RESUMEN
Ischemic stroke causes damage in the brain, and a slow buildup of adenosine is neuroprotective during ischemic injury. Spontaneous, transient adenosine signaling, lasting only 3 s per event, has been discovered that increases in frequency in the caudate-putamen during early stages of mild ischemia-reperfusion injury. However, spontaneous adenosine changes have not been studied in the hippocampus during ischemia, an area highly susceptible to stroke. Here, we investigated changes of spontaneous, transient adenosine in the CA1 region of rat hippocampus during three different models of the varied intensity of ischemia. During the early stages of the milder bilateral common carotid artery occlusion (BCCAO) model, there were fewer spontaneous, transient adenosine, but no change in the concentration of individual events. In contrast, during the moderate 2 vertebral artery occlusion (2VAO) and severe 4 vessel occlusion (4VO) models, both the frequency of spontaneous, transient adenosine and the average event adenosine concentration decreased. Blood flow measurements validate that the ischemia models decreased blood flow, and corresponding pathological changes were observed by transmission electron microscopy (TEM). 4VO occlusion showed the most severe damage in histology and BCCAO showed the least. Overall, our data suggest that there is no enhanced spontaneous adenosine release in the hippocampus during moderate and severe ischemia, which could be due to depletion of the rapidly releasable adenosine pool. Thus, during ischemic stroke, there are fewer spontaneous adenosine events that could inhibit neurotransmission, which might lead to more damage and less neuroprotection in the hippocampus CA1 region. Read the Editorial Highlight for this article on page 800.
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Adenosina/metabolismo , Isquemia Encefálica/metabolismo , Región CA1 Hipocampal/metabolismo , Región CA1 Hipocampal/ultraestructura , Circulación Cerebrovascular/fisiología , Gravedad del Paciente , Animales , Isquemia Encefálica/patología , Región CA1 Hipocampal/patología , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
Mitophagy alleviates neuronal damage after cerebral ischemia by selectively removing dysfunctional mitochondria. Phosphatase and tensin homolog (PTEN) induced putative kinase 1 (PINK1)/Parkin-mediated mitophagy is the most well-known type of mitophagy. However, little is known about the role of PINK1/Parkin-mediated mitophagy in ischemic tolerance induced by hypoxic postconditioning (HPC) with 8% O2 against transient global cerebral ischemia (tGCI). Hence, we aimed to test the hypothesis that HPC-mediated PINK1/Parkin-induced mitochondrial ubiquitination and promotes mitophagy, thus exerting neuroprotection in the hippocampal CA1 subregion against tGCI. We found that mitochondrial clearance was disturbed at the late phase of reperfusion after tGCI, which was reversed by HPC, as evidenced by the reduction of the translocase of outer mitochondrial membrane 20 homologs (TOMM20), translocase of inner mitochondrial membrane 23 (TIMM23) and heat shock protein 60 (HSP60) in CA1 after HPC. In addition, HPC further increased the ratio of LC3II/I in mitochondrial fraction and promoted the formation of mitophagosomes in CA1 neurons after tGCI. The administration of lysosome inhibitor chloroquine (CQ) intraperitoneally or mitophagy inhibitor (Mdivi-1) intracerebroventricularly abrogated HPC-induced mitochondrial turnover and neuroprotection in CA1 after tGCI. We also found that HPC activated PINK1/Parkin pathway after tGCI, as shown by the augment of mitochondrial PINK1 and Parkin and the promotion of mitochondrial ubiquitination in CA1. In addition, PINK1 or Parkin knockdown with small-interfering RNA (siRNA) suppressed the activation of PINK1/Parkin pathway and hampered mitochondrial clearance and attenuated neuroprotection induced by HPC, whereas PINK1 overexpression promoted PINK1/Parkin-mediated mitophagy and ameliorated neuronal damage in CA1 after tGCI. Taken together, the new finding in this study is that HPC-induced neuroprotection against tGCI through promoting mitophagy mediated by PINK1/Parkin-dependent pathway.
