Differential Effects of Olanzapine and Haloperidol on MK-801-induced Memory Impairment in Mice

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.

Placental Ferroptosis May Be Involved in Prenatal Arsenic Exposure Induced Cognitive Impairment in Offspring

The association between prenatal arsenic (As) exposure and offspring's cognition is still unclear, and the underlying etiology has also not been elucidated. Based on the Ma'anshan Birth Cohort (MABC) study in China, 1814 mother-child pairs were included in this study, and the association of As levels in cord serum with preschoolers' intelligence scores was explored. To validate the results from population study, in vivo models were adopted to observe the association between prenatal As exposure and spatial learning and memory abilities of mice offsprings. The As-exposure induced ferroptosis in the placenta of human beings as well as C57BL/6 J mice and HTR-8/SVneo cells was explored in order to clarify the potential cause of impairment of offspring's cognition related to As exposure, respectively. In the population study, we observed a significant inverse association between natural logarithm transformed (ln) As levels and preschoolers' intelligence scores, especially for the fluid reasoning index (FRI) [(β (95%CI): - 1.07 (- 1.98, - 0.16)] and working memory index (WMI) [β (95%CI): - 1.51 (- 2.76, - 0.25)]. Meanwhile, the data from in vivo models revealed that the learning and memory abilities of offspring mice decreased after prenatal As exposure. The occurrence of ferroptosis-like characteristics in the placenta and HTR-8/SVneo cells after As exposure was observed, accompanying with evident oxidative stress, iron accumulation, mitochondrial damage, and decreased protein levels of GPX4, xCT, and FTH1 (or FPN1). Notably, the ferroptosis-like alterations induced by NaAsO2 can be effectively alleviated by N-acetylcysteine (NAC) and ferrostatin-1 (Fer-1) treatment in HTR-8/SVneo cells, respectively. In conclusion, prenatal As exposure associates with impairment of offspring's cognition, and placental ferroptosis may be involved in the association. Further studies are needed to confirm the findings.

Social withdrawal and anxiety-like behavior have an impact on zebrafish adult neurogenesis

Introduction

Accumulating evidence highlights the key role of adult neurogenesis events in environmental challenges, cognitive functions and mood regulation. Abnormal hippocampal neurogenesis has been implicated in anxiety-like behaviors and social impairments, but the possible mechanisms remain elusive.

Methods

The present study questioned the contribution of altered excitation/inhibition as well as excessive neuroinflammation in regulating the neurogenic processes within the Social Decision-Making (SDM) network, using an adult zebrafish model displaying NMDA receptor hypofunction after sub-chronic MK-801 administration. For this, the alterations in cell proliferation and newborn cell densities were evaluated using quantitative 5-Bromo-2'-Deoxyuridine (BrdU) methodology.

Results

In short-term survival experiments. MK-801-treated zebrafish displayed decreased cell proliferation pattern within distinct neurogenic zones of telencephalic and preoptic SDM nodes, in parallel to the social withdrawal and anxiety-like comorbidity. BrdU+ cells co-expressed the pro-inflammatory marker IL-1β solely in MK-801-treated zebrafish, indicating a role of inflammation. Following the cessation of drug treatment, significant increases in the BrdU+ cell densities were accompanied by the normalization of the social and anxiety-like phenotype. Importantly, most labeled cells in neurogenic zones showed a radial glial phenotype while a population of newborn cells expressed the early neuronal marker TOAD or mGLuR5, the latter suggesting the possible involvement of metabotropic glutamate receptor 5 in neurogenic events.

Discussion

Overall, our results indicate the role of radial glial cell proliferation in the overlapping pathologies of anxiety and social disorders, observed in many neuropsychiatric disorders and possibly represent potential novel targets for amelioration of these symptoms.

Histone deacetylase 1 regulates haloperidol-induced motor side effects in aged mice

BACKGROUND

Antipsychotic drugs prescribed to elderly patients with neuropsychiatric disorders often experience severe extrapyramidal side effects. Previous studies from our group suggest that changes in histone modifications during aging increase the risk for antipsychotic drug side effects, because co-administration of antipsychotics with class 1 histone deacetylase (HDAC) inhibitors could mitigate the severity of motor side effects in aged mice. However, which HDAC subtype contributes to the age-related sensitivity to antipsychotic drug side effects is unknown.

