Treatment with levetiracetam improves cognition in a ketamine rat model of schizophrenia

Fractional amplitude of low-frequency fluctuations in sensory-motor networks and limbic system as a potential predictor of treatment response in patients with schizophrenia

BACKGROUND

Previous investigations have revealed substantial differences in neuroimaging characteristics between healthy controls (HCs) and individuals diagnosed with schizophrenia (SCZ). However, we are not entirely sure how brain activity links to symptoms in schizophrenia, and there is a need for reliable brain imaging markers for treatment prediction.

METHODS

In this longitudinal study, we examined 56 individuals diagnosed with 56 SCZ and 51 HCs. The SCZ patients underwent a three-month course of antipsychotic treatment. We employed resting-state functional magnetic resonance imaging (fMRI) along with fractional Amplitude of Low Frequency Fluctuations (fALFF) and support vector regression (SVR) methods for data acquisition and subsequent analysis.

RESULTS

In this study, we initially noted lower fALFF values in the right postcentral/precentral gyrus and left postcentral gyrus, coupled with higher fALFF values in the left hippocampus and right putamen in SCZ patients compared to the HCs at baseline. However, when comparing fALFF values in brain regions with abnormal baseline fALFF values for SCZ patients who completed the follow-up, no significant differences in fALFF values were observed after 3 months of treatment compared to baseline data. The fALFF values in the right postcentral/precentral gyrus and left postcentral gyrus, and the left postcentral gyrus were useful in predicting treatment effects.

CONCLUSION

Our findings suggest that reduced fALFF values in the sensory-motor networks and increased fALFF values in the limbic system may constitute distinctive neurobiological features in SCZ patients. These findings may serve as potential neuroimaging markers for the prognosis of SCZ patients.

Modulation of hippocampal activity in schizophrenia with levetiracetam: a randomized, double-blind, cross-over, placebo-controlled trial

Hippocampal hyperactivity is a novel pharmacological target in the treatment of schizophrenia. We hypothesized that levetiracetam (LEV), a drug binding to the synaptic vesicle glycoprotein 2 A, normalizes hippocampal activity in persons with schizophrenia and can be measured using neuroimaging methods. Thirty healthy control participants and 30 patients with schizophrenia (28 treated with antipsychotic drugs), were randomly assigned to a double-blind, cross-over trial to receive a single administration of 500 mg oral LEV or placebo during two study visits. At each visit, we assessed hippocampal function using resting state fractional amplitude of low frequency fluctuations (fALFF), cerebral blood flow (CBF) with arterial spin labeling, and hippocampal blood-oxygen-level-dependent (BOLD) signal during a scene processing task. After placebo treatment, we found significant elevations in hippocampal fALFF in patients with schizophrenia, consistent with hippocampal hyperactivity. Additionally, hippocampal fALFF in patients with schizophrenia after LEV treatment did not significantly differ from healthy control participants receiving placebo, suggesting that LEV may normalize hippocampal hyperactivity. In contrast to our fALFF findings, we did not detect significant group differences or an effect of LEV treatment on hippocampal CBF. In the context of no significant group difference in BOLD signal, we found that hippocampal recruitment during scene processing is enhanced by LEV more significantly in schizophrenia. We conclude that pharmacological modulation of hippocampal hyperactivity in schizophrenia can be studied with some neuroimaging methods, but not others. Additional studies in different cohorts, employing alternate neuroimaging methods and study designs, are needed to establish levetiracetam as a treatment for schizophrenia.

