RESUMEN
In utero exposure of rodents to valproic acid (VPA) has been proposed to induce an adult phenotype with behavioural characteristics reminiscent of those observed in autism spectrum disorder (ASD). Our previous studies have demonstrated the social cognition deficits observed in this model, a major core symptom of ASD, to be ameliorated following chronic administration of histone deacetylase (HDAC) inhibitors. Using this model, we now demonstrate pentyl-4-yn-VPA, an analogue of valproate and HDAC inhibitor, to significantly ameliorate deficits in social cognition as measured using the social approach avoidance paradigm as an indicator of social reciprocity and spatial learning to interrogate dorsal stream cognitive processing. The effects obtained with pentyl-4-yn-VPA were found to be similar to those obtained with SAHA, a pan-specific HDAC inhibitor. Histones isolated from the cerebellar cortex and immunoblotted with antibodies recognising lysine-specific modification revealed SAHA and pentyl-4-yn-VPA to enhance the acetylation status of H4K8. Additionally, the action of pentyl-4-yn-VPA, could be differentiated from that of SAHA by its ability to decrease H3K9 acetylation and enhance H3K14 acetylation. The histone modifications mediated by pentyl-4-yn-VPA are suggested to act cooperatively through differential acetylation of the promoter and transcription regions of active genes.
Asunto(s)
Conducta Animal/efectos de los fármacos , Corteza Cerebelosa/efectos de los fármacos , Trastornos Generalizados del Desarrollo Infantil/tratamiento farmacológico , Cognición/efectos de los fármacos , Inhibidores de Histona Desacetilasas/farmacología , Conducta Social , Ácido Valproico/análogos & derivados , Acetilación , Animales , Corteza Cerebelosa/enzimología , Trastornos Generalizados del Desarrollo Infantil/inducido químicamente , Trastornos Generalizados del Desarrollo Infantil/enzimología , Trastornos Generalizados del Desarrollo Infantil/psicología , Modelos Animales de Enfermedad , Femenino , Histonas/metabolismo , Ácidos Hidroxámicos/farmacología , Masculino , Exposición Materna , Aprendizaje por Laberinto/efectos de los fármacos , Actividad Motora/efectos de los fármacos , Embarazo , Efectos Tardíos de la Exposición Prenatal , Ratas Wistar , Ácido Valproico/farmacología , VorinostatRESUMEN
The putative antidepressant captodiamine is a 5-HT2c receptor antagonist and agonist at sigma-1 and D3 dopamine receptors, exerts an anti-immobility action in the forced swim paradigm, and enhances dopamine turnover in the frontal cortex. Captodiamine has also been found to ameliorate stress-induced anhedonia, reduce the associated elevations of hypothalamic corticotrophin-releasing factor (CRF) and restore the reductions in hypothalamic BDNF expression. Here we demonstrate chronic administration of captodiamine to have no significant effect on hypothalamic CRF expression through sigma-1 receptor agonism; however, both sigma-1 receptor agonism or 5-HT2c receptor antagonism were necessary to enhance BDNF expression. Regulation of BDNF expression by captodiamine was associated with increased phosphorylation of transcription factor CREB and mediated through sigma-1 receptor agonism but blocked by 5-HT2c receptor antagonism. The existence of two separate signalling pathways was confirmed by immunolocalisation of each receptor to distinct cell populations in the paraventricular nucleus of the hypothalamus. Increased BDNF induced by captodiamine was also associated with enhanced expression of synapsin, but not PSD-95, suggesting induction of long-term structural plasticity between hypothalamic synapses. These unique features of captodiamine may contribute to its ability to ameliorate stress-induced anhedonia as the hypothalamus plays a prominent role in regulating HPA axis activity.
Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/biosíntesis , Etilaminas/farmacología , Hipotálamo/metabolismo , Receptor de Serotonina 5-HT2C/metabolismo , Receptores sigma/agonistas , Antagonistas del Receptor de Serotonina 5-HT2/farmacología , Sulfuros/farmacología , Animales , Antidepresivos/agonistas , Antidepresivos/antagonistas & inhibidores , Antidepresivos/farmacología , Proteína de Unión a CREB/metabolismo , Carbazoles/farmacología , Hormona Liberadora de Corticotropina/biosíntesis , Homólogo 4 de la Proteína Discs Large , Interacciones Farmacológicas , Regulación de la Expresión Génica/efectos de los fármacos , Guanilato-Quinasas/biosíntesis , Hipotálamo/efectos de los fármacos , Masculino , Proteínas de la Membrana/biosíntesis , Ratones , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Fosforilación/efectos de los fármacos , Ritanserina/farmacología , Transducción de Señal/efectos de los fármacos , Sinapsinas/biosíntesis , Receptor Sigma-1RESUMEN
A range of adverse, early life environmental influences such as viral infection and social deprivation are thought to increase risk of psychiatric illness later in life. Here, we used peripheral administration of the viral infection mimic polyriboinosinic-polyribocytidylic acid (polyI:C) to compare the consequences of peripubertal infection and isolation rearing. Isolation rearing induced deficits in sensorimotor gating and recognition memory while no changes in social interaction or spatial learning were observed. PolyI:C injection during the peripubertal period markedly increased expression of interferon-stimulated genes (Ifit2, Prkr, Mx2 and Irf7) in the hippocampal dentate gyrus demonstrating that peripheral administration of the viral mimic in the adolescent animal does have direct effects in the brain. Peripubertal infection mimicry induced a similar but later emerging behavioural deficit in prepulse inhibition implying the existence of a peripubertal window of opportunity for viral-mediated cytokine increases to impact brain development and function. PolyI:C treatment also impaired novel object recognition but did not alter spatial reference memory or social interaction. Combining the polyI:C challenge with social isolation did not exacerbate the behavioural deficits seen with isolation rearing alone. Using Irf7 as a marker, peripubertal viral infection mimicry, isolation rearing and a combination of both were all seen to produce a long-lasting molecular imprint on the interferon-associated signalling pathway in the principal neuron population of the hippocampal dentate gyrus. The data suggest that the sensitivity of brain structure and function to disruption by viral infection extends into the peripubertal period. Moreover, augmented interferon signalling in hippocampus may represent a common molecular imprint of environmental insults associated with neuropsychiatric illnesses like schizophrenia.
