Nurbay Ates

Amygdala Kindling in the WAG/Rij Rat Model of Absence Epilepsy

Summary:  Purpose: The kindling model in rats with genetic absence epilepsy is suitable for studying mechanisms involved in the propagation and generalization of seizure activity in the convulsive and nonconvulsive components of epilepsy. In the present study, we compared the amygdala kindling rate and afterdischarge characteristics of the nonepileptic Wistar control rat with a well‐validated model of absence epilepsy, the WAG/Rij rat, and demonstrated the effect of amygdala kindling on spike‐and‐wave discharges (SWDs) in the WAG/Rij group.

The Effect of Generalized Absence Seizures on the Progression of Kindling in the Rat

Summary:  The involvement of the thalamus in limbic epileptogenesis has recently drawn attention to the connectivity between the nuclei of the thalamus and limbic structures. Thalamo‐limbic circuits are thought to regulate limbic seizure activity whereas thalamocortical circuits are involved in the expression and generation of spike‐and‐wave discharges (SWDs) in the absence epilepsy models. Genetic Absence Epilepsy Rats From Strasbourg (GAERS) and WAG/Rij (Wistar Albino Glaxo from Rijswijk) are well‐defined genetic animal models of absence epilepsy. We aimed to examine the duration of behavioral changes in the kindling process and the relation of SWD activity to the kindling progress in the GAERS and WAG/Rij animals. Electrodes were stereotaxically implanted into the basolateral amygdala and the cortex of rats for stimulation and recording. The animals were stimulated at the threshold for producing afterdischarges. EEG was recorded to analyze SWDs and afterdischarge durations. The seizure severity was evaluated using Racines 5‐stage scale. None of the GAERS animals reached stage 3, 4, or 5 after application of 30 stimulations. The WAG/Rij animals showed different rate of kindling, therefore they were further categorized into the kindling‐resistant, slow‐kindled, and rapid‐kindled groups. The kindling‐resistant animals demonstrated a significantly longer duration of SWDs on the first day of the experiment before kindling stimulation and shorter duration of afterdischarge than did the kindled WAG/Rij animals. Behavioral durations at stage 2 were longer in kindled Wistar and WAG/Rij animals compared to kindling‐resistant WAG/Rij and GAERS. These results suggest that mechanisms involved in the generation of SWDs act as a counterbalance to the excitability induced by kindling.

Electroencephalographic differences between WAG/Rij and GAERS rat models of absence epilepsy

The inbred Wistar Albino Glaxo Rats from Rijswijk (WAG/Rij) and the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) are well-validated genetic models of absence epilepsy. Although they share similar characteristics including the spike-and-wave discharges (SWDs) in the EEG, some differences have been reported between both strains. This study aimed a systematic and detailed comparison of the SWD patterns of both strains in terms of the intensity, frequency and waveform morphology of the discharges by using exactly the same measurement and analysis techniques. The number, cumulative total duration and mean duration of SWDs were significantly higher in GAERS compared to WAG/Rij, while the discharge frequency was higher in the WAG/Rij. Furthermore, SWDs spectra and average SWD waveforms indicated that a single cycle of the SWD contains more energy in faster components such as spike and late positive transient in the GAERS. Additionally, WAG/Rij exhibited a significantly higher power between 8 and 14 Hz during the pre-SWD period. These clear phenomenological differences in the EEGs of both animal models suggest that these variables may represent basic phenotypic features of SWDs that should be sought after in the future studies that explore the genetic and molecular basis of absence epilepsy.

Changes in the blood–brain barrier permeability and in the brain tissue trace element concentrations after single and repeated pentylenetetrazole-induced seizures in rats

The behaviour of brain capillary endothelium to the passage of macromolecules in single and repeated seizures conditions and its relationship to the brain trace element concentrations are the main subject of this study. For this purpose, animals were treated with either single or repeated doses of pentylenetetrazole (PTZ). As a marker of blood-brain barrier (B-BB) permeability changes, Evans Blue (EB) dye was used. Seizure activity was observed and seizure patterns and convulsion times were recorded. PTZ treatment induced generalised tonic-clonic seizure in all animals, but seizures were found to be lasting longer in single seizure group than repeated seizures group. Seizures induced by single dose PTZ treatment resulted in bilateral EB leakage in the preoptic area, caudate nucleus, putamen, thalamus, hypothalamus, midbrain, and the superior colliculus. However, repeated PTZ-induced seizures led to EB leakage in the brains of only few number of rats, and it was confined to hypothalamus, caudate nucleus, cerebellum, thalamus, and pons. On the other hand, while the levels of copper (Cu) and iron (Fe) in brain tissue were found to be decreased significantly in the repeated seizures group when compared with the other groups, the levels of zinc (Zn) did not show any differences between groups. These results indicate that the regional B-BB opening markedly differs between single and repeated PTZ-induced seizures group and this difference may be due to PTZ tolerance and changes in cerebral endothelial structure.