Influence of the dose of ketamine used on schizophrenia-like symptoms in mice: A correlation study with TH, GAD67, and PPAR-γ

Schizophrenia is a chronic, debilitating mental illness that has not yet been completely understood. In this study, we aimed to investigate the effects of different doses of ketamine, a non-competitive NMDA receptor antagonist, on the positive- and negative-like symptoms of schizophrenia. We also explored whether these effects are related to changes in the immunoreactivity of GAD67, TH, and PPAR-γ in brain structures. To conduct the study, male mice received ketamine (20-40 mg/kg) or its vehicle (0.9 % NaCl) intraperitoneally for 14 consecutive days. We quantified stereotyped behavior, the time of immobility in the forced swimming test (FST), and locomotor activity after 7 or 14 days. In addition, we performed ex vivo analysis of the immunoreactivity of GAD, TH, and PPAR-γ, in brain tissues after 14 days. The results showed that ketamine administration for 14 days increased the grooming time in the nose region at all tested doses. It also increased immobility in the FST at 30 mg/kg doses and decreased the number of rearing cycles during stereotyped behavior at 40 mg/kg. These behavioral effects were not associated with changes in locomotor activity. We did not observe any significant alterations regarding the immunoreactivity of brain proteins. However, we found that GAD and TH were positively correlated with the number of rearing during the stereotyped behavior at doses of 20 and 30 mg/kg ketamine, respectively. GAD was positively correlated with the number of rearing in the open field test at a dose of 20 mg/kg. TH was inversely correlated with immobility time in the FST at a dose of 30 mg/kg. PPAR-γ was inversely correlated with the number of bouts of stereotyped behavior at a dose of 40 mg/kg of ketamine. In conclusion, the behavioral alterations induced by ketamine in positive-like symptoms were reproduced with all doses tested and appear to depend on the modulatory effects of TH, GAD, and PPAR-γ. Conversely, negative-like symptoms were associated with a specific dose of ketamine.

Impact of levetiracetam on cognitive impairment, neuroinflammation, oxidative stress, and neuronal apoptosis caused by lipopolysaccharides in rats

Introduction

Neuroinflammation is associated with the elevation of toxic proinflammatory mediators that promote neurodegeneration and subsequently affect cognition. Causes of inflammation in the neuronal cells are believed to initiate various neurodegenerative disorders, mainly Alzheimer's disease. Levetiracetam is a second-generation antiepileptic drug. There is evidence supporting the memory-enhancing effect of levetiracetam from numerous experimental and clinical studies. Therefore, this research focused on finding its protective effects against lipopolysaccharides prompted cognitive impairment and exploring possible mechanisms underlining their neuroprotection.

Methodology

Two doses (100 or 200 mg/kg) of levetiracetam were administrated orally for 30 days. Additionally, four doses (250 µg/kg) of lipopolysaccharide were injected peripherally to induce neurotoxicity. Behavioral tests were carried out using various maze models. At the end of the tests, brain tissues were collected for biochemical evaluations. Cholinergic, neuroinflammatory, apoptosis, and oxidative-related parameters were analyzed in the brain homogenate to explore the possible mechanisms of action of levetiracetam.

Results

In lipopolysaccharide-induced rats, levetiracetam indicated a reduction (p < 0.01) in transfer latency using the elevated plus-maze. An improvement (p < 0.01) in novel and familiar objects exploration time using novel object recognition test. A rise (p < 0.05) in novel arm entries and extended time spent in the novel arm using the Y-maze test. In extension, the levels of acetylcholine (p < 0.001), anti-inflammatory factors (transforming growth factor-β1; p < 0.01 and interleukin-10; p < 0.05), and an antioxidant (catalase; p < 0.01) were elevated in lipopolysaccharide-induced rats after the administration of levetiracetam. In contrast, inflammatory factors (cyclooxygenase-2; p < 0.05, nuclear factor kappa B; p < 0.05, tumor necrosis factor-α; p < 0.01, and interleukin-6 (p < 0.01), apoptosis inducers (BCL2-associated X protein; p < 0.05 and Caspase-3 (p < 0.001), and oxidative stress (malondialdehyde; p < 0.05) were considerably reduced with levetiracetam in lipopolysaccharide-induced rats.