Asunto(s)
Conducta Animal , Giro Dentado , Inductores de Interferón/farmacología , Factor 7 Regulador del Interferón , Interferones/metabolismo , Poli I-C/farmacología , Virosis/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Conducta Animal/fisiología , Giro Dentado/efectos de los fármacos , Giro Dentado/metabolismo , Proteínas de Unión al GTP/efectos de los fármacos , Proteínas de Unión al GTP/metabolismo , Factor 7 Regulador del Interferón/efectos de los fármacos , Factor 7 Regulador del Interferón/metabolismo , Masculino , Proteínas de Resistencia a Mixovirus , Ratas , Ratas Wistar , Filtrado Sensorial/efectos de los fármacos , Filtrado Sensorial/fisiología , Maduración Sexual/fisiología , Aislamiento SocialRESUMEN
Aggregation of the amyloid ß-protein (Aß) is believed to play a central role in initiating the molecular cascade that culminates in Alzheimer-type dementia (AD), a disease which in its early stage is characterized by synaptic loss and impairment of episodic memory. Here we show that intracerebroventricular injection of Aß-containing water-soluble extracts of AD brain inhibits consolidation of the memory of avoidance learning in the rat and that this effect is highly dependent on the interval between learning and administration. When injected at 1 hour post training extracts from 2 different AD brains significantly impaired recall tested at 48 hours. Ultrastructural examination of hippocampi from animals perfused after 48 hours revealed that Aß-mediated impairment of avoidance memory was associated with lower density of synapses and altered synaptic structure in the dentate gyrus and CA1 fields. These behavioral and ultrastructural data suggest that human brain-derived Aß impairs formation of long-term memory by compromising the structural plasticity essential for consolidation and that Aß targets processes initiated very early in the consolidation pathway.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/metabolismo , Péptidos beta-Amiloides/farmacología , Reacción de Prevención/efectos de los fármacos , Encéfalo/metabolismo , Plasticidad Neuronal/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Anciano , Anciano de 80 o más Años , Animales , Femenino , Humanos , Masculino , Memoria Episódica , Ratas , Ratas WistarRESUMEN
In utero exposure of rodents to valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, has been proposed to induce an adult phenotype with behavioural characteristics reminiscent of those observed in autism spectrum disorder (ASD). We have evaluated the face validity of this model in terms of social cognition deficits which are a major core symptom of ASD. We employed the social approach avoidance paradigm as a measure of social reciprocity, detection of biological motion that is crucial to social interactions, and spatial learning as an indicator of dorsal stream processing of social cognition and found each parameter to be significantly impaired in Wistar rats with prior in utero exposure to VPA. We found no significant change in the expression of neural cell adhesion molecule polysialylation state (NCAM PSA), a measure of construct validity, but a complete inability to increase its glycosylation state which is necessary to mount the neuroplastic response associated with effective spatial learning. Finally, in all cases, we found chronic HDAC inhibition, with either pan-specific or HDAC1-3 isoform-specific inhibitors, to significantly ameliorate deficits in both social cognition and its associated neuroplastic response. We conclude that in utero exposure to VPA provides a robust animal model for the social cognitive deficits of ASD and a potential screen for the development of novel therapeutics for this condition.
Asunto(s)
Trastornos Generalizados del Desarrollo Infantil/tratamiento farmacológico , Trastornos del Conocimiento/prevención & control , Modelos Animales de Enfermedad , Histona Desacetilasa 1/antagonistas & inhibidores , Inhibidores de Histona Desacetilasas/uso terapéutico , Molécula L1 de Adhesión de Célula Nerviosa/metabolismo , Plasticidad Neuronal/efectos de los fármacos , Ácidos Siálicos/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Niño , Trastornos Generalizados del Desarrollo Infantil/metabolismo , Trastornos Generalizados del Desarrollo Infantil/patología , Trastornos Generalizados del Desarrollo Infantil/fisiopatología , Trastornos del Conocimiento/etiología , Giro Dentado/efectos de los fármacos , Giro Dentado/metabolismo , Giro Dentado/patología , Femenino , Histona Desacetilasa 1/metabolismo , Inhibidores de Histona Desacetilasas/toxicidad , Humanos , Masculino , Terapia Molecular Dirigida , Proteínas del Tejido Nervioso/metabolismo , Neuronas/efectos de los fármacos , Neuronas/enzimología , Neuronas/metabolismo , Neuronas/patología , Embarazo , Efectos Tardíos de la Exposición Prenatal , Ratas , Ratas Wistar , Conducta SocialRESUMEN
Information storage in the brain depends on the ability of neurons to alter synaptic connectivity within key circuitries such as the hippocampus. Memory-associated synaptic plasticity is mediated by a temporal cascade of de novo protein synthesis and altered protein processing. Here, we have used two-dimensional difference in gel electrophoresis (2-D DIGE) to investigate memory-specific protein changes in the hippocampal dentate gyrus at increasing times following spatial learning. We identified 42 proteins that were significantly regulated in the first 24 h of spatial memory consolidation. Two distinct waves of protein expression regulation were evident, at 3 and 12 h post-learning and this is in agreement with studies employing inhibitors of global translation. Functional classification of the memory-associated proteins revealed that the majority of regulated proteins contributed either to cellular structure or cellular metabolism. For example, actins, tubulins and intermediate filament proteins, core proteins of the three major cytoskeletal components, were dynamically regulated at times that suggest a role in memory-associated synaptic reorganization. Increased proteasome-mediated protein degradation was evident in the early post-training period including the down-regulation of phosphoprotein enriched in astrocytes 15 kDa, a key inhibitor of extracellular signal-regulated kinase signaling. Some of the most substantial protein expression changes were observed for secreted carrier proteins including transthyretin and serum albumin at 6-12 h post-learning, regulations that could serve an important role in increasing the supply of retinoic acid and thyroid hormone, key synaptic plasticity-promoting signals in the adult brain. Together these observations provide further insight into protein level regulations occurring in the hippocampus during spatial memory consolidation.
