Ketamine-induced changes in rat behaviour: A possible animal model of schizophrenia

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.

Overview on cognitive impairment in psychotic disorders: From impaired microcircuits to dysconnectivity

Schizophrenia's cognitive deficits, often overshadowed by positive symptoms, significantly contribute to the disorder's morbidity. Increasing attention highlights these deficits as reflections of neural circuit dysfunction across various cortical regions. Numerous connectivity alterations linked to cognitive symptoms in psychotic disorders have been reported, both at the macroscopic and microscopic level, emphasizing the potential role of plasticity and microcircuits impairment during development and later stages. However, the heterogeneous clinical presentation of cognitive impairment and diverse connectivity findings pose challenges in summarizing them into a cohesive picture. This review aims to synthesize major cognitive alterations, recent insights into network structural and functional connectivity changes and proposed mechanisms and microcircuit alterations underpinning these symptoms, particularly focusing on neurodevelopmental impairment, E/I balance, and sleep disturbances. Finally, we will also comment on some of the most recent and promising therapeutic approaches that aim to target these mechanisms to address cognitive symptoms. Through this comprehensive exploration, we strive to provide an updated and nuanced overview of the multiscale connectivity impairment underlying cognitive impairment in psychotic disorders.

Large-scale coupling of prefrontal activity patterns as a mechanism for cognitive control in health and disease: evidence from rodent models

Cognitive control of behavior is crucial for well-being, as allows subject to adapt to changing environments in a goal-directed way. Changes in cognitive control of behavior is observed during cognitive decline in elderly and in pathological mental conditions. Therefore, the recovery of cognitive control may provide a reliable preventive and therapeutic strategy. However, its neural basis is not completely understood. Cognitive control is supported by the prefrontal cortex, structure that integrates relevant information for the appropriate organization of behavior. At neurophysiological level, it is suggested that cognitive control is supported by local and large-scale synchronization of oscillatory activity patterns and neural spiking activity between the prefrontal cortex and distributed neural networks. In this review, we focus mainly on rodent models approaching the neuronal origin of these prefrontal patterns, and the cognitive and behavioral relevance of its coordination with distributed brain systems. We also examine the relationship between cognitive control and neural activity patterns in the prefrontal cortex, and its role in normal cognitive decline and pathological mental conditions. Finally, based on these body of evidence, we propose a common mechanism that may underlie the impaired cognitive control of behavior.

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.

Sex-Dependent Attentional Impairments in a Subchronic Ketamine Mouse Model for Schizophrenia

Background

The development of more effective treatments for schizophrenia targeting cognitive and negative symptoms has been limited, partly due to a disconnect between rodent models and human illness. Ketamine administration is widely used to model symptoms of schizophrenia in both humans and rodents. In mice, subchronic ketamine treatment reproduces key dopamine and glutamate dysfunction; however, it is unclear how this translates into behavioral changes reflecting positive, negative, and cognitive symptoms.

Methods

In male and female mice treated with either subchronic ketamine or saline, we assessed spontaneous and amphetamine-induced locomotor activity to measure behaviors relevant to positive symptoms, and used a touchscreen-based progressive ratio task of motivation and the rodent continuous performance test of attention to capture specific negative and cognitive symptoms, respectively. To explore neuronal changes underlying the behavioral effects of subchronic ketamine treatment, we quantified expression of the immediate early gene product, c-Fos, in key corticostriatal regions using immunofluorescence.

Results

We showed that spontaneous locomotor activity was unchanged in male and female subchronic ketamine-treated animals, and amphetamine-induced locomotor response was reduced. Subchronic ketamine treatment did not alter motivation in either male or female mice. In contrast, we identified a sex-specific effect of subchronic ketamine on attentional processing wherein female mice performed worse than control mice due to increased nonselective responding. Finally, we showed that subchronic ketamine treatment increased c-Fos expression in prefrontal cortical and striatal regions, consistent with a mechanism of widespread disinhibition of neuronal activity.

Conclusions

Our results highlight that the subchronic ketamine mouse model reproduces a subset of behavioral symptoms that are relevant for schizophrenia.

Sub-Chronic Ketamine Administration Increases Dopamine Synthesis Capacity in the Mouse Midbrain: a Preclinical In Vivo PET Study

PURPOSE

There is robust evidence that people with schizophrenia show elevated dopamine (DA) synthesis capacity in the striatum. This finding comes from positron emission tomography (PET) studies using radiolabelled l-3,4-dihydroxyphenylalanine (18F-DOPA). DA synthesis capacity also appears to be elevated in the midbrain of people with schizophrenia compared to healthy controls. We therefore aimed to optimise a method to quantify 18F-DOPA uptake in the midbrain of mice, and to utilise this method to quantify DA synthesis capacity in the midbrain of the sub-chronic ketamine model of schizophrenia-relevant hyperdopaminergia.

PROCEDURES

Adult male C57Bl6 mice were treated daily with either ketamine (30 mg/kg, i.p.) or vehicle (saline) for 5 days. On day 7, animals were administered 18F-DOPA (i.p.) and scanned in an Inveon PET/CT scanner. Data from the saline-treated group were used to optimise an atlas-based template to position the midbrain region of interest and to determine the analysis parameters which resulted in the greatest intra-group consistency. These parameters were then used to compare midbrain DA synthesis capacity (KiMod) between ketamine- and saline-treated animals.

RESULTS

Using an atlas-based template to position the 3.7 mm3 midbrain ROI with a T*-Tend window of 15-140 min to estimate KiMod resulted in the lowest intra-group variability and moderate test-retest agreement. Using these parameters, we found that KiMod was elevated in the midbrain of ketamine-treated animals in comparison to saline-treated animals (t(22) = 2.19, p = 0.048). A positive correlation between DA synthesis capacity in the striatum and the midbrain was also evident in the saline-treated animals (r2 = 0.59, p = 0.005) but was absent in ketamine-treated animals (r2 = 0.004, p = 0.83).

CONCLUSIONS

Using this optimised method for quantifying 18F-DOPA uptake in the midbrain, we found that elevated striatal DA synthesis capacity in the sub-chronic ketamine model extends to the midbrain. Interestingly, the dysconnectivity between the midbrain and striatum seen in this model is also evident in the clinical population. This model may therefore be ideal for assessing novel compounds which are designed to modulate pre-synaptic DA synthesis capacity.

Comparison of sleep deprivation and a low dose of ketamine on sleep and the electroencephalogram in Brown Norway rats

Ketamine is known for its antidepressant effects, but the mechanism underlying this effect remains largely unclear. In contrast to most antidepressant drugs, the action of ketamine is rapid, suggesting a different mode of action. A rapid antidepressant effect is also observed following sleep deprivation (SD). In the present study, we aimed to evaluate the effect of a 6-h SD and acute ketamine treatment on vigilance states, locomotor activity, and electroencephalogram (EEG) power density spectra in Brown Norway rats under constant condition over 2 recording days. After SD and after the initial waking period induced by ketamine, both treatments induced a similar increase in non-rapid eye movement (NREM) sleep and EEG slow-wave activity (SWA) in NREM sleep. Rapid eye movement (REM) sleep was reduced immediately after both treatments but was recovered later only after the SD. The effects on the waking EEG differed between the treatments, with a faster theta peak during and after SD, and no change in the waking spectrum after ketamine. In conclusion, SD and ketamine both lead to an acute increment in NREM sleep SWA as well as in a reduction in REM sleep. The results suggest that selective suppression of REM sleep, combined with enhancement of SWA during NREM may be effective in the treatment of depression.

