Introduction: The hippocampus was recognized as an important focus of epileptic seizures. A long-term potentiation (LTP) like that of epileptiform activities is considered as synaptic which has been observed for the first time in hippocampal formation. The purpose of the present study was investigate the synaptic plasticity induced by tetanic stimulation at CA1 area of the rat hippocampal slices that were susceptible to epileptic seizures. Materials and Methods: Epileptiform activities in these slices were induced by the application of pentylenetetrazol (PTZ, 3mM) for 20 miniutes. Neural activity in the form of population spikes in pyramidal cell of CA1 area was recorded before and after tetanic stimulation r PTZ application. Input-output curves of amplitude and delay of population spikes were used to find out changes in synaptic efficacy. Results: Twenty minutes after PTZ application, and five minutes after tetanic stimulation (in control group), input-output curves had shifted to the left and the shift remained for at least 60 minutes after PTZ washout or tetanic stimulation. PTZ application also led to the appearance of after potentials which maintained for about 30 minutes after PTZ washout. The increase of population spike amplitude induced by tetanic stimulation, in PTZ-treated slices was lower than that of the control one, but the difference between the control and PTZ treated slices was not significant. In addition, to that potentials appeared in PTZ-treated slices following the tetanic stimulation. Conclusion: The results indicate that PTZ administration for 20 minutes is after sufficient to make up a stable model of epileptic activity. PTZ, like the LTP induced by tetanic stimulation, shifts the input-output curve to the left. Potentiation resulted from LTP was not occluded by the prior PTZ. Therefore, to induce the epileptic activity, a background of potentiation in neural activity is necessary.

Kindling epileptigenesis was induced by repeated administrations of the chemical convulsant pentylenetetrazol (PTZ).The progressive nature of the chemical kindling was demonstrated by a detailed description of the behavioral sings in the course of the kindling acquistion. The Changes of Paired-Pulse Index (PPI) were primariliy investigated with extracellular recording in stratum pyramidale following stimulation of Schaffer collaterals in the CA1 region of hippocampus of the PTZ-Kindled and the control rats. The results were as follow:(1) in most of the kindled rats the first stimulus evoked a double population spike at moderate and high stimulus .intensities:(2) 40-100 hours after the kindling no significant difference was observed between the control and the kindled rats, and (3) 30-33 days after the kindling PPI was increased in the kindled rats at IPI of 10 and 20 ms with low and moderate stimulus intensities as compared with the control ones. It seems that an increase in PPI may be resulted from an enhancement of excitatory synaptic transmission and/or an increase in intrinsic excitability of pyramidal neurons of hippocampal CAI.

Introduction: The effectiveness of θ-pattern primed-burst (PBs) for the induction of long-term potentiation (LTP) of population excitatory postsynaptic potential (pEPSP) and population spikes (PS) were investigated in hippocampal CA1 of pentylenetetrazol-kindled rats. Materials and Methods: Experiments were carried out in the control and kindled animals. Field potentials (pEPSP and PS) were recorded at stratum radiatum and stratum pyramidale following stimulation of the stratum fibers, respectively. PBs was delivered to stratum fibers and PB potentiation was assessed. Results: The results showed that 48-144 h after kindling PB potentiation in stratum radiatum of kindled animals was not significantly changed compared to controls. In stratum pyramidale PBs induced LTP in control animals but not in kindled ones. Conclusion: The effect is compatible with the hypothesis that postulate kindling associated functional deficit in hippocampus, especially CA1, as an explanation for the behavioral deficits seen with the kindling model of epilepsy.      

Background: Since, 30-40 percent of epileptic patient din’t reponse to current therapy or be low responsive patient after long-term treatment, then finding of new drug paradigms is necessarily. Recently, some studies indicated about sex steroids that modulate GABA activity, that is the aim of this study to determine the effect of estradiol and progestrone on chemical epilepsy in rats. Material and Methods: This experimental study was performed on 60 male rats and randomizely divided in to six group (one control group and five experimental groups). In all groups, rats kindeled by pentylene tetrazol (PTZ) kindling model. In this modle rats received PTZ (50 mg/kg) ip once at 48 hours for 12 sessions. In experimental groups. Rats received vehicle or progestrone (25, 50 mg/kg) or stradiol valorate (5, 10mg/kg) 20 min before PTZ injection and serizure stages were measured for 20 min. Results: Our results indicated that, PTZ injection increased the average of seizure stage and in final injection, 71.43% of rats shows the five stage of seisure. Stradiol don’t significant effect on seizure stages but it clinically increased the mortality rate (P<0.05). whreas, progestrone significantly decreased the seizure stages development (P<0.01) and mortality (P<0.05). Conclusion: finally, we conclude that progesterone attenuate the seizure stages, development stradiol increased the mortality rate during seizure.

