Kindling Model Of Epileptogenesis Research Articles

Effect of a Ketogenic Diet on Oxidative Posttranslational Protein Modifications and Brain Homogenate Denaturation in the Kindling Model of Epilepsy in Mice.

This study focused on the ketogenic diet (KD) effects on oxidative posttranslational protein modification (PPM) as presumptive factors implicated in epileptogenesis. A 28-day of KD treatment was performed. The corneal kindling model of epileptogenesis was used. Four groups of adult male ICR mice (25-30g) were randomized in standard rodent chow (SRC) group, KD-treatment group; SRC + kindling group; KD + kindling group (n = 10 each). Advanced oxidation protein products (AOPP) and protein carbonyl contents of brain homogenates together with differential scanning calorimetry (DSC) were evaluated. Two exothermic transitions (Exo1 and Exo2) were explored after deconvolution of the thermograms. Factor analysis was applied. The protective effect of KD in the kindling model was demonstrated with both decreased seizure score and increased seizure latency. KD significantly decreased glucose and increased ketone bodies (KB) in blood. Despite its antiseizure effect, the KD increased the AOPP level and the brain proteome's exothermic transitions, suggestive for qualitative modifications. The ratio of the two exothermic peaks (Exo2/Exo1) of the thermograms from the KD vs. SRC treated group differed more than twice (3.7 vs. 1.6). Kindling introduced the opposite effect, changing this ratio to 2.7 for the KD + kindling group. Kindling significantly increased glucose and KB in the blood whereas decreased the BW under the SRC treatment. Kindling decreased carbonyl proteins in the brain irrespectively of the diet. Further evaluations are needed to assess the nature of correspondence of calorimetric images of the brain homogenates with PPM.

Anticonvulsive and anti-epileptogenesis effects of Echinacea purpurea root extract, an involvement of CB2 receptor.

Phytocannabinoids beyond the Δ9-tetrahy-drocannabinol have shown anticonvulsive effects. Also, alkylamides from Echinacea purpurea have been proved as cannabinomimetics. We examined the effect of the hydroalcoholic root extract of E.purpurea on pentylenetetrazol (PTZ)-induced tonic-clonic seizures and kindling model of epileptogenesis and the involvement of CB2 receptors as the mediator of this effect. Male Wistar rats (200±20g) were used. Single intraperitoneal (i.p.) injection of PTZ (80mg/kg) was used to induce tonic-clonic seizures. The kindling model of epileptogenesis was induced by daily injections of PTZ (37mg/kg; i.p. for 15days). Latency and duration of the stages were monitored for analysis. The hydroalcoholic root extract of E.purpurea was injected (i.p.) 20min before seizure induction at the doses of 10, 50, 100 and 200mg/kg. CB2 receptor antagonist SR144528 was injected (0.1mg/kg; i.p.) 20min before the Echinacea injection. In the tonic-clonic model, pretreatment with E.purpurea at the doses of 100 and 200mg/kg significantly increased latencies to S2-S6, while it significantly decreased S6 duration and mortality rate. SR144528 injection before the injection of 100mg/kg of E.purpurea significantly prevented the effects of the extract on S4-S6 latencies. In the kindling model, E.purpurea at the doses of 100 and 200mg/kg significantly delayed epileptogenesis and decreased mortality rate, while SR144528 injection before the injection of 100mg/kg of E. purpurea significantly blocked this effect of the extract. These findings revealed the anticonvulsive and antiepileptogenesis effects of the E.purpurea root extract, which can be mediated by CB2 receptors.

Comparative studies on the effects of clinically used anticonvulsants on the oxidative stress biomarkers in PTZ-induced kindling model of epileptogenesis in mice

Comparative studies on the effects of clinically used anticonvulsants on the oxidative stress biomarkers in PTZ-induced kindling model of epileptogenesis in mice

Proconvulsant effects of estriol, the third estrogen, in the mouse PTZ-kindling model.

