Azam Asgari; Saeed Semnanian; Nafiseh Atapour; Amir Shojaee; Vahid Sheybani; Seyyed Javad Mirnajafi Zadeh
Volume 23, Issue 2 , March and April 2016, , Pages 290-303
Abstract
Background and purpose: Low frequency stimulation (LFS) has anticonvulsant effect. However, its mechanism of action has not been completely determined. In the present study the effect of LFS on evoked inhibitory post synaptic GABAergic currents (eIPSC) is investigated in CA1 pyramidal neurons of the ...
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Background and purpose: Low frequency stimulation (LFS) has anticonvulsant effect. However, its mechanism of action has not been completely determined. In the present study the effect of LFS on evoked inhibitory post synaptic GABAergic currents (eIPSC) is investigated in CA1 pyramidal neurons of the hippocampus in kindled rats. Materials and Methods: In this experimental study animals were kindled through electrical stimulation of amygdala. 24 hours following fully kindling achievement in 20 Wistar rats, the effect of LFS on eIPSCs was assessed in hippocampal slices. Results: Obtained results showed that application of LFS at 200 pulses and at the intensity of 1.5 threshold, increased the amplitude and decay time constant of eIPSCs in both control and kindled rats. When 200 pulses of LFS were administered with an intensity equal to threshold, only eIPSC amplitude was increased in both control and kindled groups significantly (P<0.001). Comparing the effectiveness of LFS on control and kindled groups showed that 200 pulses of LFS at the intensity of 1.5 threshold had higher effect in control than kindled group (P<0.001). Conclusion: Results of the present study showed that LFS application increased eIPSCs parameters in a pulse number and intensity dependent manner. This increment can be considered as a possible anticonvulsant mechanism of LFS.
Homeyra Moradi Chameh; Saeed Semnanian; Mahyar Jan Ahmadi; Amir Shojaee; Azam Asgari; Seyyed Javad Mirnajafizadeh
Volume 22, Issue 4 , September and October 2015, , Pages 649-659
Abstract
Background & Objectives: Amygdala kindling is accompanied with alteration of the electrophysiological characteristics of pyramidal cells in CA1 area of hippocampus. However, it is not clear that when and in which seizure stage do these changes occur during kindling. In the present study, changes ...
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Background & Objectives: Amygdala kindling is accompanied with alteration of the electrophysiological characteristics of pyramidal cells in CA1 area of hippocampus. However, it is not clear that when and in which seizure stage do these changes occur during kindling. In the present study, changes in the electrophysiological properties of hippocampal CA1 pyramidal neurons following partial amygdala kindling in rats were compared to full kindled state. Materials & Methods: Animals were rapidly kindled by 1 ms square waves, 50 Hz, for 3 s. These stimulations were applied to the amygdala 12 times per day at 5 min intervals. Animal received kindling stimulation until achieving stage 2 (partial kindled group) and stage 5 (full kindled group). 24 hours after the last kindling stimulation electrophysiological properties of CA1 pyramidal neurons were assessed by using whole-cell patch clamp technique. Results: Obtained data from amygdala kindling showed that adaptation index, Rheobase, utilization time and the amplitude of afterhyperpolarization potential in partial kindled and full kindled compare to control were significantly decreased and the numbers of action potentials were significantly increased. Conclusion: The present findings showed that in spite of in partial amygdala kindling, the number of stimulations that rats will receive is lower than full kindled animal but it can change neuronal hyperexcitability through alteration of the electrophysiological characteristics.
SeyyedJavad Mirnajafizadeh; Yaghob Fattollahi; Amir Shojaee; Azam Asgari; Fatemeh Rostami
Volume 21, Issue 5 , September and October 2014, , Pages 951-959
Abstract
Background and purpose: Nowadays repeated transcranial magnetic stimulation (rTMS) is being used as a treatment for some neurological disorders, but its effect on neuronal activity and synaptic plasticity has not been completely determined. The purpose of this study was to evaluate the effect of chronic ...
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Background and purpose: Nowadays repeated transcranial magnetic stimulation (rTMS) is being used as a treatment for some neurological disorders, but its effect on neuronal activity and synaptic plasticity has not been completely determined. The purpose of this study was to evaluate the effect of chronic rTMS on the ability of synaptic plasticity.
Materials and Methods: rTMS was applied to the hippocampal region for 14 days. One week following termination of rTMS, the amount of synaptic long-term potentiation (LTP) in animals was investigated and compared with control group. High-frequency stimulation (HFS) was applied to the perforant path for LTP induction, andfield potentials were recorded from granular layer of the dentate gyrus. Baseline field potential was recorded 10 minutes before HFS. An increase of at least 20% in population spike amplitude was measured as an index of synaptic potentiation.To compare the effects of rTMS on measured parameters, we used t-test and two way ANOVA followed by Benferroni test (Prism 8 software).
