RESUMEN
Higher-order telencephalic circuitry has been suggested to be especially vulnerable to irradiation or other developmentally toxic impact. This report details the adult effects of prenatal irradiation at a sensitive time point on clinically relevant brain functions controlled by telencephalic regions, hippocampus (HPC), and prefrontal cortex (PFC). Pregnant C57Bl6/J mice were whole-body irradiated at embryonic day 11 (start of neurogenesis) with X-ray intensities of 0.0, 0.5, or 1.0 Gy. Female offspring completed a broad test battery of HPC-/PFC-controlled tasks that included cognitive performance, fear extinction, exploratory, and depression-like behaviors. We examined neural functions that are mechanistically related to these behavioral and cognitive changes, such as hippocampal field potentials and long-term potentiation, functional brain connectivity (by resting-state functional magnetic resonance imaging), and expression of HPC vesicular neurotransmitter transporters (by immunohistochemical quantification). Prenatally exposed mice displayed several higher-order dysfunctions, such as decreased nychthemeral activity, working memory defects, delayed extinction of threat-evoked response suppression as well as indications of perseverative behavior. Electrophysiological examination indicated impaired hippocampal synaptic plasticity. Prenatal irradiation also induced cerebral hypersynchrony and increased the number of glutamatergic HPC terminals. These changes in brain connectivity and plasticity could mechanistically underlie the irradiation-induced defects in higher telencephalic functions.
Asunto(s)
Efectos Tardíos de la Exposición Prenatal , Exposición a la Radiación , Animales , Conducta Animal/fisiología , Extinción Psicológica , Miedo/psicología , Femenino , Hipocampo/fisiología , Humanos , Ratones , Ratones Endogámicos C57BL , Plasticidad Neuronal , Embarazo , Efectos Tardíos de la Exposición Prenatal/patologíaRESUMEN
Learning has been proposed to coincide with changes in connections between brain regions. In the present study, we used resting-state fMRI (rsfMRI) to map brain-wide functional connectivity (FC) in mice that were trained in the hidden-platform version of the Morris water maze. C57BL6 mice were investigated in a small animal MRI scanner following 2, 10, or 15 days of acquisition learning, or 5 days of reversal learning. Spatial learning coincided with progressive and changing FC between telencephalic regions that have been implemented in spatial learning (such as hippocampus, cingulate, visual, and motor cortex). Search strategy assessment demonstrated that the use of cognitively advanced spatial strategies correlated positively with extensive telencephalic connectivity, whereas non-spatial strategies correlated negatively with connectivity. FC patterns were different and more extensive after reversal learning compared with after extended acquisition learning, which could explain why reversal learning has been shown to be more sensitive to subtle functional defects.
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Encéfalo/fisiología , Aprendizaje por Laberinto/fisiología , Aprendizaje Inverso/fisiología , Animales , Mapeo Encefálico , Femenino , Imagen por Resonancia Magnética , Ratones Endogámicos C57BL , Procesamiento Espacial/fisiologíaRESUMEN
BACKGROUND: Microglia play a central role in most neurological disorders, but the impact of microgliosis on brain environment and clinical functions is not fully understood. Mice lacking multifunctional protein-2 (MFP2), a pivotal enzyme in peroxisomal ß-oxidation, develop a fatal disorder characterized by motor problems similar to the milder form of MFP2 deficiency in humans. The hallmark of disease in mice is the chronic proliferation of microglia in the brain, but molecular pathomechanisms that drive rapid clinical deterioration in human and mice remain unknown. In the present study, we identified the effects of specific deletion of MFP2 from microglia in the brain on immune responses, neuronal functioning, and behavior. METHODS: We created a novel Cx3cr1-Mfp2-/- mouse model and studied the impact of MFP2 deficiency on microglial behavior at different ages using immunohistochemistry and real-time PCR. Pro- and anti-inflammatory responses of Mfp2-/- microglia were assessed in vitro and in vivo after stimulation with IL-1ß/INFγ and IL-4 (in vitro) and LPS and IL-4 (in vivo). Facial nerve axotomy was unilaterally performed in Cx3cr1-Mfp2-/- and control mice, and microglial functioning in response to neuronal injury was subsequently analyzed by histology and real-time PCR. Finally, neuronal function, motor function, behavior, and cognition were assessed using brainstem auditory evoked potentials, grip strength and inverted grid test, open field exploration, and passive avoidance learning, respectively. RESULTS: We found that Mfp2-/- microglia in a genetically intact brain environment adopt an inflammatory activated and proliferative state. In addition, we found that acute inflammatory and neuronal injury provoked normal responses of Mfp2-/- microglia in Cx3cr1-Mfp2-/- mice during the post-injury period. Despite chronic pro-inflammatory microglial reactivity, Cx3cr1-Mfp2-/- mice exhibited normal neuronal transmission, clinical performance, and cognition. CONCLUSION: Our data demonstrate that MFP2 deficiency in microglia causes intrinsic dysregulation of their inflammatory profile, which is not harmful to neuronal function, motor function, and cognition in mice during their first year of life.
