Gonul Peker

The Effects of Melatonin on the Antioxidant Systems in Experimental Spinal Injury

Melatonin has been recently shown by various in-vivo and in-vitro studies to exert potent neutralising effects on hydroxyl radicals, stimulate glutathione peroxidase (GSH-Px) activity, and protect catalase (CAT) from the destructive activity of hydroxyl radicals in neural tissue. We aimed to investigate the possible effects of pharmacological dose of melatonin on some of the antioxidant defence systems in an in-vivo study of experimental spinal injury. Seven groups of adult male Sprague Dawley rats were used in the following scheme: Group I: Naïve (n = 6), Group II: Lesion (n = 8), Group III: Melatonin (n = 5), Group IV: Melatonin + Lesion (n = 8), Group V: Placebo + Lesion (n = 5), Group VI: Sham operation (n = 5), and Group VII: Placebo (n = 5). Experimental spinal injury was induced at level T7-T8 by 5 sec compression of the total cord with an aneurism clip on anaesthetised and laminectomized animals. The total 10mg/kg dose of melatonin (Sigma) dissolved in alcohol-water was administered i.p. four times in 2.5 mg/kg doses, at 20min pre-, at the time of and at 1h and 2h post-compression. At 24±2h post-injury, the rats were euthanized and the lesioned segments of cord were dissected and homogenised with special care taken to distribute equal amount of injured tissue in each sample for analysis of reduced glutathione (GSH), oxidised glutathione (GSSG), superoxide dismutase (SOD), and CAT activity. Compression injury decreased GSH/GSSG ratio significantly (p <. 0001). Melatonin, by itself, significantly decreased GSSG content (p <. 05) and increased CAT activity (p <. 05) in the naive rats. Melatonin treatment decreased GSSG activity, thus elevating GSH/GSSG ratio, and also increased SOD and CAT activity without reaching statistical significance in the lesioned animals. In conclusion, pharmacological dose of systemically applied melatonin seemed to support some features of the antioxidant defence systems in our hands.

Oxytocin inhibits pentylentetrazol-induced seizures in the rat.

We aimed to reveal the anti-convulsant effects of oxytocin (OT) in pentylenetetrazol (PTZ)-induced seizures in rats. Thirty rats were randomly divided into 5 equal groups. Using stereotaxy, we implanted electroencephologram (EEG) electrodes in the left nucleus of the posterior thalamus. After 2 days, the first and second groups were used as the control and PTZ (35 mg/kg) groups, respectively. We administered 40, 80 and 160 nmol/kg OT+35 mg/kg PTZ to the rats, constituting the third, fourth, and fifth groups, respectively, for 5 days. At the end of 5 days, we recorded EEGs via bipolar EEG electrodes. After 12h, all groups except the first received 70 mg/kg PTZ and we determined the dose-response ratio. Racines Convulsion Scale was used to evaluate seizures. The spike-wave complex percentage in the EEG was determined as 0% for the first group, 38.6%±7.2 for the second group, 36.4%±5.6 for the third group, 4.3%±1.8 for the fifth group and 4.1%±1.1 for the fifth group. The fourth and fifth groups had significantly decreased spike-wave complex percentages compared to the second group (p<0.0001). OT may prevent PTZ-induced epilepsy on an EEG. OT may also be considered for use in the treatment of epilepsy in the future.

Free amino acid level determinations in normal and schizophrenic brain

1. Some disturbances in brain amino acids are reported with regard to pathological changes in schizophrenia: a reduction in GABA content and a reduced activity at some glutamatergic synapses. 2. Comparison of post-mortem brain tissue from control subjects and schizophrenic patients can provide evidence for amino acid alterations in disease. 3. The present study was undertaken to measure free amino acid concentrations in 20 brain regions obtained at autopsy, from normal persons and schizophrenics. Amino acids were extracted, esterified and separated by gas chromatography. 4. The distribution and levels of amino acids in normal persons is in accordance with similar values reported in human post-mortem brain samples by other investigators. 5. The differences in amino acids found in schizophrenic brain samples support the view of disturbed neurotransmission especially with regard to GABAergic and glutamatergic systems in schizophrenia and suggest the possible involvement of other amino acids as well.

