Chronic administration of atypical antipsychotics improves behavioral and synaptic defects of STOP null mice

Lifelong exposure to polystyrene-nanoplastics induces an attention-deficit hyperactivity disorder-like phenotype and impairs brain aging in mice

The accumulation of plastic waste in the environment, breaking down into micro- and nanoplastics, poses significant threats to ecosystem and human health. Plastic particles have been detected in human blood, urine, and placental tissue, indicating widespread exposure. While their long-term health impacts remain unclear, developing brains, especially in fetuses and children, may be vulnerable, potentially resulting in behavioral changes or neurodevelopmental disorders. This study explores the effects of chronic exposure to 23-nm polystyrene nanoplastics at 10 µg/day/kg in wild-type mice across life stages, using exposure levels reflective of human reality. Maternal exposure disrupted critical developmental milestones in pups. In adulthood, exposed mice exhibited Attention-Deficit Hyperactivity Disorder (ADHD)-like traits, including hyperactivity, increased risk-taking behaviors, and impaired motor learning and executive functions. In aging mice, exposure was associated with a lower epileptic threshold, with developing seizures. These behavioral changes were linked to altered gene and synaptic protein expression associated with ADHD and epilepsy. At the cellular level, lifelong nanoplastic exposure caused lysosomal dysfunctions and increased lipofuscin accumulation, indicative of accelerated brain aging. These findings align with the growing prevalence of ADHD and epilepsy in humans, particularly children and the elderly, emphasizing the urgent need to address plastic pollution and its health implications.

Pathophysiological Mechanisms of Antipsychotic-Induced Parkinsonism

Among neurological adverse reactions in patients with schizophrenia treated with antipsychotics (APs), drug-induced parkinsonism (DIP) is the most common motility disorder caused by drugs affecting dopamine receptors. One of the causes of DIP is the disruption of neurotransmitter interactions that regulate the signaling pathways of the dopaminergic, cholinergic, GABAergic, adenosinergic, endocannabinoid, and other neurotransmitter systems. Presently, the development mechanisms remain poorly understood despite the presence of the considered theories of DIP pathogenesis.

A meta-analysis of deep brain structural shape and asymmetry abnormalities in 2,833 individuals with schizophrenia compared with 3,929 healthy volunteers via the ENIGMA Consortium

Schizophrenia is associated with widespread alterations in subcortical brain structure. While analytic methods have enabled more detailed morphometric characterization, findings are often equivocal. In this meta-analysis, we employed the harmonized ENIGMA shape analysis protocols to collaboratively investigate subcortical brain structure shape differences between individuals with schizophrenia and healthy control participants. The study analyzed data from 2,833 individuals with schizophrenia and 3,929 healthy control participants contributed by 21 worldwide research groups participating in the ENIGMA Schizophrenia Working Group. Harmonized shape analysis protocols were applied to each site's data independently for bilateral hippocampus, amygdala, caudate, accumbens, putamen, pallidum, and thalamus obtained from T1-weighted structural MRI scans. Mass univariate meta-analyses revealed more-concave-than-convex shape differences in the hippocampus, amygdala, accumbens, and thalamus in individuals with schizophrenia compared with control participants, more-convex-than-concave shape differences in the putamen and pallidum, and both concave and convex shape differences in the caudate. Patterns of exaggerated asymmetry were observed across the hippocampus, amygdala, and thalamus in individuals with schizophrenia compared to control participants, while diminished asymmetry encompassed ventral striatum and ventral and dorsal thalamus. Our analyses also revealed that higher chlorpromazine dose equivalents and increased positive symptom levels were associated with patterns of contiguous convex shape differences across multiple subcortical structures. Findings from our shape meta-analysis suggest that common neurobiological mechanisms may contribute to gray matter reduction across multiple subcortical regions, thus enhancing our understanding of the nature of network disorganization in schizophrenia.

The microbial metabolite p-Cresol induces autistic-like behaviors in mice by remodeling the gut microbiota

BACKGROUND

Autism spectrum disorders (ASD) are associated with dysregulation of the microbiota-gut-brain axis, changes in microbiota composition as well as in the fecal, serum, and urine levels of microbial metabolites. Yet a causal relationship between dysregulation of the microbiota-gut-brain axis and ASD remains to be demonstrated. Here, we hypothesized that the microbial metabolite p-Cresol, which is more abundant in ASD patients compared to neurotypical individuals, could induce ASD-like behavior in mice.

RESULTS

Mice exposed to p-Cresol for 4 weeks in drinking water presented social behavior deficits, stereotypies, and perseverative behaviors, but no changes in anxiety, locomotion, or cognition. Abnormal social behavior induced by p-Cresol was associated with decreased activity of central dopamine neurons involved in the social reward circuit. Further, p-Cresol induced changes in microbiota composition and social behavior deficits could be transferred from p-Cresol-treated mice to control mice by fecal microbiota transplantation (FMT). We also showed that mice transplanted with the microbiota of p-Cresol-treated mice exhibited increased fecal p-Cresol excretion, compared to mice transplanted with the microbiota of control mice. In addition, we identified possible p-Cresol bacterial producers. Lastly, the microbiota of control mice rescued social interactions, dopamine neurons excitability, and fecal p-Cresol levels when transplanted to p-Cresol-treated mice.

CONCLUSIONS

The microbial metabolite p-Cresol induces selectively ASD core behavioral symptoms in mice. Social behavior deficits induced by p-Cresol are dependant on changes in microbiota composition. Our study paves the way for therapeutic interventions targeting the microbiota and p-Cresol production to treat patients with ASD. Video abstract.

Survival Bias and Crosstalk between Chronological and Behavioral Age: Age- and Genotype-Sensitivity Tests Define Behavioral Signatures in Middle-Aged, Old, and Long-Lived Mice with Normal and AD-Associated Aging

New evidence refers to a high degree of heterogeneity in normal but also Alzheimer's disease (AD) clinical and temporal patterns, increased mortality, and the need to find specific end-of-life prognosticators. This heterogeneity is scarcely explored in very old male AD mice models due to their reduced survival. In the present work, using 915 (432 APP23 and 483 C57BL/6 littermates) mice, we confirmed the better survival curves in male than female APP23 mice and respective wildtypes, providing the chance to characterize behavioral signatures in middle-aged, old, and long-lived male animals. The sensitivity of a battery of seven paradigms for comprehensive screening of motor (activity and gait analysis), neuropsychiatric and cognitive symptoms was analyzed using a cohort of 56 animals, composed of 12-, 18- and 24-month-old male APP23 mice and wildtype littermates. Most variables analyzed detected age-related differences. However, variables related to coping with stress, thigmotaxis, frailty, gait, and poor cognition better discriminated the behavioral phenotype of male APP23 mice through the three old ages compared with controls. Most importantly, non-linear age- and genotype-dependent behavioral signatures were found in long-lived animals, suggesting crosstalk between chronological and biological/behavioral ages useful to study underlying mechanisms and distinct compensations through physiological and AD-associated aging.

