Tibor Szilagyi - Academia.edu (original) (raw)

Papers by Tibor Szilagyi

PubMed, 2015

Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's popula... more Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's population. Despite advances regarding therapy, about 30% of patients cannot be relieved of seizures, mainly because the pathophysiological mechanisms are still not elucidated completely. Basket, axo-axonic, bistratified, oriens-lacunosum moleculare (O-LM) and Ivy cells exert spatially and temporary different inhibition on principal neurons. Our aim was to evaluate the alterations of these interneuron populations during epileptogenesis. We induced status epilepticus in male Wistar rats using intraperitoneal pilocarpine injection, which was followed, after a latency period, by spontaneous recurrent seizures (SRS). Nissl staining was used for the analysis of gross morphological changes, whereas triple immunofluorescent-labeled sections (parvalbumin, somatostatin, neuropeptide-Y) were used for differentiation of the selected interneuron types. Putative interneurons identified by their neurochemical contents were quantified, and the cell density was calculated. Although animals developing SRS showed similar behavior, the degree of hippocampal sclerosis was different. In animals with hippocampal sclerotic cell death pattern the density of perisomatic inhibitory neurons was higher, but not significantly. The dendritic inhibitory bistratified cells were preserved, whereas the number of O-LM cells showed a significant decrease. A substantial loss was observed in the number and density of Ivy cells. We suggest that the loss of hippocampal input modulatory O-LM cells, and overall excitation controlling Ivy cells, has a role in the emergence of hyperexcitability. In the same time, alterations of output controlling interneurons might contribute to the propagation of the pathological synchronization to the cortex.

Romanian Journal of Morphology and Embryology, 2011

The cerebral cortex ensures an optimal interaction of mammals, including humans, with their envir... more The cerebral cortex ensures an optimal interaction of mammals, including humans, with their environment, by encoding, storing and combining information about the surrounding world and the internal milieu. Probably the simplest and the most popular region for studying the cortical network is the hippocampal CA1 area, because it has the least heterogeneous neuronal population, the somata and dendrites of principal neurons (pyramidal cells) are arranged into well defined layers and the extrinsic and intrinsic inputs are segregated. The relatively homogeneous pyramidal cell population is supported by a very heterogeneous GABAergic interneuron population, which provides not only general inhibition, but also regulates the precise timing of pyramidal cell activity. Interneurons usually innervate distinct domains of the surface of their target cell. The strategic placement of inhibitory synapses, indicate that GABAergic interneurons belonging to different classes serve distinct functions in the hippocampal network. Neuron types are usually defined according to various morphological, molecular and physiological features. Under typical experimental conditions only some of these parameters are available, therefore an important scientific question is: which partial measures are sufficient for correct recognition of a class of cell. By immunohistochemistry it is possible to stain all neurochemically identical neurons in a given brain region, therefore it is the most widely used method for identifying neuron classes. This review presents the neuron types identified so far in the area CA1 of the rat hippocampus with special emphasis on the immunocytochemical characterization of these cells.

Brain Sciences, Nov 13, 2020

Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the ... more Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the development of new therapies, such as deep-brain stimulation (DBS). DBS was applied to different brain regions for patients with epilepsy; however, the mechanisms of action are not fully understood. Therefore, we tried to characterize the effect of amygdala DBS on hippocampal electrical activity in the lithium-pilocarpine model in male Wistar rats. After status epilepticus (SE) induction, seizure patterns were determined based on continuous video recordings. Recording electrodes were inserted in the left and right hippocampus and a stimulating electrode in the left basolateral amygdala of both Pilo and age-matched control rats 10 weeks after SE. Daily stimulation protocol consisted of 4 × 50 s stimulation trains (4-Hz, regular interpulse interval) for 10 days. The hippocampal electroencephalogram was analyzed offline: interictal epileptiform discharge (IED) frequency, spectral analysis, and phase-amplitude coupling (PAC) between delta band and higher frequencies were measured. We found that the seizure rate and duration decreased (by 23% and 26.5%) and the decrease in seizure rate correlated negatively with the IED frequency. PAC was elevated in epileptic animals and DBS reduced the pathologically increased PAC and increased the average theta power (25.9% ± 1.1 vs. 30.3% ± 1.1; p < 0.01). Increasing theta power and reducing the PAC could be two possible mechanisms by which DBS may exhibit its antiepileptic effect in TLE; moreover, they could be used to monitor effectiveness of stimulation.

Orvostudományi Értesítö, Dec 1, 2020

Temporal lobe epilepsy (TLE) is a severe neurological disease which is often pharmacoresistant. D... more Temporal lobe epilepsy (TLE) is a severe neurological disease which is often pharmacoresistant. Deep brain stimulation (DBS) is a novel method for treating epilepsy; however, its mechanism of action is not fully understood. We aimed to study the effect of amygdala DBS in the pilocarpine model of TLE. Status epilepticus was induced by pilocarpine in male Wistar rats, and spontaneous seizures occurred after a latency period. A stimulating electrode was inserted into the left basolateral amygdala and two recording electrodes into the left and right hippocampus. A stimulus package consisted of 0.1 ms-long biphasic pulses applied regularly at 4 Hz for 50 seconds. This package was repeated four times a day, with 5-minute pauses, for 10 days. We also used an age-matched healthy control group of stimulated animals and another one of sham-operated rats. From the hippocampal local field potentials high frequency oscillations (HFOs) were analyzed as these are promising epilepsy biomarkers. HFOs are short oscillatory events between 80-600 Hz which were detected offline using an open-source application of MATLAB, the RIPPLELAB system. We found that the HFO rate was significantly higher in pilocarpine-treated rats compared to the control groups (0.41 ± 0.14 HFO/min vs. 0.006 ± 0.003 in the stimulated control group and no HFO in the sham-operated group). In the pilocarpine group an instantaneous decrease in HFO rate was observed while the stimulation was on (0.44 ± 0.15 HFO/min vs 0.07 ± 0.03 HFO/min, p=0.017). The effect was short-lived because the frequency of HFOs did not change significantly in the time windows between stimulus packages or during the ten-day stimulation period. The difference of HFO rates between epileptic and control groups could be used in the electrographic assessment of epilepsy. The decreased frequency of HFOs during stimulation may be useful to study the efficacy of DBS.

Cells, Mar 1, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Cells, 2021

Temporal lobe epilepsy (TLE) is characterized by changes in interneuron numbers in the hippocampu... more Temporal lobe epilepsy (TLE) is characterized by changes in interneuron numbers in the hippocampus. Deep brain stimulation (DBS) is an emerging tool to treat TLE seizures, although its mechanisms are not fully deciphered. We aimed to depict the effect of amygdala DBS on the density of the most common interneuron types in the CA1 hippocampal subfield in the lithium-pilocarpine model of epilepsy. Status epilepticus was induced in male Wistar rats. Eight weeks later, a stimulation electrode was implanted to the left basolateral amygdala of both pilocarpine-treated (Pilo, n = 14) and age-matched control rats (n = 12). Ten Pilo and 4 control animals received for 10 days 4 daily packages of 50 s 4 Hz regular stimulation trains. At the end of the stimulation period, interneurons were identified by immunolabeling for parvalbumin (PV), neuropeptide Y (NPY), and neuronal nitric oxide synthase (nNOS). Cell density was determined in the CA1 subfield of the hippocampus using confocal microscopy....

Acta Medica Marisiensis, 2014

One of the most frequent forms of epilepsy in humans is temporal lobe epilepsy. Characteristic to... more One of the most frequent forms of epilepsy in humans is temporal lobe epilepsy. Characteristic to this form of the disease is the frequent pharmacoresistance and the association with behavioural disorders and cognitive impairment. The objective of our study was to establish the degree of cognitive impairment in a rat model of temporal lobe epilepsy after an initial epileptogenic exposure but before of the onset of the effect of long-duration epilepsy. Methods. For the experiment we used 11 rats. Status epilepticus was induced by systemic administration of a single dose of pilocarpine. The animals were continuously video-monitored to observe the occurrence of spontaneous recurrent seizures; during weeks 9-10 we performed eight-arm radial maze testing in order to assess the cognitive impairment. Results. Animals developed spontaneous recurrent seizures after a 14-21 day latency with a daily average seizure density of 0.79±0.43 during weeks 9-10. Epileptic rats had significantly more w...

Brain Sciences, 2021

Although Ca2+ ion plays an essential role in cellular physiology, calcium-binding proteins (CaBPs... more Although Ca2+ ion plays an essential role in cellular physiology, calcium-binding proteins (CaBPs) were long used for mainly as immunohistochemical markers of specific cell types in different regions of the central nervous system. They are a heterogeneous and wide-ranging group of proteins. Their function was studied intensively in the last two decades and a tremendous amount of information was gathered about them. Girard et al. compiled a comprehensive list of the gene-expression profiles of the entire EF-hand gene superfamily in the murine brain. We selected from this database those CaBPs which are related to information processing and/or neuronal signalling, have a Ca2+-buffer activity, Ca2+-sensor activity, modulator of Ca2+-channel activity, or a yet unknown function. In this way we created a gene function-based selection of the CaBPs. We cross-referenced these findings with publicly available, high-quality RNA-sequencing and in situ hybridization databases (Human Protein Atlas...

Brain Sciences, 2020

Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the ... more Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the development of new therapies, such as deep-brain stimulation (DBS). DBS was applied to different brain regions for patients with epilepsy; however, the mechanisms of action are not fully understood. Therefore, we tried to characterize the effect of amygdala DBS on hippocampal electrical activity in the lithium-pilocarpine model in male Wistar rats. After status epilepticus (SE) induction, seizure patterns were determined based on continuous video recordings. Recording electrodes were inserted in the left and right hippocampus and a stimulating electrode in the left basolateral amygdala of both Pilo and age-matched control rats 10 weeks after SE. Daily stimulation protocol consisted of 4 × 50 s stimulation trains (4-Hz, regular interpulse interval) for 10 days. The hippocampal electroencephalogram was analyzed offline: interictal epileptiform discharge (IED) frequency, spectral analysis, ...