Conclusion

The collective results suggested that levetiracetam may be able to treat neuroinflammatory-related memory loss by enhancing cholinergic activity while reducing neuroinflammation, cellular apoptosis, and oxidative stress.

Levetiracetam Attenuates Adolescent Stress-induced Behavioral and Electrophysiological Changes Associated With Schizophrenia in Adult Rats

BACKGROUND AND HYPOTHESIS

Stress during adolescence is a major risk factor for schizophrenia. We have found previously in rats that adolescent stress caused, in adulthood, behavioral changes and enhanced ventral tegmental area (VTA) dopamine system activity, which were associated with dysregulation of the excitatory-inhibitory (E/I) balance in the ventral hippocampus (vHip). Levetiracetam, an anticonvulsant drug, regulates the release of neurotransmitters, including glutamate, via SV2A inhibition. It also modulates parvalbumin interneuron activity via Kv3.1 channels. Therefore, levetiracetam could ameliorate deficits in the E/I balance. We tested whether levetiracetam attenuate the adolescent stress-induced behavioral changes, vHip hyperactivity, and enhanced VTA dopamine system activity in adult rats.

STUDY DESIGN

Male Sprague-Dawley rats were subjected to a combination of daily footshock (postnatal day [PD] 31-40), and three 1 h-restraint stress sessions (at PD31, 32, and 40). In adulthood (PD62), animals were tested for anxiety responses (elevated plus-maze and light-dark box), social interaction, and cognitive function (novel object recognition test). The activity of vHip pyramidal neurons and VTA dopamine neurons was also recorded.

STUDY RESULTS

Adolescent stress produced anxiety-like responses and impaired sociability and cognitive function. Levetiracetam (10 mg/kg) reversed these changes. Levetiracetam also reversed the increased VTA dopamine neuron population activity and the enhanced firing rate of vHip pyramidal neurons induced by adolescent stress.

CONCLUSIONS

These findings suggest that levetiracetam attenuates the adverse outcomes associated with schizophrenia caused by stress during adolescence.

Levetiracetam Ameliorates Doxorubicin-Induced Chemobrain by Enhancing Cholinergic Transmission and Reducing Neuroinflammation Using an Experimental Rat Model and Molecular Docking Study

Cancer chemotherapy-induced cognitive impairment (chemobrain) is a major complication that affects the prognosis of therapy. Our study evaluates the nootropic-like activity of levetiracetam (LEVE) against doxorubicin (DOX)-induced memory defects using in vivo and molecular modelling. Rats were treated with LEVE (100 and 200 mg/kg, 30 days) and chemobrain was induced by four doses of DOX (2 mg/kg, i.p.). Spatial memory parameters were evaluated using an elevated plus maze (EPM) and Y-maze. Additionally, acetylcholinesterase (AChE) and the neuroinflammatory biomarkers cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), nuclear factor-κB (NF-κB), and tumor necrosis factor-alpha (TNF-α) were analyzed using brain homogenate. PharmMapper was used for inverse docking and AutoDock Vina was used for molecular docking. LEVE treatment significantly diminished the DOX-induced memory impairment parameters in both the EPM and Y-maze. In addition, the drug treatment significantly reduced AChE, COX-2, PGE2, NF-κB, and TNF-α levels compared to DOX-treated animals. The inverse docking procedures resulted in the identification of AChE as the potential target. Further molecular modelling studies displayed interactions with residues Gly118, Gly119, and Ser200, critical for the hydrolysis of ACh. Analysis of the results suggested that administration of LEVE improved memory-related parameters in DOX-induced animals. The ‘nootropic-like’ activity could be related to diminished AChE and neuroinflammatory mediator levels.

Can levetiracetam improve clinical symptoms in schizophrenic patients? A randomized placebo-controlled clinical trial

INTRODUCTION

Schizophrenia is associated with persistent cognitive deficits, which worsen treatment outcomes despite increasing antipsychotic doses. This study aimed to assess the effect of levetiracetam on the severity of schizophrenia symptoms and cognitive deficits in these patients.