Berberine improves inhibitory avoidance memory impairment of Toxoplasma gondii-infected rat model of ketamine-induced schizophrenia

BACKGROUND

Memory impairment caused by Toxoplasma gondii infection has been documented. Berberine (BRB) is well known for its enhancing effects on memory and has shown promising results. However, the impact of BRB on T. gondii infection and schizophrenia-induced consolidation and reconsolidation memory impairment is still unclear. Here; we examined the effect of BRB on the inhibitory avoidance (IA) memory consolidation and reconsolidation impairment induced by T. gondii infection, and ketamine (Ket) as a pharmacological model of schizophrenia. Also; the brain-derived neurotrophic factor (BDNF) levels in the medial prefrontal cortex (mPFC) and hippocampus were analyzed.

METHODS

Rats were infected with T. gondii RH strain or received Ket (30 mg/kg/day) intraperitoneally (i.p) for at least five consecutive days (as the model of schizophrenia). Then followed by oral administration with BRB (25 mg/kg/day) for five days. Finally, the IA memory retention test was examined 48 post-conditioning, and BDNF was measured.

RESULTS

Results indicated IA memory impairment in T. gondii-infected animals since lower step-through latency (STL) was observed than in control animals. We found significant (P = 0.01, P = 0.001) elevations in STL and a significant decrease (P = 0.001) in total time spent in the dark area following BRB administration in infected and Ket-treated rats, indicating improvement (increased STL) in consolidation and reconsolidation memory. Moreover, BDNF levels were reduced (P = 0.01) in the hippocampus and mPFC regions of both T. gondii- infected and Ket-induced groups, which remarkably enhanced after BRB treatment. Furthermore; we found that BRB administration notably increased the mPFC BDNF levels in mPFC (P < 0.01) and hippocampus (P = 0.001) in the Ket-treated and rats infected with T. gondii.

CONCLUSION

Taken together; BRB may be a valuable preclinical treatment for improving memory impairment through BDNF expression in PFC and hippocampus, therefore; BRB is suggested for memory disturbances induced by T. gondii infection.

Hippocampal phase precession is preserved under ketamine, but the range of precession across a theta cycle is reduced

BACKGROUND

Hippocampal phase precession, which depends on the precise spike timing of place cells relative to local theta oscillations, has been proposed to underlie sequential memory. N-methyl-D-asparate (NMDA) receptor antagonists such as ketamine disrupt memory and also reproduce several schizophrenia-like symptoms, including spatial memory impairments and disorganized cognition. It is possible that these impairments result from disruptions to phase precession.

AIMS/METHODS

We used an ABA design to test whether an acute, subanesthetic dose (7.5 mg/kg) of ketamine disrupted phase precession in CA1 of male rats as they navigated around a rectangular track for a food reward.

RESULTS/OUTCOMES

Ketamine did not affect the ability of CA1 place cells to precess despite changes to place cell firing rates, local field potential properties and locomotor speed. However, ketamine reduced the range of phase precession that occurred across a theta cycle.

CONCLUSION

Phase precession is largely robust to acute NMDA receptor antagonism by ketamine, but the reduced range of precession could have important implications for learning and memory.

Age, Dose, and Locomotion: Decoding Vulnerability to Ketamine in C57BL/6J and BALB/c Mice

Ketamine has been abused as a psychedelic agent and causes diverse neurobehavioral changes. Adolescence is a critical developmental stage but vulnerable to substances and environmental stimuli. Growing evidence shows that ketamine affects glutamatergic neurotransmission, which is important for memory storage, addiction, and psychosis. To explore diverse biological responses, this study was designed to assess ketamine sensitivity in mice of different ages and strains. Male C57BL/6J and BALB/c mice were studied in adolescence and adulthood separately. An open field test assessed motor behavioral changes. After a 30-min baseline habituation, mice were injected with ketamine (0, 25, and 50 mg/kg), and their locomotion was measured for 60 min. Following ketamine injection, the travelled distance and speed significantly increased in C57BL/6J mice between both age groups (p < 0.01), but not in BALB/c mice. The pattern of hyperlocomotion showed that mice were delayed at the higher dose (50 mg/kg) compared to the lower dose (25 mg/kg) of ketamine treatment. Ketamine accentuated locomotor activation in adolescent C57BL/6J mice compared to adults, but not in the BALB/c strain. Here, we show that ketamine-induced locomotor behavior is modulated by dose and age. The discrepancy of neurobehaviors in the two strains of mice indicates that sensitivity to ketamine is biologically determined. This study suggests that individual vulnerability to ketamine's pharmacological responses varies biologically.

Ketamine supresses REM sleep and markedly increases EEG gamma oscillations in the Wistar Kyoto rat model of treatment-resistant depression

Wistar-Kyoto (WKY) rats exhibit depression-like characteristics and decreased sensitivity to monoamine-based antidepressants, making them a suitable model of treatment-resistant depression (TRD). Ketamine has emerged recently as a rapidly acting antidepressant with high efficacy in TRD. Our aim was to determine whether subanaesthetic doses of ketamine can correct sleep and electroencephalogram (EEG) alterations in WKY rats and whether any ketamine-induced changes differentially affect WKY rats compared to Sprague-Dawley (SD) rats. Thus, we surgically implanted 8SD and 8 WKY adult male rats with telemetry transmitters and recorded their EEG, electromyogram, and locomotor activity after vehicle or ketamine (3, 5 or 10mg/kg, s.c.) treatment. We also monitored the plasma concentration of ketamine and its metabolites, norketamine and hydroxynorketamine in satellite animals. We found that WKY rats, have an increased amount of rapid eye movement (REM) sleep, fragmented sleep-wake pattern, and increased EEG delta power during non-REM sleep compared to SD rats. Ketamine suppressed REM sleep and increased EEG gamma power during wakefulness in both strains, but the gamma increase was almost twice as large in WKY rats than in SD rats. Ketamine also increased beta oscillations, but only in WKY rats. These differences in sleep and EEG are unlikely to be caused by dissimilarities in ketamine metabolism as the plasma concentrations of ketamine and its metabolites were similar in both strains. Our data suggest an enhanced antidepressant-like response to ketamine in WKY rats, and further support the predictive validity of acute REM sleep suppression as a measure of antidepressant responsiveness.

Neurobiology of Aggression-Review of Recent Findings and Relationship with Alcohol and Trauma

Aggression can be conceptualized as any behavior, physical or verbal, that involves attacking another person or animal with the intent of causing harm, pain or injury. Because of its high prevalence worldwide, aggression has remained a central clinical and public safety issue. Aggression can be caused by several risk factors, including biological and psychological, such as genetics and mental health disorders, and socioeconomic such as education, employment, financial status, and neighborhood. Research over the past few decades has also proposed a link between alcohol consumption and aggressive behaviors. Alcohol consumption can escalate aggressive behavior in humans, often leading to domestic violence or serious crimes. Converging lines of evidence have also shown that trauma and posttraumatic stress disorder (PTSD) could have a tremendous impact on behavior associated with both alcohol use problems and violence. However, although the link between trauma, alcohol, and aggression is well documented, the underlying neurobiological mechanisms and their impact on behavior have not been properly discussed. This article provides an overview of recent advances in understanding the translational neurobiological basis of aggression and its intricate links to alcoholism and trauma, focusing on behavior. It does so by shedding light from several perspectives, including in vivo imaging, genes, receptors, and neurotransmitters and their influence on human and animal behavior.