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Región CA1 Hipocampal/enzimología , Hipoxia/enzimología , Ataque Isquémico Transitorio/enzimología , Mitocondrias/enzimología , Mitofagia , Neuronas/enzimología , Proteínas Quinasas/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Animales , Región CA1 Hipocampal/ultraestructura , Modelos Animales de Enfermedad , Hipoxia/genética , Hipoxia/patología , Ataque Isquémico Transitorio/genética , Ataque Isquémico Transitorio/patología , Masculino , Mitocondrias/genética , Mitocondrias/ultraestructura , Neuronas/ultraestructura , Proteínas Quinasas/genética , Transporte de Proteínas , Ratas Wistar , Ubiquitina-Proteína Ligasas/genética , UbiquitinaciónRESUMEN
Three-dimensional (3D) reconstruction from electron microscopy (EM) datasets is a widely used tool that has improved our knowledge of synapse ultrastructure and organization in the brain. Rearrangements of synapse structure following maturation and in synaptic plasticity have been broadly described and, in many cases, the defective architecture of the synapse has been associated to functional impairments. It is therefore important, when studying brain connectivity, to map these rearrangements with the highest accuracy possible, considering the affordability of the different EM approaches to provide solid and reliable data about the structure of such a small complex. The aim of this work is to compare quantitative data from two dimensional (2D) and 3D EM of mouse hippocampal CA1 (apical dendrites), to define whether the results from the two approaches are consistent. We examined asymmetric excitatory synapses focusing on post synaptic density and dendritic spine area and volume as well as spine density, and we compared the results obtained with the two methods. The consistency between the 2D and 3D results questions the need-for many applications-of using volumetric datasets (costly and time consuming in terms of both acquisition and analysis), with respect to the more accessible measurements from 2D EM projections.
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Región CA1 Hipocampal/ultraestructura , Espinas Dendríticas/ultraestructura , Células Piramidales/ultraestructura , Animales , Imagenología Tridimensional , Ratones , Microscopía Electrónica , Sinapsis/ultraestructuraRESUMEN
The use and abuse of cannabis can be associated with significant pathophysiology, however, it remains unclear whether (1) acute administration of Δ-9-tetrahydrocannabinol (THC) during early adulthood alters the cannabinoid type 1 (CB1 ) receptor localization and expression in cells of the brain, and (2) THC produces structural brain changes. Here we use electron microscopy and a highly sensitive pre-embedding immunogold method to examine CB1 receptors in the hippocampus cornu ammonis subfield 1 (CA1) 30 min after male mice were exposed to a single THC injection (5 mg/kg). The findings show that acute exposure to THC can significantly decrease the percentage of CB1 receptor immunopositive terminals making symmetric synapses, mitochondria, and astrocytes. The percentage of CB1 receptor-labeled terminals forming asymmetric synapses was unaffected. Lastly, CB1 receptor expression was significantly lower at terminals of symmetric and asymmetric synapses as well as in mitochondria. Structurally, CA1 dendrites were significantly larger, and contained more spines and mitochondria following acute THC administration. The area of the dendritic spines, synaptic terminals, mitochondria, and astrocytes decreased significantly following acute THC exposure. Altogether, these results indicate that even a single THC exposure can have a significant impact on CB1 receptor expression, and can alter CA1 ultrastructure, within 30 min of drug exposure. These changes may contribute to the behavioral alterations experienced by young individuals shortly after cannabis intoxication.
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Región CA1 Hipocampal/metabolismo , Región CA1 Hipocampal/ultraestructura , Agonistas de Receptores de Cannabinoides/administración & dosificación , Dronabinol/administración & dosificación , Receptor Cannabinoide CB1/biosíntesis , Receptor Cannabinoide CB1/ultraestructura , Factores de Edad , Animales , Región CA1 Hipocampal/efectos de los fármacos , Inmunohistoquímica/métodos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Receptor Cannabinoide CB1/agonistasRESUMEN
Alzheimer's disease is the most common form of dementia, characterized by a persistent and progressive impairment of cognitive functions. Alzheimer's disease is typically associated with extracellular deposits of amyloid-ß peptide and accumulation of abnormally phosphorylated tau protein inside neurons (amyloid-ß and neurofibrillary pathologies). It has been proposed that these pathologies cause neuronal degeneration and synaptic alterations, which are thought to constitute the major neurobiological basis of cognitive dysfunction in Alzheimer's disease. The hippocampal formation is especially vulnerable in the early stages of Alzheimer's disease. However, the vast majority of electron microscopy studies have been performed in animal models. In the present study, we performed an extensive 3D study of the neuropil to investigate the synaptic organization in the stratum pyramidale and radiatum in the CA1 field of Alzheimer's disease cases with different stages of the disease, using focused ion beam/scanning electron microscopy (FIB/SEM). In cases with early stages of Alzheimer's disease, the synapse morphology looks normal and we observed no significant differences between control and Alzheimer's disease cases regarding the synaptic density, the ratio of excitatory and inhibitory synapses, or the spatial distribution of synapses. However, differences in the distribution of postsynaptic targets and synaptic shapes were found. Furthermore, a lower proportion of larger excitatory synapses in both strata were found in Alzheimer's disease cases. Individuals in late stages of the disease suffered the most severe synaptic alterations, including a decrease in synaptic density and morphological alterations of the remaining synapses. Since Alzheimer's disease cases show cortical atrophy, our data indicate a reduction in the total number (but not the density) of synapses at early stages of the disease, with this reduction being much more accentuated in subjects with late stages of Alzheimer's disease. The observed synaptic alterations may represent a structural basis for the progressive learning and memory dysfunctions seen in Alzheimer's disease cases.
