RESUMEN
Ion channels are targets of various antiepileptic drugs. In cerebral presynaptic nerve endings Na(+) and Ca(2+) channels are particularly abundant, as they control neurotransmitter release, including the release of glutamate (Glu), the most concentrated excitatory amino acid neurotransmitter in the brain. Several pre-synaptic channels are implicated in the mechanism of action of the pro-convulsive agent, 4-aminopyridine (4-AP). In the present study the effects of levetiracetam and other established and newer (vinpocetine) anti-epileptic drugs, as well as of the anti-depressant, sertraline on the increase in Ca(2+) induced by 4-AP in hippocampal isolated nerve endings were investigated. Also the effects of some of the anti-seizure drugs on the selective increase in Ca(2+) induced by high K(+), or on the selective increase in Na(+) induced by veratridine were tested. Sertraline and vinpocetine effectively inhibited the rise in Ca(2+) induced by 4-AP, which was dependent on the out-in Na(+) gradient and tetrodotoxin sensitive. Carbamazepine, phenytoin, lamotrigine and oxcarbazepine inhibited the rise in Ca(2+) induced by 4-AP too, but at higher concentrations than sertraline and vinpocetine, whereas levetiracetam, valproic acid and topiramate did not. The three latter antiepileptic drugs also failed in modifying other responses mediated by the activation of brain presynaptic Na(+) or Ca(2+) channels, including Glu release. This indicates that levetiracetam, valproic acid and topiramate mechanisms of action are unrelated with a decrease in presynaptic Na(+) or Ca(2+) channels permeability. It is concluded that depolarized cerebral isolated nerve endings represent a useful tool to unmask potential antiepileptic drugs targeting presynaptic Na(+) and/or Ca(2+) channels in the brain; such as vinpocetine or the anti-depressant sertraline, which high effectiveness to control seizures in the animal in vivo has been demonstrated.
Asunto(s)
Anticonvulsivantes/farmacología , Canales de Calcio/metabolismo , Hipocampo/efectos de los fármacos , Canales de Sodio/metabolismo , Animales , Calcio/metabolismo , Ácido Glutámico/metabolismo , Hipocampo/metabolismo , Técnicas In Vitro , Masculino , Terminales Presinápticos/metabolismo , Ratas WistarRESUMEN
Seizures are accompanied by an exacerbated activation of cerebral ion channels. 4-aminopyridine (4-AP) is a pro-convulsive agent which mechanism of action involves activation of Na(+) and Ca(2+) channels, and several antiepileptic drugs control seizures by reducing these channels permeability. The antidepressant, sertraline, and the anti-seizure drug vinpocetine are effective inhibitors of cerebral presynaptic Na(+) channels. Here the effectiveness of these compounds to prevent the epileptiform EEG activity induced by 4-AP was compared with the effectiveness of seven conventional antiepileptic drugs. For this purpose, EEG recordings before and at three intervals within the next 30 min following 4-AP (2.5 mg/kg, i.p.) were taken in anesthetized animals; and the EEG-highest peak amplitude values (HPAV) calculated. In control animals, the marked increase in the EEG-HPAV observed near 20 min following 4-AP reached its maximum at 30 min. Results show that this epileptiform EEG activity induced by 4-AP is prevented by sertraline and vinpocetine at a dose of 2.5 mg/kg, and by carbamazepine, phenytoin, lamotrigine and oxcarbazepine at a higher dose (25 mg/kg). In contrast, topiramate (25 mg/kg), valproate (100 mg/kg) and levetiracetam (100 mg/kg) failed to prevent the epileptiform EEG activity induced by 4-AP. It is concluded that 4-AP is a useful tool to elicit the mechanism of action of anti-seizure drugs at clinical meaningful doses. The particular efficacy of sertraline and vinpocetine to prevent seizures induced by 4-AP is explained by their high effectiveness to reduce brain presynaptic Na(+) and Ca(2+) channels permeability.
Asunto(s)
4-Aminopiridina/toxicidad , Anticonvulsivantes/uso terapéutico , Antidepresivos/uso terapéutico , Electroencefalografía/efectos de los fármacos , Convulsiones/prevención & control , Sertralina/uso terapéutico , Alcaloides de la Vinca/uso terapéutico , Animales , Anticonvulsivantes/farmacología , Antidepresivos/farmacología , Relación Dosis-Respuesta a Droga , Electroencefalografía/métodos , Masculino , Ratas , Ratas Wistar , Convulsiones/inducido químicamente , Convulsiones/fisiopatología , Sertralina/farmacología , Resultado del Tratamiento , Alcaloides de la Vinca/farmacologíaRESUMEN
In the present study, the effects of the two classical anti-epileptic drugs, carbamazepine and valproic acid, and the non-classical anti-seizure drug vinpocetine were investigated on the expression of the pro-inflammatory cytokines IL-1ß and TNF-α in the hippocampus of rats by PCR or western blot after the administration of one or seven doses. Next, the effects of the anti-seizure drugs were investigated on the rise in cytokine expression induced by lipopolysaccharides (LPS) inoculation in vivo. To validate our methods, the changes induced by the pro-convulsive agents 4-aminopyridine, pentylenetetrazole and pilocarpine were also tested. Finally, the effect of the anti-seizure drugs on seizures and on the concomitant rise in pro-inflammatory cytokine expression induced by 4-aminopyridine was explored. Results show that vinpocetine and carbamazepine reduced the expression of IL-1ß and TNF-α from basal conditions, and the increase in both pro-inflammatory cytokines induced by LPS. In contrast, valproic acid failed to reduce both the expression of the cytokines from basal conditions and the rise in IL-1ß and TNF-α expression induced by LPS. Tonic-clonic seizures induced either by 4-aminopyridine, pentylenetetrazole or pilocarpine increased the expression of IL-1ß and TNF-α markedly. 4-aminopyridine-induced changes were reduced by all the tested anti-seizure drugs, although valproic acid was less effective. We conclude that the anti-seizure drugs, vinpocetine and carbamazepine, whose mechanisms of action involve a decrease in ion channels permeability, also reduce cerebral inflammation. The mechanism of action of anti-seizure drugs like vinpocetine and carbamazepine involves a decrease in Na(+) channels permeability. We here propose that this mechanism of action also involves a decrease in cerebral inflammation.