MATERIALS AND METHODS

In this randomized, controlled, three-blind randomized clinical trial approved by Mashhad University of Medical Sciences, Iran (IRCT20101130005280N31), forty chronic schizophrenic patients aged 18-60 years were randomly divided into two groups of levetiracetam and placebo. The levetiracetam group received levetiracetam for 8 weeks. The symptoms were evaluated by Positive and Negative Symptoms Scale (PANSS), Stroop test, Digit Span test and Wisconsin Test at baseline, 4th week, and 8th week. Data were analyzed through SPSS V. 23 software, descriptive tests and inferential statistics.

RESULTS

At the end of the study, all subscales of the PANSS questionnaire reduced significantly (P < 0.05). Also, all subscales of the cognitive tests had significant changes. The trends of digit span tests, correct number of consonants and inconsonant were increasing. While the trends related to consonant errors, inconsistent errors, consistent reaction time and nonconsistent reaction time were decreasing. The changes in the number of classes were increased while changes in preservation error were decreased.

CONCLUSION

The results showed that levetiracetam has significant effects on clinical symptoms, especially negative symptoms. Also, it impacts significantly on cognitive functions. It is recommended that it be added to the pharmacological regimen of these patients to improve their clinical symptoms, quality of life and treatment outcomes.

Increased amplitude of hippocampal low frequency fluctuations in early psychosis: A two-year follow-up study

Neuroimaging studies have revealed hippocampal hyperactivity in schizophrenia. In the early stage of the illness, hyperactivity is present in the anterior hippocampus and is thought to spread to other regions as the illness progresses. However, there is limited evidence for changes in basal hippocampal function following the onset of psychosis. Resting state functional MRI signal amplitude may be a proxy measure for increased metabolism and disrupted oscillatory activity, both consequences of an excitation/inhibition imbalance underlying hippocampal hyperactivity. Here, we used fractional amplitude of low frequency fluctuations (fALFF) to test the hypothesis of progressive hippocampal hyperactivity in a two-year longitudinal case-control study. We found higher fALFF in the anterior and posterior hippocampus of individuals in the early stage of non-affective psychosis at study entry. Contrary to our hypothesis of progressive hippocampal dysfunction, we found evidence for normalization of fALFF over time in psychosis. Our findings support a model in which hippocampal fALFF is a marker of psychosis vulnerability or acute illness state rather than an enduring feature of the illness.

Effects of clozapine and risperidone antipsychotic drugs on the expression of CACNA1C and behavioral changes in rat 'Ketamine model of schizophrenia

Calcium Voltage-Gated Channel Subunit Alpha1 C (CACNA1C) is one of the most important genes associated with schizophrenia. In this study, 45 male Wistar rats were divided into 5 groups of saline, control, ketamine, clozapine, and risperidone. Animals in ketamine, risperidone, and clozapine groups received ketamine (30 mg/kg-i.p.) for 10 days. After the last injection of ketamine, we started injecting clozapine (7.5 mg/kg-i.p.), risperidone (1 mg/kg-i.p.), up to 28 days. Twenty-four hours after the last injection, open field, social interaction, and elevated plus-maze tests and gene expression in hippocampus were performed. The results of the social interaction test revealed a significant decrease in cumulative time with ketamine, compared with the saline group, and an increase with clozapine and risperidone compared with the ketamine group. Moreover, results from the elevated plus-maze test demonstrated a critical decrease in open arm time and increase in close arm time with ketamine compared with saline, as well as increased in open arm time with risperidone compared with ketamine. Further results revealed a significant increase in rearing and grooming with ketamine compared to saline, as well as a decrease with risperidone and clozapine compared to ketamine. There were no significant differences in CACNA1C gene expression between groups in the rat hippocampus. In brief, the results of this study indicated that clozapine and risperidone could partially improve cognitive impairments in the rat. However, our findings demonstrated that this treatment is not related to CACNA1C gene expression.