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Enfermedad de Alzheimer/patología , Región CA1 Hipocampal/ultraestructura , Neuronas/ultraestructura , Sinapsis/ultraestructura , Femenino , Humanos , Imagenología Tridimensional , Masculino , Microscopía Electrónica de RastreoRESUMEN
The hippocampus plays a key role in contextual conditioning and has been proposed as an important component of the cocaine addiction brain circuit. To gain knowledge about cocaine-induced alterations in this circuit, we used focused ion beam milling/scanning electron microscopy to reveal and quantify the three-dimensional synaptic organization of the neuropil of the stratum radiatum of the rat CA1, under normal circumstances and after cocaine-self administration (SA). Most synapses are asymmetric (excitatory), macular-shaped, and in contact with dendritic spine heads. After cocaine-SA, the size and the complexity of the shape of both asymmetric and symmetric (inhibitory) synapses increased but no changes were observed in the synaptic density. This work constitutes the first detailed report on the 3D synaptic organization in the stratum radiatum of the CA1 field of cocaine-SA rats. Our data contribute to the elucidation of the normal and altered synaptic organization of the hippocampus, which is crucial for better understanding the neurobiological mechanisms underlying cocaine addiction.
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Región CA1 Hipocampal/efectos de los fármacos , Región CA1 Hipocampal/ultraestructura , Cocaína/administración & dosificación , Imagenología Tridimensional/métodos , Sinapsis/efectos de los fármacos , Sinapsis/ultraestructura , Animales , Región CA1 Hipocampal/patología , Condicionamiento Operante/efectos de los fármacos , Condicionamiento Operante/fisiología , Inhibidores de Captación de Dopamina/administración & dosificación , Masculino , Microscopía Electrónica de Rastreo/métodos , Plasticidad Neuronal/efectos de los fármacos , Plasticidad Neuronal/fisiología , Ratas , Ratas Endogámicas Lew , Autoadministración/métodos , Sinapsis/patologíaRESUMEN
Maternal separation (MS) causes long-lasting epigenetic changes in the brain and increases vulnerability to traumatic events in adulthood. Of interest, there may be sex-specific differences in these epigenetic changes. In this study, the extent of histone acetylation in the hippocampus (HIP) and the expression of BDNF were measured to determine whether BDNF influences risk of PTSD following MS in early life. Rat offspring were separated from their dams (3 h/day or 6 h/day from PND2~PND14). Then, pups were treated with a single prolonged stress (SPS) procedure when they reached adulthood (PND80). In animals stressed with the SPS procedure in adulthood, those that had increased MS intensity in childhood demonstrated more significant changes in performance on tests of anxiety, depression, and contextual fear memory. Reduced levels of total BDNF mRNA and protein were observed after SPS treatment and further declined in groups with greater MS time in childhood. Interestingly, these changes were correlated with decreased H3K9ac levels and increased HDAC2 levels. Additional MS also led to more severe ultrastructural synaptic damage in rats that experienced the SPS procedure, particularly in the CA1 and CA3 region of the HIP, reflecting impaired synaptic plasticity in these regions. Interestingly, male rats in the MS3h-PTSD group showed decreased anxiety, but no similar changes were found in female rats, suggesting a degree of gender specificity in coping with stress after mild MS. In summary, this study suggests that the epigenetic signatures of the BDNF genes can be linked to HIP responses to stress, providing insights that may be relevant for people at risk of stress-related psychopathologies.
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Factor Neurotrófico Derivado del Encéfalo/metabolismo , Histonas/metabolismo , Privación Materna , Caracteres Sexuales , Trastornos por Estrés Postraumático/metabolismo , Sinapsis/metabolismo , Acetilación , Animales , Conducta Animal , Región CA1 Hipocampal/metabolismo , Región CA1 Hipocampal/ultraestructura , Región CA3 Hipocampal/metabolismo , Región CA3 Hipocampal/ultraestructura , Corticosterona/sangre , Modelos Animales de Enfermedad , Prueba de Laberinto Elevado , Miedo , Femenino , Regulación de la Expresión Génica , Histona Desacetilasa 2/genética , Histona Desacetilasa 2/metabolismo , Inmovilización , Masculino , Prueba de Campo Abierto , Ratas Sprague-Dawley , Análisis de Regresión , Trastornos por Estrés Postraumático/sangre , Trastornos por Estrés Postraumático/complicaciones , Estrés Psicológico/sangre , Estrés Psicológico/complicaciones , Natación , Sinapsis/ultraestructuraRESUMEN
High intracranial pressure (ICP) can impede cerebral blood flow resulting in secondary injury or death following severe stroke. Compensatory mechanisms include reduced cerebral blood and cerebrospinal fluid volumes, but these often fail to prevent raised ICP. Serendipitous observations in intracerebral hemorrhage (ICH) suggest that neurons far removed from a hematoma may shrink as an ICP compliance mechanism. Here, we sought to critically test this observation. We tracked the timing of distal tissue shrinkage (e.g. CA1) after collagenase-induced striatal ICH in rat; cell volume and density alterations (42% volume reduction, 34% density increase; p < 0.0001) were highest day one post-stroke, and rebounded over a week across brain regions. Similar effects were seen in the filament model of middle cerebral artery occlusion (22% volume reduction, 22% density increase; p ≤ 0.007), but not with the Vannucci-Rice model of hypoxic-ischemic encephalopathy (2.5% volume increase, 14% density increase; p ≥ 0.05). Concerningly, this 'tissue compliance' appears to cause sub-lethal damage, as revealed by electron microscopy after ICH. Our data challenge the long-held assumption that 'healthy' brain tissue outside the injured area maintains its volume. Given the magnitude of these effects, we posit that 'tissue compliance' is an important mechanism invoked after severe strokes.