Chronic antipsychotic treatment exerts limited effects on the mania-like behavior of dopamine transporter knockdown mice

BACKGROUND

Bipolar disorder is a life-threatening disorder linked to dopamine transporter (DAT) polymorphisms, with reduced DAT levels seen in positron emission tomography and postmortem brains.

AIMS

The purpose of this study was to examine the effects of approved antipsychotics on DAT dysfunction-mediated mania behavior in mice.

METHODS

DAT knockdown mice received either D2-family receptor antagonist risperidone or asenapine and mania-related behaviors were assessed in the clinically-relevant behavioral pattern monitor to assess spontaneous exploration.

RESULTS

Chronic risperidone did not reverse mania-like behavior in DAT knockdown mice. Chronic asenapine reduced mania behavior but this effect was more pronounced in wild-type littermates than in DAT knockdown mice.

CONCLUSION

Taken together, these findings suggest that while acute antipsychotic treatment may be beneficial in management of bipolar mania, more targeted therapeutics may be necessary for long-term treatment. Specific investigation into DAT-targeting drugs could improve future treatment of bipolar mania.

Beyond Neuronal Microtubule Stabilization: MAP6 and CRMPS, Two Converging Stories

The development and function of the central nervous system rely on the microtubule (MT) and actin cytoskeletons and their respective effectors. Although the structural role of the cytoskeleton has long been acknowledged in neuronal morphology and activity, it was recently recognized to play the role of a signaling platform. Following this recognition, research into Microtubule Associated Proteins (MAPs) diversified. Indeed, historically, structural MAPs—including MAP1B, MAP2, Tau, and MAP6 (also known as STOP);—were identified and described as MT-binding and -stabilizing proteins. Extensive data obtained over the last 20 years indicated that these structural MAPs could also contribute to a variety of other molecular roles. Among multi-role MAPs, MAP6 provides a striking example illustrating the diverse molecular and cellular properties of MAPs and showing how their functional versatility contributes to the central nervous system. In this review, in addition to MAP6’s effect on microtubules, we describe its impact on the actin cytoskeleton, on neuroreceptor homeostasis, and its involvement in signaling pathways governing neuron development and maturation. We also discuss its roles in synaptic plasticity, brain connectivity, and cognitive abilities, as well as the potential relationships between the integrated brain functions of MAP6 and its molecular activities. In parallel, the Collapsin Response Mediator Proteins (CRMPs) are presented as examples of how other proteins, not initially identified as MAPs, fall into the broader MAP family. These proteins bind MTs as well as exhibiting molecular and cellular properties very similar to MAP6. Finally, we briefly summarize the multiple similarities between other classical structural MAPs and MAP6 or CRMPs.In summary, this review revisits the molecular properties and the cellular and neuronal roles of the classical MAPs, broadening our definition of what constitutes a MAP.

Altered circadian activity and sleep/wake rhythms in the stable tubule only polypeptide (STOP) null mouse model of schizophrenia

Sleep and circadian rhythm disruptions commonly occur in individuals with schizophrenia. Stable tubule only polypeptide (STOP) knockout (KO) mice show behavioral impairments resembling symptoms of schizophrenia. We previously reported that STOP KO mice slept less and had more fragmented sleep and waking than wild-type littermates under a light/dark (LD) cycle. Here, we assessed the circadian phenotype of male STOP KO mice by examining wheel-running activity rhythms and EEG/EMG-defined sleep/wake states under both LD and constant darkness (DD) conditions. Wheel-running activity rhythms in KO and wild-type mice were similarly entrained in LD, and had similar free-running periods in DD. The phase delay shift in response to a light pulse given early in the active phase under DD was preserved in KO mice. KO mice had markedly lower activity levels, lower amplitude activity rhythms, less stable activity onsets, and more fragmented activity than wild-type mice in both lighting conditions. KO mice also spent more time awake and less time in rapid eye movement sleep (REMS) and non-REMS (NREMS) in both LD and DD conditions, with the decrease in NREMS concentrated in the active phase. KO mice also showed altered EEG features and higher amplitude rhythms in wake and NREMS (but not REMS) amounts in both lighting conditions, with a longer free-running period in DD, compared to wild-type mice. These results indicate that the STOP null mutation in mice altered the regulation of sleep/wake physiology and activity rhythm expression, but did not grossly disrupt circadian mechanisms.

Pyr1-Mediated Pharmacological Inhibition of LIM Kinase Restores Synaptic Plasticity and Normal Behavior in a Mouse Model of Schizophrenia

The search for effective treatments for neuropsychiatric disorders is ongoing, with progress being made as brain structure and neuronal function become clearer. The central roles played by microtubules (MT) and actin in synaptic transmission and plasticity suggest that the cytoskeleton and its modulators could be relevant targets for the development of new molecules to treat psychiatric diseases. In this context, LIM Kinase - which regulates both the actin and MT cytoskeleton especially in dendritic spines, the post-synaptic compartment of the synapse - might be a good target. In this study, we analyzed the consequences of blocking LIMK1 pharmacologically using Pyr1. We investigated synaptic plasticity defects and behavioral disorders in MAP6 KO mice, an animal model useful for the study of psychiatric disorders, particularly schizophrenia. Our results show that Pyr1 can modulate MT dynamics in neurons. In MAP6 KO mice, chronic LIMK inhibition by long-term treatment with Pyr1 can restore normal dendritic spine density and also improves long-term potentiation, both of which are altered in these mice. Pyr1 treatment improved synaptic plasticity, and also reduced social withdrawal and depressive/anxiety-like behavior in MAP6 KO mice. Overall, the results of this study validate the hypothesis that modulation of LIMK activity could represent a new therapeutic strategy for neuropsychiatric diseases.

Preclinical validation of the micropipette-guided drug administration (MDA) method in the maternal immune activation model of neurodevelopmental disorders

Pharmacological treatments in laboratory rodents remain a cornerstone of preclinical psychopharmacological research and drug development. There are numerous ways in which acute or chronic pharmacological treatments can be implemented, with each method having certain advantages and drawbacks. Here, we describe and validate a novel treatment method in mice, which we refer to as the micropipette-guided drug administration (MDA) procedure. This administration method is based on a sweetened condensed milk solution as a vehicle for pharmacological substances, which motivates the animals to consume vehicle and/or drug solutions voluntarily in the presence of the experimenter. In a proof-of-concept study, we show that the pharmacokinetic profiles of the atypical antipsychotic drug, risperidone, were similar whether administered via the MDA procedure or via the conventional oral gavage method. Unlike the latter, however, MDA did not induce the stress hormone, corticosterone. Furthermore, we assessed the suitability and validity of the MDA method in a mouse model of maternal immune activation, which is frequently used as a model of immune-mediated neurodevelopmental disorders. Using this model, we found that chronic treatment (>4 weeks, once per day) with risperidone via MDA led to a dose-dependent mitigation of MIA-induced social interaction deficits and amphetamine hypersensitivity. Taken together, the MDA procedure described herein represents a novel pharmacological administration method for per os treatments in mice that is easy to implement, cost effective, non-invasive, and less stressful for the animals than conventional oral gavage methods.

