latrunculin-a and Seizures

Latrunculin A microperfusion of the hippocampus induces acute epileptic seizures and long-term biochemical changes leading to spontaneous seizures. This study tested the effect of eslicarbazepine acetate (ESL), a novel antiepileptic drug, on latrunculin A-induced acute and chronic seizures, and changes in brain amino acid extracellular levels. Hippocampi of Swiss mice were continuously perfused with a latrunculin A solution (4 μM, 1 μl/min, 7 h/day) with continuous EEG and videotape recording for 3 consecutive days. Microdialysate samples were analyzed by HPLC and fluorescence detection of taurine, glycine, aspartate, glutamate and GABA. Thereafter, mice were continuously video monitored for two months to identify chronic spontaneous seizures or behavioral changes. Control EEG recordings (8 h) were performed in all animals at least once a week for a minimum of one month.. Oral administration of ESL (100 mg/kg), previous to latrunculin A microperfusion, completely prevented acute latrunculin A-induced seizures as well as chronic seizures and all EEG chronic signs of paroxysmal activity. Hippocampal extracellular levels of taurine, glycine and aspartate were significantly increased during latrunculin A microperfusion, while GABA and glutamate levels remained unchanged. ESL reversed the increases in extracellular taurine, glycine and aspartate concentrations to basal levels and significantly reduced glutamate levels. Plasma and brain bioanalysis showed that ESL was completely metabolized within 1 h after administration to mainly eslicarbazepine, its major active metabolite.. ESL treatment prevented acute latrunculin A-induced seizures as well as chronic seizures and all EEG chronic signs of paroxysmal activity, supporting a possible anti-epileptogenic effect of ESL in mice.

Topics: Acute Disease; Amino Acids; Animals; Anticonvulsants; Aspartic Acid; Bridged Bicyclo Compounds, Heterocyclic; Chronic Disease; Dibenzazepines; Disease Models, Animal; Extracellular Space; gamma-Aminobutyric Acid; Glutamic Acid; Glycine; Hippocampus; Male; Mice; Seizures; Taurine; Thiazolidines

Clasmatodendrosis is an irreversible astroglial degenerative change, which includes extensive swelling and vacuolization of cell bodies and disintegrated and beaded processes. Since alteration in F-actin level influences on the formation of vacuoles/vesicles during exocytosis/endocytosis in astrocytes, we investigated whether F-actin polymerization involves clasmatodendrosis in the rat hippocampus following status epilepticus (SE). In the present study, vacuoles in clasmatodendrotic astrocytes showed LAMP-1 and LC3-II (a marker for autophagy) immunoreactivity. These findings reveal that clasmatodendrosis may be lysosome-derived autophagic astroglial death. Jasplakinolide (an F-actin stabilizer) infusion significantly decreased the size and the number of medium/large-sized vacuoles in each clasmatodendritic astrocyte accompanied by enhancement of phalloidin signals, as compared to vehicle-infusion. In contrast, latrunculin A (an F-actin-depolymerizing agent) infusion increased the size and the number of medium/large-sized vacuoles, which were dissociated adjacent to cell membrane. Therefore, our findings suggest that F-actin stabilization may inhibit lysosome-derived autophagic astroglial death during clasmatodendrosis.

Topics: Actins; Animals; Antineoplastic Agents; Astrocytes; Autophagy; Biomarkers; Bridged Bicyclo Compounds, Heterocyclic; Cell Death; Depsipeptides; Lysosomes; Male; Rats; Rats, Sprague-Dawley; Seizures; Thiazolidines

The effect of latrunculin A microperfusion on hippocampal extracellular concentrations of glutamate, aspartate, glycine and GABA, as measured by in vivo microdialysis, was investigated. Latrunculin A (4 microg/ml) was perfused for three consecutive days (8h a day) to promote in vivo F-actin depolymerization. Intrahippocampal latrunculin A microdialysis induced seizures during the second and third day of perfusion, and the animals started showing spontaneous seizures 1 month after lartrunculin A administration. Hippocampal glutamate levels were significantly increased during the first day of latrunculin A microperfusion without significant changes during the second and third day of perfusion. Aspartate levels were significantly increased during the first and second days of treatment. The rise on glutamate and asparate levels was partially reversed by perfusion of NMDA antagonist MK-801. Glycine concentrations were significantly increased during the 3 days of latrunculin A microdialyis, but no significant effect was observed on baseline GABA levels. One month after latrunculin A microperfusion, no significant differences in glutamate and aspartate extracellular concentrations were detected as compared to controls, however, significant increases in glycine and GABA extracellular concentrations were observed. The immediate increases in glutamate, aspartate and glycine levels indicate a modulatory effect of the F-actin cytoskeleton on extracellular concentrations of glutamate, aspartate and glycine. The chronic elevations in GABA and glycine levels are more likely to be related with long-term epileptogenesis processes. Our results suggest that the in vivo biochemical study of actin-dependent processes seems to be a promising approach to the neuropathology and neuropharmacology of epileptic seizures.