Asunto(s)
Anticonvulsivantes/farmacología , Carbamazepina/farmacología , Hipocampo/metabolismo , Interleucina-1beta/biosíntesis , Factor de Necrosis Tumoral alfa/biosíntesis , Ácido Valproico/farmacología , Alcaloides de la Vinca/farmacología , 4-Aminopiridina/antagonistas & inhibidores , 4-Aminopiridina/farmacología , Animales , Conducta Animal/efectos de los fármacos , Western Blotting , Convulsivantes/farmacología , ADN Complementario/biosíntesis , ADN Complementario/genética , Epilepsia Tónico-Clónica/inducido químicamente , Epilepsia Tónico-Clónica/fisiopatología , Hipocampo/efectos de los fármacos , Interleucina-1beta/antagonistas & inhibidores , Lipopolisacáridos/farmacología , Masculino , Reacción en Cadena de la Polimerasa , Ratas , Ratas Wistar , Factor de Necrosis Tumoral alfa/antagonistas & inhibidoresRESUMEN
OBJECTIVES: Analytical interferences, caused by antibodies, often go unnoticed and require a deep understanding of analyzer principles in the correct clinical context. METHODS: A case report details a 56-year-old man with symptoms of hyperviscosity syndrome (HVS) due to multiple myeloma. RESULTS: The DxH 900 analyzer revealed abnormalities in the nucleated red blood cell (nRBC) graph, attributed to a high concentration of IgA kappa. Immediate plasmapheresis successfully treated HVS, reducing the monoclonal component and eliminating the aberrant green signal. CONCLUSIONS: In the appropriate clinical context, the recognition of analytical interferences is necessary for accurate clinical interpretation, and it is only possible with knowledge of the analytical principles of the instruments. In this case, the high concentration of IgA kappa generated an aberrant green signal in the VCSm.
RESUMEN
Vinpocetine is a neuroprotective drug that exerts beneficial effects on neurological symptoms and cerebrovascular disease. 3-nitropropionic acid (3-NPA) is a toxin that irreversibly inhibits succinate dehydrogenase, the mitochondrial enzyme that acts in the electron transport chain at complex II. In previous studies in striatum-isolated nerve endings (synaptosomes), we found that vinpocetine decreased dopamine (DA) at expense of its main metabolite 3,4-dihydroxyphenylacetic acid (DOPAC), and that 3-NPA increased DA, reactive oxygen species (ROS), DA-quinone products formation, and decreased DOPAC. Therefore, in this study, the possible effect of vinpocetine on 3-NPA-induced increase in DA, ROS, lipid peroxidation, and DA-quinone products formation in striatum synaptosomes were investigated, and compared with the effects of the antioxidant α-tocopherol. Results show that the increase in DA induced by 3-NPA was inhibited by both 25 µM vinpocetine and 50 µM α-tocopherol. Vinpocetine, as α-tocopherol, also inhibited 3-NPA-induced increase in ROS (as judged by DCF fluorescence), lipid peroxidation (as judged by TBA-RS formation), and DA-quinone products formation (as judged by the nitroblue tetrazolium reduction method). As in addition to the inhibition of complex II exerted by 3-NPA, 3-NPA increases DA-oxidation products that in turn can inhibit other sites of the respiratory chain, the drop in DA produced by vinpocetine and α-tocopherol may importantly contribute to their protective action from oxidative damage, particularly in DA-rich structures.