METHODS

In this study, we overexpressed histone deacetylase type 1(HDAC1) in the striatum of 3-month-old mice and knocked down HDAC 1 in the striatum of 21-month-old mice by microinjection of AAV9-HDAC1-GFP or AAV9-CRISPR/Cas9-HDAC1-GFP vectors. Four weeks after the viral-vector delivery, the typical antipsychotic drug haloperidol was administered daily for 14 days, followed by motor function assessments through the open field, rotarod, and catalepsy behavioral tests.

RESULTS

Young mice with overexpressed HDAC1 showed increased cataleptic behavior induced by haloperidol administration, which is associated with the increased HDAC1 level in the striatum. In contrast, aged mice with HDAC1 knocked down rescued locomotor activity, motor coordination, and decreased cataleptic behavior induced by haloperidol administration, which is associated with decreased HDAC1 level in the striatum.

CONCLUSIONS

Our results suggest that HDAC1 is a critical regulator in haloperidol-induced severe motor side effects in aged mice. Repression of HDAC1 expression in the striatum of aged mice could mitigate typical antipsychotic drug-induced motor side effects.

The Effects of Four Compounds That Act on the Dopaminergic and Serotonergic Systems on Working Memory in Animal Studies; A Literature Review

The dopaminergic and serotonergic systems are two of the most important neuronal pathways in the human brain. Almost all psychotropic medications impact at least one neurotransmitter system. As a result, investigating how they affect memory could yield valuable insights into potential therapeutic applications or unanticipated side effects. The aim of this literature review was to collect literature data from animal studies regarding the effects on memory of four drugs known to act on the serotonergic and dopaminergic systems. The studies included in this review were identified in the PubMed database using selection criteria from the PRISMA protocol. We analyzed 29 articles investigating one of four different dopaminergic or serotonergic compounds. Studies conducted on bromocriptine have shown that stimulating D2 receptors may enhance working memory in rodents, whereas inhibiting these receptors could have the opposite effect, reducing working memory performance. The effects of serotonin on working memory are not clearly established as studies on fluoxetine and ketanserin have yielded conflicting results. Further studies with better-designed methodologies are necessary to explore the impact of compounds that affect both the dopaminergic and serotonergic systems on working memory.

Effects of liraglutide on depressive behavior in a mouse depression model and cognition in the probe trial of Morris water maze test

BACKGROUND

We investigated the effects of liraglutide, a glucagon-like peptide-1 (GLP-1) agonist, on a depression-like phenotype in mice exposed to chronic unpredictable stress (CUS). Learning and memory were also assessed using the Morris water maze (MWM) test.

METHODS

Liraglutide (0.3 mg/kg/day for 21 days) was administered to mice with or without exposure to CUS. After 21 days of CUS, the forced swim test (FST) was performed to assess its antidepressant effect. To evaluate cognitive function, liraglutide was administered to mice under stress-free conditions for 21 days, and then the MWM test was performed on 6 consecutive days.

RESULTS

Chronic liraglutide treatment reduced FST immobility in mice with and without CUS. In the probe trial of the Morris water maze test, the search error rate was reduced and the time spent and path length in the target quadrant and the number of platform crossings were increased.

LIMITATION

Additional animal model experiments and molecular level studies are needed to support the results obtained in this study.

CONCLUSIONS

Liraglutide appears to exert antidepressant effects and could improve cognitive function. Based on these results, GLP-1 agonists could have potential as novel antidepressants.

