RESUMEN
Mild traumatic brain injuries can have long-term consequences that interfere with the life of the patient and impose a burden on our health care system. Oxidative stress has been identified as a contributing factor for the progression of neurodegeneration following TBI. A major source of oxidative stress for many veterans is cigarette smoking and second-hand smoke, which has been shown to have an effect on TBI recovery. To examine the potential influences of second-hand smoke during recovery from TBI, we utilized a mouse model of closed head injury, followed by repeated exposure to cigarette smoke and treatment with a neuroprotective antioxidant. We found that neither the mild injuries nor the smoke exposure produced axonal damage detectable with amino cupric silver staining. However, complexity in the dendritic arbors was significantly reduced after mild TBI plus smoke exposure. In the hippocampus, there were astrocytic responses, including Cyp2e1 upregulation, after the injury and tobacco smoke insult. This study provides useful context for the importance of lifestyle changes, such as reducing or eliminating cigarette smoking, during recovery from TBI.
Asunto(s)
Conmoción Encefálica , Lesiones Traumáticas del Encéfalo , Contaminación por Humo de Tabaco , Animales , Astrocitos , Hipocampo , Humanos , RatonesRESUMEN
Traumatic brain injury (TBI) has been designated as a signature injury of modern military conflicts. Blast trauma, in particular, has come to make up a significant portion of the TBIs which are sustained in warzones. Though most TBIs are mild, even mild TBI can induce long term effects, including cognitive and memory deficits. In our study, we utilized a mouse model of mild blast-related TBI (bTBI) to investigate TBI-induced changes within the cortex and hippocampus. We performed rapid Golgi staining on the layer IV and V pyramidal neurons of the parietal cortex and the CA1 basilar tree of the hippocampus and quantified dendritic branching and distribution. We found decreased dendritic branching within both the cortex and hippocampus in injured mice. Within parietal cortex, this decreased branching was most evident within the middle region, while outer and inner regions resembled that of control mice. This study provides important knowledge in the study of how the shockwave associated with a blast explosion impacts different brain regions.
Asunto(s)
Traumatismos por Explosión/patología , Conmoción Encefálica/patología , Región CA1 Hipocampal/patología , Dendritas/patología , Lóbulo Parietal/patología , Animales , Conflictos Armados , Traumatismos por Explosión/etiología , Conmoción Encefálica/etiología , Región CA1 Hipocampal/citología , Modelos Animales de Enfermedad , Explosiones , Aparato de Golgi/patología , Humanos , Masculino , Ratones , Lóbulo Parietal/citología , Células Piramidales/citología , Células Piramidales/patologíaRESUMEN
BACKGROUND: Traumatic brain injury (TBI) is a widespread public health problem and a signature injury of our military in modern conflicts. Despite the long-term effects of even mild brain injuries, an effective treatment remains elusive. Coffee and several of its compounds, including caffeine, have been identified as having neuroprotective effects in studies of neurodegenerative disease. Given the molecular similarities between TBI and neurodegenerative disease, we have devised a study to test a nanocoffee extract in the treatment of a mouse model of mild TBI. RESULTS: After a single injury and two subsequent injections of nanocoffee, we identified treatment as being associated with improved behavioral outcomes, favorable molecular signaling changes, and dendritic changes suggestive of improved neuronal health. CONCLUSIONS: We have identified coffee extracts as a potential viable multifaceted treatment approach to target the secondary injury associated with TBI.
