Post-stress changes in BDNF and Bcl-2 immunoreactivities in hippocampal neurons: effect of chronic administration of olanzapine

Investigation of protective effects of olanzapine on impaired learning and memory using behavioral tests in a rat model of Alzheimer's disease

Introduction

Evidence suggests that oxidative stress plays a critical role in the pathogenesis and progression of Alzheimer's disease (AD). Consequently, antioxidants may mitigate neurotoxicity induced by beta-amyloid (Aβ) and potentially reduce cell death. Previous research has demonstrated that olanzapine (OLZ) possesses antioxidant and neuroprotective properties. In this study, we investigated the protective and therapeutic effects of OLZ on an animal model of AD induced by Aβ using behavioral assessments.

Methods

Rats were randomly assigned to one of five groups (n = 10 rats per group): a control group, a sham group that received an intracerebrovascular (ICV) injection of phosphate-buffered saline (the solvent for Aβ), an AD group that received an ICV injection of Aβ, an OLZ group that received OLZ via gavage for two months, and an AD + OLZ group that received OLZ for one month before and one month after AD induction.

Results

We used the Elevated Plus Maze (EPM), Novel Object Recognition Test (NORT), Barnes Maze (BM), Passive Avoidance Test (PAT), and Morris Water Maze (MWM) to assess behavioral performance in the experimental rats. Aβ administration impaired cognition and increased anxiety-like behavior. Treatment with OLZ improved cognitive decline and reduced anxiety-like behavior in Aβ-infused rats.

Conclusion

Our findings suggest that OLZ can restore cognitive performance and alleviate anxiety-like behavior following Aβ injection. Thus, OLZ may have both preventive and therapeutic potential for AD and could be considered a viable pharmacological option.

The effect of olanzapine on spatial memory impairment, depressive-like behavior, pain perception, and BDNF and synaptophysin expression following childhood chronic unpredictable mild stress in adult male and female rats

Chronic unpredictable mild stress (CUMS) method has been introduced as a rodent model of depression. On the other hand, olanzapine, as an antipsychotic, can induce antidepressant and antipsychotic effects. Also, olanzapine may improve cognitive functions. Both CUMS and olanzapine can also affect the expression level of brain-derived neurotrophic factor (BDNF) and synaptophysin, the molecular factors involved in synaptic function, and learning and memory. In this study, we investigated the effect of olanzapine on locomotor activity (using open field test), pain threshold (using hot plate), depressive-like behavior (using forced swim test), spatial learning and memory (using Morris water maze), and BDNF and synaptophysin hippocampal expression (using real-time PCR) in both male and female CUMS rats. CUMS was performed for three consecutive weeks. Olanzapine was also injected intraperitoneally at the dose of 5 mg/kg. Our data showed that olanzapine can reverse the effects of CUMS on behavioral functions and BDNF and synaptophysin expression levels in the hippocampus of both males and females. It was also shown that olanzapine effects on spatial memory, pain perception, and BDNF and synaptophysin level were stronger in females than males. In conclusion, we suggested that the therapeutic effects of olanzapine in CUMS rats may be closely related to the function of BDNF and synaptophysin. Also, the therapeutic effects of olanzapine may be stronger in females. Therefore, and for the first time, we showed that there may be a sex difference in the effects of olanzapine on behavioral and molecular changes following CUMS.

Sex differences in cognition following variations in endocrine status

Spatial memory, mediated primarily by the hippocampus, is responsible for orientation in space and retrieval of information regarding location of objects and places in an animal's environment. Since the hippocampus is dense with steroid hormone receptors and is capable of robust neuroplasticity, it is not surprising that changes in spatial memory performance occur following a variety of endocrine alterations. Here, we review cognitive changes in both spatial and nonspatial memory tasks following manipulations of the hypothalamic-pituitary-adrenal and gonadal axes and after exposure to endocrine disruptors in rodents. Chronic stress impairs male performance on numerous behavioral cognitive tasks and enhances or does not impact female cognitive function. Sex-dependent changes in cognition following stress are influenced by both organizational and activational effects of estrogen and vary depending on the developmental age of the stress exposure, but responses to gonadal hormones in adulthood are more similar than different in the sexes. Also discussed are possible underlying neural mechanisms for these steroid hormone-dependent, cognitive effects. Bisphenol A (BPA), an endocrine disruptor, given at low levels during adolescent development, impairs spatial memory in adolescent male and female rats and object recognition memory in adulthood. BPA's negative effects on memory may be mediated through alterations in dendritic spine density in areas that mediate these cognitive tasks. In summary, this review discusses the evidence that endocrine status of an animal (presence or absence of stress hormones, gonadal hormones, or endocrine disruptors) impacts cognitive function and, at times, in a sex-specific manner.

Dysregulation of adult hippocampal neuroplasticity in major depression: pathogenesis and therapeutic implications

Major depressive disorder (MDD) was previously hypothesized to be a disease of monoamine deficiency in which low levels of monoamines in the synaptic cleft were believed to underlie depressive symptoms. More recently, however, there has been a paradigm shift toward a neuroplasticity hypothesis of depression in which downstream effects of antidepressants, such as increased neurogenesis, contribute to improvements in cognition and mood. This review takes a top-down approach to assess how changes in behavior and hippocampal-dependent circuits may be attributed to abnormalities at the molecular, structural, and synaptic level. We conclude with a discussion of how antidepressant treatments share a common effect in modulating neuroplasticity and consider outstanding questions and future perspectives.

miRNA-Coordinated Schizophrenia Risk Network Cross-Talk With Cardiovascular Repair and Opposed Gliomagenesis

Background

Schizophrenia risk genes are widely investigated, but a systemic analysis of miRNAs contributing to schizophrenia is lacking.

Methods

Schizophrenia-associated genetic loci profiles were derived from a genome-wide association study (GWAS) from the Schizophrenia Working Group of the Psychiatric Genomics Consortium (PGC) dataset. Experimentally confirmed relationships between miRNAs and their target genes were retrieved from a miRTarBase. A competitive gene set association analysis for miRNA-target regulations was conducted by the Multi-marker Analysis of GenoMic Annotation (MAGMA) and further validated by literature-based functional pathway analysis using Pathway Studio. The association between the targets of three miRNAs and schizophrenia was further validated using a GWAS of antipsychotic treatment responses.

Results

Three novel schizophrenia-risk miRNAs, namely, miR-208b-3p, miR-208a-3p, and miR-494-5p, and their targetomes converged on calcium voltage-gated channel subunit alpha1 C (CACNA1C) and B-cell lymphoma 2 (BCL2), and these are well-known contributors to schizophrenia. Both miR-208a-3p and miR-208b-3p reduced the expression of the RNA-binding protein Quaking (QKI), whose suppression commonly contributes to demyelination of the neurons and to ischemia/reperfusion injury. On the other hand, both QKI and hsa-miR-494-5p were involved in gliomagenesis.

Conclusion

Presented results point at an orchestrating role of miRNAs in the pathophysiology of schizophrenia. The sharing of regulatory networks between schizophrenia and other pathologies may explain higher cardiovascular mortality and lower odds of glioma previously reported in psychiatric patients.