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Hemorragia Cerebral/patología , Accidente Cerebrovascular Hemorrágico/patología , Accidente Cerebrovascular Isquémico/patología , Modelos Biológicos , Animales , Astrocitos/patología , Región CA1 Hipocampal/patología , Región CA1 Hipocampal/ultraestructura , Tamaño de la Célula , Masculino , Neuronas/patología , Ratas Sprague-DawleyRESUMEN
In addition to its role as an auxiliary subunit of A-type voltage-gated K+ channels, we have previously reported that the single transmembrane protein Dipeptidyl Peptidase Like 6 (DPP6) impacts neuronal and synaptic development. DPP6-KO mice are impaired in hippocampal-dependent learning and memory and exhibit smaller brain size. Using immunofluorescence and electron microscopy, we report here a novel structure in hippocampal area CA1 that was significantly more prevalent in aging DPP6-KO mice compared to WT mice of the same age and that these structures were observed earlier in development in DPP6-KO mice. These novel structures appeared as clusters of large puncta that colocalized NeuN, synaptophysin, and chromogranin A. They also partially labeled for MAP2, and with synapsin-1 and VGluT1 labeling on their periphery. Electron microscopy revealed that these structures are abnormal, enlarged presynaptic swellings filled with mainly fibrous material with occasional peripheral, presynaptic active zones forming synapses. Immunofluorescence imaging then showed that a number of markers for aging and especially Alzheimer's disease were found as higher levels in these novel structures in aging DPP6-KO mice compared to WT. Together these results indicate that aging DPP6-KO mice have increased numbers of novel, abnormal presynaptic structures associated with several markers of Alzheimer's disease.
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Envejecimiento/patología , Región CA1 Hipocampal/ultraestructura , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/genética , Terminales Presinápticos/ultraestructura , Enfermedad de Alzheimer , Animales , Cromogranina A/metabolismo , Proteínas de Unión al ADN/metabolismo , Ratones , Ratones Noqueados , Microscopía Electrónica , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Sinapsinas/metabolismo , Sinaptofisina/metabolismo , Proteína 1 de Transporte Vesicular de Glutamato/metabolismoRESUMEN
Most animal species operate according to a 24-h period set by the suprachiasmatic nucleus (SCN) of the hypothalamus. The rhythmic activity of the SCN modulates hippocampal-dependent memory, but the molecular and cellular mechanisms that account for this effect remain largely unknown. Here, we identify cell-type-specific structural and functional changes that occur with circadian rhythmicity in neurons and astrocytes in hippocampal area CA1. Pyramidal neurons change the surface expression of NMDA receptors. Astrocytes change their proximity to synapses. Together, these phenomena alter glutamate clearance, receptor activation, and integration of temporally clustered excitatory synaptic inputs, ultimately shaping hippocampal-dependent learning in vivo. We identify corticosterone as a key contributor to changes in synaptic strength. These findings highlight important mechanisms through which neurons and astrocytes modify the molecular composition and structure of the synaptic environment, contribute to the local storage of information in the hippocampus, and alter the temporal dynamics of cognitive processing.