Asunto(s)
Conmoción Encefálica/prevención & control , Coffea/química , Aprendizaje por Laberinto/efectos de los fármacos , Extractos Vegetales/farmacología , Proteínas/metabolismo , Reconocimiento en Psicología/efectos de los fármacos , Animales , Conmoción Encefálica/patología , Conmoción Encefálica/psicología , Corteza Cerebral/metabolismo , Dendritas/patología , Hipocampo/metabolismo , Masculino , Ratones , Nanopartículas/química , Fármacos Neuroprotectores/farmacología , Extractos Vegetales/química , Sonicación , Agua/químicaRESUMEN
Traumatic brain injury (TBI) continues to be a signature injury of our modern conflicts. Due in part to increased use of improvised explosive devices (IEDs), we have seen blast trauma make up a significant portion of TBIs sustained by deployed troops and civilians. In addition to the physical injury, TBI is also a common comorbidity with post-traumatic stress disorder (PTSD). Previous research suggests that PTSD is often associated with increased signaling within the amygdala, leading to feelings of fear and hyperarousal. In our study, we utilized a mouse model of mild blast-related TBI (bTBI) to investigate how TBI induces changes within the amygdala, which may provide favorable conditions for the development of PTSD. To do this, we performed Golgi staining on the stellate neurons of the basolateral amygdala and quantified dendritic amount, distribution, and complexity. We found increases in dendritic branching and in the density of dendritic spines in injured mice. Increases in spine density appears to be primarily due to increases in memory associated mushroom type dendritic spines. These changes observed in our bTBI model that are consistent with chronic stress models, suggesting an important connection between the physical changes induced by TBI and the neurological symptoms of PTSD.
Asunto(s)
Amígdala del Cerebelo/patología , Traumatismos por Explosión/patología , Conmoción Encefálica/patología , Red Nerviosa/patología , Animales , Traumatismos por Explosión/psicología , Conmoción Encefálica/psicología , Tamaño de la Célula , Dendritas/patología , Dendritas/ultraestructura , Espinas Dendríticas/patología , Espinas Dendríticas/ultraestructura , Modelos Animales de Enfermedad , Masculino , Ratones , Ratones Endogámicos ICR , Trastornos por Estrés Postraumático/etiología , Trastornos por Estrés Postraumático/psicologíaRESUMEN
Worldwide head injuries are a growing problem. In the United States alone, 1.7 million people suffer a head injury each year. While most of these injuries are mild, head injury sufferers still sustain symptoms that can have major medical and economical impacts. Moreover, repetitive mild head injuries, like those observed in active military personnel and athletes, have demonstrated a more severe and long-term set of consequences. In an effort to better understand the delayed pathological changes following multiple mild head injuries, we used a mouse model of mild closed head injury (with no motor deficits observed by rotarod testing) and measured dendritic complexity at 30 days after injury and potentially related factors up to 60 days post-injury. We found an increase in TDP-43 protein at 60 days post-injury in the hippocampus and a decrease in autophagy factors three days post-injury. Alterations in dendritic complexity were neuronal subtype and location specific. Measurements of neurotropic factors suggest that an increase in complexity in the cortex may be a consequence of neuronal loss of the less connected neurons.
Asunto(s)
Conmoción Encefálica/metabolismo , Conmoción Encefálica/patología , Proteínas de Unión al ADN/biosíntesis , Dendritas/patología , Animales , Autofagia/fisiología , Modelos Animales de Enfermedad , Masculino , Ratones , Biosíntesis de Proteínas/fisiologíaRESUMEN
UNLABELLED: Arginase 1 deficiency is a urea cycle disorder associated with hyperargininemia, spastic diplegia, loss of ambulation, intellectual disability, and seizures. To gain insight on how loss of arginase expression affects the excitability and synaptic connectivity of the cortical neurons in the developing brain, we used anatomical, ultrastructural, and electrophysiological techniques to determine how single-copy and double-copy arginase deletion affects cortical circuits in mice. We find that the loss of arginase 1 expression results in decreased dendritic complexity, decreased excitatory and inhibitory synapse numbers, decreased intrinsic excitability, and altered synaptic transmission in layer 5 motor cortical neurons. Hepatic arginase 1 gene therapy using adeno-associated virus rescued nearly all these abnormalities when administered to neonatal homozygous knock-out animals. Therefore, gene therapeutic strategies can reverse physiological and anatomical markers of arginase 1 deficiency and therefore may be of therapeutic benefit for the neurological disabilities in this syndrome. SIGNIFICANCE STATEMENT: These studies are one of the few investigations to try to understand the underlying neurological dysfunction that occurs in urea cycle disorders and the only to examine arginase deficiency. We have demonstrated by multiple modalities that, in murine layer 5 cortical neurons, a gradation of abnormalities exists based on the functional copy number of arginase: intrinsic excitability is altered, there is decreased density in asymmetrical and perisomatic synapses, and analysis of the dendritic complexity is lowest in the homozygous knock-out. With neonatal administration of adeno-associated virus expressing arginase, there is near-total recovery of the abnormalities in neurons and cortical circuits, supporting the concept that neonatal gene therapy may prevent the functional abnormalities that occur in arginase deficiency.