Asunto(s)
Giro Dentado/metabolismo , Aprendizaje por Laberinto , Proteoma/metabolismo , Proteómica , Animales , Proteínas Reguladoras de la Apoptosis , Regulación de la Expresión Génica , Masculino , Memoria , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Prealbúmina/genética , Prealbúmina/metabolismo , Proteoma/genética , Ratas , Ratas Wistar , Albúmina Sérica/genética , Albúmina Sérica/metabolismo , Electroforesis Bidimensional Diferencial en GelRESUMEN
Extensive research has implicated the amyloid-ß protein (Aß) in the aetiology of Alzheimer's disease (AD). This protein has been shown to produce memory deficits when injected into rodent brain and in mouse models of AD Aß production is associated with impaired learning and/or recall. Here we examined the effects of cell-derived SDS-stable 7PA2-derived soluble Aß oligomers on consolidation of avoidance learning. At 0, 3, 6, 9 or 12h after training, animals received an intracerebroventricular injection of Aß-containing or control media and recall was tested at 24 and 48 h. Immediately after 48 h recall animals were transcardially perfused and the brain removed for sectioning and EM analysis. Rats receiving injections of Aß at 6 or 9h post-training showed a significant impairment in memory consolidation at 48 h. Importantly, impaired animals injected at 9h had significantly fewer synapses in the dentate gyrus. These data suggest that Aß low-n oligomers target specific temporal facets of consolidation-associated synaptic remodelling whereby loss of functional synapses results in impaired consolidation.
Asunto(s)
Péptidos beta-Amiloides/toxicidad , Memoria/fisiología , Inhibición Neural/fisiología , Sinapsis/patología , Péptidos beta-Amiloides/metabolismo , Animales , Reacción de Prevención/fisiología , Células CHO , Cricetinae , Cricetulus , Humanos , Masculino , Trastornos de la Memoria/etiología , Trastornos de la Memoria/patología , Trastornos de la Memoria/fisiopatología , Plasticidad Neuronal/fisiología , Ratas , Ratas Wistar , Sinapsis/metabolismoRESUMEN
Given that suppressed reelin protein synthesis is associated with cognitive dysfunction in both rodents and humans, we examined the ontogeny of these deficits in rats reared in isolation as a basis for understanding developmental emergence of neuropsychiatric illness. Isolation rearing exerted minimal effects on spatial learning other than to inhibit the transient learning improvement observed in social reared rats at postnatal day 60. By contrast, at postnatal day 80, animals reared in isolation were significantly impaired in an avoidance conditioning paradigm, a deficit that correlated with suppressed reelin synthesis restricted to the ventral aspect of the dentate gyrus. These findings suggest that environmental factors alone can impair forms of cognitive development with relevant region-specific dysfunctional plasticity.
Asunto(s)
Reacción de Prevención/fisiología , Moléculas de Adhesión Celular Neuronal/metabolismo , Condicionamiento Clásico/fisiología , Proteínas de la Matriz Extracelular/metabolismo , Hipocampo/metabolismo , Discapacidades para el Aprendizaje/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Serina Endopeptidasas/metabolismo , Aislamiento Social , Envejecimiento , Animales , Moléculas de Adhesión Celular Neuronal/biosíntesis , Giro Dentado/metabolismo , Proteínas de la Matriz Extracelular/biosíntesis , Masculino , Aprendizaje por Laberinto/fisiología , Proteínas del Tejido Nervioso/biosíntesis , Ratas , Ratas Wistar , Proteína Reelina , Serina Endopeptidasas/biosíntesis , Percepción Espacial/fisiología , Factores de TiempoRESUMEN
The critical sequence of molecular, neurotransmission and synaptic disruptions that underpin the emergence of psychiatric disorders like schizophrenia remain to be established with progress only likely using animal models that capture key features of such disorders. We have related the emergence of behavioural, neurochemical and synapse ultrastructure deficits to transcriptional dysregulation in the medial prefrontal cortex of Wistar rats reared in isolation. Isolation reared animals developed sensorimotor deficits at postnatal day 60 which persisted into adulthood. Analysis of gene expression prior to the emergence of the sensorimotor deficits revealed a significant disruption in transcriptional control, notably of immediate early and interferon-associated genes. At postnatal day 60 many gene transcripts relating particularly to GABA transmission and synapse structure, for example Gabra4, Nsf, Syn2 and Dlgh1, transiently increased expression. A subsequent decrease in genes such as Gria2 and Dlgh2 at postnatal day 80 suggested deficits in glutamatergic transmission and synapse integrity, respectively. Microdialysis studies revealed decreased extracellular glutamate suggesting a state of hypofrontality while ultrastructural analysis showed total and perforated synapse complement in layer III to be significantly reduced in the prefrontal cortex of postnatal day 80 isolated animals. These studies provide a molecular framework to understand the developmental emergence of the structural and behavioural characteristics that may in part define psychiatric illness.
