Uticaj elektromagnetnog polja (0,5 mT, 50 Hz) na motorno ponašanje, parametre oksidativnog stresa i morfološke karakteristike mozga nakon eksperimentalno izazvane moždane ishemije na modelu pustinjskog miša
Influence of electromagnetic field (0,5mT, 50 Hz) on motor behaviour, oxidative stress parameters and morphological characteristicsof brain after global cerebral ischemia in mongolian gerbils
Doctoral thesis (Published version)
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Nowadays, one of the most common diseases, which affect the whole society, is brain stroke, which can be caused by cerebral ischemia. Beside high mortality rate, consequences of brain stroke are often permanent without appropriate treatment. Another hallmark of modern society is development of electronic industry and usage of diverse electron devices, therefore increasing degree of pollution with “electromagnetic smog”. The increased presence of extremely low frequency magnetic fields (ELF-MF) has attracted the interest of many scientists to explore its effects, among others, on functional properties of central nervous system. Based on the known facts of its action, we can propose that this field affects development of pathophysiological events and recovery in conditions like cerebral ischemia. The purpose of this study was to determine whether ELF-MF (0.5 mT, 50 Hz, continuous exposue during 7 days) affects hypermotor activity of gerbils, induced by 10-min global cerebral ischemia on the 1st, 2nd, 4th and 7th day (immediate effect) as well as on the 14th day after reperfusion (delayed effect). Also, on this model we examined whether applied ELF-MF affect oxidative stress parameters, otherwise increased after cerebral ischemia, in some brain regions on the 7th and 14th reperfusion day. Also, we examined effect of ELF-MF on morphological changes in the most vulnerable structures of brain (hippocampus, striatum and forebrain cortex) induced by ischemia on the 7th and 14th reperfusion day, as well as performed quantification of this changes in neurons and glial cells. Animal behaviour was monitored for 60 min in the open field. It was shown that the 10-min global cerebral ischemia per se induced a significant motor activity increase (locomotion, stereotypy and rotations), and consequently immobility decrease until day 4 after reperfusion, compared to control gerbils. