Early molecular events of autosomal-dominant Alzheimer's disease in marmosets with PSEN1 mutations.

INTRODUCTION: Fundamental questions remain about the key mechanisms that initiate Alzheimer's disease (AD) and the factors that promote its progression. Here we report the successful generation of the first genetically engineered marmosets that carry knock-in (KI) point mutations in the presenilin 1 (PSEN1) gene that can be studied from birth throughout lifespan. METHODS: CRISPR/Cas9 was used to generate marmosets with C410Y or A426P point mutations in PSEN1. Founders and their germline offspring are comprehensively studied longitudinally using non-invasive measures including behavior, biomarkers, neuroimaging, and multiomics signatures. RESULTS: Prior to adulthood, increases in plasma amyloid beta were observed in PSEN1 mutation carriers relative to non-carriers. Analysis of brain revealed alterations in several enzyme-substrate interactions within the gamma secretase complex prior to adulthood. DISCUSSION: Marmosets carrying KI point mutations in PSEN1 provide the opportunity to study the earliest primate-specific mechanisms that contribute to the molecular and cellular root causes of AD onset and progression. HIGHLIGHTS: We report the successful generation of genetically engineered marmosets harboring knock-in point mutations in the PSEN1 gene. PSEN1 marmosets and their germline offspring recapitulate the early emergence of AD-related biomarkers. Studies as early in life as possible in PSEN1 marmosets will enable the identification of primate-specific mechanisms that drive disease progression.

Improving preclinical to clinical translation of cognitive function for aging-related disorders: the utility of comprehensive touchscreen testing batteries in common marmosets.

Concerns about poor animal to human translation have come increasingly to the fore, in particular with regards to cognitive improvements in rodent models, which have failed to translate to meaningful clinical benefit in humans. This problem has been widely acknowledged, most recently in the field of Alzheimer's disease, although this issue pervades the spectrum of central nervous system (CNS) disorders, including neurodevelopmental, neuropsychiatric, and neurodegenerative diseases. Consequently, recent efforts have focused on improving preclinical to clinical translation by incorporating more clinically analogous outcome measures of cognition, such as touchscreen-based assays, which can be employed across species, and have great potential to minimize the translational gap. For aging-related research, it also is important to incorporate model systems that facilitate the study of the long prodromal phase in which cognitive decline begins to emerge and which is a major limitation of short-lived species, such as laboratory rodents. We posit that to improve translation of cognitive function and dysfunction, nonhuman primate models, which have conserved anatomical and functional organization of the primate brain, are necessary to move the field of translational research forward and to bridge the translational gaps. The present studies describe the establishment of a comprehensive battery of touchscreen-based tasks that capture a spectrum of domains sensitive to detecting aging-related cognitive decline, which will provide the greatest benefit through longitudinal evaluation throughout the prolonged lifespan of the marmoset.

Bridging the rodent to human translational gap: Marmosets as model systems for the study of Alzheimer's disease.

Introduction: Our limited understanding of the mechanisms that trigger the emergence of Alzheimer's disease (AD) has contributed to the lack of interventions that stop, prevent, or fully treat this disease. We believe that the development of a non-human primate model of AD will be an essential step toward overcoming limitations of other model systems and is crucial for investigating primate-specific mechanisms underlying the cellular and molecular root causes of the pathogenesis and progression of AD. Methods: A new consortium has been established with funding support from the National Institute on Aging aimed at the generation, characterization, and validation of Marmosets As Research Models of AD (MARMO-AD). This consortium will study gene-edited marmoset models carrying genetic risk for AD and wild-type genetically diverse aging marmosets from birth throughout their lifespan, using non-invasive longitudinal assessments. These include characterizing the genetic, molecular, functional, behavioral, cognitive, and pathological features of aging and AD. Results: The consortium successfully generated viable founders carrying PSEN1 mutations in C410Y and A426P using CRISPR/Cas9 approaches, with germline transmission demonstrated in the C410Y line. Longitudinal characterization of these models, their germline offspring, and normal aging outbred marmosets is ongoing. All data and resources from this consortium will be shared with the greater AD research community. Discussion: By establishing marmoset models of AD, we will be able to investigate primate-specific cellular and molecular root causes that underlie the pathogenesis and progression of AD, overcome limitations of other model organisms, and support future translational studies to accelerate the pace of bringing therapies to patients.