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Encéfalo/patología , Inflamación/patología , Microglía/efectos de los fármacos , Microglía/metabolismo , Proteína-2 Multifuncional Peroxisomal/deficiencia , Animales , Animales Recién Nacidos , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Receptor 1 de Quimiocinas CX3C/metabolismo , Proteínas de Unión al Calcio/metabolismo , Proliferación Celular/efectos de los fármacos , Proliferación Celular/genética , Células Cultivadas , Modelos Animales de Enfermedad , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Potenciales Evocados Auditivos del Tronco Encefálico/genética , Conducta Exploratoria/efectos de los fármacos , Conducta Exploratoria/fisiología , Enfermedades del Nervio Facial/complicaciones , Enfermedades del Nervio Facial/patología , Lateralidad Funcional , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Fuerza de la Mano/fisiología , Inflamación/inducido químicamente , Interleucina-4/administración & dosificación , Lipopolisacáridos/toxicidad , Ratones , Ratones Transgénicos , Proteínas de Microfilamentos/metabolismo , Microglía/patología , Proteína-2 Multifuncional Peroxisomal/genéticaRESUMEN
Type 2 diabetes (T2DM) and obesity might increase the risk for AD by 2-fold. Different attempts to model the effect of diet-induced diabetes on AD pathology in transgenic animal models, resulted in opposite conclusions. Here, we used a novel knock-in mouse model for AD, which, differently from other models, does not overexpress any proteins. Long-term high fat diet treatment triggers a reduction in hippocampal N-acetyl-aspartate/myo-inositol metabolites ratio and impairs long term potentiation in hippocampal acute slices. Interestingly, these alterations do not correlate with changes in the core neuropathological features of AD, i.e. amyloidosis and Tau hyperphosphorylation. The data suggest that AD phenotypes associated with high fat diet treatment seen in other models for AD might be exacerbated because of the overexpressing systems used to study the effects of familial AD mutations. Our work supports the increasing insight that knock-in mice might be more relevant models to study the link between metabolic disorders and AD.
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Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/fisiopatología , Dieta Alta en Grasa/efectos adversos , Hipocampo/metabolismo , Hipocampo/fisiopatología , Potenciación a Largo Plazo/fisiología , Enfermedad de Alzheimer/patología , Animales , Glucemia/metabolismo , Dieta Alta en Grasa/tendencias , Hipocampo/patología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Técnicas de Cultivo de ÓrganosRESUMEN
Fear extinction is the well-known process of fear reduction through repeated re-exposure to a feared stimulus without the aversive outcome. The last two decades have witnessed a surge of interest in extinction learning. First, extinction learning is observed across species, and especially research on rodents has made great strides in characterising the physical substrate underlying extinction learning. Second, extinction learning is considered of great clinical significance since it constitutes a crucial component of exposure treatment. While effective in reducing fear responding in the short term, extinction learning can lose its grip, resulting in a return of fear (i.e., laboratory model for relapse of anxiety symptoms in patients). Optimization of extinction learning is, therefore, the subject of intense investigation. It is thought that the success of extinction learning is, at least partly, determined by the mismatch between what is expected and what actually happens (prediction error). However, while much of our knowledge about the neural circuitry of extinction learning and factors that contribute to successful extinction learning comes from animal models, translating these findings to humans has been challenging for a number of reasons. Here, we present an overview of what is known about the animal circuitry underlying extinction of fear, and the role of prediction error. In addition, we conducted a systematic literature search to evaluate the degree to which state-of-the-art neuroimaging methods have contributed to translating these findings to humans. Results show substantial overlap between networks in animals and humans at a macroscale, but current imaging techniques preclude comparisons at a smaller scale, especially in sub-cortical areas that are functionally heterogeneous. Moreover, human neuroimaging shows the involvement of numerous areas that are not typically studied in animals. Results obtained in research aimed to map the extinction circuit are largely dependent on the methods employed, not only across species, but also across human neuroimaging studies. Directions for future research are discussed.
