Ketamine-induced changes in rat behaviour: a possible animal model of schizophrenia. Test of predictive validity

The antipsychotic potential of Salix Mucronata on ketamine-induced rats

Salix mucronata is one of the herbal plants offered by the traditional health practitioners in KwaZulu-Natal, South Africa for the treatment of schizophrenia. This study aimed to investigate the effects of repeated administration of ketamine on social interaction, novelty and motivation in adult, male Sprague Dawley rats. It also aimed to investigate the potential of risperidone and the herbal extract of S. mucronata to reverse impairments that are induced by ketamine. Experimental rats (n=45) received a dose of ketamine at 30 mg/kg via intraperitoneal injection for 5 consecutive days. They were then allocated into their respective treatment groups and given risperidone (APD) and the herbal extract of S. mucronata (TM) at doses of 6 mg/kg and 5 mg/kg, respectively, for 7 consecutive days. Social behaviour was tested using the 3-chambered sociability test, and anhedonia was tested using the sucrose preference test. Ketamine induction elicited social withdrawal and reduced social novelty which were later successfully reversed by risperidone and S. mucronata. The rats showed reduced preference to sucrose post-induction and post-treatment. Ketamine and mild stress caused by scruff restraint elicited reduced weight gain for the animals. No differences were noted on brain mass between controls and experimental groups and also between risperidone and S. mucronata groups. However, reduced brain volume was noted in experimental groups. Dopamine and acetylcholine concentration levels were high in groups which received risperidone and S. mucronata. These findings highlight that the antipsychotic potential of S. mucronata is similar to risperidone.

Is the antidepressant effect of ketamine separate from its psychotomimetic effect? A review of rodent models

Ketamine is an NMDA (N-methyl-d-aspartate) glutamate receptor antagonist, which has a myriad of dose-dependent pharmacological and behavioral effects, including anesthetic, sedative, amnestic, analgesic, and anti-inflammatory properties. Intriguingly, ketamine at subanesthetic doses displays a relevant profile both in mimicking symptoms of schizophrenia and also as the first fast-acting treatment for depression. Here, we present an overview of the state-of-the-art knowledge about ketamine as an antidepressant as well as a pharmacological model of schizophrenia in animal models and human participants. Ketamine's dual effect appears to arise from its mechanism of action involving NMDA receptors, with both immediate and downstream consequences being triggered as a result. Finally, we discuss the feasibility of a unified approach linking the glutamatergic hypothesis of schizophrenia to the promising preclinical and clinical success of ketamine in the treatment of refractory depression.

Pre-adolescence repeat exposure to sub-anesthetic doses of ketamine induces long-lasting behaviors and cognition impairment in male and female rat adults

In pre-adolescence, repeated anesthesia may be required for therapeutic interventions. Adult cognitive and neurobehavioral problems may result from preadolescent exposure to anesthetics. This study examined the long-term morphological and functional effects of repeated sub-anesthetic doses of ketamine exposure on male and female rat adults during pre-adolescence. Weaned 48 pre-adolescent rats from eight mothers and were randomly divided into four equal groups: control group and the ketamine group of males and females (20 mg/kg daily for 14 days); then animals received care for 20-30 days. Repeated exposure to sub-anesthetic doses of ketamine on cognitive functions was assayed using Social discrimination and novel object tests. Besides, an elevated plus maze and fear conditioning apparatus were utilized to determine exploratory and anxiety-like behavior in adults. Toluidine blue stain was used to evaluate the number of dead neurons in the hippocampus, and the effects of ketamine on synaptic plasticity were compared in the perforant pathway of the CA1 of the hippocampus. Our study indicates that repeated exposure to sub-anesthetic doses of ketamine during pre-adolescence can result in neurobehavioral impairment in male and female rat adulthood but does not affect anxiety-like behavior. We found a significant quantifiable increase in dark neurons. Recorded electrophysiologically, repeat sub-anesthetic doses of ketamine resulted in hampering long-term potentiation and pair pulse in male adult animals. Our results showed that repeated exposure to sub-anesthetic doses of ketamine during pre-adolescence can induce hippocampus and neuroplasticity changes later in adulthood. This study opens up a new line of inquiry into potential adverse outcomes of repeated anesthesia exposure in pre-adolescent rats.

NMDA receptor modulation by Esculetin: Investigating behavioral, biochemical and neurochemical effects in schizophrenic mice model

Schizophrenia, a global mental health disorder affecting approximately 1 % of the population, is characterized by neurotransmitter dysregulation, particularly dopamine, serotonin, and glutamate. Current antipsychotic therapies, despite their efficacy, are accompanied by adverse effects, which has motivated researchers to investigate more secure substitutes. This study examines the potential antipsychotic effects of esculetin, a natural coumarin derivative recognized for its wide-ranging pharmacological activities (anti-inflammatory, antioxidant, anti-pathogenic, anticancer, and neuroprotective), in animal model of schizophrenia induced by ketamine. In order to induce disease, acute and chronic ketamine administration was performed on Swiss albino mice, supplemented with esculetin (as the test substance) and clozapine (as the reference standard). Behavioral studies and biochemical assays were performed to evaluate positive, negative, and cognitive symptoms of schizophrenia, as well as antioxidant and oxidant levels in various brain regions. Esculetin demonstrated significant improvements in behavioral symptoms, attenuated oxidative stress and neuroinflammation, and modulated neurotransmitter levels. Afterwards, ELISA was performed to evaluate levels of schizophrenia biomarkers AChE, BDNF. Moreover, proinflammatory cytokines (IL-6 and TNF-α) and NF-κB were also determined. Histopathological parameters of under study brain parts i.e., hippocampus, cortex and striata were also assessed. Esculetin and clozapine significantly (***p < 0.0001) altered ketamine induced behavioral symptoms and attenuated ketamine induced oxidative stress and neuroinflammation. Additionally, esculetin significantly (***p < 0.0001) altered neurotransmitter (dopamine, serotonin, glutamate) levels. ELISA analysis depicts ketamine reduced BDNF levels in hippocampus, cortex and striata while esculetin significantly (***p < 0.0001) increased BDNF levels in under study three parts of brain. Histopathological changes were seen in test groups. The findings of this study indicate that esculetin may have therapeutic potential in the treatment of schizophrenia induced by ketamine. As a result, esculetin may have the potential to be utilized as a treatment for schizophrenia.

Effects of ketamine on rat social behavior as analyzed by DeepLabCut and SimBA deep learning algorithms

Traditional methods of rat social behavior assessment are extremely time-consuming and susceptible to the subjective biases. In contrast, novel digital techniques allow for rapid and objective measurements. This study sought to assess the feasibility of implementing a digital workflow to compare the effects of (R,S)-ketamine and a veterinary ketamine preparation Vetoquinol (both at 20 mg/kg) on the social behaviors of rat pairs. Historical and novel videos were used to train the DeepLabCut neural network. The numerical data generated by DeepLabCut from 14 video samples, representing various body parts in time and space were subjected to the Simple Behavioral Analysis (SimBA) toolkit, to build classifiers for 12 distinct social and non-social behaviors. To validate the workflow, previously annotated by the trained observer historical videos were analyzed with SimBA classifiers, and regression analysis of the total time of social interactions yielded R 2 = 0.75, slope 1.04; p < 0.001 (N = 101). Remarkable similarities between human and computer annotations allowed for using the digital workflow to analyze 24 novel videos of rats treated with vehicle and ketamine preparations. Digital workflow revealed similarities in the reduction of social behavior by both compounds, and no substantial differences between them. However, the digital workflow also demonstrated ketamine-induced increases in self-grooming, increased transitions from social contacts to self-grooming, and no effects on adjacent lying time. This study confirms and extends the utility of deep learning in analyzing rat social behavior and highlights its efficiency and objectivity. It provides a faster and objective alternative to human workflow.

Haloperidol alters neurotrophic factors and epigenetic parameters in an animal model of schizophrenia induced by ketamine

This study aimed to evaluate Haloperidol's (Hal) effects on the behavioral, neurotrophic factors, and epigenetic parameters in an animal model of schizophrenia (SCZ) induced by ketamine (Ket). Injections of Ket or saline were administered intraperitoneal (once a day) between the 1st and 14th days of the experiment. Water or Hal was administered via gavage between the 8th and 14th experimental days. Thirty minutes after the last injection, the animals were subjected to behavioral analysis. The activity of DNA methyltransferase (DNMT), histone deacetylase (HDAC), and histone acetyltransferase and levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), and glial-derived neurotrophic factor (GDNF) were evaluated in the frontal cortex, hippocampus, and striatum. Ket increased the covered distance and time spent in the central area of the open field, and Hal did not reverse these behavioral alterations. Significant increases in the DNMT and HDAC activities were detected in the frontal cortex and striatum from rats that received Ket, Hal, or a combination thereof. Besides, Hal per se increased the activity of DNMT and HDAC in the hippocampus of rats. Hal per se or the association of Ket plus Hal decreased BDNF, NGF, NT-3, and GDNF, depending on the brain region and treatment regimen. The administration of Hal can alter the levels of neurotrophic factors and the activity of epigenetic enzymes, which can be a factor in the development of effect collateral in SCZ patients. However, the precise mechanisms involved in these alterations are still unclear.