Asunto(s)
Cuerpo Estriado/efectos de los fármacos , Dopamina/metabolismo , Terminaciones Nerviosas/efectos de los fármacos , Inhibición Neural/efectos de los fármacos , Nitrocompuestos/farmacología , Estrés Oxidativo/efectos de los fármacos , Propionatos/farmacología , Alcaloides de la Vinca/farmacología , alfa-Tocoferol/farmacología , Animales , Anticonvulsivantes/farmacología , Antioxidantes/farmacología , Cuerpo Estriado/química , Dopamina/biosíntesis , Terminaciones Nerviosas/química , Inhibición Neural/fisiología , Fármacos Neuroprotectores/farmacología , Estrés Oxidativo/fisiología , RatasRESUMEN
In the present study, a possible sertraline action on cerebral pre-synaptic Na(+) channels was investigated. For this purpose, the effect of sertraline on responses induced by the Na(+) channel opener, veratridine, namely the increase in Na(+) and in neurotransmitter release in hippocampus-isolated nerve endings was investigated. Results show that sertraline in the low µM range (1.5-25 µM) progressively inhibits the rise in Na(+) and the release of pre-loaded [(3) H]Glu as well as the release of endogenous 5-HT, Glu and GABA (detected by HPLC) induced by veratridine depolarization either under external Ca(2+) -free conditions or in the presence of external Ca(2+) . In addition, under non-depolarized conditions, sertraline (25 µM) increased the external concentration of 5-HT at expense of its internal concentration, and unchanged the external and internal concentrations of the amino acid neurotransmitters and of the 5-HT main metabolite, 5-HIAA. This result is consistent with the sertraline inhibitory action of the serotonin transporter. However, sertraline is unlikely to inhibit pre-synaptic Na(+) channels permeability by increasing external 5-HT. Because 5-HT in a wide concentration range (1-1000 µM) did not change the veratridine-induced increase in Na(+) . In summary, present findings demonstrate that besides the inhibition of 5-HT reuptake, sertraline is an effective inhibitor of pre-synaptic Na(+) channels controlling neurotransmitter release.
Asunto(s)
Hipocampo/efectos de los fármacos , Terminaciones Nerviosas/efectos de los fármacos , Terminales Presinápticos/efectos de los fármacos , Sertralina/farmacología , Bloqueadores de los Canales de Sodio , Canales de Sodio/efectos de los fármacos , Animales , Calcio/farmacología , Ácido Glutámico/metabolismo , Hipocampo/citología , Ácido Hidroxiindolacético/metabolismo , Técnicas In Vitro , Masculino , Neurotransmisores/metabolismo , Ratas , Ratas Wistar , Serotonina/metabolismo , Sodio/metabolismo , Tetrodotoxina/farmacología , Veratridina/farmacología , Ácido gamma-Aminobutírico/metabolismoRESUMEN
In order to investigate a potential anticonvulsive action of sertraline (i.p.), its effects on seizures, EEG epileptiform activity and EEG amplitude increases induced by two convulsive agents were evaluated and compared with the effects of carbamazepine. Around 20 min following 4-aminopyridine (4-AP, 2.5 mg/kg, i.p.), tonic-clonic seizures and epileptiform activity were observed in control animals. A single sertraline pre-injection of 2.5 mg/kg, but not of 0.75 mg/kg, prevented these changes to 4-AP. Repeated daily administration of 0.75 mg/kg for one week, however, effectively inhibited the changes induced by 4-AP. The first generalized tonic-clonic seizure and EEG changes in response to pentylenetetrazole (PTZ, 50 mg/kg, i.p.) were observed near the first minute in control animals. Single sertraline doses above 5 mg/kg prevented the PTZ-induced changes. Moreover, a single carbamazepine dose of 25 mg/kg (i.p.), but not of 15 mg/kg, prevented the changes induced by the above convulsive agents. An anti-seizure action of the antidepressant sertraline is strongly suggested by these findings.
Asunto(s)
Anticonvulsivantes/uso terapéutico , Encéfalo/efectos de los fármacos , Convulsiones/prevención & control , Sertralina/uso terapéutico , 4-Aminopiridina/farmacología , Animales , Anticonvulsivantes/administración & dosificación , Encéfalo/fisiopatología , Carbamazepina/administración & dosificación , Carbamazepina/uso terapéutico , Modelos Animales de Enfermedad , Electroencefalografía/efectos de los fármacos , Conducta Exploratoria/efectos de los fármacos , Masculino , Pentilenotetrazol/farmacología , Ratas , Ratas Wistar , Convulsiones/inducido químicamente , Convulsiones/fisiopatología , Sertralina/administración & dosificación , Vocalización Animal/efectos de los fármacosRESUMEN
BACKGROUND AND AIMS: Hereditary anemia (HA) encloses a wide group of rare inherited disorders with clinical and hematologic overlaps that complicate diagnosis. MATERIALS AND METHODS: A 48-gene panel was developed to diagnose HA by Next Generation Sequencing (NGS) in a large cohort of 165 patients from 160 unrelated families. RESULTS: Patients were divided in: A) patients who had a suspicion of a specific type of HA (n = 109), and B) patients who had a suspicion of HA but with no clear type (n = 56). Diagnostic performance was 83.5% in group A and a change of the initial diagnosis occurred in 11% of these patients. In group B, 35.7% of patients achieved a genetic diagnosis. NGS identified 6 cases of xerocytosis, 6 of pyruvate kinase (PK) deficiency, 4 of G6PD, and 1 case of phytosterolemia with no initial suspicion of these pathologies, which is clinically relevant since they have specific treatment. Five patients were found to carry variants associated to two different pathologies (4 of them combining a metabolic deficiency and a membrane defect), and 44 new variants were identified in 41 patients. CONCLUSION: The use of NGS is a sensitive technique to diagnose HA and it shows better performance when patients are better characterized.