Asunto(s)
Corteza Cerebral/metabolismo , Regulación de la Expresión Génica/fisiología , Aislamiento Social/psicología , Animales , Conducta Animal/fisiología , Corteza Cerebral/química , Corteza Cerebral/ultraestructura , Biología Computacional , ADN/biosíntesis , ADN/genética , Masculino , Microdiálisis , Actividad Motora/fisiología , Familia de Multigenes , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN/biosíntesis , ARN/genética , ARN Complementario/biosíntesis , ARN Complementario/genética , Ratas , Ratas Wistar , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Estrés Psicológico/genética , Estrés Psicológico/psicología , Sinapsis/fisiología , Factores de TranscripciónRESUMEN
Long-term memory is formed by alterations in glutamate-dependent excitatory synaptic transmission, which is in turn regulated by synaptosomal protein of 25 kDa (SNAP-25), a key component of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex essential for exocytosis of neurotransmitter-filled synaptic vesicles. Both reduced and excessive SNAP-25 activity has been implicated in various disease states that involve cognitive dysfunctions such as attention deficit hyperactivity disorder, schizophrenia and Alzheimer's disease. Here, we over-express SNAP-25 in the adult rat dorsal hippocampus by infusion of a recombinant adeno-associated virus vector, to evaluate the consequence of late adolescent-adult dysfunction of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor protein in the absence of developmental disruption. We report a specific and significant increase in the levels of extracellular glutamate detectable by microdialysis and a reduction in paired-pulse facilitation in the hippocampus. In addition, SNAP-25 over-expression produced cognitive deficits, delaying acquisition of a spatial map in the water maze and impairing contextual fear conditioning, both tasks known to be dorsal hippocampal dependent. The high background transmission state and pre-synaptic dysfunction likely result in interference with requisite synapse selection during spatial and fear memory consolidation. Together these studies provide the first evidence that excess SNAP-25 activity, restricted to the adult period, is sufficient to mediate significant deficits in the memory formation process.
Asunto(s)
Regulación de la Expresión Génica/fisiología , Hipocampo/metabolismo , Trastornos de la Memoria , Plasticidad Neuronal/fisiología , Proteína 25 Asociada a Sinaptosomas/metabolismo , Animales , Reacción de Prevención/fisiología , Biofisica/métodos , Línea Celular Transformada , Condicionamiento Clásico/fisiología , Dependovirus/genética , Dependovirus/metabolismo , Modelos Animales de Enfermedad , Estimulación Eléctrica/métodos , Conducta Exploratoria/fisiología , Citometría de Flujo/métodos , Ácido Glutámico/metabolismo , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Hipocampo/fisiología , Humanos , Técnicas In Vitro , Masculino , Aprendizaje por Laberinto/fisiología , Trastornos de la Memoria/metabolismo , Trastornos de la Memoria/patología , Trastornos de la Memoria/fisiopatología , Microdiálisis/métodos , Inhibición Neural/fisiología , Ratas , Ratas Wistar , Proteína 25 Asociada a Sinaptosomas/genética , Transducción Genética/métodos , Transfección/métodosRESUMEN
To further understand the procognitive actions of GSK189254, a histamine H(3) receptor antagonist, we determined its influence on the modulation of hippocampal neural cell adhesion molecule (NCAM) polysialylation (PSA) state, a necessary neuroplastic mechanism for learning and memory consolidation. A 4-day treatment with GSK189254 significantly increased basal expression of dentate polysialylated cells in rats with the maximal effect being observed at 0.03-0.3 mg/kg. At the optimal dose (0.3 mg/kg), GSK189254 enhanced water maze learning and the associated transient increase in NCAM-polysialylated cells. The increase in dentate polysialylated cell frequency induced by GSK189254 was not attributable to enhanced neurogenesis, although it did induce a small, but significant, increase in the survival of these newborn cells. GSK189254 (0.3 mg/kg) was without effect on polysialylated cell frequency in the entorhinal and perirhinal cortex, but significantly increased the diffuse PSA staining observed in the anterior, ventromedial, and dorsomedial aspects of the hypothalamus. Consistent with its ability to enhance the learning-associated, post-training increases in NCAM PSA state, GSK189254 (0.3 mg/kg) reversed the amnesia induced by scopolamine given in the 6-h post-training period after training in an odor discrimination paradigm. Moreover, GSK189254 significantly improved the performance accuracy of a delayed match-to-position paradigm, a task dependent on the prefrontal cortex and degree of cortical arousal, the latter may be related to enhanced NCAM PSA-associated plasticity in the hypothalamus. The procognitive actions of H3 antagonism combined with increased NCAM PSA expression may exert a disease-modifying action in conditions harboring fundamental deficits in NCAM-mediated neuroplasticity, such as schizophrenia and Alzheimer's disease.