Lipopolysaccharide Exacerbates Ketamine-Induced Psychotic-Like Behavior, Oxidative Stress, and Neuroinflammation in Mice: Ameliorative Effect of Diosmin

Schizophrenia, a neuropsychiatric disorder has been associated with aberrant neurotransmission affecting behaviors, social preference, and cognition. Limitations in understanding its pathogenesis via the dopamine hypothesis have engendered other hypotheses such as the glutamate hypothesis. That antagonism of the N-methyl-D-aspartate receptor (NMDAR) elicits schizophrenia-like behaviors indistinguishable from the disorder in animal and human models. There are growing concerns that redox imbalance and neuro-immuno dysfunction may play role in aggravating the symptomologies of this disorder. This 14-day treatment study was designed to investigate the effect of diosmin on lipopolysaccharide (LPS) plus ketamine (NMDAR antagonist). Mice were divided into 4 groups (n = 6). Group 1 was administered 5% DMSO (10 mL/kg, i.p) while group 2-4 received LPS (0.1 mg/kg, i.p) daily for 14 days. Diosmin (50 mg/kg, i.p) and risperidone (0.5 mg/kg, i.p) were given to groups 3 and 4 respectively. Groups 2-4 were given KET (20 mg/kg, i.p.) daily from days 8-14. Behavioral tests were done 30 min after the last dose, and oxidative stress and neuroinflammatory maker were assayed. LPS plus ketamine-induced hyperlocomotion, stereotypy, decreased social preference, and memory impairment. Furthermore, LPS plus-ketamine-induced oxidative stress (reduced GSH, CAT, SOD, and increased MDA and nitrite levels) and marked pro-inflammatory cytokines TNF-α and IL-6 suggesting neuroinflammation. However, diosmin attenuated behavioral deficits and improved memory. Additionally, diosmin potentiated antioxidant level via increased GSH, CAT, and SOD while reducing MDA and nitrite levels. Finally, diosmin reduced TNF-α and IL-6 suggesting anti-neuro-immuno activity. Conclusively, diosmin attenuated LPS plus ketamine-induced behavioral deficits, oxidative stress, neuroinflammation, and improved memory.

The α2C-adrenoceptor antagonist JP-1302 controls behavioral parameters, tyrosine hydroxylase activity and receptor expression in a rat model of ketamine-induced schizophrenia-like deficits

Schizophrenia is a chronic disabling disease affecting 1 % of the population. Current antipsychotics have limited efficacy in mitigating the severity of the symptoms of the disease. Therefore, searching for new therapeutic targets is essential. Previous studies have shown that α_2C-adrenoceptor antagonists may have antipsychotic and pro-cognitive effects. Therefore, the current study evaluates the behavioral and neurochemical effects of JP-1302, a selective α_2C-adrenoceptor antagonist, in a model of schizophrenia-like deficits induced by sub-chronic ketamine (KET) administration. Here, we administered ketamine (25 mg/kg, i.p.) to male and female Wistar rats for eight consecutive days. On the last two days of ketamine administration, rats were pretreated with either JP-1302 (1-3-10 μmol/kg, i.p.), chlorpromazine (0.1 mg/kg, i.p.), or saline, and the behavioral tests were performed. Behaviors related to positive (locomotor activity), negative (social interaction), and cognitive (novel object recognition) symptoms of schizophrenia were assessed. Glutamate, glutamine, GABA levels, and α_2C-adrenoceptor expression were measured in the frontal cortex and the hippocampus. Tyrosine hydroxylase immunocytochemical reactivity was also shown in the midbrain regions. Sub-chronic ketamine administration increased locomotor activity and produced robust social interaction and object recognition deficits, and JP-1302 significantly ameliorated ketamine-induced cognitive deficits. Ketamine induced a hyperdopaminergic activity in the striatum, which was reversed by the treatment with JP-1302. Also, the α_2C-adrenoceptor expression was higher in the frontal cortex and hippocampus in the ketamine-treated rats. Our findings confirm that α_2C-adrenoceptor antagonism may be a potential drug target for treating cognitive disorders related to schizophrenia.

A vitamina C na esquizofrenia apresenta benefício? Estudo preliminar com análise comportamental em ratos

RESUMO Objetivo O objetivo deste estudo foi analisar em ratos modelos de esquizofrenia, induzidos pela administração de cetamina, a possibilidade dos efeitos benéficos do ácido ascórbico na esquizofrenia, por meio do teste comportamental. Métodos O estudo preliminar foi simples-cego e randomizado. Foi realizado o protocolo de psicose por cetamina em 24 ratos Wistar submetidos posteriormente à análise comportamental. No primeiro grupo, foram administradas: água e cetamina; no segundo: ácido ascórbico e cetamina; no terceiro: antipsicótico, ácido ascórbico e cetamina; e no quarto: antipsicótico, água e cetamina. A análise comportamental foi feita por meio do Open Field Test, considerado o método-padrão para avaliar comportamento em modelos animais de esquizofrenia. A análise estatística foi realizada pelo software IBM-SPSS, por meio dos Modelos Lineares Generalizados. Resultados O tratamento em monoterapia de haloperidol (Média Quadrante: 44,5 ± 15,8; IC: 13,54-75,46/Média Centro: 2,67 ± 0,67; IC: 1,63-4,35) e aquele em conjunto com a vitamina C (Média Quadrante: 38,67 ± 15,8; IC: 7,71-69,52/Média Centro: 2,00 ± 0,58; IC: 1,14-3,52) demonstraram benefícios nos ratos modelos de esquizofrenia induzidos por cetamina (Média Quadrante: 108,5 ± 15,8; IC: 77,54-139,46/Média Centro: 11,33 ± 1,37; IC: 8,94-14,37) (p < 0,001). O tratamento isolado com a vitamina C não apresentou resultado significante (Média Quadrante: 62,00 ± 15,8; IC: 31,04-92,96/Média Centro: 7,00 ± 1,08; IC: 5,17-9,47). Conclusão A associação de antipsicótico e vitamina C e somente o antipsicótico demonstraram efeito terapêutico em relação aos controles. A vitamina C isolada não apresentou benefício.

Schizophrenia-like endurable behavioral and neuroadaptive changes induced by ketamine administration involve Angiotensin II AT1 receptor

Schizophrenia is a chronic disease affecting 1% worldwide population, of which 30% are refractory to the available treatments: thus, searching for new pharmacological targets is imperative. The acute and repeated ketamine administration are validated preclinical models that recreate the behavioral and neurochemical features of this pathology, including the parvalbumin-expressing interneurons dysfunction. Angiotensin II, through AT₁ receptors (AT₁-R), modulates the dopaminergic and GABAergic neurotransmission. We evaluated the AT₁-R role in the long-term neuronal activation and behavioral alterations induced by repeated ketamine administration. Adult male Wistar rats received AT₁-R antagonist candesartan/vehicle (days 1-10) and ketamine/saline (days 6-10). After 14 days of drug-free, neuronal activation and behavioral analysis were performed. Locomotor activity, social interaction and novel object recognition tests were assessed at basal conditions or after ketamine challenge. Immunostaining for c-Fos, GAD67 and parvalbumin were assessed after ketamine challenge in cingulate, insular, piriform, perirhinal, and entorhinal cortices, striatum, and hippocampus. Additionally, to evaluate the AT₁-R involvement in acute ketamine psychotomimetic effects, the same behavioral tests were performed after 6 days of daily-candesartan and a single-ketamine administration. We found that ketamine-induced long-lasting schizophrenia-like behavioral alterations, and regional-dependent neuronal activation changes, involving the GABAergic neurotransmission system and the parvalbumin-expressing interneurons, were AT₁-R-dependent. The AT₁-R were not involved in the acute ketamine psychotomimetic effects. These results add new evidence to the wide spectrum of action of ketamine and strengthen the AT₁-R involvement in endurable alterations induced by psychostimulants administration, previously proposed by our group, as well as their preponderant role in the development of psychiatric pathologies.

Involvement of anti-inflammatory, antioxidant, and BDNF up-regulating properties in the antipsychotic-like effect of the essential oil of Alpinia zerumbet in mice: a comparative study with olanzapine

The current drug therapy for schizophrenia effectively treats acute psychosis and its recurrence; however, this mental disorder's cognitive and negative symptoms are still poorly controlled. Antipsychotics present important side effects, such as weight gain and extrapyramidal effects. The essential oil of Alpinia zerumbet (EOAZ) leaves presents potential antipsychotic properties that need further preclinical investigation. Here, we determined EAOZ effects in preventing and reversing schizophrenia-like symptoms (positive, negative, and cognitive) induced by ketamine (KET) repeated administration in mice and putative neurobiological mechanisms related to this effect. We conducted the behavioral evaluations of prepulse inhibition of the startle reflex (PPI), social interaction, and working memory (Y-maze task), and verified antioxidant (GSH, nitrite levels), anti-inflammatory [interleukin (IL)-6], and neurotrophic [brain-derived neurotrophic factor (BDNF)] effects of this oil in hippocampal tissue. The atypical antipsychotic olanzapine (OLZ) was used as standard drug therapy. EOAZ, similarly to OLZ, prevented and reversed most KET-induced schizophrenia-like behavioral alterations, i.e., sensorimotor gating deficits and social impairment. EOAZ had a modest effect on the prevention of KET-associated working memory deficit. Compared to OLZ, EOAZ showed a more favorable side effects profile, inducing less cataleptic and weight gain changes. EOAZ efficiently protected the hippocampus against KET-induced oxidative imbalance, IL-6 increments, and BDNF impairment. In conclusion, our data add more mechanistic evidence for the anti-schizophrenia effects of EOAZ, based on its antioxidant, anti-inflammatory, and BDNF up-regulating actions. The absence of significant side effects observed in current antipsychotic drug therapy seems to be an essential benefit of the oil.