Acta Marisiensis - Seria Medica, 2021

Objective: The aim of our study was to investigate the effect of amygdala low-frequency stimulati... more Objective: The aim of our study was to investigate the effect of amygdala low-frequency stimulation on inter-hippocampal network synchronization by using the phase locking value (PLV) in order to establish new biomarkers of treatment efficacy in a temporal lobe epilepsy model. Materials and Methods: The lithium-pilocarpine model of epilepsy was used to induce status epilepticus in male Wistar rats. Afterward, seizures were scored based on continuous video recordings. 8 weeks after status epilepticus electrodes were implanted: a stimulating electrode in the left basolateral amygdala and bilaterally two hippocampal recording electrodes in both pilocarpine-treated and age-matched control rats (N=7). 10 Pilo and 4 control animals were stimulated daily for 10 days with 4 packages of 50 seconds 4Hz trains. Inter-hippocampal PLVs were measured offline before and after stimulation trains in delta (1-4Hz), theta (4-12Hz), gamma (30-100Hz), HFO (100-150Hz), ripple (150-250Hz), and fast ripple...

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2016

Multiple Endocrine Neoplasia Type 1 (MEN1) does not involve the thyroid gland, but animal studies... more Multiple Endocrine Neoplasia Type 1 (MEN1) does not involve the thyroid gland, but animal studies have shown that mice with inactivation of menin could develop thyroid pathologies. The objective was to evaluate if the selective inactivation of menin in murine thyroid glands expressing RET÷PTC3 and E7 oncogenes, might induce an increased index of proliferation and a more rapid development of thyroid hyperplasia and÷or tumors. The thyroid glands of 77 mice aged 4-18 months (31 expressing the E7 oncogene and 25 the RET÷PTC3 oncogene) were analyzed for histological changes and Ki67 proliferation index. Fifty-two mice had selective inactivation of menin in the thyroid gland (16 mice with RET÷PTC3 oncogene and 19 mice with E7 oncogene). As compared to wild type, mice with inactivation of menin presented an increased Ki67 proliferation index. Mice presenting the E7 oncogene showed larger thyroid glands with a pattern of diffuse hyperplasia. Mice expressing the RET÷PTC3 oncogene presented l...

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2015

Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's po... more Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's population. Despite advances regarding therapy, about 30% of patients cannot be relieved of seizures, mainly because the pathophysiological mechanisms are still not elucidated completely. Basket, axo-axonic, bistratified, oriens-lacunosum moleculare (O-LM) and Ivy cells exert spatially and temporary different inhibition on principal neurons. Our aim was to evaluate the alterations of these interneuron populations during epileptogenesis. We induced status epilepticus in male Wistar rats using intraperitoneal pilocarpine injection, which was followed, after a latency period, by spontaneous recurrent seizures (SRS). Nissl staining was used for the analysis of gross morphological changes, whereas triple immunofluorescent-labeled sections (parvalbumin, somatostatin, neuropeptide-Y) were used for differentiation of the selected interneuron types. Putative interneurons identified by their neuroch...

The Journal of Physiology, 1997

European Journal of Neuroscience, 2004

The ®rst step in building a realistic computational neuron model is to produce a passive electric... more The ®rst step in building a realistic computational neuron model is to produce a passive electrical skeleton on to which active conductances can be grafted. For this, anatomically accurate morphological reconstructions of the desired cell type are required. In this study compartmental models were used to compare from a functional perspective three on-line archives of rat hippocampal CA1 pyramidal cell morphologies. The topological organization of cells was found to be similar for all archives, but several morphometric differences were observed. The three-dimensional size of the cells, the diameter and tortuosity of dendrites, and the electrotonic length of the main apical dendrite and of the branches in stratum lacunosum moleculare were dissimilar. The experimentally measured kinetics of somatically recorded inhibitory postsynaptic currents evoked in the stratum lacunosum moleculare (data from the literature) could be reproduced only using the archives that contained cells with an electrotonically short main apical dendrite. In the amplitude attenuation of the simulated postsynaptic currents and the voltage escape from the command potential under voltage clamp conditions, a two-to threefold difference was observed among archives. Upon activation of a single model synapse on distal branches, cells with low dendritic diameter showed a voltage escape larger than 15 mV. The diameter of the dendrites in¯uenced greatly the results, emphasizing the importance of methods that allow an accurate measurement of this parameter. Our results indicate that there are functionally signi®cant differences in the morphometric data available in different archives even if the cell type, brain region and species are the same.

Archives of Pharmacal Research, 2015

Antiepileptic drugs act on voltage gated sodium channels in many different ways: rufinamide is th... more Antiepileptic drugs act on voltage gated sodium channels in many different ways: rufinamide is thought to influence the fast inactivation, so its anticonvulsant action could be similar to carbamazepine, whereas lacosamide enhances the slow inactivation; however some antidepressants were also described to act in the same way. Rufinamide, lacosamide, carbamazepine, fluoxetine and imipramine were tested using in vitro models of epileptiform activities. Extracellular local field potentials were recorded using hippocampal slices from immature rats and the pattern of epileptiform activities was analyzed. Seizure-like events (SLE), but not interictal bursts were sensitive to AEDs&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; action. Rufinamide increased interictal periods by prolonging preictal phase and reducing SLE duration, and was the only tested AED which reduced SLE frequency. Lacosamide&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s effect resembled that of fluoxetine in the low-Mg(2+) model: both drugs reduced markedly the SLE duration, but increased their frequency. Imipramine and fluoxetine irreversibly suppressed SLE in all slices. Some proconvulsive type of action on SLEs such as increasing preictal neuronal activity by rufinamide and increasing SLE frequency by lacosamide, fluoxetine and carbamazepine, were also observed. Newer drugs were more efficient than carbamazepine, and the anticonvulsant action of antidepressants on in vitro epileptiform activities may seem somewhat surprising.