Results: Obtained data showed that, following 14 days of rTMS application causeda reduction in population spike amplitude compared to the control group (P
Amir Shojaee; Vahid Sheybani; Khadijeh Esmaeel pour; Yaser Masoumi; Seyyed Javad Mirnajafizadeh
Volume 20, Issue 4 , January and February 2014, , Pages 496-504
Abstract
Background: Low frequency stimulation (LFS) has been recently suggested as an antiepileptic method in treating the drug-resistant epileptic syndromes such as temporal lobe epilepsy. So far, in the most clinical and experimental studies, LFS has been applied to the seizure focus itself. Considering the ...
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Background: Low frequency stimulation (LFS) has been recently suggested as an antiepileptic method in treating the drug-resistant epileptic syndromes such as temporal lobe epilepsy. So far, in the most clinical and experimental studies, LFS has been applied to the seizure focus itself. Considering the role of dentate gyrus in spreading of the limbic seizures, in the present study the effect of LFS of dentate gyrus on amygdala kindling-induced seizures was investigated.
Materials and methods: To kindle the animals, using stereotaxic instrument, a tripolar electrode was inserted into right basolateral area of amygdala and a bipolar electrode was ipsilaterally placed in dentate gyrus of male Wistar rats. After a 10 days recovery period, animals divided into two groups. The animals of kindled group were received daily electrical stimulations. In kindled+LFS group, LFS was delivered to dentate gyrus 1 min after cessation of amygdala kindling stimulation. The maximum seizure stage and duration of afterdischarges were evaluated after kindling stimulation. The effect of LFS on behavioral seizure stages and afterdischarges was compared using Kruskall Wallis and repeated measures 2-way AVOVA. A P value less than 0.05 was considered as significant level.
Results: The required time to achieve a stage 5 seizure was 12 days in kindled group animals. However, animals of kindled+LFS group did not show more than stage 2 seizure following 12 days of stimulation. LFS of dentate gyrus significantly prevented the increment of behavioral seizure stages and afterdischarge duration in kindled-LFS group compared with kindled group.
Conclusion: The results of this study demonstrated that application of LFS in the dentate gyrus can be an effective therapeutic method for controlling the amygdala kindling-induced seizures. Furthermore, this study provide further evidences showing LFS of brain areas involved in spreading the seizures, other than seizure focus can have anticonvulsant affect.
Mohammad Javan; Seyyed Javad Mirnajafizadeh; Maryam Zeraati; Simin Namvar
Volume 17, Issue 3 , September and October 2010, , Pages 158-169
Abstract
Background and Purpose: Despite widespread research on epilepsy, the mechanism of its insidnece is still unknown. Since the activity of ATPase plays a vital role in changing ATP into AMP, and this substance can later turn into adenosine which is the most important endogenous anticonvulsant agent in brain, ...
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Background and Purpose: Despite widespread research on epilepsy, the mechanism of its insidnece is still unknown. Since the activity of ATPase plays a vital role in changing ATP into AMP, and this substance can later turn into adenosine which is the most important endogenous anticonvulsant agent in brain, the effect of inhibition of ATPase on perforant path kindling was investigated in the present study. Methods and Materials: In this experimental study, animals were kindled by electrical stimulations of the perforant path (12 times a day with a frequency of 50 Hz and pulse duration of 1 millisecond). Upon kindling, behavioral and electrophysiologic measures of convulsions and filed potentials were recorded. For investigating the role of ATPase in animal groups, FPL 67156 was injected as the inhibitor of the ATPase after kindling stimulations ended each day. Kindled animals were 6, and there were 4 rats in other groups. Repeated measures ANOVA and Bonferoni test were used to compare the statistical quantities of fEPSP and PS of epilepsy creation in different groups of the study. Comparing the difference of paired pulses between groups was conducted by Bonferoni test. The five-stage convulsion of the groups was compared through Kruskall Wallis and Mann Whitney U tests. Statistical analyses were conducted in Prism 5. Results: The results indicated that ATPase inhibition (by injecting FPL 67156) causes no change in various behavioral stages of convulsion and daily afterdischarge duration following kindling (P>0.05); however, it affects synapsis formation, so that PS increases in comparison with the kindled group (P
Seyyed Javad Mirnajafizadeh; Ali Jahanshahi Anvar; Yosef Sadeghi; Raziyeh Rohani; Abbas Piriayi; Maryam Zeraati
Volume 17, Issue 2 , July and August 2010, , Pages 96-107
Abstract
Background and Purpose: Application of low-frequency stimulation (LFS) induces anticonvulsant effects. In this study, the effect of changes in LFS frequencies on its anticonvulsant effects in kindling model of epilepsy was investigated by determining the behavioral and ultrastructural changes. Methods ...