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.

Wisket rat model of schizophrenia: Impaired motivation and, altered brain structure, but no anhedonia

It is well-known that the poor cognition in schizophrenia is strongly linked to negative symptoms, including motivational deficit, which due to, at least partially, anhedonia. The goal of this study was to explore whether the schizophrenia-like Wisket animals with impaired motivation (obtained in the reward-based hole-board test), also show decreased hedonic behavior (investigated with the sucrose preference test). While neurochemical alterations of different neurotransmitter systems have been detected in the Wisket rats, no research has been performed on structural changes. Therefore, our additional aim was to reveal potential neuroanatomical and structural alterations in different brain regions in these rats. The rats showed decreased general motor activity (locomotion, rearing and exploration) and impaired task performance in the hole-board test compared to the controls, whereas no significant difference was observed in the sucrose preference test between the groups. The Wisket rats exhibited a significant decrease in the frontal cortical thickness and the hippocampal area, and moderate increases in the lateral ventricles and cell disarray in the CA3 subfield of hippocampus. To our knowledge, this is the first study to investigate the hedonic behavior and neuroanatomical alterations in a multi-hit animal model of schizophrenia. The results obtained in the sucrose preference test suggest that anhedonic behavior might not be involved in the impaired motivation obtained in the hole-board test. The neuropathological changes agree with findings obtained in patients with schizophrenia, which refine the high face validity of the Wisket model.

Identification of Molecular Markers of Clozapine Action in Ketamine-Induced Cognitive Impairment: A GPCR Signaling PathwayFinder Study

Background: Cognitive disorders associated with schizophrenia are closely linked to prefrontal cortex (PFC) dysfunction. Administration of the non-competitive NMDA receptor antagonist ketamine (KET) induces cognitive impairment in animals, producing effects similar to those observed in schizophrenic patients. In a previous study, we showed that KET (20 mg/kg) induces cognitive deficits in mice and that administration of clozapine (CLZ) reverses this effect. To identify biochemical mechanisms related to CLZ actions in the context of KET-induced impairment, we performed a biochemical analysis using the same experimental paradigm—acute and sub-chronic administration of these drugs (0.3 and 1 mg/kg). Methods: Since the effect of CLZ mainly depends on G-protein-related receptors, we used the Signaling PathwayFinder Kit to identify 84 genes involved in GPCR-related signal transduction and then verified the genes that were statistically significantly different on a larger group of mice using RT-PCR and Western blot analyses after the administration of acute and sub-chronic drugs. Results: Of the 84 genes involved in GPCR-related signal transduction, the expression of six, βarrestin1, βarrestin2, galanin receptor 2 (GalR2), dopamine receptor 2 (DRD2), metabotropic glutamate receptor 1 (mGluR1), and metabotropic glutamate receptor 5 (mGluR5), was significantly altered. Since these genes affect the levels of other signaling proteins, e.g., extracellular signal-regulated kinase 1/2 (ERK1/2), G protein-coupled receptor kinase 2 (Grk2), and G protein-gated inwardly rectifying potassium 3 (Girk3), we determined their levels in PFC using Western blot. Most of the observed changes occurred after acute treatment with 0.3 mg/kg CLZ. We showed that acute treatment with CLZ at a lower dose significantly increased βarrestin1 and ERK1/2. KET treatment induced the upregulation of βarrestin1. Joint administration of these drugs had no effect on the βarrestin1 level. Conclusion: The screening kit we used to study the expression of GPCR-related signal transduction allowed us to select several important genes affected by CLZ. However, the obtained data do not explain the mechanism of action of CLZ that is responsible for reversing KET-induced cognitive impairment.

N, N-dimethylglycine Protects Behavioral Disturbances and Synaptic Deficits Induced by Repeated Ketamine Exposure in Mice

Ketamine, an N-methyl-d-aspartate receptor (NMDAR) blocker, is gaining ground as a treatment option for depression. The occurrence of persistent psychosis and cognitive impairment after repeated use of ketamine remains a concern. N, N-dimethylglycine (DMG) is a nutrient supplement and acts as an NMDAR glycine site partial agonist. The objective of this study was to assess whether DMG could potentially prevent the behavioral and synaptic deficits in mice after repeated ketamine exposure. Male ICR mice received ketamine (20 mg/kg) from postnatal day (PN) 33-46, twice daily, for 14 days. The locomotor activity, novel location recognition test (NLRT), novel object recognition test (NORT), social interaction test, head twitch response induced by serotonergic hallucinogen, and the basal synaptic transmission and long-term potentiation (LTP) in the hippocampal slices were monitored after repeated ketamine treatment. Furthermore, the protective effects of repeated combined administration of DMG (30 and 100 mg/kg) with ketamine on behavioral abnormalities and synaptic dysfunction were assessed. The results showed that mice exhibited memory impairments, social withdrawal, increased head twitch response, reduced excitatory synaptic transmission, and lower LTP after repeated ketamine exposure. The ketamine-induced behavioral and synaptic deficits were prevented by co-treatment with DMG. In conclusion, these findings may pave a new path forward to developing a combination formula with ketamine and DMG for the treatment of depression and other mood disorders.

Combined Low Dose of Ketamine and Social Isolation: A Possible Model of Induced Chronic Schizophrenia-Like Symptoms in Male Albino Rats

While animal models for schizophrenia, ranging from pharmacological models to lesions and genetic models, are available, they usually mimic only the positive symptoms of this disorder. Identifying a feasible model of chronic schizophrenia would be valuable for studying the possible underlying mechanism and to investigate emerging treatments. Our hypothesis starts from the observation that combining ketamine with isolation could result in long-lasting neuro-psychological deficits and schizophrenia-like features; thus, it could probably be used as the first model of chronic schizophrenia that emphasizes the characteristic of having a multifactorial etiology. By the means of this study, we investigated the effects of ketamine administration combined with isolation in inducing schizophrenia-like symptoms in male albino rats and the brain reactive oxygen species levels. Our results showed that the number of lines crossings in the open field test, the number of open arm entries in the elevated plus maze, and the spontaneous alternations percentage in the Y-maze were significantly lower in the ketamine + isolation group compared to both the control and ketamine + social housing group (p < 0.05). Furthermore, the ketamine + isolation intervention significantly increased the MDA levels and decreased the GPx levels both in the hippocampus and the cortex of the rats. In addition, our premise of creating a model capable of exhibiting both positive and negative symptoms of schizophrenia was also based on adding the aripiprazole treatment to a group of rats. Therefore, we compared the ketamine + social isolation group with the ketamine + social isolation + aripiprazole group in order to attempt to discover if the antipsychotic drug would significantly decrease the potential positive schizophrenia-like symptoms induced by social isolation and ketamine. Given that we obtained significant results, we cautiously presume that this might be an important step in developing our animal model capable of illustrating both positive and negative symptoms of schizophrenia. This study could be a first step towards the creation of a complex animal model capable of exhibiting the multifactorial origin and manifestation of schizophrenia.

Molecular mechanisms involved in the prevention and reversal of ketamine-induced schizophrenia-like behavior by rutin: the role of glutamic acid decarboxylase isoform-67, cholinergic, Nox-2-oxidative stress pathways in mice

Mounting evidences have shown that nicotinamide adenine dinucleotide phosphate oxidase-2 (Nox-2) pathway modifies glutamic-acid decarboxylase-67 (GAD₆₇) (GABAergic enzyme) and cholinergic systems via oxidative-nitrergic mechanisms in schizophrenia pathology. Rutin, a neuroactive antioxidant compound, with proven neuroprotective property has been shown to reduce schizophrenic-like behavior in mice. This study sought to investigate the mechanisms of action of the psychopharmacological activity of rutin in the preventive and reversal effects of ketamine-induced schizophrenic-like behavior, oxidative-nitrergic stress, cholinergic and GABAergic derangements in mice. In the preventive treatment, male mice were given rutin (0.1, 0.2 and 0.4 mg/kg) or risperidone (0.5 mg/kg) orally for 14 days prior to ketamine (20 mg/kg, i.p.) treatment from the 8 to 14th day. However, in the reversal treatment, ketamine was given for 14 days prior to rutin and risperidone. Behavioral (open-field, social-interaction and Y-maze tests), biochemical (oxidative/nitrergic stress markers, acetylcholinesterase activity), immunohistochemical (GAD₆₇, Nox-2) and neuronal cell deaths in the striatum, prefrontal cortex, and hippocampus were evaluated. Ketamine-induced behavioral impairments were prevented and reversed by rutin. Exposure of mice to ketamine increased malondialdehyde, nitrite contents, acetylcholinesterase activity, neuronal cell death and Nox-2 expressions in the striatum, prefrontal cortex and hippocampus. Conversely, these derangements were prevented and reversed by rutin. The decreased glutathione levels due to ketamine were marked increased by rutin. Rutin only prevented ketamine-induced decrease in GAD₆₇ expression in the striatal-hippocampal region. Altogether, the study showed that the prevention and reversal treatments of mice with rutin attenuated ketamine-induced schizophrenic-like behaviors via reduction of Nox-2 expression, oxidative/nitrergic stresses, acetylcholinesterase activity, and increased GAD₆₇ enzyme.

