Forough Ebrahim Tabar

Bio: Forough Ebrahim Tabar is an academic researcher from Babol University of Medical Sciences. The author has contributed to research in topics: Hippocampal formation & Synaptosome. The author has an hindex of 2, co-authored 2 publications receiving 16 citations.

High and low temperatures affect rat hippocampal synaptosome’s viability and functions

Abstract: Introduction: Synaptosomes are sealed particles that contain mitochondria, cytoskeleton and vesicles which are necessary to synaptic events like neurotransmitter release and uptake in the nervous system. However, the effect of high and low temperatures on synaptosome membrane integrity and function during a time course after its extraction is less known. The purpose of this study was to assess synaptosome viability and function at 37, 4°C and room temperature (RT) during 6 hours after its extraction. Methods: Hippocampi of 40 male Wistar rats were used for synaptosome preparation. To ensure synaptosome membrane integrity and function, lactate dehydrogenase activity (LDH) and GABA uptake were assessed during 6 successive hours after their extraction at 37, 4°C and RT. Results: Our results showed that at 37°C, synaptosome membrane integrity was reduced 3 hours but at 4°C and RT, it occurred 5 hours following their extraction. The results of synaptosome function analysis coincide with LDH enzyme assay data, meaning that GABA uptake faced a 50% reduction from the initial value at 37°C after 3 hours and at RT after 5 hours. We also found that GABA uptake was reduced at 4°C in the first hour after extraction because the low temperature inhibits GABA transporters. Conclusion: Synaptosomes preserved their viability and function at RT, 37 and 4°C at least for 3 hours after extraction and reduced over time. For long term application of synaptosomes, it is better to keep them at 4°C. iD Physiol Pharmacol 22 (2018) 73-81 D ow nl oa de d fr om p pj .p hy ph a. ir at 1 0: 19 + 03 30 o n M on da y N ov em be r 4t h 20 19 Synaptosome viability and function Physiol Pharmacol 22 (2018) 73-81 | 74 by Whittaker in the late 1950s and detected as detached synapses by electron microscopy (Whittaker, 1993; Whittaker and Gray, 1962). Synaptosomes are acquired by homogenization of fresh brain tissue in an appropriate isotonic solution which causes the nerve terminals to be separated from their axon stalks. Then, the membrane of presynaptic terminals is resealed, which contains cytoplasm, cytoskeleton, mitochondria and synaptic vesicles with the presynaptic and occasionally postsynaptic membranes (Dunkley et al., 2008; Whittaker et al., 1964). Synaptosomes have widely been applied as an in vitro model to investigate the molecular mechanisms of brain synapses specially storage, release, and uptake of neurotransmitters. As a result, our knowledge about the function of synapse ending at a physiological, cellular and molecular level was enhanced (Breukel et al., 1997; Dunkley et al., 1988; Dunkley et al., 2008; Whittaker, 1993). Different procedures have been developed to isolate synaptosomes including ultrafiltration, electrophoresis, sucrose and percoll gradients; however, a median-speed centrifuge technique seems to be more appropriate (Dunkley et al., 1988; Dunkley et al., 2008; Enriquez et al.,1990; Kamat et al., 2014; Stadler and Tashiro, 1979). Synaptosomes can be obtained from any part of the brain tissues. In addition, the nerves of the non-neurological tissue are also involved in the synaptosomes preparation (Jonakait et al.,1979). If a chemical active ingredient is found abundantly in synaptosomes, it can be assumed as a neurotransmitter or coneurotransmitter. Moreover, mixed fraction synaptosomes can be applied to assess the mechanisms of neurotransmitters release (Breukel et al., 1997). Exposure of adult albino rats to the high ambient temperature at 35 °C for 2-12 hours or at 45 °C for 12 hours increased the acetylcholinesterase activity of their brain synaptosomes (Mukhopadhyay and Poddar, 1990). Several studies have investigated the effects of organophosphate compound on the GABA uptake of synaptosomes in cerebral cortex, cerebellum and hippocampus, suggesting that the GABA uptake was optimal one hour after synaptosome extraction (Ghasemi et al., 2007; Pourabdolhossein et al., 2009; Shahroukhi, et al., 2007). Furthermore, Hosseini et al. reported 35 minute is the optimal time for GABA release by rat cerebral synaptosomes (Hosseini et al., 2004). Incubation of synaptosomes at room temperature (22-25 °C) gradually increases the percentage of microtubule containing synaptosomes (41-47%) while its stabilization at low temperature leads to a significant reduction in the number of synaptosomes (Hajos et al., 1979). Despite the significance of synaptosomes in pharmaceutical, structural and functional studies, there is no empirical data on synaptosomes viability and function at different temperatures and time points after their extraction. Thus, the main ambition behind this study was to examine the synaptosomes survival and function at different temperatures and time points by measuring lactate dehydrogenase enzyme (LDH) and GABA uptake. We used hippocampal synaptosome due to its high synaptic contacts ratio compared to the other brain regions (Cragg, 1975). Materials and methods

Schema-like learning and memory consolidation acting through myelination.

