Seizures Induces Hypoxia and Hypoxia Induces Seizures: A Perverse Relationship that Increases the Risk of SUDEP

He uttered a cry and was seen to be rubbing his hands together. His pulse wasimmediately examined for but was not palpable.Hypoxia is a biological stimulus capable of promoting both rescue and survivalmechanisms, as well as triggering a sequence of irreversible events that lead to deathof cell, tissue and even individual. Brain and heart functions depend critically onadequate energy supply and they are highly susceptible to hypoxic conditions.Adequate oxygen supply is needed for the brain and heart to metabolize glucose asits major energy source. But how many type of hypoxia we know, and how muchsevere is the hypoxic condition, when more than one type of hypoxia aresimultaneously acting. Four types of hypoxia are distinguished in medicine: α- thehypoxemic hypoxia, due to a decrease in the amount of breathable oxygen orcardiopulmonary failure, b- the anemic hypoxia related with decreased amount offunctional hemoglobin, c- the stagnant hypoxia, secondary to reduced or unevenlydistributed flow of blood distribution to the tissues, and mainly result from heartdisease that impairs the circulation; and d- the histotoxic hypoxia, in which the tissuecells are poisoned and are therefore unable to make proper use of oxygen.Fil: Auzmendi, Jerónimo Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Lazarowski, Alberto Jorge. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Bioquímica Clínica; Argentin

Early Gabapentin Treatment during the Latency Period Increases Convulsive Threshold, Reduces Microglial Activation and Macrophage Infiltration in the Lithium-Pilocarpine Model of Epilepsy

The lithium-pilocarpine model of epilepsy reproduces several features of temporal lobe epilepsy in humans, including the chronological timeline of an initial latency period followed by the development of spontaneous seizures. Epilepsy therapies in humans are implemented, as a rule, after the onset of the spontaneous seizures. We here studied the potential effect on epileptogenesis of starting an early treatment during the latency period, in order to prevent the development of spontaneous seizures. Adult male Wistar rats were treated with 3 mEq/kg LiCl, and 20 h later 30 mg/kg pilocarpine. Once status epilepticus (SE) was achieved, it was allowed to last for 20 min, and then motor seizures were controlled with the administration of 20 mg/kg diazepam. At 1DPSE (DPSE, days post-status epilepticus), animals started to receive 400 mg/kg/day gabapentin or saline for 4 days. At 5DPSE, we observed that SE induced an early profuse microglial and astroglial reactivity, increased synaptogenic trombospondin-1 expression and reduced AQP4 expression in astroglial ending feet. Blood brain barrier (BBB) integrity seemed to be compromised, as infiltrating NG2+ macrophages and facilitated access to the CNS was observed by transplanting eGFP+ blood cells and bone marrow-derived progenitors in the SE animals. The early 4-day gabapentin treatment successfully reduced microglial cell reactivity and blood-borne cell infiltration, without significantly altering the mRNA of proinflammatory cytokines IL-1β and TNFα immediately after the treatment. After 21DSPE, another group of animals that developed SE and received 4 days of gabapentin treatment, were re-exposed to subconvulsive accumulative doses of pilocarpine (10 mg/kg/30 min) and were followed by recording the Racine scale reached. Early 4-day gabapentin treatment reduced the Racine scale reached by the animals, reduced animal mortality, and reduced the number of animals that achieved SE (34% vs. 72%). We conclude that early gabapentin treatment following SE, during the latency period, is able to reduce neuroinflammation and produces a persistent effect that limits seizures and increases convulsive threshold, probably by restricting microglial reactivity and spurious synaptogenesis.Fil: Rossi, Alicia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia ; ArgentinaFil: Murta, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia ; ArgentinaFil: Auzmendi, Jerónimo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia ; ArgentinaFil: Ramos, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia ; Argentin

Convulsive Stress Mimics Brain Hypoxia and Promotes the P-Glycoprotein (P-gp) and Erythropoietin Receptor Overexpression. Recombinant Human Erythropoietin Effect on P-gp Activity