Naringin treatment improved main clozapine-induced adverse effects in rats; emphasis on weight gain, metabolic abnormalities, and agranulocytosis

Schizophrenia is one of the major neuropsychiatric disorders affecting people worldwide. Unfortunately, currently available antipsychotic medications possess several side effects. Among them, clozapine is one of the atypical antipsychotics prescribed in schizophrenia wing to its blocking effect on dopamine (D2) and serotonin (5-HT_1c ) receptors. However, it has been recently reserved for resistant schizophrenia due to its several side effects. The current research aimed at investigating potential naringin add-on benefit to cease the main side effects of clozapine in ketamine-induced psychosis in rats. In this study, schizophrenia was induced in rats via ketamine administration that could promote neuropathological patterns of schizophrenia. Afterwards, clozapine and naringin were administered to rats in order to improve such effects induced by ketamine. Clozapine administration promoted weight gain, hyperglycemia, dyslipidemia, and agranulocytosis. However, naringin was able to reduce such adverse effects when added to clozapine treatment. Naringin increased total leukocyte count preventing agranulocytosis either when administered alone or in combination with clozapine. In addition, via its metabolic activities, naringin treatment lowered serum total cholesterol and triglycerides levels. Moreover, naringin prevented weight gain when administered. Finally, naringin reduced serum glucose level preventing hyperglycemia associated with clozapine treatment. Collectively, these findings may suggest that naringin possesses a potential add-on benefit to clozapine in treatment of schizophrenia.

Ascorbic acid supplementation attenuates schizophrenia-like symptoms in an animal model induced by ketamine

Schizophrenia is a chronic neuropsychiatric disorder with a poorly understood pathophysiology. The theories about the disorder are mainly about dysregulation in one or more systems of neurotransmitters, and the progression triggers the presence of inflammatory markers indicates the possibility that the disorder is initially an inflammatory disease. The objective was to evaluate the ascorbic acid supplementation in an animal model of schizophrenia, on behavioral parameters, and cytokines involved in inflammation IL-1β, IL-10. Wistar rats with 60 days of age were used which were supplemented with ascorbic acid at 0.1, 1, and 10 mg/kg or saline for 14 days via orogastric gavage. Subsequently, four groups were given ketamine (25 mg/kg) and four groups received intraperitoneal saline from the 9th-15th day of the experiment. After 30 min of the last administration of ketamine/saline, and behavioral test, rats were killed by guillotine decapitation and the brain structures were carefully dissected for biochemical analysis. Results showed that ascorbic acid supplementation prevented motor sensory loss but nor alter other parameters evaluated. We concluded that ascorbic acid may be used as a therapeutic adjuvant in schizophrenia and may help to improve the schizophrenic patient's life quality.

Withdrawal from chronic ethanol exposure increases postsynaptic glutamate function of insular cortex projections to the rat basolateral amygdala

A key feature of alcohol use disorder (AUD) is negative affect during withdrawal, which often contributes to relapse and is thought to be caused by altered brain function, especially in circuits that are important mediators of emotional behaviors. Both the agranular insular cortex (AIC) and the basolateral amygdala (BLA) regulate emotions and are sensitive to ethanol-induced changes in synaptic plasticity. The AIC and BLA are reciprocally connected; and the effects of chronic ethanol exposure on this circuit have yet to be explored. Here, we use a combination of optogenetics and electrophysiology to examine the pre- and postsynaptic changes that occur to AIC-BLA synapses following withdrawal from 7- or 10-days of chronic intermittent ethanol (CIE) exposure. While CIE/withdrawal did not alter presynaptic glutamate release probability from AIC inputs, withdrawal from 10, but not 7, days of CIE increased AMPA receptor-mediated postsynaptic function at these synapses. Additionally, NMDA receptor-mediated currents evoked by electrical stimulation of the external capsule, which contains AIC afferents, were also increased during withdrawal. Notably, a single subanesthetic dose of ketamine administered at the onset of withdrawal prevented the withdrawal-induced increases in both AMPAR and NMDAR postsynaptic function. Ketamine also prevented the withdrawal-induced increases in anxiety-like behavior measured using the elevated zero maze. Together, these findings suggest that chronic ethanol exposure increases postsynaptic function within the AIC-BLA circuit and that ketamine can prevent ethanol withdrawal-induced alterations in synaptic plasticity and negative affect.

Comprehensive mapping of cytochrome c oxidase activity in the rat brain after sub-chronic ketamine administration

Ketamine is a noncompetitive antagonist of glutamatergic N-methyl-d-aspartate receptors. Its acute effects on healthy volunteers and schizophrenia patients mimic some acute psychotic, but also cognitive and negative symptoms of schizophrenia, and subchronic treatment with ketamine has been used as an animal model of psychotic disorders. Glutamatergic neurotransmission is tightly coupled to oxidative metabolism in the brain. Quantitative histochemical mapping of cytochrome c oxidase (COX) activity, which reflect long-term energy metabolism, was carried out in rats that received a daily subanaesthetic dose (30 mg/kg) of ketamine for 10 days. In total, COX activity was measured in 190 brain regions to map out metabolic adaptations to the subchronic administration of ketamine. Ketamine treatment was associated with elevated COX activity in nine brain sub-regions in sensory thalamus, basal ganglia, cortical areas, hippocampus and superior colliculi. Changes in pairwise correlations between brain regions were studied with differential correlation analysis. Ketamine treatment was associated with the reduction of positive association between brain regions in 66 % of the significant comparisons. Different layers of the superior colliculi showed the strongest effects. Changes in other visual and auditory brain centres were also of note. The locus coeruleus showed opposite pattern of increased coupling to mainly limbic brain regions in ketamine-treated rats. Our study replicated commonly observed activating effects of ketamine in the hippocampus, cingulate cortex, and basal ganglia. The current study is the first to extensively map the oxidative metabolism in the CNS in the ketamine model of schizophrenia. It shows that ketamine treatment leads to the re-organization of activity in sensory and memory-related brain circuits.

The Effect of Minor Doses of Olanzapine-Solid Lipid Nanoparticles on an Animal Model of Schizophrenia (Neurochemical and Behavioral Study) and the Side Effect

Background and Objective:

Olanzapine (OLZ) is an atypical psychotic agent; the poor bioavailability of olanzapine is the most important issue in its treatment. The present work was carried out to evaluate the oral form of olanzapine solid lipid nanoparticles (OLZ-SLN) to overcome its poor bioavailability and compare between the effect of different doses of OLZ and OLZ-SLN on ketamineinduced schizophrenic-like symptoms. The study was extended to evaluate the adverse effects of subchronic administration of these doses of OLZ and its SLN.

Methods:

OLZ-SLN was prepared by hot homogenization, particle size, zeta potential and in vitro release and entrapping efficiency studies were performed. In order to assess the effective dose in the treatment of schizophrenia, the effect of different doses of OLZ and OLZ-SLN on open field was assessed and passive avoidance tests were carried out. The test was performed to examine the effects of excitatory and inhibitory amino acids, as well as dopamine and serotonin levels in the brain regions.

Results and Conclusion:

The new oral formula showed high stability and sustained release. The administration of low and high dose of OLZ-SLN equivalent to (1/10 and 1/20 from the therapeutic dose before ketamine attenuated the behavioral abnormalities by blocking the effect of ketamine-induced increase in glutamate, dopamine and serotonin levels and enhanced apoptosis were studied in the brain areas. In addition, the sub-chronic treatment with OLZ-SLN showed no adverse effect while the treatment with OLZ free form did.

Ketamine applications beyond anesthesia - A literature review

Ketamine's clinical use began in the 1970s. Physicians benefited from its safety and ability to induce short-term anesthesia and analgesia. The psychodysleptic effects caused by the drug called its further clinical use into question. Despite these unpleasant effects, ketamine is still applied in veterinary medicine, field medicine, and specialist anesthesia. Recent intensive research brought into light new possible applications of this drug. It began to be used in acute, chronic and cancer pain management. Most interesting reports come from research on the antidepressive and antisuicidal properties of ketamine giving hope for the creation of an effective treatment for major depressive disorder. Other reports highlight the possible use of ketamine in treating addiction, asthma and preventing cancer growth. Besides clinical use, the drug is also applied to in animal model of schizophrenia. It seems that nowadays, with numerous possible applications, the use of ketamine has returned; to its former glory. Nevertheless, the drug must be used with caution because still the mechanisms by which it executes its functions and long-term effects of its use are not fully known. This review aims to discuss the well-known and new promising applications of ketamine.

Ultrasonic vocalizations as a tool in studying emotional states in rodent models of social behavior and brain disease

Rodents emit ultrasonic vocalizations (USVs) to communicate the presence of positive or negative emotional states and to coordinate social interactions. On this basis, USVs are increasingly being used as a behavioral readout in rodent studies of affect, motivation and social behavior. Notably, several investigations have demonstrated that rodents emit USVs when tested in experimental paradigms that are used in preclinical studies of psychiatric and neurological diseases. Moreover, it has been shown that calling behavior may be influenced by genetic and/or environmental factors (i.e., stress), early rearing conditions that have been implicated in brain disease, as well as psychoactive drugs. Hence, measuring USV emissions has emerged as a useful tool in studying the mechanisms that underlie the emotional disturbances featuring certain brain diseases, as well as in the development of suited pharmacological therapies. This review provides an overview of the behavioral significance of USV emissions and describes the contexts that promote calling behavior in rats and mice. Moreover, the review summarizes the current evidence concerning the use of USVs as a marker of affect in rat and mouse models of sociability, psychiatric diseases and neurological diseases, and discusses the strengths and current limitations of using USVs as a behavioral readout in rodent studies of emotional behavior. This article is part of the Special Issue entitled 'The neuropharmacology of social behavior: from bench to bedside'.