A Postsynaptic Density Immediate Early Gene-Based Connectome Analysis of Acute NMDAR Blockade and Reversal Effect of Antipsychotic Administration

Although antipsychotics' mechanisms of action have been thoroughly investigated, they have not been fully elucidated at the network level. We tested the hypothesis that acute pre-treatment with ketamine (KET) and administration of asenapine (ASE) would modulate the functional connectivity of brain areas relevant to the pathophysiology of schizophrenia, based on transcript levels of Homer1a, an immediate early gene encoding a key molecule of the dendritic spine. Sprague-Dawley rats (n = 20) were assigned to KET (30 mg/kg) or vehicle (VEH). Each pre-treatment group (n = 10) was randomly split into two arms, receiving ASE (0.3 mg/kg), or VEH. Homer1a mRNA levels were evaluated by in situ hybridization in 33 regions of interest (ROIs). We computed all possible pairwise Pearson correlations and generated a network for each treatment group. Acute KET challenge was associated with negative correlations between the medial portion of cingulate cortex/indusium griseum and other ROIs, not detectable in other treatment groups. KET/ASE group showed significantly higher inter-correlations between medial cingulate cortex/indusium griseum and lateral putamen, the upper lip of the primary somatosensory cortex, septal area nuclei, and claustrum, in comparison to the KET/VEH network. ASE exposure was associated with changes in subcortical-cortical connectivity and an increase in centrality measures of the cingulate cortex and lateral septal nuclei. In conclusion, ASE was found to finely regulate brain connectivity by modelling the synaptic architecture and restoring a functional pattern of interregional co-activation.

Integrative Roles of Dopamine Pathway and Calcium Channels Reveal a Link between Schizophrenia and Opioid Use Disorder

Several theories have been proposed to explain the mechanisms of substance use in schizophrenia. Brain neurons pose a potential to provide novel insights into the association between opioid addiction, withdrawal, and schizophrenia. Thus, we exposed zebrafish larvae at 2 days post-fertilization (dpf) to domperidone (DPM) and morphine, followed by morphine withdrawal. Drug-induced locomotion and social preference were assessed, while the level of dopamine and the number of dopaminergic neurons were quantified. In the brain tissue, the expression levels of genes associated with schizophrenia were measured. The effects of DMP and morphine were compared to vehicle control and MK-801, a positive control to mimic schizophrenia. Gene expression analysis revealed that α1C, α1Sa, α1Aa, drd2a, and th1 were up-regulated after 10 days of exposure to DMP and morphine, while th2 was down-regulated. These two drugs also increased the number of positive dopaminergic neurons and the total dopamine level but reduced the locomotion and social preference. The termination of morphine exposure led to the up-regulation of th2, drd2a, and c-fos during the withdrawal phase. Our integrated data implicate that the dopamine system plays a key role in the deficits in social behavior and locomotion that are common in the schizophrenia-like symptoms and opioid dependence.

Mechanisms underpinning Carpolobia lutea G. Don ethanol extract's neurorestorative and antipsychotic-like activities in an NMDA receptor antagonist model of schizophrenia

ETHNOPHARMACOLOGICAL RELEVANCE

Persistent ketamine insults to the central nervous system block NMDA receptors and disrupt putative neurotransmission, oxido-nitrosative, and inflammatory pathways, resulting in schizophrenia-like symptoms in animals. Previously, the ethnomedicinal benefits of Carpolobia lutea against insomnia, migraine headache, and insanity has been documented, but the mechanisms of action remain incomplete.

AIM OF THE STUDY

Presently, we explored the neuro-therapeutic role of Carpolobia lutea ethanol extract (C. lutea) in ketamine-induced schizophrenia-like symptoms in mice.

MATERIALS AND METHODS

Sixty-four male Swiss (22 ± 2 g) mice were randomly assigned into eight groups (n = 8/group) and exposed to a reversal ketamine model of schizophrenia. For 14 days, either distilled water (10 mL/kg; p.o.) or ketamine (20 mg/kg; i.p.) was administered, following possible reversal treatments with C. lutea (100, 200, 400, and 800 mg/kg; p.o.), haloperidol (1 mg/kg, p.o.), or clozapine (5 mg/kg; p.o.) beginning on days 8-14. During the experiment, a battery of behavioral characterizations defining schizophrenia-like symptoms were obtained using ANY-maze software, followed by neurochemical, oxido-inflammatory and histological assessments in the mice brains.

RESULTS

A 7-day reversal treatment with C. lutea reversed predictors of positive, negative and cognitive symptoms of schizophrenia. C. lutea also mitigated ketamine-induced neurochemical derangements as evidenced by modulations of dopamine, glutamate, norepinephrine and serotonin neurotransmission. Also, the increased acetylcholinesterase activity, malondialdehyde nitrite, interleukin-6 and tumor necrosis-factor-α concentrations were reversed by C. lutea accompanied with elevated levels of catalase, superoxide dismutase and reduced glutathione. Furthermore, C. lutea reversed ketamine-induced neuronal alterations in the prefrontal cortex, hippocampus and cerebellum sections of the brain.

CONCLUSION

These findings suggest that C. lutea reverses the cardinal symptoms of ketamine-induced schizophrenia in a dose-dependent fashion by modulating the oxido-inflammatory and neurotransmitter-related mechanisms.

Ketamine Inhalation Alters Behavior and Lower Urinary Tract Function in Mice

We aimed to evaluate behavioral and lower urinary tract changes in mice using a novel ketamine inhalation model mimicking human ketamine abusers and compare the results to those obtained using a ketamine intraperitoneal injection model. C57BL/6N mice were placed in a transparent acrylic observation cage connected to an ultrasonic nebulizer producing ketamine (KI) or saline (SI) fog. The mice were given KI or SI fog twice a week for three months. In another experiment arm, the mice were given intraperitoneal ketamine injections (KP) or saline injections (SP) twice a week for three months. The presence of urine ketamine (>100 ng/mL) was determined using a quick test kit. Locomotor activity was recorded by video using the open field test. Lower urinary tract function was assessed using urine spots, cystometry and histology. KI and KP mice crossed the center more frequently and traveled farther than SI and SP mice. Only KI mice, however, demonstrated popcorn-like jumping, and frequent center crossing. Detrusor overactivity, reduced cystometric bladder capacity, and denuded mucosa were observed in both KI and KP mice. Ketamine inhalation induces behavioral and lower urinary tract changes in mice that are comparable to intraperitoneal ketamine injections.

