Person: ONAT, FİLİZ
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
ONAT
First Name
FİLİZ
Name
31 results
Search Results
Now showing 1 - 10 of 31
Publication Open Access Changes in baroreflex responses of kindled rats(WILEY, 2005-03) ONAT, FİLİZ; Kaya, CA; Ozkaynakci, AE; Goren, MZ; Onat, FYPurpose: This Study was planned to investigate the baroreflex responses (BRs) in kindled rats during seizure-free period to put forward new data on cardiac autonomic changes in epilepsy. Methods: Male Wistar rats were randomized into sham-operated (SO) and kindled groups where stimulation and recording electrodes were implanted stereotaxically into the basolateral amygdala and the cortex, respectively. For kindling process, rats were stimulated twice daily at their afterdischarge threshold current and accepted as being kindled after 10 grade 5 seizures. Six to 8 weeks after the establishment of the kindled state, mean arterial pressure (MAP) and heart rate (HR) were evaluated. BR was defined as the ratio of HR response to changes in MAP induced by i.v. nitroprusside (10, 25 mu g/kg) or i.v. pherylephrine (10, 25 mu g/kg). The sympathetic or parasympathetic component of the BR was evaluated in rats pretreated with atropine or atenolol where phenylephrine or nitroprusside was administered at 25 mu g/kg. Results: Basal MAP and HR values were found to be similar in SO and kindled rats. Phenylephrine increased MAP more in the kindled group (p < 0.05), but the HR decreased similarly in both groups. Nitroprusside decreased MAP at similar rates, but the increase in HR was higher in the kindled rats (p < 0.05). BRs to phenylephrine and nitroprusside were abolished after pretreatment with atenolol and atropine, whereas pherylephrine- and nitroprusside-induced changes in MAP remained unchanged in both groups. Conclusions: These results may indicate that amygdaloid kindling affects BRs in long-term seizure-free periods.Publication Open Access The pathways connecting the hippocampal formation, the thalamic reuniens nucleus and the thalamic reticular nucleus in the rat(WILEY, 2008-03) ONAT, FİLİZ; Cavdar, Safiye; Onat, Filiz Y.; Cakmak, Yusuf Oezguer; Yananli, Hasan R.; Gulcebi, Medine; Aker, RezzanMost dorsal thalamic nuclei send axons to specific areas of the neocortex and to specific sectors of the thalamic reticular nucleus; the neocortex then sends reciprocal connections back to the same thalamic nucleus, directly as well indirectly through a relay in the thalamic reticular nucleus. This can be regarded as a 'canonical' circuit of the sensory thalamus. For the pathways that link the thalamus and the hippocampal formation, only a few comparable connections have been described. The reuniens nucleus of the thalamus sends some of its major cortical efferents to the hippocampal formation. The present study shows that cells of the hippocampal formation as well as cells in the reuniens nucleus are retrogradely labelled following injections of horseradish peroxidase or fluoro-gold into the rostral part of the thalamic reticular nucleus in the rat. Within the hippocampal formation, labelled neurons were localized in the subiculum, predominantly on the ipsilateral side, with fewer neurons labelled contralaterally. Labelled neurons were seen in the hippocampal formation and nucleus reuniens only after injections made in the rostral thalamic reticular nucleus (1.6-1.8 mm caudal to bregma). In addition, the present study confirmed the presence of afferent connections to the rostral thalamic reticular nucleus from cortical (cingulate, orbital and infralimbic, retrosplenial and frontal), midline thalamic (paraventricular, anteromedial, centromedial and mediodorsal thalamic nuclei) and brainstem structures (substantia nigra pars reticularis, ventral tegmental area, periaqueductal grey, superior vestibular and pontine reticular nuclei). These results demonstrate a potential for the thalamo-hippocampal circuitry to influence the functional roles of the thalamic reticular nucleus, and show that thalamo-hippocampal connections resemble the circuitry that links the sensory thalamus and neocortex.Publication Open Access Cerebellar connections to the rostral reticular nucleus of the thalamus in the rat(WILEY, 2002-12) ONAT, FİLİZ; Cavdar, S; Onat, FYL; Yananli, HR; Sehirli, US; Tulay, C; Saka, E; Gurdal, EWe studied the cerebellar connections to the reticular nucleus thalamus (RNT) by means of retrograde axonal transport of horseradish peroxidase (HRP) in the rat. Specific HRP pressure injections to the rostral RNT(1.6-1.8 mm caudal to bregma) resulted in retrograde labelling of neurones in the cerebellar nuclei. The rostral RNT showed specific topographical organization of its cerebellar connections. Microinjections into the rostral RNT, 1.6 mm caudal to bregma, produced numerous HRP-labelled neurones within the anterior interposed (emboliform nucleus) and scarce HRP-labelled neurones within the lateral (dentate nucleus) cerebellar nuclei, whereas injections into the rostral RNT, 1.8 mm caudal to bregma, produced numerous HRP-labelled neurones within the posterior interposed (globose nucleus) and scarce lightly HRP-labelled neurones within the lateral (dentate