Emerging Electroencephalographic Biomarkers to Improve Preclinical to Clinical Translation in Alzheimer's Disease.

Continually emerging data indicate that sub-clinical, non-convulsive epileptiform activity is not only prevalent in Alzheimer's disease (AD) but is detectable early in the course of the disease and predicts cognitive decline in both humans and animal models. Epileptiform activity and other electroencephalographic (EEG) measures may hold powerful, untapped potential to improve the translational validity of AD-related biomarkers in model animals ranging from mice, to rats, and non-human primates. In this review, we will focus on studies of epileptiform activity, EEG slowing, and theta-gamma coupling in preclinical models, with particular focus on its role in cognitive decline and relevance to AD. Here, each biomarker is described in the context of the contemporary literature and recent findings in AD relevant animal models are discussed.

Maternal Immune Activation during Pregnancy Alters Postnatal Brain Growth and Cognitive Development in Nonhuman Primate Offspring.

Human epidemiological studies implicate exposure to infection during gestation in the etiology of neurodevelopmental disorders. Animal models of maternal immune activation (MIA) have identified the maternal immune response as the critical link between maternal infection and aberrant offspring brain and behavior development. Here we evaluate neurodevelopment of male rhesus monkeys (Macaca mulatta) born to MIA-treated dams (n = 14) injected with a modified form of the viral mimic polyinosinic:polycytidylic acid at the end of the first trimester. Control dams received saline injections at the same gestational time points (n = 10) or were untreated (n = 4). MIA-treated dams exhibited a strong immune response as indexed by transient increases in sickness behavior, temperature, and inflammatory cytokines. Although offspring born to control or MIA-treated dams did not differ on measures of physical growth and early developmental milestones, the MIA-treated animals exhibited subtle changes in cognitive development and deviated from species-typical brain growth trajectories. Longitudinal MRI revealed significant gray matter volume reductions in the prefrontal and frontal cortices of MIA-treated offspring at 6 months that persisted through the final time point at 45 months along with smaller frontal white matter volumes in MIA-treated animals at 36 and 45 months. These findings provide the first evidence of early postnatal changes in brain development in MIA-exposed nonhuman primates and establish a translationally relevant model system to explore the neurodevelopmental trajectory of risk associated with prenatal immune challenge from birth through late adolescence.SIGNIFICANCE STATEMENT Women exposed to infection during pregnancy have an increased risk of giving birth to a child who will later be diagnosed with a neurodevelopmental disorder. Preclinical maternal immune activation (MIA) models have demonstrated that the effects of maternal infection on fetal brain development are mediated by maternal immune response. Since the majority of MIA models are conducted in rodents, the nonhuman primate provides a unique system to evaluate the MIA hypothesis in a species closely related to humans. Here we report the first longitudinal study conducted in a nonhuman primate MIA model. MIA-exposed offspring demonstrate subtle changes in cognitive development paired with marked reductions in frontal gray and white matter, further supporting the association between prenatal immune challenge and alterations in offspring neurodevelopment.

New approaches to quantify social development in rhesus macaques (Macaca mulatta): Integrating eye tracking with traditional assessments of social behavior.

The nonhuman primate provides a sophisticated animal model system both to explore neurobiological mechanisms underlying complex behaviors and to facilitate preclinical research for neurodevelopmental and neuropsychiatric disease. A better understanding of evolutionarily conserved behaviors and brain processes between humans and nonhuman primates will be needed to successfully apply recently released NIMH guidelines (NOT-MH-19-053) for conducting rigorous nonhuman primate neurobehavioral research. Here, we explore the relationship between two measures of social behavior that can be used in both humans and nonhuman primates-traditional observations of social interactions with conspecifics and eye gaze detection in response to social stimuli. Infant male rhesus macaques (Macaca mulatta) serving as controls (N = 14) for an ongoing study were observed in their social rearing groups and participated in a noninvasive, longitudinal eye-tracking study. We found significant positive relationships between time spent viewing eyes of faces in an eye tracker and number of initiations made for social interactions with peers that is consistent with similar observations in human populations. Although future studies are needed to determine if this relationship represents species-typical social developmental processes, these preliminary results provide a novel framework to explore the relationship between social interactions and social attention in nonhuman primate models for neurobehavioral development.