Asunto(s)
Anemia Hemolítica Congénita no Esferocítica , Anemia Hemolítica Congénita , Errores Innatos del Metabolismo del Piruvato , Anemia Hemolítica Congénita/diagnóstico , Anemia Hemolítica Congénita/genética , Anemia Hemolítica Congénita no Esferocítica/genética , Femenino , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Mutación , Piruvato Quinasa/deficiencia , Errores Innatos del Metabolismo del Piruvato/diagnóstico , Errores Innatos del Metabolismo del Piruvato/genéticaRESUMEN
The striatum is a cerebral structure particularly susceptible to the metabolic challenge exerted by 3-nitropropionic acid (3-NPA), a toxin that inhibits the respiratory chain at complex II. The striatum, which receives the nerve endings of the nigro-striatal pathway, concentrates the largest amount of 3,4-dihydroxyphenylethylamine or dopamine (DA) in the brain. DA is metabolized to 3,4-dihydroxyphenylacetic acid (DOPAC) by monoamine oxidase (MAO), an enzyme that contains a redox-active disulfide in the active site. In striatum isolated nerve endings exposed to 3-NPA in vitro, DA increased and DOPAC decreased already after 10 min, and after 2 h also an increase in reactive oxygen species and DA-quinone products formation was detected. These 3-NPA-induced effects resulted in an increase in DA release after 2 h. In striatum homogenates from animals presenting motor disturbances in response to 3-NPA in vivo, the DA metabolites homovanillic acid and DOPAC were increased. It is concluded that in the striatum nerve endings where DA is particularly concentrated, the increase in reactive oxygen species induced by 3-NPA, oxidizes DA generating DA-quinones. These DA-quinones may form adducts with the active site of MAO type A reducing its activity. The DA not metabolized to DOPAC is both, used to unchain generation of more of the harmful DA-oxidation products and released to the external medium, where is metabolized by the non-neuronal enzymes MAO type B and catechol-O-methyltransferase.
Asunto(s)
Cuerpo Estriado/efectos de los fármacos , Neurotoxinas/toxicidad , Nitrocompuestos/toxicidad , Propionatos/toxicidad , Ácido 3,4-Dihidroxifenilacético/metabolismo , Animales , Catecolaminas/metabolismo , Dopamina/análogos & derivados , Dopamina/metabolismo , Exocitosis/efectos de los fármacos , Técnicas In Vitro , Masculino , Actividad Motora/efectos de los fármacos , Terminaciones Nerviosas/metabolismo , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Especies Reactivas de Oxígeno/metabolismo , Sinaptosomas/metabolismoRESUMEN
The effects of two classic antiepileptic drugs (carbamazepine and phenytoin), a potential antiepileptic (vinpocetine) and a monoamine-oxidase inhibitor (clorgyline) on the simultaneous changes (detected by HPLC) on Glu, Asp, dopamine and DOPAC inside and outside striatal isolated nerve endings were investigated. Under resting conditions phenytoin, carbamazepine and clorgyline increased dopamine release. Phenytoin and clorgyline increased internal dopamine and decreased DOPAC formation. Carbamazepine decreased internal dopamine and practically did not change DOPAC formation. Glu and Asp release was unchanged. Neurotransmitter release induced by the Na+ channel opener veratridine was reduced by all the antiepileptic drugs tested, except phenytoin which, like clorgyline, facilitated veratridine-induced dopamine release. We conclude that besides the antagonism exerted by carbamazepine, phenytoin and vinpocetine on excitatory neurotransmitters release triggered by Na+ channel activation, that might importantly contribute to their anticonvulsant action, they exert different actions on striatal dopamine distribution, that might explain their different side effect profiles.
Asunto(s)
Anticonvulsivantes/farmacología , Catecolaminas/metabolismo , Cuerpo Estriado/efectos de los fármacos , Inhibidores de la Monoaminooxidasa/farmacología , Terminaciones Nerviosas/efectos de los fármacos , Canales de Sodio/metabolismo , Ácido 3,4-Dihidroxifenilacético/metabolismo , Animales , Anticonvulsivantes/efectos adversos , Ácido Aspártico/metabolismo , Carbamazepina/efectos adversos , Carbamazepina/farmacología , Clorgilina/efectos adversos , Clorgilina/farmacología , Cuerpo Estriado/metabolismo , Cuerpo Estriado/ultraestructura , Dopamina/metabolismo , Glutamina/metabolismo , Técnicas In Vitro , Masculino , Inhibidores de la Monoaminooxidasa/efectos adversos , Terminaciones Nerviosas/metabolismo , Fenitoína/efectos adversos , Fenitoína/farmacología , Ratas , Ratas Wistar , Agonistas de los Canales de Sodio , Alcaloides de la Vinca/efectos adversos , Alcaloides de la Vinca/farmacologíaRESUMEN
OBJECTIVE: To compare the acute, chronic and post-treatment effects of the classic antiepileptic drug carbamazepine (CBZ) and the potential antiepileptic vinpocetine (VPC), successfully used in the treatment of brain vascular origin disorders, on 4-aminopyridine (4-AP)-induced increase in auditory threshold, brain-auditory-evoked-potentials (BAEPs) later waves alterations and epileptiform activity. METHODS: BAEP and EEG recordings before and following 4-AP (3mg/kg, i.p.) were obtained in guinea pigs. One week after, the animals received a daily injection (i.p.) of vehicle, 3mg/kg VPC or 17 mg/kg CBZ for 13 days. The acute and chronic effects before and following 4-AP were tested at the 1st and last days, respectively, and the post-treatment effect 1 month after the end of treatment. RESULTS: CBZ and 4-AP increased BAEPs threshold and BAEPs P4 wave latency. Chronic CBZ inhibited 4-AP-induced increase in P3 amplitude. In the VPC-treated group, all the 4-AP-induced BAEPs changes were prevented. Seizures were prevented in 50% and 75% of the animals by chronic CBZ and VPC, respectively. After acute VPC and after the end of VPC-treatment 4-AP failed to induce seizures in 50% of the animals. CONCLUSION: VPC inhibits 4-AP-induced seizures and hearing loss, even after post-treatment, at a concentration about 10 times lower than CBZ. SIGNIFICANCE: The complications in hearing that can accompany epilepsy can be prevented by VPC, indicating its advantage as an alternative antiepileptic.