Repeated olanzapine treatment mitigates PTSD like symptoms in rats with changes in cell signaling factors

Post Traumatic Stress Disorder is an anxiety disorder with prolonged distortion of rational behavior. In this study, we report the preclinical potential of olanzapine (OLZ) in the treatment of PTSD. Since the atypical antipsychotics have modulating effects on cell protective and destructive factors, we tested the effects of OLZ in PTSD regarding these cell modulating factors. Rats, when subjected to stress-restress (SRS) model of PTSD, showed a derangement in cell protective factors like the decline in BDNF, ERK, and CREB. While the adversarial factors like caspase-3 were enhanced. Four weeks treatment with OLZ at doses of 1 and 10 mg/kg significantly mitigated the SRS-induced derangement related to PTSD. OLZ at doses of 1 and 10 mg/kg enhanced BDNF, ERK and CREB levels which were reduced by SRS in PTSD animals. Further, at the fore mentioned doses it also inhibited the elevation of caspase-3 a downstream apoptotic factor. Besides, OLZ also showed mitigation in behavioral alterations related to anxiety and memory brought about by PTSD. These effects of OLZ were comparable to that of paroxetine a clinically approved drug for PTSD in terms of biochemical and behavioral assessments indicating its anti-PTSD potential.

Flupirtine attenuates chronic restraint stress-induced cognitive deficits and hippocampal apoptosis in male mice

Chronic restraint stress (CRS) causes hippocampal neurodegeneration and hippocampus-dependent cognitive deficits. Flupirtine represents neuroprotective effects and we have previously shown that flupirtine can protect against memory impairment induced by acute stress. The present study aimed to investigate whether flupirtine could alleviate spatial learning and memory impairment and hippocampal apoptosis induced by CRS. CRS mice were restrained in well-ventilated Plexiglass tubes for 6h daily beginning from 10:00 to 16:00 for 21 consecutive days. Mice were injected with flupirtine (10mg/kg and 25mg/kg) or vehicle (10% DMSO) 30min before restraint stress for 21 days. After stressor cessation, the spatial learning and memory, dendritic spine density, injured neurons and the levels of Bcl-2, Bax, p-Akt, p-GSK-3β, p-Erk1/2 and synaptophysin of hippocampal tissues were examined. Our results showed that flupirtine significantly prevented spatial learning and memory impairment induced by CRS in the Morris water maze. In addition, flupirtine (10mg/kg and 25mg/kg) treatment alleviated neuronal apoptosis and the reduction of dendritic spine density and synaptophysin expression in the hippocampal CA1 region of CRS mice. Furthermore, flupirtine (10mg/kg and 25mg/kg) treatment significantly decreased the expression of Bax and increased the p-Akt and p-GSK-3β, and flupirtine (25mg/kg) treatment up-regulated the p-Erk1/2 in the hippocampus of CRS mice. These results suggested that flupirtine exerted protective effects on the CRS-induced cognitive impairment and hippocampal neuronal apoptosis, which is possibly associated with the activation of Akt/GSK-3β and Erk1/2 signaling pathways.

The involvement of ERK/CREB/Bcl-2 in depression-like behavior in prenatally stressed offspring rats

A number of studies reveal that prenatal stress (PS) may induce an increased vulnerability to depression in offspring. Some evidences indicate that extracellular signal-regulated kinase (ERK)-cyclic AMP responsive element binding protein (CREB) signal system may play an important role in the molecular mechanism of depression. In the present study, we examined the effects of prenatal restraint stress on depression-like behavior in one-month offspring Sprague-Dawley rats and expression of ERK2, CREB, B-cell lymphoma-2 (Bcl-2) mRNA in the hippocampus, prefrontal cortex and striatum to explore the potential role of ERK-CREB pathway in mediating the behavioral effects of PS exposure. Our findings demonstrated that PS increased immobility time in forced swimming test and decreased expression of ERK2, CREB, Bcl-2 mRNA in the hippocampus and prefrontal cortex of juvenile offspring rats except for CREB in hippocampus of male offspring. Changes induced by PS were partly prevented by MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist. These findings suggested that the ERK-CREB system might be related with the depression-like behavior in juvenile offspring rats subjected to PS, in which NMDA receptors might be involved.

Behavioural and neurochemical changes induced by stress-related conditions are counteracted by the neurokinin-2 receptor antagonist saredutant

These experiments were undertaken to assess the mechanisms underlying the antidepressant-like effects of the neurokinin-2 (NK(2)) receptor antagonist saredutant (SR48968) in rats tested in the forced swim test (FST), by analysing hippocampal brain-derived neurotrophic factor (BDNF) and plasma corticosterone [as index of hypothalamic-pituitary-adrenal (HPA) axis activity]. Male Wistar rats received three intraperitoneal injections over 24 h of vehicle, saredutant (5 mg/kg), citalopram (15 mg/kg), clomipramine (50 mg/kg). Rats were subjected to restraint stress (4 h) 24 h prior to the FST procedure. This stress procedure increased immobility and decreased swimming behaviour in the FST; furthermore, it lowered hippocampal BDNF protein expression and increased plasma corticosterone levels. Saredutant and clomipramine or citalopram, used here as positive controls, reduced the immobility time in the FST both under basal conditions and after stress exposure. This effect was not attributable to changes in locomotion, because locomotor activity was unchanged when assessed in the open field test. Pretreatment with para-cholorophenylalanine (150 mg/kg, 72 h and 48 h prior to FST) abolished the effect of citalopram and saredutant on immobility time. At neurochemical level, saredutant attenuated activation of HPA axis in stressed animals more than clomipramine or citalopram. The behavioural effects of saredutant support the hypothesis that NK(2) receptor activity is involved in stress-related disorders. These effects of saredutant may be related to normalization of the HPA axis. Moreover, saredutant increases BDNF expression in the hippocampus, confirming the role of NK(2) receptor blockade in BDNF activation following stressor application.

The Role of Neurotrophins in Major Depressive Disorder

Neurotrophins and other growth factors have been advanced as critical modulators of depressive behavior. Support for this model is based on analyses of knockout and transgenic mouse models, human genetic studies, and screens for gene products that are regulated by depressive behavior and/or antidepressants. Even subtle alteration in the regulated secretion of brain-derived neurotrophic factor (BDNF), for example, due to a single nucleotide polymorphism (SNP)-encoded Val-Met substitution in proBDNF that affects processing and sorting, impacts behavior and cognition. Alterations in growth factor expression result in changes in neurogenesis as well as structural changes in neuronal cytoarchitecture, including effects on dendritic length and spine density, in the hippocampus, nucleus accumbens, and prefrontal cortex. These changes have the potential to impact the plasticity and stability of synapses in the CNS, and the complex brain circuitry that regulates behavior. Here we review the role that neurotrophins play in the modulation of depressive behavior, and the downstream signaling targets they regulate that potentially mediate these behavioral pro-depressant and antidepressant effects.

Effects of fluoxetine, tianeptine and olanzapine on unpredictable chronic mild stress-induced depression-like behavior in mice

AIMS

Tianeptine is an atypical antidepressant drug that has a different mechanism of action than other antidepressants. Olanzapine is an atypical antipsychotic drug used for the treatment of schizophrenia. The present study was undertaken to investigate effects of chronic administration of tianeptine or olanzapine on unpredictable chronic mild stress (UCMS)-induced depression-like behavior in mice compared to a widely used SSRI antidepressant, fluoxetine.