Asunto(s)
Benzazepinas/farmacología , Aprendizaje Discriminativo/efectos de los fármacos , Antagonistas de los Receptores Histamínicos H3/farmacología , Memoria/efectos de los fármacos , Moléculas de Adhesión de Célula Nerviosa/metabolismo , Plasticidad Neuronal/efectos de los fármacos , Niacinamida/análogos & derivados , Amnesia/inducido químicamente , Amnesia/tratamiento farmacológico , Amnesia/fisiopatología , Animales , Benzazepinas/administración & dosificación , Encéfalo/efectos de los fármacos , Encéfalo/fisiología , Encéfalo/fisiopatología , Supervivencia Celular/efectos de los fármacos , Aprendizaje Discriminativo/fisiología , Relación Dosis-Respuesta a Droga , Antagonistas de los Receptores Histamínicos H3/administración & dosificación , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Aprendizaje por Laberinto/fisiología , Memoria/fisiología , Neurogénesis/efectos de los fármacos , Plasticidad Neuronal/fisiología , Neuronas/efectos de los fármacos , Neuronas/fisiología , Pruebas Neuropsicológicas , Niacinamida/administración & dosificación , Niacinamida/farmacología , Percepción Olfatoria/efectos de los fármacos , Percepción Olfatoria/fisiología , Ratas , Ratas Wistar , Escopolamina , Factores de TiempoRESUMEN
Polysialylation of the neural cell adhesion molecule (NCAM PSA) is necessary for the consolidation processes of hippocampus-based learning. Previously, we have found inhibition of protein kinase C delta (PKCdelta) to be associated with increased polysialyltransferase (PST) activity, suggesting inhibitors of this kinase might ameliorate cognitive deficits. Using a rottlerin template, a drug previously considered an inhibitor of PKCdelta, we searched the Compounds Available for Purchase (CAP) database with the Accelrys((R)) Catalyst programme for structurally similar molecules and, using the available crystal structure of the phorbol-binding domain of PKCdelta, found that diferuloylmethane (curcumin) docked effectively into the phorbol site. Curcumin increased NCAM PSA expression in cultured neuro-2A neuroblastoma cells and this was inversely related to PKCdelta protein expression. Curcumin did not directly inhibit PKCdelta activity but formed a tight complex with the enzyme. With increasing doses of curcumin, the Tyr(131) residue of PKCdelta, which is known to direct its degradation, became progressively phosphorylated and this was associated with numerous Tyr(131)-phospho-PKCdelta fragments. Chronic administration of curcumin in vivo also increased the frequency of polysialylated cells in the dentate infragranular zone and significantly improved the acquisition and consolidation of a water maze spatial learning paradigm in both adult and aged cohorts of Wistar rats. These results further confirm the role of PKCdelta in regulating PST and NCAM PSA expression and provide evidence that drug modulation of this system enhances the process of memory consolidation.
Asunto(s)
Envejecimiento/metabolismo , Curcumina/farmacología , Giro Dentado/metabolismo , Aprendizaje por Laberinto/fisiología , Molécula L1 de Adhesión de Célula Nerviosa/biosíntesis , Proteína Quinasa C-delta/metabolismo , Ácidos Siálicos/biosíntesis , Envejecimiento/efectos de los fármacos , Animales , Línea Celular Tumoral , Giro Dentado/efectos de los fármacos , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/fisiología , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Ratas , Ratas Wistar , Conducta Espacial/efectos de los fármacos , Conducta Espacial/fisiologíaRESUMEN
The prefrontal cortex (PFC) is an interconnected set of cortical areas that function in the synthesis of a diverse range of information and production of complex behaviour. It is now clear that these frontal structures, through bidirectional excitatory communication with the hippocampal formation, also play a substantial role in long-term memory consolidation. In the hippocampus, morphological synaptic plasticity, supported by regulation of neural cell adhesion molecule (NCAM) polysialylation status, is crucial to information storage. The recent description of polysialylated neurons in the various fields of the medial PFC suggests these structures to possess a similar capacity for synaptic plasticity. Here, using double-labelling immunohistochemistry with glutamic acid decarboxylase 67, we report that the nature of NCAM polysialic acid-positive neurons in the PFC is region-specific, with a high proportion (30-50%) of a gamma-aminobutyric acid (GABA)ergic phenotype in the more ventral infralimbic, orbitofrontal and insular cortices compared with just 10% in the dorsal structures of the cingulate, prelimbic and frontal cortices. Moreover, spatial learning was accompanied by activations in polysialylation expression in ventral PFC structures, while avoidance conditioning involved downregulation of this plasticity marker that was restricted to the dorsomedial PFC--the cingulate and prelimbic cortices. Thus, in contrast to other structures integrated functionally with the hippocampus, memory-associated plasticity mobilized in the PFC is region-, cell type- and task-specific.