Inhibition in the central nervous system is largely mediated by local-circuit neurons that releas... more Inhibition in the central nervous system is largely mediated by local-circuit neurons that release GABA (γ-amino-butyric acid). GABAAreceptors play a major role in virtually all brain physiological functions and serve as targets for numerous classes of drugs, used both in clinical practice and as research tools. These receptors are heteropentamers, α1 being the most widely occurring subunit; therefore it is the best candidate to be studied in pathological conditions where the inhibitory system might be altered (e.g. epilepsy). We compared quantitatively the regional distribution of GABAA-receptor α1-subunit (GABAAR-α1) expression in three brain areas: neocortex, hippocampus and cerebellum by RT-qPCR. TaqMan probe was used in order to avoid detection of non-specific amplification products and synaptophysin as internal control. This substance was chosen because it has a stable expression restricted to neurons, and contrary to GAPDH, the most commonly used reference gene for expression analysis, synaptophysin expression is not modified in animal models of epilepsy. Expression of synaptophysin was higher than expression of GABAAR-α1 in all samples from the central nervous system. The latter was significantly different among the studied brain areas. It was the smallest in the hippocampus, intermediate in the neocortex and the highest in the cerebellum. Interanimal differences were small for any brain region under study. These results indicate that combination of TaqMan real-time PCR method with synaptophysin as internal control can reliably measure the relative expression of GABAAR-α1 mRNA, and are suitable for investigating the modifications that appear under pathological conditions and/or diverse experimental paradigms.

Temporal lobe epilepsy (TLE) is one of the therapy-resistant forms of epileptic syndromes. Variou... more Temporal lobe epilepsy (TLE) is one of the therapy-resistant forms of epileptic syndromes. Various mechanisms of action and potential drug target sites were discovered, but major progress was not achieved in combating pharmacoresistance. Newer antiepileptic drugs (AEDs) – rufinamide and lacosamide – are suspected to act on voltage gated sodium channels in a different manner than classic sodium channel blockers: by prolonging the recovery from sustained inactivation of Na+ channels or by accelerating the process of entry into the slow inactivated state, respectively. These distinct mechanisms brought some chance to uncover efficient drugs in pharmacoresistant TLE. To test our hypothesis, drugs were applied in an in vitro model of low Mg2+induced recurrent seizure, which can be considered the model of pharmacoresistant epilepsy as the evoked seizure like events (SLE) are resistant to the majority of classical AEDs. Hippocampal slice preparations obtained from P7-P13 male Wistar rats w...

Acta Medica Marisiensis, 2014

Objective. Epilepsy is a neurological disorder that can be caused by many underlying pathologies.... more Objective. Epilepsy is a neurological disorder that can be caused by many underlying pathologies. The epileptic and interictal manifestations that appear during the progression of chronic epilepsy are still not understood completely. One of the most frequent forms of this disease is temporal lobe epilepsy in which is clear involvement of the hippocampal formation. In order to study the electrografic progression of untreated seizures we used amygdala kindling in freely moving rats. Methods. Seven animals were implanted with bilateral hippocampal and prefrontal electrodes. A bipolar electrode, implanted in the lateral nuclei of the left amygdala was used for stimulation. The kindled group of animals was stimulated daily with the minimum current intensity needed to reach the afterdischarge threshold. Behavioral changes during kindling were scored according to the Racine scale. Results. The average seizure severity on the Racine scale was 2.6±0.4 by day 6 and 4.4±0.6 by day 20. The firs...

Aims: The main purpose of the study was the development of a specific and precise method for the ... more Aims: The main purpose of the study was the development of a specific and precise method for the quantification of different third generation antiepileptic drugs to evaluate their specific pharmacokinetic properties – tissue distribution, blood-brain-barrier passing rate – during concomitent use. A rapid and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed for rufinamide and lacosamide in various plasma samples and validated according to the current bioanalytical guidelines. Materials and methods: The separation was conducted on a reversed phase column (Zorbax SB-C18 100 x 3 mm, 3.5 µm), the mobile phase consisting of methanol and 0.1% formic acid in water (50:50 v/v) at 40 ºC with a flow rate of 0.3 mL/min. The detection of the analytes was performed with an Agilent G6410A Triple Quad mass spectrometer in multiple reaction monitoring mode (MRM) using a positive electrospray ionization. The mass transitions monitored were m/z 239→...

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2011

The cerebral cortex ensures an optimal interaction of mammals, including humans, with their envir... more The cerebral cortex ensures an optimal interaction of mammals, including humans, with their environment, by encoding, storing and combining information about the surrounding world and the internal milieu. Probably the simplest and the most popular region for studying the cortical network is the hippocampal CA1 area, because it has the least heterogeneous neuronal population, the somata and dendrites of principal neurons (pyramidal cells) are arranged into well defined layers and the extrinsic and intrinsic inputs are segregated. The relatively homogeneous pyramidal cell population is supported by a very heterogeneous GABAergic interneuron population, which provides not only general inhibition, but also regulates the precise timing of pyramidal cell activity. Interneurons usually innervate distinct domains of the surface of their target cell. The strategic placement of inhibitory synapses, indicate that GABAergic interneurons belonging to different classes serve distinct functions in...