Asunto(s)
Arginasa/uso terapéutico , Terapia Genética , Hiperargininemia/patología , Hiperargininemia/terapia , Corteza Motora/fisiología , Recuperación de la Función/fisiología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Amoníaco/sangre , Animales , Animales Recién Nacidos , Arginasa/genética , Arginasa/metabolismo , Modelos Animales de Enfermedad , Hiperargininemia/sangre , Técnicas In Vitro , Ratones , Ratones Transgénicos , Corteza Motora/citología , Corteza Motora/ultraestructura , Red Nerviosa/patología , Red Nerviosa/fisiología , Red Nerviosa/ultraestructura , Neuronas/fisiología , Neuronas/ultraestructura , Picrotoxina/farmacología , Bloqueadores de los Canales de Sodio/farmacología , Sinapsis/ultraestructura , Tetrodotoxina/farmacologíaRESUMEN
We previously demonstrated that rats that receive dorsal third ventricle (3V) streptozotocin (STZ) injections (STZ-3V-rats) exhibit cognitive decline as measured by the Morris Water Maze (MWM) and can be used as an animal model of Alzheimer's disease (AD). Immunohistochemical studies of the hippocampal formations of these animals have revealed significant changes in cerebral insulin signalling pathways, as well as marked increases of amyloid beta (Ab) deposition. Here, we performed Sholl analyses of granule cell layer dendrites and measured dendrite spine densities to assess the effect of STZ on hippocampal morphology. In STZ-3V rats as the results, more branching, complex dendrite arborisation, and increased soma size of the granule cells were observed, while spine densities were decreased in all three spine types. An intraventricular injection of a long-acting insulin analogue improved STZ-induced behavioural and immunohistochemical changes. Nevertheless, dendrite spine densities remained diminished, presumably due to overall null changes since new spine formation due to insulin stimulation has been compensated by loss of old spines. It is concluded that cognitive decline in the "Brain Diabetes" rats is primarily due to impaired intracerebral insulin signalling and the ultimate results were injured excitatory inputs through the perforant pathway.
Asunto(s)
Dendritas/patología , Diabetes Mellitus Experimental/patología , Hipocampo/patología , Animales , Tamaño de la Célula/efectos de los fármacos , Dendritas/efectos de los fármacos , Dendritas/fisiología , Diabetes Mellitus Experimental/tratamiento farmacológico , Diabetes Mellitus Experimental/fisiopatología , Modelos Animales de Enfermedad , Hipocampo/efectos de los fármacos , Hipocampo/fisiopatología , Inmunohistoquímica , Inyecciones Intraventriculares , Masculino , Neuronas/efectos de los fármacos , Neuronas/patología , Neuronas/fisiología , Ratas Wistar , EstreptozocinaRESUMEN
A large body of evidence from molecular, cellular and human studies suggests that lithium may enhance synaptic plasticity, which may be associated with its therapeutic efficacy. However, only a small number of studies have directly assessed this. To determine whether lithium treatment alters structural synaptic plasticity, this study examined the effect of 4 wk lithium treatment on the amount and distribution of dendrites in the dentate gyrus (DG) and hippocampal area CA1 of young adult rats. Following 4 wk lithium or control chow feeding, animals were decapitated, the hippocampi were prepared and stained using a rapid Golgi staining technique and the amount and distribution of the dendritic branching was evaluated using Sholl analyses (method of concentric circles). In the DG, lithium treatment increased the amount and distribution of dendritic branches in the proximal half of dendritic trees of the granule cells and reduced branching in the distal half. In area CA1, the same treatment also increased the number of dendritic branches in the proximal half of apical dendritic trees of CA1 pyramidal cells and reduced branching in the distal half of apical dendritic trees but had no effect on basilar dendritic trees. The lithium treatment altered the total density of dendritic trees in neither the DG nor area CA1. These findings suggest that, in the DG and apical CA1, chronic lithium treatment rearranges neuronal morphology to increase dendritic branching and distribution to where major afferent input is received.