The effect of estriol, the third estrogen, was evaluated for its effect on pentylenetetrazole (PTZ)-kindling model of epileptogenesis in mice followed by evaluation on kindling-induced changes in cognitive and motor functions. Kindling was induced by once every 2 days treatment with PTZ (25 mg/kg, i.p.) for 5 weeks. The seizure severity during induction of kindling and percentage incidence of animals kindled at the end of 5 weeks was recorded. Motor function was assessed using a grip strength meter while spatial memory was assessed in a cross maze. Estriol (0.005 and 0.01 mg/kg i.p.) reduced the time for induction of kindling from 5 weeks to 3 and 2 weeks for male and female mice respectively and enhanced the percentage incidence of seizures. Clomiphene (0.9 mg/kg i.p.) delayed the development of kindling and produced anticonvulsant effects. It also partially reversed the proconvulsant effects of estriol. On grip strength test and spontaneous alternation behaviour, a significant decline was observed in kindled mice which was further reduced by pre-treatment with estriol. Both clomiphene and diazepam were unable to reverse the reduced GS of PTZ-kindled mice but enhanced the percentage alternation of such animals. The study shows that estriol has powerful proconvulsant effects. Its administration in hormone replacement therapy or other indications, thus, requires careful monitoring in patients susceptible to epileptic seizures. The anticonvulsant effects of clomiphene requires further investigations.

Effect of medroxyprogesterone on development of pentylenetetrazole-induced kindling in mice

In the present study, the effect of medroxyprogesterone (MPA) is evaluated for its effect on pentylenetetrazole (PTZ) kindling model of epileptogenesis in mice followed by evaluation on kindling-induced changes in cognitive and motor functions. To explore whether the effects are mediated via progesterone receptors, a selective antagonist of progesterone (mifepristone, MIF) was also taken. Kindling was induced by once every 2 days treatment with PTZ (25 mg/kg, i.p.) for 5 weeks. The seizure severity during induction of kindling and % incidence of animals kindled at the end of 5 weeks were recorded. The motor function was assessed using a grip strength meter, whereas spatial memory was assessed in a cross maze. MPA (5 and 10 mg/kg, i.p.) significantly reduced the seizure severity scores and produced a significant decrease in the incidence of animals kindled at the end of 5 weeks (P<0.01). A higher efficacy was observed against male mice as compared with females following MPA. MIF neither reduced nor delayed the development of PTZ-induced kindling in mice. Also, it couldn't reverse the antiepileptogenic effects of MPA. On grip strength test (GST) and spontaneous alternation behavior (SAB), a significant decline in GST and % alternation was observed in kindled mice which was reversed by pre-treatment with MPA. MIF, however, could reverse only the reduced % alternation and not grip strength (GS) in PTZ-kindled animals. The study shows that MPA has antiepileptogenic effects against development of PTZ-induced kindling in mice that may not be mediated via progesterone receptors.

Conditional Deletion of NRSF in Forebrain Neurons Accelerates Epileptogenesis in the Kindling Model

Neuron-restrictive silencer factor (NRSF), also known as repressor element-1 silencing transcription factor, is a transcriptional repressor that plays important roles in embryonic development and neurogenesis. Recent findings show that NRSF is upregulated after seizures activity however, the link between NRSF and epileptogenesis remains poorly understood. To investigate the role of NRSF in epilepsy, we employed a Cre-loxp system to specifically delete NRSF in excitatory neurons of the postnatal mouse forebrain. In the kindling model of epileptogenesis, conditional NRSF knockout (NRSF-cKO) mice exhibited dramatically accelerated seizure progression and prolonged afterdischarge duration compared with control mice. Moreover, seizures activity-induced mossy fiber sprouting was enhanced in the NRSF-cKO mice. The degree of upregulation of Fibroblast growth factor 14 and Brain-derived neurotrophic factor (BDNF) following kainic acid-induced status epilepticus was significantly increased in the cortex of NRSF-cKO mice compared with control mice. Furthermore, the derepression of BDNF was associated by activation of PLCγ and PI(3)K signaling pathways. These findings indicate that NRSF functions as an intrinsic repressor of limbic epileptogenesis.