MAIN METHODS

Male inbred BALB/c mice were subjected to different kinds of stressors several times a day for 7weeks and were treated intraperitoneally with tianeptine (5mg/kg), olanzapine (2.5mg/kg), fluoxetine (15mg/kg) or vehicle for 5weeks (n=7-8 per group).

KEY FINDINGS

All the drugs tested prevented stress-induced deficit in coat state during UCMS procedure, in grooming behavior in the splash test, decreased the attack frequency in the resident intruder test and decreased the immobility time in the tail suspension test. In the open field test olanzapine had anxiolytic-like effects in both stressed and non-stressed mice. Tianeptine, olanzapine and fluoxetine decreased the enhanced levels of plasma ACTH and IL-6. Chronic treatment with tianeptine resulted in a significant increase in both total number and density of BrdU-labeled cells in stressed animals, while fluoxetine and olanzapine had a partial effect.

SIGNIFICANCE

The results of this study support the hypothesis that tianeptine can be as effective as fluoxetine for the treatment of depression in spite of the differences in the mechanism of action of these drugs. Moreover, olanzapine could be used effectively in psychotic patients with depression.

Effects of 4-weeks of treatment with lithium and olanzapine on long-term potentiation in hippocampal area CA1

Neuroplastic theories propose that lithium has robust neuroprotective and neurotrophic actions leading to the up-regulation of synaptic plasticity, and this action may be associated with the efficacy of lithium in the treatment of bipolar disorder. Olanzapine, an atypical antipsychotic drug, is efficacious in the treatment of bipolar disorder. It has been suggested that olanzapine may also up-regulate synaptic plasticity by its neuroprotective and neurotrophic actions, and this action may be related to antipsychotic and anti-manic effects of the drug. However, few studies have directly examined whether these drugs alter synaptic plasticity. In the present study, to examine the effects of lithium and olanzapine on synaptic plasticity, we examined the effects of chronic treatment with lithium and olanzapine on long-term potentiation (LTP) and input and output (I/O) responses of field excitatory postsynaptic potentials (fEPSP) of CA1 pyramidal cells in hippocampal slices prepared from rats administered the drugs for 4 weeks. Our results show that 4 weeks of lithium treatment magnified LTP of CA1 pyramidal cells. However, the same treatment with olanzapine did not magnify LTP of CA1 pyramidal cells. Four weeks of treatment with lithium did not alter I/O responses of CA1 pyramidal cells. However, the same treatment with olanzapine increased I/O responses of CA1 pyramidal cells. The results suggest that lithium up-regulates synaptic plasticity in the hippocampus, and olanzapine increases synaptic transmission without apparent changes in LTP in the hippocampus.

Different impacts of aquaporin 4 and MAOA allele variation among olanzapine, risperidone, and paliperidone in schizophrenia

Apoptosis has been considered to be involved in schizophrenia. Water channels are modulated just before apoptosis. In the aquaporin family, aquaporin 4 (AQP-4) is most highly expressed in the brain and is supposed to play an important role in a neuronal environment. In this clinical study, we investigated the relationship between the AQP-4 polymorphism and drug response in schizophrenia under the control of the MAOA (monoamine oxidase A) promoter gene. We recruited 91 patients with schizophrenia, and they were randomized to receive olanzapine (n = 44), risperidone (n = 23), or paliperidone (n = 24). Genotyping of AQP-4 and MAOA polymorphisms was done in all patients. Patients with the AQP-4 non-C polymorphism needed a higher dosage of olanzapine for treatment (z = 4.163, P = 0.041), and patients with a short form of the MAOA polymorphism needed a higher dosage of risperidone for treatment (z = 5.124, P = 0.024). Patients who smoked cigarettes needed a higher dosage of olanzapine for treatment (z = 4.905, P = 0.027), but cigarette smoking did not affect the dosage of paliperidone. The AQP-4 polymorphism may have an effect in influencing the dosage of olanzapine. However, the roles of AQP-4 polymorphisms in the blood-brain barrier and different neuroprotective effects need further exploration in future studies.

Fluoxetine affects hippocampal plasticity, apoptosis and depressive-like behavior of chronically isolated rats

Plastic response and successful adaptation to stress are of particular importance in the hippocampus, where chronic stress may cause cell death instead of neural remodeling. Structural modifications that occur both in the brain of depressed patients and animal stress models may be reversed by antidepressants. Since morphological changes induced by stress and/or antidepressants could be mediated by presynaptically located proteins, determining the levels of these proteins may be a useful way to identify molecular changes associated with synaptic plasticity. In this study we analyzed the effects of chronic (six-week) social isolation and long-term (three-week) fluoxetine treatment on molecular markers of plasticity and apoptosis in the hippocampus of Wistar rats. Compartmental redistribution of NFκB transcription factor involved in the regulation of plasticity and apoptosis was also examined. To establish whether social isolation is able to evoke behavioral-like effects, which might be related to the observed molecular changes, we performed the forced swimming test. The results show that synaptosomal polysialic neural cell adhesion molecule (PSA-NCAM), a molecular plasticity marker, was increased in the hippocampus of chronically isolated rats, while subsequent treatment with fluoxetine set it at the control level. In addition, analysis of cytoplasm/mitochondria redistribution of apoptotic proteins Bax and Bcl-2 after exposure to chronic isolation stress, revealed an increase in Bcl-2 protein expression in both compartments, while fluoxetine enhanced the effect of stress only in the mitochondria. The observed alterations at the molecular level were accompanied by normalization of stress-induced behavioral changes by fluoxetine.

Antipsychotics in the treatment of bipolar disorder

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

Depression: a repair response to stress-induced neuronal microdamage that can grade into a chronic neuroinflammatory condition?

Depression is a major contributor to the global burden of disease and disability, yet it is poorly understood. Here we review data supporting a novel theoretical model for the biology of depression. In this model, a stressful life event leads to microdamage in the brain. This damage triggers an injury repair response consisting of a neuroinflammatory phase to clear cellular debris and a spontaneous tissue regeneration phase involving neurotrophins and neurogenesis. During healing, released inflammatory mediators trigger sickness behavior and psychological pain via mechanisms similar to those that produce physical pain during wound healing. The depression remits if the neuronal injury repair process resolves successfully. Importantly, however, the acute psychological pain and neuroinflammation often transition to chronicity and develop into pathological depressive states. This hypothesis for depression explains substantially more data than alternative models, including why emerging data show that analgesic, anti-inflammatory, pro-neurogenic and pro-neurotrophic treatments have antidepressant effects. Thus, an acute depressive episode can be conceptualized as a normally self-limiting but highly error-prone process of recuperation from stress-triggered neuronal microdamage.