Changes in blood-brain barrier permeability during hot water-induced seizures in rats

Abstract.Hot water epilepsy (HWE) was induced in freely moving Wistar rats by applying hot water jets over the head region. The status of the blood-brain barrier (BBB) during the seizures and during hot water-induced hyperthermia without seizures was examined using Evans blue dye. In order to investigate the contribution of concomitant factors to this process, synchronized body temperature and blood pressure recordings were also made. Tonic-clonic seizure activity was observed within an average of 3.9 min (SE=0.6 min) in the rats exposed to the hot water jets; this treatment induced BBB opening in the cortical and deep brain areas. Body temperature and blood pressure increased from 36.5°±0.3°C to 40.0°±0.2°C, and from 91±3 mmHg to 153±4 mmHg, respectively. In the group of animals exposed to hot water application without inducing seizures, there were significant increases both in blood pressure and body temperature; however, the extravasation of Evans blue was not pronounced in the brains. Hot water-induced seizures, increased cerebrovascular permeability. Although high blood pressure and hyperthermia contribute to this permeability, the seizure activity is the major factor in this change.

Effect of pentylenetetrazole and sound stimulation induced single and repeated convulsive seizures on the MDA, GSH and NO levels, and SOD activities in rat liver and kidney tissues

OBJECTIVES the aim of our study was to evaluate the activity of superoxide dismutase (SOD) and the levels of glutathione (GSH), malondialdehyde (MDA), and nitric oxide (NO) in liver and kidney tissues in a rat model of convulsive seizure induced by single and repeated doses of pentylenetetrazole (PTZ) and sound stimulation with key ringing. MATERIALS AND METHODS male Wistar adult rats (n=48), were used in the experiment. The animals were divided into six groups: (1) Single Seizure Control Group (SS-Control; n=8), (2) Repeated Seizures Control Group (RS-Control; n=8), (3) PTZ induced Single Seizure Group (SS-PTZ Group; n=8), (4) PTZ induced Repeated Seizures Group (RS- PTZ Group; n=8), (5) Key-Ringing Induced Single Seizure Group (SS-KEY Group; n=8), (6) Key-Ringing Induced Repeated Seizures Group (RS-KEY Group; n=8). Following injections rats were observed for seizure activity for 30 min. Animals were sacrificed 24h after induced seizure (single or last seizure) or saline administration. MDA, NO, GSH levels and SOD activities were determined in liver and kidney tissues. RESULTS there was no significant difference between SS-Control and RS-Control groups, SS-PTZ and SS-KEY groups, and RS-PTZ and RS-KEY groups (p>0.05) in none of the examined 4 parameters in liver and kidney tissues. The liver and kidney levels of MDA and NO in SS-PTZ group were found to be significantly higher than the SS-Control group (p<0.05). In SS-KEY group, the liver and kidney levels of MDA and NO were found to be significantly higher and GSH levels were significantly lower than the SS-Control group (p<0.05). While liver and kidney levels of MDA in RS-PTZ group and RS-KEY group were found to be significantly higher than the RS-Control group (p<0.05), liver and kidney GSH levels were significantly lower (p<0.05). The liver levels of NO in RS-PTZ group and RS-KEY group were found to be significantly higher than the RS-Control group (p<0.05). Kidney SOD activities in RS-PTZ group and RS-KEY group were found to be significantly lower than the RS-Control group (p<0.05). When RS-PTZ group is compared with the SS-PTZ group, the liver SOD activity and kidney NO level were found to be significantly lower in the RS-PTZ group (p<0.05). While the liver NO level and GSH level in RS-KEY group were significantly higher than the SS-KEY group, SOD activity was significantly lower in the RS-KEY group (p<0.05). When RS-KEY group was compared with SS-KEY group, the kidney NO level and SOD activity were found to be significantly lower in the RS-KEY group (p<0.05). CONCLUSION in conclusion, key-ringing or PTZ induced single and repeated seizures result in increased oxidative damage and lipid peroxidation, and decreased antioxidant defense mechanisms.