Asunto(s)
Antimaníacos/farmacología , Dendritas/efectos de los fármacos , Hipocampo/citología , Litio/farmacología , Neuronas/ultraestructura , Animales , Espinas Dendríticas/efectos de los fármacos , Masculino , Neuronas/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Tinción con Nitrato de Plata , Estadísticas no Paramétricas , Factores de TiempoRESUMEN
We investigated the neurobiological bases of variation in response to predator stress (PS). Sixteen days after treatment (PS or handling), rats were grouped according to anxiety in the elevated plus maze (EPM). Acoustic startle was also measured. We examined the structure of dendritic trees of basolateral amygdala (BLA) output neurons (stellate and pyramidal cells) and of dorsal hippocampal (DHC) dentate granule cells of less anxious (LA) and more (extremely) anxious (MA) stressed animals (PSLA and PSMA). Handled controls (HC) which were less anxious (HCLA) and spontaneously more anxious (HCMA) equivalently to predator stressed subgroups were also studied. Golgi analysis revealed BLA output neurons of HCMA rats exhibited longer, more branched dendrites with higher spine density than the other groups of rats, which did not differ. Finally, spine density of DHC granule cells was equally depressed in HCMA and PSMA rats relative to HCLA and PSLA rats. Total dendritic length of BLA pyramidal and stellate cells (positive predictor) and DHC spine density (negative predictor) together accounted for 96% of the variance of anxiety of handled rats. DHC spine density was a negative predictor of PSMA and PSLA anxiety, accounting for 70% of the variance. Data are discussed in the context of morphological differences as phenotypic markers of a genetic predisposition to anxiety in handled controls, and a possible genetic vulnerability to predator stress expressed as reduced spine density in the DHC. Significance of findings for animal models of anxiety and hyperarousal comorbidities of PTSD are discussed.
Asunto(s)
Amígdala del Cerebelo/citología , Ansiedad/fisiopatología , Dendritas/fisiología , Manejo Psicológico , Hipocampo/citología , Neuronas/citología , Amígdala del Cerebelo/fisiopatología , Animales , Conducta Animal/fisiología , Forma de la Célula/fisiología , Hipocampo/fisiopatología , Masculino , Neuronas/fisiología , Ratas , Ratas Long-Evans , Estrés Psicológico/fisiopatologíaRESUMEN
Conservation of normal cognitive functions relies on the proper performance of the nervous system at the cellular and molecular level. The mammalian nicotinamide-adenine dinucleotide-dependent deacetylase SIRT1 impacts different processes potentially involved in the maintenance of brain integrity, such as chromatin remodeling, DNA repair, cell survival, and neurogenesis. Here we show that SIRT1 is expressed in neurons of the hippocampus, a key structure in learning and memory. Using a combination of behavioral and electrophysiological paradigms, we analyzed the effects of SIRT1 deficiency and overexpression on mouse learning and memory as well as on synaptic plasticity. We demonstrated that the absence of SIRT1 impaired cognitive abilities, including immediate memory, classical conditioning, and spatial learning. In addition, we found that the cognitive deficits in SIRT1 knock-out (KO) mice were associated with defects in synaptic plasticity without alterations in basal synaptic transmission or NMDA receptor function. Brains of SIRT1-KO mice exhibited normal morphology and dendritic spine structure but displayed a decrease in dendritic branching, branch length, and complexity of neuronal dendritic arbors. Also, a decrease in extracellular signal-regulated kinase 1/2 phosphorylation and altered expression of hippocampal genes involved in synaptic function, lipid metabolism, and myelination were detected in SIRT1-KO mice. In contrast, mice with high levels of SIRT1 expression in brain exhibited regular synaptic plasticity and memory. We conclude that SIRT1 is indispensable for normal learning, memory, and synaptic plasticity in mice.