Prospects for Neurotrophic Factor-Based Early Intervention in Schizophrenia: Lessons Learned from the Effects of Antipsychotic Drugs on Cognition, Neurogenesis, and Neurotrophic Factors

Although reducing psychotic symptoms in schizophrenia has been a major focus of therapeutic interventions for decades, improving cognition is considered a better predictor of functional outcomes. However, the most commonly prescribed antipsychotic drugs (APDs) show only marginal beneficial effects on cognition in patients with schizophrenia. The neural mechanisms underlying cognitive disturbances in schizophrenia remain unknown that making drug development efforts very challenging. Since neurotrophic factors are the primary architects of neurogenesis, synaptic plasticity, learning, and memory, the findings from preclinical and clinical studies that assess changes in neurogenesis and neurotrophic factors and their relationship to cognitive performance in schizophrenia, and how these mechanisms might be impacted by APD treatment, may provide valuable clues in developing therapies to combat cognitive deficit in schizophrenia. Numerous evidence produced over the years suggests a deficit in a wide spectrum of neurotrophic factors in schizophrenia. Since schizophrenia is considered a neurodevelopmental disorder, early intervention with neurotrophic factors may be more effective in ameliorating the cognitive deficits and psychopathological symptoms associated with this pathology. In this context, results from initial clinical trials with neurotrophic factors and their future potential to improve cognition and psychosocial functioning in schizophrenia are discussed.

Effect of Haloperidol and Olanzapine on Hippocampal Cells’ Proliferation in Animal Model of Schizophrenia

Aberrant neurogenesis in the subventricular zone (SVZ) and hippocampus (HIP) contributes to schizophrenia pathogenesis. Haloperidol (HAL) and olanzapine (OLA), commonly prescribed antipsychotics for schizophrenia treatment, affect neurogenesis too. The effect of HAL and OLA on an mHippoE-2 cell line was studied in vitro where we measured the cell number and projection length. In vivo, we studied the gene expression of DCX, Sox2, BDNF, and NeuN in the SVZ and HIP in an MK-801-induced animal schizophrenia model. Cells were incubated with HAL, OLA, and MK-801 for 24, 48, and 72 h. Animals were injected for 6 days with saline or MK801 (0.5 mg/kg), and from the 7th day with either vehicle HAL (1 mg/kg) or OLA (2 mg/kg), for the next 7 days. In vitro, HAL and OLA dose/time-dependently suppressed cells’ proliferation and shortened their projection length. HAL/OLA co-treatment with MK-801 for 24 h reversed HAL’s/OLA’s inhibitory effect. In vivo, HAL and OLA suppressed DCX and NeuN genes’ expression in the HIP and SVZ. MK-801 decreased DCX and NeuN genes’ expression in the HIP and OLA prevented this effect. The data suggest that subchronic HAL/OLA treatment can inhibit DCX and NeuN expression. In an MK-801 schizophrenia model, OLA reversed the MK-801 inhibitory effect on DCX and NeuN and HAL reversed the effect on DCX expression; however, only in the HIP.

Effect of Co-Treatment of Olanzapine with SEP-363856 in Mice Models of Schizophrenia

Olanzapine is a commonly used drug in the treatment of schizophrenia, but its clinical application has been restricted by metabolic-related side effects. In order to mitigate the weight gain side effects caused by olanzapine, other drugs with different targets were selected for combined use and evaluated in animal models of schizophrenia. SEP-363856 is a novel psychotropic agent which is under phase III clinical trials for schizophrenia treatment. The aim of the research was to evaluate whether co-administration of olanzapine and SEP-363856 exerts synergistic anti-schizophrenic effects in the apomorphine (APO)-induced climbing test, the MK-801-induced hyperactivity test, and the Morris water maze test, and therefore reduces the weight gain side effects induced by olanzapine. Through isobolographic analysis, the results showed a synergistic interaction in the climbing test; the experimental ED30 (3 mg/kg) was significantly smaller (p < 0.05) than the theoretical ED30 (5 mg/kg). Additionally, such potentiating effects appeared additive in the MK-801 challenge experiment. Co-treatment with an effective dose of olanzapine and a low dose of SEP-363856 reversed MK-801-induced cognitive impairment symptoms in mice. Moreover, combination treatment with olanzapine and SEP-363856 controls sustained weight gain in mice with chronic exposure to olanzapine. These results support further clinical trials to test the effectiveness of co-treatment of olanzapine and SEP-363856 for controlling symptoms and weight gain in patients with schizophrenia during antipsychotic treatments.

