Person: ONAT, FİLİZ
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ONAT
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FİLİZ
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Publication Metadata only The relationship between age-related development of spike-and-wave discharges and the resistance to amygdaloid kindling in rats with genetic absence epilepsy(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2008) ONAT, FİLİZ; Carcak, Nihan; Aker, Rezzan Guelhan; Oezdemir, Osman; Demiralp, Tamer; Onat, Filiz YilmazGenetic Absence Epilepsy Rats from Strasbourg (GAERS) are resistant to amygdaloid kindling. Since in GAERS the characteristics of spike-and-wave discharges (SWDs) change with age, we have studied the relation between SWD maturation and the development of kindling resistance. Non-epileptic Wistar rats and GAERS were stimulated in basolateral amygdala with 400 mu A at 20 min intervals until they reached stage 5 seizures or for a maximum of 36 stimulations. All of the Wistar rats, the postnatal (PN) day 20 GAERS and the (kindling-prone) subgroups of GAERS at PN30 and PN60 reached stage 5 seizures; at PN20, PN30 and PN60 kindling rates were significantly slower in GAERS compared to Wistar rats. At PN30 and PN60, 41% and 69% of GAERS, respectively, showed no stage 3, 4 or 5 seizures after 36 stimulations (kindling-resistant subgroups). The SWD maturation involves changes in spectral patterns and correlate with age-related increases in kindling resistance in GAERS. (C) 2008 Elsevier Inc. All rights reserved.Publication Metadata only Seizure expression, behavior, and brain morphology differences in colonies of Genetic Absence Epilepsy Rats from Strasbourg(WILEY, 2014) ONAT, FİLİZ; Powell, Kim L.; Tang, Howard; Ng, Caroline; Guillemain, Isabelle; Dieuset, Gabriel; Dezsi, Gabi; Carcak, Nihan; Onat, Filiz; Martin, Benoit; O'Brien, Terence J.; Depaulis, Antoine; Jones, Nigel C.ObjectiveOriginally derived from a Wistar rat strain, a proportion of which displayed spontaneous absence-type seizures, Genetic Absence Epilepsy Rats from Strasbourg (GAERS) represent the most widely utilized animal model of genetic generalized epilepsy. Here we compare the seizure, behavioral, and brain morphometric characteristics of four main GAERS colonies that are being actively studied internationally: two from Melbourne (MELB and STRAS-MELB), one from Grenoble (GREN), and one from Istanbul (ISTAN). MethodsElectroencephalography (EEG) recordings, behavioral examinations, and structural magnetic resonance imaging (MRI) studies were conducted on GAERS and Non-Epileptic Control (NEC) rats to assess and compare the following: (1) characteristics of spike-and-wave discharges, (2) anxiety-like and depressive-like behaviors, and (3) MRI brain morphology of regions of interest. ResultsSeizure characteristics varied between the colonies, with MELB GAERS exhibiting the least severe epilepsy phenotype with respect to seizure frequency, and GREN GAERS exhibiting four times more seizures than MELB. MELB and STRAS-MELB colonies both displayed consistent anxiety and depressive-like behaviors relative to NEC. MELB and GREN GAERS showed similar changes in brain morphology, including increased whole brain volume and increased somatosensory cortical width. A previously identified mutation in the Cacna1h gene controlling the Ca(V)3.2 T-type calcium channel (R1584P) was present in all four GAERS colonies, but absent in all NEC rats. SignificanceThis study demonstrates differences in epilepsy severity between GAERS colonies that were derived from the same original colony in Strasbourg. This multi-institute study highlights the potential impact of environmental conditions and/or genetic drift on the severity of epileptic and behavioral phenotypes in rodent models of epilepsy.Publication Metadata only Suppressive effect of Rho-kinase inhibitors Y-27632 and fasudil on spike-and-wave discharges in genetic absence epilepsy rats from Strasbourg (GAERS)(SPRINGER, 2018) ONAT, FİLİZ; Carcak, Nihan; Yavuz, Melis; Karamahmutoglu, Tugba