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KOYUNCUOĞLU, TÜRKAN

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2017 - 201922020 - 20211
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Author: YEGEN, BERRAK × Subject: RECEPTOR ×

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    PublicationOpen Access
    High-fat Diet Enhances Gastric Contractility, but Abolishes Nesfatin-1-induced Inhibition of Gastric Emptying
    (KOREAN SOC NEUROGASTROENTEROLOGY & MOTILITY, 2021-04-30) YEGEN, BERRAK; Ozdemir-Kumral, Zarife N.; Koyuncuoglu, Turkan; Arabaci-Tamer, Sevil; Cilingir-Kaya, Ozlem T.; Koroglu, Ayca K.; Yuksel, Meral; Yegen, Berrak C.
    Neither HFD nor NES-1 changed methylcellulose emptying, but NES-1 delayed saline emptying in cannulated ND-rats. Inhibitory effect of NES-1 on gastric emptying in ND-rats was reversed by all antagonists, and abolished in HFD-rats. In HFD-rats, carbachol-induced contractility was enhanced in gastric, but inhibited in ileal strips. HFD increased body weight, while serum triglycerides, alanine transaminase, aspartate aminotransferase, glucose, and levels of malondialdehyde, glutathione, myeloperoxidase activity, and luminolchemiluminescence in hepatic, ileal, and adipose tissues were similar in ND- and HFD-rats, but only lucigenin-chemiluminescence was Background/Aims Gastrointestinal motility changes contribute to development and maintenance of obesity. Nesfatin-1 (NES-1) is involved in central appetite control. The aim is to elucidate effects of NES-1 and high-fat diet (HFD) on gastrointestinal motility and to explore myenteric neuron expressions of tyrosine hydroxylase (TH), vasoactive intestinal peptide (VIP), and neuronal nitric oxide synthase (nNOS) in HFDinduced oxidative injury. Methods Sprague-Dawley rats were fed with normal diet (ND) or HFD. Gastric emptying rate was measured following NES-1 (5 pmol/rat, intracerebroventricular) preceded by subcutaneous injections of glucagon-like peptide 1 (GLP-1), cholecystokinin 1 (CCK-1), and gastrin/CCK-2 receptor antagonists. In carbachol-contracted gastric and ileal strips, contractile changes were recorded by adding NES1 (0.3 nmol/L), GLP-1, CCK-1, and gastrin/CCK-2 antagonists. Results Neither HFD nor NES-1 changed methylcellulose emptying, but NES-1 delayed saline emptying in cannulated ND-rats. Inhibitory effect of NES-1 on gastric emptying in ND-rats was reversed by all antagonists, and abolished in HFD-rats. In HFD-rats, carbachol-induced contractility was enhanced in gastric, but inhibited in ileal strips. HFD increased body weight, while serum triglycerides, alanine transaminase, aspartate aminotransferase, glucose, and levels of malondialdehyde, glutathione, myeloperoxidase activity, and luminolchemiluminescence in hepatic, ileal, and adipose tissues were similar in ND-and HFD-rats, but only lucigenin-chemiluminescence was increased in HFD-rats. Vasoactive intestinal peptide (VIP) and TH immunoreactivities were depressed and nNOS immunoreactivity was increased in gastric tissues of HFD-rats, while VIP and TH were enhanced, but nNOS was reduced in their intestines. Conclusions HFD caused mild systemic inflammation, disrupted enteric innervation, enhanced gastric contractility, inhibited ileal contractility, and eliminated inhibitory effect of NES-1 on gastric motility. (J Neurogastroenterol Motil 2021;27:265-278)
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    Obestatin improves oxidative brain damage and memory dysfunction in rats induced with an epileptic seizure
    (ELSEVIER SCIENCE INC, 2017) YEGEN, BERRAK; Koyuncuoglu, Turkan; Vizdiklar, Caner; Uren, Dogan; Yilmaz, Hakan; Yildirim, Cagan; Atal, Sefa Semih; Akakin, Dilek; Demirci, Elif Kervancioglu; Yuksel, Meral; Yegen, Berrak C.
    Obestatin was shown to alleviate renal, gastrointestinal and haemorrhage-induced brain injury in rats. In order to investigate the neuroprotective effects of obestatin on seizure-induced oxidative brain injury, an epileptic seizure was induced with a single intraperitoneal (i.p.) close of pentylenetetrazole (PTZ, 45 mg/kg) in male Wistar rats. Thirty minutes before the PTZ injection, rats were treated with either saline or obestatin (1 mu g/kg, i.p.). Seizure was video-taped and then evaluated by using Racine's scoring (0-5). For the assessment of memory function, passive-avoidance test was performed before seizure induction, which was repeated on the 3rd day of seizure. The rats were decapitated at the 24th or 72nd hour of seizures and brain tissues were obtained for histopathological examination and for measuring levels of malondialdehyde (MDA), glutathione (GSH), reactive oxygen radicals and myeloperoxidase (MPO) activity. Obestatin treatment reduced the average seizure score, decreased the occurrence and duration of generalized tonic-clonic seizures, presenting with a shorter latency to their onset. Increased lipid peroxidation and enhanced generation of oxygen-derived radicals detected at the post-seizure 72nd h were suppressed by the consecutive treatments of obestatin, but no changes were observed by the single obestatin treatment in the 24-h seizure group. Neuronal damage and increased GFAP immunoreactivity, observed in the hippocampal areas and cortex of PTZ-induced rats were alleviated in 3-day obestatin-treated PTZ group. PTZ-induced memory dysfunction was significantly improved in obestatin-treated PTZ group as compared to saline-treated rats. The present data indicate that obestatin ameliorated the severity of PTZ-induced seizures, improved memory dysfunction and reduced neuronal damage by limiting oxidative damage. (C) 2017 Elsevier Inc. All rights reserved.
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    PublicationOpen Access
    Nicorandil preserves blood-brain barrier and improves memory impairment in hypertensive rats
    (MARMARA UNIV, 2019-11-15) YEGEN, BERRAK; Cevikelli Yakut, Zatiye Ayca; Ertas, Busra; Koyuncuoglu, Turkan; Yegen, Berrak C.; Sener, Goksel
    In renovascular hypertension (RVH), oxidative stress and inflammation due to high blood pressure and elevated levels of angiotensin 2 are mainly responsible of cerebrovascular complications and impaired cognitive functions. Since the nicorandil has been shown to exert neuroprotective, anti-inflammatory and antioxidant effects, we investigated the effect of nicorandil against vascular dementia and blood brain barrier damage in a rat model of angiotensin-dependent hypertension. Wistar albino rats, were divided as sham-operated control, renovascular hypertension (RVH) and Nicorandil-treated RVH groups. Silver clip was implanted onto the left renal artery. Using the tail-cuff method, blood pressure of rats was measured before the surgery and at the end of the post-surgical 3rd and 12th weeks. Nicorandil (4mg/kg, orally) or vehicle was administered for 9 weeks. Twelve weeks after RVH surgery, a new object recognition test was performed. Following the determination of blood brain barrier integrity, serum samples were taken for the evaluation of proinflammatory cytokines tumor necrosis alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta). Levels of sodium-potassium adenosine triphosphatase (Na+/K+-ATPase), as a marker of endothelial damage, were evaluated in the hippocampal tissues. RVH resulted in significant increases in TNF-alpha and IL-1 beta levels and decreases in Na+/K+-ATPase levels, along with impairment in blood brain barrier integrity and memory performance. In the nicorandil treatment group, these indices were reversed back to control levels. The present data demonstrated that nicorandil attenuates RVH-induced memory impairment and blood brain barrier damage in rats with RVH.