Oxytocin provides protection against diabetic polyneuropathy in rats.

Abstract Purpose: The aim of the present study is to investigate the protective effects of oxytocin (OT) on diabetic neuropathy (DNP) in rats. Materials and methods: Eighteen rats were used to induce diabetes using single dose streptozotocin (STZ, 60 mg/kg). Diabetic DNP was verified by electromyography (EMG) and motor function test on 21st day following STZ injection. Six rats served as naïve control group and received no drug (n = 6). Following EMG, diabetic rats were randomly divided into three groups and administered with either 1 ml/kg saline or 80 μg/kg OT or 160 μg/kg OT intraperitoneally for four weeks. Then, EMG, motor function test, biochemical analysis (plasma lipid peroxides and glutathione), histological, and immunohistochemical analysis of sciatic nerves (bax, caspase 3, caspase 9, and NGF) were performed. Results: Diabetic rats developed neuropathy, which was apparent from decreased compound muscle action potentials amplitudes and prolonged distal latency in saline-treated rats (p < 0.001) whereas 160 μg/kg OT significantly improved EMG findings. OT treatment significantly lessened the thickening of perineural fibrosis when compared with saline group (p < 0.001). Besides, OT significantly reduced plasma lipid peroxides (p < 0.05) and increased glutathione levels in diabetic rats (p < 0.001). The sciatic nerves of saline-treated rats showed considerable increase in bax, caspase 3 and caspase 8 expressions (p < 0.001) while OT treatment significantly suppressed these apoptosis markers. Also, OT improved NGF expression in diabetic rats compared to saline group. Conclusion: Present results demonstrate that OT appears to alleviate harmful effects of hyperglycemia on peripheral neurons by suppressing inflammation, oxidative stress and apoptotic pathways.

Neuroprotective effects of erythropoietin on Alzheimer’s dementia model in rats

BACKGROUND Although Alzheimers disease (AD) is the most common age-related neurodegenerative disease and characterized by memory impairment, only symptomatic treatments are available. OBJECTIVES Because recombinant human erythropoietin (rhEPO) has various neuroprotective effects and improves cognitive function in animal models of neurodegenerative disorders, we investigated the therapeutic effects of rhEPO in an intracerebroventricular (ICV)-streptozotocin (STZ) animal model of sporadic-AD. MATERIAL AND METHODS A total of 24 Sprague-Dawley adult rats were divided into 4 groups of naive control (n = 6), sham-operated (n = 6), ICV-STZ + saline (n = 6) and ICV-STZ + rhEPO (n = 6). Twelve rats with Alzheimers disease, induced by STZ injection (3 mg/kg) into both lateral ventricles using a stereotaxic frame (bilaterally ICV-STZ), were divided into 2 groups 5 days after the STZ injection: one treated with rhEPO 5000 (IU/kg/day, i.p.) and the other with 0.9% NaCl (1 mL/kg/day, i.p.) for 2 weeks. The sham-operated rats received bilaterally ICV-0.9% NaCl. No surgical operation or treatment was given to the naive-control animals. On day 20, a passive avoidance learning (PAL) test was used followed by sacrification and removal of the brain tissue in all animals. Brain TNF-α and ChAT levels were determined, and neurons in the hippocampal CA1 and CA3 regions were counted by Cresyl violet staining. RESULTS ICV-STZ was found to significantly shorten the latency time on the PAL, increase brain TNF-α level, and decrease brain ChAT activity and the number of neurons in the hippocampal CA1 and CA3 regions. On the other hand, rhEPO significantly attenuated all these detrimental effects induced by STZ. CONCLUSIONS RhEPO treatment significantly prevented the ICV-STZ-induced memory deficit by attenuating the hippocampal neuronal loss, neuroinflammation and cholinergic deficit in rats. This result suggests that rhEPO may be beneficial for treating AD.