Effect of valproic acid on sodium currents in cortical neurons from patients with pharmaco-resistant temporal lobe epilepsy

In a selected group of temporal lobe epilepsy patients with seizures refractory to pharmacological treatment, pharmacological seizure control can be attained by surgical resection of the epileptic zone. We investigated to what extent pharmaco-resistance is reflected in a reduced response at the cellular level, in neurons acutely isolated from the temporal cortex resected in 20 patients. We studied the effect of valproic acid (VPA) on the transient sodium current, measured under whole-cell voltage-clamp conditions. We compared neurons from patients with temporal lobe sclerosis (S) with neurons from patients without hippocampal sclerosis (nS) and compared hippocampal CA1 neurons (CA) with neocortical neurons (NC). We could not detect differences in the voltage dependence and kinetics of sodium current activation and inactivation in any of the group comparisons. VPA shifted the voltage dependence of steady-state inactivation (expressed as V(h,i) in a Boltzmann fit) to more hyperpolarized levels. The shift induced by 2 mM VPA was -5.1 +/- 0.7 mV in CA-S (n = 13), -5.1 +/- 0.7 mV in CA-nS (n = 25), -4.3 +/- 0.5 mV in NC-S (n = 17) and -4.9 +/- 0.5 mV in NC-nS (n = 16) The relation between concentration and voltage shift had an EC50 of 1.4 +/- 0.2 mM VPA (n = 16) and a maximal shift of 9.6 +/- 0.9 mV. We conclude that pharmaco-resistance in these patients is not associated with a changed modulation of the sodium current by VPA. Results are discussed in the light of a reduced sodium current modulation by carbamazepine in CA1 neurons of patients with hippocampal sclerosis and of similar observations in the kindling model of epileptogenesis.

Changes in voltage-dependent calcium channel α 1-subunit mRNA levels in the kindling model of epileptogenesis

The establishment of a focus of epileptiform activity in the hippocampus of the rat, using the kindling paradigm, leads to enhanced voltage-dependent calcium conductance of CA1 pyramidal neurones (G.C. Faas, M. Vreugdenhil, W.J. Wadman, Calcium currents in pyramidal CA1 neurones in vitro after kindling epileptogenesis in the hippocampus of the rat, Neuroscience 75 (1996) 57–67; M. Vreugdenhil, W.J. Wadman, Kindling-induced long-lasting enhancement of calcium in hippocampal CA1 area of the rat: relation to calcium-dependent inactivation, Neuroscience 59 (1994) 105–114). Using semi-quantitative in situ hybridization techniques, we investigated whether these changes were associated with an altered expression of the genes that encode for the α 1 A–E-subunits of the voltage-dependent calcium channels (VDCC). Kindling epileptogenesis was induced in rats that received an electrical tetanic stimulation of the Schaffer collateral/commissural fibre pathway in the hippocampus twice daily. Two groups of rats were studied before the appearance of generalized seizures, one group after at least 5 generalized seizures (fully kindled) and one group was investigated at long-term (28 days) after the last seizure. During the initial stages of epileptogenesis, the α 1A-, α 1D- and α 1E-subunit mRNA levels were significantly increased in the different hippocampal subareas in comparison to the levels in control animals. In contrast, α 1B-subunit gene expression decreased in the CA1 area and dentate gyrus. No significant change was observed in the α 1C-I and α 1C-II expression. At the fully kindled stage, the only significant change was an up-regulation of the α 1B-subunit mRNA levels in the CA3 area, 24 h after the last seizure. No change in VDCC α 1-subunit gene expression was found in animals investigated long-term after the establishment of the fully kindled state. Thus, the VDCC a 1-subunit gene expression is altered in a subclass-specific manner during the early stages of kindling and may play a role in the establishment of a kindled focus, possibly caused by an alteration of the population of VDCCs involved in neurotransmitter release. The absence of long-lasting changes suggests that the maintenance of a kindled focus is not due to persisting alterations in VDCC α 1 mRNA levels.

Synaptic vesicle size and shape profile in the kindling model of epileptogenesis.