Asunto(s)
Aprendizaje/fisiología , Molécula L1 de Adhesión de Célula Nerviosa/metabolismo , Plasticidad Neuronal/fisiología , Corteza Prefrontal , Ácidos Siálicos/metabolismo , Animales , Humanos , Masculino , Molécula L1 de Adhesión de Célula Nerviosa/química , Neuronas/citología , Neuronas/fisiología , Corteza Prefrontal/citología , Corteza Prefrontal/metabolismo , Ratas , Ratas Wistar , Ácidos Siálicos/químicaRESUMEN
Alzheimer's disease constitutes a rising threat to public health. Despite extensive research in cellular and animal models, identifying the pathogenic agent present in the human brain and showing that it confers key features of Alzheimer's disease has not been achieved. We extracted soluble amyloid-beta protein (Abeta) oligomers directly from the cerebral cortex of subjects with Alzheimer's disease. The oligomers potently inhibited long-term potentiation (LTP), enhanced long-term depression (LTD) and reduced dendritic spine density in normal rodent hippocampus. Soluble Abeta from Alzheimer's disease brain also disrupted the memory of a learned behavior in normal rats. These various effects were specifically attributable to Abeta dimers. Mechanistically, metabotropic glutamate receptors were required for the LTD enhancement, and N-methyl D-aspartate receptors were required for the spine loss. Co-administering antibodies to the Abeta N-terminus prevented the LTP and LTD deficits, whereas antibodies to the midregion or C-terminus were less effective. Insoluble amyloid plaque cores from Alzheimer's disease cortex did not impair LTP unless they were first solubilized to release Abeta dimers, suggesting that plaque cores are largely inactive but sequester Abeta dimers that are synaptotoxic. We conclude that soluble Abeta oligomers extracted from Alzheimer's disease brains potently impair synapse structure and function and that dimers are the smallest synaptotoxic species.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/química , Encéfalo/metabolismo , Hipocampo/metabolismo , Memoria , Sinapsis/metabolismo , Animales , Encéfalo/patología , Espinas Dendríticas , Dimerización , Humanos , Aprendizaje , Ratones , Plasticidad Neuronal , Neuronas/metabolismo , RatasRESUMEN
While there is now substantial evidence that 5-HT(6) antagonism leads to significantly improved cognitive ability, the mechanism(s) and/or pathway(s) involved are poorly understood. We have evaluated the consequence of chronic administration of the 5-HT(6) receptor antagonists SB-271046 and SB-399885 on neural cell adhesion molecule polysialylation state (NCAM PSA), a neuroplastic mechanism necessary for memory consolidation. Quantitative analysis of NCAM PSA immunopositive neurons in the dentate gyrus of drug-treated animals revealed a dose-dependent increase in polysialylated cell frequency following treatment with both SB-271046 and SB-399885. These effects could not be attributed to increased neurogenesis, as no difference in the rate of bromodeoxyuridine incorporation was apparent between the control and drug-treated groups. A substantial increase in the frequency of polysialylated cells in layer II of the entorhinal and perirhinal cortices was also observed, brain regions not previously associated with neurogenesis. Chronic treatment with SB-271046 or SB-399885 also significantly increased the activation of dentate polysialylation that is specific to learning. This effect does not occur with other cognition-enhancing drugs, such as tacrine, and this action potentially differentiates 5-HT(6) receptor antagonism as an unique neuroplastic mechanism for cognitive processes which may slow or reverse age/neurodegenerative related memory deficits.
Asunto(s)
Giro Dentado/efectos de los fármacos , Hipocampo/efectos de los fármacos , Moléculas de Adhesión de Célula Nerviosa/farmacología , Neuronas/metabolismo , Piperazinas/farmacología , Receptores de Serotonina/efectos de los fármacos , Antagonistas de la Serotonina/farmacología , Ácidos Siálicos/farmacología , Sulfonamidas/farmacología , Tiofenos/farmacología , Animales , Antimetabolitos , Bromodesoxiuridina , Proliferación Celular/efectos de los fármacos , Gránulos Citoplasmáticos/efectos de los fármacos , Gránulos Citoplasmáticos/metabolismo , Giro Dentado/citología , Relación Dosis-Respuesta a Droga , Corteza Entorrinal/citología , Corteza Entorrinal/efectos de los fármacos , Hipocampo/citología , Inmunohistoquímica , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Neuronas/efectos de los fármacos , Ratas , Ratas WistarRESUMEN
Recent evidence has suggested a role for Notch in memory consolidation but the means by which this evolutionarily conserved mechanism serves these plasticity-related processes remains to be established. We have examined a role for this signalling pathway in the hippocampal dentate gyrus of Wistar rats at increasing times following passive avoidance conditioning. Our principal finding is that a transient attenuation of Notch signalling occurs at the 10-12h post-training time. In this period, extracellular Notch-1 protein fragment exhibited a significant 2- to 3-fold increase but, by contrast, Notch-1 mRNA levels were significantly reduced. Moreover, transient inactivation of Notch-1 signalling was further suggested by concomitant reductions in the Notch ligand Jagged-1 and Notch-1 target protein Hes-1 mRNA levels. The C-terminal fragment of PS-1, necessary for gamma-secretase activity, was also significantly reduced at the 12h post-training time. These events were commensurate with the increase of a Notch immunoreactive fragment of 66 kDa in the nuclear fraction of the dentate gyrus. This fragment, identified with two different Notch-1 antisera, was not the expected NICD polypeptide of approximately 110 kDa and its accumulation was found to correlate with a significantly reduced expression of the Hes-1 transcriptional repressor. During the period of reduced Notch activity, a transient increase in soluble beta-catenin and GSK-3beta phosphorylation was observed, indicating a reciprocal activation of the Wnt signalling pathway. As down-regulation of Notch signalling promotes differentiation and neurite outgrowth in post-mitotic neurons, it is proposed that this pathway regulates the integration of synapses transiently produced during memory consolidation.