Detection of Impaired Cognitive Function in Rat with Hepatosteatosis Model and Improving Effect of GLP-1 Analogs (Exenatide) on Cognitive Function in Hepatosteatosis

The aims of the study were to evaluate (1) detection of cognitive function changing in rat with hepatosteatosis model and (2) evaluate the effect of GLP-1 analog (exenatide) on cognitive function in hepatosteatosis. In the study group, 30% fructose was given in nutrition water to perform hepatosteatosis for 8 weeks to 18 male rats. Six male rats were chosen as control group and had normal nutrition. Fructose nutrition group were stratified into 3 groups. In first group (n = 6), intracerebroventricular (ICV) infusion of exenatide (n = 6) was given. ICV infusion of NaCl (n = 6) was given to second group. And also, the third group had no treatment. And also, rats were evaluated for passive avoidance learning (PAL) and liver histopathology. Mean levels of latency time were statistically significantly decreased in rats with hepatosteatosis than those of normal rats (P < 0.00001). However, mean level of latency time in rats with hepatosteatosis treated with ICV exenatide was statistically significantly increased than that of rats treated with ICV NaCl (P < 0.001). Memory performance falls off in rats with hepatosteatosis feeding on fructose (decreased latency time). However, GLP-1 ameliorates cognitive functions (increased latency time) in rats with hepatosteatosis and releated metabolic syndrome.

Manganese-enhanced MRI to evaluate neurodegenerative changes in a rat model of kainic acid-induced excitotoxicity

PURPOSE Manganese-enhanced magnetic resonance imaging (MEMRI) has been used to detect brain activity based on the ability of active neurons to take up manganese ions through calcium channels. Kainic acid (KA), an analog of excitotoxic glutamate, can elicit selective neuronal death in the brains of rodents, of which the pathological changes partially mimic neurodegeneration in the central nervous system. We used in vivo MEMRI to evaluate neurodegenerative changes in an excitotoxicity model induced by KA in rats. MATERIALS AND METHODS Adult Sprague-Dawley rats (220-250 g) were injected with either KA or saline into the right lateral ventricle. Precontrast and postcontrast MEMRI sessions were obtained. Region of interest (ROI) analyses were performed on both injected (saline and KA) and contralateral (normal) sites in the hippocampal area. All brains were evaluated histologically following MEMRI. RESULTS Analysis of percentage change in ROI intensities of T1-weighted fluid-attenuated inversion-recovery MR images in the hippocampal area revealed a significant difference between the KA-injected (ipsilateral) and contralateral sites (P = 0.008), whereas no significant difference was observed between the saline-injected and contralateral sites. Furthermore, there was a significant difference between ipsilateral sites of the saline-treated and KA-treated groups (P = 0.026). The histological results supported these findings. CONCLUSION MEMRI is a simple and useful in vivo method for detecting neurodegenerative changes due to excitotoxicity in the rat brain. The development of a manganese-based contrast agent that can be safely used in humans is warranted to investigate neurological disorders.

The Presentation of Therapeutic Effect Of Memantine in Sepsis Induced Critical Illness Polyneuropathy

BACKGROUND: The purpose of our study is to investigate the effects of the different dosage of memantine for the treatment of Critical Illness Polyneuropathy (CIP) in rats that have surgically induced sepsis, by using electromyography (EMG) signs, such as amplitude and duration of compound muscle action potentials (CMAP), distal latency, and by using levels of plasma tumor necrosis factor (TNF)-α and lipid peroxides (malondialdehyde, (MDA)). METHODS: Rats were divided into five groups and cecal ligation and puncture (CLP) procedure was performed on 24 rats. Study groups were designed as follows: Group 1: normal (control, n=6); Group 2: sham-operated (n =6); Group 3: CLP (untreated group, n = 8); Group 5: CLP and 15 mg/kg memantin (n = 8); Group 6: CLP and 30 mg/kg memantin (n = 8). EMG was performed and plasma MDA and TNF-α levels were evaluated in all groups. RESULTS: Our findings showed an increase at the plasma levels of TNF-α and MDA in cecal ligation and puncture group. Besides, we established a reduction in CMAP amplitude and prolongation of distal latency in CLP goup. Administration of 15 and 30 mg/kg Memantine significantly provided a decrease in TNF-α and MDA levels in CLP group. CMAP distal latency was reduced in all memantine-treated groups. CONCLUSION: We observed that memantine showed its antioxidant and neuroprotective effects by decreasing the plasma MDA and TNF- α levels in CIP.