Changes in behavioural parameters, oxidative stress and neurotrophins in the brain of adult offspring induced to an animal model of schizophrenia: The effects of FA deficient or FA supplemented diet during the neurodevelopmental phase

A deficiency of maternal folic acid (FA) can compromise the function and development of the brain, and may produce a susceptibility to diseases such as schizophrenia (SZ) in the later life of offspring. The aim of this study was to evaluate the effects of both FA deficient and FA supplemented diets during gestation and lactation on behavioural parameters, the markers of oxidative stress and neurotrophic factors in adult offspring which had been subjected to an animal model of SZ. Female mother rats (Dam's) were separated into experimental maternal groups, which began receiving a special diet (food) consisting of the AIN-93 diet, a control diet, or an FA deficient diet during the periods of pregnancy and lactation. Dam's receiving the control diet were further subdivided into four groups: one group received only control diet, while three groups to receive supplementation with FA at different doses (5, 10 and 50 mg/kg). Adult offspring bred from the Dam's were divided into ten groups for induction of the animal model of SZ through the administration of ketamine (Ket) (25 mg/kg). After the last administration of the drug, the animals were subjected to the behavioural tests and were then euthanized. The frontal cortex (FC) and hippocampus (Hip) were then dissected for later biochemical analysis. Our data demonstrates that Ket induced the model of SZ by altering the behavioural parameters (e.g. hyperlocomotion, social impairment, deficits in the sensory-motor profile and memory damage in the adult animals); and also caused changes in the parameters of oxidative stress (lipid hydroperoxide - LPO; 8-isoprostane - 8-ISO; 4-hydroxynonenal - 4-HNE; protein carbonyl content; superoxide dismutase - SOD and catalase - CAT) as well as in the levels of neurotrophic factors (brain-derived neurotrophic factor - BDNF and nerve growth factor - NGF) particularly within the FC of adult offspring. A deficiency in maternal FA, alone or in combination with ket, was able to induce hyperlocomotion and social impairment in the offspring with increased levels of lipid and protein damage (LPO, 8-ISO, 4-HNE, carbonylation of protein) within the FC, increased activity of antioxidant enzymes (SOD and CAT) in both of the brain structures studied, and also reduced the levels of neurotrophins (BDNF and NGF), particularly within the Hip of the adult offspring. Supplementation of FA (5, 10 and 50 mg/kg) to the Dam's was mostly able to prevent the cognitive damage which was induced by Ket in the adult animals. FA (10 and 50 mg/kg) attenuated the action of Ket in the animals in relation to the biochemical parameters, proving the possible neuroprotective effect of FA in the adulthood of offspring that were subjected to the animal model of SZ. Our study indicates that the intake of maternal FA during pregnancy and lactation plays an important role, particularly in the regulation of markers of oxidative stress and neurotrophins.

Probable mechanisms involved in the antipsychotic-like activity of morin in mice

Evidence derived from preliminary studies suggests that morin, a neuroactive flavonoid with proven antioxidant and antiinflammatory properties possess antipsychotic-like activity. The present study was designed to evaluate the probable mechanisms involve in the antipsychotic-like activity of morin in ketamine model of schizophrenia. The effects of morin, haloperidol and risperidone on neurobehavioral and anti-schizophrenia-like effects were evaluated in mice (n = 7) following intraperitoneal (i.p.) administration of morin (25-100 mg/kg), haloperidol (1 mg/kg) and risperidone (0.5 mg/kg) alone or in combination with ketamine (20 mg/kg, i.p.) for 10 days. Neurobehavioral and schizophrenia-like activities consisting of open-field (positive symptoms), Y-maze, novel-object recognition (cognitive symptoms), social interaction (negative symptoms) tests were assessed. Also, wood-block catalepsy and rota-rod tests were employed to evaluate extrapyramidal side effects of morin. Thereafter, brain levels of biomarkers of oxidative, nitrergic and acetylcholinesterase alterations as well as histomorphological changes in the striatum and prefrontal-cortex were determined. Administration of morin and risperidone alone but not haloperidol significantly (p > 0.05) prevented ketamine-induced hyperlocomotion, social withdrawal and cognitive impairments relative to controls, and were devoid of extrapyramidal side effects. Morin alone or in combination with ketamine significantly increased glutathione concentration, superoxide dismutase and catalase activities compared with saline- or ketamine-treated mice. Moreover, morin alone or in combination with ketamine also significantly decreased malondialdehyde, nitrite and acetylcholinesterase alterations in mice brains. Furthermore, morin prevented ketamine-induced brain neuronal alterations in the striatum and prefrontal-cortex. Together, our findings suggest that morin may demonstrate antipsychotic-like therapeutic effect via modulation of oxidative/nitrergic, cholinergic actions and neuroprotection.

A Role for Prefrontal Cortical NMDA Receptors in Murine Alcohol-Heightened Aggression

Alcohol is associated with nearly half of all violent crimes committed in the United States; yet, a potential neural basis for this type of pathological aggression remains elusive. Alcohol may act on N-methyl-d-aspartate receptors (NMDARs) within cortical circuits to impede processing and to promote aggression. Here, male mice were characterized as alcohol-heightened (AHAs) or alcohol non-heightened aggressors (ANAs) during resident-intruder confrontations after self-administering 1.0 g/kg alcohol (6% w/v) or water. Alcohol produced a pathological-like pattern of aggression in AHAs; these mice shifted their bites to more vulnerable locations on the body of a submissive animal, including the anterior back and ventrum after consuming alcohol. In addition, through immunoblotting, we found that AHAs overexpressed the NMDAR GluN2D subunit in the prefrontal cortex (PFC) as compared to ANAs while the two phenotypes expressed similar levels of GluN1, GluN2A and GluN2B. After identifying several behavioral and molecular characteristics that distinguish AHAs from ANAs, we tested additional mice for their aggression following preferential antagonism of GluN2D-containing NMDARs. In these experiments, groups of AHAs and ANAs self-administered 1.0 g/kg alcohol (6% w/v) or water before receiving intraperitoneal (i.p.) doses of ketamine or memantine, or infusions of memantine directly into the prelimbic (PLmPFC) or infralimbic medial PFC (ILmPFC). Moderate doses of IP ketamine, IP memantine, or intra-PLmPFC memantine increased aggression in AHAs, but only in the absence of alcohol. Prior alcohol intake blocked the pro-aggressive effects of ketamine or memantine. In contrast, only memantine, administered systemically or intra-PLmPFC, interacted with prior alcohol intake to escalate aggression in ANAs. Intra-ILmPFC memantine had no effect on aggression in either AHAs or ANAs. In sum, this work illustrates a potential role of GluN2D-containing NMDARs in the PLmPFC in alcohol-heightened aggression. GluN2D-containing NMDARs are highly expressed on cortical parvalbumin-containing interneurons, suggesting that, in a subset of individuals, alcohol may functionally alter signal integration within cortical microcircuits to dysregulate threat reactivity and promote aggression. This work suggests that targeting GluN2D-NMDARs may be of use in reducing the impact of alcohol-related violence in the human population.

Effect of ketamine administration, alone and in combination with E-6837, on climbing behavior

Some types of schizophrenia have been associated with repetitive movements lacking specific purpose, also known as stereotyped behavior. Dopamine agonists (D2) and noncompetitive N-methyl-D-aspartate receptor antagonists (e.g. ketamine) have been administered in rodent models to induce stereotyped behavior that resembles some motor symptoms of schizophrenia. Recently, a relationship has been found between 5-HT6 receptors (5-HT6Rs) and dopaminergic activity. The present study evaluates the effect of ketamine (5 and 10 mg/kg), alone and in combination with the 5-HT6R agonist E-6837, on the climbing behavior of male mice. Ketamine was administered with an acute (1 day) and subchronic (5 day) scheme. Later, these doses and schemes were combined with an acute scheme of E-6837 (5 and 10 mg/kg). With both the acute and the subchronic schemes, ketamine increased climbing behavior at a dose of 10 mg/kg, and this effect was reversed by E-6837 (at 5 and 10 mg/kg). The present results suggest that there is an interaction between N-methyl-D-aspartate and 5-HT6 receptors in the regulation of climbing behavior. Further research is necessary to provide more evidence on this interaction.

