RESUMEN
Stress is a biologically relevant signal and can modulate hippocampal synaptic plasticity. The subiculum is the major output station of the hippocampus and serves as a critical hub in the stress response network. However, stress-associated synaptic plasticity in the ventral subiculum has not been adequately addressed. Therefore, we investigated the impact of a single exposure to an inherently stressful two-way active avoidance conditioning on the induction of long-term potentiation (LTP) at CA1-subiculum synapses in ventral hippocampal slices from young adult rats 1 day after stressor exposure. We found that acute stress enhanced LTP and lowered the induction threshold for a late-onset LTP at excitatory CA1 to subicular burst-spiking neuron synapses. This late-onset LTP was dependent on the activation of ß-adrenergic and glutamatergic N-methyl-D-aspartate receptors and independent of D1/D5 dopamine receptor activation. Thereby, we present a cellular mechanism that might contribute to behavioral stress adaptation after acute stressor exposure.
RESUMEN
Malformations of cortical development (MCD) represent a group of rare diseases with severe clinical presentation as epileptic and pharmacoresistant encephalopathies. Morphological studies in tissue from MCD patients have revealed reduced GABAergic efficacy and increased intracellular chloride concentration in neuronal cells as important pathophysiological mechanisms in MCD. Also, in various animal models, alterations of GABAergic inhibition have been postulated as a predominant factor contributing to perilesional hyperexcitability. Along with this line, the NKCC1 inhibitor bumetanide has been postulated as a potential drug for treatment of epilepsy, mediating its antiepileptic effect by reduction of the intracellular chloride and increased inhibitory efficacy of GABAergic transmission. In the present study, we focused on the focal freeze-lesion model of MCD to compare antiepileptic drugs with distinct mechanisms of action, including NKCC1 inhibition by bumetanide. For this purpose, we combined electrophysiological and optical methods in slice preparations and assessed the properties of seizure like events (SLE) induced by 4-aminopyridine. In freeze-lesioned but not control slices, SLE onset was confined to the perilesional area, confirming that this region is hyperexcitable and likely triggers pathological activity. Bumetanide selectively reduced epileptic activity in lesion-containing slices but not in slices from sham-treated control rats. Moreover, bumetanide caused a shift in the SLE onset site away from the perilesional area. In contrast, effects of other antiepileptic drugs including carbamazepine, lacosamide, acezatolamide and zonisamide occurred mostly independently of the lesion and did not result in a shift of the onset region. Our work adds evidence for the functional relevance of chloride homeostasis in the pathophysiology of microgyrus formation as represented in the focal freeze-lesion model. Further studies in different MCD models and human tissue will be required to validate the effects across different MCD subtypes and species and to assess the translational value of our findings.
Asunto(s)
Anticonvulsivantes/administración & dosificación , Criocirugía/efectos adversos , Malformaciones del Desarrollo Cortical/tratamiento farmacológico , Malformaciones del Desarrollo Cortical/patología , Convulsiones/tratamiento farmacológico , Convulsiones/patología , 4-Aminopiridina/toxicidad , Animales , Bumetanida/administración & dosificación , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/patología , Masculino , Malformaciones del Desarrollo Cortical/etiología , Técnicas de Cultivo de Órganos , Ratas , Ratas Wistar , Convulsiones/inducido químicamente , Inhibidores del Simportador de Cloruro Sódico y Cloruro Potásico/administración & dosificaciónRESUMEN
A traumatic childhood is among the most important risk factors for developing stress-related psychopathologies such as posttraumatic stress disorder or depression later in life. However, despite the proven role of astrocytes in regulating transmitter release and synaptic plasticity, the contribution of astrocytic transmitter metabolism to such stress-induced psychopathologies is currently not understood. In rodents, childhood adversity can be modeled by juvenile stress exposure, resulting in increased anxiety, and impaired coping with stress in adulthood. We describe that such juvenile stress in rats, regardless of additional stress in adulthood, leads to reduced synaptic efficacy in the ventral CA1 (vCA1) Schaffer collaterals, but increased long-term potentiation (LTP) of synaptic transmission after high-frequency stimulation. We tested whether the glutamate-glutamine-cycle guides the lasting changes on plasticity observed after juvenile stress by blocking the astrocytic glutamate-degrading enzyme, glutamine synthetase (GS). Indeed, the pharmacological inhibition of GS by methionine sulfoximine in slices from naïve rats mimics the effect of juvenile stress on vCA1-LTP, while supplying glutamine is sufficient to normalize the LTP. Assessing steady-state mRNA levels in the vCA1 stratum radiatum reveals distinct shifts in the expression of GS, astrocytic glutamate, and glutamine transporters after stress in juvenility, adulthood, or combined juvenile/adult stress. While GS mRNA expression levels are lastingly reduced after juvenile stress, GS protein levels are maintained stable. Together our results suggest a critical role for astrocytes and the glutamate-glutamine cycle in mediating long-term effects of juvenile stress on plasticity in the vCA1, a region associated with anxiety and emotional memory processing.
