal controls. Quantification of isoform expression was accomplished via densitometric scanning of Western blots utilizing isoform-specific antibodies.

RESULTS

Bipolar individuals exhibited a significant reduction in the abundance of the alpha 2 isoform of Na,K-ATPase compared to normal controls. Schizophrenic and schizo-affective brains were not significantly different from normal controls.

CONCLUSION

These data suggest that previously observed abnormalities in regulation and distribution of ions in bipolar illness may be related to specific alpha 2 dysregulation.

Electrolytes in erythrocytes of patients with depressive disorders

The concentrations of calcium, sodium, potassium and magnesium in the erythrocytes of patients were measured in the active and remission phases of depressive disorders. Twelve patients in the active phase and 19 patients in remission with major depression were studied and compared with 20 age-matched healthy controls. Patients with major depression in both active and remission phases showed significantly lower calcium concentrations in the erythrocytes compared with controls, although no significant differences in sodium, potassium or magnesium concentrations were found among the three groups. In addition, no differences were found in the electrolyte concentrations between the active and remission phases in the same patients. This calcium concentration had no relationship to the age, gender, or medication drugs of the subjects. Low calcium concentrations were found in the erythrocytes of depressed patients, which may be a relevant marker for depression.

Effect of antidepressants on intracellular Ca++ mobilization in human frontal cortex

BACKGROUND

It is well documented that central serotonin (5-HT)2 receptor dysfunction is involved in the biochemistry and pathophysiology of depression and might be corrected by antidepressant drug treatment.

METHODS

The effect of imipramine (IMI) and fluoxetine (FLX) on 5-HT2A receptor-mediated intracellular calcium ([Ca++]i) mobilization in synaptosomes of human frontal cortex was studied. [Ca++]i was measured using Fura-2AM.

RESULTS

It was observed that in response to 5-HT (10 mumol/L) there was a significant increase (254%; p < .001) in [Ca++]i compared to basal level (140.00 +/- 31.77 nmol/L/mg protein). Both IMI and FLX (10-1000 nmol/L) induce mobilization of basal [Ca++]i in a dose-dependent manner. IMI and FLX antagonize the 5-HT-stimulated [Ca++]i mobilization in a dose-dependent manner. IMI showed higher antagonizing effect at lower concentration (10 nmol/L); however, FLX showed maximum antagonizing effect at higher concentration (1000 nmol/L).

CONCLUSIONS

It is observed that imipramine and fluoxetine have different effects on antagonizing the 5-HT response in frontal cortex. One mode of action of these antidepressants might be by decreasing the intracellular calcium.

Nimodipine monotherapy and carbamazepine augmentation in patients with refractory recurrent affective illness

Of 30 patients with treatment-refractory affective illness, 10 showed a moderate to marked response to blind nimodipine monotherapy compared with placebo on the Clinical Global Impressions Scale. Fourteen inadequately responsive patients (3 unipolar [UP], 11 bipolar [BP]) were treated with the blind addition of carbamazepine. Carbamazepine augmentation of nimodipine converted four (29%) of the partial responders to more robust responders. Patients who showed an excellent response to the nimodipine-carbamazepine combination included individual patients with patterns of rapid cycling, ultradian cycling, UP recurrent brief depression, and one with BP type II depression. When verapamil was blindly substituted for nimodipine, two BP patients failed to maintain improvement but responded again to nimodipine and remained well with a blind transition to another dihydropyridine L-type calcium channel blocker (CCB), isradipine. Mechanistic implications of the response to the dihydropyridine L-type CCB nimodipine alone and in combination with carbamazepine are discussed.

The role of calcium in the etiology of the affective disorders

Calcium abnormalities are some of the more consistent findings in platelets of affective disorder patients. While medication status does not correlate with this finding, antidepressants do modulate intracellular calcium. This, in combination with reports that calcium channel inhibitors may have antidepressant potential, suggests that calcium may play an important role in this disorder. This paper reviews the specificity of calcium abnormalities for the affective disorders and also discusses possible mechanisms of action.