Comparative effects of sertraline, haloperidol or olanzapine treatments on ketamine-induced changes in mouse behaviours

Effects of sertraline, haloperidol or olanzapine administration on ketamine-induced behaviours in mice were examined. The aim was to ascertain the degree of reversal of such behaviours by sertraline, and compare its effectiveness to haloperidol and olanzapine. Ten-week old mice (N = 120) were equally divided into main groups; 1 (open-field, radial-arm maze and elevated plus maze {EPM} tests), and 2 (social interaction test). Mice in each main group were assigned into six groups of ten (n = 10) each. Group 1 received intraperitoneal (i.p) injection of vehicle, while groups 2-6 received i.p ketamine at 15 mg/kg daily for 10 days. From day 11 to 24, mice in group 1 (vehicle) were given distilled water (i.p at 2 ml/kg and oral at 10 ml/kg), group 2 (ketamine control) received daily i.p ketamine and oral distilled water; while animals in groups 3-6 received daily i.p. ketamine and oral haloperidol (4 mg/kg), olanzapine (2 mg/kg), or one of two doses of sertraline (SERT) (2.5 or 5 mg/kg), respectively. Treatments were administered daily, and behaviours assessed on days 11 and 24. Results showed that repeated ketamine administration caused hyperlocomotion, increased self-grooming, memory loss and social withdrawal. Administration of sertraline (both doses), haloperidol, and olanzapine reversed ketamine-induced behavioural changes. However, in the EPM, sertraline and olanzapine were anxiolytic, while haloperidol was anxiogenic. Sertraline's effect on behaviours tested was comparable to olanzapine and better than haloperidol. In conclusion, this study shows that sertraline's ability to counteract ketamine-induced behavioural changes in mice is comparable to known antipsychotics.

Is Forced Swimming Immobility a Good Endpoint for Modeling Negative Symptoms of Schizophrenia? - Study of Sub-Anesthetic Ketamine Repeated Administration Effects

Immobility time in the forced swimming has been described as analogous to emotional blunting or apathy and has been used for characterizing schizophrenia animal models. Several clinical studies support the use of NMDA receptor antagonists to model schizophrenia in rodents. Some works describe the effects of ketamine on immobility behavior but there is variability in the experimental design used leading to controversial results. In this study, we evaluated the effects of repeated administration of ketamine sub-anesthetic doses in forced swimming, locomotion in response to novelty and novel object recognition, aiming a broader evaluation of the usefulness of this experimental approach for modeling schizophrenia in mice. Ketamine (30 mg/kg/day i.p. for 14 days) induced a not persistent decrease in immobility time, detected 24h but not 72h after treatment. This same administration protocol induced a deficit in novel object recognition. No change was observed in mice locomotion. Our results confirm that repeated administration of sub-anesthetic doses of ketamine is useful in modeling schizophrenia-related behavioral changes in mice. However, the immobility time during forced swimming does not seem to be a good endpoint to evaluate the modeling of negative symptoms in NMDAR antagonist animal models of schizophrenia.

Effect of clozapine on ketamine-induced deficits in attentional set shift task in mice

RATIONALE

Clozapine (CLZ) is an effective treatment for schizophrenia, producing improvements in both negative symptoms and cognitive impairments. Cognitive impairments can be modelled in animals by ketamine (KET) and assessed using the attentional set-shift task (ASST).

OBJECTIVE

Our first aim was to determine whether CLZ improves cognitive function and reverses KET-induced cognitive impairments using the ASST. Our second aim was to assess dose dependency of these effects.

RESULTS

Our findings demonstrate that acute as well as sub-chronic administration of KET cause cognitive deficits observed as increase in number of trails and errors to reach the criterion in the EDS phase. CLZ 0.3 mg/kg reversed the effects of both acute and sub-chronic KET, with no effects on locomotor activity. However, clozapine's effect after sub-chronic administration of dose 0.3 mg/kg was not as explicit as in the case of acute treatment. Moreover, administration of 1 mg/kg CLZ to KET-treated mice induced or enhanced deficits in the extra-dimensional shift phase compared to 1 mg/kg CLZ administration to mice not receiving KET. Locomotor activity test showed sedation effects of CLZ 1 mg/kg after acute treatment; therefore, effect of CLZ 1 mg/kg on KET-induced cognitive deficits was not evaluated in the attentional set-shift task (ASST) test.

CONCLUSIONS

The present findings support dose-dependent effects of CLZ to reverse KET-induced cognitive deficits. The observed dose dependency may be mediated by activation of different receptors, including monomers and/or heterodimers.

Probable mechanisms involved in the antipsychotic-like activity of methyl jasmonate in mice

Psychosis is a chronic neuropsychiatric disorder that affects millions of individuals worldwide and impairs the quality of life and productivity of the patients. The clinical efficacy of antipsychotic drugs has been compromised by adverse effects, relapse, and therapeutic failures, thus necessitating search for alternative agents. Methyl jasmonate (MJ) is a bioactive compound reported to have beneficial effects in various neurological disorders. This study was undertaken to investigate the antipsychotic-like effects of MJ in mice. Male Swiss mice were pretreated intraperitoneally with MJ (25-100 mg/kg) or vehicle (10 mL/kg) 60 min prior to bromocriptine (5 mg/kg) or acute injection of ketamine (10 mg/kg). Thereafter, each mouse was observed for stereotype behaviors for 2 min at 10, 15, 20, 30, and 45 min post-bromocriptine injection. Another set of mice received MJ (25-100 mg/kg) or vehicle (10 mL/kg) 60 min after chronic ketamine injection (20 mg/kg, i.p) once daily for 14 consecutive days. Afterwards, locomotor activity and memory function in this sequence were evaluated using open field and Y-maze tests. The levels of malondialdehyde (MDA) and glutathione (GSH) and activity of catalase and superoxide dismutase (SOD) in the brain were determined. MJ significantly inhibited stereotypy behavior induced by bromocriptine or acute ketamine injection, which suggest antipsychotic-like activity. It also attenuated hyper-locomotion and memory deficits induced by chronic injection of ketamine in mice. The increased oxidative stress as shown by the altered brain levels of MDA, GSH, and activity of antioxidant enzymes induced by chronic injection of ketamine was reduced by MJ. Taken together, these findings suggest that MJ demonstrated antipsychotic-like property via mechanism related to its antioxidant property and interference with dopaminergic neurotransmission.

The preventive effects of ascorbic acid supplementation on locomotor and acetylcholinesterase activity in an animal model of schizophrenia induced by ketamine

Studies have shown that schizophrenic patients seem to have nutritional deficiencies. Ascorbic acid (AA) has an important antioxidant effect and neuromodulatory properties. The aim of this study was to evaluate the effects of AA on locomotor activity and the acetylcholinesterase activity (AChE) in an animal model of schizophrenia (SZ). Rats were supplemented with AA (0.1, 1, or 10 mg/kg), or water for 14 days (gavage). Between the 9th and 15th days, the animals received Ketamine (Ket) (25 mg/kg) or saline (i.p). After the last administration (30 min) rats were subjected to the behavioral test. Brain structures were dissected for biochemical analysis. There was a significant increase in the locomotor activity in Ket treated. AA prevented the hyperlocomotion induced by ket. Ket also showed an increase of AChE activity within the prefrontal cortex and striatum prevented by AA. Our data indicates an effect for AA in preventing alterations induced by Ket in an animal model of SZ, suggesting that it may be an adjuvant approach for the development of new therapeutic strategies within this psychiatric disorder.

Nardostachys jatamansi Targets BDNF-TrkB to Alleviate Ketamine-Induced Schizophrenia-Like Symptoms in Rats

OBJECTIVE

Schizophrenia, a common neurological disorder appearing in the late teens or early adulthood, is characterized by disorganized thinking, behaviour, and perception of emotions. Aberrant N-methyl-D-aspartate (NMDA) receptor-mediated synaptic plasticity is a major pathological event here due to dysfunction of dopamine and glutamate transmission at NMDA receptors. De-regulated brain-derived neurotrophic factor (BDNF), i.e., its signalling through the tropomyosin receptor kinase B (TrkB) receptor, is a major feature of schizophrenia. With recent global awareness of traditional plant medicines in reducing side effects, the aim of our study was to evaluate the efficacy of the ethanolic root extract of a herb belonging to the Valerianacea family, Nardostachys jatamansi, against ketamine-induced schizophrenia-like model in rats.

METHODS

The effect of the N. jatamansi drug (oral dosage of 500 mg/kg body weight for 14 days) in ketamine-administered male Wistar albino rats (30 mg/kg body weight for 5 days) on modulating behaviour and the level of neurotransmitters like dopamine and glutamate was studied in whole-brain homogenates, and its influence on BDNF and TrkB levels in 2 relevant brain regions, the hippocampus and prefrontal cortex, was assessed.

RESULTS

We observed that N. jatamansi treatment exhibited encouraging results in the modulation of ketamine-induced schizophrenia-like behaviours, principally the positive symptoms. Our drug both significantly upregulated the glutamate level and downregulated the dopamine level in whole-brain homogenates and retained the normal levels of BDNF (in the hippocampus but not in the prefrontal cortex) and TrkB (in both hippocampus and prefrontal cortex) induced by ketamine in rats.

CONCLUSION

These findings suggest a neuroprotective effect of the ethanolic root extract of N. jatamansi against ketamine-induced schizophrenia-like symptoms in rats; possibly, regarding its effect on TrkB signalling. Further research is warranted in the treatment of schizophrenic symptoms.