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Astrocitos/enzimología , Glutamato-Amoníaco Ligasa/fisiología , Hipocampo/enzimología , Potenciación a Largo Plazo/fisiología , Estrés Psicológico/enzimología , Factores de Edad , Animales , Astrocitos/patología , Hipocampo/patología , Masculino , Técnicas de Cultivo de Órganos , Ratas , Ratas Wistar , Estrés Psicológico/patología , Estrés Psicológico/psicologíaRESUMEN
OBJECTIVE: Blood-brain barrier (BBB) impairment, redistribution of pericytes, and disturbances in cerebral blood flow may contribute to the increased seizure propensity and neurological comorbidities associated with epilepsy. However, despite the growing evidence of postictal disturbances in microcirculation, it is not known how recurrent seizures influence pericytic membrane currents and subsequent vasodilation. METHODS: Here, we investigated successive changes in capillary neurovascular coupling and BBB integrity during recurrent seizures induced by 4-aminopyridine or low-Mg2+ conditions. To avoid the influence of arteriolar dilation and cerebral blood flow changes on the capillary response, we measured seizure-associated pericytic membrane currents, capillary motility, and permeability changes in a brain slice preparation. Arteriolar responses to 4-aminopyridine-induced seizures were further studied in anesthetized Sprague Dawley rats by using electrocorticography and tissue oxygen recordings simultaneously with intravital imaging of arteriolar diameter, BBB permeability, and cellular damage. RESULTS: Within the preserved vascular network in hippocampal slice cultures, pericytes regulated capillary diameter in response to vasoactive agents and neuronal activity. Seizures induced distinct patterns of membrane currents that contributed to the regulation of pericytic length. During the course of recurrent seizures, individual vasodilation responses eroded and BBB permeability increased, despite unaltered neurometabolic coupling. Reduced vascular responsiveness was associated with mitochondrial depolarization in pericytes. Subsequent capillary constriction preceded BBB opening, suggesting that pericyte injury mediates the breach in capillary integrity. In vivo findings were consistent with slice experiments, showing seizure-related neurovascular decoupling and BBB dysfunction in small cortical arterioles, accompanied by perivascular cellular injury despite normoxic conditions. SIGNIFICANCE: Our study presents a direct observation of gradually developing neurovascular decoupling during recurrent seizures and suggests pericytic injury as an inducer of vascular dysfunction in epilepsy.
Asunto(s)
Barrera Hematoencefálica/fisiopatología , Capilares/lesiones , Permeabilidad Capilar/fisiología , Convulsiones/fisiopatología , Animales , Encéfalo/fisiopatología , Capilares/fisiopatología , Circulación Cerebrovascular/fisiología , Neuronas/fisiología , Acoplamiento Neurovascular/fisiología , Ratas Sprague-Dawley , Convulsiones/complicacionesRESUMEN
OBJECTIVE: Epilepsy is a neurological disorder affecting 50 million individuals globally. Modern research has inspected the likelihood of forecasting epileptic seizures. Algorithmic investigations are giving promising results for seizure prediction. Though mostly seizure prediction algorithm uses pre-ictal (prodromal symptoms) events for prediction. On the contrary, prodromal symptoms may not necessarily be present in every patient or subject. This paper focuses on seizure forecasting regardless of the presence of pre-ictal (prodromal symptoms) using the single robust feature with maximum accuracy. Method: We evaluated datasets having 4-aminopydine induced seizure-like events rat's hippocampa slices and cortical tissue from pharmacoresistant epilepsy patients. The proposed methodology applies the Discrete Wavelet Transform (DWT) at levels 1-5 utilizing 'Daubechies-4'. Linear Discriminant classifier (LDC), Quadratic Discriminant Classifier (QDC) and Support Vector Machine (SVM) were used to classify each signal using eight discriminative features. Results: Classifier performance was assessed by parameters like true detections (TD), false detection (FD), accuracy (ACC), sensitivity (SEN), specificity (SPF), and positive predicted value (PPC), negative predicted value (NPV). Highest classification feature was selected as a seizure forecasting correlation vector and decision rule was formulated for seizure forecasting. Correlation vector served as a forecaster for current EEG activity. Proposed decision rule forecasted ongoing signal activity towards possible seizure condition true or false. The suggested framework revealed forecasting of ictal events at 10 seconds before the actual seizure. Conclusion: It is worth mentioning that the proposed study utilized a single linear feature to predict seizures precisely. Moreover, utilization of single feature encouraged in subsiding system complexity, processing delays, and system latency.