PubMed, 2015

Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's popula... more Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's population. Despite advances regarding therapy, about 30% of patients cannot be relieved of seizures, mainly because the pathophysiological mechanisms are still not elucidated completely. Basket, axo-axonic, bistratified, oriens-lacunosum moleculare (O-LM) and Ivy cells exert spatially and temporary different inhibition on principal neurons. Our aim was to evaluate the alterations of these interneuron populations during epileptogenesis. We induced status epilepticus in male Wistar rats using intraperitoneal pilocarpine injection, which was followed, after a latency period, by spontaneous recurrent seizures (SRS). Nissl staining was used for the analysis of gross morphological changes, whereas triple immunofluorescent-labeled sections (parvalbumin, somatostatin, neuropeptide-Y) were used for differentiation of the selected interneuron types. Putative interneurons identified by their neurochemical contents were quantified, and the cell density was calculated. Although animals developing SRS showed similar behavior, the degree of hippocampal sclerosis was different. In animals with hippocampal sclerotic cell death pattern the density of perisomatic inhibitory neurons was higher, but not significantly. The dendritic inhibitory bistratified cells were preserved, whereas the number of O-LM cells showed a significant decrease. A substantial loss was observed in the number and density of Ivy cells. We suggest that the loss of hippocampal input modulatory O-LM cells, and overall excitation controlling Ivy cells, has a role in the emergence of hyperexcitability. In the same time, alterations of output controlling interneurons might contribute to the propagation of the pathological synchronization to the cortex.

Romanian Journal of Morphology and Embryology, 2011

The cerebral cortex ensures an optimal interaction of mammals, including humans, with their envir... more The cerebral cortex ensures an optimal interaction of mammals, including humans, with their environment, by encoding, storing and combining information about the surrounding world and the internal milieu. Probably the simplest and the most popular region for studying the cortical network is the hippocampal CA1 area, because it has the least heterogeneous neuronal population, the somata and dendrites of principal neurons (pyramidal cells) are arranged into well defined layers and the extrinsic and intrinsic inputs are segregated. The relatively homogeneous pyramidal cell population is supported by a very heterogeneous GABAergic interneuron population, which provides not only general inhibition, but also regulates the precise timing of pyramidal cell activity. Interneurons usually innervate distinct domains of the surface of their target cell. The strategic placement of inhibitory synapses, indicate that GABAergic interneurons belonging to different classes serve distinct functions in the hippocampal network. Neuron types are usually defined according to various morphological, molecular and physiological features. Under typical experimental conditions only some of these parameters are available, therefore an important scientific question is: which partial measures are sufficient for correct recognition of a class of cell. By immunohistochemistry it is possible to stain all neurochemically identical neurons in a given brain region, therefore it is the most widely used method for identifying neuron classes. This review presents the neuron types identified so far in the area CA1 of the rat hippocampus with special emphasis on the immunocytochemical characterization of these cells.

Brain Sciences, Nov 13, 2020

Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the ... more Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the development of new therapies, such as deep-brain stimulation (DBS). DBS was applied to different brain regions for patients with epilepsy; however, the mechanisms of action are not fully understood. Therefore, we tried to characterize the effect of amygdala DBS on hippocampal electrical activity in the lithium-pilocarpine model in male Wistar rats. After status epilepticus (SE) induction, seizure patterns were determined based on continuous video recordings. Recording electrodes were inserted in the left and right hippocampus and a stimulating electrode in the left basolateral amygdala of both Pilo and age-matched control rats 10 weeks after SE. Daily stimulation protocol consisted of 4 × 50 s stimulation trains (4-Hz, regular interpulse interval) for 10 days. The hippocampal electroencephalogram was analyzed offline: interictal epileptiform discharge (IED) frequency, spectral analysis, and phase-amplitude coupling (PAC) between delta band and higher frequencies were measured. We found that the seizure rate and duration decreased (by 23% and 26.5%) and the decrease in seizure rate correlated negatively with the IED frequency. PAC was elevated in epileptic animals and DBS reduced the pathologically increased PAC and increased the average theta power (25.9% ± 1.1 vs. 30.3% ± 1.1; p < 0.01). Increasing theta power and reducing the PAC could be two possible mechanisms by which DBS may exhibit its antiepileptic effect in TLE; moreover, they could be used to monitor effectiveness of stimulation.

Orvostudományi Értesítö, Dec 1, 2020

Temporal lobe epilepsy (TLE) is a severe neurological disease which is often pharmacoresistant. D... more Temporal lobe epilepsy (TLE) is a severe neurological disease which is often pharmacoresistant. Deep brain stimulation (DBS) is a novel method for treating epilepsy; however, its mechanism of action is not fully understood. We aimed to study the effect of amygdala DBS in the pilocarpine model of TLE. Status epilepticus was induced by pilocarpine in male Wistar rats, and spontaneous seizures occurred after a latency period. A stimulating electrode was inserted into the left basolateral amygdala and two recording electrodes into the left and right hippocampus. A stimulus package consisted of 0.1 ms-long biphasic pulses applied regularly at 4 Hz for 50 seconds. This package was repeated four times a day, with 5-minute pauses, for 10 days. We also used an age-matched healthy control group of stimulated animals and another one of sham-operated rats. From the hippocampal local field potentials high frequency oscillations (HFOs) were analyzed as these are promising epilepsy biomarkers. HFOs are short oscillatory events between 80-600 Hz which were detected offline using an open-source application of MATLAB, the RIPPLELAB system. We found that the HFO rate was significantly higher in pilocarpine-treated rats compared to the control groups (0.41 ± 0.14 HFO/min vs. 0.006 ± 0.003 in the stimulated control group and no HFO in the sham-operated group). In the pilocarpine group an instantaneous decrease in HFO rate was observed while the stimulation was on (0.44 ± 0.15 HFO/min vs 0.07 ± 0.03 HFO/min, p=0.017). The effect was short-lived because the frequency of HFOs did not change significantly in the time windows between stimulus packages or during the ten-day stimulation period. The difference of HFO rates between epileptic and control groups could be used in the electrographic assessment of epilepsy. The decreased frequency of HFOs during stimulation may be useful to study the efficacy of DBS.