The Importance of Complementary Collaboration of Researchers, Veterinarians, and Husbandry Staff in the Successful Training of Marmoset Behavioral Assays.

Interest in marmosets as research models has seen exponential growth over the last decade, especially given that the research community is eager to improve on gaps with historical animal models for behavioral and cognitive disorders. The spectrum of human disease traits that present naturally in marmosets, as well as the range of analogous human behaviors that can be assessed in marmosets, makes them ideally suited as translational models for behavioral and cognitive disorders. Regardless of the specific research aims of any project, without close collaboration between researchers, veterinarians, and animal care staff, it would be impossible to meet these goals. Behavior is inherently variable, as are marmosets that are genetically and phenotypically diverse. Thus, to ensure rigor, reliability, and reproducibility in results, it is important that in the research environment, the animal's daily husbandry and veterinary needs are being met and align with the research goals while keeping the welfare of the animal the most critical and highest priority. Much of the information described herein provides details on key components for successful behavioral testing, based on a compendium of methods from peer-reviewed publications and our own experiences. Specific areas highlighted include habituation procedures, selection of appropriate rewards, optimization of testing environments, and ways to integrate regular veterinary and husbandry procedures into the research program with minimal disruptions to the behavioral testing plan. This article aims to provide a broad foundation for researchers new to establishing behavioral and cognitive testing paradigms in marmosets and especially for the veterinary and husbandry colleagues who are indispensable collaborators of these research projects.

Non-invasive Eye Tracking Methods for New World and Old World Monkeys.

Eye-tracking methods measure what humans and other animals visually attend to in the environment. In nonhuman primates, eye tracking can be used to test hypotheses about how primates process social information. This information can further our understanding of primate behavior as well as offer unique translational potential to explore causes of or treatments for altered social processing as seen in people with neurodevelopmental disorders such as autism spectrum disorder and schizophrenia. However, previous methods for collecting eye-tracking data in nonhuman primates required some form of head restraint, which limits the opportunities for research with respect to the number of or kinds of primates that can undergo an eye-tracking study. We developed a novel, noninvasive method for collecting eye tracking data that can be used both in animals that are difficult to restrain without sedation as well as animals that are of different ages and sizes as the box size can be adjusted. Using a transport box modified with a viewing window, we collected eye-tracking data in both New (Callicebus cupreus) and Old World monkeys (Macaca mulatta) across multiple developmental time points. These monkeys had the option to move around the box and avert their eyes from the screen, yet, they demonstrated a natural interest in viewing species-specific imagery with no previous habituation to the eye-tracking paradigm. Provided with opportunistic data from voluntary viewing of stimuli, we found that juveniles viewed stimuli more than other age groups, videos were viewed more than static photo imagery, and that monkeys increased their viewing time when presented with multiple eye tracking sessions. This noninvasive approach opens new opportunities to integrate eye-tracking studies into nonhuman primate research.

Opportunities and challenges for intranasal oxytocin treatment studies in nonhuman primates.

Nonhuman primates provide a human-relevant experimental model system to explore the mechanisms by which oxytocin (OT) regulates social processing and inform its clinical applications. Here, we highlight contributions of the nonhuman primate model to our understanding of OT treatment and address unique challenges in administering OT to awake behaving primates. Prior preclinical research utilizing macaque monkeys has demonstrated that OT can modulate perception of other individuals and their expressions, attention to others, imitation, vigilance to social threats, and prosocial decisions. We further describe ongoing efforts to develop an OT delivery system for use in experimentally naïve juvenile macaque monkeys compatible with naturalistic social behavior outcomes. Finally, we discuss future directions to further develop the rhesus monkey as a preclinical test bed to evaluate the effects of OT exposure and advance efforts to translate basic science OT research into safe and effective OT therapies.

Maternal Immune Activation and Autism Spectrum Disorder: From Rodents to Nonhuman and Human Primates.

A subset of women who are exposed to infection during pregnancy have an increased risk of giving birth to a child who will later be diagnosed with a neurodevelopmental or neuropsychiatric disorder. Although epidemiology studies have primarily focused on the association between maternal infection and an increased risk of offspring schizophrenia, mounting evidence indicates that maternal infection may also increase the risk of autism spectrum disorder. A number of factors, including genetic susceptibility, the intensity and timing of the infection, and exposure to additional aversive postnatal events, may influence the extent to which maternal infection alters fetal brain development and which disease phenotype (autism spectrum disorder, schizophrenia, other neurodevelopmental disorders) is expressed. Preclinical animal models provide a test bed to systematically evaluate the effects of maternal infection on fetal brain development, determine the relevance to human central nervous system disorders, and to evaluate novel preventive and therapeutic strategies. Maternal immune activation models in mice, rats, and nonhuman primates suggest that the maternal immune response is the critical link between exposure to infection during pregnancy and subsequent changes in brain and behavioral development of offspring. However, differences in the type, severity, and timing of prenatal immune challenge paired with inconsistencies in behavioral phenotyping approaches have hindered the translation of preclinical results to human studies. Here we highlight the promises and limitations of the maternal immune activation model as a preclinical tool to study prenatal risk factors for autism spectrum disorder, and suggest specific changes to improve reproducibility and maximize translational potential.

The atypical antipsychotic blonanserin reverses (+)-PD-128907- and ketamine-induced deficit in executive function in common marmosets.

Antagonism of the dopamine D3 receptor is considered a promising strategy for the treatment of cognitive impairment associated with schizophrenia. We have previously reported that the atypical antipsychotic blonanserin, a dopamine D2/D3 and serotonin 5-HT2A receptor antagonist, highly occupies dopamine D3 receptors at its antipsychotic dose range in rats. In the present study, we evaluated the effects of blonanserin on executive function in common marmosets using the object retrieval with detour (ORD) task. The dopamine D3 receptor-preferring agonist (+)-PD-128907 at 1mg/kg decreased success rate in the difficult trial, but not in the easy trial. Since the difference between the two trials is only cognitive demand, our findings indicate that excess activation of dopamine D3 receptors impairs executive function in common marmosets. Blonanserin at 0.1mg/kg reversed the decrease in success rate induced by (+)-PD-128907 in the difficult trial. This finding indicates that blonanserin has beneficial effect on executive function deficit induced by activation of the dopamine D3 receptor in common marmosets. Next, and based on the glutamatergic hypothesis of schizophrenia, the common marmosets were treated with the N-methyl-d-aspartate (NMDA) receptor antagonist ketamine. Ketamine at sub-anesthetic doses decreased success rate in the difficult trial, but not in the easy trial. Blonanserin at 0.1mg/kg reversed the decrease in success rate induced by ketamine in the difficult trial. The findings of this study suggest that blonanserin might have beneficial effect on executive dysfunction in patients with schizophrenia.

The dopamine D1 receptor agonist SKF-82958 effectively increases eye blinking count in common marmosets.

Eye blinking is a spontaneous behavior observed in all mammals, and has been used as a well-established clinical indicator for dopamine production in neuropsychiatric disorders, including Parkinson's disease and Tourette syndrome [1,2]. Pharmacological studies in humans and non-human primates have shown that dopamine agonists/antagonists increase/decrease eye blinking rate. Common marmosets (Callithrix jacchus) have recently attracted a great deal of attention as suitable experimental animals in the psychoneurological field due to their more developed prefrontal cortex than rodents, easy handling compare to other non-human primates, and requirement for small amounts of test drugs. In this study, we evaluated the effects of dopamine D1-4 receptors agonists on eye blinking in common marmosets. Our results show that the dopamine D1 receptor agonist SKF-82958 and the non-selective dopamine receptor agonist apomorphine significantly increased common marmosets eye blinking count, whereas the dopamine D2 agonist (+)-PHNO and the dopamine D3 receptor agonist (+)-PD-128907 produced somnolence in common marmosets resulting in a decrease in eye blinking count. The dopamine D4 receptor agonists PD-168077 and A-41297 had no effect on common marmosets' eye blinking count. Finally, the dopamine D1 receptor antagonist SCH 39166 completely blocked apomorphine-induced increase in eye blinking count. These results indicate that eye blinking in common marmosets may be a useful tool for in vivo screening of novel dopamine D1 receptor agonists as antipsychotics.