Asunto(s)
Cognición/fisiología , Hipocampo/fisiología , Aprendizaje/fisiología , Potenciación a Largo Plazo/genética , Memoria/fisiología , Neuronas/metabolismo , Sirtuina 1/genética , Animales , Espinas Dendríticas/ultraestructura , Regulación de la Expresión Génica , Hipocampo/citología , Ratones , Ratones Noqueados , Neuronas/química , Técnicas de Placa-Clamp , Sirtuina 1/análisis , Distribución TisularRESUMEN
BACKGROUND: Neurodevelopmental disorders are associated with altered patterns of neuronal connectivity. A critical determinant of neuronal connectivity is the dendritic morphology of individual neurons, which is shaped by experience. The identification of environmental exposures that interfere with dendritic growth and plasticity may, therefore, provide insight into environmental risk factors for neurodevelopmental disorders. OBJECTIVE: We tested the hypothesis that polychlorinated biphenyls (PCBs) alter dendritic growth and/or plasticity by promoting the activity of ryanodine receptors (RyRs). METHODS AND RESULTS: The Morris water maze was used to induce experience-dependent neural plasticity in weanling rats exposed to either vehicle or Aroclor 1254 (A1254) in the maternal diet throughout gestation and lactation. Developmental A1254 exposure promoted dendritic growth in cerebellar Purkinje cells and neocortical pyramidal neurons among untrained animals but attenuated or reversed experience-dependent dendritic growth among maze-trained littermates. These structural changes coincided with subtle deficits in spatial learning and memory, increased [3H]-ryanodine binding sites and RyR expression in the cerebellum of untrained animals, and inhibition of training-induced RyR upregulation. A congener with potent RyR activity, PCB95, but not a congener with negligible RyR activity, PCB66, promoted dendritic growth in primary cortical neuron cultures and this effect was blocked by pharmacologic antagonism of RyR activity. CONCLUSIONS: Developmental exposure to PCBs interferes with normal patterns of dendritic growth and plasticity, and these effects may be linked to changes in RyR expression and function. These findings identify PCBs as candidate environmental risk factors for neurodevelopmental disorders, especially in children with heritable deficits in calcium signaling.
Asunto(s)
/toxicidad , Dendritas/efectos de los fármacos , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Plasticidad Neuronal/efectos de los fármacos , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Animales , Animales Recién Nacidos , Peso Corporal , Femenino , Proteínas Fluorescentes Verdes , Tamaño de la Camada , Aprendizaje por Laberinto/efectos de los fármacos , Memoria/efectos de los fármacos , Proteínas Asociadas a Microtúbulos , Embarazo , Efectos Tardíos de la Exposición Prenatal , Ratas , Ratas Sprague-Dawley , Razón de MasculinidadRESUMEN
BACKGROUND/OBJECTIVE: We previously reported that chronic hyperglycemia, but not hypoglycemia, was associated with the reduction of neuronal size in the rat brain. We hypothesized that hyperglycemia-induced changes in neuronal structure would have negative consequences, such as impaired learning and memory. We therefore assessed the effects of hyperglycemia and hypoglycemia on neuronal dendritic structure and cognitive functioning in young rats. DESIGN/METHODS: Experimental manipulations were conducted on male Wistar rats for 8 wk, beginning at 4 wk of age. At the completion of the treatments, all rats were trained in the radial-arm water maze, a spatial (hippocampus-dependent) learning and memory task. Three groups of rats were tested: an untreated control group, a streptozotocin-induced diabetic (STZ-D) group, and an intermittent hypoglycemic group. Following behavioral training, the brains of all animals were examined with histologic and biochemical measurements. RESULTS: Peripheral hyperglycemia was associated with significant increases in brain sorbitol (7.5 +/- 1.6 vs. 5.84 +/- 1.0 microM/mg) and inositol (9.6 +/- 1.4 vs. 7.1 +/- 1.1 microM/mg) and reduced taurine (0.65 +/- 0.1 vs. 1.3 +/- 0.1 mg/mg). Histologic evaluation revealed neurons with reduced dendritic branching and spine density in STZ-D rats but not in control or hypoglycemic animals. In addition, the STZ-D group exhibited impaired performance on the water maze memory test. CONCLUSIONS: Hyperglycemia, but not hypoglycemia, was associated with adverse effects on the brain polyol pathway activity, neuronal structural changes, and impaired long-term spatial memory. This finding suggests that the hyperglycemic component of diabetes mellitus has a greater adverse effect on brain functioning than does intermittent hypoglycemia.