Eryigit; Kurt, Akif Hakan; Kucuk, Meral Urhan; Onat, Filiz Yilmaz; Buyukafsar, KansuRho/Rho-kinase (ROCK) signaling contributes to neuroinflammation, epileptogenesis, and seizures in convulsive-type epilepsies. However, this pathway has not been investigated in absence epilepsy. We investigated RhoA activity in genetic absence epilepsy rats from Strasburg (GAERS) and the effects of ROCK inhibitors Y-27632 and fasudil on spike-and-wave discharges (SWDs) of GAERS. ROCK level and activity were measured by Western blot analysis in the brain areas involved in absence seizures (i.e., cortex and thalamus) and hippocampus. Male GAERS were stereotaxically implanted with bilateral cortical electrodes for electroencephalogram (EEG) recordings and/or guide cannula into the right ventricle. ROCK inhibitors were administered by intraperitoneal injection (1-10mg/kg for Y-27632 or fasudil) or intracerebroventricular injection (7-20nmol/5l for Y-27632 or 10-100nmol/5l for fasudil). EEG was recorded under freely moving conditions. Compared with Wistar rats, GAERS exhibited increased RhoA activity in the somatosensory cortex but not in the thalamus or hippocampus. The single systemic administration of Y-27632 and fasudil partially suppressed the duration and frequency of absence seizure, respectively. However, local brain administration caused a widespread suppressive effect on the total seizure duration, number of seizures, and the average individual seizure length. In summary, Rho/ROCK signaling may be involved in the pathophysiology of absence epilepsy. Furthermore, ROCK inhibitors can control the expression of absence seizure in GAERS, thus indicating that Y-27632 and fasudil have the potential to be used as novel anti-absence drugs.Publication Open Access Effects of Probiotic Consumption on Absence Seizures(KARE PUBL, 2017) ONAT, FİLİZ; Akkol, Serdar; Dogan, Mehmet Can; Esenkar, Duygu; Dogan, Handan; Karamahmutoglu, Tugba; Onat, FilizObjectives: Probiotics are microorganisms of intestinal microflora that are beneficial for human health. Childhood absence epilepsy has 2 validated rat models: Genetic Absence Epilepsy Rats from Strasbourg (GAERS) and Wistar Albino Glaxo from Rijswijk (WAG/Rij). To date, there have been no clinical or experimental studies of the effects of probiotics on absence epilepsy. The present study was an investigation of the effects of probiotics on absence seizures in the GAERS rat model. Methods: GAERS were used to examine the effects of probiotics. Nine male GAERS were assigned to 1 of 2 groups (probiotic or control). The animals had free access to food and water. Commercially available probiotic product was provided in drinking water to probiotic group for 1 month. Surface electrodes were then implanted for electroencephalogram (EEG) recordings. Two aspects of EEG recordings were compared: cumulative duration and cumulative number of absence seizures. Results: Analysis of spike-and-wave discharges between the 2 groups showed no significant difference in either cumulative duration or number (p>0.05). Additionally, it was observed that probiotic group consumed more water than control group (p<0.05). Conclusion: Results indicated that probiotic consumption had no effect on duration or number of spike-and-wave discharges of GAERS after 1-month feeding period. This is the first investigation in the literature addressing interactions between probiotics and absence epilepsy, and further research is needed.Publication Metadata only Comparing glutamatergic neuron population in the mediodorsal thalamic nucleus of genetic absence epilepsy rats from strasbourg (GAERS) and normal control Wistar rats(ELSEVIER SCIENCE BV, 2016) ONAT, FİLİZ; Cavdar, Safiye; Ozgur, Merve; Kirazli, Ozlem; Karahuseyinoglu, Sercin; Onat, FilizAn imbalance between GABAergic inhibition and glutamatergic excitation is suspected to play a role in the genesis of epileptic processes. In the present study we quantified the number of glutamate+ve neurons in the mediodorsal thalamic nucleus (MD) of genetic absence epilepsy rats from Strasbourg (GAERS) and compared these with values for normal Wistar rats. The MD thalamic nucleus was removed from each animal and the glutamatergic neurons were labelled using light-microscopy glutamate immunohistochemistry. The disector method was used to quantify the glutamate+ve neurons in the MD thalamic nucleus of GAERS and Wistar rats. The data were statistically analyzed. In the Wistar animals glutamate+ve neurons formed 89% and in GAERS 92.3% of the total neurons in 1000 mu m(3) of MD thalamic nucleus. In GAERS glutamate+ve neurons showed statistically significant increase in the MD thalamic nucleus compared to Wistar animals. In Wistar animals the glutamate-ve neurons formed 11% and in GAERS 7.7% of the total neurons in 1000 mu m(3) of MD thalamic. No significant difference was observed in glutamate ye neurons between the two strains. The average diameter of glutamate-ve neurons showed no significance, while glutamate-ve neurons were significant between the two strains. The results of the present study, on genetic absence epilepsy model, GAERS, confirms the role of MD thalamic nucleus in chemically induced absence epilepsy. (C) 2016 Elsevier B.V. All rights reserved.Publication Open Access Effect of stage 2 kindling on local cerebral blood flow rates in rats with genetic absence epilepsy(WILEY, 2009-01) ONAT, FİLİZ; Carcak, Nihan; Ferrandon, Arielle; Koning, Estelle; Aker, Rezzan Guelhan; Oezdemir, Osman; Onat, Filiz Yilmaz; Nehlig, AstridGenetic absence epilepsy rats from Strasbourg (GAERS) are resistant to the progression of kindling seizures. We studied local cerebral blood flow (LCBF) changes in brain regions involved in seizures in both GAERS and nonepileptic rats (NEC) to map the differences that may be related to the resistance to kindling. Electrodes were implanted in the amygdala of adult NEC and GAERS male rats, which were stimulated to reach stage 2. Quantitative autoradiographic measurements of LCBF were performed by the [C-14]-iodoantipyrine ([C-14]IAP) autoradiographic technique allowing the precise mapping of regional perfusion changes. LCBF rates were measured bilaterally in 43 brain regions. The tracer infusion lasted for 60 s and started at 15 s before seizure induction. Rates of LCBF increased in stimulated GAERS and NEC groups compared to nonstimulated controls. The LCBF increase in stimulated GAERS was larger and more widespread than that observed in stimulated NEC. The LCBF increase in the somatosensory cortex, ventrobasal and anterior thalamic nuclei, hypothalamus, subthalamic nucleus, piriform, entorhinal and perirhinal cortex, amygdala, CA2 region of hippocampus, and substantia nigra was statistically significantly larger in stimulated GAERS compared to stimulated NEC rats. The results show that more brain regions are activated by kindling stimulation in GAERS. This widespread activation in GAERS involves the somatosensory cortex and thalamus, which are both known to be involved in the expression of absence seizures as well as numerous limbic regions thought not to play a role in the expression of absence seizures, suggesting an interaction between corticothalamocortical and limbic circuitries.Publication Metadata only Atipamezole, a specific alpha(2A) antagonist, suppresses spike-and-wave discharges and alters Ca2+/calmodulin-dependent protein kinase II in the thalamus of genetic absence epilepsy rats(WILEY, 2020) AYDIN OMAY, BANU; Yavuz, Melis; Aydin, Banu; Carcak, Nihan; Akman, Ozlem; Raci Yananli, Hasan; Onat, FilizObjective The role of alpha(2A) adrenergic receptors (alpha(2A)ARs) in absence epilepsy is not well characterized. Therefore, we investigated the outcomes of the specific antagonism of alpha(2A)ARs on the spike-and-wave discharges (SWDs) in genetic absence epilepsy rats from Strasbourg (GAERSs), together with its influence on the behavior and second messenger systems, which may point to the mechanisms to which a possible SWD modulation can be related. Methods Atipamezole, an alpha(2A)AR antagonist, was administered intracerebroventricularly to the adult