(R,S)-ketamine and (2R,6R)-hydroxynorketamine differentially affect memory as a function of dosing frequency

A single subanesthetic infusion of ketamine can rapidly alleviate symptoms of treatment-resistant major depression. Since repeated administration is required to sustain symptom remission, it is important to characterize the potential untoward effects of prolonged ketamine exposure. While studies suggest that ketamine can alter cognitive function, it is unclear to what extent these effects are modulated by the frequency or chronicity of treatment. To test this, male and female adolescent (postnatal day [PD] 35) and adult (PD 60) BALB/c mice were treated for four consecutive weeks, either daily or thrice-weekly, with (R,S)-ketamine (30 mg/kg, intraperitoneal) or its biologically active metabolite, (2R,6R)-hydroxynorketamine (HNK; 30 mg/kg, intraperitoneal). Following drug cessation, memory performance was assessed in three operationally distinct tasks: (1) novel object recognition to assess explicit memory, (2) Y-maze to assess working memory, and (3) passive avoidance to assess implicit memory. While drug exposure did not influence working memory performance, thrice-weekly ketamine and daily (2R,6R)-HNK led to explicit memory impairment in novel object recognition independent of sex or age of exposure. Daily (2R,6R)-HNK impaired implicit memory in the passive-avoidance task whereas thrice-weekly (2R,6R)-HNK tended to improve it. These differential effects on explicit and implicit memory possibly reflect the unique mechanisms by which ketamine and (2R,6R)-HNK alter the functional integrity of neural circuits that subserve these distinct cognitive domains, a topic of clinical and mechanistic relevance to their antidepressant actions. Our findings also provide additional support for the importance of dosing frequency in establishing the cognitive effects of repeated ketamine exposure.

Using internal memory representations in associative learning to study hallucination-like phenomenon

Studies of Pavlovian conditioning have enriched our understanding of how relations among events can adaptively guide behavior through the formation and use of internal mental representations. In this review, we illustrate how internal representations flexibly integrate new updated information in reinforcer revaluation to influence relationships to impact actions and outcomes. We highlight representation-mediated learning to show the similarities in properties and functions between internally generated and directly activated representations, and how normal perception of internal representations could contribute to hallucinations. Converging evidence emerges from recent behavioral and neural activation studies using animal models of schizophrenia as well as clinical studies in patients to support increased tendencies in these populations to evoke internal representations from prior associative experience that approximate hallucination-like percepts. The heightened propensity is dependent on dopaminergic activation which is known to be sensitive to hippocampal overexcitability, a condition that has been observed in patients with psychosis. This presents a network that overlaps with cognitive neural circuits and offers a fresh approach for the development of therapeutic interventions targeting psychosis.

Inhibiting Epileptiform Activity in Cognitive Disorders: Possibilities for a Novel Therapeutic Approach

Cognitive impairment is a common and seriously debilitating symptom of various mental and neurological disorders including autism, attention deficit hyperactivity disorder, multiple sclerosis, epilepsy, and neurodegenerative diseases, like Alzheimer's disease. In these conditions, high prevalence of epileptiform activity emerges as a common pathophysiological hallmark. Growing body of evidence suggests that this discrete but abnormal activity might have a long-term negative impact on cognitive performance due to neuronal circuitries' remodeling, altered sleep structure, pathological hippocampo-cortical coupling, and even progressive neuronal loss. In animal models, epileptiform activity was shown to enhance the formation of pathological amyloid and tau proteins that in turn trigger network hyperexcitability. Abolishing epileptiform discharges might slow down the cognitive deterioration. These findings might provide basis for therapeutic use of antiepileptic drugs in neurodegenerative cognitive disorders. The aim of our review is to describe the data on the prevalence of epileptiform activity in various cognitive disorders, to summarize the current knowledge of the mechanisms of epileptic activity in relation to cognitive impairment, and to explore the utility of antiepileptic drugs in the therapy of cognitive disorders. We also propose future directions for drug development and novel therapeutic interventions targeting epileptiform discharges in these disorders.