Niacin mitigates blood-brain barrier tight junctional proteins dysregulation and cerebral inflammation in ketamine rat model of psychosis: Role of GPR109A receptor

Dysregulated inflammatory responses and blood-brain barrier (BBB) dysfunction are recognized as central factors in the development of psychiatric disorders. The present study was designed to evaluate the effect of niacin on BBB integrity in ketamine-induced model of psychosis. Meanwhile, mepenzolate bromide (MPN), a GPR109A receptor blocker, was used to investigate the role of this receptor on the observed niacin's effect. Male Wistar rats received ketamine (30 mg/kg/day, i.p) for 5 consecutive days and then niacin (40 mg/kg/day, p.o), with or without MPN (5 mg/kg/day, i.p), was given for the subsequent 15 days. Three days before the end of experiment, rats were behaviorally tested using open field, novel object recognition, social interaction, and forced swimming tests. Niacin significantly ameliorated ketamine-induced behavioral deficits, amended gamma aminobutyric acid and glutamate concentration, decreased tumor necrosis factor-α and matrix metallopeptidase 9 levels, and increased netrin-1 contents in the hippocampus of rats. Niacin also augmented the hippocampal expression of ZO-1, occludin, and claudin-5 proteins, indicating the ability of niacin to restore the BBB integrity. Moreover, the histopathologic changes in hippocampal neurons were alleviated. Since all the beneficial effects of niacin in the present investigation were partially abolished by the co-administration of MPN; GPR109A receptor was proven to partially mediate the observed antipsychotic effects of niacin. These data revealed that GPR109A-mediated signaling pathways might represent potential targets for therapeutic interventions to prevent or slow the progression of psychosis.

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.

Vineland Adaptive Behavior Scale in a Cohort of Four ADNP Syndrome Patients Implicates Age-Dependent Developmental Delays with Increased Impact of Activities of Daily Living

Activity-dependent neuroprotective protein (ADNP) is one of the lead genes in autism spectrum disorder/intellectual disability. Heterozygous, de novo ADNP mutations cause the ADNP syndrome. Here, to evaluate natural history of the syndrome, mothers of two ADNP syndrome boys aged 6 and a half and two adults aged 27 years (man and woman) were subjected to Vineland III questionnaire assessing adaptive behavior. The boys were assessed again about 2 years after the first measurements. The skill measures, presented as standard scores (SS) included domains of communication, daily living, socialization, motor skills and a sum of adaptive behavior composite. The age equivalent (AE) and growth scale values (GSV) encompassing 11 subdomains assess the age level at which the subject's raw score is found at a norm sample median and the individual temporal progression, respectively. The norm referenced standard scores age-matched, mean 100 ± 15 of the two children showed the lowest outcome in communication (SS: 20-30). Daily living skills presented SS of 50-60, with a possible potential loss of some activities as the child ages, especially in interpersonal relationships with people outside of the immediate family (boy A). In contrast, in socialization, both children were at the SS of 38, with some positive increase to SS of ~ 45 (interpersonal relations with family members and coping skills, depending on the particular individual), 2 years later. Interestingly, there was an apparent large difference in motor skills (gross and fine) at the young age, with subject B showing a relatively higher level of skills (SS: 70), decreasing to subject A level (SS: 40) 2 years later. Together, the adaptive behavior composite suggested a level of SS: 39-48 with B showing a potential increase (SS: 41-44) and A, a substantial decrease (SS: 48-39), suggesting a strong impact of daily living skills. Adults were at SS: 20, which is the lowest possible score. AE showed minor improvements for subject A and B, with all AE values being below 3 years. GSVs for subject A showed some improvement with age, especially in interpersonal, play and leisure, and gross motor subdomains. GSV for subject B showed minor improvements in the various subdomains. Notably, all subjects showed a percentile rank < 1 compared with age-matched norms except for subject B as to motor domain (2^nd percentile) at the age of 6 years. In summary, the results, especially comparing SS and AEs between childhood and adulthood, implied a continuous deterioration of activities compared to the general population, encompassing a slower developmental process coupled to possible neurodegeneration, strongly supporting a great need for disease modifying medicinal procedures.

Calcium/calmodulin-dependent protein kinase IIα heterozygous knockout mice show electroencephalogram and behavioral changes characteristic of a subpopulation of schizophrenia and intellectual impairment

Cognitive deficit remains an intractable symptom of schizophrenia, accounting for substantial disability. Despite this, little is known about the cause of cognitive dysfunction in schizophrenia. Recent studies suggest that schizophrenia patients show several changes in dentate gyrus structure and functional characteristic of immaturity. The immature dentate gyrus (iDG) has been replicated in several mouse models, most notably the αCaMKII heterozygous mouse (CaMKIIa-hKO). The current study characterizes behavioral phenotypes of CaMKIIa-hKO mice and determines their neurophysiological profile using electroencephalogram (EEG) recording from hippocampus. CaMKIIa-hKO mice were hypoactive in home-cage environment; however, they displayed less anxiety-like phenotype, suggestive of impulsivity-like behavior. In addition, severe cognitive dysfunction was evident in CaMKIIa-hKO mice as examined by novel object recognition and contextual fear conditioning. Several EEG phenomena established in both patients and relevant animal models indicate key pathological changes associated with the disease, include auditory event-related potentials and time-frequency EEG oscillations. CaMKIIa-hKO mice showed altered event-related potentials characterized by an increase in amplitude of the N40 and P80, as well as increased P80 latency. These mice also showed increased power in theta range time-frequency measures. Additionally, CaMKIIa-hKO mice showed spontaneous bursts of spike wave activity, possibly indicating absence seizures. The GABAB agonist baclofen increased, while the GABAB antagonist CGP35348 and the T-Type Ca2⁺ channel blocker Ethosuximide decreased spike wave burst frequency. None of these changes in event-related potentials or EEG oscillations are characteristic of those observed in general population of patients with schizophrenia; yet, CaMKIIa-hKO mice likely model a subpopulation of patients with schizophrenia.

Astrocyte Activation, but not Microglia, Is Associated with the Experimental Mouse Model of Schizophrenia Induced by Chronic Ketamine

Ketamine is a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptors. Many experimental studies have shown that ketamine can induce cognitive impairments and schizophrenia-like symptoms. While much data have demonstrated that glial cells are associated with the pathophysiology of psychiatric disorders, including schizophrenia, the response of glial cells to ketamine and its significance to schizophrenia are not clear. The present study was intended to explore whether chronic ketamine treatment would induce behavioral and glial changes in mice. First, ketamine was used to stimulate behavioral abnormalities similar to schizophrenia evaluated by the open field test, elevated plus-maze test, Y maze test, novel object recognition test, and tail suspension test. Secondly, histopathology and Nissl staining were performed. Meanwhile, immunofluorescence was used to evaluate the expression levels of IBA-1 (a microglial marker) and GFAP (an astrocyte marker) in the mouse hippocampus for any change. Then, ELISA was used to analyze proinflammatory cytokine levels for any change. Our results showed that ketamine (25 mg/kg, i.p., qid, 12 days) induced anxiety, recognition deficits, and neuronal injury in the hippocampus. Moreover, chronic ketamine treatment enhanced GFAP expression in CA1 and DG regions of the hippocampus but did not influence the expression of IBA-1. Ketamine also increased the levels of IL-1β, IL-6, and TNF-α in the mouse hippocampus. Our study created a new procedure for ketamine administration, which successfully induce negative symptoms and cognitive-behavioral defects in schizophrenia by chronic ketamine. This study further revealed that an increase in astrocytosis, but not microglia, is associated with the mouse model of schizophrenia caused by ketamine. In summary, hippocampal astrocytes may be involved in the pathophysiology of ketamine-induced schizophrenia-like phenotypes through reactive transformation and regulation of neuroinflammation.