The beta3 adrenoceptor agonist, amibegron (SR58611A) counteracts stress-induced behavioral and neurochemical changes

These experiments were made to study the mechanisms underlying the antidepressant-like effects of the beta(3) adrenoceptor agonist amibegron (SR58611A). To this purpose, the expression levels of the hippocampal cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), B-cell lymphoma-2 (Bcl-2) and Bax proteins were assessed, by using western blot analysis, in rats tested in the forced swim test (FST). Under basal conditions (no previous exposure to stressors), different groups of male Wistar rats received acutely or repeatedly (once/day for 7days) intraperitoneal (i.p.) injections of amibegron (1, 5 and 10mg/kg), the tricyclic antidepressant (TCA) clomipramine (50mg/kg), the selective serotonin reuptake inhibitor (SSRI) citalopram (15mg/kg) or their vehicles. The influence of stress-related conditions was studied in rats subjected to acute (4h) or repeated (4h/day for 7days) restraint stress, applied prior to the FST procedure. Compared to the control groups, both stressor procedures increased the immobility time in the FST and reduced hippocampal BDNF and Bcl-2/Bax ratio proteins expression, which were counteracted by amibegron (5 and 10mg/kg) treatment. Opposite effects were found in the CREB expression, since it was lower after acute and higher after repeated stress procedure, respectively. Again, these effects were reversed by amibegron treatment. Different results were obtained in animals treated with clomipramine or citalopram. Hence, it is likely that the observed behavioral effects of amibegron could be due, at least in part, to its action on hippocampal expression of neurotrophic and/or anti-apoptotic factors, supporting the hypothesis that beta(3) adrenoceptors may be a therapeutic target for the treatment of stress-related disorders.

Efficacy, safety and tolerability of Symbyax for acute-phase management of treatment-resistant depression

Treatment resistance is frequently encountered during the long-term care of patients with major depression. A number of 'next step' therapeutic options exist in such cases, including switching to an alternative antidepressant, combining antidepressants from different pharmacological classes, adding evidence-supported psychotherapies to ongoing antidepressant treatment and augmentation with a nonantidepressant drug. Augmenting antidepressants with atypical antipsychotic drugs has generated considerable clinical interest. Three atypical antipsychotics (aripiprazole, quetiapine and olanzapine) have received regulatory approval for adjunctive use with antidepressants for treatment-resistant major depression (TRD) in adults. Symbyax (olanzapine-fluoxetine combination or OFC), the combination of olanzapine and the selective serotonin-reuptake inhibitor fluoxetine, is also approved for this indication. The short-term effectiveness of OFC for TRD is supported by results of five published randomized, controlled, acute-phase studies of generally similar design. In each study, OFC was associated with rapid reduction in depressive symptoms. In two studies, significantly greater improvement in depressive symptoms occurred in OFC-treated patients at study end point compared with those who received antidepressant monotherapy. These effects appeared to be strongest in cases where antidepressant failure was established during the current depressive episode. Although OFC was well-tolerated, increases in body weight and prolactin concentration were greater with OFC than antidepressant monotherapy, and were similar to olanzapine monotherapy. Increases in random total cholesterol levels were greatest for OFC, and were significantly greater than those of olanzapine and antidepressant monotherapy. The long-term efficacy and tolerability of OFC for TRD has not been investigated, and the comparative effectiveness of OFC versus other next-step options is unknown. As such, the exact place of OFC among the available therapeutic options for TRD is not fully understood at this time.

Increase in brain-derived neurotrophic factor in first episode psychotic patients after treatment with atypical antipsychotics

Some preclinical and postmortem studies suggest that the effects of atypical antipsychotics could be mediated by brain-derived neurotrophic factor (BDNF). Olanzapine is an atypical antipsychotic with shown efficacy in psychosis treatment. The aim of this study was to compare plasma BDNF levels at baseline and after 1 year of olanzapine treatment in 18 drug-naive patients who experienced a first psychotic episode with those of 18 healthy control participants matched by age, sex, and socioeconomic level. Plasma BDNF levels were measured in patients at the index episode and at 1, 6, and 12 months of follow-up using an enzyme-linked immunosorbent assay. Symptoms and functioning of patients and controls were assessed with the Positive and Negative Symptom Scale and Global Assessment of Function Scale. BDNF levels of patients at onset were significantly lower than controls but increased toward control values during olanzapine treatment. There was a significant positive correlation between BDNF levels and functioning (Global Assessment of Function Scale). BDNF levels were also negatively correlated with positive symptoms, but not with negative symptoms or general psychopathology. Results suggest that olanzapine can offset the low BDNF levels at the onset of first psychotic episodes, and improving psychotic symptoms. The increase in BDNF levels may be its mechanism of action in improving positive symptoms.

Resistance to the development of stress-induced behavioral despair in the forced swim test associated with elevated hippocampal Bcl-xl expression

Stress may predispose individuals toward depression through down-regulation of neurogenesis and increase in apoptosis in the brain. However, many subjects show high resistance to stress in relation to psychopathology. In the present study, we assessed the possibility that individual-specific patterns of gene expression associated with cell survival and proliferation may be among the molecular factors underlying stress resilience. Brain-derived neurotrophic factor (BDNF), anti-apoptotic B cell lymphoma like X (Bcl-xl) and pro-apoptotic bcl2-associated X protein (Bax) expression were determined in the hippocampus and frontal cortex of rats naturally differed in despair-like behavior in the forced swim test. In the hippocampus, BDNF messenger RNA (mRNA) level was significantly down-regulated 2h after the forced swim test exposure, and at this time point, Bcl-xl mRNA and protein levels were significantly higher in stressed than in untested animals. The ratios of hippocampal Bcl-xl to Bax mRNA negatively correlated with the total time spent immobile in the test. When animals were divided in two groups according to immobility responses in two consecutive swim sessions and designated as stress resilient if their immobility time did not increase in the second session as it did in stress sensitive rats, it was found that resilient rats had significantly higher Bcl-xl/Bax ratios in the hippocampus than stress sensitive animals. The data suggest that naturally occurring variations in the Bcl-xl/Bax ratio in the hippocampus may contribute to individual differences in vulnerability to stress-induced depression-like behaviors.

Fluoxetine and olanzapine combination therapy in treatment-resistant major depression: review of efficacy and safety data

BACKGROUND

There has been growing evidence supporting the use of atypical antipsychotic drugs as adjunctive treatments in patients with major depression who fail to respond adequately to antidepressants.

OBJECTIVE

To review the efficacy and safety data for one such combination, fluoxetine (FLX) + olanzapine (OLZ) in treatment-resistant depression (TRD).

METHODS

We reviewed published randomized, controlled acute-phase studies, as well as available long-term clinical studies.

RESULTS/CONCLUSIONS

In each acute-phase study (n = 5), FLX/OLZ group experienced rapid antidepressant effects and, in two of these studies, resulted in significantly greater improvement at study end point compared with antidepressant monotherapy. These effects were strongest when TRD was defined as having failed at least two antidepressant trials during the current depressive episode. FLX + OLZ was generally well tolerated; however, increases in body weight and prolactin levels with FLX + OLZ were greater than that of antidepressant monotherapy groups and were similar to OLZ monotherapy. However, changes in random total cholesterol were also greatest for FLX + OLZ and were greater in magnitude than that of OLZ or FLX monotherapy. Long-term effectiveness/safety data are sparse, and comparison trials and sequential treatment studies involving FLX + OLZ and other antidepressant-atypical antipsychotic combinations are lacking. Thus, the exact place of FLX + OLZ among other available options for TRD is difficult to determine.