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Electroencefalografía/métodos , Epilepsia/fisiopatología , Convulsiones/fisiopatología , Máquina de Vectores de Soporte , Animales , Corteza Cerebral/fisiopatología , Modelos Animales de Enfermedad , Epilepsia Refractaria/fisiopatología , Epilepsia/diagnóstico , Predicción , Humanos , Ratas , Convulsiones/diagnósticoRESUMEN
Human mesial temporal lobe epilepsy (MTLE) features subregion-specific hippocampal neurodegeneration and reactive astrogliosis, including up-regulation of the glial fibrillary acidic protein (GFAP) and down-regulation of glutamine synthetase (GS). However, the regional astrocytic expression pattern of GFAP and GS upon MTLE-associated neurodegeneration still remains elusive. We assessed GFAP and GS expression in strict correlation with the local neuronal number in cortical and hippocampal surgical specimens from 16 MTLE patients using immunohistochemistry, stereology and high-resolution image analysis for digital pathology and whole-slide imaging. In the cortex, GS-positive (GS+) astrocytes are dominant in all neuronal layers, with a neuron to GS+ cell ratio of 2:1. GFAP-positive (GFAP+) cells are widely spaced, with a GS+ to GFAP+ cell ratio of 3:1-5:1. White matter astrocytes, on the contrary, express mainly GFAP and, to a lesser extent, GS. In the hippocampus, the neuron to GS+ cell ratio is approximately 1:1. Hippocampal degeneration is associated with a reduction of GS+ astrocytes, which is proportional to the degree of neuronal loss and primarily present in the hilus. Up-regulation of GFAP as a classical hallmark of reactive astrogliosis does not follow the GS-pattern and is prominent in the CA1. Reactive alterations were proportional to the neuronal loss in the neuronal somatic layers (stratum pyramidale and hilus), while observed to a lesser extent in the axonal/dendritic layers (stratum radiatum, molecular layer). We conclude that astrocytic GS is expressed in the neuronal somatic layers and, upon neurodegeneration, is down-regulated proportionally to the degree of neuronal loss.
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Astrocitos/enzimología , Corteza Cerebral/enzimología , Epilepsia del Lóbulo Temporal/enzimología , Glutamato-Amoníaco Ligasa/metabolismo , Neuronas/enzimología , Adulto , Astrocitos/patología , Muerte Celular/fisiología , Corteza Cerebral/patología , Epilepsia Refractaria/enzimología , Epilepsia Refractaria/patología , Epilepsia Refractaria/cirugía , Epilepsia del Lóbulo Temporal/patología , Epilepsia del Lóbulo Temporal/cirugía , Femenino , Proteína Ácida Fibrilar de la Glía/metabolismo , Gliosis/enzimología , Gliosis/patología , Humanos , Inmunohistoquímica , Masculino , Enfermedades Neurodegenerativas/enzimología , Enfermedades Neurodegenerativas/patología , Neuronas/patología , Sustancia Blanca/enzimología , Sustancia Blanca/patologíaRESUMEN
In vitro preparations are a powerful tool to explore the mechanisms and processes underlying epileptogenesis and ictogenesis. In this review, we critically review the numerous in vitro methodologies utilized in epilepsy research. We provide support for the inclusion of detailed descriptions of techniques, including often ignored parameters with unpredictable yet significant effects on study reproducibility and outcomes. In addition, we explore how recent developments in brain slice preparation relate to their use as models of epileptic activity.