Asunto(s)
Reacción de Prevención/fisiología , Giro Dentado/metabolismo , Memoria/fisiología , Presenilina-1/metabolismo , Receptor Notch1/metabolismo , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Análisis de Varianza , Animales , Líquido Extracelular/metabolismo , Regulación de la Expresión Génica/fisiología , Masculino , Plasticidad Neuronal/fisiología , ARN Mensajero/análisis , Ratas , Ratas Wistar , Receptor Notch1/genética , Transducción de Señal/fisiología , Estadísticas no Paramétricas , Factores de TiempoRESUMEN
6-[(3-Cyclobutyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-yl)oxy]-N-methyl-3-pyridinecarboxamide hydrochloride (GSK189254) is a novel histamine H(3) receptor antagonist with high affinity for human (pK(i) = 9.59 -9.90) and rat (pK(i) = 8.51-9.17) H(3) receptors. GSK189254 is >10,000-fold selective for human H(3) receptors versus other targets tested, and it exhibited potent functional antagonism (pA(2) = 9.06 versus agonist-induced changes in cAMP) and inverse agonism [pIC(50) = 8.20 versus basal guanosine 5'-O-(3-[(35)S]thio)triphosphate binding] at the human recombinant H(3) receptor. In vitro autoradiography demonstrated specific [(3)H]GSK189254 binding in rat and human brain areas, including cortex and hippocampus. In addition, dense H(3) binding was detected in medial temporal cortex samples from severe cases of Alzheimer's disease, suggesting for the first time that H(3) receptors are preserved in late-stage disease. After oral administration, GSK189254 inhibited cortical ex vivo R-(-)-alpha-methyl[imidazole-2,5(n)-(3)H]histamine dihydrochloride ([(3)H]R-alpha-methylhistamine) binding (ED(50) = 0.17 mg/kg) and increased c-Fos immunoreactivity in prefrontal and somatosensory cortex (3 mg/kg). Microdialysis studies demonstrated that GSK189254 (0.3-3 mg/kg p.o.) increased the release of acetylcholine, noradrenaline, and dopamine in the anterior cingulate cortex and acetylcholine in the dorsal hippocampus. Functional antagonism of central H(3) receptors was demonstrated by blockade of R-alpha-methylhistamine-induced dipsogenia in rats (ID(50) = 0.03 mg/kg p.o.). GSK189254 significantly improved performance of rats in diverse cognition paradigms, including passive avoidance (1 and 3 mg/kg p.o.), water maze (1 and 3 mg/kg p.o.), object recognition (0.3 and 1 mg/kg p.o.), and attentional set shift (1 mg/kg p.o.). These data suggest that GSK189254 may have therapeutic potential for the symptomatic treatment of dementia in Alzheimer's disease and other cognitive disorders.
Asunto(s)
Benzazepinas/farmacología , Encéfalo/efectos de los fármacos , Antagonistas de los Receptores Histamínicos/farmacología , Niacinamida/análogos & derivados , Nootrópicos/farmacología , Receptores Histamínicos H3/metabolismo , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/fisiopatología , Animales , Benzazepinas/metabolismo , Benzazepinas/farmacocinética , Unión Competitiva , Encéfalo/metabolismo , Encéfalo/patología , Línea Celular , Perros , Agonistas de los Receptores Histamínicos/metabolismo , Agonistas de los Receptores Histamínicos/farmacocinética , Agonistas de los Receptores Histamínicos/farmacología , Antagonistas de los Receptores Histamínicos/metabolismo , Antagonistas de los Receptores Histamínicos/farmacocinética , Humanos , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Ratones , Persona de Mediana Edad , Neurotransmisores/metabolismo , Niacinamida/metabolismo , Niacinamida/farmacocinética , Niacinamida/farmacología , Nootrópicos/metabolismo , Nootrópicos/farmacocinética , Ratas , Ratas Sprague-Dawley , Ratas Wistar , Receptores Histamínicos H3/análisis , Sus scrofaRESUMEN
GSK207040 (5-[(3-cyclobutyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-yl)oxy]-N-methyl-2-pyrazinecarboxamide) and GSK334429 (1-(1-methylethyl)-4-({1-[6-(trifluoromethyl)-3-pyridinyl]-4-piperidinyl}carbonyl)hexahydro-1H-1,4-diazepine) are novel and selective non-imidazole histamine H(3) receptor antagonists from distinct chemical series with high affinity for human (pK(i)=9.67+/-0.06 and 9.49+/-0.09, respectively) and rat (pK(i)=9.08+/-0.16 and 9.12+/-0.14, respectively) H(3) receptors expressed in cerebral cortex. At the human recombinant H(3) receptor, GSK207040 and GSK334429 were potent functional antagonists (pA(2)=9.26+/-0.04 and 8.84+/-0.04, respectively versus H(3) agonist-induced changes in cAMP) and exhibited inverse agonist properties (pIC(50)=9.20+/-0.36 and 8.59+/-0.04 versus basal GTPgammaS binding). Following oral administration, GSK207040 and GSK334429 potently inhibited cortical ex vivo [(3)H]-R-alpha-methylhistamine binding (ED(50)=0.03 and 0.35 mg/kg, respectively). Functional antagonism of central H(3) receptors was demonstrated by blockade of R-alpha-methylhistamine-induced dipsogenia in rats (ID(50)=0.02 and 0.11 mg/kg p.o. for GSK207040 and GSK334429, respectively). In more pathophysiologically relevant pharmacodynamic models, GSK207040 (0.1, 0.3, 1 and 3mg/kg p.o.) and GSK334429 (0.3, 1 and 3mg/kg p.o.) significantly reversed amnesia induced by the cholinergic antagonist scopolamine in a passive avoidance paradigm. In addition, GSK207040 (0.1, 0.3 and 1mg/kg p.o.) and GSK334429 (3 and 10mg/kg p.o.) significantly reversed capsaicin-induced reductions in paw withdrawal threshold, suggesting for the first time that blockade of H(3) receptors may be able to reduce tactile allodynia. Novel H(3) receptor antagonists such as GSK207040 and GSK334429 may therefore have therapeutic potential not only in dementia but also in neuropathic pain.
