Ataç Sönmez

Erythropoietin improves long-term spatial memory deficits and brain injury following neonatal hypoxia-ischemia in rats

It is well known that neonatal hypoxic-ischemic brain injury leads to mental retardation and deficits in cognitive abilities such as learning and memory in human beings. The ameliorative effect of erythropoietin (Epo) on experimental hypoxic-ischemic brain injury in neonatal rats has been recently reported. However, the effect of Epo on cognitive abilities in the hypoxic-ischemic brain injury model is unknown. The aim of this study is to investigate the effects of Epo on learning-memory, behavior and neurodegeneration induced by hypoxia-ischemia. Seven days old Wistar Albino rat pups have been used in the study (n = 28). Experimental groups in the study were: (1) saline-treated hypoxia-ischemia group, (2) Epo-treated (i.p., 1000 U/kg) hypoxia-ischemia group, (3) sham-operated group, (4) control group. In hypoxia-ischemia groups, left common carotid artery was ligated permanently on the seventh postnatal day. Two hours after the procedure, hypoxia (92% nitrogen and 8% oxygen) was induced for 2.5 h. Epo was administered as a single dose immediately after the hypoxia period. When pups were 22 days old, learning experiments were performed using Morris water maze. On the 20th week, when brain development is accepted to be complete, learning experiments were repeated. Rats were then perfused and brains removed for macroscopic and microscopic evaluation. Epo treatment immediately after hypoxic-ischemic insult significantly improved long-term neurobehavioral achievements when tested during the subsequent phase of brain maturation and even into adulthood. Histopathological evaluation demonstrated that Epo also significantly diminished brain injury and spared hippocampal CA1 neurons. In conclusion, Epo administrated as a single dose immediately after neonatal hypoxic-ischemic insult provides benefit over a prolonged period in the still developing rat brain. Since the wide use of Epo in premature newborns, this agent may be potentially beneficial in treating asphyxial brain damage in the perinatal period.

Neuroprotective effects of resveratrol against traumatic brain injury in immature rats

Childhood trauma resulting in traumatic brain injury (TBI) due to accidents and abuse is the major cause of death and dysfunction in the young. Since there are no approved specific pharmacological agents that block the progression of the secondary injury, the current management of TBI is mainly supportive. We aimed to determine the effect of resveratrol on hippocampal damage and behavioral deficits in 7-day-old rat pups subjected to contusion injury. Resveratrol was injected intraperitoneally at the doses of 100 mg/kg of body weight immediately after induction of traumatic injury. Hippocampal damage was examined by cresyl violet staining and behavioral alterations were evaluated using open field and novel object recognition tests 2 weeks after trauma. Histopathological evaluation showed that treatment with a single dose of 100 mg/kg resveratrol (i.p.) after the trauma significantly ameliorated the trauma induced hippocampal neuron loss at ipsilateral and contralateral hippocampal brain regions of rats. Additionally, treatment with resveratrol decreased anxiety and increased cortex/hippocampus dependent memory of animals subjected to blunt head trauma. These results show that acute treatment of resveratrol has a neuroprotective role against trauma induced hippocampal neuron loss and associated cognitive impairment in rats.

Erythropoietin Increases Glutathione Peroxidase Enzyme Activity and Decreases Lipid Peroxidation Levels in Hypoxic-Ischemic Brain Injury in Neonatal Rats

Background: We have previously shown that erythropoietin (Epo) exerts neuroprotective effects in the Rice-Vannucci model of neonatal hypoxic-ischemic brain injury. However, the mechanisms of Epo protection in this model are still unclear. Objectives: In the present study, we studied the effects of systemically administered Epo on lipid peroxidation levels and antioxidant enzyme (superoxide dismutase and glutathione peroxidase) activities following hypoxic-ischemic brain injury in neonatal rats. Methods: Seven-day-old Wistar rat pups were subjected to left carotid artery occlusion followed by 2.5 h of hypoxic exposure. Brain lipid peroxidation levels and antioxidant enzyme activities were measured in the injured hemispheres 24 h after the hypoxic-ischemic insult. Results: Hypoxic-ischemic injury significantly increased the thiobarbituric acid-reactive substance levels in the injured hemispheres as compared to the control group. In addition, glutathione peroxidase activity was significantly elevated in Epo-treated animals compared to saline-treated animals and the control group. Conclusions: These results suggest that Epo exerts neuroprotective effects against hypoxic-ischemic brain injury at least partially via the modulation of antioxidant enzyme activity.