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Ondas Encefálicas/fisiología , Encéfalo/fisiopatología , Epilepsia/patología , Técnicas In Vitro , Comités Consultivos , Animales , Modelos Animales de Enfermedad , Femenino , Técnicas In Vitro/instrumentación , Técnicas In Vitro/métodos , Técnicas In Vitro/normas , Masculino , Técnicas de Cultivo de Órganos/métodos , Técnicas de Cultivo de Órganos/normasRESUMEN
Neuronal injury due to seizures may result from a mismatch of energy demand and adenosine triphosphate (ATP) synthesis. However, ATP demand and oxygen consumption rates have not been accurately determined, yet, for different patterns of epileptic activity, such as interictal and ictal events. We studied interictal-like and seizure-like epileptiform activity induced by the GABAA antagonist bicuculline alone, and with co-application of the M-current blocker XE-991, in rat hippocampal slices. Metabolic changes were investigated based on recording partial oxygen pressure, extracellular potassium concentration, and intracellular flavine adenine dinucleotide (FAD) redox potential. Recorded data were used to calculate oxygen consumption and relative ATP consumption rates, cellular ATP depletion, and changes in FAD/FADH2 ratio by applying a reactive-diffusion and a two compartment metabolic model. Oxygen-consumption rates were ca. five times higher during seizure activity than interictal activity. Additionally, ATP consumption was higher during seizure activity (~94% above control) than interictal activity (~15% above control). Modeling of FAD transients based on partial pressure of oxygen recordings confirmed increased energy demand during both seizure and interictal activity and predicted actual FAD autofluorescence recordings, thereby validating the model. Quantifying metabolic alterations during epileptiform activity has translational relevance as it may help to understand the contribution of energy supply and demand mismatches to seizure-induced injury.
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Potenciales de Acción/fisiología , Consumo de Oxígeno/fisiología , Convulsiones/metabolismo , Potenciales de Acción/efectos de los fármacos , Adenosina Trifosfato/metabolismo , Animales , Antracenos/farmacología , Bicuculina/farmacología , Electrofisiología , Flavina-Adenina Dinucleótido/metabolismo , Masculino , Consumo de Oxígeno/efectos de los fármacos , Ratas , Ratas WistarRESUMEN
Brain damage due to stroke or traumatic brain injury (TBI), both leading causes of serious long-term disability, often leads to the development of epilepsy. Patients who develop post-injury epilepsy tend to have poor functional outcomes. Emerging evidence highlights a potential role for blood-brain barrier (BBB) dysfunction in the development of post-injury epilepsy. However, common mechanisms underlying the pathological hyperexcitability are largely unknown. Here, we show that comparative transcriptome analyses predict remodeling of extracellular matrix (ECM) as a common response to different types of injuries. ECM-related transcriptional changes were induced by the serum protein albumin via TGFß signaling in primary astrocytes. In accordance with transcriptional responses, we found persistent degradation of protective ECM structures called perineuronal nets (PNNs) around fast-spiking inhibitory interneurons, in a rat model of TBI as well as in brains of human epileptic patients. Exposure of a naïve brain to albumin was sufficient to induce the transcriptional and translational upregulation of molecules related to ECM remodeling and the persistent breakdown of PNNs around fast-spiking inhibitory interneurons, which was contingent on TGFß signaling activation. Our findings provide insights on how albumin extravasation that occurs upon BBB dysfunction in various brain injuries can predispose neural circuitry to the development of chronic inhibition deficits.
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Matriz Extracelular/metabolismo , Expresión Génica , Neuronas/metabolismo , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Astrocitos/metabolismo , Barrera Hematoencefálica/metabolismo , Lesiones Traumáticas del Encéfalo/etiología , Lesiones Traumáticas del Encéfalo/metabolismo , Lesiones Traumáticas del Encéfalo/patología , Corteza Cerebral/metabolismo , Corteza Cerebral/patología , Biología Computacional/métodos , Matriz Extracelular/genética , Perfilación de la Expresión Génica , Hipocampo/metabolismo , Hipocampo/patología , Humanos , Inflamación/genética , Inflamación/metabolismo , Inflamación/patología , Interneuronas/metabolismo , Losartán/farmacología , Receptor Tipo I de Factor de Crecimiento Transformador beta/metabolismo , Activación Transcripcional , TranscriptomaRESUMEN
Neuronal lactate uptake supports energy metabolism associated with synaptic signaling and recovery of extracellular ion gradients following neuronal activation. Altered expression of the monocarboxylate transporters (MCT) in temporal lobe epilepsy (TLE) hampers lactate removal into the bloodstream. The resulting increase in parenchymal lactate levels might exert both, anti- and pro-ictogen effects, by causing acidosis and by supplementing energy metabolism, respectively. Hence, we assessed the contribution of lactate to the maintenance of transmembrane potassium gradients, synaptic signaling and pathological network activity in chronic epileptic human tissue. Stimulus induced and spontaneous field potentials and extracellular potassium concentration changes (∆[Kâº]O) were recorded in parallel with tissue pO2 and pH in slices from TLE patients while blocking MCTs by α-cyano-4-hydroxycinnamic acid (4-CIN) or d-lactate. Intrinsic lactate contributed to the oxidative energy metabolism in chronic epileptic tissue as revealed by the changes in pO2 following blockade of lactate uptake. However, unlike the results in rat hippocampus, ∆[Kâº]O recovery kinetics and field potential amplitude did not depend on the presence of lactate. Remarkably, inhibition of lactate uptake exerted pH-independent anti-seizure effects both in healthy rat and chronic epileptic tissue and this effect was partly mediated via adenosine 1 receptor activation following decreased oxidative metabolism.
