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 ...
Read More
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 ...
Read More
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 ...
Read More
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 ...
Read More
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.