Defective tubulin detyrosination causes structural brain abnormalities with cognitive deficiency in humans and mice

Reversible detyrosination of tubulin, the building block of microtubules, is crucial for neuronal physiology. Enzymes responsible for detyrosination were recently identified as complexes of vasohibins (VASHs) one or two with small VASH-binding protein (SVBP). Here we report three consanguineous families, each containing multiple individuals with biallelic inactivation of SVBP caused by truncating variants (p.Q28* and p.K13Nfs*18). Affected individuals show brain abnormalities with microcephaly, intellectual disability and delayed gross motor and speech development. Immunoblot testing in cells with pathogenic SVBP variants demonstrated that the encoded proteins were unstable and non-functional, resulting in a complete loss of VASH detyrosination activity. Svbp knockout mice exhibit drastic accumulation of tyrosinated tubulin and a reduction of detyrosinated tubulin in brain tissue. Similar alterations in tubulin tyrosination levels were observed in cultured neurons and associated with defects in axonal differentiation and architecture. Morphological analysis of the Svbp knockout mouse brains by anatomical magnetic resonance imaging showed a broad impact of SVBP loss, with a 7% brain volume decrease, numerous structural defects and a 30% reduction of some white matter tracts. Svbp knockout mice display behavioural defects, including mild hyperactivity, lower anxiety and impaired social behaviour. They do not, however, show prominent memory defects. Thus, SVBP-deficient mice recapitulate several features observed in human patients. Altogether, our data demonstrate that deleterious variants in SVBP cause this neurodevelopmental pathology, by leading to a major change in brain tubulin tyrosination and alteration of microtubule dynamics and neuron physiology.

Impact of Chronic Risperidone Use on Behavior and Survival of 3xTg-AD Mice Model of Alzheimer's Disease and Mice With Normal Aging

Psychosis and/or aggression are common problems in dementia, and when severe or persistent, cause considerable patient distress and disability, caregiver stress, and early institutionalization. In 2005, the Food and Drug Administration (FDA) determined that atypical antipsychotics were associated with a significantly greater mortality risk compared to placebo, which prompted the addition of an FDA black-box warning. The American College of Neuropsychopharmacology (ACNP) White Paper, 2008, reviewed this issue and made clinical and research recommendations regarding the use of antipsychotics in dementia patients with psychosis and/or agitation. Increased mortality risk has also been described in cerebrovascular adverse events in elderly users of antipsychotics. In the present work, at the translational level, we used male 3xTg-AD mice (PS1M146V, APPSwe, tauP301L) at advanced stages of the disease reported to have worse survival than females, to study the behavioral effects of a low chronic dose of risperidone (0.1 mg/kg, s.c., 90 days, from 13 to 16 months of age) and its impact on long-term survival, as compared to mice with normal aging. Animals were behaviorally assessed for cognitive and BPSD (behavioral and psychological symptoms of dementia)-like symptoms in naturalistic and experimental conditions (open-field test, T-maze, social interaction, Morris water maze, and marble test) before and after treatment. Weight, basal glucose levels, and IPGTT (i.p. glucose tolerance test) were also recorded. Neophobia in the corner test was used for behavioral monitoring. Survival curves were recorded throughout the experiment until natural death. The benefits of risperidone were limited, both at cognitive and BPSD-like level, and mostly restricted to burying, agitation/vibrating tail, and other social behaviors. However, the work warns about a clear early mortality risk window during the treatment and long-lasting impact on survival. Reduced life expectancy and life span were observed in the 3xTg-AD mice, but total lifespan (36 months) recorded in C57BL/6 × 129Sv counterparts with normal aging was also truncated to 28 months in those with treatment. Sarcopenia at time of death was found in all groups, but was more severe in wild-type animals treated with risperidone. Therefore, the 3xTg-AD mice and their non-transgenic counterparts can be useful to delimitate critical time windows and for studying the physio-pathogenic factors and underlying causal events involved in this topic of considerable public health significance.

Neurobehavioral effects of chronic low-dose risperidone administration in juvenile male rats

Despite substantial increases in the use of antipsychotics to treat various psychiatric conditions in children, there is a lack of literature regarding long-term effects of early treatment. Some studies have indicated that early administration results in differential alterations to neurotransmission systems, but few studies have investigated whether there are long-term behavioral modifications. Therefore, the aim of the current study was to investigate the neurobehavioral effects of low dose risperidone (a commonly prescribed antipsychotic) treatment using juvenile rats. Twenty-four male Sprague-Dawley rats were either subcutaneously implanted with a continuous release risperidone pellet (.04 mg/day) or a placebo pellet. To encompass the peri-adolescent to adolescent timeframe (postnatal day 40-70) thought to be important for brain development, male rats began risperidone treatment at post-natal day 35. Six weeks following commencement of risperidone treatment, all rats were tested on a battery of behavioral assessments including open field, object recognition, Morris Water Maze, and Y-Maze tasks. Risperidone treatment did not affect performance on the open field, object recognition, or Morris Water maze. A significant effect was found on the Y-maze. Although all rats exhibited normal spontaneous alternation, risperidone treated rats demonstrated significantly higher same arm returns, indicative of a working memory deficit. Continued research is needed to determine whether early exposure to risperidone may lead to differences in working memory at longer time-points. These results seem to indicate that early low dose risperidone treatment during the peri-adolescent and adolescent period does not severely impair behavior.

Deletion of the microtubule-associated protein 6 (MAP6) results in skeletal muscle dysfunction

Background

The skeletal muscle fiber has a specific and precise intracellular organization which is at the basis of an efficient muscle contraction. Microtubules are long known to play a major role in the function and organization of many cells, but in skeletal muscle, the contribution of the microtubule cytoskeleton to the efficiency of contraction has only recently been studied. The microtubule network is dynamic and is regulated by many microtubule-associated proteins (MAPs). In the present study, the role of the MAP6 protein in skeletal muscle organization and function has been studied using the MAP6 knockout mouse line.

Methods

The presence of MAP6 transcripts and proteins was shown in mouse muscle homogenates and primary culture using RT-PCR and western blot. The in vivo evaluation of muscle force of MAP6 knockout (KO) mice was performed on anesthetized animals using electrostimulation coupled to mechanical measurement and multimodal magnetic resonance. The impact of MAP6 deletion on microtubule organization and intracellular structures was studied using immunofluorescent labeling and electron microscopy, and on calcium release for muscle contraction using Fluo-4 calcium imaging on cultured myotubes. Statistical analysis was performed using Student’s t test or the Mann-Whitney test.