Levetiracetam induction of theta frequency oscillations in rodent hippocampus in vitro

Levetiracetam (LEV) has been demonstrated to improve cognitive function. Hippocampal theta rhythm (4-12 Hz) is associated with a variety of cognitively related behaviors, such as exploration in both humans and animal models. We investigated the effects of LEV on the theta rhythm in the rat hippocampal CA3 in hippocampal slices in vitro. We found that LEV increased the theta power in a dose-dependent manner. The increase in theta power can be blocked by GABA_A receptor (GABA_AR) or NMDA receptor (NMDAR) antagonists but not by AMPA receptor antagonist, indicating the involvement of GABA_AR and NMDAR in the induction of theta activity. Interestingly, LEV enhancement of theta power can be also blocked by taurine or GABA-A agonist THIP, indicating that LEV induction of theta may be related to the indirect boosting of GABA action via reduction of extrasynaptic GABA_AR activation. Furthermore, the increased theta power can be partially reduced by the mACh receptor (mAChR) antagonist atropine but not by nACh receptor antagonists, suggesting that mAChR activation provides excitatory input into local network responsible for LEV-induced theta. Our study demonstrated that LEV induced a novel theta oscillation in vitro, which may have implications in the treatment of the neuronal disorders with impaired theta oscillation and cognitive function.

Drug repositioning for psychiatric and neurological disorders through a network medicine approach

Psychiatric and neurological disorders (PNDs) affect millions worldwide and only a few drugs achieve complete therapeutic success in the treatment of these disorders. Due to the high cost of developing novel drugs, drug repositioning represents a promising alternative method of treatment. In this manuscript, we used a network medicine approach to investigate the molecular characteristics of PNDs and identify novel drug candidates for repositioning. Using IBM Watson for Drug Discovery, a powerful machine learning text-mining application, we built knowledge networks containing connections between PNDs and genes or drugs mentioned in the scientific literature published in the past 50 years. This approach revealed several drugs that target key PND-related genes, which have never been used to treat these disorders to date. We validate our framework by detecting drugs that have been undergoing clinical trial for treating some of the PNDs, but have no published results in their support. Our data provides comprehensive insights into the molecular pathology of PNDs and offers promising drug repositioning candidates for follow-up trials.

Hyperactivity and Reduced Activation of Anterior Hippocampus in Early Psychosis

OBJECTIVE

In schizophrenia, the anterior hippocampus is hyperactive and shows reduced task-related recruitment, but the relationship between these two findings is unclear. The authors tested the hypothesis that hyperactivity impairs recruitment of the anterior hippocampus during scene processing.

METHODS

Functional MRI data from 45 early-psychosis patients and 35 demographically matched healthy control subjects were analyzed using a block-design 1-back scene-processing task. Hippocampal activation in response to scenes and faces compared with scrambled images was measured. In a subset of 20 early-psychosis patients and 31 healthy control subjects, baseline hippocampal activity using cerebral blood volume (CBV) mapping was measured. Correlation analyses were used to examine the association between baseline hippocampal activity and task-related hippocampal activation.

RESULTS

Activation of the anterior hippocampus was significantly reduced and CBV in the anterior hippocampus was significantly increased in the early stages of psychosis. Increased CBV in early-psychosis patients was inversely correlated with task-related activation during scene processing in the anterior hippocampus.

CONCLUSIONS

Anterior hippocampal hyperactivity in early-psychosis patients appears to limit effective recruitment of this region during task performance. These findings provide novel support for the anterior hippocampus as a therapeutic target in the treatment of cognitive deficits in psychosis.