Asunto(s)
Anticonvulsivantes/uso terapéutico , Carbamazepina/uso terapéutico , Pérdida Auditiva/tratamiento farmacológico , Convulsiones/tratamiento farmacológico , Alcaloides de la Vinca/uso terapéutico , 4-Aminopiridina , Estimulación Acústica/métodos , Animales , Umbral Auditivo/efectos de los fármacos , Modelos Animales de Enfermedad , Interacciones Farmacológicas , Potenciales Evocados Auditivos/efectos de los fármacos , Cobayas , Pérdida Auditiva/inducido químicamente , Masculino , Psicoacústica , Convulsiones/inducido químicamente , Factores de TiempoRESUMEN
The effect of carbamazepine, phenytoin, valproate, oxcarbazepine, lamotrigine and topiramate, that are among the most widely used antiepileptic drugs (AEDs), and of the new putative AED vinpocetine on the Ca(2+) channel-mediated release of [(3)H]Glu evoked by high K(+) in hippocampal isolated nerve endings was investigated. Results show that carbamazepine, oxcarbazepine and phenytoin reduced [(3)H]Glu release to high K(+) to about 30% and 55% at concentrations of 500 microM and 1500 microM, respectively; lamotrigine and topiramate to about 27% at 1500 microM; while valproate failed to modify it. Vinpocetine was the most potent and effective; 50 microM vinpocetine practically abolished the high K(+) evoked release of [(3)H]Glu. Comparison of the inhibition exerted by the AEDs on [(3)H]Glu release evoked by high K(+) with the inhibition exerted by the AEDs on [(3)H]Glu release evoked by the Na(+) channel opener, veratridine, shows that all the AEDs are in general more effective blockers of the presynaptic Na(+) than of the presynaptic Ca(2+) channel-mediated response. The high doses of AEDs required to control seizures are frequently accompanied by adverse secondary effects. Therefore, the higher potency and efficacy of vinpocetine to reduce the permeability of presynaptic ionic channels controlling the release of the most important excitatory neurotransmitter in the brain must be advantageous in the treatment of epilepsy.
Asunto(s)
Anticonvulsivantes/farmacología , Canales de Calcio/fisiología , Ácido Glutámico/metabolismo , Canales de Sodio/fisiología , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismo , Animales , Bloqueadores de los Canales de Calcio/farmacología , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Hipocampo/ultraestructura , Masculino , Potasio/farmacología , Ratas , Ratas Wistar , Bloqueadores de los Canales de Sodio/farmacología , Tetrodotoxina/farmacología , Tritio/metabolismo , omega-Agatoxina IVA/farmacologíaRESUMEN
Several of the most effective antiepileptic drugs are believed to stop the paroxysmal neuronal activity acting as Na(+) channel blockers. However, no single study comparing in parallel the potency and efficacy of the most commonly used antiepileptic drugs on brain Na(+) channel-mediated responses is available. In the present study the effects of increasing concentrations of carbamazepine, phenytoin, lamotrigine, oxcarbazepine and topiramate, which are among the most frequently used antiepileptic drugs, and of the new putative antiepileptic drug, vinpocetine, on the release of glutamate (Glu) elicited by the Na(+) channel opener, veratridine were investigated in hippocampal isolated nerve endings preloaded with the labeled excitatory amino acid neurotransmitter. The present results show that carbamazepine, phenytoin, lamotrigine and oxcarbazepine, in the range from 150 to 1500 microM, progressively inhibit [(3)H]Glu release induced by veratridine. Also vinpocetine progressively inhibits the veratridine-induced response, but in a much lower range of concentrations (from 1.5 to 15 microM), whereas topiramate only exerts a modest inhibition (20%) of Glu release to veratridine at the highest dose tested (1500 microM). These results indicate that the mechanism of action of several of the most widely used antiepileptic drugs involves reduction in cerebral presynaptic voltage sensitive Na(+) channels permeability. Considering that the high doses of antiepileptic drugs required to control seizures are frequently accompanied by adverse secondary effects, the higher potency of vinpocetine to reduce Na(+) channels permeability might be advantageous.