REL-1017 (esmethadone; d-methadone) does not cause reinforcing effect, physical dependence and withdrawal signs in Sprague Dawley rats

REL-1017 (esmethadone, d-methadone) is the opioid-inactive d-isomer of racemic d,l-methadone. REL-1017 may exert antidepressant effects via uncompetitive N-methyl-d-aspartate receptor (NMDAR) channel block. As REL-1017 is expected to exert central nervous system activity, full characterization of its abuse potential is warranted. We evaluated lack of reinforcing effect, physical dependence, and withdrawal of REL-1017 in Sprague Dawley rats. (1) Self-administration Study Rats were trained to self-administer oxycodone intravenously (IV) and then were subjected to 3-day substitution tests where saline, oxycodone, and REL-1017 were self-delivered IV by a fixed number of lever presses; (2) Drug Discontinuation Study Rats were treated for 30 days by oral gavage with vehicle, REL-1017, ketamine or morphine and evaluated for withdrawal with functional observational batteries (FOBs). In the self-administration study, rats treated with saline, vehicle, and all REL-1017 doses showed the typical “extinction burst” pattern of response, characterized by an initial rapid increase of lever-pressing followed by a rapid decrease over 3 days. Rats treated with oxycodone maintained stable self-injection, as expected for reinforcing stimuli. In the withdrawal study, REL-1017 did not engender either morphine or ketamine withdrawal signs over 9 days following abrupt discontinuation of drug exposure. REL-1017 showed no evidence of abuse potential and did not engender withdrawal symptomatology.

Receptor-Mediated AKT/PI3K Signalling and Behavioural Alterations in Zebrafish Larvae Reveal Association between Schizophrenia and Opioid Use Disorder

The link between substance abuse and the development of schizophrenia remains elusive. In this study, we assessed the molecular and behavioural alterations associated with schizophrenia, opioid addiction, and opioid withdrawal using zebrafish as a biological model. Larvae of 2 days post fertilization (dpf) were exposed to domperidone (DMP), a dopamine-D2 dopamine D2 receptor antagonist, and morphine for 3 days and 10 days, respectively. MK801, an N-methyl-D-aspartate (NMDA) receptor antagonist, served as a positive control to mimic schizophrenia-like behaviour. The withdrawal syndrome was assessed 5 days after the termination of morphine treatment. The expressions of schizophrenia susceptibility genes, i.e., pi3k, akt1, slc6a4, creb1 and adamts2, in brains were quantified, and the levels of whole-body cyclic adenosine monophosphate (cAMP), serotonin and cortisol were measured. The aggressiveness of larvae was observed using the mirror biting test. After the short-term treatment with DMP and morphine, all studied genes were not differentially expressed. As for the long-term exposure, akt1 was downregulated by DMP and morphine. Downregulation of pi3k and slc6a4 was observed in the morphine-treated larvae, whereas creb1 and adamts2 were upregulated by DMP. The levels of cAMP and cortisol were elevated after 3 days, whereas significant increases were observed in all of the biochemical tests after 10 days. Compared to controls, increased aggression was observed in the DMP-, but not morphine-, treated group. These two groups showed reduction in aggressiveness when drug exposure was prolonged. Both the short- and long-term morphine withdrawal groups showed downregulation in all genes examined except creb1, suggesting dysregulated reward circuitry function. These results suggest that biochemical and behavioural alterations in schizophrenia-like symptoms and opioid dependence could be controlled by common mechanisms.

Long-term safety of ketamine and esketamine in treatment of depression

INTRODUCTION

Ketamine is an NMDA receptor antagonist that can produce rapid-acting antidepressant effects. Esketamine (Spravato), the S-enantiomer of racemic ketamine, was approved by the FDA for treatment-resistant depression in 2019. Here we review what is known about the long-term safety of both racemic ketamine and esketamine as therapies for psychiatric disorders.

AREAS COVERED

In this article, we conducted a safety review of ketamine and esketamine. In looking at ketamine and esketamine long-term safety effects, we considered data available from experimental studies and several phase-three clinical trials.

EXPERT OPINION

Based on available data, the most common side effects of ketamine/esketamine are generally transient, mild, and self-limited. These include dissociation, nausea, headache, elevated heart rate, and blood pressure. Treatment with esketamine may lead to an increased risk of lower urinary tract symptoms, such as dysuria or urgency. However, severe bladder pathology has not been reported among patients receiving doses of esketamine/ketamine in line with prescribing guidelines for depression. There is considerable data that ketamine at high doses can lead to long-term impairments in cognition. However, the esketamine clinical trials found that cognition generally remains stable or improves over time, suggesting that when used appropriately, there is no increased risk of cognitive impairment.

Sodium Benzoate—Harmfulness and Potential Use in Therapies for Disorders Related to the Nervous System: A Review

Currently, due to the large number of reports regarding the harmfulness of food additives, more and more consumers follow the so-called “clean label” trend, i.e., prefer and choose the least-processed food products. One of the compounds known as a preservative with a high safety profile is sodium benzoate. While some studies show that it can be used to treat conditions such as depression, pain, schizophrenia, autism spectrum disorders, and neurodegenerative diseases, others report its harmfulness. For example, it was found to cause mutagenic effects, generate oxidative stress, disrupt hormones, and reduce fertility. Due to such disparate results, the purpose of this study is to comprehensively discuss the safety profile of sodium benzoate and its potential use in neurodegenerative diseases, especially in autism spectrum disorder (ASD), schizophrenia, major depressive disorder (MDD), and pain relief.

Mathematical Model Insights into EEG Origin under Transcranial Direct Current Stimulation (tDCS) in the Context of Psychosis

Schizophrenia is a psychotic disease that develops progressively over years with a transition from prodromal to psychotic state associated with a disruption in brain activity. Transcranial Direct Current Stimulation (tDCS), known to alleviate pharmaco-resistant symptoms in patients suffering from schizophrenia, promises to prevent such a psychotic transition. To understand better how tDCS affects brain activity, we propose a neural cortico-thalamo-cortical (CTC) circuit model involving the Ascending Reticular Arousal System (ARAS) that permits to describe major impact features of tDCS, such as excitability for short-duration stimulation and electroencephalography (EEG) power modulation for long-duration stimulation. To this end, the mathematical model relates stimulus duration and Long-Term Plasticity (LTP) effect, in addition to describing the temporal LTP decay after stimulus offset. This new relation promises to optimize future stimulation protocols. Moreover, we reproduce successfully EEG-power modulation under tDCS in a ketamine-induced psychosis model and confirm the N-methyl-d-aspartate (NMDA) receptor hypofunction hypothesis in the etiopathophysiology of schizophrenia. The model description points to an important role of the ARAS and the δ-rhythm synchronicity in CTC circuit in early-stage psychosis.

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.