Asunto(s)
Dendritas/patología , Diabetes Mellitus Experimental/fisiopatología , Hiperglucemia/complicaciones , Trastornos de la Memoria/etiología , Neuronas/patología , Animales , Química Encefálica/fisiología , Corteza Cerebral/metabolismo , Espinas Dendríticas/patología , Espinas Dendríticas/fisiología , Hipocampo/metabolismo , Hiperglucemia/fisiopatología , Hipoglucemia/complicaciones , Hipoglucemia/fisiopatología , Inositol/metabolismo , Aprendizaje por Laberinto/fisiología , Memoria/fisiología , Ratas , Ratas Wistar , Sorbitol/metabolismo , Conducta Espacial/fisiología , Taurina/metabolismoRESUMEN
While methamphetamine-induced changes in brain neurotransmitters, their receptors, and transporters are well studied, the means by which methamphetamine abuse results in cognitive and behavioral abnormalities is unknown. Here, we administered methamphetamine chronically, in doses relevant to recreational usage patterns, to nonhuman primates. Neurostructural analysis revealed decreased dendritic material and loss of spines in frontal lobe neurons. Molecular examination demonstrated that type I interferons (interferon-alpha and interferon-beta) increased in the frontal lobe in response to chronic methamphetamine treatment, in correlation with the neuronal changes. Chronic methamphetamine thus results in significant changes in the primate brain, inducing cytokines and altering neuronal structure, both of which can contribute to functional abnormalities.
Asunto(s)
Estimulantes del Sistema Nervioso Central/farmacología , Lóbulo Frontal/efectos de los fármacos , Interferón Tipo I/efectos de los fármacos , Metanfetamina/farmacología , Neuronas/efectos de los fármacos , Animales , Lóbulo Frontal/patología , Expresión Génica/efectos de los fármacos , Interferón Tipo I/biosíntesis , Macaca mulatta , Neuronas/patología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Regulación hacia ArribaRESUMEN
Estrogens have long been implicated in influencing cognitive processes, yet the molecular mechanisms underlying these effects and the roles of the estrogen receptors alpha (ERalpha) and beta (ERbeta) remain unclear. Using pharmacological, biochemical and behavioral techniques, we demonstrate that the effects of estrogen on hippocampal synaptic plasticity and memory are mediated through ERbeta. Selective ERbeta agonists increased key synaptic proteins in vivo, including PSD-95, synaptophysin and the AMPA-receptor subunit GluR1. These effects were absent in ERbeta knockout mice. In hippocampal slices, ERbeta activation enhanced long-term potentiation, an effect that was absent in slices from ERbeta knockout mice. ERbeta activation induced morphological changes in hippocampal neurons in vivo, including increased dendritic branching and increased density of mushroom-type spines. An ERbeta agonist, but not an ERalpha agonist, also improved performance in hippocampus-dependent memory tasks. Our data suggest that activation of ERbeta can regulate hippocampal synaptic plasticity and improve hippocampus-dependent cognition.