Dose Effects of Histone Deacetylase Inhibitor Tacedinaline (CI-994) on Antipsychotic Haloperidol-Induced Motor and Memory Side Effects in Aged Mice

Background: Elderly patients treated with antipsychotic drugs often experience increased severity and frequency of side effects, yet the mechanisms are not well understood. Studies from our group indicate age-related histone modifications at drug targeted receptor gene promoters may contribute to the increased side effects, and histone deacetylase (HDAC) inhibitors entinostat (MS-275) and valproic acid (VPA) could reverse typical antipsychotic haloperidol (HAL) induced motor-side effects. However, whether such effects could be dose dependent and whether HDAC inhibitors could improve memory function in aged mice is unknown. Methods: We co-treated selective class 1 HDAC inhibitor tacedinaline (CI-994) at different doses (10, 20, and 30 mg/kg) with HAL (0.05 mg/kg) in young (3 months) and aged (21 months) mice for 14 consecutive days, then motor and memory behavioral tests were conducted, followed by biochemical measurements. Results: CI-994 at doses of 10 and 20 mg/kg could decrease HAL-induced cataleptic episodes but only 20 mg/kg was sufficient to improve motor coordination in aged mice. Additionally, CI-994 at 10 and 20 mg/kg mitigate HAL-induced memory impairment in aged mice. Biochemical analyses showed increased acetylation of histone marks H3K27ac and H3K18ac at the dopamine 2 receptor (D2R) gene (Drd2) promoter and increased expression of the Drd2 mRNA and D2R protein in the striatum of aged mice after administration of CI-994 at 20 mg/kg. Conclusions: Our results suggest CI-994 can reduce HAL-induced motor and memory side effects in aged mice. These effects may act through an increase of acetylation at the Drd2 promoter, thereby restoring D2R expression and improving antipsychotic drug action.

Minireview: Animal model of schizophrenia from the perspective of behavioral pharmacology: Effect of treatment on cognitive functions

Schizophrenia is a debilitating mental disorder characterized by positive, negative and cognitive symptoms. Whereas positive symptoms are satisfactorily addressed by current antipsychotic treatment, negative and cognitive symptomatic treatment remains largely ineffective. This review investigates the treatment efficacy regarding cognitive symptoms and evaluates the contribution of different monoamine receptor systems involved in schizophrenia pathophysiology to cognition. In the review, we included preclinical studies assessing the effect of different treatments on cognition in pre-pulse inhibition and two spatial cognitive tests. While pre-pulse inhibition investigates pre-attentive processes operating outside of conscious awareness, the spatial tasks require continuous attention and active engagement in task solving for a successful outcome. The schizophrenia-like phenotype was attained by acute or subchronic administration of non-competitive NMDA receptor antagonist MK-801.

Prediction of Locomotor Activity by Infrared Motion Detector on Sleep-wake State in Mice

Objective

Behavioral assessments that effectively predict sleep-wake states were tried in animal research. This study aimed to examine the prediction power of an infrared locomotion detector on the sleep-wake states in ICR (Institute Cancer Research) mice. We also explored the influence of the durations and ways of data processing on the prediction power.

Methods

The locomotor activities of seven male mice in home cages were recorded by infrared detectors. Their sleep-wake states were assessed by video analysis. Using the receiver operating characteristic curve analysis, the cut-off score was determined, then the area under the curve (AUC) values of the infrared motion detector that predicted sleep-wake states were calculated. In order to improve the prediction power, the four ways of data processing on the prediction power were performed by Matlab 2013b.

Results

In the initial analysis of raw data, the AUC value was 0.785, but it gradually reached to 0.942 after data summation. The simple data averaging and summation among four different methods showed the maximal AUC value. The 10-minute data summation improved sensitivity (0.889) and specificity (0.901) significantly from the baseline value (sensitivity 0.615; specificity 0.936) (p < 0.001).