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Potenciales de Acción , Corteza Entorrinal/metabolismo , Epilepsia del Lóbulo Temporal/metabolismo , Ácido Láctico/metabolismo , Neocórtex/metabolismo , Animales , Corteza Entorrinal/fisiopatología , Epilepsia del Lóbulo Temporal/fisiopatología , Humanos , Neocórtex/fisiopatología , Potasio/metabolismo , Ratas , Ratas WistarRESUMEN
ALBRECHT, A., MÜLLER, I., ARDI, Z., ÇALISKAN, G., GRUBER, D., IVENS, S., SEGAL, M., BEHR, J., HEINEMANN, U., STORK, O., and RICHTER-LEVIN, G. Neurobiological consequences of juvenile stress: A GABAergic perspective on risk and resilience. NEUROSCI BIOBEHAV REV XXX-XXX, 2016.- Childhood adversity is among the most potent risk factors for developing mood and anxiety disorders later in life. Therefore, understanding how stress during childhood shapes and rewires the brain may optimize preventive and therapeutic strategies for these disorders. To this end, animal models of stress exposure in rodents during their post-weaning and pre-pubertal life phase have been developed. Such 'juvenile stress' has a long-lasting impact on mood and anxiety-like behavior and on stress coping in adulthood, accompanied by alterations of the GABAergic system within core regions for the stress processing such as the amygdala, prefrontal cortex and hippocampus. While many regionally diverse molecular and electrophysiological changes are observed, not all of them correlate with juvenile stress-induced behavioral disturbances. It rather seems that certain juvenile stress-induced alterations reflect the system's attempts to maintain homeostasis and thus promote stress resilience. Analysis tools such as individual behavioral profiling may allow the association of behavioral and neurobiological alterations more clearly and the dissection of alterations related to the pathology from those related to resilience.
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Estrés Psicológico , Adolescente , Envejecimiento , Animales , Ansiedad , Conducta Animal , HumanosRESUMEN
Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy supply-demand mismatch in viable tissue. Spreading depolarizations exacerbate neuronal injury through prolonged ionic breakdown and spreading depolarization-related hypoperfusion (spreading ischemia). Local duration of the depolarization indicates local tissue energy status and risk of injury. Regional electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can be recognized and quantified. Here, we describe the experimental basis for interpreting these patterns and illustrate their translation to human disease. We further provide consensus recommendations for electrocorticographic methods to record, classify, and score spreading depolarizations and associated spreading depressions. These methods offer distinct advantages over other neuromonitoring modalities and allow for future refinement through less invasive and more automated approaches.
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Lesiones Encefálicas/fisiopatología , Depresión de Propagación Cortical/fisiología , Cuidados Críticos/métodos , Sustancia Gris/fisiopatología , Monitorización Neurofisiológica/métodos , Accidente Cerebrovascular/fisiopatología , Lesiones Encefálicas/diagnóstico , Lesiones Encefálicas/terapia , Circulación Cerebrovascular , Electrocorticografía , Humanos , Guías de Práctica Clínica como Asunto , Accidente Cerebrovascular/diagnóstico , Accidente Cerebrovascular/terapiaRESUMEN
Peri-infarct opening of the blood-brain barrier may be associated with spreading depolarizations, seizures, and epileptogenesis as well as cognitive dysfunction. We aimed to investigate the mechanisms underlying neural network pathophysiology in the blood-brain barrier-dysfunctional hippocampus. Photothrombotic stroke within the rat neocortex was associated with increased intracranial pressure, vasogenic edema, and peri-ischemic blood-brain barrier dysfunction that included the ipsilateral hippocampus. Intrahippocampal recordings revealed electrographic seizures within the first week in two-thirds of animals, accompanied by a reduction in gamma and increase in theta frequency bands. Synaptic interactions were studied in parasagittal hippocampal slices at 24 h and seven days post-stroke. Field potential recordings in CA1 and CA3 uncovered multiple population spikes, epileptiform episodes, and spreading depolarizations at 24 h. Input-output analysis revealed that fEPSP-spike coupling was significantly enhanced at seven days. In addition, CA1 feedback and feedforward inhibition were diminished. Slices generating epileptiform activity at seven days revealed impaired bidirectional long-term plasticity following high and low-frequency stimulation protocols. Microarray and PCR data confirmed changes in expression of astrocyte-related genes and suggested downregulation in expression of GABAA-receptor subunits. We conclude that blood-brain barrier dysfunction in the peri-infarct hippocampus is associated with early disinhibition, hyperexcitability, and abnormal synaptic plasticity.