Asunto(s)
Receptor beta de Estrógeno/metabolismo , Estrógenos/metabolismo , Hipocampo/metabolismo , Memoria/fisiología , Plasticidad Neuronal/fisiología , Neuronas/metabolismo , Animales , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/efectos de los fármacos , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Espinas Dendríticas/efectos de los fármacos , Espinas Dendríticas/metabolismo , Estradiol/metabolismo , Estradiol/farmacología , Receptor beta de Estrógeno/agonistas , Receptor beta de Estrógeno/genética , Estrógenos/agonistas , Estrógenos/farmacología , Femenino , Hipocampo/citología , Hipocampo/efectos de los fármacos , Potenciación a Largo Plazo/efectos de los fármacos , Potenciación a Largo Plazo/fisiología , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Aprendizaje por Laberinto/fisiología , Memoria/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Plasticidad Neuronal/efectos de los fármacos , Neuronas/citología , Neuronas/efectos de los fármacos , Técnicas de Cultivo de Órganos , Ovariectomía , Fosforilación/efectos de los fármacos , Ratas , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiologíaRESUMEN
OBJECTIVE: Perinatal exposure to polychlorinated biphenyls (PCBs) is associated with decreased IQ scores, impaired learning and memory, psychomotor difficulties, and attentional deficits in children. It is postulated that these neuropsychological deficits reflect altered patterns of neuronal connectivity. To test this hypothesis, we examined the effects of developmental PCB exposure on dendritic growth. METHODS: Rat dams were gavaged from gestational day 6 through postnatal day (PND) 21 with vehicle (corn oil) or the commercial PCB mixture Aroclor 1254 (6 mg/kg/day). Dendritic growth and molecular markers were examined in pups during development. RESULTS: Golgi analyses of CA1 hippocampal pyramidal neurons and cerebellar Purkinje cells indicated that developmental exposure to PCBs caused a pronounced age-related increase in dendritic growth. Thus, even though dendritic lengths were significantly attenuated in PCB-treated animals at PND22, the rate of growth was accelerated at later ages such that by PND60, dendritic growth was comparable to or even exceeded that observed in vehicle controls. Quantitative reverse transcriptase polymerase chain reaction analyses demonstrated that from PND4 through PND21, PCBs generally increased expression of both spinophilin and RC3/neurogranin mRNA in the hippocampus, cerebellum, and cortex with the most significant increases observed in the cortex. CONCLUSIONS: This study demonstrates that developmental PCB exposure alters the ontogenetic profile of dendritogenesis in critical brain regions, supporting the hypothesis that disruption of neuronal connectivity contributes to neuropsychological deficits seen in exposed children.
Asunto(s)
Células Dendríticas/efectos de los fármacos , Contaminantes Ambientales/toxicidad , Bifenilos Policlorados/toxicidad , Efectos Tardíos de la Exposición Prenatal , Animales , Aumento de la Célula , Niño , Trastornos del Conocimiento/inducido químicamente , Discapacidades del Desarrollo/inducido químicamente , Modelos Animales de Enfermedad , Femenino , Humanos , Embarazo , Células de Purkinje/efectos de los fármacos , Tractos Piramidales/citología , Tractos Piramidales/efectos de los fármacos , Ratas , Ratas Long-EvansRESUMEN
Lifelong cognitive stimulation is associated with a lower risk of Alzheimer's disease (AD), but causality is difficult to prove. We therefore sought to investigate the preventative potential of environmental enrichment (EE) using mice expressing both human mutant presenilin-1 and the amyloid precursor protein (PS1/PDAPP). At weaning, mice were placed into either an enriched or standard housing environment. Behavioral testing at 4.5-6 months showed that environmentally enriched PS1/PDAPP mice outperformed mice in standard housing, and were behaviorally indistinguishable from non-transgenic mice across multiple cognitive domains. PS1/PDAPP mice exposed to both environmental enrichment and behavioral testing, but not to EE alone, showed 50% less brain beta-amyloid without improved dendritic morphology. Microarray analysis revealed large enrichment-induced changes in hippocampal expression of genes/proteins related to Abeta sequestration and synaptic plasticity. These results indicate that EE protects against cognitive impairment in AD transgenic mice through a dual mechanism, including both amyloid dependent and independent mechanisms.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Péptidos beta-Amiloides/fisiología , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/terapia , Ambiente , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/genética , Animales , Conducta Animal , Encéfalo/metabolismo , Encéfalo/ultraestructura , Trastornos del Conocimiento/genética , Trastornos del Conocimiento/patología , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática/métodos , Regulación de la Expresión Génica/fisiología , Humanos , Aprendizaje por Laberinto/fisiología , Memoria a Corto Plazo/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Análisis de Secuencia por Matrices de Oligonucleótidos/métodos , Inhibidores de Fosfodiesterasa/uso terapéutico , Presenilina-1/genética , Rolipram/uso terapéutico , Tinción con Nitrato de Plata/métodosRESUMEN
We have studied the influence of predator stress (30 min of cat exposure) on long-term (24 h) spatial memory and the density of spines in basilar dendrites of CA1 neurons. Predator stress occurred either immediately before water maze training (Stress Pre-Training) or before the 24 h memory test (Stress Pre-Retrieval). The Control (nonstress) group exhibited excellent long-term spatial memory and a robust increase in the density of stubby, but not mushroom, shaped spines. The Stress Pre-Training group had impaired long-term memory and did not exhibit any changes in spine density. The Stress Pre-Retrieval group was also impaired in long-term memory performance, but this group exhibited an increase in the density of stubby, but not mushroom, shaped spines, which was indistinguishable from the control group. These findings indicate that: (1) A single day of water maze training under control conditions produced intact long-term memory and an increase in the density of stubby spines in CA1; (2) Stress before training interfered with the consolidation of information into long-term memory and suppressed the training-induced increase in spine density; and (3) Stress immediately before the 24 h memory test trial impaired the retrieval of the stored memory, but did not reverse the training-induced increase in CA1 spine density. Overall, this work provides evidence of structural plasticity in dendrites of CA1 neurons which may be involved in the consolidation process, and how spinogenesis and memory are modulated by stress.