Conclusion

This study suggests that the locomotor activity measured by an infrared motion detector might be useful to predict the sleep-wake states in ICR mice. It also revealed that only simple data summation may improve the predictive power. Using daily locomotor activities measured by an infrared motion detector is expected to facilitate animal research related to sleep-wake states.

Olanzapine Increases Neural Chemorepulsant-Draxin Expression in the Adult Rat Hippocampus

Draxin belongs to the family of inhibitory axon-guiding factors that regulate neuronal migration and axonal spreading in the developing brain. This glycoprotein has recently been considered to play an important role both in hippocampal differentiation and adult neurogenesis in the dentate gyrus. Given that it has been reported that antipsychotic drugs may affect neurite growth and neurogenesis, we have therefore investigated whether chronic treatment with olanzapine modulates draxin immunoreactivity in the adult rat hippocampus. After analysis of local fluorescence intensity, we found a significant increase of draxin immunoexpression both in the subgranular zone (SGZ) and granular zone of the rat hippocampus following long-term olanzapine administration. This study reveals, for the first time, the modulatory effect of the atypical antipsychotic medication olanzapine on expression of the novel chemorepulsive protein draxin in the context of adult neurogenesis regulation. Moreover, this is the first report dealing with pharmacological aspects of draxin signaling. An elevated draxin expression may indirectly support a recently formulated hypothesis that olanzapine may drive adult neurogenesis via paracrine draxin-related signaling. This action of draxin is a new element in the neurogenesis mechanism that may be part of the action of second-generation antipsychotics in the treatment of schizophrenia, indicating more detailed molecular studies are urgently required to fully investigate these potential novel mechanisms of neurogenesis.

N-(3-{4-[3-(trifluoromethyl)phenyl]piperazin-1-yl}propyl)-1H-indazole-3-carboxamide (D2AAK3) as a potential antipsychotic: In vitro, in silico and in vivo evaluation of a multi-target ligand

Schizophrenia is a mental illness of not adequately understood causes that is not satisfactorily enough treated by current antipsychotics. In search for novel potential antipsychotics we performed structure-based virtual screening aimed to identify new dopamine D₂ receptor antagonists. We found compound D2AAK3 with affinity to dopamine D₂ receptor of 115 nM. D2AAK3 possesses additional nanomolar or low micromolar affinity to D₁, D₃, 5-HT_1A, 5-HT_2A and 5-HT₇ receptors, which makes it a good hit for further development as a multifunctional ligand. The compound has also some affinity to M₁ and H₁ receptors. We used homology modeling, molecular docking and molecular dynamics to study interactions of D2AAK3 with its molecular targets at the molecular level. In behavioral studies D2AAK3 decreases amphetamine-induced hyperactivity (when compared to the amphetamine-treated group) measured as spontaneous locomotor activity in mice. In addition, passive avoidance test demonstrated that D2AAK3 improves memory consolidation after acute treatment in mice. Elevated plus maze tests indicated that D2AAK3 induces anxiogenic activity 30 min after acute treatment, whereas this effect has no longer been observed 60 min after administration of the studied compound in mice.

Olanzapine attenuates postoperative cognitive dysfunction in adult rats

Background

Postoperative cognitive dysfunction (POCD) is associated with poor quality of life and difficulty working. Its impact may be greater in middle-aged patients than in elderly patients. Neuroinflammation is reported to be a main cause of POCD. Olanzapine has been reported to improve learning and memory functions. We therefore investigated olanzapine's effectiveness and mechanisms in an adult rat POCD model.

Methods

Six-month-old rats underwent laparotomy and lipopolysaccharide (LPS group) or LPS + olanzapine (OLA group) intraperitoneal injection or anesthesia alone (CON group) 1 week after a Barnes maze training session. A Barnes maze test trial was then conducted the day after surgery or anesthesia. The microglial activity in the hippocampus and cytokine levels were measured by Iba1 staining and enzyme-linked immunosorbent assay, respectively.