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Barrera Hematoencefálica/fisiopatología , Infarto Encefálico/fisiopatología , Depresión de Propagación Cortical/fisiología , Epilepsia/fisiopatología , Hipocampo/fisiopatología , Plasticidad Neuronal/fisiología , Receptores de GABA-A/metabolismo , Animales , Barrera Hematoencefálica/diagnóstico por imagen , Barrera Hematoencefálica/metabolismo , Barrera Hematoencefálica/patología , Infarto Encefálico/diagnóstico por imagen , Infarto Encefálico/metabolismo , Infarto Encefálico/patología , Regulación hacia Abajo , Epilepsia/metabolismo , Hipocampo/diagnóstico por imagen , Hipocampo/metabolismo , Hipocampo/patología , Presión Intracraneal/fisiología , Imagen por Resonancia Magnética , Masculino , Red Nerviosa/fisiopatología , Ratas Wistar , Receptores de GABA-A/genéticaRESUMEN
Learning is facilitated when information can be incorporated into an already learned set of rules or 'mental schema'. The location of a new restaurant, for example, is learned more easily if the neighbourhood's general layout is already known. This type of information is processed by the hippocampus and stored as a schema in the cortex, but it is not known whether the hippocampus can also map new stimuli to cortical schemata that are hippocampus-independent, such as odour classification. Using a hippocampus-independent odour-rule task we found that animals without a functional hippocampus learnt which odours did not fit the rule faster than sham animals, which persistently applied the rule to all odours. Conversely, when non-fitting odours were linked to a new rule sham animals were faster to link these odours to the new rule. The hippocampus, thus, regulates the association of stimuli with existing schemata even when the schemata are hippocampus-independent. © 2016 Wiley Periodicals, Inc.
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Anticipación Psicológica/fisiología , Asociación , Generalización Psicológica/fisiología , Hipocampo/fisiología , Inhibición Psicológica , Aprendizaje Inverso/fisiología , Animales , Hipocampo/efectos de los fármacos , Hipocampo/patología , Ácido Iboténico/toxicidad , Masculino , Memoria/fisiología , Actividad Motora/fisiología , Pruebas Neuropsicológicas , Percepción Olfatoria/fisiología , RatasRESUMEN
Norepinephrine, is involved in the enhancement of learning and memory formation by regulating synaptic mechanisms through its ability to activate pre- and post-synaptic adrenergic receptors. Here we show that ß-agonists of norepinephrine facilitate the induction of both associational LTP and sharp wave ripples (SPW-Rs) in acute slices of rat hippocampus in area CA3. Surprisingly, this facilitating effect persists when slices are only pretreated with ß-receptor agonists followed by wash out and application of the unspecific ß-adrenoreceptor (ßAR) antagonist propranolol. During application of ßAR agonists repeated stimulation resulted in facilitated induction of SPW-Rs. Since SPW-Rs are thought to be involved in memory replay we studied the effects of ßAR-agonists on spontaneous SPW-Rs in murine hippocampus and found that amplitude and incidence of SPW-Rs increased. These effects involve cyclic-AMP and the activation of protein kinase A and suggest a supportive role in memory consolidation. © 2016 Wiley Periodicals, Inc.