Erythropoietin (EPO) is not only a hormone that promotes erythropoiesis but also has a neuroprotective effect on neurons attributed to its known anti-apoptotic action. Previously, our group has demonstrated that recombinant-human EPO (rHu-EPO) can protect neurons and recovery motor activity in a chemical focal brain hypoxia model (Merelli et al., 2011). We and others also have reported that repetitive seizures can mimic a hypoxic- like condition by HIF-1α nuclear translocation and high neuronal expression P-gp. Here, we report that a single 20-min status epilepticus (SE) induces P-gp and EPO-R expression in cortical pyramidal neurons and only P-gp expression in astrocytes. In vitro, excitotoxic stress (300 μM glutamate, 5 min), can also induce the expression of EPO-R and P-gp simultaneously with both HIF-1α and NFkB nuclear translocation in primary cortical neurons. Primary astrocytes exposed to chemical hypoxia with CoCl2 (0.3 mM, 6 h) increased P-gp expression as well as an increased efflux of Rhodamine 123 (Rho123) that is a P-gp substrate. Tariquidar, a specific 3er generation P-gp-blocker was used as an efflux inhibitor control. Astrocytes treated with rHu-EPO showed a significant recovery of the Rho123 retention in a similar way as seen by Tariquidar, demonstrating for first time that rHu-EPO can inhibit the P-gp-dependent efflux activity. Taking together, these data suggest that stimulation of EPO depending signaling system could not only play a central role in brain cell protection, but this system could be a new tool for reverse the pharmacoresistant phenotype in refractory epilepsy as well as in other pharmacoresistant hypoxic brain diseases expressing P-gp.Fil: Merelli, Amalia Margarita. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; ArgentinaFil: Ramos, Alberto Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Lazarowski, Alberto Jorge. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; ArgentinaFil: Auzmendi, Jerónimo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentin

Is cannabidiol a drug acting on unconventional targets to control drug-resistant epilepsy

Cannabis has been considered as a therapeutic strategy to control intractable epilepsy. Several cannabis components, especially cannabidiol (CBD), induce antiseizure effects. However, additional information is necessary to identify the types of epilepsies that can be controlled by these components and the mechanisms involved in these effects. This review presents a summary of the discussion carried out during the 2nd Latin American Workshop on Neurobiology of Epilepsy entitled “Cannabinoid and epilepsy: myths and realities.” This event was carried out during the 10th Latin American Epilepsy Congress in San José de Costa Rica (September 28, 2018). The review focuses to discuss the use of CBD as a new therapeutic strategy to control drug-resistant epilepsy. It also indicates the necessity to consider the evaluation of unconventional targets such as P-glycoprotein, to explain the effects of CBD in drug-resistant epilepsy.Fil: Rocha, Luisa. CENTRO DE INVESTIGACIÓN Y DE ESTUDIOS AVANZADOS ; INSTITUTO POLITÉCNICO NACIONAL;Fil: Lizette Frías Soria , Christian. CENTRO DE INVESTIGACIÓN Y DE ESTUDIOS AVANZADOS ; INSTITUTO POLITÉCNICO NACIONAL;Fil: Ortiz, José G.. Universidad de Puerto Rico; Puerto RicoFil: Auzmendi, Jerónimo Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Lazarowski, Alberto. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; Argentin

3-mercaptopropionic acid-induced seizures decrease NR2B expression in Purkinje cells: Cyclopentyladenosine effect

Inhibitory mechanism of cerebellum epileptic activity can be involved depending on the intensity and frequency of seizure convulsions. N-methyl-D-aspartate receptors (NMDARs) play key roles in excitatory synaptic transmission and have been implicated in neurological disorders: in cerebellum, they have specific characteristics. NMDARs are heteromeric complexes, and the expression of functional receptors in mammalian cells requires the subunit NR1 (essential) and one NR2 subtype of the four isoforms: NR2A-NR2D. In mature Purkinje cells, the combination of NR1 with NR2B subunits forms functional NMDARs; NR2B subunit may be altered in exocitotoxic events. Cyclopentyladenosine (CPA), an adenosine analogue, administered to rats, for one or more days, increases seizure threshold induced by the convulsant drug 3-mercaptopropionic acid (MP). In this study, we focused on the expression of NR2B in cerebellum after repetitive seizures induced by MP and the effect of adenosine analogue CPA administered alone or previous to MP (CPA + MP). A significant decrease in NR2B in the whole cerebellum was observed after MP and CPA administration with a tendency to recover to normal values in the combined treatment of CPA administered 30 min before MP by Western blot assay. In immunohistochemical studies, NR2B expression was observed and analysed in Purkinje cells. NR2B expression was decreased after MP (55%) and CPA (12%) administration, and CPA injected 30 min before MP led to 28% reduction in Purkinje cells. These results could be related to Purkinje cell damage or alternatively to avoid the excitotoxic effect. Results recorded after CPA + MP treatment seemed involved in decreasing the convulsant MP effect.Fil: Girardi, Elena Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Auzmendi, Jerónimo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Charó, Nancy Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Gori, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Castro, Marcelo Fidel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentin

Progressive heart P-glycoprotein (P-gp) overexpression after experimental repetitive seizures (ERS) associated with fatal status epilepticus (FSE): Is it related with SUDEP?

Patients with refractory epilepsy (RE) have increased risk of Sudden Unexpected Death in Epilepsy (SUDEP), where acute and fatal heart failure is suspected. High seizure frequency, polypharmacy, changes in dosing, persistent low AED levels or poor adherence to therapy are the greatest risk factors of SUDEP and are also features observed in RE. We evaluated the progressive P-gp overexpression in heart, related with the development of fatal status epilepticus (FSE) after experimental repetitive seizures (ERS). Male Wistar rats (180–230g) were daily injected (i.p) with Pentylenetetrazole (PTZ; 45mg/kg; n=18) or saline (Controls; n=6). Severity of seizures was recorded. Four PTZ-treated rats were sacrificed at 4th-7th day respectively. Ten remaining rats, underwent same treatment until develop fatal status epilepticus (FSE). Brains and hearts were studied by immunofluorecent method for P-glycoptrotein (P-gp) expression. Seizures were observed each day of PTZ treatment, associated with a progressive P-gp overexpression in heart and FSE at 9th day. Using the same PTZ model, we previously demonstrated that progressive brain P-gp overexpression contributes to cell membrane depolarization of hippocampus and neocortex. These are the first evidences showing that ERS induces a simultaneous and progressive P-gp overexpression in brain and heart associated with FSE, and suggests a role for this pattern expression of P-gp as risk factor for death during SE. The simultaneous and spontaneous death of all animals during SE observed only at day 9th, suggest that a higher P-gp overexpression in cardiomyocytes could play a role in SUDEP, however, because it is only a study descriptive, further researches are needed to confirm this hypothesis.Fil: Auzmendi, Jerónimo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Merelli, Amalia Margarita. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Girardi, Elena Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Orozco Suárez, Sandra. Centro Médico Nacional Siglo XXI; MéxicoFil: Rocha Arrieta, Luisa Lilia. Centro de Investigación y de Estudios Avanzados. Departamento de Farmacobiología; MéxicoFil: Lazarowski, Alberto Jorge. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Fundación Investigar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentin

Cannabidiol (Cbd) alters the functionality of neutrophils (pmn). implications in the refractory epilepsy treatment

Cannabidiol (CBD), a lipophilic cannabinoid compound without psychoactive effects, has emerged as adjuvant of anti‐epileptic drugs (AEDs) in the treatment of refractory epilepsy (RE), decreasing the severity and/or frequency of seizures. CBD is considered a multitarget drug that could act throughout the canonical endocannabinoid receptors (CB1‐CB2) or multiple non‐canonical pathways. Despite the fact that the CBD mechanism in RE is still unknown, experiments carried out in our laboratory showed that CBD has an inhibitory role on P‐glycoprotein excretory function, highly related to RE. Since CB2 is expressed mainly in the immune cells, we hypothesized that CBD treatment could alter the activity of polymorphonuclear neutrophils (PMNs) in a similar way that it does with microglia/macrophages and others circulating leukocytes. In vitro, CBD induced PMN cytoplasmatic vacuolization and proapoptotic nuclear condensation, associated with a significantly decreased viability in a concentration‐dependent manner, while low CBD concentration decreased PMN viability in a time‐dependent manner. At a functional level, CBD reduced the chemotaxis and oxygen consumption of PMNs related with superoxide anion production, while the singlet oxygen level was increased suggesting oxidative stress damage. These results are in line with the well-known CBD anti‐inflammatory effect and support a potential immunosuppressor role on PMNs that could promote an eventual defenseless state during chronic treatment with CBD in RE.Fil: Taborda Gómez, Claudia Marcela. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Lairion, Fabiana Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Repetto, Marisa Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Ettcheto, Miren. Universidad de Barcelona; EspañaFil: Merelli, Amalia Margarita. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; ArgentinaFil: Lazarowski, Alberto Jorge. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; ArgentinaFil: Auzmendi, Jerónimo Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Fisiopatología y Bioquímica Clínica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