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Amígdala del Cerebelo/fisiología , Mapeo Encefálico , Condicionamiento Clásico/fisiología , Extinción Psicológica/fisiología , Miedo/fisiología , Hipocampo/fisiología , Corteza Prefrontal/fisiología , Investigación Biomédica Traslacional , Amígdala del Cerebelo/diagnóstico por imagen , Animales , Hipocampo/diagnóstico por imagen , Humanos , Corteza Prefrontal/diagnóstico por imagenRESUMEN
Alpha-mannosidosis is a glycoproteinosis caused by deficiency of lysosomal acid alpha-mannosidase (LAMAN), which markedly affects neurons of the central nervous system (CNS), and causes pathognomonic intellectual dysfunction in the clinical condition. Cognitive improvement consequently remains a major therapeutic objective in research on this devastating genetic error. Immune-tolerant LAMAN knockout mice were developed to evaluate the effects of enzyme replacement therapy (ERT) by prolonged administration of recombinant human enzyme. Biochemical evidence suggested that hippocampus may be one of the brain structures that benefits most from long-term ERT. In the present functional study, ERT was initiated in 2-month-old immune-tolerant alpha-mannosidosis mice and continued for 9months. During the course of treatment, mice were trained in the Morris water maze task to assess spatial-cognitive performance, which was related to synaptic plasticity recordings and hippocampal histopathology. Long-term ERT reduced primary substrate storage and neuroinflammation in hippocampus, and improved spatial learning after mid-term (10weeks+) and long-term (30weeks+) treatment. Long-term treatment substantially improved the spatial-cognitive abilities of alpha-mannosidosis mice, whereas the effects of mid-term treatment were more modest. Detailed analyses of spatial memory and spatial-cognitive performance indicated that even prolonged ERT did not restore higher cognitive abilities to the level of healthy mice. However, it did demonstrate marked therapeutic effects that coincided with increased synaptic connectivity, reflected by improvements in hippocampal CA3-CA1 long-term potentiation (LTP), expression of postsynaptic marker PSD-95 as well as postsynaptic density morphology. These experiments indicate that long-term ERT may hold promise, not only for the somatic defects of alpha-mannosidosis, but also to alleviate cognitive impairments of the disorder.
Asunto(s)
Cognición/efectos de los fármacos , Terapia de Reemplazo Enzimático , Hipocampo/efectos de los fármacos , Plasticidad Neuronal/efectos de los fármacos , Sinapsis/efectos de los fármacos , alfa-Manosidosis/tratamiento farmacológico , Animales , Cognición/fisiología , Modelos Animales de Enfermedad , Homólogo 4 de la Proteína Discs Large/metabolismo , Femenino , Hipocampo/patología , Hipocampo/fisiopatología , Humanos , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Aprendizaje por Laberinto/fisiología , Ratones Noqueados , Plasticidad Neuronal/fisiología , Proteínas Recombinantes/administración & dosificación , Memoria Espacial/efectos de los fármacos , Memoria Espacial/fisiología , Sinapsis/patología , Sinapsis/fisiología , Factores de Tiempo , alfa-Manosidasa/administración & dosificación , alfa-Manosidasa/deficiencia , alfa-Manosidasa/genética , alfa-Manosidosis/patología , alfa-Manosidosis/fisiopatologíaRESUMEN
The Morris water maze (MWM) spatial learning task has been demonstrated to involve a cognitive switch of action control to serve the transition from an early towards a late learning phase. However, the molecular mechanisms governing this switch are largely unknown. We employed MALDI MS imaging (MSI) to screen for changes in expression of small proteins in brain structures implicated in the different learning phases. We compared mice trained for 3days and 30days in the MWM, reflecting an early and a late learning phase in relation to the acquisition of a spatial learning task. An ion with m/z of 6724, identified as PEP-19/pcp4 by top-down tandem MS, was detected at higher intensity in the dorsal striatum of the late learning phase group compared with the early learning phase group. In addition, mass spectrometric analysis of synaptosomes confirmed the presence of PEP-19/pcp4 at the synapse. PEP-19/pcp4 has previously been identified as a critical determinant of synaptic plasticity in locomotor learning. Our findings extend PEP-19/pcp4 function to spatial learning in the forebrain and put MSI forward as a valid and unbiased research strategy for the discovery and identification of the molecular machinery involved in learning, memory and synaptic plasticity. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.