Pathophysiological effects of dietary essential fatty acid balance on neural systems

Dietary fatty acid balance has been revealed to affect neural functions as well as chronic diseases such as cancer, cerebro- and cardiovascular diseases, and allergic hyper-reactivity. In this review, we focused on the pathophysiological effects of n-6 and n-3 fatty acids on brain functions. Long-term n-3 fatty acid deficiency in the presence of n-6 fatty acids has been shown to affect learning behavior, drug sensitivity and retinal functions. Some membrane enzymes and ion channel functions have been shown in experimental animals to be regulated by membrane fatty acid modifications. We also summarized the effects of these fatty acids in diets on human psychotic aspects and brain diseases. Although biochemical mechanisms remain to be elucidated, investigations on the effect of dietary fatty acids on neural networks may provide an important clue to clarify complex brain functions.

Platelet cytosolic calcium responses to serotonin in depressed patients and controls: relationship to symptomatology and medication

BACKGROUND

Serotonin produces an exaggerated rise in platelet cytosolic calcium (delta [Ca++]i) in patients with mood disorders. Studies on patients with bipolar disorder consistently demonstrate calcium abnormalities. By comparison, data on patients with major depression are more variable.

METHODS

To determine causes of variability, we utilized Fura-2 loaded platelets to compare changes in platelet intracellular calcium levels (delta [Ca++]i) following serotonin stimulation in 24 patients with major depression and in 20 controls. We also sought relationships between the delta [Ca++]i responses and scores on clinical depression and anxiety scales.

RESULTS

We found positive correlations between delta [Ca++]i responses and the clinical scales across all subjects. Furthermore, depressed patients with high anxiety had significantly increased delta [Ca++]i responses compared to depressed patients with low anxiety. In addition, patients receiving selective-serotonin reuptake inhibitors (SSRIs) demonstrated reduced delta [Ca++]i responses compared to patients not on SSRIs.

CONCLUSIONS

Since elevations in [Ca++]i mediate platelet aggregation and secretion cascades, the enhanced responsivity observed in depressed, and in particular anxious, depressed patients may contribute to their increased risk for vascular disease.

Comparative studies of the biological distinction between unipolar and bipolar depressions

Although unipolar depression and bipolar depression are considered distinct entities both by clinicians and researchers, it is not clear whether a pathophysiological distinction, which is the bridge between etiology and treatment, exists between these two conditions. The objective of this paper was to systematically review the studies that examined the biological differences between unipolar and bipolar depression. Using computerized Medline and manual searches, we located and reviewed studies that directly compared patients with unipolar depression with bipolar depressed patients on at least one biological variable. The results showed that patients with bipolar depression had lower levels of urinary NE and its metabolites and lower platelet MAO activity, and higher platelet free and stimulated intracellular calcium levels compared with unipolar depressed patients, but none of the variables examined appeared to differentiate the two groups consistently. We discuss some of the methodological flaws that might have contributed to this, and suggest that further studies should control for such confounding variables.

Calibration of Fura-2 signals introduces errors into measurement of thrombin-stimulated calcium mobilisation in human platelets

The intracellular calcium indicator dye Fura-2 has been widely used for the study of human platelet thrombin receptor-mediated calcium mobilisation in disease states. In general, authors (a) use a Fura-2/AM concentration of 2-3 mumol/l and (b) calibrate fluorescence signals on the basis of maximum and minimum ratios of fluorescence (Rmax and Rmin) and the ratio of the calcium-free and calcium-bound fluorescence at an excitation wavelength of 380 nm ("C2/B2"). In the present study, it is found (a) that a greater peak response to thrombin is seen when 1 mumol/l Fura-2/AM rather than 2 or 3 mumol/l is used; and (b) that calibration leads to a poorer test-retest reliability and in general a greater variability of the obtained calcium signal than when the simple measurement of the 340 nm/380 nm fluorescence ratio is used. It is suggested that this poor variability is due to the presence of an extracellular factor that can quench the Fura-2 signal once the platelets have been permeabilised by detergent treatment. Consistent with this, addition of bovine serum albumin to the assay medium has no significant effect on the fluorescence ratio response to thrombin, but greatly increases the observed calibrated calcium signal.