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Agonistas Adrenérgicos beta/farmacología , Región CA3 Hipocampal/efectos de los fármacos , Potenciación a Largo Plazo/efectos de los fármacos , Antagonistas Adrenérgicos beta/farmacología , Animales , Ondas Encefálicas/efectos de los fármacos , Ondas Encefálicas/fisiología , Región CA1 Hipocampal/efectos de los fármacos , Región CA1 Hipocampal/fisiología , Región CA3 Hipocampal/fisiología , Isoproterenol/farmacología , Potenciación a Largo Plazo/fisiología , Ratones Endogámicos C57BL , Propranolol/farmacología , Ratas Wistar , Receptores Adrenérgicos beta/metabolismo , Técnicas de Cultivo de TejidosRESUMEN
Astrocyte-derived lactate supports pathologically enhanced neuronal metabolism, but its role under physiological conditions is still a matter of debate. Here, we determined the contribution of astrocytic neuronal lactate shuttle for maintenance of ion homeostasis and energy metabolism. We tested for the effects of α-cyano-4-hydroxycinnamic acid (4-CIN), which could interfere with energy metabolism by blocking monocarboxylate-transporter 2 (MCT2)-mediated neuronal lactate uptake, on evoked potentials, stimulus-induced changes in K+, Na+, Ca2+, and oxygen concentrations as well as on changes in flavin adenine dinucleotide (FAD) autofluorescence in the hippocampal area CA3. MCT2 blockade by 4-CIN reduced synaptically evoked but not antidromic population spikes. This effect was dependent on the activation of KATP channels indicating reduced neuronal ATP synthesis. By contrast, lactate receptor activation by 3,5-dihydroxybenzoic acid (3,5-DHBA) resulted in increased antidromic and orthodromic population spikes suggesting that 4-CIN effects are not mediated by lactate accumulation and subsequent activation of lactate receptors. Recovery kinetics of all ion transients were prolonged and baseline K+ concentration became elevated by blockade of lactate uptake. Lactate contributed to oxidative metabolism as both baseline respiration and stimulus-induced changes in Po2 were decreased, while FAD fluorescence increased likely due to a reduced conversion of FAD into FADH2 These data suggest that lactate shuttle contributes to regulation of ion homeostatsis and synaptic signaling even in the presence of ample glucose.
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Región CA3 Hipocampal/metabolismo , Metabolismo Energético/fisiología , Líquido Extracelular/fisiología , Ácido Láctico/metabolismo , Neuronas/metabolismo , Animales , Región CA3 Hipocampal/efectos de los fármacos , Ácidos Cumáricos/farmacología , Metabolismo Energético/efectos de los fármacos , Líquido Extracelular/efectos de los fármacos , Hidroxibenzoatos/farmacología , Ácido Láctico/antagonistas & inhibidores , Masculino , Neuronas/efectos de los fármacos , Técnicas de Cultivo de Órganos , Ratas , Ratas Wistar , Resorcinoles/farmacologíaRESUMEN
Peripheral biomarkers have myriad potential uses for treatment, prediction, prognostication, and pharmacovigilance in epilepsy. To date, no single peripheral biomarker has demonstrated proven effectiveness, although multiple candidates are in development. In this review, we discuss the major areas of focus including inflammation, blood-brain barrier dysfunction, redox alterations, metabolism, hormones and growth factors.
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Biomarcadores/metabolismo , Epilepsia/genética , Epilepsia/metabolismo , Animales , Barrera Hematoencefálica/fisiopatología , Humanos , Inflamación/metabolismo , Péptidos y Proteínas de Señalización Intercelular/genética , Péptidos y Proteínas de Señalización Intercelular/metabolismoRESUMEN
OBJECTIVE: The need for alternative pharmacologic strategies in treatment of epilepsies is pressing for about 30% of patients with epilepsy who do not experience satisfactory seizure control with present treatments. In temporal lobe epilepsy (TLE) even up to 80% of patients are pharmacoresistant, and surgical resection of the ictogenic tissue is only possible for a minority of TLE patients. In this study we investigate purinergic modulation of drug-resistant seizure-like events (SLEs) in human temporal cortex slices. METHODS: Layer V/VI field potentials from a total of 77 neocortical slices from 17 pharmacoresistant patients were recorded to monitor SLEs induced by application of 8 mM [K(+) ] and 50 µm bicuculline. RESULTS: Activating A1 receptors with a specific agonist completely suppressed SLEs in 73% of human temporal cortex slices. In the remaining slices, incidence of SLEs was markedly reduced. Because a subportion of slices can be pharmacosensitive, we tested effects of an A1 agonist, in slices insensitive to a high dose of carbamazepine (50 µm). Also in these cases the A1 agonist was equally efficient. Moreover, ATP and adenosine blocked or modulated SLEs, an effect mediated not by P2 receptors but rather by adenosine A1 receptors. SIGNIFICANCE: Selective activation of A1 receptors mediates a strong anticonvulsant action in human neocortical slices from pharmacoresistant patients. We propose that our human slice model of seizure-like activity is a feasible option for future studies investigating new antiepileptic drug (AED) candidates.