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Astrocitos/fisiología , Región CA1 Hipocampal/fisiología , Ritmo Circadiano/fisiología , Plasticidad Neuronal/fisiología , Neuronas/fisiología , Sistema de Transporte de Aminoácidos X-AG/metabolismo , Animales , Región CA1 Hipocampal/ultraestructura , Relojes Circadianos/genética , Corticosterona/metabolismo , Oscuridad , Potenciales Postsinápticos Excitadores/fisiología , Regulación de la Expresión Génica , Ácido Glutámico/metabolismo , Memoria/fisiología , Ratones Endogámicos C57BL , Hilos del Neurópilo/metabolismo , Prueba de Campo Abierto , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapsis/fisiología , Factores de Tiempo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico/metabolismoRESUMEN
ATRX gene mutations have been identified in syndromic and non-syndromic intellectual disabilities in humans. ATRX is known to maintain genomic stability in neuroprogenitor cells, but its function in differentiated neurons and memory processes remains largely unresolved. Here, we show that the deletion of neuronal Atrx in mice leads to distinct hippocampal structural defects, fewer presynaptic vesicles, and an enlarged postsynaptic area at CA1 apical dendrite-axon junctions. We identify male-specific impairments in long-term contextual memory and in synaptic gene expression, linked to altered miR-137 levels. We show that ATRX directly binds to the miR-137 locus and that the enrichment of the suppressive histone mark H3K27me3 is significantly reduced upon the loss of ATRX. We conclude that the ablation of ATRX in excitatory forebrain neurons leads to sexually dimorphic effects on miR-137 expression and on spatial memory, identifying a potential therapeutic target for neurological defects caused by ATRX dysfunction.
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Eliminación de Gen , Regulación de la Expresión Génica , Trastornos de la Memoria/genética , Trastornos de la Memoria/fisiopatología , MicroARNs/genética , Caracteres Sexuales , Aprendizaje Espacial , Proteína Nuclear Ligada al Cromosoma X/deficiencia , Animales , Secuencia de Bases , Región CA1 Hipocampal/patología , Región CA1 Hipocampal/ultraestructura , Condicionamiento Operante , Dendritas/metabolismo , Dendritas/ultraestructura , Femenino , Genotipo , Histonas/metabolismo , Lisina/metabolismo , Imagen por Resonancia Magnética , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , MicroARNs/metabolismo , Neuronas , Especificidad de Órganos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Sinapsis/metabolismo , Sinapsis/ultraestructura , Proteína Nuclear Ligada al Cromosoma X/metabolismoRESUMEN
The hippocampal CA1 field integrates a wide variety of subcortical and cortical inputs, but its synaptic organization in humans is still unknown due to the difficulties involved studying the human brain via electron microscope techniques. However, we have shown that the 3D reconstruction method using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) can be applied to study in detail the synaptic organization of the human brain obtained from autopsies, yielding excellent results. Using this technology, 24,752 synapses were fully reconstructed in CA1, revealing that most of them were excitatory, targeting dendritic spines and displaying a macular shape, regardless of the layer examined. However, remarkable differences were observed between layers. These data constitute the first extensive description of the synaptic organization of the neuropil of the human CA1 region.
There are billions of nerve cells or neurons in the human brain, and each one can form thousands of connections, also called synapses, with other neurons. That means there are trillions of synapses in the brain that keep information flowing. Studying the arrangement of individual neurons in the human brain, and the connections between them, is incredibly difficult because of its complexity. Scientists have tools that can image the whole brain and can measure the activity in different regions, but these tools only visualize brain structures that are large enough to be seen with human eyes. Synapses are much smaller (in the range of nanometers), and can only be seen using thin slices of preserved brain tissue through a technique called electron microscopy. The hippocampus is a part of the human brain that is critical for memory, learning and spatial orientation, and is affected in epilepsy and Alzheimer's disease. Although numerous studies of the hippocampus have been performed in laboratory animals, such as mice, the question remains as to how much of the information gained from these studies applies to humans. Thus, studying the human brain directly is a major goal in neuroscience. However, the scarcity of human brain tissue suitable for the study of synapses is one of the most important issues to overcome. Fortunately, healthy human brain tissue that can be studied using electron microscopy is sometimes donated after death. Using these donations could improve the understanding of the synapses in normal brains and possible changes associated with disease. Now, Montero-Crespo et al. have mapped synapses in the normal human hippocampus in three dimensions providing the first detailed description of synaptic structure in this part of the brain. Using high-powered electron microscopes and donated brain tissue samples collected after death, Montero-Crespo et al. imaged almost 25,000 connections between neurons. The analysis showed that synapses were more densely packed in some layers of the hippocampus than in others. Most synapses were found to be connected to tiny dendritic 'spines' that sprout from dendritic branches of the neuron, and they activated (not suppressed) the next neuron. Beyond its implications for better understanding of brain health and disease, this work could also advance computer modelling attempts to mimic the structure of the brain and its activity.