Antidepressant properties of the 5-HT4 receptor partial agonist, SL65.0155: behavioral and neurochemical studies in rats

This study was undertaken to investigate the potential antidepressant-like properties of SL65.0155, a serotonin 5-HT(4) receptor partial agonist, in male rats of the Wistar strain tested in the forced swim test (FST), an experimental model widely used to assess antidepressant-like activity. The expression of hippocampal neurotrophic factors, such as the brain-derived neurotrophic factor (BDNF), the phosphorilated cAMP response element-binding protein (p-CREB), the B cell lymphoma-2 (Bcl-2), the Bax and the vascular endothelium growth factor (VEGF) were also evaluated by Western Blot analysis. Different groups of rats received intraperitoneally (i.p.) injections of SL65.0155 (0.1, 0.5 and 1 mg/kg), clomipramine (50 mg/kg), citalopram (15 mg/kg) or vehicle, respectively, 24, 5 and 1 h prior to the FST. Compared to the control group, SL65.0155 (0.5 and 1 mg/kg), clomipramine or citalopram injected animals showed an increased swimming and climbing behavior and reduced immobility time in the FST. Interestingly, this effect was not due to changes in the locomotor activity since all treated groups failed to show any change in motor ability as assessed in the open field test. Western blot analysis of hippocampal homogenates showed an enhancement of p-CREB, BDNF Bcl-2 and VEGF protein levels in SL65.0155 treated groups, but not in citalopram or clomipramine treated groups, used here as positive control. No change was found in Bax expression in any treated group. These findings give further support to the hypothesis that the stimulation of serotonin 5-HT(4) receptors may be a therapeutic target for depression.

Reverse translational strategies for developing animal models of bipolar disorder

Bipolar disorder (BD) affects a significant portion of the population of the world, yet there has been limited success in developing novel treatments for the disorder. One of the major reasons for this dearth is the absence of suitable animal models for BD. Traditionally, animal models of human phenomena have been evaluated based on similarity to the human syndrome, response to appropriately corresponding medications, and the degree to which a model supports a common mechanistic theory between the human disorder and the model itself. The following review emphasizes the use of 'reverse translation', drawing on patient-based findings to develop suitable animal models for BD. We highlight some examples of this strategy, emphasizing their construct validity as a starting point. These studies have produced informative models that have altered the expression of genes/pathways implicated in BD, including the point mutation D181A of mouse mitochondrial DNA polymerase (POLG), glutamate receptor 6 (GluR6), Clock, extracellular regulated kinase 1 (ERK1), glycogen synthase kinase-3beta (GSK-3beta), B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated athanogene (BAG-1). These studies demonstrate that this method is useful, viable and deserves attention in new efforts to generate animal models of BD.

Neuroprotective effect of atypical antipsychotics in cognitive and non-cognitive behavioral impairment in animal models

Antipsychotic drugs are divided into two groups: typical and atypical. Recent clinical studies show atypical antipsychotics have advantages over typical antipsychotics in a wide variety of neuropsychiatric conditions, in terms of greater efficacy for positive and negative symptoms, beneficial effects on cognitive functioning, and fewer extra pyramidal side effects in treating schizophrenia. As such, atypical antipsychotics may be effective in the treatment of depressive symptoms associated with psychotic and mood disorders, posttraumatic stress disorder and psychosis in Alzheimer disease. In this paper, we describe the effects and potential neurochemical mechanisms of action of atypical antipsychotics in several animal models showing memory impairments and/or non-cognitive behavioral changes. The data provide new insights into the mechanisms of action of atypical antipsychotics that may broaden their clinical applications.

Olanzapine and fluoxetine combination therapy for treatment-resistant depression: review of efficacy, safety, and study design issues

Treatment-resistant depression (TRD) is a common occurrence in clinical practice. Up to 30% of patients with major depression do not respond to conventional antidepressant treatment, while a significantly greater number of patients experience only partial symptom reduction. Numerous strategies may be applied by the practicing clinician to overcome limitations in the effectiveness of antidepressant monotherapy, including combining drug treatment with evidence-supported psychotherapies, combining antidepressants (combination pharmacotherapy), and combining antidepressants with other non-antidepressant psychotropic medications (augmentation treatment). One such augmentation strategy, the combination of the selective serotonin reuptake inhibitor, fluoxetine (FLX), with the atypical antipsychotic drug, olanzapine (OLZ), is supported by the results of four randomized, double-blind, acute phase studies of patients who had responded inadequately to antidepressant monotherapy. In each study, the FLX/OLZ combination caused rapid reduction in Montgomery-Asberg Depression Rating scale scores, with two of the four studies showing significantly greater improvement than antidepressant monotherapy at study endpoint. Effects of the FLX/OLZ combination were strongest in cases where failure to respond to two antidepressants prior to randomization was established during the current depressive episode. The FLX/OLZ combination was well-tolerated; however, body weight gain and increases in prolactin were greater than that of the antidepressant monotherapy groups, and were comparable to that of OLZ monotherapy. While effective during acute-phase treatment, questions remain regarding the long-term efficacy and safety of FLX/OLZ relative to antidepressant monotherapy and other combination strategies. Efforts aimed at determining the placement of FLX/OLZ among the available options for addressing TRD are limited by lack of comparison and sequential treatment studies. Important aspects of study design and directions for future research are discussed.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.

The effect of early maternal separation on brain derived neurotrophic factor and monoamine levels in adult heterozygous reeler mice

OBJECTIVE AND METHODS

The reeler heterozygous (HZ) mice have provided a model for studying the relationship between reelin (a protein of extracellular matrix) haploinsufficiency and the emergence of neuropsychiatric diseases. In a neurodevelopmental framework, the enduring consequences of early maternal separation (5 h/day during the first postnatal week, or handling controls, H) were studied in reeler HZ and wild type (WT) mice at adulthood. The modulatory effects of a chronic treatment with the atypical antipsychotic olanzapine (OLZ, 1.5 mg/kg for 40 days) were also investigated.

RESULTS

Early maternal separation had long-term effects on brain plasticity, with a reduction of brain- and glial- derived neurotrophic factor (BDNF and GDNF) in several brain areas of mice, but such a consequence was less marked in the HZ genotype. On the other hand, treatment with OLZ did not affect at all the GDNF but led to an increase of BDNF levels in maternally separated (SEP) mice, an effect which was far more marked in the HZ genotype. Brain levels of serotonin (5-HT) were markedly increased, striatal dopamine (DA) was increased, whereas metabolites and turnover were decreased, in SEP mice of both genotypes. The spontaneous home-cage activity was generally lower in HZ than WT mice, and OLZ treatment contrasted this hypoactivity profile. Maternal separation also decreased the interest toward an unknown mouse proposed as a social stimulus, but only in WT mice.

CONCLUSION

We investigated the interplay between genetic vulnerability (reelin haploinsufficiency), the outcome of early stressful experiences, and the efficacy of the antipsychotic drug therapy. The reeler HZ genotype exhibited a slightly lower sensitivity to the environmental insult as well as an enhanced response to the atypical antipsychotic treatment.