Topics: Actins; Animals; Bridged Bicyclo Compounds, Heterocyclic; Excitatory Amino Acids; gamma-Aminobutyric Acid; Glycine; Hippocampus; Male; Rats; Rats, Sprague-Dawley; Seizures; Thiazolidines

Eslicarbazepine acetate (ESL, BIA 2-093) is a novel antiepileptic drug endowed with an anticonvulsant potency similar to that of carbamazepine, and shares with carbamazepine and oxcarbazepine the capability to inhibit voltage-gated sodium channels. ESL is efficacious against maximal electroshock seizure-induced seizures, protects against picrotoxin-induced seizures in mice and rats, and prevents development of kindling in rats. In vivo, latrunculin A microperfusion in the rat hippocampus induces acute epileptic seizures and long-term biochemical changes leading to decreased picrotoxin seizure threshold and spontaneous seizures. We have tested the effect of ESL on latrunculin A-induced seizures, and its effect on the changes in extracellular amino acid levels induced by latrunculin A.. Rat hippocampus was continuously perfused with a latrunculin A solution (4 microM) through CMA/12 microdialysis probes at a flow rate of 2 microl/min during 8 h with continuous EEG and videotape recording for 3 consecutive days. The same protocol was repeated after oral administration of ESL (3, 10 and 30 mg/kg). Samples from the microdialysate were collected and analyzed by HPLC using pre-column derivatization with 6 aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) and fluorescence detection.. After the administration of 3 mg/kg of ESL, seizures were completely suppressed in the 66.7% of the rats. 10 and 30 mg/kg of ESL did completely suppressed seizures in the 100% of the animals studied. Hippocampal extracellular levels of glutamate, glycine and aspartate were significantly increased during latrunculin A microperfusion, while GABA levels remained unchanged. At the doses studied, ESL reversed the increases in extracellular glutamate and aspartate concentrations to basal levels and significantly reduced glycine levels.. ESL, at oral doses of 3, 10 and 30 mg/kg, shows an excellent anticonvulsant effect against seizures induced by latrunculin A microperfusion in the rat, and prevents the increases in glutamate and aspartate induced by latrunculin A.

Topics: Amino Acids; Animals; Anticonvulsants; Brain Chemistry; Bridged Bicyclo Compounds, Heterocyclic; Chromatography, High Pressure Liquid; Dibenzazepines; Electroencephalography; Extracellular Space; Hippocampus; Indicators and Reagents; Male; Marine Toxins; Microdialysis; Rats; Rats, Sprague-Dawley; Seizures; Thiazolidines

The molecular basis for developing epilepsy remains under debate. It is hypothesized that increased excitatory synaptic activity might activate the N-methyl-D-aspartate receptor/Ca(2+) transduction pathway, which induces long-lasting plasticity changes leading to recurrent epileptiform discharges. To determine if these effects are caused by disruption of F-actin in the dendritic spines, we have perfused the hippocampus of conscious rats with the F-actin-depolymerizing agent latrunculin Aand the actin filament stabilizer jasplakinolide. Single perfusions of latrunculin Aand jasplakinolide decrease and increase picrotoxin seizure threshold, respectively. Repeated perfusions of both latrunculin Aand jasplakinolide induce epileptic seizures and a long-term increase in neuronal excitability. These results suggest that actin disruption might not be just a consequence but also a possible cause of epileptic seizures. We propose a new experimental model in rats to study the biochemical changes that might lead to chronic seizures and a method for testing new antiepileptic drugs.

Topics: Actins; Animals; Anticonvulsants; Antineoplastic Agents; Bridged Bicyclo Compounds, Heterocyclic; Convulsants; Depsipeptides; Hippocampus; Male; Microdialysis; Picrotoxin; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Seizures; Thiazolidines