The effect of memantine in harmaline-induced tremor and neurodegeneration

Essential tremor (ET) is one of the most common and most disabling movement disorders among adults. The drug treatment of ET remains unsatisfactory. Additional therapies are required for patients with inadequate response or intolerable side effects. The current study aims to investigate the anti-tremogenic and neuroprotective effects of memantine (NMDA receptor antagonist) on the harmaline model of transient action tremor. The effects of memantine were further compared with ethanol. Three separate groups of male Wistar rats were injected either with saline, ethanol (1.5 gr/kg), or memantine (5 mg/kg) 15 min prior to a single intraperitoneal injection of harmaline (20 mg/kg). Tremor and locomotion were evaluated by a custom-built tremor and locomotion analysis system. After 24 h of harmaline injection, cellular viability, and apoptosis were assessed using crystal violet staining, and caspase-3 immunostaining, respectively. Harmaline caused neuronal cell loss and caspase-3 mediated apoptosis in cerebellar granular and purkinje cells as well as the inferior olivary neurons. Despite a reduction in tremor intensity and duration with ethanol, this compound resulted in cell loss in cerebellum and olivary nucleus. Memantine exhibited neuroprotective efficacy on cerebellar and inferior olivary neurons albeit weaker anti-tremor effect compared to ethanol. In conclusion, anti-tremogenic and neuroprotective effects do not necessarily overlap. Memantine is a potential treatment for ET particularly given its neuroprotective efficacy.

Hippocampal kindling in rats with absence epilepsy resembles amygdaloid kindling

PURPOSE WAG/Rij and GAERS rats show delays or resistance to secondary generalization of limbic seizures during amygdaloid kindling. In this study, we aimed to evaluate the kindling from a different limbic site, hippocampus, and to compare its effects on spike-and-wave discharges (SWDs) with that of amygdaloid kindling. METHODS Recording electrodes were implanted epidurally and a stimulation/recording electrode was implanted into the ventral hippocampus in the WAG/Rij, GAERS and Wistar rats. Animals received kindling stimulation twice daily at their afterdischarge thresholds until they reached stage 5 seizures, or the maximum number of stimulations (50) had been delivered. The EEG was recorded to analyze SWDs and afterdischarge durations. RESULTS All Wistar rats reached stage 5 by the 34th stimulation. 4 of 8 WAG/Rij rats and 3 of 6 GAERS rats displayed stage 4/5 seizures (kindling-prone rats); the rest stayed at stage 2 seizures (kindling-resistant rats) even after 50th stimulations. The cumulative duration and number of SWDs decreased in the post-stimulation period after the first stage 2 seizures, whereas these parameters increased after the first stage 3 seizures in the kindling-prone WAG/Rij and GAERS. The peak frequency of SWDs and its harmonics decreased significantly only in the GAERS group after stage 4 seizures. CONCLUSION Hippocampal kindling resembles amygdaloid kindling in showing a delay of or resistance to secondary seizure generalization, which supported the interaction of thalamo-cortical and limbic circuitry in GAERS and WAG/Rij.

Effects of adenosine administration on spike‐wave discharge frequency in genetically epileptic rats

1. In the present study, the effects of the administration of adenosine on absence seizures were investigated in the Wistar Albino Glaxo/Rijswijk (WAG/Rij) strain of rats, which are an adequate model for human absence epilepsy.

Theophylline, a methylxanthine derivative, suppresses absence epileptic seizures in WAG/Rij rats

The effects of systemic theophylline administration on spike-wave discharge (SWD) frequency in genetically absence epileptic Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats are investigated. After an hour of baseline recording, animals were injected intraperitoneally (ip) with 5, 10, and 20mg/kg theophylline and electroencephalograms (EEGs) were recorded for 2h postinjection. Then, the number and total duration of SWDs were analyzed. Spontaneous behaviors of the animals was also observed before and after drug administration. Our results show that systemic administration of theophylline suppresses the occurrence of SWDs in a dose-dependent manner. The greatest suppression was seen in the group administered 20mg/kg theophylline. Theophylline also induced a mild increase in exploratory and automatic behavior. These results indicate that blockage of adenosinergic receptors via the methylxanthine derivative theophylline decreases the occurrence of SWDs, probably by augmenting the efficacy of excitator neurotransmission and increasing vigilance and arousal levels.