Results

The OLA group had significantly higher success rates of Barnes maze trial than the LPS group. The success rate in time of the OLA group was inferior to that of the CON group. On the other hand, the success rate in distance of the OLA group was similar to that of the CON group. Iba1 staining areas in the LPS and OLA groups were larger than that in the CON group; however, the staining area in the OLA group was smaller than that of the LPS group. Plasma interleukin-1β concentration in the LPS and OLA groups was significantly higher than that in the CON group; however, there was no significant difference between the LPS and OLA groups.

Conclusion

Olanzapine attenuated both spatial cognitive dysfunction and microglial activity of the hippocampus, which were induced by surgery and LPS injection. These effects were unrelated to inflammatory cytokine concentrations in plasma and hippocampus.

Contributions of animal models of cognitive disorders to neuropsychopharmacology

Cognitive disorders and symptoms are key features of many mental and neurological diseases, with a large spectrum of impaired domains. Because of their possible evolution and detrimental functioning impact, they are a major pharmacological target for both symptomatic and disease-modifier drugs, while few cognitive enhancers have been marketed with an insufficient efficiency. It explains the need to model these cognitive disorders beyond the modelization of mental or neurological diseases themselves. According to the experimental strategy used to induce cognitive impairment, three categories of models have been identified: neurotransmission-driven models; pathophysiology-driven models; environment-driven models. These three categories of models reflect different levels of integration of endogenous and exogenous mechanisms underlying cognitive disorders in humans. Their comprehensive knowledge and illustration of their pharmacological modulation could help to propose a renewing strategy of drug development in central nervous system (CNS) field at a time when the academic and industrial invest seems to be declining despite the medical and social burden of brain diseases.

Antipsychotic Drugs Reverse MK801-Inhibited Cell Migration and F-actin Condensation by Modulating the Rho Signaling Pathway in B35 Cells

Background and Aim. MK801-induced psychotic symptoms and also the Ras homolog family member A (RhoA) expression and cell division control protein 42 (cdc42) mRNA modulation in the rat brain have been investigated. Antipsychotic drugs (APDs) have been reported to induce Rho GDP-dissociation inhibitor (RhoGDI) pathway regulation related to cytoskeleton reorganization in neuronal cells. It will be necessary to clarify the effects of APDs on MK801-induced RhoGDI signaling regulation in neuronal cells. Methods. B35 neuronal cells were treated with MK801 for 7 days then treated with MK801 in combination with haloperidol or clozapine for a further 7 days. Cell migration, F-actin condensation, and RhoGDI signaling regulation were examined to investigate the regulatory effects of MK801, haloperidol, and clozapine in B35 neuronal cells. Results. MK801 reduced B35 cell migration, whereas both haloperidol and clozapine reversed the reduction in cell migration induced by MK801. Haloperidol and clozapine restored F-actin condensation after it was diminished by MK801 in B35 cell nuclei. MK801 increased the RhoGDI1 and RhoA expression, which was diminished by the addition of haloperidol and clozapine. MK801 reduced the CDC42 expression, which was restored by haloperidol and clozapine. MK801 reduced the Rho-associated coiled-coil containing protein kinase 1 (ROCK1), profilin1 (PFN1), and neuronal Wiskott–Aldrich Syndrome protein (N-WASP) expression, which was further reduced by haloperidol and clozapine. MK801 also increased the phosphorylated myosin light chain 2 (p-MLC2), postsynaptic density protein 95 (PSD-95), and c-jun expression, which was decreased by haloperidol and clozapine. p21 (RAC1-) activated kinase 1 (PAK1) expression was not affected by MK801.

Effect of NMDAR-NMNAT1/2 pathway on neuronal cell damage and cognitive impairment of sevoflurane-induced aged rats