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Región CA1 Hipocampal/citología , Región CA1 Hipocampal/ultraestructura , Microscopía Electrónica de Rastreo/métodos , Adulto , Anciano , Anciano de 80 o más Años , Autopsia , Cadáver , Femenino , Humanos , Masculino , Persona de Mediana Edad , Conformación MolecularRESUMEN
The deposition of beta-amyloid (Aß) in the brain is detected in Alzheimer's disease and during ageing. Until now, ultrastructural studies of changes caused by Aß in the dentate gyrus are very scarce. The effects of Aß 1-42 injection into the CA1 field of rat hippocampus were studied by electron microscopy. In 2 weeks after injection of aggregated Aß in low concentrations, destructive changes were seen in the structure of dentate gyrus cells, which consisted in a decrease in the number of dentate gyrus neurons and axo-dendritic synapses. These changes were accompanied by enlargement of the endoplasmic reticulum cisterns and widening of the active zones of synapses. Thus, injection of aggregated Aß 1-42 into the hippocampus led to irreversible (a decrease in the number of neurons and axo-dendritic synapses, agglutination of synthetic vesicles) and adaptive changes (an increase in the sizes of endoplasmic reticulum cisterns and active zones of synapses) in dentate gyrus neurons aimed at the maintenance of functional activity of the nervous system.
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Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/administración & dosificación , Región CA1 Hipocampal/ultraestructura , Giro Dentado/ultraestructura , Neuronas/ultraestructura , Fragmentos de Péptidos/administración & dosificación , Sinapsis/ultraestructura , Enfermedad de Alzheimer/inducido químicamente , Péptidos beta-Amiloides/química , Animales , Región CA1 Hipocampal/efectos de los fármacos , Región CA1 Hipocampal/patología , Gránulos Citoplasmáticos/efectos de los fármacos , Gránulos Citoplasmáticos/patología , Gránulos Citoplasmáticos/ultraestructura , Giro Dentado/efectos de los fármacos , Giro Dentado/patología , Modelos Animales de Enfermedad , Retículo Endoplásmico/efectos de los fármacos , Retículo Endoplásmico/patología , Retículo Endoplásmico/ultraestructura , Inyecciones Intraventriculares , Lipofuscina/química , Masculino , Microscopía Electrónica , Neuronas/efectos de los fármacos , Neuronas/patología , Fragmentos de Péptidos/química , Agregado de Proteínas , Ratas , Ratas Wistar , Sinapsis/efectos de los fármacos , Sinapsis/patologíaRESUMEN
BACKGROUND: Electroconvulsive therapy (ECT) is a highly effective and fast-acting treatment for depression used in the clinic. Its mechanism of therapeutic action remains uncertain. Previous studies have focused on documenting neuroplasticity in the early phase following electroconvulsive seizures (ECS), an animal model of ECT. Here, we investigate whether changes in synaptic plasticity and nonneuronal plasticity (vascular and mitochondria) are sustained 3 months after repeated ECS trials. METHODS: ECS or sham treatment was given daily for 1 day or 10 days to a genetic animal model of depression: the Flinders Sensitive and Resistant Line rats. Stereological principles were employed to quantify numbers of synapses and mitochondria as well as length of microvessels in the hippocampus 24 hours after a single ECS. Three months after 10 ECS treatments (1 per day for 10 days) and sham-treatment, brain-derived neurotrophic factor and vascular endothelial growth factor protein levels were quantified with immunohistochemistry. RESULTS: A single ECS treatment significantly increased the volume of hippocampal CA1-stratum radiatum, the total length of microvessels, mitochondria number, and synapse number. Observed changes were sustained as shown in the multiple ECS treatment group analyzed 3 months after the last of 10 ECS treatments. CONCLUSION: A single ECS caused rapid effects of synaptic plasticity and nonneuronal plasticity, while repeated ECS induced long-lasting changes in the efficacy of synaptic plasticity and nonneuronal plasticity at least up to 3 months after ECS.
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Electrochoque/efectos adversos , Hipocampo/ultraestructura , Animales , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Región CA1 Hipocampal/ultraestructura , Capilares/ultraestructura , Depresión/genética , Depresión/psicología , Depresión/terapia , Inmunohistoquímica , Masculino , Mitocondrias/ultraestructura , Plasticidad Neuronal , Ratas , Sinapsis/ultraestructura , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
Short chain fatty acids, produced as gut microbiome metabolites but also present in the diet, exert broad effects in host physiology. Propionic acid (PPA), along with butyrate and acetate, plays a growing role in health, but also in neurological conditions. Increased PPA exposure in humans, animal models and cell lines elicit diverse behavioural and biochemical changes consistent with organic acidurias, mitochondrial disorders and autism spectrum disorders (ASD). ASD is considered a disorder of synaptic dysfunction and cell signalling, but also neuroinflammatory and neurometabolic components. We examined behaviour (Morris water and radial arm mazes) and the ultrastructure of the hippocampus and medial prefrontal cortex (electron microscopy) following a single intraperitoneal (i.p.) injection of PPA (175 mg/kg) in male adolescent rats. PPA treatment showed altered social and locomotor behaviour without changes in learning and memory. Both transient and enduring ultrastructural alterations in synapses, astro- and microglia were detected in the CA1 hippocampal area. Electron microscopic analysis showed the PPA treatment significantly decreased the total number of synaptic vesicles, presynaptic mitochondria and synapses with a symmetric active zone. Thus, brief systemic administration of this dietary and enteric short chain fatty acid produced behavioural and dynamic brain ultrastructural changes, providing further validation of the PPA model of ASD.