Abstract: Memory is a dynamic brain function that is continually processed after encoding. Although psychologic concepts of mental schema are now well established, they have rarely been considered in animal ...

Arbutin Improves Functional Recovery and Attenuates Glial Activation in Lysolecethin-Induced Demyelination Model in Rat Optic Chiasm

Abstract: Neuroinflammation, glial activation, and oxidative injury are the main pathological mechanisms of demyelination in multiple sclerosis (MS). Arbutin, a natural polyphenol compound, possesses antioxidant, anti-inflammatory, and neuroprotective properties whose therapeutic potential has not been studied in the experimental animal models of MS. In the present study, the efficiency of arbutin on lysolecthin (LPC)-induced local demyelination model was investigated. Demyelination was induced by micro-injection of 2 μl LPC (1%) into the rat optic chiasm and the treated group received daily injection of arbutin (50 mg/kg, i.p) during 2 weeks. Visual-evoked potential (VEP) recordings were used to functionally assess the visual pathway. Gene expression analysis was done to evaluate the arbutin effect on the inflammatory, stress oxidative-related mediators, and myelin markers. The myelin-specific staining was performed to assess demyelination and GFAP staining as an astrocyte marker. We found that arbutin significantly reduced P1-latency of VEPs waves and demyelination at 7 and 14 days post-demyelination. Arbutin decreased inflammatory cytokines (IL-1B, IL-17, TNF-α) and iNOS mRNA expression level. In addition, the expression level of anti-inflammatory cytokine (IL-10) and antioxidant mediators (Nrf-2 and HO-1) was enhanced by arbutin treatment. Arbutin increased MBP and Olig2 expression levels in demyelination context. Finally, arbutin attenuated GFAP as an astrocyte marker. Finally, this study demonstrates that arbutin improves functional recovery and myelin repair in the demyelinated optic chiasm through attenuation of inflammation, astrocyte activation, and oxidative stress. These findings might open new promising avenues for treating demyelinating disorders such as multiple sclerosis.

Protective Effects of Hyperbaric Oxygen Therapy on Brain Injury by Regulating the Phosphorylation of Drp1 Through ROS/PKC Pathway in Heatstroke Rats

Abstract: This study aimed to elucidate the neurotherapeutic effect of hyperbaric oxygen (HBO) on brain injury and the potential role of dynamin-related protein 1 (Drp1) and its regulatory pathway in heatstroke (HS) rats. In in vivo experiments, rats were exposed to HBO after the onset of HS, or the same pressure but normal air as a control. The results indicated that HBO decreased the mortality and thermoregulatory dysfunction and prolonged the survival time of HS rats. Neurological dysfunction induced by HS was attenuated by HBO through assessment of modified neurological severity score and Morris water maze. HBO also alleviated histopathologic changes and oxidative injury (malondialdehyde and 8-hydroxyguanine), increased activities of superoxide dismutase (SOD) and glutathione/oxidized glutathione and ameliorated apoptotic parameters (caspase-3/6 activities and the number of apoptotic cells) of the hippocampus, hypothalamus and brain stem in rats compared to the HS group. Phosphorylation of DrpSer616 was increased by HS but decreased by HBO in the brains of rats determined by Western blot and immunohistochemical staining. In experiments in vitro, rat hippocampal neurons were used as a heat stress (HS) cellular model to examine the effects of HBO. As the results, HBO attenuated HS-induced cytotoxicity, oxidative injury (malondialdehyde), reactive oxygen species (ROS) generation, decreasing SOD activity and apoptosis. Drp1 inhibitor (Mdivi-1) treatment produced the same effects and had a trend to decrease oxidative injury. But the difference is not statistically significant. HBO and Mdivi-1decreased the phosphorylation of DrpSer616 induced by HS and HBO decreased the phosphorylation of protein kinase C (PKC) induced by HS. Moreover, both PKC inhibitor and ROS scavenger inhibited HS-induced p-DrpSer616. In conclusion, HBO may alleviate the brain injury caused by HS by decreasing ROS/PKC-regulated p-DrpSer616.