Ketamine for psychotic depression: An overview of the glutamatergic system and ketamine's mechanisms associated with antidepressant and psychotomimetic effects

Approximately 0.35-1% of the general population is afflicted with psychotic depression at some time in their life. Psychotic depression is a subtype of major depressive disorder characterized by mood congruent hallucinations and/or delusions. Patients with psychotic depression often represent the most severe cases, with high relapse and mortality rate. Although treatment guidelines recommend a combination of antidepressants and antipsychotics or electroconvulsive therapy, most patients subsequently relapse due to treatment resistance. Furthermore, with the concern of antipsychotic drug's side effects (e.g., tardive dyskinesia), there is a need for an alternative pharmacotherapy for psychotic depression. Recently, several case studies demonstrated that treatment with ketamine not only ameliorated mood, but also improved psychotic symptoms in patients with treatment-resistant depression and psychotic features. However, the safety of ketamine in these patients is controversial since ketamine is known to induce psychotomimetic and dissociative effects. Additionally, the efficacy and safety of ketamine in patients with psychotic depression has not been established as most clinical trials have excluded these persons due to the theorized risk of aggravating psychotic symptoms. Notwithstanding, it is not established empirically that ketamine treatment in psychotic depression would predictably amplify psychotic symptoms and/or overall illness presentation. Future trials evaluating ketamine in depression should include patients with psychotic features to inform whether ketamine is safe and effective in this subpopulation.

Neuroprotective effects of curcumin-loaded nanophytosome on ketamine-induced schizophrenia-like behaviors and oxidative damage in male mice

Curcumin as an antioxidant natural herb has shown numerous pharmacological effects. However, the poor bioavailability of curcumin is a significant pharmacological barrier for its antioxidant activities. The present study was conducted to develop curcumin-loaded nanophytosome (CNP) and explore their therapeutic potential in a ketamine (KET)-induced schizophrenia (SCZ) model. The mice in our experiment were treated orally with curcumin and CNP (20 mg/kg) for 30 consecutive days. In addition, the animals received intraperitoneal injection of KET (30 mg/kg/day) from the 16th to the 30th day. SCZ-like behaviors were evaluated employing forced swimming test (FST), open field test (OFT), and novel object recognition test (NORT), and oxidative stress markers in the brain were estimated. Our results revealed that CNP has a greater neuroprotective effect compared to free curcumin. CNP pretreatment significantly ameliorated KET-induced brain injury evidenced by a marked reduction in the depressive and anxiety-like behaviors, memory deficits, and oxidative stress markers in cortical and subcortical tissues. Therefore, CNP, as a suitable drug delivery system, may improve curcumin bioavailability and confer stronger neuroprotective effects against KET-induced behavioral deficits and oxidative damages.

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.

CBD Effects on Motor Profile and Neurobiological Indices Related to Glutamatergic Function Induced by Repeated Ketamine Pre-Administration

Clinical evidence and experimental studies have shown the psychotomimetic properties induced by ketamine. Moreover, acute or chronic ketamine (KET) administration has been widely used for modeling schizophrenia-like symptomatology and pathophysiology. Several studies have reported the antipsychotic potential of cannabidiol (CBD), while there is limited information on the cannabidiol effect on KET-induced schizophrenia-like impairments. Therefore, the goal of the present study was to evaluate neuroplastic changes induced by repeated KET administration, which is used as an experimental model of schizophrenia—with a behavioral focus on positive-like symptomatology– and to assess the modulatory role of CBD treatment. The present findings have shown a robust increase in motor activity in KET-treated rats, following a 10-day period of chronic administration at the sub-anesthetic dose of 30 mg/kg (i.p), that was reversed to normal by subsequent chronic CBD treatment. Concerning the expression of glutamate receptors, the current findings have shown region-dependent KET-induced constitutional alterations in NMDA and AMPA receptors that were modified by subsequent CBD treatment. Additionally, repeated KET administration increased ERK1/2 phosphorylation state in all regions examined, apart from the ventral hippocampus that was modulated by subsequent CBD treatment. The present results show, for the first time, a stimulated motor output coupled with a specific glutamatergic-related status and ERK1/2 activation following chronic KET administration that were attenuated by CBD treatment, in a region-dependent manner. These findings provide novel information concerning the antipsychotic potential of CBD using a specific design of chronic KET administration, thus contributing to experimental approaches that mirror the symptomatology and pathophysiology of schizophrenia.

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.

Clozapine protects adult neural stem cells from ketamine-induced cell death in correlation with decreased apoptosis and autophagy

Adult neurogenesis, the production of newborn neurons from neural stem cells (NSCs) has been suggested to be decreased in patients with schizophrenia. A similar finding was observed in an animal model of schizophrenia, as indicated by decreased bromodeoxyuridine (BrdU) labelling cells in response to a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist. The antipsychotic drug clozapine was shown to counteract the observed decrease in BrdU-labelled cells in hippocampal dentate gyrus (DG). However, phenotypic determination by immunohistochemistry analysis could not reveal whether BrdU-positive cells were indeed NSCs. Using a previously established cell model for analysing NSC protection in vitro, we investigated a protective effect of clozapine on NSCs.

Primary NSCs were isolated from the mouse subventricular zone (SVZ), we show that clozapine had a NSC protective activity alone, as evident by employing an ATP cell viability assay. In contrast, haloperidol did not show any NSC protective properties. Subsequently, cells were exposed to the non-competitive NMDA-receptor antagonist ketamine. Clozapine, but not haloperidol, had a NSC protective/anti-apoptotic activity against ketamine-induced cytotoxicity. The observed NSC protective activity of clozapine was associated with increased expression of the anti-apoptotic marker Bcl-2, decreased expression of the pro-apoptotic cleaved form of caspase-3 and associated with decreased expression of the autophagosome marker 1A/1B-light chain 3 (LC3-II).

Collectively, our findings suggest that clozapine may have a protective/anti-apoptotic effect on NSCs, supporting previous in vivo observations, indicating a neurogenesis-promoting activity for clozapine. If the data are further confirmed in vivo, the results may encourage an expanded use of clozapine to restore impaired neurogenesis in schizophrenia.

Subclass imbalance of parvalbumin-expressing GABAergic neurons in the hippocampus of a mouse ketamine model for schizophrenia, with reference to perineuronal nets

Impairments of parvalbumin-expressing GABAergic neurons (PV⁺ neurons) and specialized extracellular structures called perineuronal nets (PNNs) have been found in schizophrenic patients. In this study, we examined potential alterations in four subclasses of PV⁺ neurons colocalized with PNNs in the hippocampus of a mouse ketamine model for schizophrenia. Because biosynthesis of human natural killer-1 (HNK-1) is shown to be associated with the risk of schizophrenia, here we used mouse monoclonal Cat-315 antibody, which recognizes HNK-1 glycans on PNNs. Once-daily intraperitoneal injections of ketamine for seven consecutive days induced hyper-locomotor activity in the open field tests. The prepulse inhibition (PPI) test showed that PPI scores declined in ketamine-treated mice compared to vehicle-treated mice. The densities of PV⁺ neurons and Cat-315⁺ PNNs declined in the CA1 region of ketamine-treated mice. Interestingly, the density of Cat-315⁺/PV⁺ neurons was lower in ketamine-treated mice than in vehicle-treated mice, whereas the density of Cat-315^-/PV⁺ neurons was not affected by ketamine. Among the four subclasses of PV⁺ neurons, the densities of Cat-315⁺/PV⁺ basket cells and Cat-315^-/PV⁺ axo-axonic cells were lower in ketamine-treated mice than in vehicle-treated mice, while the densities of Cat-315^-/PV⁺ basket cells and Cat-315⁺/PV⁺ axo-axonic cells were not affected by ketamine. Taken together, PNNs may not play a simple neuroprotective role against ketamine. Because different subclasses of PV⁺ neurons are considered to play distinct roles in the hippocampal neuronal network, the ketamine-induced subclass imbalance of PV⁺ neurons may result in abnormal network activity, which underlies the pathophysiology of schizophrenia.