Cells, Mar 1, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Cells, 2021

Temporal lobe epilepsy (TLE) is characterized by changes in interneuron numbers in the hippocampu... more Temporal lobe epilepsy (TLE) is characterized by changes in interneuron numbers in the hippocampus. Deep brain stimulation (DBS) is an emerging tool to treat TLE seizures, although its mechanisms are not fully deciphered. We aimed to depict the effect of amygdala DBS on the density of the most common interneuron types in the CA1 hippocampal subfield in the lithium-pilocarpine model of epilepsy. Status epilepticus was induced in male Wistar rats. Eight weeks later, a stimulation electrode was implanted to the left basolateral amygdala of both pilocarpine-treated (Pilo, n = 14) and age-matched control rats (n = 12). Ten Pilo and 4 control animals received for 10 days 4 daily packages of 50 s 4 Hz regular stimulation trains. At the end of the stimulation period, interneurons were identified by immunolabeling for parvalbumin (PV), neuropeptide Y (NPY), and neuronal nitric oxide synthase (nNOS). Cell density was determined in the CA1 subfield of the hippocampus using confocal microscopy....

Acta Medica Marisiensis, 2014

One of the most frequent forms of epilepsy in humans is temporal lobe epilepsy. Characteristic to... more One of the most frequent forms of epilepsy in humans is temporal lobe epilepsy. Characteristic to this form of the disease is the frequent pharmacoresistance and the association with behavioural disorders and cognitive impairment. The objective of our study was to establish the degree of cognitive impairment in a rat model of temporal lobe epilepsy after an initial epileptogenic exposure but before of the onset of the effect of long-duration epilepsy. Methods. For the experiment we used 11 rats. Status epilepticus was induced by systemic administration of a single dose of pilocarpine. The animals were continuously video-monitored to observe the occurrence of spontaneous recurrent seizures; during weeks 9-10 we performed eight-arm radial maze testing in order to assess the cognitive impairment. Results. Animals developed spontaneous recurrent seizures after a 14-21 day latency with a daily average seizure density of 0.79±0.43 during weeks 9-10. Epileptic rats had significantly more w...

Brain Sciences, 2021

Although Ca2+ ion plays an essential role in cellular physiology, calcium-binding proteins (CaBPs... more Although Ca2+ ion plays an essential role in cellular physiology, calcium-binding proteins (CaBPs) were long used for mainly as immunohistochemical markers of specific cell types in different regions of the central nervous system. They are a heterogeneous and wide-ranging group of proteins. Their function was studied intensively in the last two decades and a tremendous amount of information was gathered about them. Girard et al. compiled a comprehensive list of the gene-expression profiles of the entire EF-hand gene superfamily in the murine brain. We selected from this database those CaBPs which are related to information processing and/or neuronal signalling, have a Ca2+-buffer activity, Ca2+-sensor activity, modulator of Ca2+-channel activity, or a yet unknown function. In this way we created a gene function-based selection of the CaBPs. We cross-referenced these findings with publicly available, high-quality RNA-sequencing and in situ hybridization databases (Human Protein Atlas...

Brain Sciences, 2020

Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the ... more Temporal-lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and warrants the development of new therapies, such as deep-brain stimulation (DBS). DBS was applied to different brain regions for patients with epilepsy; however, the mechanisms of action are not fully understood. Therefore, we tried to characterize the effect of amygdala DBS on hippocampal electrical activity in the lithium-pilocarpine model in male Wistar rats. After status epilepticus (SE) induction, seizure patterns were determined based on continuous video recordings. Recording electrodes were inserted in the left and right hippocampus and a stimulating electrode in the left basolateral amygdala of both Pilo and age-matched control rats 10 weeks after SE. Daily stimulation protocol consisted of 4 × 50 s stimulation trains (4-Hz, regular interpulse interval) for 10 days. The hippocampal electroencephalogram was analyzed offline: interictal epileptiform discharge (IED) frequency, spectral analysis, ...