Asunto(s)
Proteínas del Tejido Nervioso/metabolismo , Aprendizaje Espacial/fisiología , Sinapsis/metabolismo , Sinaptosomas/metabolismo , Animales , Encéfalo/metabolismo , Encéfalo/fisiología , Femenino , Discapacidades para el Aprendizaje/metabolismo , Discapacidades para el Aprendizaje/patología , Locomoción/fisiología , Aprendizaje por Laberinto/fisiología , Memoria/fisiología , Ratones , Ratones Endogámicos C57BL , Plasticidad Neuronal/fisiología , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodosRESUMEN
Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by a functional deficiency of the lysosomal enzyme arylsulfatase A. The prevailing late-infantile variant of MLD is characterized by widespread and progressive demyelination of the central nervous system (CNS) causing death during childhood. In order to gain insight into the pathomechanism of the disease and to identify novel therapeutic targets, we analyzed neuroinflammation in two mouse models reproducing a mild, nondemyelinating, and a more severe, demyelinating, variant of MLD, respectively. Microgliosis and upregulation of cytokine/chemokine levels were clearly more pronounced in the demyelinating model. The analysis of the temporal cytokine/chemokine profiles revealed that the onset of demyelination is preceded by a sustained elevation of the macrophage inflammatory protein (MIP)-1α followed by an upregulation of MIP-1ß, monocyte chemotactic protein (MCP)-1, and several interleukins. The tumor necrosis factor (TNF)-α remains unchanged. Treatment of the demyelinating mouse model with the nonsteroidal anti-inflammatory drug simvastatin reduced neuroinflammation, improved the swimming performance and ataxic gait, and retarded demyelination of the spinal cord. Our data suggest that neuroinflammation is causative for demyelination in MLD mice and that anti-inflammatory treatment might be a novel therapeutic option to improve the CNS function of MLD patients.
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Sistema Nervioso Central/efectos de los fármacos , Inflamación/tratamiento farmacológico , Leucodistrofia Metacromática/tratamiento farmacológico , Simvastatina/administración & dosificación , Animales , Antiinflamatorios/administración & dosificación , Sistema Nervioso Central/fisiopatología , Quimiocina CCL2/biosíntesis , Quimiocina CCL4/biosíntesis , Enfermedades Desmielinizantes/tratamiento farmacológico , Enfermedades Desmielinizantes/patología , Modelos Animales de Enfermedad , Humanos , Inflamación/fisiopatología , Leucodistrofia Metacromática/inmunología , Ratones , Médula Espinal/efectos de los fármacos , Médula Espinal/patología , Factor de Necrosis Tumoral alfa/biosíntesisRESUMEN
The multiple memory systems hypothesis posits that dorsal striatum and hippocampus are central nodes in independent memory systems, supporting response-based and place-based learning, respectively. Although our understanding of the function of hippocampus within this framework is relatively well established, the contribution of dorsal striatum is less clear. This in part seems to be due to the heterogeneous nature of dorsal striatum, which receives extensive topographically organized projections from higher cortical areas. Here we quantified neural activity in the intact brain while mice and humans acquired analogous versions of the Morris water maze. We found that dorsomedial striatum and medial prefrontal cortex support the initial acquisition of what is typically considered a hippocampus-dependent spatial learning task. We suggest that the circuit involving dorsomedial striatum and medial prefrontal cortex identified here plays a more task-independent role in early learning than currently thought. Furthermore, our results demonstrate that dorsomedial and dorsolateral striatum serve fundamentally different roles during place learning. The remarkably high degree of anatomical overlap in brain function between mouse and human observed in our study emphasizes the extent of convergence achievable with a well-matched multilevel approach.
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Cuerpo Estriado/fisiología , Aprendizaje por Laberinto , Corteza Prefrontal/fisiología , Adulto , Animales , Femenino , Humanos , Hibridación in Situ , Ratones , Ratones Endogámicos C57BL , Adulto JovenRESUMEN
INTRODUCTION: In Alzheimer's disease (AD), pathologic amyloid-beta (Aß) is synaptotoxic and impairs neuronal function at the microscale, influencing brain networks at the macroscale before Aß deposition. The latter can be detected noninvasively, in vivo, using resting-state functional MRI (rsfMRI), a technique used to assess brain functional connectivity (FC). METHODS: RsfMRI was performed longitudinally in TG2576 and PDAPP mice, starting before Aß deposition to determine the earliest FC changes. Additionally, the role of pathologic Aß on early FC alterations was investigated by treating TG2576 mice with the 3D6 anti-Aß-antibody. RESULTS: Both transgenic models showed hypersynchronized FC before Aß deposition and hyposynchronized FC at later stages. Early anti-Aß treatment in TG2576 mice prevented hypersynchronous FC and the associated synaptic impairments and excitatory/inhibitory disbalances. DISCUSSION: Hypersynchrony of FC may be used as a new noninvasive read out of early AD and can be recovered by anti-Aß treatment, encouraging preventive treatment strategies in familial AD.
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Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/fisiopatología , Péptidos beta-Amiloides/antagonistas & inhibidores , Péptidos beta-Amiloides/metabolismo , Encéfalo/efectos de los fármacos , Encéfalo/fisiopatología , Enfermedad de Alzheimer/diagnóstico por imagen , Animales , Autoanticuerpos/farmacología , Encéfalo/diagnóstico por imagen , Mapeo Encefálico , Circulación Cerebrovascular/fisiología , Sincronización Cortical/fisiología , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Estudios Longitudinales , Imagen por Resonancia Magnética , Ratones Transgénicos , Vías Nerviosas/diagnóstico por imagen , Vías Nerviosas/fisiopatología , Fármacos Neuroprotectores/farmacología , Oxígeno/sangre , Placa Amiloide/diagnóstico por imagen , Placa Amiloide/fisiopatología , Placa Amiloide/prevención & control , Síntomas Prodrómicos , DescansoRESUMEN
Niemann-Pick disease type A (NPDA) is a fatal disease due to mutations in the acid sphingomyelinase (ASM) gene, which triggers the abnormal accumulation of sphingomyelin (SM) in lysosomes and the plasma membrane of mutant cells. Although the disease affects multiple organs, the impact on the brain is the most invalidating feature. The mechanisms responsible for the cognitive deficit characteristic of this condition are only partially understood. Using mice lacking the ASM gene (ASMko), a model system in NPDA research, we report here that high sphingomyelin levels in mutant neurons lead to low synaptic levels of phosphoinositide PI(4,5)P2 and reduced activity of its hydrolyzing phosphatase PLCγ, which are key players in synaptic plasticity events. In addition, mutant neurons have reduced levels of membrane-bound MARCKS, a protein required for PI(4,5)P2 membrane clustering and hydrolysis. Intracerebroventricular infusion of a peptide that mimics the effector domain of MARCKS increases the content of PI(4,5)P2 in the synaptic membrane and ameliorates behavioral abnormalities in ASMko mice.
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Encéfalo/metabolismo , Péptidos y Proteínas de Señalización Intracelular/uso terapéutico , Proteínas de la Membrana/uso terapéutico , Trastornos Mentales/tratamiento farmacológico , Trastornos Mentales/etiología , Enfermedad de Niemann-Pick Tipo A/complicaciones , Enfermedad de Niemann-Pick Tipo A/tratamiento farmacológico , Animales , Reacción de Prevención/efectos de los fármacos , Encéfalo/efectos de los fármacos , Encéfalo/patología , Modelos Animales de Enfermedad , Conducta Exploratoria/efectos de los fármacos , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Inyecciones Intraventriculares , Metabolismo de los Lípidos/efectos de los fármacos , Metabolismo de los Lípidos/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad Motora/efectos de los fármacos , Actividad Motora/genética , Fuerza Muscular/efectos de los fármacos , Fuerza Muscular/genética , Mutación/genética , Sustrato de la Proteína Quinasa C Rico en Alanina Miristoilada , Enfermedad de Niemann-Pick Tipo A/metabolismo , Enfermedad de Niemann-Pick Tipo A/patología , Fosfolipasa C gamma/metabolismo , Esfingomielina Fosfodiesterasa/genética , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismoRESUMEN
miR-29 is expressed strongly in the brain and alterations in expression have been linked to several neurological disorders. To further explore the function of this miRNA in the brain, we generated miR-29a/b-1 knockout animals. Knockout mice develop a progressive disorder characterized by locomotor impairment and ataxia. The different members of the miR-29 family are strongly expressed in neurons of the olfactory bulb, the hippocampus and in the Purkinje cells of the cerebellum. Morphological analysis showed that Purkinje cells are smaller and display less dendritic arborisation compared to their wildtype littermates. In addition, a decreased number of parallel fibers form synapses on the Purkinje cells. We identified several mRNAs significantly up-regulated in the absence of the miR-29a/b-1 cluster. At the protein level, however, the voltage-gated potassium channel Kcnc3 (Kv3.3) was significantly up-regulated in the cerebella of the miR-29a/b knockout mice. Dysregulation of KCNC3 expression may contribute to the ataxic phenotype.