Behavioral and neurophysiological effects of Ro 10-5824, a dopamine D4 receptor partial agonist, in common marmosets.

RATIONALE: Growing evidence suggests that dopamine D4 receptors (D4Rs) are involved in controlling executive functions. We have previously demonstrated that Ro 10-5824, a D4R partial agonist, improves the performance of common marmosets in the object retrieval detour (ORD) task. However, the neural mechanisms underlying this improvement are unknown. OBJECTIVES: We investigated the behavioral and neurophysiological effects of Ro 10-5824 in common marmosets. METHODS: The effects of Ro 10-5824 on cognitive function were evaluated using the ORD task. The neurophysiological effects of Ro 10-5824 were investigated by quantitative electroencephalography, especially on baseline gamma band activity in the frontal cortex. The effects of Ro 10-5824 on spontaneous locomotion were also assessed. RESULTS: Systemic administration of Ro 10-5824 at 3 mg/kg significantly increased the success rate in the ORD task. At doses of 1 and 3 mg/kg, Ro 10-5824 increased baseline gamma band activity in the frontal cortex. Ro 10-5824 had no effect on spontaneous locomotion. CONCLUSIONS: Activation of D4R by Ro 10-5824 improves the success rate in the ORD task and increases baseline gamma band activity in the frontal cortex without affecting locomotion in common marmosets. These findings highlight the role of D4R in gamma oscillations of non-human primates. As gamma oscillations are thought to be involved in attention and behavioral inhibition, our results suggest D4R agonists may improve these cognitive functions by modulating baseline gamma band activity in the frontal cortex.

The serotonin 5-HT1A receptor agonist tandospirone improves executive function in common marmosets.

Previous pilot clinical studies have shown that the serotonin 5-HT1A receptor agonist tandospirone has beneficial effect on cognitive deficits associated with schizophrenia. In the present study, we evaluated the cognitive efficacy of tandospirone, given alone or in combination with the antipsychotic blonanserin, risperidone or haloperidol, on executive function in marmosets using the object retrieval with detour (ORD) task. Treatment with tandospirone alone at 20 and 40 mg/kg increased the number of correct responses in the difficult trial, while risperidone (0.3mg/kg) and haloperidol (0.3mg/kg) decreased the number of correct responses in this trial. On the other hand, blonanserin (0.1-0.3mg/kg), an atypical antipsychotic highly selective for dopamine D2/D3 and serotonin 5-HT2A receptors, did not affect the number of correct responses in both the easy and difficult trials. Co-treatment with tandospirone (20mg/kg) and risperidone (0.1-0.3mg/kg) or haloperidol (0.1-0.3mg/kg) did not improve animals' performance in the difficult trial. However, co-treatment with tandospirone and blonanserin (0.1-0.3mg/kg) increased the number of correct responses in the difficult trial. In addition, treatment with the dopamine D1 receptor agonist SKF-81297 at 1mg/kg increased marmosets correct responses in the difficult trial. These results suggest that tandospirone is a promising candidate for the treatment of cognitive deficits associated with schizophrenia and that adjunctive treatment with tandospirone and blonanserin is more appropriate for cognitive deficits than combination therapy with tandospirone and risperidone or haloperidol. The results of this study also indicate that the putative mechanism of action of tandospirone might be related to enhancement of dopamine neurotransmission via activation of the 5-HT1A receptor.

Lurasidone suppresses rapid eye movement sleep and improves sleep quality in rats.