Reduced cortical GABA and glutamate in high schizotypy

RATIONALE

Abnormal functioning of the inhibitory gamma-aminobutyric acid (GABA) and excitatory (glutamate) systems is proposed to play a role in the development of schizophrenia spectrum disorder. Although results are mixed, previous 1H-magnetic resonance spectroscopy (MRS) studies in schizophrenia and clinical high-risk samples report these metabolites are altered in comparison to healthy controls. Currently, however, there are few studies of these metabolites in schizotypy samples, a personality dimension associated with the experience of schizophrenia and psychosis-like symptoms.

OBJECTIVES

We investigated if GABA and glutamate metabolite concentrations are altered in people with high schizotypy. We also explored the relationship between resilience to stress, GABA metabolite concentrations and schizotypy.

METHODS

We used MRS to examine GABA and glutamate levels in the medial prefrontal cortex in people with low and high schizotypy traits as assessed with the Schizotypal Personality Questionnaire. Resilience to stress was assessed using the Connor-Davidson Resilience Scale.

RESULTS

Compared to individuals with low schizotypy traits, high schizotypy individuals showed lower cortical prefrontal GABA (F (1,38) = 5.18, p = 0.03, η² = 0.09) and glutamate metabolite levels (F (1, 49) = 6.25, p = 0.02, η² = 0.02). Furthermore, participants with high GABA and high resilience levels were significantly more likely to be in the low schizotypy group than participants with low GABA and high resilience or high GABA and low resilience (95% CI 1.07-1.34, p < .001).

CONCLUSIONS

These findings demonstrate that subclinical schizotypal traits are associated with abnormal functioning of both inhibitory and excitatory systems and suggest that these transmitters are implicated in a personality trait believed to be on a continuum with psychosis.

Distinct hierarchical alterations of intrinsic neural timescales account for different manifestations of psychosis

Hierarchical perceptual-inference models of psychosis may provide a holistic framework for understanding psychosis in schizophrenia including heterogeneity in clinical presentations. Particularly, hypothesized alterations at distinct levels of the perceptual-inference hierarchy may explain why hallucinations and delusions tend to cluster together yet sometimes manifest in isolation. To test this, we used a recently developed resting-state fMRI measure of intrinsic neural timescale (INT), which reflects the time window of neural integration and captures hierarchical brain gradients. In analyses examining extended sensory hierarchies that we first validated, we found distinct hierarchical INT alterations for hallucinations versus delusions in the auditory and somatosensory systems, thus providing support for hierarchical perceptual-inference models of psychosis. Simulations using a large-scale biophysical model suggested local elevations of excitation-inhibition ratio at different hierarchical levels as a potential mechanism. More generally, our work highlights the robustness and utility of INT for studying hierarchical processes relevant to basic and clinical neuroscience.

Application of a flexible polymer microECoG array to map functional coherence in schizophrenia model

Anatomically, connections form the fundamental brain network, functionally the different types of oscillatory electric activities are creating a temporarily connected fraction of the anatomical connectome generating an output to the motor system. Schizophrenia can be considered as a connectome disease, in which the sensory input generates a schizophrenia specific temporary connectome and the signal processing becomes diseased showing hallucinations and adverse behavioral reactions. In this work, flexible, 32-channel polymer microelectrode arrays fabricated by the authors are used to map the functional coherence on large cortical areas during physiological activities in a schizophrenia model in rats.-Fabrication of a flexible microECoG array is shown.-Protocol to use a flexible microECoG is demonstrated to characterize connectome diseases in rats.-Customized method to analyze the functional coherence between different cortical areas during visually evoked potential is detailed.-R-based implementation of the analysis method is presented.

Hippocampal Hyperactivity as a Druggable Circuit-Level Origin of Aberrant Salience in Schizophrenia

The development of current neuroleptics was largely aiming to decrease excessive dopaminergic signaling in the striatum. However, the notion that abnormal dopamine creates psychotic symptoms by causing an aberrant assignment of salience that drives maladaptive learning chronically during disease development suggests a therapeutic value of early interventions that correct salience-related neural processing. The mesolimbic dopaminergic output is modulated by several interconnected brain-wide circuits centrally involving the hippocampus and key relays like the ventral and associative striatum, ventral pallidum, amygdala, bed nucleus of the stria terminalis, nucleus reuniens, lateral and medial septum, prefrontal and cingulate cortex, among others. Unraveling the causal relationships between these circuits using modern neuroscience techniques holds promise for identifying novel cellular-and ultimately molecular-treatment targets for reducing transition to psychosis and symptoms of schizophrenia. Imaging studies in humans have implicated a hyperactivity of the hippocampus as a robust and early endophenotype in schizophrenia. Experiments in rodents, in turn, suggested that the activity of its output region-the ventral subiculum-may modulate dopamine release from ventral tegmental area (VTA) neurons in the ventral striatum. Even though these observations suggested a novel circuit-level target for anti-psychotic action, no therapy has yet been developed along this rationale. Recently evaluated treatment strategies-at least in part-target excess glutamatergic activity, e.g. N-acetyl-cysteine (NAC), levetiracetam, and mGluR2/3 modulators. We here review the evidence for the central implication of the hippocampus-VTA axis in schizophrenia-related pathology, discuss its symptom-related implications with a particular focus on aberrant assignment of salience, and evaluate some of its short-comings and prospects for drug discovery.

Non-invasive electroencephalographical (EEG) recording system in awake monkeys

Background

Human clinical studies reported that several electroencephalographical (EEG) parameters can be used as biomarkers of psychiatric disorders. EEGs recorded from non-human primates (monkeys) is useful for understanding of human pathologies of psychiatric disorders and development of new therapeutic agents.

New methods

In this study, we expand a previous non-invasive head holding system with face masks for awake monkeys to be applied to scalp EEG recording. The new design of a head holding system allows to attach scalp EEG electrodes on the positions comparable to human electrode placement and to present auditory stimuli.

Results

With this system, we could record auditory evoked potentials (AEPs) in auditory sensory gating and oddball paradigms, which are often used as biomarkers of psychiatric disorders in animal models and human patients. The recorded AEPs were comparable to previous human clinical data.

Comparison with existing methods

Compared with previous non-invasive head holding systems, top, side (cheek and ears), and rear of the head can be open for attachment of EEG electrodes and auditory stimulation in the present system.

Conclusions

The results suggest that the present system is useful in EEG recording from awake monkeys. Furthermore, this system can be applied to eye-tracking and chronic intra-cerebral recording experiments.