The Evaluation of Folic Acid-Deficient or Folic Acid-Supplemented Diet in the Gestational Phase of Female Rats and in Their Adult Offspring Subjected to an Animal Model of Schizophrenia

Although folic acid (FA) supplementation is known to influence numerous physiological functions, especially during pregnancy, little is known about its direct effects on the mothers' health. However, this vitamin is essential for the health of the mother and for the normal growth and development of the fetus. Thus, the aim of this study was (1) to evaluate the cognitive effects and biochemical markers produced by the AIN-93 diet (control), the AIN-93 diet supplemented with different doses of FA (5, 10, and 50 mg/kg), and a FA-deficient diet during pregnancy and lactation in female mother rats (dams) and (2) to evaluate the effect of maternal diets on inflammatory parameters in the adult offspring which were subjected to an animal model of schizophrenia (SZ) induced by ketamine (Ket). Our study demonstrated through the Y-maze test that rats subjected to the FA-deficient diet showed significant deficits in spatial memory, while animals supplemented with FA (5 and 10 mg/kg) showed no deficit in spatial memory. Our results also suggest that the rats subjected to the FA-deficient diet had increased levels of carbonylated proteins in the frontal cortex and hippocampus and also increased plasma levels of homocysteine (Hcy). Folate was able to prevent cognitive impairments in the rats supplemented with FA (5 and 10 mg/kg), data which may be attributed to the antioxidant effect of the vitamin. Moreover, FA prevented protein damage and elevations in Hcy levels in the rats subjected to different doses of this vitamin (5, 10, and 50 mg/kg). We verified a significant increase of the anti-inflammatory cytokine (interleukin-4 (IL-4)) and a reduction in the plasma levels of proinflammatory cytokines (interleukin-6 (IL-6)) and TNF-α) in the dams that were subjected to the diets supplemented with FA (5, 10, and 50 mg/kg), showing the possible anti-inflammatory effects of FA during pregnancy and lactation. In general, we also found that in the adult offspring that were subjected to an animal model of SZ, FA had a protective effect in relation to the levels of IL-4, IL-6, and TNF-α, which indicates that the action of FA persisted in the adult offspring, since FA showed a lasting effect on the inflammatory response, which was similar in both the dams and their offspring. In conclusion, the importance of supplementation with FA during pregnancy and lactation should be emphasized, not only for the benefit of the offspring but also for the health of the mother. All this is due to the considerable protective effect of this vitamin against oxidative damage, cognitive impairment, hyperhomocysteinemia, immune function, and also its ability in preventing common processes in post-pregnancy stages, as well as in reducing the risks of neurodevelopmental disorders and enhancing fetal immune development.

Reversal of schizophrenia-like symptoms and immune alterations in mice by immunomodulatory drugs

Immune dysregulation observed in schizophrenia alters tryptophan metabolism. Tryptophan metabolism is triggered by indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO). Tryptophan is converted to quinolinic acid, a potent neurotoxin, and to kynurenic acid, an NMDA antagonist. 1-Methyl-D-tryptophan (MDT) inhibits IDO. Melatonin is metabolized by IDO while inhibiting TDO. We evaluated the reversal of ketamine-induced schizophrenia-like behavioral and neurochemical alterations in mice by the administration of MDT (20 or 40 mg/kg, i.p.) or melatonin (15 mg/kg, per os). Oxidative stress and inflammatory alterations, i.e. myeloperoxidase activity (MPO), reduced glutathione (GSH), lipid peroxidation (LPO) and interleukin (IL)-4 and IL-6 were measured in the prefrontal cortex (PFC), hippocampus and striatum. Risperidone was used as standard antipsychotic. Ketamine triggered positive- (PPI deficits and hyperlocomotion), cognitive- (working memory deficits) and negative (social interaction deficits) schizophrenia-like symptoms. These symptoms were accompanied by increased MPO activity, decreased GSH and increased LPO in all brain areas and increments in hippocampal IL-4 and IL-6. MDT and melatonin reversed all ketamine-induced behavioral alterations. Risperidone did not reverse working memory deficits. MDT and melatonin reversed alterations in MPO activity and GSH levels. LP was reversed only by melatonin and risperidone. Risperidone could not reverse MPO alterations in the PFC and striatum. All drugs reversed the alterations in IL-4 and IL-6. The hippocampus and striatum of ketamine+melatonin-treated animals had lower levels of IL-6. Our findings provide further preclinical evidence that immune-inflammatory and oxidative pathways are involved in schizophrenia and that targeting these pathways is a valid treatment option in schizophrenia.

Neuroprotective effects of the ethanol stem bark extracts of Terminalia ivorensis in ketamine-induced schizophrenia-like behaviors and oxidative damage in mice

CONTEXT

Schizophrenia is a heterogenous neurological disorder, which has been hypothetically linked to oxidative imbalance and associated behavioral perturbations. Preliminary evidence from animal models predictive of human psychosis suggests that Terminalia ivorensis A. Chev. (Combretaceae) has antipsychotic-like activity in mice.

OBJECTIVE

This study investigates the neuroprotective property of the ethanol stem bark extracts of T. ivorensis (EETI) in reversal treatment of ketamine-induced schizophrenia-like behaviors and oxidative alteration in adult male Swiss albino mice.

MATERIALS AND METHODS

Animals were divided into six treatment groups (n = 5). Animals received distilled water or ketamine (20 mg/kg) once daily intraperitoneally (i.p.) for 14 days, and from the 8th to the 14th day, they were treated with EETI (125, 250 or 500 mg/kg), risperidone (RIS) or vehicle orally once daily. Behaviors related to positive (locomotor activity) and cognitive (Y maze) symptoms of schizophrenia were assessed. Glutathione (GSH) levels, superoxide dismutase (SOD) and catalase (CAT) activities, including malondialdehyde (MDA) concentration were measured in mice whole brains.

RESULT

The LD₅₀ of EETI was 2236.06 mg/kg, p.o. body weight. EETI (125, 250 or 500 mg/kg, p.o.) demonstrated significant (p < 0.05) inhibition of ketamine-induced hyperlocomotion and cognitive dysfunction. The extract decreased MDA concentration (39.0, 62.6 and 67.5%) in a dose-dependent manner. Moreover, EETI significantly (p < 0.05) reversed the depletion of GSH, and increased activities of SOD and CAT in brain tissues.

DISCUSSION AND CONCLUSION

These findings suggest that EETI probably exert its antipsychotic-like activity, via a neuroprotective compensatory mechanism of action, and as such, could be relevant in the management of schizophrenia.

Effect of folic acid on oxidative stress and behavioral changes in the animal model of schizophrenia induced by ketamine

Recent studies have shown benefits for the supplementation of folic acid in schizophrenic patients. The aim of this study was to evaluate the effects of folic acid addition on adult rats, over a period of 7 or 14 days. It also sets out to verify any potential protective action using an animal model of schizophrenia induced by ketamine, in behavioral and biochemical parameters. This study used two protocols (acute and chronic) for the administration of ketamine at a dose of 25 mg/kg (i.p.). The folic acid was given by oral route in doses of 5, 10 and 50 mg/kg, once daily, for 7 and/or 14 days in order to compare the protective effects of folic acid. Thirty minutes after the last administration of ketamine, the locomotor and social interaction activities were evaluated, and immediately the brain structure were removed for biochemical analysis. In this study, ketamine was administered in a single dose or in doses over the course of 7 days increasing the animal's locomotion. This study showed that the administration of folic acid over 7 days was unable to prevent hyper locomotion. In contrast, folic acid (10 and 50 mg/kg) administrated over a period of 14 days, was able to partially prevent the hyper locomotion. Our data indicates that both acute and chronic administrations of ketamine increased the time to first contact between the animals, while the increased latency for social contact was completely prevented by folic acid (5, 10 and 50 mg/kg). Chronic and acute administrations of ketamine also increased lipid peroxidation and protein carbonylation in brain. Folic acid (10 and 50 mg/kg) supplements showed protective effects on the oxidative damage found in the different brain structures evaluated. All together, the results indicate that nutritional supplementation with folic acid provides promising results in an animal model of schizophrenia induced by ketamine.

Region-specific effects of repeated ketamine administration on the presynaptic GABAergic neurochemistry in rat brain

A growing body of evidence indicates that clinical use of ketamine as a promising antidepressant can be accompanied by psychotic-like side effects. Although, the generation of such effects is thought to be attributed to dysfunction of prefrontal GABAergic interneurons, the mechanism underlying ketamine's propsychotic-like action is not fully understood. Due to wide spectrum of behavioral abnormalities, it is hypothesized that ketamine action is not limited to only cortical GABA metabolism but may also involve alterations in other functional brain areas. To test it, we treated rats with ketamine (30 mg/kg, i.p.) for 5 days, and next we analyzed GABA metabolizing enzymes in cortex, cerebellum, hippocampus and striatum. Our results demonstrated that diminished GAD67 expression in cortex, cerebellum (by ∼60%) and in hippocampus (by ∼40%) correlated with lowered protein level in these areas. The expression of GAD65 isoform decreased by ∼45% in striatum, but pronounced increase by ∼90% was observed in hippocampus. Consecutively, reduction in glutamate decarboxylase activity and GABA concentration were detected in cortex, cerebellum and striatum, but not in hippocampus. Ketamine administration decreased GABA transaminase protein in cortex and striatum (by ∼50% and 30%, respectively), which was reflected in diminished activity of the enzyme. Also, a significant drop in succinic semialdehyde dehydrogenase activity in cortex, cerebellum and striatum was present. These data suggest a reduced utilization of GABA for energetic purposes. In addition, we observed synaptic GABA release to be reduced by ∼30% from striatal terminals. It correlated with lowered KCl-induced Ca(2+) influx and decreased amount of L-type voltage-dependent calcium channel. Our results indicate that unique changes in GABA metabolism triggered by chronic ketamine treatment in functionally distinct brain regions may be involved in propsychotic-like effects of this drug.