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Ataxia/metabolismo , Cerebelo/metabolismo , MicroARNs/metabolismo , Células de Purkinje/metabolismo , Canales de Potasio Shaw/metabolismo , Animales , Conducta Animal , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad MotoraRESUMEN
Recent work has demonstrated that functional connectivity between remote brain regions can be modulated by task learning or the performance of an already well-learned task. Here, we investigated the extent to which initial learning and stable performance of a spatial navigation task modulates functional connectivity between subregions of hippocampus and striatum. Subjects actively navigated through a virtual water maze environment and used visual cues to learn the position of a fixed spatial location. Resting-state functional magnetic resonance imaging scans were collected before and after virtual water maze navigation in two scan sessions conducted 1 week apart, with a behavior-only training session in between. There was a large significant reduction in the time taken to intercept the target location during scan session 1 and a small significant reduction during the behavior-only training session. No further reduction was observed during scan session 2. This indicates that scan session 1 represented initial learning and scan session 2 represented stable performance. We observed an increase in functional connectivity between left posterior hippocampus and left dorsal caudate that was specific to scan session 1. Importantly, the magnitude of the increase in functional connectivity was correlated with offline gains in task performance. Our findings suggest cooperative interaction occurs between posterior hippocampus and dorsal caudate during awake rest following the initial phase of spatial navigation learning. Furthermore, we speculate that the increase in functional connectivity observed during awake rest after initial learning might reflect consolidation-related processing.
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Núcleo Caudado/fisiología , Hipocampo/fisiología , Aprendizaje por Laberinto/fisiología , Percepción Visual/fisiología , Adulto , Mapeo Encefálico , Señales (Psicología) , Femenino , Lateralidad Funcional , Humanos , Imagen por Resonancia Magnética , Vías Nerviosas/fisiología , Descanso , Procesamiento de Señales Asistido por Computador , Interfaz Usuario-Computador , Agua , Adulto JovenRESUMEN
BACKGROUND: Group III metabotropic glutamate receptors (mGlu4, mGlu7, mGlu8) display differential brain distribution, which suggests different behavioral functions. However, comparison across the available animal studies remains methodologically hazardous and controversial. The present report directly compares knockouts for each group III receptor subtype using a single behavioral test battery and multivariate analysis. METHODS: The behavioral phenotypes of C57BL/6J mice lacking mGlu4, mGlu7, or mGlu8 and their respective littermates were examined using a multimetric test battery, which included elements of neuromotor performance, exploratory behavior, and learning and memory. Multivariate statistical methods were used to identify subtype-specific behavioral profiles and variables that distinguished between these mouse lines. RESULTS: It generally appears that mGlu7 plays a significant role in hippocampus-dependent spatial learning and in some fear-related behaviors, whereas mGlu4 is most clearly involved in startle and motivational processes. Excepting its influence on body weight, the effect of mGlu8 deletion on behavior appears more subtle than that of the other group III receptors. These receptors have been proposed as potential drug targets for a variety of psychopathological conditions. CONCLUSION: On the basis of these controlled comparisons, we presently conclude that the different group III receptors indeed have quite distinct behavioral functions.
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Aprendizaje/fisiología , Memoria/fisiología , Actividad Motora/fisiología , Receptores de Glutamato Metabotrópico/metabolismo , Animales , Peso Corporal/efectos de los fármacos , Peso Corporal/fisiología , Conducta Exploratoria/fisiología , Miedo/fisiología , Femenino , Ratones Endogámicos C57BL , Ratones Noqueados , Motivación/genética , Motivación/fisiología , Actividad Motora/genética , Análisis Multivariante , Receptores de Glutamato Metabotrópico/genética , Reflejo de Sobresalto/genética , Reflejo de Sobresalto/fisiologíaRESUMEN
Humans can spontaneously create rules that allow them to efficiently generalize what they have learned to novel situations. An enduring question is whether rule-based generalization is uniquely human or whether other animals can also abstract rules and apply them to novel situations. In recent years, there have been a number of high-profile claims that animals such as rats can learn rules. Most of those claims are quite weak because it is possible to demonstrate that simple associative systems (which do not learn rules) can account for the behavior in those tasks. Using a procedure that allows us to clearly distinguish feature-based from rule-based generalization (the Shanks-Darby procedure), we demonstrate that adult humans show rule-based generalization in this task, while generalization in rats and pigeons was based on featural overlap between stimuli. In brief, when learning that a stimulus made of two components ("AB") predicts a different outcome than its elements ("A" and "B"), people spontaneously abstract an opposites rule and apply it to new stimuli (e.g., knowing that "C" and "D" predict one outcome, they will predict that "CD" predicts the opposite outcome). Rats and pigeons show the reverse behavior-they generalize what they have learned, but on the basis of similarity (e.g., "CD" is similar to "C" and "D", so the same outcome is predicted for the compound stimulus as for the components). Genuinely rule-based behavior is observed in humans, but not in rats and pigeons, in the current procedure.