Melissa officinalis is a well known medicinal plant. Different studies performed in mice have shown the sedative, hypnotic, analgesic, antiviral and antimicrobial effects of this plant. The present investigation was undertaken to evaluate the effect of percolated extract of this plant against lethal seizure induced by intraregional injection of pentylentetrazole (PTZ) in wistar rats. The study was performed on three groups of animals pretreated with different doses of extract via intraperitonal injection. After 30 minutes each animal received high dose of PTZ (90 mg/kg) for induction of lethal seizure. The control group received normal saline. In addition a positive control group pretreated with diazepam, a well known drug in the treatment of seizure, was used for comparison. The efficacy of the extract to protect the animals against lethal seizure was based on the latency of the appearance of the first sign of seizure or the latency of the different epileptic manifestations and decrease of mortality rate in each group. The results showed that various epileptic manifestations are delayed in diazepam pretreated animals and extract compared with control group. The dose of 50 mg/kg of the extract appeared to be significantly effective on the tremors and the myoclonic jerks of epileptic manifestations (P<0.05). In addition the mortality rate was significantly reduced in pretreated animals with this dose compared with control group (P<0.05). Mortality rate was 88% in saline group, 13% in 50mggroup and zero percent in diazepam group. The results indicated. that the extract of Melissa officinalis possesses anticonvulsant property.

Introduction: Pentylenetetrazol (PTZ) is one of the most often used epileptogenic agents. Several effects of this epileptogenic drug have been described, but the mechanism of the epileptogenic action of PTZ at the cellular level is still unclear. In this study the effect of PTZ, on the ionic currents of D5 neuronal soma membrane in Helixaspersa, using intracellular recording technique was investigated.Materials and Methods: Experiments were carried out on D5 neuronal soma membrane located in the left parietal ganglion of the snail, Helix aspersa. The properties of the inward and outward cationic currents induced by PTZ (25 mM) were analyzed using two electrodes voltage clamp technique. Results: The extracellular application of PTZ (25 mM), caused an increase in spontaneous firing activity and with 4 to 7 minutes after adding PTZ, led to a dramatic changes in action potential shape of D5 neuronal cells. Under voltage clamp condition, the peak amplitude of inward current in the presence of PTZ reduced 16.5 % within 7 min. The current-voltage relationship of inward current also shifted by 23.18 % in a hyperpolarizing direction. Furthermore, the peak amplitude of outward currents showed a reduction of about 6.75%. Conclusion: The results of this study show that PTZ by effecting on the properties of bioelectrical activity causes an increase in the excitability of D5 cells. In addition, the effect of PTZ on inward and outward currents accounts for an induction of epileptic activity.

Introduction: Epilepsy is one of the most common neurological disorders. In spite of the fact that a great development has been made regarding therapy against epilepsy, little is known, however, about the precise mechanism of the epilepsy. Pentylenetetrazol (PTZ) is one of the most often used epileptogenic agents. Hence the main purpose of the present work was to determine the effect of PTZ as a convulsant drug on the bioelectrical activity and neuronal excitability of D5 neurone in Helix aspersa. Materials and Methods: Experiments were carried out on D5 neuronal soma membrane located in the left parietal ganglion of snail, Helix aspersa. The properties of the action potentials were analyzed using two electrodes current clamp technique.Results: The results showed that the injection of 1 nA depolarizing current in the presence of PTZ caused an increase in the frequency and the duration of action potentials by about 11.7% and 14% respectively. It also led to a 32.3% decrease in the amplitude of afterhyperpolarization and the amplitude of action potential by about 2-3mV. Furthermore when PTZ (25 mM) was applied extracellularly, the resting membrane potential of the D5 cell became hyperpolarized by about 4 mV. Conclusion: These findings suggest that PTZ induces changes in bioelectrical properties which effect on neuronal signaling.