GAERSs, and electroencephalography (EEG) was conducted. The cumulative duration and number of SWDs, and the mean duration of each SWD complex were counted. The relative power of the EEG frequency bands and behavioral activity after the acute application of two doses (12 and 31 mu g/5 mu L) of atipamezole were evaluated. The levels of cyclic adenosine monophosphate and calcium/calmodulin-dependent kinase II (CaMKII) were measured in the cortex, thalamus, and hippocampus of naive Wistar rats and GAERSs, administered with artificial cerebrospinal fluid (aCSF) as a vehicle, or either acute or chronic atipamezole (12 mu g), the latter being administered for 5 consecutive days. Results Atipamezole significantly suppressed SWDs dose-dependently, without affecting the relative power values of EEG frequency spectrum. The stereotypic activity was significantly lower in both naive Wistar rats and GAERSs receiving the highest dose (31 mu g) of atipamezole compared to GAERSs receiving aCSF. In GAERSs, CaMKII levels were found to be higher in the thalamus after the acute and chronic application of SWD-suppressing doses of atipamezole (12 and 31 mu g) compared to aCSF. Significance This study emphasizes the alpha(2)AR-related modulation of absence epilepsy and particularly the significance of alpha(2)AR antagonism in suppressing SWDs. Atipamezole's SWD-suppressive actions may be through CaMKII-mediated second messenger systems in the thalamus.Publication Metadata only GABA(A) receptor mediated transmission in the thalamic reticular nucleus of rats with genetic absence epilepsy shows regional differences: Functional implications(ELSEVIER SCIENCE BV, 2006) ONAT, FİLİZ; Aker, Rezzan Gulhan; Ozyurt, Hazan B.; Yananli, Hasan R.; Cakmak, Yusuf Ozgur; Ozkaynakci, Aydan E.; Sehirli, Umit; Saka, Erdinc; Cavdar, Safiye; Onat, Filiz YimazThe aim of the present study was to investigate the effect of local injections of the GABA(A) receptor antagonist, bicuculline, into the rostral and caudal parts of the thalamic reticular nucleus (TRN), on the generation of spike-and-wave discharges in Genetic Absence Epilepsy Rats from Strasbourg (GAERS). Spike-and-wave discharges are important in the pathophysiology of absence epilepsy and generated by the cortico-thalamo-cortical pathway, where GABA has a significant role, particularly in the TRN. Artificial cerebrospinal fluid or bicuculline was administered to rostral or caudal parts of TRN of GAERS through a stereotaxically placed guide cannula. Administration of bicuculline produced opposite effects according to the injection site. Administration into the caudal TRN produced statistically significant increases in the duration of spike-and-wave discharges, whereas injections into the rostral TRN produced significant decreases. Correspondingly, distinct patterns of afferent connections have been demonstrated with the wheat-germ-agglutinin horseradish peroxidase (WGA-HRP) retrograde tracing method in control non-epileptic rats and GAERS for the rostral and caudal parts of the TRN. Injection of WGA-HRP tracer showed no detectable difference regarding the rostral and caudal connections between GAERS and Wistar animals. Rostral parts of TRN have thalamic and cortical connections that are primarily motor and limbic whereas for the caudal parts these connections are primarily sensory. Further, the rostral parts receive inputs from the substantia nigra pars reticularis and the ventral pallidum that the caudal part lacks. The extent to which these connectional differences may be responsible for the functional differences demonstrated by the bicucculine injections remains to be explored. (c) 2006 Elsevier B.V. All rights reserved.Publication Metadata only Ultrastructural GABA immunogold labeling in the substantia nigra pars reticulata of kindled genetic absence epilepsy rats(TAYLOR & FRANCIS INC, 2020) AKAKIN, DİLEK; Sirvanci, Serap; Akakin, Dilek; Idrizoglu, Medine Gulcebi; Kaya, Ozlem Tugce; Karamahmutoglu, Tugba; Asik, Zehra Nur Turgan; Onat, FilizGenetic Absence Epilepsy Rats from Strasbourg (GAERS) is