Protective effect of melatonin against head trauma-induced hippocampal damage and spatial memory deficits in immature rats

It is well known that head trauma induces the cognitive dysfunction resulted from hippocampal damage. In the present study, we aimed to demonstrate the effect of melatonin on hippocampal damage and spatial memory deficits in 7-day-old rat pups subjected to contusion injury. Melatonin was injected intraperitoneally at the doses of 5 or 20 mg/kg of body weight immediately after induction of traumatic injury. Hippocampal damage was examined by cresyl violet staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Spatial memory performance was assessed in the Morris water maze. Melatonin significantly attenuated trauma-induced neuronal death in hippocampal CA1, CA3 regions and dentate gyrus, and improved spatial memory deficits, which was equally effective at doses of 5-20 mg/kg. The present results suggest that melatonin is a highly promising agent for preventing the unfavorable outcomes of traumatic brain injury in young children.

Positive effects of deprenyl and estradiol on spatial memory and oxidant stress in aged female rat brains

Increasing age decreases spatial learning and memory. Spatial learning is coordinated with different brain regions. Since the oxidative damage may play a role in the aging process, including the associated cognitive decline, age-related impairment in spatial learning and memory may be alleviated by antioxidant treatment. The present study examined the effects of the monoamine oxidase B inhibitor L-deprenyl, alone and in combination with estradiol, on spatial memory using the Morris water maze and oxidant stress in aged female rat brains. We demonstrated that co-administration of deprenyl and estradiol caused a synergistic effect on spatial memory. However, use of either deprenyl or estradiol alone increased antioxidant enzyme activities in brain and reduced lipid peroxidation. Therefore, positive effects of deprenyl and estradiol on spatial memory may occur due not only to their antioxidant activities but also to the different actions.

Methamphetamine induces oligodendroglial cell death in vitro.

We investigated whether the psychostimulant methamphetamine (METH) has a cytotoxic effect on oligodendrocytes and which cell-death pathways are involved in the cytotoxic process. METH caused concentration- and time-dependent cytotoxicity in rat oligodendrocyte cultures. METH induced apoptotic cell death and mRNA expression of pro-apoptotic proteins (bax and DP5), but not anti-apoptotic proteins (bcl-2 and bcl-XL). These results suggest that METH induces cytotoxicity in rat oligodendrocytes via the differential regulation of the expression of genes involved in the apoptotic process.

Age-dependent effects of maternal deprivation on oxidative stress in infant rat brain

Developing brain is much more sensitive to all kind of stressors than the developed brain. Early maternal deprivation causes some behavioural and physiological effects on rats. After the birth, there is no endocrinological response to stressors between post-natal 4 and 14th days, which is called stress-hyporesponsive period (SHRP) in rats. This hypo-responsiveness is time- and stressor-specific, as some more severe stressors have been shown to induce a stress response. The present study examined the effects of maternal deprivation on oxidative stress in the hippocampus, prefrontal cortex (PFC) and striatum regions of the brain both during and after SHRP of the infant rats. The results showed that maternal deprivation in SHRP increased antioxidant enzyme activities and reduced lipid peroxidation in infant rat brain. However, by the termination of SHRP, maternal deprivation reduced enzyme activities and increased lipid peroxidation. The results indicated that infant brain might be protected in SHRP from maternal deprivation-induced oxidative stress.