Objective: The possible effect of NMDAR (N-methyl-D-aspartate receptor)-NMNAT1/2 (nicotinamide/nicotinic acid mono-nucleotide adenylyltransferase) signaling pathway on the neuronal cell damage and cognitive impairment of aged rats anesthetized by sevoflurane was explored.Methods: Adult male Wistar rats were selected and divided into Control, Sevo (Sevoflurane), Sevo+DCS (NMDAR agonist D-cycloserine) 30 mg/kg, Sevo+DCS 100 mg/kg, and Sevo+DCS 200 mg/kg groups. Morris water maze and fear conditioning text were used to observe cognitive function changes of rats. The inflammatory cytokines were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) assay, neuronal apoptosis by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) staining and MDAR-NMNAT1/2 pathway-related proteins by Western blotting.Results: The longer escape latency, decreased platform crossing times and reduced staying time spent in platform quadrant were found in rats from Sevo group, with decreased percentage of freezing time in contextual test and tone cued test; and meanwhile, these rats had increased inflammatory cytokines (interleukin (IL)-1β, tumor necrosis factor (TNF-α), IL-6, and IL-8) and neuronal apoptosis, but declined expressions of MDAR-NMNAT1/2 pathway-related proteins. However, the above changes were exhibited an opposite tendency in those Sevo rats treated with different concentrations of DCS (including 30, 100, and 200 mg/kg, respectively). Particularly, the improving effect of low-dose DCS on each aspect in aged rats was better than high-dose ones.Conclusion: Activation of NMDAR-NMNAT1/2 signaling pathway could not only reduce neuronal apoptosis, but also alleviate sevoflurane-induced neuronal inflammation and cognitive impairment in aged rats.

Risperidone Reverses the Downregulation of BDNF in Hippocampal Neurons and MK801-Induced Cognitive Impairment in Rats

MK-801, also known as dizocilpine, is a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist that induces schizophrenia-like symptoms. Our previous study showed that brain-derived neurotrophic factor (BDNF) signaling was upregulated in cultured hippocampal astrocytes in response to MK-801. However, dysfunctional NMDA receptors are mainly expressed in neurons. The effects of MK-801 on neuron-derived BDNF expression and of risperidone on MK-801-induced cognitive impairment and changes in BDNF expression are unclear. To address this issue, we examined BDNF expression in the hippocampus of rats that received repeated injections of MK-801 (0.5 mg/kg body weight for 6 days) and in primary cultured hippocampal neurons incubated with 20 μM MK-801 for 24 h. BDNF expression and cognitive function were also evaluated in rats receiving intraperitoneal injections of risperidone (1 mg/kg body weight) once daily for 7 days and in hippocampal neurons incubated with 10 μM risperidone following MK801 treatment. MK-801 treatment decreased BDNF expression in the rat hippocampus as well as the expression and secretion of BDNF in hippocampal neurons in vitro. However, risperidone reversed the effects of MK801 on BDNF level and improved cognitive function in rats treated with MK801. These findings suggest that risperidone may alleviate cognitive impairment caused by MK801 via upregulation of BNDF signaling in the hippocampus.

Effects of Tianeptine on Adult Rats Following Prenatal Stress

Objective

Exposing a pregnant female to stress during the critical period of embryonic fetal brain development increases the risk of psychiatric disorders in the offspring. The objective of this study was to investigate the effect of antidepressant tianeptine on prenatally stressed (PNS) rats.

Methods

In this study, a repeated variable stress paradigm was applied to pregnant rats during the last week of gestation. To investigate the effects of antidepressant tianeptine on PNS rats, behavioral and protein expression analyses were performed. Forced swim test, open field test, and social interaction test were performed to determine changes in PNS rats compared to non-stressed offspring. Haloperidol was used as a positive control as an antipsychotic drug based on previous studies.

Results

Behavioral changes were restored after treatment with tianeptine or haloperidol. Western blot and immunohistochemical analyses of the prefrontal cortex revealed downregulation of several neurodevelopmental proteins in PNS rats. After treatment with tianeptine or haloperidol, their expression levels were increased.

Conclusion

Downregulation of several proteins in PNS rats might have caused subsequent behavioral changes in PNS rats. After tianeptine or haloperidol treatment, behavioral changes in PNS rats were restored. Therefore, tianeptine might decrease incidence of prenatal stress related-psychiatric disorders such as depression and schizophrenia.