Detrimental Effects of HMGB-1 Require Microglial-Astroglial Interaction: Implications for the Status Epilepticus -Induced Neuroinflammation

Temporal Lobe Epilepsy (TLE) is the most common form of human epilepsy and available treatments with antiepileptic drugs are not disease-modifying therapies. The neuroinflammation, neuronal death and exacerbated plasticity that occur during the silent period, following the initial precipitating event (IPE), seem to be crucial for epileptogenesis. Damage Associated Molecular Patterns (DAMP) such as HMGB-1, are released early during this period concomitantly with a phenomenon of reactive gliosis and neurodegeneration. Here, using a combination of primary neuronal and glial cell cultures, we show that exposure to HMGB-1 induces dendrite loss and neurodegeneration in a glial-dependent manner. In glial cells, loss of function studies showed that HMGB-1 exposure induces NF-κB activation by engaging a signaling pathway that involves TLR2, TLR4, and RAGE. In the absence of glial cells, HMGB-1 failed to induce neurodegeneration of primary cultured cortical neurons. Moreover, purified astrocytes were unable to fully respond to HMGB-1 with NF-κB activation and required microglial cooperation. In agreement, in vivo HMGB-1 blockage with glycyrrhizin, immediately after pilocarpine-induced status epilepticus (SE), reduced neuronal degeneration, reactive astrogliosis and microgliosis in the long term. We conclude that microglial-astroglial cooperation is required for astrocytes to respond to HMGB-1 and to induce neurodegeneration. Disruption of this HMGB-1 mediated signaling pathway shows beneficial effects by reducing neuroinflammation and neurodegeneration after SE. Thus, early treatment strategies during the latency period aimed at blocking downstream signaling pathways activated by HMGB-1 are likely to have a significant effect in the neuroinflammation and neurodegeneration that are proposed as key factors in epileptogenesis.Fil: Rosciszewski, Gerardo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Cadena, María Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Auzmendi, Jerónimo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Cieri, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Lukin, Jeronimo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Rossi, Alicia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Murta, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Villarreal, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Reines, Analia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; ArgentinaFil: Gomes, Flávia C. A.. Universidade Federal do Rio de Janeiro; BrasilFil: Ramos, Alberto Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentin

Development of technology for study of the quick activation of ion channels

Los canales iónicos son proteínas multiméricas que regulan el pasaje de iones a través de la membrana celular acoplando su funcionamiento a factores externos como el voltaje de membrana y/o presencia de ligandos específicos. Sus dinámicas de cambio de estado pueden ser descriptas cuantitativamente en términos de un proceso de Markov, aleatorio y sin memoria. Las constantes cinéticas de estos procesos pueden ser obtenidas, a partir de resultados experimentales, con la estimación de la máxima verosimilitud (EMV), empleando el algoritmo recursivo de cadenas ocultas de Markov. En el caso particular de los canales activados por ligando se han postulado estados parciales de energía intermedia (FLIP-STATE), para explicar retardos durante la activación del receptor. Para dilucidar si la existencia de estos estados es una propiedad del receptor o de cada una de las subunidades es necesario poder realizar aplicaciones de agonista aún más breves que las del estado de arte (0.2 ms). Por tal motivo en esta tesis se presenta la creación de un método que permite realizar aplicaciones discretas de agonista ultra-rápidas (20 μs), sobre una preparación de outside-out patch clamp, marcando una mejora sustancial de 10- 50 veces comparado con el estado del arte actual y a los dispositivos comerciales, respectivamente. Se analizó el rango de condiciones en el que esta técnica puede s er empleada y se realizaron modificaciones para generar aplicaciones arbitrarias del agonista maximizando la información cinética obtenida por experimento. Por último, se realizó un análisis teórico, bajo la óptica de la estadística Bayesiana, de la respuesta de canales a aplicaciones ultra-cortas de agonista. Empleando esta técnica y método de análisis puede discriminarse entre modelos que ajustan igualmente los datos experimentales