Asunto(s)
Trastorno Autístico/inducido químicamente , Trastorno Autístico/psicología , Conducta Animal/efectos de los fármacos , Encéfalo/patología , Propionatos/toxicidad , Animales , Trastorno Autístico/patología , Encéfalo/ultraestructura , Región CA1 Hipocampal/patología , Región CA1 Hipocampal/ultraestructura , Modelos Animales de Enfermedad , Hipocampo/patología , Hipocampo/ultraestructura , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Actividad Motora/efectos de los fármacos , Corteza Prefrontal/patología , Corteza Prefrontal/ultraestructura , Ratas , Ratas Wistar , Conducta SocialRESUMEN
The present study aimed at exploring a potentially neuroprotective effect of topiramate (TPM), one of the most commonly used newer-generation, broad-spectrum, antiepileptic drugs against ultrastructural damage of hippocampal synaptic endings in the experimental model of febrile seizures (FS). The study used male young Wistar rats aged 22-30 days, divided into three experimental groups and the control group. Brain maturity in such animals corresponds to that of 1- or 2-year-old children. Hyperthermic stress was evoked by placing animals in a 45°C water bath for four consecutive days. TPM at a dose of 80 mg/kg b.m. was administered with an intragastric tube before and immediately after FS. Specimens (1 mm3) collected from the hippocampal CA1 and CA3 sectors, fixed via transcardial perfusion with a solution of paraformaldehyde and glutaraldehyde, were routinely processed for transmission-electron microscopic analysis. Advanced ultrastructural changes induced by hyperthermic stress were manifested by distinct swelling of hippocampal pre- and post-synaptic axodendritic and axospinal endings, including their vacuolization and disintegration. The axoplasm of the presynaptic boutons contained a markedly decreased number of synaptic vesicles and their abnormal accumulation in the active synaptic region. The synaptic junctions showed a dilated synaptic cleft and a decreased synaptic active zone. TPM used directly after FS was ineffective in the prevention of hyperthermia-induced injury of synaptic endings in hippocampal CA1 and CA3 sectors. However, "prophylactic" administration of TPM, prior to FS induction, demonstrated a neuroprotective effect against synaptic damage in approximately 25% of the synaptic endings in the hippocampal sectors, more frequently located in perivascular zones. It was manifested by smaller oedema of both presynaptic and postsynaptic parts, containing well-preserved mitochondria, increased number and regular distribution of synaptic vesicles within the axoplasm, and increased synaptic active zone. Our current and previous findings suggest that TPM administered "prophylactically", before FS, could exert a favourable effect on some synapses, indirectly, via the vascular factor, i.e. protecting blood-brain barrier components and through better blood supply of the hippocampal CA1 and CA3 sectors, which may have practical implications.
Asunto(s)
Anticonvulsivantes/farmacología , Región CA1 Hipocampal/efectos de los fármacos , Región CA3 Hipocampal/efectos de los fármacos , Terminales Presinápticos/efectos de los fármacos , Convulsiones Febriles/patología , Topiramato/farmacología , Animales , Región CA1 Hipocampal/ultraestructura , Región CA3 Hipocampal/ultraestructura , Modelos Animales de Enfermedad , Masculino , Microscopía Electrónica de Transmisión , Fármacos Neuroprotectores/farmacología , Terminales Presinápticos/ultraestructura , Ratas , Ratas WistarRESUMEN
Simultaneous imaging and manipulation of a genetically defined neuronal population can provide a causal link between its activity and function. Here, we designed a miniaturized microscope (or 'miniscope') that allows fluorescence imaging and optogenetic manipulation at the cellular level in freely behaving animals. This miniscope has an integrated optical connector that accepts any combination of external light sources, allowing flexibility in the choice of sensors and manipulators. Moreover, due to its simple structure and use of open source software, the miniscope is easy to build and modify. Using this miniscope, we demonstrate the optogenetic silencing of hippocampal CA1 neurons using two laser light sources-one stimulating a calcium sensor (i.e., jGCaAMP7c) and the other serving as an optogenetic silencer (i.e., Jaws). This new miniscope can contribute to efforts to determine causal relationships between neuronal network dynamics and animal behavior.