Asunto(s)
Anticonvulsivantes/farmacología , Ácido Glutámico/metabolismo , Hipocampo/ultraestructura , Terminaciones Nerviosas/efectos de los fármacos , Canales de Sodio/fisiología , Animales , Relación Dosis-Respuesta a Droga , Técnicas In Vitro , Masculino , Ratas , Ratas Wistar , Tritio/metabolismoRESUMEN
OBJECTIVE: To characterize the acute and chronic effects of the antiepileptic drugs (AEDs): carbamazepine (CBZ), phenytoin (PHT), valproic acid (VPA) and vinpocetine (VPC), at doses 20, 6, 30 and 2mg/kg, respectively, on the latencies and amplitudes of the waves of brainstem auditory evoked potentials (BAEPs) elicited by a supra-threshold stimulus alongside BAEP threshold. METHODS: BAEPs elicited by a stimulus of high (100dB nHL) intensity and BAEP thresholds were obtained at 4 and 8kHz: before, after the start of treatment, and following 28 days of a daily injection of the AEDs. RESULTS: After the start of treatment BAEPs were unchanged. After the long term treatment, CBZ and PHT increased P3 and P4 wave peak latencies and reduced P4 amplitude. Chronic VPA did not modify BAEP waves, and chronic VPC reduced P3 and P4 latencies. P1 and P2 were unchanged. BAEP thresholds at 4 and 8kHz were increased by CBZ, PHT and VPA, and decreased by VPC. CONCLUSIONS: The chronic administration of several AEDs modifies BAEP waves of retro-cochlear origin. SIGNIFICANCE: Alterations in the generators of the later waves of BAEPs underlie, in most cases, the changes in hearing sensitivity produced by the long term treatment with AEDs at therapeutic relevant doses.
Asunto(s)
Anticonvulsivantes/farmacología , Vías Auditivas/efectos de los fármacos , Umbral Auditivo/efectos de los fármacos , Tronco Encefálico/efectos de los fármacos , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Estimulación Acústica , Animales , Vías Auditivas/fisiología , Percepción Auditiva/efectos de los fármacos , Percepción Auditiva/fisiología , Umbral Auditivo/fisiología , Tronco Encefálico/fisiología , Carbamazepina/farmacología , Electrofisiología , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Cobayas , Masculino , Conducción Nerviosa/efectos de los fármacos , Conducción Nerviosa/fisiología , Fenitoína/farmacología , Tiempo de Reacción/efectos de los fármacos , Tiempo de Reacción/fisiología , Ácido Valproico/farmacología , Alcaloides de la Vinca/farmacologíaRESUMEN
The single and combined effects of carbamazepine and vinpocetine on the release of the excitatory amino acid neurotransmitter glutamate, on the rise in internal Na+ (Na(i), as determined with SBFI), and on the rise in internal Ca2+ (Ca(i), as determined with fura-2) induced by an increased permeability of presynaptic Na+ channels, with veratridine, or by an increased permeability of presynaptic Ca2+ channels with high K+, were investigated in isolated hippocampal nerve endings. The present study shows that carbamazepine and vinpocetine, both inhibit dose dependently the release of preloaded [3H]Glu induced by veratridine. However, carbamazepine is two orders of magnitude less potent than vinpocetine. The calculated IC(50)'s for carbamazepine and vinpocetine to inhibit veratridine-induced [3H]Glu release are 200 and 2 microM, respectively. Consistently 150 microM carbamazepine and 1.5 microM vinpocetine reduce the veratridine-induced rise in Na(i) in a similar extent. The single effects of carbamazepine and of vinpocetine on the presynaptic Na+ channel mediated responses, namely the rise in Na(i) and the release of Glu induced by veratridine, are additive. Responses that depend on the entrance of external Ca2+ via presynaptic Ca2+ channels, such as the release of [3H]Glu and the rise in Ca(i) induced by high K+, are insensitive to 300 microM carbamazepine and slightly reduced by 5 microM vinpocetine. It is concluded that the additive effects of carbamazepine, which is one of the most common antiepileptic drugs, and vinpocetine that besides its known neuroprotective action and antiepileptic potential is a memory enhancer, may perhaps be advantageous in the treatment of epileptic patients.
Asunto(s)
Carbamazepina/farmacología , Ácido Glutámico/metabolismo , Hipocampo/efectos de los fármacos , Canales Iónicos/efectos de los fármacos , Terminales Presinápticos/efectos de los fármacos , Alcaloides de la Vinca/farmacología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Anticonvulsivantes/farmacología , Calcio/metabolismo , Canales de Calcio/efectos de los fármacos , Canales de Calcio/metabolismo , Relación Dosis-Respuesta a Droga , Sinergismo Farmacológico , Quimioterapia Combinada , Hipocampo/metabolismo , Canales Iónicos/metabolismo , Masculino , Fármacos Neuroprotectores/farmacología , Técnicas de Cultivo de Órganos , Terminales Presinápticos/metabolismo , Ratas , Ratas Wistar , Sodio/metabolismo , Canales de Sodio/efectos de los fármacos , Canales de Sodio/metabolismo , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología , Veratridina/farmacologíaRESUMEN
The long-term effect of three of the most widely used antiepileptic drugs at relevant doses on the hearing decline that accompanies pentylenetetrazole (PTZ)-induced experimental epilepsy was investigated here, and compared with the effect of vinpocetine (VPC), which is a drug with antiepileptic potential. For this purpose, cortical activity (monitored by the EEG) and auditory sensitivity, as indicated by brainstem auditory evoked potential (BAEP) threshold at 4 and 8 kHz tone frequencies, were determined in guinea pigs daily injected for 28 days with vehicle (control), 20 mg/kg carbamazepine (CBZ), 6 mg/kg phenytoin (PHT), 30 mg/kg valproate (VPA) or 2 mg/kg vinpocetine (VPC) before and after the administration of PTZ at a convulsing dose (100 mg/kg). Results show that all the antiepileptic drugs tested were more or less effective in preventing PTZ-induced seizures. The long-term treatment with VPC decreased the auditory threshold, whereas the long-term treatment with CBZ, PHT or VPA increased the auditory threshold to a similar extent as the convulsing agent, PTZ. The combined effects of the antiepileptic drugs and PTZ on auditory threshold were additive. Therefore, only VPC prevented the increase in the auditory threshold induced by PTZ. It is concluded that the hearing loss produced by the long-term treatment with the most commonly used antiepileptic drugs could be aggravated by the illness. The prevention exerted by VPC on the hearing decline that accompanies experimental epilepsy, along with its capacity to control seizures at low doses in this and other animal models of epilepsy, would make VPC a valid candidate for the treatment of epilepsy.