Asunto(s)
Epilepsia Refractaria/patología , Neocórtex/efectos de los fármacos , Neocórtex/metabolismo , Receptores Purinérgicos P1/metabolismo , Adenosina/análogos & derivados , Adenosina/farmacología , Adenosina Trifosfato/farmacología , Adulto , Bicuculina/análogos & derivados , Bicuculina/farmacología , Carbamazepina/efectos adversos , Carbamazepina/farmacología , Epilepsia Refractaria/tratamiento farmacológico , Estimulación Eléctrica , Potenciales Evocados/efectos de los fármacos , Femenino , Humanos , Técnicas In Vitro , Masculino , Persona de Mediana Edad , Potasio/farmacología , Purinérgicos/farmacología , Factores de Tiempo , Adulto JovenRESUMEN
Epileptogenesis following insults to the brain may be triggered by a dysfunctional blood-brain barrier (BBB) associated with albumin extravasation and activation of astrocytes. Using ex vivo recordings from the BBB-disrupted hippocampus after neocortical photothrombotic stroke, we previously demonstrated abnormal activity-dependent accumulation of extracellular potassium with facilitated generation of seizure like events and spreading depolarizations. Similar changes could be observed after intracerebroventricular (icv) application of albumin. We hypothesized that alterations in extracellular potassium and glutamate homeostasis might lead to alterations in synaptic interactions. We therefore assessed the effects of icv albumin on homo- and heterosynaptic plasticity in hippocampal CA1, 24h after a single injection or 7days after continuous infusion of icv albumin. We demonstrate alterations in both homo- and heterosynaptic plasticity compared to control conditions in ex vivo slice studies. Albumin-treated tissue reveals (1) reduced long-term depression following low-frequency stimulation; (2) increased long-term potentiation of population spikes in response to 20Hz stimulation; (3) potentiated responses to Schaffer collateral stimulation following high-frequency stimulation of the direct cortical input and low-frequency stimulation of alveus and finally, (4) TGFß receptor II (TGFßR-II) involvement in albumin-induced homosynaptic plasticity changes. We conclude that albumin-induced network hyperexcitability is associated with abnormal homo- and heterosynaptic plasticity that could partly be reversed by interference with TGFßR-II-mediated signaling and therefore it might be an important factor in the process of epileptogenesis.
Asunto(s)
Albúminas/farmacología , Barrera Hematoencefálica/efectos de los fármacos , Región CA1 Hipocampal/efectos de los fármacos , Potenciación a Largo Plazo/efectos de los fármacos , Plasticidad Neuronal/efectos de los fármacos , Albúminas/administración & dosificación , Animales , Astrocitos/efectos de los fármacos , Barrera Hematoencefálica/fisiopatología , Región CA1 Hipocampal/citología , Inyecciones Intraventriculares , Potenciación a Largo Plazo/fisiología , Masculino , Plasticidad Neuronal/fisiología , Neuronas/efectos de los fármacos , Neuronas/fisiología , Ratas WistarRESUMEN
Action potentials represent the output of a neuron. Especially interneurons display a variety of discharge patterns ranging from regular action potential firing to prominent spike clustering or stuttering. The mechanisms underlying this heterogeneity remain incompletely understood. We established hierarchical cluster analysis of spike trains as a measure of spike clustering. A clustering index was calculated from action potential trains recorded in the whole-cell patch clamp configuration from hippocampal (CA1, stratum radiatum) and entorhinal (medial entorhinal cortex, layer 2) interneurons in acute slices and simulated data. Prominent, region-dependent, but also variable spike clustering was detected using this measure. Further analysis revealed a strong positive correlation between spike clustering and membrane potentials oscillations but an inverse correlation with neuronal resonance. Furthermore, clustering was more pronounced when the balance between fast-activating K(+) currents, assessed by the spike repolarisation time, and hyperpolarization-activated currents, gauged by the size of the sag potential, was shifted in favour of fast K(+) currents. Simulations of spike clustering confirmed that variable ratios of fast K(+) and hyperpolarization-activated currents could underlie different degrees of spike clustering and could thus be crucial for temporally structuring interneuron spike output.