Repeated unpredictable stress and antidepressants differentially regulate expression of the bcl-2 family of apoptotic genes in rat cortical, hippocampal, and limbic brain structures

Apoptosis has been proposed as a contributing cellular mechanism to the structural alterations that have been observed in stress-related mood disorders. Antidepressants, on the other hand, are hypothesized to exert trophic and/or neuroprotective actions. The present study examined the regulation of the major antiapoptotic (Bcl-2, Bcl-xl) and proapoptotic (Bax) genes by repeated unpredictable stress (an animal model of depression) and antidepressant treatments (ADT). In adult rats, exposure to unpredictable stress reduced Bcl-2 mRNA levels in the central nucleus of the amygdala (CeA), cingulate (Cg), and frontal (Fr) cortices. Bcl-xl mRNA was significantly decreased in hippocampal subfields. In contrast, chronic administration of clinically effective antidepressants from four different classes, ie fluoxetine, reboxetine, tranylcypromine, and electroconvulsive seizures (ECS) upregulated Bcl-2 mRNA expression in the Cg, Fr, and CeA. Reboxetine, tranylcypromine, and ECS selectively increased Bcl-xl, but not Bcl-2 mRNA expression in the hippocampus. Chemical ADT but not ECS, robustly enhanced Bcl-2 expression in the medial amygdaloid nucleus and ventromedial hypothalamus. Fluoxetine did not influence Bcl-xl expression in the hippocampus, but it was the only ADT that decreased Bax expression in this region. In the CeA, again in direct contrast to the stress effects, exposure to all classes of ADTs significantly increased Bcl-2 mRNA. The selective regulation of Bcl-xl and Bax in hippocampal subfields and of Bcl-2 in the Cg cortex, amygdala, and hypothalamus suggests that these cellular adaptations contribute to the long-term neural plastic adaptations to stress and ADTs in cortical, hypothalamic, and limbic brain structures.

Neuroprotective effect of chronic lithium treatment against hypoxia in specific brain regions with upregulation of cAMP response element binding protein and brain-derived neurotrophic factor but not nerve growth factor: comparison with acute lithium treatment

OBJECTIVES

We evaluated the neuroprotective effect of chronically or acutely administered lithium against hypoxia in several brain regions. Furthermore, we investigated the contribution of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and cAMP response element binding protein (CREB) to the neuroprotective effect of lithium.

METHODS

Brain slices were prepared from rats that had been treated chronically or acutely with lithium. The cerebral glucose metabolic rate (CMRglc) before and after hypoxia loading to brain slices was measured using the dynamic positron autoradiography technique with [(18)F]2-fluoro-2-deoxy-D-glucose. The changes of expression of proteins were investigated using Western blot analysis.

RESULTS

Before hypoxia loading, the CMRglc did not differ between the lithium-treated and untreated groups. After hypoxia loading, the CMRglc of the untreated group was significantly lower than that before hypoxia loading. However, the CMRglc of the chronic lithium treatment group recovered in the frontal cortex, caudate putamen, hippocampus and cerebellum, but not in the thalamus. In contrast, the CMRglc of the acute lithium treatment group did not recover in any analyzed brain regions. After chronic lithium treatment, the levels of expression of BDNF and phospho-CREB were higher than those of untreated rats in the frontal cortex, but not in the thalamus. However, the expression of NGF did not change in the frontal cortex and thalamus.

CONCLUSIONS

These results demonstrated that lithium was neuroprotective against hypoxia only after chronic treatment and only in specific brain regions, and that CREB and BDNF might contribute to this effect.

Protective effects of olanzapine and haloperidol on serum withdrawal-induced apoptosis in SH-SY5Y cells

PURPOSE

Recent clinical studies have suggested that treatment with second generation antipsychotic drugs such as olanzapine may prevent progressive alterations of brain structure in patients with schizophrenia. However, the molecular mechanisms underlying these different effects remain to be determined. We investigated the mechanisms of action of olanzapine and haloperidol, on serum withdrawal apoptosis in human neuroblastoma SH-SY5Y cells.

METHODS

SH-SY5Y cells were cultured with olanzapine and haloperidol in medium with or without serum. We determined the effects of the drugs on cell viability against serum withdrawal by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, to explore the drugs' actions, Western blot was performed to examine the expression of key genes involved in GSK-3beta-mediated signaling, notably GSK-3beta, beta-catenin, and Bcl-2.

RESULTS

SH-SY5Y cells suffered about a 38% loss in cell number under serum-free conditions for 48 h. Olanzapine (10-200 muM) up to 100 muM significantly attenuated serum withdrawal-induced cell loss (p<0.01), and a dose of 100 muM also increased cell viability (p<0.05). In contrast, haloperidol (0.01-10 muM) did not affect cell viability but exacerbated cell death at 10 muM under serum-free conditions (p<0.01). Western blot analysis showed that olanzapine, but not haloperidol, prevented the serum withdrawal-induced decrease in levels of neuroprotective proteins such as p-GSK-3beta, beta-catenin, and Bcl-2 (p<0.01), whereas haloperidol robustly reduced the levels of these proteins at a 10 muM dose in serum-starved cells (p<0.05). Moreover, olanzapine alone significantly increased phosphorylation of GSK-3beta under normal conditions (p<0.05).

CONCLUSIONS

This study showed that olanzapine may have neuroprotective effects, whereas haloperidol was apparently neurotoxic. The actions of signaling systems associated with GSK-3beta may be key targets for olanzapine and haloperidol, but their effects are distinct. These differences suggest different therapeutic effects of first and second generation antipsychotic drugs in patients with schizophrenia.

Beneficial effects of quetiapine in a transgenic mouse model of Alzheimer's disease

Previous studies have suggested that quetiapine, an atypical antipsychotic drug, may have beneficial effects on cognitive impairment, and be a neuroprotectant in treating neurodegenerative diseases. In the present study, we investigated the effects of quetiapine on memory impairment and pathological changes in an amyloid precursor protein (APP)/presenilin-1 (PS-1) double transgenic mouse model of Alzheimer's disease (AD). Non-transgenic and transgenic mice were treated with quetiapine (0, 2.5, or 5mg/(kg day)) for 1, 4, and 7 months in drinking water from the age of 2 months. After 4 and 7 months of continuous quetiapine administration, memory impairment was prevented, and the number of beta-amyloid (Abeta) plaques decreased in the cortex and hippocampus of the transgenic mice. Quetiapine also decreased brain Abeta peptides, beta-secretase activity and expression, and the level of C99 (an APP C-terminal fragment following cleavage by beta-secretase) in the transgenic mice. Furthermore, quetiapine attenuated anxiety-like behavior, up-regulated cerebral Bcl-2 protein, and decreased cerebral nitrotyrosine in the transgenic mice. These findings suggest that quetiapine can alleviate cognitive impairment and pathological changes in an APP/PS1 double transgenic mouse model of AD, and further indicate that quetiapine may have preventive effects in the treatment of AD.