Neuroprotective effects of MK-801 against traumatic brain injury in immature rats.

Traumatic brain injury (TBI) is a major health problem in pediatric ages and also has major social, economic, and emotional outcomes, with diverse sequelae in many spheres of everyday life. We aimed to investigate the effect of MK-801, a competitive NMDA receptor antagonist, on hippocampal damage and behavioral deficits on 10-day-old rat pups subjected to contusion injury. The aims of the present study were to determine: (i) the short term effects of MK-801 on hippocampal BDNF, NGF and NMDA receptor immunoreactivity and neuron density in hippocampus (ii) long term effects of MK-801 on cognitive dysfunction following TBI in the immature rats. MK-801, was injected intraperitoneally at the doses of 1mg/kg of body weight immediately after induction of traumatic injury. Hippocampal damage was examined by cresyl violet staining, BDNF, NGF and NMDAR receptor immunohistochemistry on P10 day and behavioral alterations were evaluated using elevated plus maze and novel object recognition tests two months after the trauma. Histopathological and immunohistochemical evaluations showed that treatment with a single dose of 1mg/kg MK-801 (i.p.) significantly ameliorated the trauma induced hippocampal neuron loss and decreased BDNF, NGF and NMDAR expressions in CA1, CA3 and DG hippocampal brain regions. Additionally, treatment with MK-801 ameliorated anxiety and hippocampus dependent memory of animals subjected to trauma. These results show that acute treatment of MK-801 has a neuroprotective role against trauma induced hippocampal neuron loss and associated cognitive impairment in immature rats.

Protective effect of melatonin against maternal deprivation-induced acute hippocampal damage in infant rats

It is known that maternal deprivation induces hippocampal damage in the developing brains. In the present study, we examined the effects of melatonin on maternal deprivation-induced hippocampal damage both during and after stress-hyporesponsive period (SHRP). Hippocampal damage was examined by cresyl violet staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. The results showed that a single episode of maternal deprivation for 24 h at post-SHRP induced neuronal loss in hippocampus regions of the brain in the infant rats, while it did not influence hippocampal neurons in SHRP. Melatonin prevented maternal deprivation-induced hippocampal damage in the infant rats at post-SHRP. These results suggest that melatonin is a potentially beneficial agent to improve the neurobehavioral outcomes of maternal deprivation in later developmental period.

Early protective effects of iloprost, a stable prostacyclin analog, during spinal cord ischemia in a rabbit model

Spinal cord ischemia may develop into paraplegia in some cases during operation of the thoracoabdominal aorta. This is attributable to the vulnerability of spinal motor neurons to ischemia. In this study, iloprost was used as an agent to decrease the severity of ischemia and reperfusion injury to the spinal cord motor neurons. Twenty-one rabbits were randomized into three groups of seven animals each: group A (iloprost not administered), group B (25 ng/kg per minute iloprost), and group S (sham-operated). The spinal cord ischemia model was created by a 15-min occlusion of the aorta just caudal to the renal artery with a balloon catheter. Administration of iloprost began 10 min before occlusion of the aorta, and continued thereafter for 60 min. The pre- and postocclusion arterial pressure and heart rate recordings, results of blood gas analyses, and hematocrit and glucose levels were recorded. The spinal cords were removed after 8-h monitoring of neurologic function. Viable and nonviable motor neurons in the anterior horn of the spinal cord were counted under light microscopy. Any significant alteration in hemodynamics, blood gases, and other physiologic parameters could not be detected within the groups. Iloprost had a moderately hypotensive effect. Neurologic function in terms of Johnson scoring was significantly better in the iloprost group (P < 0.05). The number of viable cells was higher, whereas the number of nonviable cells was lower in iloprost group, when compared with the control group (P < 0.05). Higher numbers of viable motor neurons were consistent with the neurological findings. As a result of this study we concluded that iloprost infused during clamping of the aorta mitigates the spinal cord injury due to ischemia and reperfusion, and has a significant protective effect.