Transient Dose-dependent Effects of Ketamine on Neural Oscillatory Activity in Wistar-Kyoto Rats

Ketamine is a promising therapeutic for treatment-resistant depression (TRD) but is associated with an array of short-term psychomimetic side-effects. These disparate drug effects may be elicited through the modulation of neural circuit activity. The purpose of this study was to therefore delineate dose- and time-dependent changes in ketamine-induced neural oscillatory patterns in regions of the brain implicated in depression. Wistar-Kyoto rats were used as a model system to study these aspects of TRD neuropathology whereas Wistar rats were used as a control strain. Animals received a low (10 mg/kg) or high (30 mg/kg) dose of ketamine and temporal changes in neural oscillatory activity recorded from the prefrontal cortex (PFC), cingulate cortex (Cg), and nucleus accumbens (NAc) for ninety minutes. Effects of each dose of ketamine on immobility in the forced swim test were also evaluated. High dose ketamine induced a transient increase in theta power in the PFC and Cg, as well as a dose-dependent increase in gamma power in these regions 10-min, but not 90-min, post-administration. In contrast, only low dose ketamine normalized innate deficits in fast gamma coherence between the NAc-Cg and PFC-Cg, an effect that persisted at 90-min post-injection. These low dose ketamine-induced oscillatory alterations were accompanied by a reduction in immobility time in the forced swim test. These results show that ketamine induces time-dependent effects on neural oscillations at specific frequencies. These drug-induced changes may differentially contribute to the psychomimetic and therapeutic effects of the drug.

Pain in neuropsychiatry: Insights from animal models

Pain is the most common symptom reported in clinical practice, meaning that it is associated with many pathologies as either the origin or a consequence of other illnesses. Furthermore, pain is a complex emotional and sensorial experience, as the correspondence between pain and body damage varies considerably. While these issues are widely acknowledged in clinical pain research, until recently they have not been extensively considered when exploring animal models, important tools for understanding pain pathophysiology. Interestingly, chronic pain is currently considered a risk factor to suffer psychiatric disorders, mainly stress-related disorders like anxiety and depression. Conversely, pain appears to be altered in many psychiatric disorders, such as depression, anxiety and schizophrenia. Thus, pain and psychiatric disorders have been linked in epidemiological and clinical terms, although the neurobiological mechanisms involved in this pathological bidirectional relationship remain unclear. Here we review the evidence obtained from animal models about the co-morbidity of pain and psychiatric disorders, placing special emphasis on the different dimensions of pain.

Expression of Behavioral Phenotypes in Genetic and Environmental Mouse Models of Schizophrenia

Schizophrenia is a neuropsychiatric disorder characterized by multifactorial etiology involving complex interactions among genetic and environmental factors. "Multiple-hit" models of the disorder can explain its variable incidence and prevalence in related individuals. Hence, there is a dire need to understand these interactions in the emergence of schizophrenia. To test these factors in the emergence of schizophrenia-like behaviors, we employed a genetic mouse model of the disorder (harboring the DISC1 mutation) along with various environmental insults, such as early life stress (maternal separation of pups) and/or pharmacological interventions (ketamine injections). When assessed on a battery of behavioral tests, we found that environmental interventions affect the severity of behavioral phenotypes in terms of increased negative behavior, as shown by reduced mobility in the forced swim and tail suspension tests, and changes to positive and cognitive symptoms, such as increased locomotion and disrupted PPI along with reduced working memory, respectively. Among the various interventions, the genetic mutation had the most profound effect on behavioral aberrations, followed by an environmental intervention by ketamine injections and ketamine-injected animals that were maternally separated during early postnatal days. We conclude that although environmental factors increased the prevalence of aberrant behavioral phenotypes, genetic background is still the predominant influence on phenotypic alterations in these mouse models of schizophrenia.

Glutamate Systems in DSM-5 Anxiety Disorders: Their Role and a Review of Glutamate and GABA Psychopharmacology

Serotonin reuptake inhibitors and benzodiazepines are evidence-based pharmacological treatments for Anxiety Disorders targeting serotonin and GABAergic systems, respectively. Although clearly effective, these medications fail to improve anxiety symptoms in a significant proportion of patients. New insights into the glutamate system have directed attention toward drugs that modulate glutamate as potential alternative treatments for anxiety disorders. Here we summarize the current understanding of the potential role of glutamate neurotransmission in anxiety disorders and highlight specific glutamate receptors that are potential targets for novel anxiety disorder treatments. We also review clinical trials of medications targeting the glutamate system in DSM-5 anxiety disorders. Understanding the role of the glutamate system in the pathophysiology of anxiety disorder may aid in developing novel pharmacological agents that are effective in treating anxiety disorders.

The Role of the N-Methyl-D-Aspartate Receptors in Social Behavior in Rodents

The appropriate display of social behaviors is essential for the well-being, reproductive success and survival of an individual. Deficits in social behavior are associated with impaired N-methyl-D-aspartate (NMDA) receptor-mediated neurotransmission. In this review, we describe recent studies using genetically modified mice and pharmacological approaches which link the impaired functioning of the NMDA receptors, especially of the receptor subunits GluN1, GluN2A and GluN2B, to abnormal social behavior. This abnormal social behavior is expressed as impaired social interaction and communication, deficits in social memory, deficits in sexual and maternal behavior, as well as abnormal or heightened aggression. We also describe the positive effects of pharmacological stimulation of the NMDA receptors on these social deficits. Indeed, pharmacological stimulation of the glycine-binding site either by direct stimulation or by elevating the synaptic glycine levels represents a promising strategy for the normalization of genetically-induced, pharmacologically-induced or innate deficits in social behavior. We emphasize on the importance of future studies investigating the role of subunit-selective NMDA receptor ligands on different types of social behavior to provide a better understanding of the underlying mechanisms, which might support the development of selective tools for the optimized treatment of disorders associated with social deficits.

Early Celastrol Administration Prevents Ketamine-Induced Psychotic-Like Behavioral Dysfunctions, Oxidative Stress and IL-10 Reduction in The Cerebellum of Adult Mice

Administration of subanesthetic doses of ketamine during brain maturation represents a tool to mimic an early insult to the central nervous system (CNS). The cerebellum is a key player in psychosis pathogenesis, to which oxidative stress also contributes. Here, we investigated the impact of early celastrol administration on behavioral dysfunctions in adult mice that had received ketamine (30 mg/kg i.p.) at postnatal days (PNDs) 7, 9, and 11. Cerebellar levels of 8-hydroxydeoxyguanosine (8-OHdG), NADPH oxidase (NOX) 1 and NOX2, as well as of the calcium-binding protein parvalbumin (PV), were also assessed. Furthermore, celastrol effects on ketamine-induced alterations of proinflammatory (TNF-α, IL-6 and IL-1β) and anti-inflammatory (IL-10) cytokines in this brain region were evaluated. Early celastrol administration prevented ketamine-induced discrimination index decrease at adulthood. The same was found for locomotor activity elevations and increased close following and allogrooming, whereas no beneficial effects on sniffing impairment were detected. Ketamine increased 8-OHdG in the cerebellum of adult mice, which was also prevented by early celastrol injection. Cerebellar NOX1 levels were enhanced at adulthood following postnatal ketamine exposure. Celastrol per se induced NOX1 decrease in the cerebellum. This effect was more significant in animals that were early administered with ketamine. NOX2 levels did not change. Ketamine administration did not affect PV amount in the cerebellum. TNF-α levels were enhanced in ketamine-treated animals; however, this was not prevented by early celastrol administration. While no changes were observed for IL-6 and IL-1β levels, ketamine determined a reduction of cerebellar IL-10 expression, which was prevented by early celastrol treatment. Our results suggest that NOX inhibition during brain maturation prevents the development of psychotic-like behavioral dysfunctions, as well as the increased cerebellar oxidative stress and the reduction of IL-10 in the same brain region following ketamine exposure in postnatal life. This opens novel neuroprotective opportunities against early detrimental insults occurring during brain development.