Applying vinpocetine to reverse synaptic ultrastructure by regulating BDNF-related PSD-95 in alleviating schizophrenia-like deficits in rat

BACKGROUND

Schizophrenia is a mental disorder characterized by hyperlocomotion, cognitive symptoms, and social withdrawal. Brain-derived neurotrophic factor (BDNF) and postsynaptic density (PSD)-95 are related to schizophrenia-like deficits via regulating the synaptic ultrastructure, and play a role in drug therapy. Vinpocetine is a nootropic phosphodiesterase-1 (PDE-1) inhibitor that can reverse ketamine-induced schizophrenia-like deficits by increasing BDNF expression. However, the effects of vinpocetine on alleviating schizophrenia-like deficits via reversing the synaptic ultrastructure by regulating BDNF-related PSD-95 have not been sufficiently studied.

METHODS

In this study, the schizophrenic model was built using ketamine (30 mg/kg) for 14 consecutive days. The effect of vinpocetine on reversing schizophrenia-like behaviors was examined via behavioral testing followed by treatment with certain doses of vinpocetine (20 mg/kg, i.p.). The BDNF and PSD-95 levels in the posterior cingulate cortex (PCC) were measured using biochemical assessments. In addition, the synaptic ultrastructure was observed using transmission electron microscopy (TEM).

RESULTS

Ketamine induced drastic schizophrenia-like behaviors, lower protein levels of BDNF and PSD-95, and a change in the synaptic ultrastructure in the PCC. After treatment, the vinpocetine revealed a marked amendment in schizophrenia-like behaviors induced by ketamine, including higher locomotor behavior, lower cognitive behavior, and social withdrawal defects. Vinpocetine could increase the PSD-95 protein level by up-regulating the expression of BDNF. In addition, the synaptic ultrastructure was changed after vinpocetine administration, including a reduction in the thickness and curvature of the synaptic interface, as well as an increase in synaptic cleft width in the PCC.

CONCLUSION

Vinpocetine can reverse the synaptic ultrastructure by regulating BDNF-related PSD-95 to alleviate schizophrenia-like deficits induced by ketamine in rats.

Anxiety-like features and spatial memory problems as a consequence of hippocampal SV2A expression

The Synaptic Vesicle Protein 2A (SV2A) is a transmembrane protein whose presence is reduced both in animal models and in patients with chronic epilepsy. Besides its implication in the epileptic process, the behavioural consequences of the changes in its expression remain unclear. The purpose of our research is to better understand the possible role(s) of this protein through the phenotype of cKO (Grik4 Cre+/-, SV2A lox/lox) mice, male and female, which present a specific decrease of SV2A expression levels in the hippocampal glutamatergic neurons but without any epileptic seizures. In this study, we compare the cKO mice with cHZ (Grik4 Cre+/-, SV2A lox/+) and WT (Grik4 Cre+/+, SV2A lox/lox) mice through a battery of tests, used to evaluate different features: the anxiety-related features (Elevated Plus Maze), the locomotor activity (Activity Chambers), the contextual fear-related memory (Contextual Fear Conditioning), and the spatial memory (Barnes Maze). Our results showed statistically significant differences in the habituation to a new environment, an increase in the anxiety levels and spatial memory deficit in the cHZ and cKO groups, compared to the WT group. No statistically significant differences due to the genotype appeared in the spontaneous locomotor activity or the fear-linked memory. However, sexual differences were observed in this last feature. These results highlight not only an important role of the SV2A protein in the cognitive and anxiety problems typically encountered in epileptic patients, but also a possible role in the symptomatology of other neurodegenerative diseases, such as the Alzheimer’s disease.