Asunto(s)
Espinas Dendríticas/fisiología , Hipocampo/fisiología , Memoria/fisiología , Percepción Espacial/fisiología , Estrés Psicológico/fisiopatología , Amnesia/fisiopatología , Animales , Gatos , Espinas Dendríticas/ultraestructura , Hipocampo/citología , Masculino , Aprendizaje por Laberinto/fisiología , Plasticidad Neuronal/fisiología , Conducta Predatoria , Ratas , Ratas Sprague-DawleyRESUMEN
The hippocampus is highly sensitive to ischemia and is one of the most extensively damaged regions of brain during cardiac arrest. Damage to hippocampus can subsequently lead to learning and memory deficits. The current study used the Morris water maze to characterize spatial learning and memory deficits elicited by 8 min of cardiac arrest with cardiopulmonary resuscitation (CA/CPR) in mice, which is associated with a 25-50% decrease in CA1 neurons. Mice were trained to navigate the water maze prior to CA/CPR or sham surgery (SHAM). They were retested in the water maze on days 7 and 8 postsurgery; both CA/CPR and SHAM groups were able to perform the task at presurgical levels. However, when the hidden platform was moved to a new location, the SHAM mice were able to adapt more quickly to the change and swam a shorter distance in search of the platform than did CA/CPR mice. Thus, CA/CPR did not affect the ability of mice to retain a previously learned platform location, but it did affect their ability to learn a new platform location. This behavioural impairment was correlated with dendritic spine density in the CA1 region of the hippocampus. Data presented here suggest that morphological changes, such as spine density, that occur in neurons that survive CA/CPR may be associated with cognitive impairments.
Asunto(s)
Reanimación Cardiopulmonar , Paro Cardíaco Inducido/psicología , Aprendizaje por Laberinto/fisiología , Memoria/fisiología , Células Piramidales/fisiología , Percepción Espacial/fisiología , Médula Espinal/fisiología , Animales , Presión Sanguínea , Encéfalo/patología , Encéfalo/fisiopatología , Modelos Animales de Enfermedad , Masculino , Ratones , Ratones Endogámicos C57BL , Médula Espinal/citología , Médula Espinal/patologíaRESUMEN
This study evaluated somatic and dendritic growth of neurons in the frontoparietal cortex of Igf1-/- brains. Pyramidal neuron density was increased by approximately 25% (P =.005) and soma size reduced by approximately 10% (P <.001). Golgi staining revealed that cortical layer II-III neurons exhibited a significant reduction in dendritic length and complexity in Igf1 null mice. Dendritic spine density and presumably synaptic contacts were reduced by 16% (P =.002). Similar findings were obtained for cortical layer V and piriform cortex pyramids. Supporting a reduction in synapses, synaptotagmin levels were reduced by 30% (P <.02) in the Igf1 null brain. Investigation of factors critically involved in dendritic growth and synaptogenesis showed an approximately 50% reduction in cortical CDC42 protein expression (P <.001) and an approximately 10% reduction in brain cholesterol levels (P <.01) in Igf1 null mice. Evidence is presented that Igf1 deletion causes disruptions in lipid and microtubule metabolism, leading to impaired neuronal somatic and dendritic growth. Published 2003 Wiley-Liss, Inc.