Acta Marisiensis - Seria Medica, 2021

Objective: The aim of our study was to investigate the effect of amygdala low-frequency stimulati... more Objective: The aim of our study was to investigate the effect of amygdala low-frequency stimulation on inter-hippocampal network synchronization by using the phase locking value (PLV) in order to establish new biomarkers of treatment efficacy in a temporal lobe epilepsy model. Materials and Methods: The lithium-pilocarpine model of epilepsy was used to induce status epilepticus in male Wistar rats. Afterward, seizures were scored based on continuous video recordings. 8 weeks after status epilepticus electrodes were implanted: a stimulating electrode in the left basolateral amygdala and bilaterally two hippocampal recording electrodes in both pilocarpine-treated and age-matched control rats (N=7). 10 Pilo and 4 control animals were stimulated daily for 10 days with 4 packages of 50 seconds 4Hz trains. Inter-hippocampal PLVs were measured offline before and after stimulation trains in delta (1-4Hz), theta (4-12Hz), gamma (30-100Hz), HFO (100-150Hz), ripple (150-250Hz), and fast ripple...

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2016

Multiple Endocrine Neoplasia Type 1 (MEN1) does not involve the thyroid gland, but animal studies... more Multiple Endocrine Neoplasia Type 1 (MEN1) does not involve the thyroid gland, but animal studies have shown that mice with inactivation of menin could develop thyroid pathologies. The objective was to evaluate if the selective inactivation of menin in murine thyroid glands expressing RET÷PTC3 and E7 oncogenes, might induce an increased index of proliferation and a more rapid development of thyroid hyperplasia and÷or tumors. The thyroid glands of 77 mice aged 4-18 months (31 expressing the E7 oncogene and 25 the RET÷PTC3 oncogene) were analyzed for histological changes and Ki67 proliferation index. Fifty-two mice had selective inactivation of menin in the thyroid gland (16 mice with RET÷PTC3 oncogene and 19 mice with E7 oncogene). As compared to wild type, mice with inactivation of menin presented an increased Ki67 proliferation index. Mice presenting the E7 oncogene showed larger thyroid glands with a pattern of diffuse hyperplasia. Mice expressing the RET÷PTC3 oncogene presented l...

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2015

Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's po... more Epilepsy is a frequent neurological disorder that affects directly 0.5-1.5% of the world's population. Despite advances regarding therapy, about 30% of patients cannot be relieved of seizures, mainly because the pathophysiological mechanisms are still not elucidated completely. Basket, axo-axonic, bistratified, oriens-lacunosum moleculare (O-LM) and Ivy cells exert spatially and temporary different inhibition on principal neurons. Our aim was to evaluate the alterations of these interneuron populations during epileptogenesis. We induced status epilepticus in male Wistar rats using intraperitoneal pilocarpine injection, which was followed, after a latency period, by spontaneous recurrent seizures (SRS). Nissl staining was used for the analysis of gross morphological changes, whereas triple immunofluorescent-labeled sections (parvalbumin, somatostatin, neuropeptide-Y) were used for differentiation of the selected interneuron types. Putative interneurons identified by their neuroch...

The Journal of Physiology, 1997

European Journal of Neuroscience, 2004

The ®rst step in building a realistic computational neuron model is to produce a passive electric... more The ®rst step in building a realistic computational neuron model is to produce a passive electrical skeleton on to which active conductances can be grafted. For this, anatomically accurate morphological reconstructions of the desired cell type are required. In this study compartmental models were used to compare from a functional perspective three on-line archives of rat hippocampal CA1 pyramidal cell morphologies. The topological organization of cells was found to be similar for all archives, but several morphometric differences were observed. The three-dimensional size of the cells, the diameter and tortuosity of dendrites, and the electrotonic length of the main apical dendrite and of the branches in stratum lacunosum moleculare were dissimilar. The experimentally measured kinetics of somatically recorded inhibitory postsynaptic currents evoked in the stratum lacunosum moleculare (data from the literature) could be reproduced only using the archives that contained cells with an electrotonically short main apical dendrite. In the amplitude attenuation of the simulated postsynaptic currents and the voltage escape from the command potential under voltage clamp conditions, a two-to threefold difference was observed among archives. Upon activation of a single model synapse on distal branches, cells with low dendritic diameter showed a voltage escape larger than 15 mV. The diameter of the dendrites in¯uenced greatly the results, emphasizing the importance of methods that allow an accurate measurement of this parameter. Our results indicate that there are functionally signi®cant differences in the morphometric data available in different archives even if the cell type, brain region and species are the same.

Archives of Pharmacal Research, 2015

Antiepileptic drugs act on voltage gated sodium channels in many different ways: rufinamide is th... more Antiepileptic drugs act on voltage gated sodium channels in many different ways: rufinamide is thought to influence the fast inactivation, so its anticonvulsant action could be similar to carbamazepine, whereas lacosamide enhances the slow inactivation; however some antidepressants were also described to act in the same way. Rufinamide, lacosamide, carbamazepine, fluoxetine and imipramine were tested using in vitro models of epileptiform activities. Extracellular local field potentials were recorded using hippocampal slices from immature rats and the pattern of epileptiform activities was analyzed. Seizure-like events (SLE), but not interictal bursts were sensitive to AEDs&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; action. Rufinamide increased interictal periods by prolonging preictal phase and reducing SLE duration, and was the only tested AED which reduced SLE frequency. Lacosamide&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s effect resembled that of fluoxetine in the low-Mg(2+) model: both drugs reduced markedly the SLE duration, but increased their frequency. Imipramine and fluoxetine irreversibly suppressed SLE in all slices. Some proconvulsive type of action on SLEs such as increasing preictal neuronal activity by rufinamide and increasing SLE frequency by lacosamide, fluoxetine and carbamazepine, were also observed. Newer drugs were more efficient than carbamazepine, and the anticonvulsant action of antidepressants on in vitro epileptiform activities may seem somewhat surprising.