Hypoactivity of the lateral habenula contributes to negative symptoms and cognitive dysfunction of schizophrenia in rats

Dopaminergic (DAergic) hypofunction in the medial prefrontal cortex (mPFC) has been implicated in the negative and cognitive symptoms of schizophrenia and is regulated by serotonergic (5-HTergic) neurons in the dorsal raphe nucleus (DRN). The lateral habenula (LHb) is a key element in controlling DRN 5-HT neurons. We investigated how the LHb impacts the activity of mPFC neurons and whether it mediates the involvement of DRN on development of symptoms in a pharmacological animal model of schizophrenia. We used immunohisochemistry to assess cytochrome-c oxidase (COX) activity of the LHb in MK-801 model rats and extracellular firing recording to compare firing rates in LHb neurons of acute MK-801-treated rats. The sucrose preference, social interaction, and radial arm maze tests were used to access schizophrenia-like behavior in rats with electrolytically lesioned LHb. Finally, we examined levels of the dopamine D1 receptor (D1R) and tyrosine hydroxylase (TH) in the mPFC, and tryptophan hydroxylase 2 (TPH2) in the DRN of rats with LHb lesions to determine the possible mechanism underlying the schizophrenia-like behavior associated with lesioned LHb. We found that COX levels and LHb neuron firing rates decreased significantly in MK-801-treated animals. The LHb lesions induced negative and cognitive, but not positive symptoms of schizophrenia. The D1R and TH levels decreased in the mPFC while TPH2 expression elevated in the DRN and mPFC of LHb-lesioned rats. These results suggest that LHb hypoactivity may contribute to the negative and cognitive symptoms of schizophrenia by downregulating D1R expression in the mPFC, which might be mediated by DRN 5-HT neurons.

The profile of cognitive impairments in chronic ketamine users

The aim of this study was to examine the cognitive function in chronic ketamine users. Factors correlated to cognition impairments were analyzed. Sixty-three chronic ketamine users and 65 healthy subjects were recruited. Cognitive function was assessed by using immediate/delayed visual reproduction (IVR/DVR) tasks, immediate/delayed logical memory (ILM/DLM) tasks, Stroop test, Wisconsin card sorting test (WCST), and continuous performance test (CPT). Psychopathological symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). Ketamine users performed worse than controls on the IVR, ILM, DLM, Stroop and auditory CPT tests. IVR and DVR, color-naming and color-interference-reading scores were positively correlated with education level. In ketamine users ILM scores were negatively correlated with the negative subscale of PANSS. DLM score was positively correlated with average dose of ketamine use. Word-reading score was positively correlated with education level, and negatively correlated with duration of ketamine use. False hits in auditory CPT was positively correlated with duration of ketamine use. Number of trials to complete the first category and perseverative errors on WCST were positively correlated with the duration between the test and last ketamine use. Chronic ketamine users had cognitive impairments across multiple domains.

A greater tendency for representation mediated learning in a ketamine mouse model of schizophrenia

Representation mediated learning is a behavioral paradigm that could be used to potentially capture psychotic symptoms including hallucinations and delusions in schizophrenia. In studies of mediated learning, representations of prior experience can enter into current associations. Using a ketamine model of schizophrenia, we investigated whether mice exposed to ketamine during late adolescence subsequently showed an increased tendency to use a representation of a prior gustatory experience to form associations in learning. Mice were given prior experience of an odor and a taste presented together. The odor was subsequently presented alone with gastrointestinal illness induced by a lithium chloride injection. A consumption test was then given to assess whether the taste, despite its absence during conditioning, entered into an association with the induced illness. Such learning would be mediated via a representation of the taste activated by the odor. Our results showed that control mice displayed no aversion to the taste following the procedures just described, but mice that had been treated developmentally with ketamine exhibited a significant taste aversion, suggesting a greater propensity for mediated learning. Complementary to that finding, ketamine-exposed mice also showed a greater susceptibility to mediated extinction. Chronic treatment with the antipsychotic drug, risperidone, in ketamine-exposed mice attenuated mediated learning, a finding that may be related to its known efficacy in reducing the positive symptoms of schizophrenia. These data provide a setting with potential relevance to preclinical research on schizophrenia, to study the neural mechanisms underlying a propensity for aberrant associations and assessment of therapeutics. (PsycINFO Database Record