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Columbidae/fisiología , Aprendizaje Discriminativo , Generalización Psicológica , Ratas/fisiología , Animales , Aprendizaje por Asociación , Femenino , Humanos , Masculino , Reconocimiento Visual de Modelos , Ratas Sprague-Dawley , Adulto JovenRESUMEN
Deficiency of glycosaminoglycan (GAG) degradation causes a subclass of lysosomal storage disorders called mucopolysaccharidoses (MPSs), many of which present with severe neuropathology. Critical steps in the degradation of the GAG heparan sulfate remain enigmatic. Here we show that the lysosomal arylsulfatase G (ARSG) is the long-sought glucosamine-3-O-sulfatase required to complete the degradation of heparan sulfate. Arsg-deficient mice accumulate heparan sulfate in visceral organs and the central nervous system and develop neuronal cell death and behavioral deficits. This accumulated heparan sulfate exhibits unique nonreducing end structures with terminal N-sulfoglucosamine-3-O-sulfate residues, allowing diagnosis of the disorder. Recombinant human ARSG is able to cleave 3-O-sulfate groups from these residues as well as from an authentic 3-O-sulfated N-sulfoglucosamine standard. Our results demonstrate the key role of ARSG in heparan sulfate degradation and strongly suggest that ARSG deficiency represents a unique, as yet unknown form of MPS, which we term MPS IIIE.
Asunto(s)
Arilsulfatasas/antagonistas & inhibidores , Mucopolisacaridosis/etiología , Sulfatasas/metabolismo , Animales , Conducta Animal , Ratones , Mucopolisacaridosis/enzimologíaRESUMEN
The metalloproteinase ADAM10 is of importance for Notch-dependent cortical brain development. The protease is tightly linked with α-secretase activity toward the amyloid precursor protein (APP) substrate. Increasing ADAM10 activity is suggested as a therapy to prevent the production of the neurotoxic amyloid ß (Aß) peptide in Alzheimer's disease. To investigate the function of ADAM10 in postnatal brain, we generated Adam10 conditional knock-out (A10cKO) mice using a CaMKIIα-Cre deleter strain. The lack of ADAM10 protein expression was evident in the brain cortex leading to a reduced generation of sAPPα and increased levels of sAPPß and endogenous Aß peptides. The A10cKO mice are characterized by weight loss and increased mortality after weaning associated with seizures. Behavioral comparison of adult mice revealed that the loss of ADAM10 in the A10cKO mice resulted in decreased neuromotor abilities and reduced learning performance, which were associated with altered in vivo network activities in the hippocampal CA1 region and impaired synaptic function. Histological and ultrastructural analysis of ADAM10-depleted brain revealed astrogliosis, microglia activation, and impaired number and altered morphology of postsynaptic spine structures. A defect in spine morphology was further supported by a reduction of the expression of NMDA receptors subunit 2A and 2B. The reduced shedding of essential postsynaptic cell adhesion proteins such as N-Cadherin, Nectin-1, and APP may explain the postsynaptic defects and the impaired learning, altered network activity, and synaptic plasticity of the A10cKO mice. Our study reveals that ADAM10 is instrumental for synaptic and neuronal network function in the adult murine brain.