Patients with psychiatric disorders, including schizophrenia, are reported to suffer from sleep disorders. In this study, we investigated the effects of lurasidone, an atypical antipsychotic, on sleep architecture in rats using sleep electroencephalography. The course of sleep in rats was classified into 3 stages: WAKE, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Lurasidone shortened REM duration and prolonged the mean duration of one bout in WAKE and NREM. Quantitative frequency band analysis during NREM sleep revealed that lurasidone increases slow waves and decreases fast waves. These results suggest that lurasidone ameliorates sleep disorders associated with psychosis.

Effects of lurasidone on ketamine-induced joint visual attention dysfunction as a possible disease model of autism spectrum disorders in common marmosets.

Infants with autism have difficulties performing joint visual attention (JVA), defined as following another person's pointing gesture and gaze. Some non-human primates (NHPs) can also perform JVA. Most preclinical research on autism spectrum disorders (ASD) has used rodents as animal models of this social interaction disorder. However, models using rodents fail to capture the complexity of social interactions that are disrupted in ASD. Therefore, JVA impairment in NHPs might be a more useful model of ASD. The aim of this study was to develop an appropriate and convenient ASD model with common marmosets. We first tested whether marmosets were capable of performing JVA. Subsequently, we administered ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, to induce JVA impairment and investigated the effects of lurasidone, a newer antipsychotic agent, on the JVA impairments. An apparatus was constructed using 4 white boxes, which were attached to the corners of a frame. All boxes had a hinged door, and marmosets could easily obtain a reward by pushing the door. An experimenter pointed and gazed at the boxes to inform the marmosets which box contained the reward. Their behavior was scored according to the number of incorrect choices. The JVA score was significantly higher in the cued vs. uncued tasks. Ketamine significantly decreased the JVA score, but lurasidone significantly reversed this effect. These findings suggest that this experimental system could be a useful animal model of neuropsychiatric disorders characterized by NMDA-receptor signaling, including ASD, and that lurasidone might be effective for some aspects of ASD.

Lack of dopamine D4 receptor affinity contributes to the procognitive effect of lurasidone.

We previously demonstrated among several antipsychotics exhibiting potent dopamine D2 receptor antagonism that only lurasidone, (1R,2S,3R,4S)-N-[(1R,2R)-2-[4-(1,2-benzisothiazol-3-yl)-1-piperazinylmethyl]-1-cyclohexylmethyl]-2,3-bicyclo[2.2.1] heptanedicarboximide hydrochloride, improved performance in the object retrieval detour (ORD) task by marmosets. The mechanisms by which only lurasidone causes enhancements in cognitive function have not yet been established; however, most antipsychotics, except for lurasidone, have been shown to exhibit potent antagonistic activity against the dopamine D4 receptor. The objectives of this study were to evaluate the role of the dopamine D4 receptor on executive function with the selective agonist, Ro10-5824 and antagonist, L-745,870, and elucidate a possible mechanism for the procognitive effect of lurasidone. The effects of these drugs were evaluated in naïve marmosets using the ORD task. Changes in the success rate during the difficult trial in the task were used to assess the cognitive effect of the drugs. Ro10-5824 (0.3-3 mg/kg) increased the success rate in the difficult trial, potentiated the effect of lurasidone, and reversed the cognitive impairment induced by clozapine. Interestingly, the co-administration of L-745,870 with lurasidone decreased the success rate in the difficult trial, whereas the single administration of L-745,870 had no effect. These results suggest that activation of the dopamine D4 receptor may improve executive function, whereas concomitant blockade of dopamine D4 and D2 receptors may have the opposite effect. In addition to the other unique binding profiles of other monoamine receptors, the lack of affinity for the dopamine D4 receptor by lurasidone could also contribute, at least partly, to its cognitive-enhancing effect.

Effects of a dopamine D1 agonist on ketamine-induced spatial working memory dysfunction in common marmosets.