a well-known animal model of absence epilepsy and they are resistant to electrical kindling stimulations. The present study aimed to examine possible differences in gamma-aminobutyric acid (GABA) levels and synapse counts in the substantia nigra pars reticulata anterior (SNRa) and posterior (SNRp) regions between GAERS and Wistar rats receiving kindling stimulations. Animals in the kindling group either received six stimulations in the amygdala and had grade 2 seizures or they were kindled, having grade five seizures. Rats were decapitated one hour after the last stimulation. SNR regions were obtained after vibratome sectioning of the brain tissue. GABA immunoreactivity was detected by immunogold method and synapses were counted. Sections were observed by transmission electron microscope and analyzed by Image J program. GABA density in the SNRa region of fully kindled GAERS and Wistar groups increased significantly compared to that of their corresponding grade 2 groups. The number of synapses increased significantly in kindled and grade 2 GAERS groups, compared to kindled and grade 2 Wistar groups, respectively, in the SNRa region. GABA density in the SNRp region of kindled GAERS group increased significantly compared to that of GAERS grade 2 group. In the SNRp region, both kindled and grade 2 GAERS groups were found to have increased number of synapses compared to that of GAERS control group. We concluded that both SNRa and SNRp regions may be important in modulating resistance of GAERS to kindling stimulations.Publication Open Access Effects of in utero exposure to valproate or levetiracetam on the seizures and newborn histopathology of genetic absence epilepsy rats(2022-04-17) ERCAN, FERİHA; KAYA, ÖZLEM TUĞÇE; ONAT, FİLİZ; Can Kantarci B., Sanli A., Gavas S., Toplu A., Nur Turgan Asik Z., Tugce Cilingir-Kaya Ö. T., Gulcebi Idrizoglu M., ERCAN F., ONAT F.© 2022Valproate (VPA) and levetiracetam (LEV), the two broad spectrum antiseizure drugs with antiabsence effects were previously tested for their antiepileptogenic effects when administered in the early postnatal period and revealed possible modification of the epileptogenic process though the effect being not persistent. The aim of this study was to investigate the effects of in utero exposure to these drugs on the absence epilepsy seizures of Genetic Absence Epilepsy Rats from Strasbourg (GAERS) rats on electroencephalogram (EEG) which are characterised by bilateral, symmetrical, and synchronized spike-and-wave discharges (SWDs). Considering LEV was proposed as a safer drug of choice in pregnancy, its effects on the newborn histopathology of GAERS was also investigated. Adult female GAERS were randomly grouped as VPA-(400 mg/kg/day), LEV- (100 mg/kg/day), and saline-treated. The drugs were injected into the animals intraperitoneally starting before pregnancy until parturition. The lungs, kidneys, and brains of the LEV-exposed newborns were evaluated histologically to be compared with unexposed naïve Wistar and GAERS newborns. Rest of the VPA-, LEV-, and saline-exposed offsprings were taken for EEG recordings on postnatal day 90. VPA or LEV did not show significant effect on mean cumulative duration and mean number of SWDs on EEG. The lungs of the LEV-exposed offsprings showed thickened alveolar epithelium in most regions, suggesting incomplete development of the alveoli. The renal examination revealed dilated Bowman\"s spaces in some renal corpuscles, which may be interpreted as a deleterious effect of LEV on the kidney. In addition, brain examination of LEV- and saline-exposed groups revealed irregularities in cortical thickness compared to Wistar control group. Lack of significant difference on SWD parameters may indicate that the mechanism responsible for the antiepileptogenic effects of VPA and LEV may not be operating in the prenatal period. The detrimental effect of LEV exposure observed in our study on the lungs and the kidneys of the newborns should be investigated by further studies with advanced molecular and biochemical techniques.