Results

We demonstrate the presence of MAP6 transcripts and proteins in skeletal muscle. Deletion of MAP6 results in a large number of muscle modifications: muscle weakness associated with slight muscle atrophy, alterations of microtubule network and sarcoplasmic reticulum organization, and reduction in calcium release.

Conclusion

Altogether, our results demonstrate that MAP6 is involved in skeletal muscle function. Its deletion results in alterations in skeletal muscle contraction which contribute to the global deleterious phenotype of the MAP6 KO mice. As MAP6 KO mouse line is a model for schizophrenia, our work points to a possible muscle weakness associated to some forms of schizophrenia.

Electronic supplementary material

The online version of this article (10.1186/s13395-018-0176-8) contains supplementary material, which is available to authorized users.

Dissociated features of social cognition altered in mouse models of schizophrenia: Focus on social dominance and acoustic communication

Social and communication impairments are common features of psychiatric disorders. Animal models of schizophrenia display various social deficits due to difference in tests, mouse strains and drugs. Moreover, communication deficits have not been studied. Our objectives were to assess and compare three major features of social cognition in different mouse models of schizophrenia: interest for a social stimulus, organization and acceptance of social contact, and acoustic communication to question whether mouse models for schizophrenia with social dysfunction also exhibit vocal communication defects. To achieve these aims we treated acutely C57BL/6J mice either with MK-801 or ketamine and tested WT and microtubule-associated protein 6 -MAP6- KO mice in two complementary social tasks: the 3-chamber test which measures social motivation and the social interaction task -SIT- which relies on prefrontal cortex activity and measures the ability to organize and respond to a real interaction, and which promotes ultrasonic vocalizations. Our results reveal that schizophrenia models have intact interest for a social stimulus in the 3-chamber test. However, thanks to principal component analyses of social interaction data, we demonstrate that social motivation and the ability to act socially rely on distinct mechanisms in revealing a decrease in dominance and communication in pharmacological schizophrenia models along with social withdraw, classically observed in schizophrenia, in MK-801 model. In this latter model, some social parameters can be significantly improved by aripiprazole, an atypical antipsychotic. Our social protocol, combined with fine-tuned analysis, is expected to provide an innovative framework for testing future treatments in preclinical models. This article is part of the Special Issue entitled 'The neuropharmacology of social behavior: from bench to bedside'.

A key function for microtubule-associated-protein 6 in activity-dependent stabilisation of actin filaments in dendritic spines

Emerging evidence indicates that microtubule-associated proteins (MAPs) are implicated in synaptic function; in particular, mice deficient for MAP6 exhibit striking deficits in plasticity and cognition. How MAP6 connects to plasticity mechanisms is unclear. Here, we address the possible role of this protein in dendritic spines. We find that in MAP6-deficient cortical and hippocampal neurons, maintenance of mature spines is impaired, and can be restored by expressing a stretch of the MAP6 sequence called Mc modules. Mc modules directly bind actin filaments and mediate activity-dependent stabilisation of F-actin in dendritic spines, a key event of synaptic plasticity. In vitro, Mc modules enhance actin filament nucleation and promote the formation of stable, highly ordered filament bundles. Activity-induced phosphorylation of MAP6 likely controls its transfer to the spine cytoskeleton. These results provide a molecular explanation for the role of MAP6 in cognition, enlightening the connection between cytoskeletal dysfunction, synaptic impairment and neuropsychiatric illnesses.

Microtubule-associated protein 6 (MAP6) is known to be important for synaptic plasticity and cognition, supposedly via interaction with microtubules. Here, the authors found that MAP6 is crucial for the stabilisation of enlarged synapses through its association with a different cytoskeletal element, actin.

3D imaging of the brain morphology and connectivity defects in a model of psychiatric disorders: MAP6-KO mice

In the central nervous system, microtubule-associated protein 6 (MAP6) is expressed at high levels and is crucial for cognitive abilities. The large spectrum of social and cognitive impairments observed in MAP6-KO mice are reminiscent of the symptoms observed in psychiatric diseases, such as schizophrenia, and respond positively to long-term treatment with antipsychotics. MAP6-KO mice have therefore been proposed to be a useful animal model for these diseases. Here, we explored the brain anatomy in MAP6-KO mice using high spatial resolution 3D MRI, including a volumetric T_1w method to image brain structures, and Diffusion Tensor Imaging (DTI) for white matter fiber tractography. 3D DTI imaging of neuronal tracts was validated by comparing results to optical images of cleared brains. Changes to brain architecture included reduced volume of the cerebellum and the thalamus and altered size, integrity and spatial orientation of some neuronal tracks such as the anterior commissure, the mammillary tract, the corpus callosum, the corticospinal tract, the fasciculus retroflexus and the fornix. Our results provide information on the neuroanatomical defects behind the neurological phenotype displayed in the MAP6-KO mice model and especially highlight a severe damage of the corticospinal tract with defasciculation at the location of the pontine nuclei.

Potential Role of Microtubule Stabilizing Agents in Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs) are characterized by neuroanatomical abnormalities indicative of corticogenesis disturbances. At the basis of NDDs cortical abnormalities, the principal developmental processes involved are cellular proliferation, migration and differentiation. NDDs are also considered “synaptic disorders” since accumulating evidence suggests that NDDs are developmental brain misconnection syndromes characterized by altered connectivity in local circuits and between brain regions. Microtubules and microtubule-associated proteins play a fundamental role in the regulation of basic neurodevelopmental processes, such as neuronal polarization and migration, neuronal branching and synaptogenesis. Here, the role of microtubule dynamics will be elucidated in regulating several neurodevelopmental steps. Furthermore, the correlation between abnormalities in microtubule dynamics and some NDDs will be described. Finally, we will discuss the potential use of microtubule stabilizing agents as a new pharmacological intervention for NDDs treatment.

Disruptions of Sleep/Wake Patterns in the Stable Tubule Only Polypeptide (STOP) Null Mouse Model of Schizophrenia

Disruption of sleep/wake cycles is common in patients with schizophrenia and correlates with cognitive and affective abnormalities. Mice deficient in stable tubule only polypeptide (STOP) show cognitive, behavioral, and neurobiological deficits that resemble those seen in patients with schizophrenia, but little is known about their sleep phenotype. We characterized baseline sleep/wake patterns and recovery sleep following sleep deprivation in STOP null mice. Polysomnography was conducted in adult male STOP null and wild-type (WT) mice under a 12:12 hours light:dark cycle before, during, and after 6 hours of sleep deprivation during the light phase. At baseline, STOP null mice spent more time awake and less time in non-rapid eye movement sleep (NREMS) over a 24-hour period, with more frequent transitions between wake and NREMS, compared to WT mice, especially during the dark phase. The distributions of wake, NREMS and REMS across the light and the dark phases differed by genotype, and so did features of the electroencephalogram (EEG). Following sleep deprivation, both genotypes showed homeostatic increases in sleep duration, with no significant genotype differences in the initial compensatory increase in sleep intensity (EEG delta power). These results indicate that STOP null mice sleep less overall, and their sleep and wake periods are more fragmented than those of WT mice. These features in STOP null mice are consistent with the sleep patterns observed in patients with schizophrenia.

-NMDA R/+VDR pharmacological phenotype as a novel therapeutic target in relieving motor-cognitive impairments in Parkinsonism

BACKGROUND

Parkinsonism describes Parkinson's disease and other associated degenerative changes in the brain resulting in movement disorders. The motor cortex, extrapyramidal tracts and nigrostriatal tract are brain regions forming part of the motor neural system and are primary targets for drug or chemotoxins induced Parkinsonism. The cause of Parkinsonism has been described as wide and elusive, however, environmental toxins and drugs accounts for large percentage of spontaneous cases in humans. A common mechanism in the cause and progression of drug/chemotoxin induced Parkinsonism involves calcium signalling in; oxidative stress, autophagy, cytoskeletal instability and excitotoxicity .

AIM

This study sets to investigate the effect of targeting calcium controlling receptors, specifically activation of Vitamin D3 receptor (VDR) and inhibition of N-Methyl-D-Aspartate Receptor (NMDAR) in the motor cortex of mice model of drug induced Parkinsonism. Also we demonstrated how these interventions improved neural activity, cytoskeleton, glia/neuron count and motor-cognitive functions in vivo.

METHODS

Adult mice were separated into six groups of n = 5 animals each. Body weight (5 mg/kg) of haloperidol was administered intraperitoneally for 7 days to block dopaminergic D2 receptors and induce degeneration in the motor cortex following which an intervention of VDR agonist (VDRA), and (or) NMDAR inhibitor was administered for 7 days. A set of control animals received normal saline while a separate group of control animals received the combined intervention of VDRA and NMDAR inhibitor without prior treatment with haloperidol. Behavioral tests for motor and cognitive functions were carried out at the end of the treatment and intervention periods. Subsequently, neural activity in the motor cortex was recorded in vivo using unilateral wire electrodes. We also employed immunohistochemistry to demonstrate neuron, glia, neurofilament and proliferation in the motor cortex after haloperidol treatment and the intervention.

RESULT/DISCUSSION

We observed a decline in motor function and memory index in the haloperidol treatment group when compared with the control. Similarly, there was a decline in neural activity in the motor cortex (a reduced depolarization peak frequency). General cell loss (neuron and glia) and depletion of neurofilament were characteristic anatomical changes seen in the motor cortex of this group. However, Vitamin D3 intervention facilitated an improvement in motor-cognitive function, neural activity, glia/neuron survival and neurofilament expression. NMDAR inhibition and the combined intervention improved motor-cognitive functions but not as significant as values observed in VDRA intervention. Interestingly, animals treated with the combined intervention without prior haloperidol treatment showed a decline in motor function and neural activity.

CONCLUSION

Our findings suggest that calcium mediated toxicity is primary to the cause and progression of Parkinsonism and targeting receptors that primarily modulates calcium reduces the morphological and behavioral deficits in drug induced Parkinsonism. VDR activation was more effective than NMDAR inhibition and a combined intervention. We conclude that targeting VDR is key for controlling calcium toxicity in drug/chemotoxin induced Parkinsonism.

Microtubule-associated protein 6 mediates neuronal connectivity through Semaphorin 3E-dependent signalling for axonal growth

Structural microtubule associated proteins (MAPs) stabilize microtubules, a property that was thought to be essential for development, maintenance and function of neuronal circuits. However, deletion of the structural MAPs in mice does not lead to major neurodevelopment defects. Here we demonstrate a role for MAP6 in brain wiring that is independent of microtubule binding. We find that MAP6 deletion disrupts brain connectivity and is associated with a lack of post-commissural fornix fibres. MAP6 contributes to fornix development by regulating axonal elongation induced by Semaphorin 3E. We show that MAP6 acts downstream of receptor activation through a mechanism that requires a proline-rich domain distinct from its microtubule-stabilizing domains. We also show that MAP6 directly binds to SH3 domain proteins known to be involved in neurite extension and semaphorin function. We conclude that MAP6 is critical to interface guidance molecules with intracellular signalling effectors during the development of cerebral axon tracts.

Loss of the structural microtubule-associated protein 6 (MAP6) leads to neuronal differentiation defects that are independent of MAP6's microtubule-binding properties. Here the authors establish a functional link between MAP6 and Semaphorin 3E signalling for proper formation of the fornix of the brain.

Effects of antipsychotic D2 antagonists on long-term potentiation in animals and implications for human studies

In people with schizophrenia, cognitive abilities - including memory - are strongly associated with functional outcome. Long-term potentiation (LTP) is a form of neuroplasticity that is believed to be the physiological basis for memory. It has been postulated that antipsychotic medication can impair long-term potentiation and cognition by altering dopaminergic transmission. Thus, a systematic review was performed in order to assess the relationship between antipsychotics and D2 antagonists on long-term potentiation. The majority of studies on LTP and antipsychotics have found that acute administration of antipsychotics was associated with impairments in LTP in wild-type animals. In contrast, chronic administration and acute antipsychotics in animal models of schizophrenia were not. Typical and atypical antipsychotics and other D2 antagonists behaved similarly, with the exception of clozapine and olanzapine. Clozapine caused potentiation independent of tetanization, while olanzapine facilitated tetanus-induced potentiation. These studies are limited in their ability to model the effects of antipsychotics in patients with schizophrenia as they were largely performed in wild-type animals as opposed to humans with schizophrenia, and assessed after acute rather than chronic treatment. Further studies using patients with schizophrenia receiving chronic antipsychotic treatment are needed to better understand the effects of these medications in this population.

Neuronal transport defects of the MAP6 KO mouse - a model of schizophrenia - and alleviation by Epothilone D treatment, as observed using MEMRI

The MAP6 (microtubule-associated protein 6) KO mouse is a microtubule-deficient model of schizophrenia that exhibits severe behavioral disorders that are associated with synaptic plasticity anomalies. These defects are alleviated not only by neuroleptics, which are the gold standard molecules for the treatment of schizophrenia, but also by Epothilone D (Epo D), which is a microtubule-stabilizing molecule. To compare the neuronal transport between MAP6 KO and wild-type mice and to measure the effect of Epo D treatment on neuronal transport in KO mice, MnCl2 was injected in the primary somatosensory cortex. Then, using manganese-enhanced magnetic resonance imaging (MEMRI), we followed the propagation of Mn(2+) through axonal tracts and brain regions that are connected to the somatosensory cortex. In MAP6 KO mice, the measure of the MRI relative signal intensity over 24h revealed that the Mn(2+) transport rate was affected with a stronger effect on long-range and polysynaptic connections than in short-range and monosynaptic tracts. The chronic treatment of MAP6 KO mice with Epo D strongly increased Mn(2+) propagation within both mono- and polysynaptic connections. Our results clearly indicate an in vivo deficit in neuronal Mn(2+) transport in KO MAP6 mice, which might be due to both axonal transport defects and synaptic transmission impairments. Epo D treatment alleviated the axonal transport defects, and this improvement most likely contributes to the positive effect of Epo D on behavioral defects in KO MAP6 mice.

Postmortem brain: an underutilized substrate for studying severe mental illness

We propose that postmortem tissue is an underutilized substrate that may be used to translate genetic and/or preclinical studies, particularly for neuropsychiatric illnesses with complex etiologies. Postmortem brain tissues from subjects with schizophrenia have been extensively studied, and thus serve as a useful vehicle for illustrating the challenges associated with this biological substrate. Schizophrenia is likely caused by a combination of genetic risk and environmental factors that combine to create a disease phenotype that is typically not apparent until late adolescence. The complexity of this illness creates challenges for hypothesis testing aimed at understanding the pathophysiology of the illness, as postmortem brain tissues collected from individuals with schizophrenia reflect neuroplastic changes from a lifetime of severe mental illness, as well as treatment with antipsychotic medications. While there are significant challenges with studying postmortem brain, such as the postmortem interval, it confers a translational element that is difficult to recapitulate in animal models. On the other hand, data derived from animal models typically provide specific mechanistic and behavioral measures that cannot be generated using human subjects. Convergence of these two approaches has led to important insights for understanding molecular deficits and their causes in this illness. In this review, we discuss the problem of schizophrenia, review the common challenges related to postmortem studies, discuss the application of biochemical approaches to this substrate, and present examples of postmortem schizophrenia studies that illustrate the role of the postmortem approach for generating important new leads for understanding the pathophysiology of severe mental illness.

Reduced expression of STOP/MAP6 in mice leads to cognitive deficits

BACKGROUND

STOP/MAP6 null (KO) mice recapitulate behavioral abnormalities related to positive and negative symptoms and cognitive deficits of schizophrenia. Here, we investigated whether decreased expression of STOP/MAP6 proteins in heterozygous mice (only one allele expressed) would result in abnormal behavior related to those displayed by STOP null mice.

METHODS

Using a comprehensive test battery, we investigated the behavioral phenotype of STOP heterozygous (Het) mice compared with STOP KO and wild type (WT) mice on animals raised either in standard conditions (controls) or submitted to maternal deprivation.

RESULTS

Control Het mice displayed prominent deficits in social interaction and learning, resembling KO mice. In contrast, they exhibited short-lasting locomotor hyperreactivity to acute mild stress and no impaired locomotor response to amphetamine, much like WT mice. Additionally, perinatal stress deteriorated Het mouse phenotype by exacerbating alterations related to positive symptoms such as their locomotor reactivity to acute mild stress and psychostimulant challenge.

CONCLUSION

Results show that the dosage of susceptibility genes modulates their putative phenotypic contribution and that STOP expression has a high penetrance on cognitive abilities. Hence, STOP Het mice might be useful to investigate cognitive defects related to those observed in mental diseases and ultimately might be a valuable experimental model to evaluate preventive treatments.

Structural basis for the association of MAP6 protein with microtubules and its regulation by calmodulin

Microtubules are highly dynamic αβ-tubulin polymers. In vitro and in living cells, microtubules are most often cold- and nocodazole-sensitive. When present, the MAP6/STOP family of proteins protects microtubules from cold- and nocodazole-induced depolymerization but the molecular and structure determinants by which these proteins stabilize microtubules remain under debate. We show here that a short protein fragment from MAP6-N, which encompasses its Mn1 and Mn2 modules (MAP6(90-177)), recapitulates the function of the full-length MAP6-N protein toward microtubules, i.e. its ability to stabilize microtubules in vitro and in cultured cells in ice-cold conditions or in the presence of nocodazole. We further show for the first time, using biochemical assays and NMR spectroscopy, that these effects result from the binding of MAP6(90-177) to microtubules with a 1:1 MAP6(90-177):tubulin heterodimer stoichiometry. NMR data demonstrate that the binding of MAP6(90-177) to microtubules involve its two Mn modules but that a single one is also able to interact with microtubules in a closely similar manner. This suggests that the Mn modules represent each a full microtubule binding domain and that MAP6 proteins may stabilize microtubules by bridging tubulin heterodimers from adjacent protofilaments or within a protofilament. Finally, we demonstrate that Ca(2+)-calmodulin competes with microtubules for MAP6(90-177) binding and that the binding mode of MAP6(90-177) to microtubules and Ca(2+)-calmodulin involves a common stretch of amino acid residues on the MAP6(90-177) side. This result accounts for the regulation of microtubule stability in cold condition by Ca(2+)-calmodulin.

The effects of antipsychotics on behavioral abnormalities of the Gunn rat (unconjugated hyperbilirubinemia rat), a rat model of schizophrenia

BACKGROUND

There have been reports of a positive relationship between schizophrenia and hyperbilirubinemia. Patients with schizophrenia show a significantly higher frequency of hyperbilirubinemia than patients suffering from other psychiatric disorders and when compared to the general population. Previously we observed that patients suffering from schizophrenia frequently present an elevated unconjugated bilirubin plasma concentration, when admitted to the hospital. In addition it was recently reported that unconjugated bilirubin exhibited neurotoxicity in the developing nervous system. We also reported that Gunn rats, which tend to show a high frequency of hyperbilirubinemia, may be used as an animal model of schizophrenia. In the present study, we assessed the effects of antipsychotics on Gunn rat behavioral abnormalities.

METHODS

We examined the behavior of Gunn rats after treatment with risperidone (0.1mg/kg), haloperidol (0.2mg/kg), or aripiprazole (0.4mg/kg) using an open-field test, social interaction test and a prepulse inhibition (PPI) test.

RESULTS

The administration of antipsychotics alleviated behavioral abnormalities, mimicking some positive and negative symptoms and cognitive defects of schizophrenia. The pharmacological reaction of Gunn rats to antipsychotics echoes the pharmacological response of humans to such antipsychotics.

CONCLUSIONS

Our study suggested that the Gunn rat may be useful as a preclinical model of schizophrenia with which to evaluate the pharmacological properties of antipsychotics. The results obtained to date have been encouraging and warrant further research.

Effects of antipsychotic drugs on the expression of synaptic proteins and dendritic outgrowth in hippocampal neuronal cultures

Recent evidence has suggested that atypical antipsychotic drugs regulate synaptic plasticity. We investigated whether some atypical antipsychotic drugs (olanzapine, aripiprazole, quetiapine, and ziprasidone) altered the expression of synapse-associated proteins in rat hippocampal neuronal cultures under toxic conditions induced by B27 deprivation. A typical antipsychotic, haloperidol, was used for comparison. We measured changes in the expression of various synaptic proteins including postsynaptic density protein-95 (PSD-95), brain-derived neurotrophic factor (BDNF), and synaptophysin (SYP). Then we examined whether these drugs affected the dendritic morphology of hippocampal neurons. We found that olanzapine, aripiprazole, and quetiapine, but not haloperidol, significantly hindered the B27 deprivation-induced decrease in the levels of these synaptic proteins. Ziprasidone did not affect PSD-95 or BDNF levels, but significantly increased the levels of SYP under B27 deprivation conditions. Moreover, olanzapine and aripiprazole individually significantly increased the levels of PSD-95 and BDNF, respectively, even under normal conditions, whereas haloperidol decreased the levels of PSD-95. These drugs increased the total outgrowth of hippocampal dendrites via PI3K signaling, whereas haloperidol had no effect in this regard. Together, these results suggest that the up-regulation of synaptic proteins and dendritic outgrowth may represent key effects of some atypical antipsychotic drugs but that haloperidol may be associated with distinct actions.

Both chronic treatments by epothilone D and fluoxetine increase the short-term memory and differentially alter the mood status of STOP/MAP6 KO mice

Recent evidence underlines the crucial role of neuronal cytoskeleton in the pathophysiology of psychiatric diseases. In this line, the deletion of STOP/MAP6 (Stable Tubule Only Polypeptide), a microtubule-stabilizing protein, triggers various neurotransmission and behavioral defects, suggesting that STOP knockout (KO) mice could be a relevant experimental model for schizoaffective symptoms. To establish the predictive validity of such a mouse line, in which the brain serotonergic tone is dramatically imbalanced, the effects of a chronic fluoxetine treatment on the mood status of STOP KO mice were characterized. Moreover, we determined the impact, on mood, of a chronic treatment by epothilone D, a taxol-like microtubule-stabilizing compound that has previously been shown to improve the synaptic plasticity deficits of STOP KO mice. We demonstrated that chronic fluoxetine was either antidepressive and anxiolytic, or pro-depressive and anxiogenic, depending on the paradigm used to test treated mutant mice. Furthermore, control-treated STOP KO mice exhibited paradoxical behaviors, compared with their clear-cut basal mood status. Paradoxical fluoxetine effects and control-treated STOP KO behaviors could be because of their hyper-reactivity to acute and chronic stress. Interestingly, both epothilone D and fluoxetine chronic treatments improved the short-term memory of STOP KO mice. Such treatments did not affect the serotonin and norepinephrine transporter densities in cerebral areas of mice. Altogether, these data demonstrated that STOP KO mice could represent a useful model to study the relationship between cytoskeleton, mood, and stress, and to test innovative mood treatments, such as microtubule-stabilizing compounds.

The deletion of STOP/MAP6 protein in mice triggers highly altered mood and impaired cognitive performances

The microtubule-associated Stable Tubulie Only Polypeptide (STOP; also known as MAP6) protein plays a key role in neuron architecture and synaptic plasticity, the dysfunctions of which are thought to be implicated in the pathophysiology of psychiatric diseases. The deletion of STOP in mice leads to severe disorders reminiscent of several schizophrenia-like symptoms, which are also associated with differential alterations of the serotonergic tone in somas versus terminals. In STOP knockout (KO) compared with wild-type mice, serotonin (5-HT) markers are found to be markedly accumulated in the raphe nuclei and, in contrast, deeply depleted in all serotonergic projection areas. In the present study, we carefully examined whether the 5-HT imbalance would lead to behavioral consequences evocative of mood and/or cognitive disorders. We showed that STOP KO mice exhibited depression-like behavior, associated with a decreased anxiety-status in validated paradigms. In addition, although STOP KO mice had a preserved very short-term memory, they failed to perform well in all other learning and memory tasks. We also showed that STOP KO mice exhibited regional imbalance of the norepinephrine tone as observed for 5-HT. As a consequence, mutant mice were hypersensitive to acute antidepressants with different selectivity. Altogether, these data indicate that the deletion of STOP protein in mice caused deep alterations in mood and cognitive performances and that STOP protein might have a crucial role in the 5-HT and norepinephrine networks development.

Mutant mouse models in evaluating novel approaches to antipsychotic treatment

In this review we consider the application of mutant mouse phenotypes to the study of psychotic illness in general and schizophrenia in particular, as they relate to behavioral, psychopharmacological, and cellular phenotypes of putative import for antipsychotic drug development. Mutant models appear to be heuristic at two main levels; firstly, by indicating the functional roles of neuronal components thought to be of relevance to the putative pathobiology of psychotic illness, they help resolve overt behavioral and underlying cellular processes regulated by those neuronal components; secondly, by indicating the functional roles of genes associated with risk for psychotic illness, they help resolve overt behavioral and underlying cellular processes regulated by those risk genes. We focus initially on models of dopaminergic and glutamatergic dysfunction. Then, we consider advances in the genetics of schizophrenia and mutant models relating to replicable risk genes. Lastly, we extend this discussion by exemplifying two new variant approaches in mutant mice that may serve as prototypes for advancing antipsychotic drug development. There is continuing need not only to address numerous technical challenges but also to develop more "real-world" paradigms that reflect the milieu of gene × environment and gene × gene interactions that characterize psychotic illness and its response to antipsychotic drugs.

Deletion of CB2 cannabinoid receptor induces schizophrenia-related behaviors in mice

The possible role of the CB(2) receptor (CB(2)r) in psychiatric disorders has been considered. Several animal models use knockout (KO) mice that display schizophrenia-like behaviors and this study evaluated the role of CB(2)r in the regulation of such behaviors. Mice lacking the CB(2)r (CB(2)KO) were challenged in open field, light-dark box, elevated plus-maze, tail suspension, step down inhibitory avoidance, and pre-pulse inhibition tests (PPI). Furthermore, the effects of treatment with cocaine and risperidone were evaluated using the OF and the PPI test. Gene expression of dopamine D(2) (D(2)r), adrenergic-α(2C) (α(2C)r), serotonergic 5-HT(2A) and 5-HT(2C) receptors (5-HT(2A)r and 5-HT(2C)r) were studied by RT-PCR in brain regions related to schizophrenia. Deletion of CB(2)r decreased motor activity in the OF test, but enhanced response to acute cocaine and produced mood-related alterations, PPI deficit, and cognitive impairment. Chronic treatment with risperidone tended to impair PPI in WT mice, whereas it 'normalized' the PPI deficit in CB(2)KO mice. CB(2)KO mice presented increased D(2)r and α(2C)r gene expressions in the prefrontal cortex (PFC) and locus coeruleus (LC), decreased 5-HT(2C)r gene expression in the dorsal raphe (DR), and 5-HT(2A)r gene expression in the PFC. Chronic risperidone treatment in WT mice left α(2C)r gene expression unchanged, decreased D(2)r gene expression (15 μg/kg), and decreased 5-HT(2C)r and 5-HT(2A)r in PFC and DR. In CB(2)KO, the gene expression of D(2)r in the PFC, of α(2C)r in the LC, and of 5-HT(2C)r and 5-HT(2A)r in PFC was reduced; 5-HT(2C)r and 5-HT(2A)r gene expressions in DR were increased after treatment with risperidone. These results suggest that deletion of CB(2)r has a relation with schizophrenia-like behaviors. Pharmacological manipulation of CB(2)r may merit further study as a potential therapeutic target for the treatment of schizophrenia-related disorders.

Microtubules, schizophrenia and cognitive behavior: preclinical development of davunetide (NAP) as a peptide-drug candidate

NAP (davunetide) is an active fragment of activity-dependent neuroprotective protein (ADNP). ADNP and the homologous protein ADNP2 provide cell protection. ADNP is essential for brain formation, proper development and neuronal plasticity, all reported to be impaired in schizophrenia. ADNP haploinsufficiecy inhibits social and cognitive functions, major hallmarks in schizophrenia. Imbalance in ADNP/ADNP2 expression in the schizophrenia brain may impact disease progression. NAP treatment partly ameliorates ADNP haploinsufficiecy. The microtubule, stable tubule-only polypeptide (STOP)-deficient mice were shown to provide a reliable model for schizophrenia. Daily intranasal NAP treatment significantly decreased hyperactivity in STOP-deficient mice and protected visual memory, supporting further clinical development.

The deletion of the microtubule-associated STOP protein affects the serotonergic mouse brain network

The deletion of microtubule-associated protein stable tubule only polypeptide (STOP) leads to neuroanatomical, biochemical and severe behavioral alterations in mice, partly alleviated by antipsychotics. Therefore, STOP knockout (KO) mice have been proposed as a model of some schizophrenia-like symptoms. Preliminary data showed decreased brain serotonin (5-HT) tissue levels in STOP KO mice. As literature data demonstrate various interactions between microtubule-associated proteins and 5-HT, we characterized some features of the serotonergic neurotransmission in STOP KO mice. In the brainstem, mutant mice displayed higher tissue 5-HT levels and in vivo synthesis rate, together with marked increases in 5-HT transporter densities and 5-HT1A autoreceptor levels and electrophysiological sensitivity, without modification of the serotonergic soma number. Conversely, in projection areas, STOP KO mice exhibited lower 5-HT levels and in vivo synthesis rate, associated with severe decreases in 5-HT transporter densities, possibly related to reduced serotonergic terminals. Mutant mice also displayed a deficit of adult hippocampal neurogenesis, probably related to both STOP deletion and 5-HT depletion. Finally, STOP KO mice exhibited a reduced anxiety- and, probably, an increased helpness-status, that could be because of the strong imbalance of the serotonin neurotransmission between somas and terminals. Altogether, these data suggested that STOP deletion elicited peculiar 5-HT disconnectivity.

Loss of STOP protein impairs peripheral olfactory neurogenesis

Background

STOP (Stable Tubulin-Only Polypeptide) null mice show behavioral deficits, impaired synaptic plasticity, decrease in synaptic vesicular pools and disturbances in dopaminergic transmission, and are considered a neurodevelopmental model of schizophrenia. Olfactory neurons highly express STOP protein and are continually generated throughout life. Experimentally-induced loss of olfactory neurons leads to epithelial regeneration within two months, providing a useful model to evaluate the role played by STOP protein in adult olfactory neurogenesis.

Methodology/Principal Findings

Immunocytochemistry and electron microscopy were used to study the structure of the glomerulus in the main olfactory bulb and neurogenesis in the neurosensorial epithelia. In STOP null mice, olfactory neurons showed presynaptic swellings with tubulovesicular profiles and autophagic-like structures. In olfactory and vomeronasal epithelia, there was an increase in neurons turnover, as shown by the increase in number of proliferating, apoptotic and immature cells with no changes in the number of mature neurons. Similar alterations in peripheral olfactory neurogenesis have been previously described in schizophrenia patients. In STOP null mice, regeneration of the olfactory epithelium did not modify these anomalies; moreover, regeneration resulted in abnormal organisation of olfactory terminals within the olfactory glomeruli in STOP null mice.

Conclusions/Significance

In conclusion, STOP protein seems to be involved in the establishment of synapses in the olfactory glomerulus. Our results indicate that the olfactory system of STOP null mice is a well-suited experimental model (1) for the study of the mechanism of action of STOP protein in synaptic function/plasticity and (2) for pathophysiological studies of the mechanisms of altered neuronal connections in schizophrenia.

NAP (davunetide) enhances cognitive behavior in the STOP heterozygous mouse--a microtubule-deficient model of schizophrenia

NAP (generic name, davunetide) is an active fragment of activity-dependent neuroprotective protein (ADNP). ADNP-/- embryos exhibit CNS dysgenesis and die in utero. ADNP+/- mice survive but demonstrate cognitive dysfunction coupled with microtubule pathology. NAP treatment ameliorates, in part, ADNP-associated dysfunctions. The microtubule, stable tubule-only polypeptide (STOP) knockout mice were shown to provide a reliable model for schizophrenia. Here, STOP-/- as well as STOP+/- showed schizophrenia-like symptoms (hyperactivity) that were ameliorated by chronic treatment with the antipsychotic drug, clozapine. Daily intranasal NAP treatment significantly decreased hyperactivity in the STOP+/- mice and protected visual memory.

Nitric oxide synthase mediates the ability of darbepoetin alpha to improve the cognitive performance of STOP null mice

STOP (stable tubule only polypeptide) null mice display neurochemical and behavioral abnormalities that resemble several well-recognized features of schizophrenia. Recent evidence suggests that the hematopoietic growth factor erythropoietin improves the cognitive performance of schizophrenics. The mechanism, however, by which erythropoietin is able to improve the cognition of schizophrenics is unclear. To address this question, we first determined whether acute administration of the erythropoietin analog known as darbepoetin alpha (D. alpha) improved performance deficits of STOP null mice in the novel objective recognition task (NORT). NORT performance of STOP null mice, but not wild-type littermates, was enhanced 3 h after a single injection of D. alpha (25 microg/kg, i.p.). Improved NORT performance was accompanied by elevated NADPH diaphorase staining in the ventral hippocampus as well as medial and cortical aspects of the amygdala, indicative of increased nitric oxide synthase (NOS) activity in these structures. NOS generates the intracellular messenger nitric oxide (NO) implicated in learning and memory. In keeping with this hypothesis, D. alpha significantly increased NO metabolite levels (nitrate and nitrite, NOx) in the hippocampus of both wild-type and STOP null mice. The NOS inhibitor, N (G)-nitro-L- arginine methyl ester (L-NAME; 25 mg/kg, i.p.), completely reversed the increase in hippocampal NOx levels produced by D. alpha. Moreover, L-NAME also inhibited the ability of D. alpha to improve the NORT performance of STOP null mice. Taken together, these observations suggest D. alpha enhances the NORT performance of STOP null mice by increasing production of NO.