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Background and Purpose: Application of low-frequency stimulation (LFS) induces anticonvulsant effects. In this study, the effect of changes in LFS frequencies on its anticonvulsant effects in kindling model of epilepsy was investigated by determining the behavioral and ultrastructural changes. Methods and Materials: In this experimental study, 45 Wistar rats weighing 250-280 g were used. For induction of kindled seizures, stimulating and recording electrodes were implanted in perforant path and dentate gyrus respectively. Animals were stimulated in a rapid kindling manner. Different groups of animals received LFS at different frequencies (0.5, 1 and 5 Hz) following kindling stimulations and their effects on kindling rate were determined using behavioral and electrophysiological studies. After stimulating the animals for 7 days, they were killed and their dentate gyri were sampled for ultrastructural studies under electron microscopy. For data analysis, one-way and two-way ANOVA, LSD, Kruskal Wallis and Mann Whitney U were used in Statistica 2. Results: Different LFS frequencies had a significant inhibitory effect on kindling rate and decreased after-discharge duration and the number of stimulations to achieve stage 4 and 5 seizures significantly. In addition, application of LFS prevented the increase in the post-synaptic density and induction of concave synaptic vesicles following kindling. There was not any significant change between anticonvulsant effects of LFS at different frequencies. Conclusion: Obtained results show that LFS application can prevent the neuronal hyper-excitability by preventing the ultrastructural changes during kindling, and can exert its anticonvulsant effects.
Mohammad Javan; Seyyed Javad Mirnajafizadeh; Mehdi Godarznavd; Taghi Tarihi
Volume 16, Issue 2 , July and August 2009, , Pages 62-71
Abstract
Background and purpose: Antioxidants and vitamin D3 are currently used for the treatment of neurodegenerative diseases although their mechanism of action is not well understood. The present study was conducted to investigate the effect of combined administration of vitamins D3 and E on demyelination ...
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Background and purpose: Antioxidants and vitamin D3 are currently used for the treatment of neurodegenerative diseases although their mechanism of action is not well understood. The present study was conducted to investigate the effect of combined administration of vitamins D3 and E on demyelination cell death and remyelination of rat hippocampus following the local ethidium bromide (EB) injection. Methods and Materials: This experimental study was conducted on 32 Spague rats. After EB-induced demyelination animals received intraperitoneal vitamin E (100 mg/kg) and D3 (5µg/kg) together for 7 days. The extent and intensity of demyelination were studied by luxol fats blue staining the activated caspase-3 genes and MBP. The study data were analyzed in SPSS using one-way ANOVA and Tukey post test. Results: The findings revealed that the combined administration of vitamins E and D3 for 7 days caused a significant reduction in the expression of activated caspase-3 (10±0) (p
Seyyed Javad Mirnajafizadeh; Mohammad Mohammadzadeh
Volume 15, Issue 3 , September and October 2008, , Pages 129-137
Abstract
Background and Purpose: Previous studies have not properly clarified the role of A2A adenosine receptors in convulsions induced by kindling. In the present study the role of these receptors in convulsions induced perforant path kindling has been investigated by blocking these receptors (with specific ...
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Background and Purpose: Previous studies have not properly clarified the role of A2A adenosine receptors in convulsions induced by kindling. In the present study the role of these receptors in convulsions induced perforant path kindling has been investigated by blocking these receptors (with specific antagonists). Methods and Materials: This experimental study was conducted on 24 rats which were randomly divided into four groups of six. They were kindled by electric stimulation of the perforant path. In two groups before each kindling stimulation antagonists of A2A adenosine receptors (ZM 241385) (500 and 200 µM) was injected to the lateral ventricle of the rats. Control animals were given only the electric stimulations. In the fourth group (sham) the solvent of the abovementioned drug was injected to the lateral ventricle before kindling stimulations. The obtained data were analyzed using two-way ANOVA and Tukey tests. Results: Injecting the antagonists of A2A adenosine receptors (ZM 241385) (500 µM) to the lateral ventricle of the rats postponed the process of kindling. Two-way ANOVA indicated that number of stimulations required to reach the convulsive stages were significantly increased (P