Excitatory synapses were studied in the dentate gyrus ipsilateral to stimulated entorhinal cortex in fully kindled rats 2 weeks after the last (3rd) stage 5 seizure. In previous studies of the same model marked redistribution of synaptic vesicles to a 'strategic position' in the vicinity of the synaptic cleft and a significant enlargement of postsynaptic element were described. In this study the size and shape of synaptic vesicles were evaluated in three zones parallel to the presynaptic membrane of the synaptic cleft. The first zone (0.1 micron) directly adjoined the active zone of presynaptic membrane, the second was from 0.1 to 0.2 micron and the third from 0.2 to 0.3 micron from the presynaptic membrane. The vesicles of both the experimental and control animals were significantly smaller in zone I than in zone II and III and, in the control animals there was a tendency of vesicles to diminish towards the active zone. Such a tendency was not observed in the experimental animals, the largest vesicles were in the middle of zone II and were significantly more rounded in comparison to the vesicles in the controls. On the contrary, the vesicles in zone I and III were more elongated in the experimental animals than in controls. Our results may be taken as a sign of active reconstruction of synaptic apparatus in relation to increased functional readiness of the synapses. Possible mechanisms as well as significance for the kindling and epileptogenesis are discussed.

GABA and epileptogenesis.

GABA and epileptogenesis.

N-methyl-d-aspartate and kainate receptor gene expression in hippocampal pyramidal and granular neurons in the kindling model of epileptogenesis

To investigate the changes underlying kindling epileptogenesis in the rat hippocampus, the levels of the messenger RNAs encoding for the subunits of the N-methyl-D-aspartate-receptor (1, 2A-D) and the kainate-receptor (1, -2, GluR-5, -6, -7) were determined in hippocampal principal neurons using in situ hybridization techniques and semi-quantitative analysis of the autoradiograms. Schaffer collateral-commissural pathway kindled rats were investigated at three different stages of kindling acquisition, always 24 h after the last stimulation. Furthermore, fully kindled rats were studied at long-term (28 days) after termination of kindling stimulations. NR1 messenger RNA levels were slightly decreased in CA1 area of fully kindled animals. In the fascia dentata region, a minor increase of NR2A and NR2B transcripts was found at all stages of kindling acquisition. KA-2 messenger RNA was enhanced in all hippocampal subfields during kindling development. However, none of these changes persisted at long-term after the last seizure and only the low-abundant GluR-7 expression was slightly depressed in the fascia dentata. From our observations we conclude that it is unlikely that alterations in N-methyl-Daspartate or kainate receptor gene expression play an important role in kindling acquisition or maintenance.

Expression of GABAA receptor subunit mRNAs in hippocampal pyramidal and granular neurons in the kindling model of epileptogenesis: an in situ hybridization study.

To investigate the molecular changes underlying kindling epileptogenesis in the rat hippocampus, the expression levels of the genes encoding for 13 different gamma-aminobutyric acid type-A receptor (GABAAR) subunits were measured in hippocampal principal neurons using in situ hybridization techniques and semi-quantitative analysis of the autoradiograms. Schaffer collateral-commissural pathway kindled rats were investigated at three different stages of kindling acquisition, at 24 h after the last seizure and at long-term (28 days) after termination of kindling stimulations. Changes were distinct for the different subunits in the three analyzed regions (CA1, CA3, fascia dentata) and also different for the various kindling stages. In all hippocampal areas at the early phases of kindling epileptogenesis, before the appearance of generalized seizures, an increase was found of those transcripts that constituted the majority of the expressed variants in control animals (alpha 1, alpha 2, alpha 4, beta 1, beta 2, beta 3, gamma 2/gamma 2L mRNA). In these stages, the increased levels of different variants in the granular neurons of the fascia dentata were more pronounced when compared to the pattern of changes in pyramidal cells of CA1 and CA3. In fully kindled animals, the expression levels of several subunits returned to control levels, whereas beta 3 and gamma 2/gamma 2L mRNA expression was still significantly enhanced in all areas. At long-term, few changes were encountered. The long-splice variant of gamma 2 was decreased within pyramidal and granular neurons while the total level of gamma 2 mRNA was not different from controls. The increased GABAAR subunit expression in the fascia dentata may underly the reported increased GABAAR ligand binding and the increased GABA mediated inhibition. However, the decreased GABAAR binding and the attenuation of GABAergic inhibition in CA1, could not be explained by a decrement of receptor subunit expression.