Asunto(s)
Anticonvulsivantes/farmacología , Convulsivantes/toxicidad , Audición/efectos de los fármacos , Pentilenotetrazol/toxicidad , Estimulación Acústica/métodos , Animales , Anticonvulsivantes/uso terapéutico , Umbral Auditivo/efectos de los fármacos , Modelos Animales de Enfermedad , Relación Dosis-Respuesta en la Radiación , Interacciones Farmacológicas , Electroencefalografía , Epilepsia/inducido químicamente , Epilepsia/tratamiento farmacológico , Epilepsia/fisiopatología , Cobayas , Factores de TiempoRESUMEN
The objective of this study was to get a more understandable picture of the mechanism underlying the anticonvulsant action of vinpocetine. The question of how the cerebral excitability is affected was investigated by determining the effect of vinpocetine on the changes on the internal concentrations of Na(+) (Na(i)) and Ca(2+) (Ca(i)) induced by different concentrations of the convulsing agent 4-aminopyridine (4-AP) in striatal isolated nerve endings. The cytosolic concentrations of Na(i) and Ca(i) were detected fluorimetrically with sodium-binding benzofuran isophthalate (SBFI) and fura-2, respectively. Vinpocetine, like the Na(+) channel blocker, tetrodotoxin, abolished the increase in Na(i) induced by 0.1 mM 4-AP and only inhibited in 30% the rise in Na(i) induced by 1mM 4-AP. In contrast with the different sensitivity of the rise in Na(i) induced by 0.1 and 1mM 4-AP to vinpocetine and tetrodotoxin, the rise in Ca(i) induced by the two concentrations of 4-AP was markedly inhibited by vinpocetine (and tetrodotoxin), indicating that only the voltage-sensitive sodium channels (VSSC)-mediated fraction of the rise in Na(i) induced by 4-AP is linked with the activation of pre-synaptic Ca(2+) channels. The elevation of Ca(2+) induced by high K(+) (30 mM) does not require a Na(+) gradient and is vinpocetine and tetrodotoxin insensitive. In contrast, the elevation of Ca(i) induced by 4-AP, requires a physiological (out/in) Na(+) gradient and is vinpocetine and tetrodotoxin-sensitive. It is concluded that by blocking the tetrodotoxin-sensitive fraction of the rise in Na(i) induced by 4-AP, vinpocetine inhibits the concomitant rise in Ca(i) induced by 4-AP. The inhibitory effect of vinpocetine on pre-synaptic voltage-sensitive sodium channels may underlie the in vivo anticonvulsant action of vinpocetine.