Brain-derived neurotropic factor/TrkB signaling in the pathogenesis and novel pharmacotherapy of schizophrenia

The role of neurotropins, predominantly brain-derived neurotropic factor (BDNF), has been implicated in the pathophysiology as well as treatment outcome of schizophrenia. Both human and rodent studies indicate that the beneficial effects of antipsychotic drugs are mediated, at least in part, through BDNF and its receptor, TrkB. This review will discuss the available data on the levels of BDNF and TrkB in subjects with schizophrenia and in animals with and without conventional antipsychotics. The data concerning the impact of the antipsychotic drugs on BDNF/TrkB signaling will also be discussed. More importantly, this review will provide future perspective on BDNF/TrkB signaling as a novel molecular target to correct the pathogenesis and improve the long-term clinical outcome by treatments with conventional and adjunctive drugs.

Chronic stress and neural function: accounting for sex and age

Cognitive responses to stress follow the temporally dependent pattern originally established by Selye (1) wherein short-term stressors elicit adaptive responses whereas continued stress (chronic) results in maladaptive changes--deleterious effects on physiological systems and impaired cognition. However, this pattern for cognitive effects appears to apply to only half the population (males) and, more specifically, to young, adult males. Females show different cognitive responses to stress. In contrast to impaired cognition in males after chronic stress, female rodents show enhanced performance on the same memory tasks after the same stress. Not only cognition, but anxiety, shows sex-dependent changes following chronic stress--stress is anxiolytic in males and anxiogenic in females. Moreover, behavioral responses to chronic stress are different in developing as well as aging subjects (both sexes) as compared to adults. In aged rats, chronic stress enhances recognition memory in both sexes, does not alter spatial memory, and anxiety effects are opposite to young adults. When pregnant dams are exposed to chronic stress, at adulthood the offspring display yet different consequences of stress on anxiety and cognition, and, in contrast to adulthood when the behavioral effects of stress are reversible, prenatal stress effects appear enduring. Changing levels of estradiol in the sexes over the lifespan appear to contribute to the differences in response to stress. Thus, theories of stress dependent modulations in CNS function--developed solely in male models, focused on peripheral physiological processes and tested in adults--may require revision when applied to a more diverse population (age- and sex-wise) at least in relation to the neural functions of cognition and anxiety. Moreover, these results suggest that other stressors and neural functions should be investigated to determine whether age, sex and gonadal hormones also have an impact.

Stress and ageing interactions: A paradox in the context of shared etiological and physiopathological processes

Gerontology has made considerable progress in the understanding of the mechanisms underlying the ageing process and age-related neurodegenerative disorders. However, ways to improve quality of life in the elderly remain to be elucidated. It is now clear that stress and the ageing process share a number of underlying mechanisms bound in a very close, if not indissociable, relationship. The ageing process is regulated by the factors underlying the ability to adjust to stress, whilst stress has an influence on the life span and the quality of ageing. In addition, the ability to cope with stress in adulthood predicts life expectancy and quality of life at senescence. The ageing process and stress also share several common mechanisms, particularly in relation to the energy factor. Stress consumes energy and ageing may be considered as a cost of the energy expended to deal with the stressors to which the body is exposed throughout its lifetime. This suggests that the ageing process is associated with and/or a consequence of a long-lasting activation of the major stress responsive systems. However, despite common features, the interaction between stress and the ageing process gives rise to some paradoxes. Stress can either diminish or exacerbate the ageing process just as the ageing process can worsen or counter the effects of stress. There has been little attempt to understand how ageing and stress might interact to promote "successful" or pathological ageing. A key factor in this respect is the individual's ability to adapt to stress. Viewed from this angle, the quality of life of aged subjects may be improved through therapy designed to improve the tolerance to stress.

Food intake and reward mechanisms in patients with schizophrenia: implications for metabolic disturbances and treatment with second-generation antipsychotic agents

Obesity is highly prevalent among patients with schizophrenia and is associated with detrimental health consequences. Although excessive consumption of fast food and pharmacotherapy with such second-generation antipsychotic agents (SGAs) as clozapine and olanzapine has been implicated in the schizophrenia/obesity comorbidity, the pathophysiology of this link remains unclear. Here, we propose a mechanism based on brain reward function, a relevant etiologic factor in both schizophrenia and overeating. A comprehensive literature search on neurobiology of schizophrenia and of eating behavior was performed. The collected articles were critically reviewed and relevant data were extracted and summarized within four key areas: (1) energy homeostasis, (2) food reward and hedonics, (3) reward function in schizophrenia, and (4) metabolic effects of the SGAs. A mesolimbic hyperdopaminergic state may render motivational/incentive reward system insensitive to low salience/palatability food. This, together with poor cognitive control from hypofunctional prefrontal cortex and enhanced hedonic impact of food, owing to exaggerated opioidergic drive (clinically manifested as pain insensitivity), may underlie unhealthy eating habits in patients with schizophrenia. Treatment with SGAs purportedly improves dopamine-mediated reward aspects, but at the cost of increased appetite and worsened or at least not improved opiodergic capacity. These effects can further deteriorate eating patterns. Pathophysiological and therapeutic implications of these insights need further validation via prospective clinical trials and neuroimaging studies.

Possible Mechanisms of Neurodegeneration in Schizophrenia

Brain morphological alterations in schizophrenic patients have led to the neurodevelopmental hypothesis of schizophrenia. On the other hand, a progressive neurodegenerative process has also been suggested and some follow-up studies have shown progressive morphological changes in schizophrenic patients. Several neurotransmitter systems have been suggested to be involved in this disorder and some of them could lead to neuronal death under certain conditions. This review discusses some of the biochemical pathways that could lead to neurodegeneration in schizophrenia showing that neuronal death may have a role in the etiology or natural course of this disorder.

The effects of chronic administration of quetiapine on the methamphetamine-induced recognition memory impairment and dopaminergic terminal deficit in rats

Previous studies have suggested that quetiapine, a new atypical antipsychotic drug, may have beneficial effects on cognitive impairment and be a neuroprotectant in treating neurodegenerative diseases. In the present study, we investigated the therapeutic effects of chronic administration of quetiapine on methamphetamine (METH)-induced recognition memory impairment and dopaminergic terminal neurotoxicity in rats. Rats were pretreated with METH (5 mg/kg; s.c.) four times at 2-h intervals while their body temperature was monitored. Fifteen minutes after the last METH injection, rats were administered quetiapine (10 mg/kg/day; i.p.) for 28 days. One day after the last quetiapine injection, rats were trained and tested on an object recognition task on days 29 and 30. Finally, on day 31, rats were sacrificed for immunohistochemistry, 1 day after the object recognition task. METH induced hyperthermia, recognition memory impairment and a decrease of tyrosine hydroxylase immunoreactivity in the caudate putamen (CPu) of striatum. Quetiapine attenuated the METH-induced hyperthermia. Furthermore, chronic post-treatment of quetiapine reversed the METH-induced memory impairment and dopaminergic terminal deficit. These findings suggest that quetiapine may have therapeutic effects in the treatment of cognitive impairment and neurodegeneration induced by METH.