Asunto(s)
Azepinas/uso terapéutico , Benzazepinas/uso terapéutico , Capsaicina , Antagonistas de los Receptores Histamínicos/uso terapéutico , Trastornos de la Memoria/tratamiento farmacológico , Neuralgia/tratamiento farmacológico , Pirazinas/uso terapéutico , Piridinas/uso terapéutico , Receptores Histamínicos H3/metabolismo , Escopolamina , Analgésicos/farmacocinética , Analgésicos/farmacología , Analgésicos/uso terapéutico , Animales , Reacción de Prevención/efectos de los fármacos , Azepinas/administración & dosificación , Azepinas/farmacocinética , Benzazepinas/farmacocinética , Benzazepinas/farmacología , Sistema Nervioso Central/efectos de los fármacos , Ingestión de Líquidos/efectos de los fármacos , Agonistas de los Receptores Histamínicos/farmacocinética , Agonistas de los Receptores Histamínicos/farmacología , Antagonistas de los Receptores Histamínicos/farmacocinética , Antagonistas de los Receptores Histamínicos/farmacología , Humanos , Masculino , Trastornos de la Memoria/inducido químicamente , Neuralgia/inducido químicamente , Pirazinas/farmacocinética , Pirazinas/farmacología , Piridinas/administración & dosificación , Piridinas/farmacocinética , Ratas , Ratas Sprague-DawleyRESUMEN
A learning event initiates a cascade of altered gene expression leading to synaptic remodelling within the hippocampal dentate gyrus, a structure vital to memory formation. To illuminate this transcriptional program of synaptic plasticity we used microarrays to quantify mRNA from the rat dentate gyrus at increasing times following passive avoidance learning. Approximately, 500 known genes were transcriptionally regulated across the 24 h post-training period. The 0-2 h period saw up-regulation of genes involved in transcription while genes with a role in synaptic/cytoskeletal structure increased 0-6 h, consistent with structural rearrangements known to occur at these times. The most striking feature was the profound down-regulation, across all functional groups, 12 h post-training. Bioinformatics analysis identified the likely transcription factors controlling gene expression in each post-training period. The role of NF kappa B, implicated in the early post-training period was subsequently confirmed with activation and nuclear translocation seen in dentate granule neurons following training. mRNA changes for four genes, LRP3 (0 h), alpha actin (3 h), SNAP25 and NSF (6-12 h), were validated at message and/or protein level and shown to be learning specific. Thus, the memory-associated transcriptional cascade supports the cardinal periods of synaptic loosening, reorganisation and selection thought to underpin the process of long-term memory consolidation in the hippocampus.
Asunto(s)
Reacción de Prevención/fisiología , Giro Dentado/metabolismo , Regulación de la Expresión Génica/fisiología , Animales , Conducta Animal , Western Blotting , Biología Computacional/métodos , Giro Dentado/citología , Masculino , Análisis por Micromatrices/métodos , Modelos Biológicos , Neuronas/metabolismo , Ratas , Ratas Wistar , Tiempo de Reacción/fisiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , Factores de TiempoRESUMEN
SB-399885 (N-[3,5-dichloro-2-(methoxy)phenyl]-4-(methoxy)-3-(1-piperazinyl)benzenesulfonamide) has high affinity for human recombinant and native 5-HT(6) receptors, with pK(i) values 9.11+/-0.03 and 9.02+/-0.05, respectively and is a potent competitive antagonist (pA(2) 7.85+/-0.04). It displays over 200-fold selectivity for the 5-HT(6) receptor over all other receptors, ion channels and enzymes tested to date. SB-399885 inhibited ex vivo [(125)I]SB-258585 (4-Iodo-N-[4-methoxy-3-(4-methyl-piperazin-1-yl)-phenyl]-benzenesulfonamide) binding with an ED(50) of 2.0+/-0.24 mg/kg p.o. in rats. It had a minimum effective dose of 1 mg/kg p.o. in a rat maximal electroshock seizure threshold test and a long duration of action, overall demonstrating an excellent pharmacokinetic-pharmacodynamic correlation. Repeated administration of this agent (10 mg/kg p.o., b.i.d. for 7 days) significantly reversed a scopolamine-induced deficit (0.5 mg/kg i.p.) in a rat novel object recognition paradigm. Moreover, in aged rats (22 months old) SB-399885 (10 mg/kg p.o., b.i.d. for 7 days) fully reversed the age-dependent deficit in water maze spatial learning compared to vehicle-treated age-matched controls and significantly improved recall of the task measured by increases in the searching of the target quadrant on post-training days 1, 3 and 7. In vivo microdialysis in the rat medial prefrontal cortex demonstrated that acute SB-399885 (10 mg/kg p.o.) significantly increased extracellular acetylcholine levels. These data demonstrate that SB-399885 is a potent, selective, brain penetrant, orally active 5-HT(6) receptor antagonist with cognitive enhancing properties that are likely to be mediated by enhancements of cholinergic function. These studies provide further support for the potential therapeutic utility of 5-HT(6) receptor antagonists in disorders characterised by cognitive deficits such as Alzheimer's disease and schizophrenia.