Asunto(s)
Señalización del Calcio/efectos de los fármacos , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/efectos de los fármacos , Sinapsis/efectos de los fármacos , Sinaptosomas/efectos de los fármacos , Alcaloides de la Vinca/farmacología , 4-Aminopiridina/farmacología , Animales , Anticonvulsivantes/farmacología , Calcio/metabolismo , Canales de Calcio/metabolismo , Señalización del Calcio/fisiología , Relación Dosis-Respuesta a Droga , Masculino , Neostriado/química , Bloqueadores de los Canales de Potasio/farmacología , Ratas , Ratas Wistar , Sodio/metabolismo , Canales de Sodio/metabolismo , Sinapsis/química , Sinapsis/metabolismo , Membranas Sinápticas/efectos de los fármacos , Membranas Sinápticas/metabolismo , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología , Sinaptosomas/química , Sinaptosomas/metabolismo , Tetrodotoxina/farmacología , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/fisiologíaRESUMEN
The present study shows that omega-agatoxin-TK, a toxin of the venom of Agelenopsis aperta, which is 10 times more concentrated than the P/Q type Ca(2+) channel blocker, omega-agatoxin-IVA in the venom, inhibits the high K(+) depolarisation-induced rise in internal Ca(2+) (Ca(i), as determined with fura-2) dose dependently in cerebral (striatal and hippocampal) isolated nerve endings, with calculated IC(50)'s of about 60nM. The maximal inhibition exerted by omega-agatoxin-TK in striatal synaptosomes (61 +/- 11%) is 10% larger than in hippocampal synaptosomes, suggesting a larger population of omega-agatoxin-TK-sensitive Ca(2+) channels in striatal than in hippocampal nerve endings. The N-type Ca(2+) channel blocker, omega-conotoxin-GVIA (1muM), inhibits part of the omega-agatoxin-TK-insensitive rise in Ca(i) induced by high K(+). In contrast to the inhibition exerted by omega-agatoxin-TK on the Ca(i) response to high K(+), omega-agatoxin-TK failed to inhibit the tetrodotoxin-sensitive elevations in Ca(i) and in internal Na(+) (Na(i), as determined with SBFI) induced by veratridine, indicating that the Ca(2+) influx activated by veratridine does not involve omega-agatoxin-TK-sensitive channels. High K(+) does not increase Na(i). In [(3)H]Glu preloaded hippocampal synaptosomes super-fused with low Na(+) Krebs Ringer HEPES (a condition that guarantees the elimination of neurotransmitter transporters-mediated release), the release of [(3)H]Glu induced by high K(+) is absolutely dependent on the entrance of external Ca(2+). This exocytotic release of [(3)H]Glu attained in the absence of a chemical Na(+) gradient is inhibited with the same potency and efficacy by omega-agatoxin-TK and by omega-agatoxin-IVA, which is known to differ from omega-agatoxin-TK in its amino terminal moiety. These results indicate that omega-agatoxin-TK represents a good pharmacological tool to study P/Q type Ca(2+) channel-mediated responses in cerebral nerve endings.
Asunto(s)
Encéfalo/citología , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio Tipo P/efectos de los fármacos , Canales de Calcio Tipo P/metabolismo , Calcio/metabolismo , Ácido Glutámico/metabolismo , Terminaciones Nerviosas/metabolismo , Venenos de Araña/farmacología , Agatoxinas , Animales , Encéfalo/efectos de los fármacos , Química Encefálica/efectos de los fármacos , Tampones (Química) , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Masculino , Neostriado/efectos de los fármacos , Neostriado/metabolismo , Terminaciones Nerviosas/efectos de los fármacos , Potasio/farmacología , Ratas , Ratas Wistar , Canales de Sodio/efectos de los fármacos , Canales de Sodio/metabolismo , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismo , omega-Conotoxina GVIA/farmacologíaRESUMEN
OBJECTIVE: The purpose of the present study was to investigate if the sodium channel blocker and memory enhancer, vinpocetine, was capable to overcome the epileptic cortical activity, the abnormalities in the later waves of the auditory brainstem responses (ABRs) and the hearing loss induced by 4-AP at a convulsing dose in the guinea pig in vivo. METHODS: EEG and ABR recordings before and at specific times within 2h after the injection of 4-AP (2 mg/kg, i.p.) were taken in animals pre-injected i.p. with vehicle or with vinpocetine (2 mg/kg) 1 h before 4-AP. The amplitude and latency of the ABR waves induced by a monoaural stimulus of high intensity (100 dB nHL) at 4 and 8 kHz pure tone frequencies and the ABR threshold were determined in the animals exposed to the different experimental conditions. RESULTS: Vinpocetine inhibited the EEG changes induced by 4-AP for the ictal and post-ictal periods as well as the alterations in amplitude and latency of P3 and P4 and the increase in the ABR threshold induced by 4-AP. CONCLUSIONS: Vinpocetine prevents the retro-cochlear alterations and the hearing decline that accompany the epileptic cortical activity. SIGNIFICANCE: Vinpocetine could be a promising alternative for the treatment of epilepsy.
Asunto(s)
4-Aminopiridina/farmacología , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Nootrópicos/farmacología , Bloqueadores de los Canales de Potasio/farmacología , Alcaloides de la Vinca/farmacología , Animales , Interacciones Farmacológicas , Electroencefalografía/efectos de los fármacos , Epilepsia/tratamiento farmacológico , Cobayas , Audición/efectos de los fármacos , Pérdida Auditiva/inducido químicamente , Pérdida Auditiva/tratamiento farmacológico , Pérdida Auditiva/prevención & control , Masculino , Núcleo Olivar/efectos de los fármacos , Tiempo de Reacción/efectos de los fármacosRESUMEN
Here we investigate the effect of the neuroprotective drug, vinpocetine on the epileptic cortical activity, on the alterations of the later waves of brainstem auditory evoked potentials (BAEPs) and on the hearing decline induced by the convulsing agent, pentylenetetrazole (PTZ). Vinpocetine at doses from 2 to 10 mg/kg inhibits the tonic-clonic convulsions induced by PTZ (100 mg/kg). Vinpocetine injected at a dose of 2 mg/kg 4 h before PTZ completely prevents the characteristic electroencephalogram (EEG) changes induced by PTZ for the ictal and post-ictal periods. Vinpocetine also abolished the PTZ-induced changes in the amplitude and latency of the later waves of the BAEPs in response to pure tone burst monoaural stimuli (frequency 8 or 4 kHz intensity 100 dB), and the PTZ-induced increase in the BAEP threshold. These results show the antiepileptic potential of vinpocetine and indicate the capability of vinpocetine to prevent the changes in the BAEP waves associated with the hearing loss observed during generalized epilepsy.