It is considered that functional deficiency of the NMDA receptors in the prefrontal cortex (PFC) is one of the causes of the cognitive impairment observed in schizophrenia. As non-human primates display more developed PFC than rodents, they are considered to be useful experimental animals for improving the predictive validity of models used to discover new drugs for treating cognitive dysfunction. The aim of this study was to develop a convenient model of the cognitive impairment observed in schizophrenia using common marmosets and the CANTAB system and to test whether a full agonist of the dopamine D1 receptor (SKF-81297) was effective against the cognitive impairment induced in this model. We administered the NMDA receptor antagonist ketamine (1.5-16mg/kg, i.m.) to the marmosets to induce cognitive impairment and then evaluated their working memory function using the CANTAB spatial working memory (SWM) test. The marmosets' working memory was impaired by subanesthetic doses of ketamine. Next, we tested the effect of SKF-81297 (3 or 10mg/kg, p.o.) on this ketamine-induced cognitive dysfunction. The marmosets were administered SKF-81297 30min before the ketamine injection. Pretreatment with SKF-81297 reversed the ketamine-induced cognitive deficiency. In this study, we found that a D1 receptor agonist, which has been reported to enhance cognitive function, reversed ketamine-induced cognitive impairment in marmosets, which suggests that our marmoset model could be a useful tool for predicting the clinical efficacy of cognitive-enhancing drugs.

Effects of lurasidone on executive function in common marmosets.

Cognitive impairment is one of the major symptoms of schizophrenia, and is considered largely due to dysfunctions in the prefrontal cortex (PFC). Lurasidone, a novel atypical antipsychotic agent with high binding affinity for dopamine D2, serotonin 5-HT7, 5-HT2A and 5-HT1A receptors has been reported to have superior efficacy in rodents' models of cognitive impairment. However, the beneficial effect of lurasidone on cognitive impairment has not been evaluated in non-human primates. In this study, we investigated the effect of lurasidone on executive function, which is one of the cognitive domains, in common marmosets and compared the results to those of other antipsychotics. The effects of lurasidone, haloperidol, olanzapine, risperidone, quetiapine and clozapine on executive function were evaluated in naïve marmosets using the object retrieval with detours (ORD) task. Before drug treatment, marmosets' success rates in the easy trial of the test were almost 90%. However, maximum success in the difficult trial of the task reached only 50% after 8 days of training. Haloperidol, olanzapine and risperidone decreased correct performance even in the easy trial of the task. All drugs, except lurasidone, impaired success rate in the difficult trial. On the other hand, lurasidone dose-dependently increased marmosets' success rates in the difficult trial with significant effect at 10mg/kg. In conclusion, we have shown in this study that lurasidone, unlike conventional antipsychotics, improves cognition associated with executive function in common marmosets. These findings suggest that lurasidone would be more useful for treatment of schizophrenia cognitive impairment than other antipsychotics.

Effects of a novel metabotropic glutamate receptor 7 negative allosteric modulator, 6-(4-methoxyphenyl)-5-methyl-3-pyridin-4-ylisoxazonolo[4,5-c]pyridin-4(5H)-one (MMPIP), on the central nervous system in rodents.

We recently identified 6-(4-methoxyphenyl)-5-methyl-3-pyridin-4-ylisoxazolo[4,5-c]pyridin-4(5H)-one (MMPIP), the first allosteric metabotropic glutamate (mGlu) 7 receptor-selective negative allosteric modulator. In this study, we examined the in vivo pharmacological effects of MMPIP on the central nervous system. MMPIP was distributed into the brain after systemic administration in both mice and rats. Pharmacokinetic study revealed that the half-life of MMPIP in circulation was about 1h in rats. Results of various behavioral studies revealed that MMPIP impaired non-spatial and spatial cognitive performances in the object recognition test and the object location test in mice, respectively. In rats, MMPIP increased time to complete the task in the 8-arm radial maze test without increasing error. In addition to impairing cognition, MMPIP decreased social interaction with reduction of line crossing in rats, while MMPIP had no effects on locomotor activity in rats and mice, rota-rod performance in mice, prepulse inhibition in rats, maternal separation-induced ultrasonic vocalization in rat pups, stress-induced hyperthermia in mice, or the tail suspension test in mice. No analgesic effects of MMPIP were detected in either the tail immersion test or formalin test in mice. MMPIP did not alter the threshold for induction of seizures by electrical shock or pentylenetetrazole in mice. These findings suggest that blockade of mGlu(7) receptors by MMPIP may modulate both non-spatial and spatial cognitive functions without non-selective inhibitory effects on the central nervous system.