nucleus) cerebellar nuclei. Cerebellar connections with the rostral RNT were exclusively ipsilateral to the injection site. No HRP-labelled cells were detected in the medial (fastigial nucleus) cerebellar nucleus. The cerebellar connections reach the RNT via the superior cerebellar peduncle. By contrast, HRP injections into the anterior, posterior interposed and lateral cerebellar nuclei produced no labelled cells within the RNT. This study demonstrates the existence of direct cerebello-RNT but not RNT-cerebellar connections. The presence of the cerebello-RNT connections introduces a new route through which the cerebellum may influence RNT and thus cerebral cortical activity.Publication Open Access Animal models of absence epilepsies: What do they model and do sex and sex hormones matter?(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2014-12) ONAT, FİLİZ; van Luijtelaar, Gilles; Onat, Filiz Yilmaz; Gallagher, Martin J.While epidemiological data suggest a female prevalence in human childhood- and adolescence-onset typical absence epilepsy syndromes, the sex difference is less clear in adult-onset syndromes. In addition, although there are more females than males diagnosed with typical absence epilepsy syndromes, there is a paucity of studies on sex differences in seizure frequency and semiology in patients diagnosed with any absence epilepsy syndrome. Moreover, it is unknown if there are sex differences in the prevalence or expression of atypical absence epilepsy syndromes. Surprisingly, most studies of animal models of absence epilepsy either did not investigate sex differences, or failed to find sex-dependent effects. However, various rodent models for atypical syndromes such as the AY9944 model (prepubertal females show a higher incidence than prepubertal males), BN model (also with a higher prevalence in males) and the Gabral deletion mouse in the C57BL/6J strain offer unique possibilities for the investigation of the mechanisms involved in sex differences. Although the mechanistic bases for the sex differences in humans or these three models are not yet known, studies of the effects of sex hormones on seizures have offered some possibilities. The sex hormones progesterone, estradiol and testosterone exert diametrically opposite effects in genetic absence epilepsy and pharmacologically-evoked convulsive types of epilepsy models. In addition, acute pharmacological effects of progesterone on absence seizures during proestrus are opposite to those seen during pregnancy. 17 beta-Estradiol has anti-absence seizure effects, but it is only active in atypical absence models. It is speculated that the pro-absence action of progesterone, and perhaps also the delayed pro-absence action of testosterone, are mediated through the neurosteroid allopregnanolone and its structural and functional homolog, androstanediol. These two steroids increase extrasynaptic thalamic tonic GABAergic inhibition by selectively targeting neurosteroid-selective subunits of GABA(A) receptors (GABA(A)Rs). Neurosteroids also modulate the expression of GABA(A)R containing the gamma 2, alpha 4, and delta subunits. It is hypothesized that differences in subunit expression during pregnancy and ovarian cycle contribute to the opposite effects of progesterone in these two hormonal states. (C) 2014 Elsevier Inc All rights reserved.Publication Open Access The effects of partial bilateral lesioning of substantia nigra in a genetic absence epilepsy rat model(2002-04-01) GÜLHAN, REZZAN; ONAT, FİLİZ; GÖREN, MEHMET ZAFER; GÖREN M. Z., GÜLHAN R., ONAT F., Ergün A.Objective: \"Genetic Absence Epilepsy Rats from Strasbourg\" (GAERS), an inbred Wistar strain, serve as an experimental venue. These rats generate spontaneous spike-and-wave discharges (SWD) and have increased γ-aminobutyric acid (GABA) levels in the ventrolateral thalamus (VLT). Recently, substantia nigra pars reticulata (SNpr) was reported to act as an endogeneous inhibitory mechanism in the generation, onset and maintenance of various types of seizures. The presence of tonic control exerted by SNpr in absence seizures should also be tested in GAERS. Methods: In this current study, GABA and L-glutamic acid release in VLT of GAERS with partial bilateral electrolytic lesions of SNpr was evaluated by using microdialysis technique with fluorescent detection. Results: GABA levels in VLT were 0.12±0.04 μM and 0.24±0.08 μM in sham-lesioned and SNpr-lesioned GAERS, respectively. L-glutamic acid level was found to be 0.41 5±0.150 μM in sham-lesioned group and 0.324±0.094 μM in SNpr-lesioned GAERS. Statistical analysis revealed no significant difference between sham-lesioned and SNpr-lesioned rats. The number and the duration of SWD were also similar in two groups. Conclusion: These findings show that SNpr does not exert a tonic control in GAERS and we assume that intact SNpr acts as a site that may exert an inhibition on target structures when activated in GAERS.Publication Open Access Amygdala kindling in the WAG/Rij rat model of absence epilepsy(WILEY, 2006-01) ONAT, FİLİZ; Aker, RG; Yananli, HR; Gurbanova, AA; Ozkaynakci, AE; Ates, N; van Luijtelaar, G; Onat, FYPurpose: 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. Methods: Electrodes were stereotaxically implanted into the basolateral amygdala of rats for stimulation and recording and into the cortex for recording. After a recovery period, the animals were stimulated at their afterdischarge thresholds. EEG was recorded to analyze SWDs and afterdischarge durations. The seizure severity was evaluated by using Racine's 5-stage scale. Results: All nonepileptic control and four of seven WAG/Rij animals reached a stage 5 seizure state, whereas three animals failed to reach stage 3, 4, or 5 and stayed at stage 2 after application of 30 stimulations. Interestingly, WAG/Rij rats, resistant to kindling, demonstrated a significantly longer duration of SWDs on the first day of the experiment before kindling stimulation than did the kindled WAG/Rij animals. Additionally, the cumulative total duration and the number of SWDs after the kindling stimulation were statistically increased compared with SWDs before kindling stimulation. Conclusions: The results of our study demonstrate that the progress of amygdala kindling is changed in rats with genetic absence epilepsy, perhaps as a consequence of the hundreds of daily SWDs.Publication Open Access COLCHICINE USE DURING PREGNANCY: CASE REPORTS(BMJ PUBLISHING GROUP, 2019-06) KARAALP, ATİLA; Duman, Nesrin Caglayan; Karabacak, Murat; Oglu, Medine Gulcebi Idriz; Inanc, Nevsun; Asik, Zehra Nur Turgan; Atagunduz, Pamir; Ozkula, Songul; Gulhan, Rezzan; Goren, Zafer; Onat, Filiz; Direskeneli, Haner; Karaalp, AtilaPublication Open Access Workshop on Idiopathic Generalized Epilepsies: Bridging basic science and clinical research (October 3-6, 2007; Antalya, Turkey)(WILEY-BLACKWELL, 2008-11) ONAT, FİLİZ; Bertram, Edward H.; Onat, Filiz Yilmaz; Ozkara, Cigdem; Moshe, Solomon L.; Avanzini, GiulianoPublication Open Access Connections of the zona incerta to the reticular nucleus of the thalamus in the rat(WILEY, 2006-08) ONAT, FİLİZ; Cavdar, Safiye; Onat, Filiz; Cakmak, Yusuf Ozgur; Saka, Erdinc; Yananli, Hasan R.; Aker, RezzanThis study demonstrated that there is a pathway from the zona incerta to the thalamic reticular nucleus. Injections of horseradish peroxidase or Fluorogold were made, using stereotaxic coordinates, into the rostral, intermediate or caudal regions of the thalamic reticular nucleus of adult Sprague-Dawley rats. The results show that the different regions of the thalamic reticular nucleus have distinct patterns of connections with the sectors of the zona incerta. In terms of the relative strength of the connections, injections made into the rostral regions of the thalamic reticular nucleus showed the highest number of labelled cells within the rostral and ventral sectors of the zona incerta; injections made into the intermediate regions of the thalamic reticular nucleus showed labelled cells in the dorsal and ventral sectors; while injections to the caudal regions of the thalamic reticular nucleus showed only a few labelled cells in the caudal sector of the zona incerta. Previous studies have shown that the zona incerta projects to the higher order thalamic nuclei but not first order thalamic nuclei. The labelling observed in the present study may represent collaterals of zona incerta to higher order thalamic nuclei projections.Publication Open Access Alterations in the kinetic activity of aromatlc-L-amino acid decarboxylase and preliminary 2-DE investigation of the brains in a 6-OHDA induced Parkinson's disease rat model(2003-07-01) OGAN, AYŞE; ONAT, FİLİZ; GÜLHAN, REZZAN; Günel A., OGAN A., ONAT F., GÜLHAN R.Objective: The aim of this study was to isolate and purify the aromatic-L-amino acid decarboxylase (AADC,EC 4.1.1.28) enzyme rats from Parkinson\"s Disease (PD) induced and the healthy control group rat brains and compare the alterations in the kinetic activities of the isolated enzyme. The protein spots displaying on the 2-DE patterns of the diseased and the healthy control group crude rat brain homogenates were evaluated. Medhods: In this study, the Parkinson\"s Disease model was induced by injecting 6-hydroxydopamine into the brains of the rats. The PD model formation was successful in two rats out of three. Results: The AADC decarboxylase was isolated and partially purified by DEAE-Sephacel ion exchange chromatography from the brains of PD induced and healthy control animals to compare the kinetic activity of the enzyme. The kinetic activity of the enzyme was reduced 70% in the PD group compared to controls. In order to determine and correlate the alterations with PD, and the distribution of the proteins displayed by the crude brain homogenates of the diseased and the healthy control group both were investigated. Polyacrylamide gel electrophoresis (PAGE) of the crude brain homogenates under the native and denaturizing conditions displayed matching bands for both of the groups, while two dimensional electrophoresis (2-DE) patterns of the crude brain homogenates of the diseased and the control group displayed considerable differences. Conclusion: The results of this study confirm the power of 2-DE-PAGE technique of the proteome analysis. Currently only the proteome analysis enables the identification of disease correlated proteins.