The Memory-Enhancing Effects of Liquiritigenin by Activation of NMDA Receptors and the CREB Signaling Pathway in Mice

Liquiritigenin (LQ) is a flavonoid that can be isolated from Glycyrrhiza radix. It is frequently used as a tranditional oriental medicine herbal treatment for swelling and injury and for detoxification. However, the effects of LQ on cognitive function have not been fully explored. In this study, we evaluated the memory-enhancing effects of LQ and the underlying mechanisms with a focus on the N-methyl-D-aspartic acid receptor (NMDAR) in mice. Learning and memory ability were evaluated with the Y-maze and passive avoidance tests following administration of LQ. In addition, the expression of NMDAR subunits 1, 2A, and 2B; postsynaptic density-95 (PSD-95); phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII); phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2); and phosphorylation of cAMP response element binding (CREB) proteins were examined by Western blot. In vivo, we found that treatment with LQ significantly improved memory performance in both behavioral tests. In vitro, LQ significantly increased NMDARs in the hippocampus. Furthermore, LQ significantly increased PSD-95 expression as well as CaMKII, ERK, and CREB phosphorylation in the hippocampus. Taken together, our results suggest that LQ has cognition enhancing activities and that these effects are mediated, in part, by activation of the NMDAR and CREB signaling pathways.

Olanzapine Reverses MK-801-Induced Cognitive Deficits and Region-Specific Alterations of NMDA Receptor Subunits

Cognitive dysfunction constitutes an essential component in schizophrenia for its early presence in the pathophysiology of the disease and close relatedness to life quality of patients. To develop effective treatment of cognitive deficits, it is important to understand their neurobiological causes and to identify potential therapeutic targets. In this study, adopting repeated MK-801 treatment as an animal model of schizophrenia, we investigated whether antipsychotic drugs, olanzapine and haloperidol, can reverse MK-801-induced cognitive deficits and how the reversal processes recruited proteins involved in glutamate neurotransmission in rat medial prefrontal cortex (mPFC) and hippocampus. We found that low-dose chronic MK-801 treatment impaired object-in-context recognition memory and reversal learning in the Morris water maze, leaving reference memory relatively unaffected, and that these cognitive deficits can be partially reversed by olanzapine, not haloperidol, treatment. At the molecular level, chronic MK-801 treatment resulted in the reduction of multiple N-methyl-D-aspartate (NMDA) receptor subunits in rat mPFC and olanzapine, not haloperidol, treatment restored the levels of GluN1 and phosphorylated GluN2B in this region. Taken together, MK-801-induced cognitive deficits may be associated with region-specific changes in NMDA receptor subunits and the reversal of specific NMDA receptor subunits may underlie the cognition-enhancing effects of olanzapine.

Inhalation Toxicity of Bisphenol A and Its Effect on Estrous Cycle, Spatial Learning, and Memory in Rats upon Whole-Body Exposure

Bisphenol A (BPA) is a monomer used in a polymerization reaction in the production of polycarbonate plastics. It has been used in many consumer products, including plastics, polyvinyl chloride, food packaging, dental sealants, and thermal receipts. However, there is little information available on the inhalation toxicity of BPA. Therefore, the aim of this study was to determine its inhalation toxicity and effects on the estrous cycle, spatial learning, and memory. Sprague-Dawley rats were exposed to 0, 10, 30, and 90 mg/m³ BPA, 6 hr/day, 5 days/week for 8 weeks via whole-body inhalation. Mortality, clinical signs, body weight, hematology, serum chemistry, estrous cycle parameters, performance in the Morris water maze test, and organ weights, as well as gross and histopathological findings, were compared between the control and BPA exposure groups. Statistically significant changes were observed in serum chemistry and organ weights upon exposure to BPA. However, there was no BPA-related toxic effect on the body weight, food consumption, hematology, serum chemistry, organ weights, estrous cycle, performance in the Morris water maze test, or gross or histopathological lesions in any male or female rats in the BPA exposure groups. In conclusion, the results of this study suggested that the no observable adverse effect level (NOAEL) for BPA in rats is above 90 mg/m³/6 hr/day, 5 days/week upon 8-week exposure. Furthermore, BPA did not affect the estrous cycle, spatial learning, or memory in rats.