Asunto(s)
Proteínas ADAM/deficiencia , Secretasas de la Proteína Precursora del Amiloide/deficiencia , Encéfalo/ultraestructura , Espinas Dendríticas/patología , Epilepsia/genética , Epilepsia/patología , Discapacidades para el Aprendizaje/patología , Proteínas de la Membrana/deficiencia , Sinapsis/patología , Proteína ADAM10 , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Animales Recién Nacidos , Encéfalo/patología , Cadherinas/metabolismo , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/genética , Moléculas de Adhesión Celular/metabolismo , Espinas Dendríticas/metabolismo , Modelos Animales de Enfermedad , Regulación del Desarrollo de la Expresión Génica/genética , Gliosis/genética , Discapacidades para el Aprendizaje/genética , Ratones , Ratones Transgénicos , Nectinas , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapsis/metabolismo , Sinapsis/ultraestructuraRESUMEN
Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by a functional deficiency of arylsulfatase A (ASA). Previous studies in ASA-knockout mice suggested enzyme replacement therapy (ERT) to be a promising treatment option. The mild phenotype of ASA-knockout mice did, however, not allow to examine therapeutic responses of the severe neurological symptoms that dominate MLD. We, therefore, generated an aggravated MLD mouse model displaying progressive demyelination and reduced nerve conduction velocity (NCV) and treated it by weekly intravenous injections of 20 mg/kg recombinant human ASA for 16 weeks. To analyze the stage-dependent therapeutic effects, ERT was initiated in a presymptomatic, early and progressed disease stage, at age 4, 8 and 12 months, respectively. Brain sulfatide storage, NCV and behavioral alterations were improved only in early, but not in late, treated mice showing a clear age-dependent efficacy of treatment. Hematopoietic stem cell transplantation (HSCT) for late-onset variants is the only therapeutic option for MLD to date. ERT resembles a part of the HSCT rationale, which is based on ASA supply by donor cells. Beyond ERT, our results, therefore, corroborate the clinical observation that HSCT is only effective when performed in early stages of disease.
Asunto(s)
Leucodistrofia Metacromática/genética , Leucodistrofia Metacromática/terapia , Animales , Células CHO , Cerebrósido Sulfatasa/genética , Cerebrósido Sulfatasa/metabolismo , Cricetinae , Modelos Animales de Enfermedad , Terapia de Reemplazo Enzimático , Terapia Genética , Ratones , Ratones Noqueados , Transfección , Resultado del TratamientoRESUMEN
Synaptic vesicle recycling involves AP-2/clathrin-mediated endocytosis, but it is not known whether the endosomal pathway is also required. Mice deficient in the tissue-specific AP-1-sigma1B complex have impaired synaptic vesicle recycling in hippocampal synapses. The ubiquitously expressed AP-1-sigma1A complex mediates protein sorting between the trans-Golgi network and early endosomes. Vertebrates express three sigma1 subunit isoforms: A, B and C. The expressions of sigma1A and sigma1B are highest in the brain. Synaptic vesicle reformation in cultured neurons from sigma1B-deficient mice is reduced upon stimulation, and large endosomal intermediates accumulate. The sigma1B-deficient mice have reduced motor coordination and severely impaired long-term spatial memory. These data reveal a molecular mechanism for a severe human X-chromosome-linked mental retardation.
Asunto(s)
Complejo 1 de Proteína Adaptadora/metabolismo , Endosomas/metabolismo , Aprendizaje , Memoria , Vesículas Sinápticas/metabolismo , Complejo 1 de Proteína Adaptadora/análisis , Complejo 1 de Proteína Adaptadora/genética , Animales , Conducta Animal , Células Cultivadas , Clatrina/metabolismo , Femenino , Expresión Génica , Hipocampo/citología , Humanos , Ratones , Ratones Noqueados , Actividad Motora , Neuronas/metabolismo , Isoformas de Proteínas/análisis , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismoRESUMEN
The amyloid peptides Aß(40) and Aß(42) of Alzheimer's disease are thought to contribute differentially to the disease process. Although Aß(42) seems more pathogenic than Aß(40), the reason for this is not well understood. We show here that small alterations in the Aß(42):Aß(40) ratio dramatically affect the biophysical and biological properties of the Aß mixtures reflected in their aggregation kinetics, the morphology of the resulting amyloid fibrils and synaptic function tested in vitro and in vivo. A minor increase in the Aß(42):Aß(40) ratio stabilizes toxic oligomeric species with intermediate conformations. The initial toxic impact of these Aß species is synaptic in nature, but this can spread into the cells leading to neuronal cell death. The fact that the relative ratio of Aß peptides is more crucial than the absolute amounts of peptides for the induction of neurotoxic conformations has important implications for anti-amyloid therapy. Our work also suggests the dynamic nature of the equilibrium between toxic and non-toxic intermediates.