Plasma membrane Ca(2+)-ATPase is a novel target for ketamine action

Ketamine, a high affinity uncompetitive antagonist of voltage-dependent NMDA receptor, has been used for years as a dissociative anesthetic. Although the drug is considered as safe and well-tolerable, it is now evident that it can exert dose-dependent multidirectional effects acting on different cellular targets and pathways. The latest clinical studies also demonstrated its promising antidepressant action. However, the widespread use of this drug in humans is largely limited by a broad range of cognitive adverse effects that resemble some core symptoms of schizophrenia. In line with the hypothesis of unifying role of calcium in schizophrenia symptomology, we used ketamine-induced rat model of experimental psychosis to study the effect of 5-day ketamine treatment (30 mg/kg, ip) on the activity of plasma membrane Ca(2+)-ATPase. Whereas no change in a total amount of the enzyme in cortical synaptosomal membranes was observed, a decrease by ∼50% in hydrolytic activity, as well as lowered phosphointermediate formation were detected. Moreover, ketamine action appeared to be isoform-independent. The experiments on intact Ca(2+)-ATPase purified from vehicle-treated rat cortex revealed dose-dependent inhibition of enzymatic activity. Furthermore, ketamine decreased, but not eliminated, the stimulation by calmodulin. The inhibitory effect, although much weaker, was also evident for truncated form of calcium pump obtained following digestion by trypsin. Our results indicate that plasma membrane Ca(2+)-ATPase is a novel target for ketamine and putative interaction sites may involve central catalytic loop and calmodulin-binding domain.

Maternal deprivation disrupts mitochondrial energy homeostasis in the brain of rats subjected to ketamine-induced schizophrenia

Maternal deprivation (MD) appears to be one of the environmental factors involved in the pathophysiology of schizophrenia. A widely used animal model of the schizophrenia involves the administration of ketamine, a dissociative anesthetic, NMDA receptors noncompetitive antagonist, that induce symptoms such as schizophrenia. To clarify the molecular mechanism of schizophrenia induced by MD, we investigated alterations in energetic metabolism, oxidative stress and neurotrophic factor levels in the brain of rats following MD and/or a single administration of ketamine during adulthood. Male Wistar rats were subjected to MD for 10 days. Additionally, these animals received acute ketamine (5, 15 or 25 mg/kg by intraperitoneal route, i.p.) during adulthood, and 30 min later, they were killed and the prefrontal cortex (PFC), the hippocampus and the striatum were removed for molecular analyses. Ketamine 25 mg/kg and/or MD and Ketamine 15 and 5 mg/kg with MD decreased the creatine kinase (CK) activity in the hippocampus. The enzyme activity of succinate dehydrogenase (SDH) in the Krebs cycle had increased in the striatum following the administration of ketamine 25 mg/kg, MD per se or MD plus ketamine 5 and 15 mg/kg. MD per se or MD combined with ketamine in different doses increased the activity of mitochondrial complexes. The PFC of animals subjected to MD and administered with ketamine 5 mg/kg exhibited increased protein carbonyl content. In the hippocampus, ketamine 15 mg/kg, ketamine 25 mg/kg and MD each increased the carbonyl content. In the striatum, the TBARS levels were increased by the administration of ketamine 25 mg/kg. Finally, in the hippocampus, MD alone or in combination with ketamine reduced the Nerve Growth Factor (NGF) levels; however, the Brain-derived Neurotrophic Factor (BDNF) levels were unaltered. In the present study, we suggest that MD increased the risk of psychotic symptoms in adulthood, altering different parameters of energy and oxidative stress. Our results suggest that adverse experiences occurring early in life may sensitize specific neurocircuits to subsequent stressors, inducing vulnerability, and may help us understand the pathophysiological mechanisms involved in this disorder.

Effects of omega-3 supplementation on interleukin and neurotrophin levels in an animal model of schizophrenia

ABSTRACTNew studies suggest that polyunsaturated fatty acids, such as omega-3, may reduce the symptoms of schizophrenia. The present study evaluated the preventive effect of omega-3 on interleukines (IL) and neurotrophin brain-derived neurotrophic factor (BDNF) levels in the brains of young rats subjected to a model of schizophrenia. Treatment was performed over 21 days, starting on the 30th day of rat's life. After 14 days of treatment with omega-3 or vehicle, a concomitant treatment with saline or ketamine (25 mg/kg) was started and maintained until the last day of the experiment. BDNF levels in the rat's prefrontal cortex were decreased at 1 h and 24 h after the last administration of ketamine, whereas the group administered with ketamine and omega-3 showed a decrease in BDNF levels only after 24 h. In contrast, both interventions induced similar responses in levels of IL-1β and IL6. These findings suggest that the similarity of IL-1β and IL6 levels in our experimental groups is due to the mechanism of action of ketamine on the immune system. More studies have to be carried out to explain this pathology. In conclusion, according to previous studies and considering the current study, we could suggest a prophylactic role of omega-3 against the outcome of symptoms associated with schizophrenia.

Alpha-lipoic acid alone and combined with clozapine reverses schizophrenia-like symptoms induced by ketamine in mice: Participation of antioxidant, nitrergic and neurotrophic mechanisms

Oxidative stress has important implications in schizophrenia. Alpha-lipoic acid (ALA) is a natural antioxidant synthesized in human tissues with clinical uses. We studied the effect of ALA or clozapine (CLZ) alone or in combination in the reversal of schizophrenia-like alterations induced by ketamine (KET). Adult male mice received saline or KET for 14 days. From 8th to 14th days mice were additionally administered saline, ALA (100 mg/kg), CLZ 2.5 or 5 mg/kg or the combinations ALA+CLZ2.5 or ALA+CLZ5. Schizophrenia-like symptoms were evaluated by prepulse inhibition of the startle (PPI) and locomotor activity (positive-like), social preference (negative-like) and Y maze (cognitive-like). Oxidative alterations (reduced glutathione - GSH and lipid peroxidation - LP) and nitrite in the prefrontal cortex (PFC), hippocampus (HC) and striatum (ST) and BDNF in the PFC were also determined. KET caused deficits in PPI, working memory, social interaction and hyperlocomotion. Decreased levels of GSH, nitrite (HC) and BDNF and increased LP were also observed in KET-treated mice. ALA and CLZ alone reversed KET-induced behavioral alterations. These drugs also reversed the decreases in GSH (HC) and BDNF and increase in LP (PFC, HC and ST). The combination ALA+CLZ2.5 reversed behavioral and some neurochemical parameters. However, ALA+CLZ5 caused motor impairment. Therefore, ALA presented an antipsychotic-like profile reversing KET-induced positive- and negative-like symptoms. The mechanism partially involves antioxidant, neurotrophic and nitrergic pathways. The combination of ALA+CLZ2.5 improved most of the parameters evaluated in this study without causing motor impairment demonstrating, thus, that possibly when combined with ALA a lower dose of CLZ is required.

The hippocampo-prefrontal pathway: a possible therapeutic target for negative and cognitive symptoms of schizophrenia

The hippocampo-prefrontal (H-PFC) pathway has been linked to cognitive and emotional disturbances in several psychiatric disorders including schizophrenia. Preclinical evidence from the NMDA receptor antagonism rodent model of schizophrenia shows severe pathology selective to the H-PFC pathway. It is speculated that there is an increased excitatory drive from the hippocampus to the prefrontal cortex due to dysfunctions in the H-PFC plasticity, which may serve as the basis for the behavioral consequences observed in this rodent model. Thus, the H-PFC pathway is currently emerging as a promising therapeutic target for the negative and cognitive symptom clusters of schizophrenia. Here, we have reviewed the physiological, pharmacological and functional characteristics of the H-PFC pathway and we propose that allosteric activation of glutamatergic and cholinergic neurotransmission can serve as a plausible therapeutic approach.

Ketamine administration during the second postnatal week induces enduring schizophrenia-like behavioral symptoms and reduces parvalbumin expression in the medial prefrontal cortex of adult mice

Dysfunctions in the GABAergic system are considered a core feature of schizophrenia. Pharmacological blockade of NMDA receptors (NMDAR), or their genetic ablation in parvalbumin (PV)-expressing GABAergic interneurons can induce schizophrenia-like behavior in animals. NMDAR-mediated currents shape the maturation of GABAergic interneurons during a critical period of development, making transient blockade of NMDARs during this period an attractive model for the developmental changes that occur in the course of schizophrenia's pathophysiology. Here, we examined whether developmental administration of the non-competitive NMDAR antagonist ketamine results in persistent deficits in PFC-dependent behaviors in adult animals. Mice received injections of ketamine (30mg/kg) on postnatal days (PND) 7, 9 and 11, and then tested on a battery of behavioral experiments aimed to mimic major symptoms of schizophrenia in adulthood (between PND 90 and 120). Ketamine treatment reduced the number of cells that expressed PV in the PFC by ∼60% as previously described. Ketamine affected performance in an attentional set-shifting task, impairing the ability of the animals to perform an extradimensional shift to acquire a new strategy. Ketamine-treated animals showed deficits in latent inhibition, novel-object recognition and social novelty detection compared to their SAL-treated littermates. These deficits were not a result of generalized anxiety, as both groups performed comparably on an elevated plus maze. Ketamine treatment did not cause changes in amphetamine-induced hyperlocomotion that are often taken as measures for the positive-like symptoms of the disorder. Thus, ketamine administration during development appears to be a useful model for inducing cognitive and negative symptoms of schizophrenia.