Asunto(s)
Región CA1 Hipocampal/metabolismo , Microscopía/instrumentación , Red Nerviosa/metabolismo , Neuroimagen/métodos , Neuronas/metabolismo , Optogenética/métodos , Animales , Conducta Animal/fisiología , Región CA1 Hipocampal/ultraestructura , Calcio/metabolismo , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Dependovirus/genética , Dependovirus/metabolismo , Expresión Génica , Genes Reporteros , Vectores Genéticos/química , Vectores Genéticos/metabolismo , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Inyecciones Intraventriculares , Luz , Ratones , Microscopía/métodos , Red Nerviosa/ultraestructura , Neuroimagen/instrumentación , Neuronas/ultraestructura , Imagen Óptica/instrumentación , Imagen Óptica/métodos , Optogenética/instrumentación , Rodopsina/genética , Rodopsina/metabolismoRESUMEN
How do neurons encode long-term memories? Bilateral imaging of neuronal activity in the mouse hippocampus reveals that, from one day to the next, ~40% of neurons change their responsiveness to cues, but thereafter only 1% of cells change per day. Despite these changes, neuronal responses are resilient to a lack of exposure to a previously completed task or to hippocampus lesions. Unlike individual neurons, the responses of which change after a few days, groups of neurons with inter- and intrahemispheric synchronous activity show stable responses for several weeks. The likelihood that a neuron maintains its responsiveness across days is proportional to the number of neurons with which its activity is synchronous. Information stored in individual neurons is relatively labile, but it can be reliably stored in networks of synchronously active neurons.
Asunto(s)
Región CA1 Hipocampal/lesiones , Región CA1 Hipocampal/fisiología , Memoria a Largo Plazo/fisiología , Recuerdo Mental/fisiología , Células Piramidales/fisiología , Animales , Región CA1 Hipocampal/ultraestructura , Señales (Psicología) , Ratones , Ratones Transgénicos , Neuroimagen , Células Piramidales/ultraestructura , Factores de TiempoRESUMEN
Status epilepticus without prompt seizure control always leads to neuronal death and long-term cognitive deficits, but effective intervention is still absent. Here, we found that hydrogen could alleviate the hippocampus-dependent spatial learning and memory deficit in lithium-pilocarpine model of status epilepticus in rats, as evidenced by the results in Morris water maze test. Hydrogen treatment downregulated the expression of necroptosis-related proteins, such as MLKL, phosphorylated-MLKL, and RIPK3 in hippocampus, and further protected neurons and astrocytes from necroptosis which was here first verified to occur in status epilepticus. Hydrogen also protected cells from apoptosis, which was indicated by the decreased cleaved-Caspase 3 expression. Meanwhile, Iba1+ microglial activation by status epilepticus was reduced by hydrogen treatment. These findings confirm the utility of hydrogen treatment in averting cell death including necroptosis and alleviating cognitive deficits caused by status epilepticus. Therefore, hydrogen may provide a potential and powerful clinical treatment for status epilepticus-related cognitive deficits.
Asunto(s)
Apoptosis/efectos de los fármacos , Trastornos del Conocimiento/tratamiento farmacológico , Trastornos del Conocimiento/patología , Hidrógeno/uso terapéutico , Estado Epiléptico/inducido químicamente , Estado Epiléptico/tratamiento farmacológico , Animales , Región CA1 Hipocampal/efectos de los fármacos , Región CA1 Hipocampal/patología , Región CA1 Hipocampal/ultraestructura , Trastornos del Conocimiento/complicaciones , Trastornos del Conocimiento/fisiopatología , Modelos Animales de Enfermedad , Hidrógeno/farmacología , Inflamación/patología , Litio , Masculino , Memoria/efectos de los fármacos , Necrosis , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Neuronas/patología , Fármacos Neuroprotectores/farmacología , Fármacos Neuroprotectores/uso terapéutico , Pilocarpina , Ratas Sprague-Dawley , Aprendizaje Espacial/efectos de los fármacos , Estado Epiléptico/complicaciones , Estado Epiléptico/patologíaRESUMEN
Activity can induce structural changes in glutamatergic excitatory synapses, including increase in thickness and curvature of the postsynaptic density (PSD); these structural changes can only be documented by electron microscopy. Here in organotypic hippocampal slice cultures where experimental conditions can be easily manipulated, increases in thickness and curvature of PSDs were noticeable within 30 s of stimulation and progressed with time up to 3 min. These structural changes were reversible upon returning the samples to control medium for 5-10 min. Thus, the postsynaptic density is a very dynamic structure that undergoes rapid reorganization of its components upon stimulation, and recovery upon cessation of stimulation. The gradual increase in thickness of PSD could result from a gradual translocation of some PSD proteins to the PSD, and the increase in curvature of the PSD is likely led by postsynaptic elements.