The effects of chronic administration of quetiapine on the phencyclidine-induced reference memory impairment and decrease of Bcl-XL/Bax ratio in the posterior cingulate cortex in rats

Quetiapine, a new atypical antipsychotic drug, effectively alleviates positive and negative symptoms, as well as cognitive impairment that may be caused by neurodegeneration, in schizophrenia patients. Earlier in vivo and in vitro studies have demonstrated that quetiapine may be a neuroprotectant. The present study was designed to examine the beneficial effects of quetiapine on the possible cognitive impairment and changes of brain apoptotic regulation proteins induced by phencyclidine (PCP) in rats. Rats were treated with quetiapine (10 mg/kg/day; intraperitoneal (i.p.)) or vehicle for 16 days. On day 14, 1 h after the administration of quetiapine, the rats were given PCP (50 mg/kg; subcutaneous (s.c.)) or vehicle. Then quetiapine was administrated for an additional 2 days. One day after the last quetiapine injection (3 days after the PCP injection), the rats were trained on a spatial memory task in a radial arm maze. After the behavioural test, the rats were decapitated for Western blot analysis. PCP induced reference memory impairment, and a decrease of the ratio of an anti-apoptotic Bcl-2 family member (Bcl-XL) to a pro-apoptotic analogue (Bax) in the posterior cingulate cortex. Chronic administration of quetiapine counteracted the PCP-induced reference memory impairment and decrease of Bcl-XL/Bax ratio in the posterior cingulate cortex. These results suggest that quetiapine may have ameliorating effects on the cognitive impairment and brain apoptotic processes induced by PCP.

Quetiapine reverses the suppression of hippocampal neurogenesis caused by repeated restraint stress

Quetiapine is an atypical antipsychotic effective in treating the positive, negative, and cognitive symptoms of patients with schizophrenia. Our previous study has shown that chronic administration of quetiapine attenuates the decrease in levels of brain-derived neurotrophic factor (BDNF) in the hippocampi of rats subjected to chronic-restraint stress. In the present study, we investigated the effects of quetiapine on hippocampal neurogenesis that had been compromised in stressed rats. Newborn cells in the hippocampus were labeled by bromodeoxyuridine (BrdU), and immature neurons were detected immunohistochemically using an antibody against phosphorylated cAMP response element-binding protein (pCREB). The restrained rats (4 h/day for 7 days) showed lower levels of hippocampal neurogenesis indicated by decreased numbers of BrdU-labeled and pCREB-positive cells. Post-stress administration of quetiapine (10 mg/kg) for 7 or 21 days reversed the stress-induced suppression of hippocampal neurogenesis, evidenced in the numbers of BrdU-labeled and pCREB-positive cells that are comparable to those in non-stressed rats but higher than those in the vehicle-treated rats. The results may help us understand the therapeutic effects of quetiapine on cognitive deficits in patients with schizophrenia and depression, in which the structure and functions of the hippocampus are implicated.

Olanzapine and quetiapine protect PC12 cells from β-amyloid peptide25-35-induced oxidative stress and the ensuing apoptosis

We previously found that the atypical antipsychotic drugs (APDs) clozapine, olanzapine, quetiapine, and risperidone reduce PC12 cell death induced by hydrogen peroxide, N-methyl-4-phenylpyridinium ion, or beta-amyloid peptide (Abeta(25-35)). Such neurotoxic substances have in common the capability of causing oxidative stress. Atypical APDs have been used in treating schizophrenia and in treating psychotic symptoms of patients with Alzheimer's disease (AD), in which Abeta is involved by causing oxidative stress. Therefore, we hypothesized that atypical APDs might alleviate oxidative stress in PC12 cells, thus protecting them from apoptosis. PC12 cells were seeded in plates or chambers for 24 hr and cultured for another 24 hr with olanzapine or quetiapine in the medium, and then the cells were cultured in the new medium containing Abeta(25-35) and/or olanzapine, quetiapine, but not serum, for various periods. It was shown that cultures treated with olanzapine + Abeta(25-35), or quetiapine + Abeta(25-35), had significantly higher cell viabilities and lower rates of apoptosis compared with the cultures exposed only to Abeta(25-35). In addition, the drugs blocked the activation of caspase-3 caused by Abeta(25-35). Furthermore, olanzapine and quetiapine prevented Abeta(25-35)-induced overproduction of intracellular reactive oxygen species, Abeta(25-35)-induced decrease in mitochondrial membrane potential, and Abeta(25-35)-induced changes in activities of the key antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. In consideration of the wealth of evidence linking oxidative stress to the pathophysiology of schizophrenia and AD, these findings give us a new insight into the therapeutic actions of atypical antipsychotics in patients with the disorders.

Olanzapine attenuates the okadaic acid-induced spatial memory impairment and hippocampal cell death in rats

It is hypothesized that olanzapine, an atypical antipsychotic drug, has beneficial effects on cognitive impairment and neuropathological changes in treating neurodegenerative diseases. In the present study, we investigated the effects of chronic administration of olanzapine on the spatial memory impairment and hippocampal cell death induced by the direct injection of okadaic acid (OA), a potent neurotoxin, into the rat hippocampus. After being pretreated with olanzapine (0.5 or 2 mg/kg/day, i.p.) for 2 weeks, the rats were unilaterally microinjected with OA (100 ng) into the hippocampus, and then were continuously administrated with olanzapine for an additional week The rats were trained on a spatial memory task in an eight-arm radial maze before OA administration, and tested on the same task 18 h after the last olanzapine injection. After the behavioral test, the rats were killed for Nissl staining and terminal deoxynucleutidyl transferase-mediated biotinylated UTP nick end labeling staining. OA significantly induced spatial memory impairment, and caused pyramidal cell loss in the CAI and apoptotic cell death in the hippocampus. Olanzapine significantly attenuated OA-induced spatial memory impairment and the OA-induced neuropathological changes in the hippocampus. These findings suggest that olanzapine may have therapeutic effects in treatment of cognitive impairment and neuropathological changes of schizophrenia and other neurodegenerative diseases.

Chronic administration of quetiapine alleviates the anxiety-like behavioural changes induced by a neurotoxic regimen of dl-amphetamine in rats

We have demonstrated that the atypical antipsychotic drugs prevent cell death in PC12 cells induced by various cytotoxins and have protective effects on methamphetamine-induced neurotoxcity in rats. The present study was designed to examine the possible effects of chronic administration of quetiapine, an atypical antipsychotic drug, on the anxiety-like behavioural consequences of a neurotoxic regimen of dl-amphetamine. Rats were treated with quetiapine (10 mg/kg/day; i.p.) for 33 days. During days 15-19 of this period, the animals were given dl-amphetamine (20 mg/kg/day; s.c.) 1 h after the administration of quetiapine. The repeated administration of dl-amphetamine resulted in a decrease of tyrosine hydroxylase (TH) immunostaining in the caudate putamen, hyperthermia, and anxiety-like behavioural changes. The behavioural changes were indicated by a significant increase in the time spent in the light box in the light/dark box test, an increase in the ratios of ambulation distance inside the inner circle over the total ambulation distance and rearings inside the inner circle over the total rearings in the open field test, and an increase in the time spent in open arms in the elevated plus-maze test. Chronic administration of quetiapine significantly attenuated the dl-amphetamine-induced hyperthermia, and the anxiety-like behavioural changes in the light/dark box and in the open field tests. These results suggest that quetiapine can normalize the dl-amphetamine-induced anxiety-like behavioural changes, and might be helpful in the treatment for amphetamine-induced emotional changes.