Inhibition in the central nervous system is largely mediated by local-circuit neurons that releas... more Inhibition in the central nervous system is largely mediated by local-circuit neurons that release GABA (γ-amino-butyric acid). GABAAreceptors play a major role in virtually all brain physiological functions and serve as targets for numerous classes of drugs, used both in clinical practice and as research tools. These receptors are heteropentamers, α1 being the most widely occurring subunit; therefore it is the best candidate to be studied in pathological conditions where the inhibitory system might be altered (e.g. epilepsy). We compared quantitatively the regional distribution of GABAA-receptor α1-subunit (GABAAR-α1) expression in three brain areas: neocortex, hippocampus and cerebellum by RT-qPCR. TaqMan probe was used in order to avoid detection of non-specific amplification products and synaptophysin as internal control. This substance was chosen because it has a stable expression restricted to neurons, and contrary to GAPDH, the most commonly used reference gene for expression analysis, synaptophysin expression is not modified in animal models of epilepsy. Expression of synaptophysin was higher than expression of GABAAR-α1 in all samples from the central nervous system. The latter was significantly different among the studied brain areas. It was the smallest in the hippocampus, intermediate in the neocortex and the highest in the cerebellum. Interanimal differences were small for any brain region under study. These results indicate that combination of TaqMan real-time PCR method with synaptophysin as internal control can reliably measure the relative expression of GABAAR-α1 mRNA, and are suitable for investigating the modifications that appear under pathological conditions and/or diverse experimental paradigms.

Temporal lobe epilepsy (TLE) is one of the therapy-resistant forms of epileptic syndromes. Variou... more Temporal lobe epilepsy (TLE) is one of the therapy-resistant forms of epileptic syndromes. Various mechanisms of action and potential drug target sites were discovered, but major progress was not achieved in combating pharmacoresistance. Newer antiepileptic drugs (AEDs) – rufinamide and lacosamide – are suspected to act on voltage gated sodium channels in a different manner than classic sodium channel blockers: by prolonging the recovery from sustained inactivation of Na+ channels or by accelerating the process of entry into the slow inactivated state, respectively. These distinct mechanisms brought some chance to uncover efficient drugs in pharmacoresistant TLE. To test our hypothesis, drugs were applied in an in vitro model of low Mg2+induced recurrent seizure, which can be considered the model of pharmacoresistant epilepsy as the evoked seizure like events (SLE) are resistant to the majority of classical AEDs. Hippocampal slice preparations obtained from P7-P13 male Wistar rats w...

Acta Medica Marisiensis, 2014

Objective. Epilepsy is a neurological disorder that can be caused by many underlying pathologies.... more Objective. Epilepsy is a neurological disorder that can be caused by many underlying pathologies. The epileptic and interictal manifestations that appear during the progression of chronic epilepsy are still not understood completely. One of the most frequent forms of this disease is temporal lobe epilepsy in which is clear involvement of the hippocampal formation. In order to study the electrografic progression of untreated seizures we used amygdala kindling in freely moving rats. Methods. Seven animals were implanted with bilateral hippocampal and prefrontal electrodes. A bipolar electrode, implanted in the lateral nuclei of the left amygdala was used for stimulation. The kindled group of animals was stimulated daily with the minimum current intensity needed to reach the afterdischarge threshold. Behavioral changes during kindling were scored according to the Racine scale. Results. The average seizure severity on the Racine scale was 2.6±0.4 by day 6 and 4.4±0.6 by day 20. The firs...

Aims: The main purpose of the study was the development of a specific and precise method for the ... more Aims: The main purpose of the study was the development of a specific and precise method for the quantification of different third generation antiepileptic drugs to evaluate their specific pharmacokinetic properties – tissue distribution, blood-brain-barrier passing rate – during concomitent use. A rapid and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed for rufinamide and lacosamide in various plasma samples and validated according to the current bioanalytical guidelines. Materials and methods: The separation was conducted on a reversed phase column (Zorbax SB-C18 100 x 3 mm, 3.5 µm), the mobile phase consisting of methanol and 0.1% formic acid in water (50:50 v/v) at 40 ºC with a flow rate of 0.3 mL/min. The detection of the analytes was performed with an Agilent G6410A Triple Quad mass spectrometer in multiple reaction monitoring mode (MRM) using a positive electrospray ionization. The mass transitions monitored were m/z 239→...

Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie, 2011

The cerebral cortex ensures an optimal interaction of mammals, including humans, with their envir... more The cerebral cortex ensures an optimal interaction of mammals, including humans, with their environment, by encoding, storing and combining information about the surrounding world and the internal milieu. Probably the simplest and the most popular region for studying the cortical network is the hippocampal CA1 area, because it has the least heterogeneous neuronal population, the somata and dendrites of principal neurons (pyramidal cells) are arranged into well defined layers and the extrinsic and intrinsic inputs are segregated. The relatively homogeneous pyramidal cell population is supported by a very heterogeneous GABAergic interneuron population, which provides not only general inhibition, but also regulates the precise timing of pyramidal cell activity. Interneurons usually innervate distinct domains of the surface of their target cell. The strategic placement of inhibitory synapses, indicate that GABAergic interneurons belonging to different classes serve distinct functions in...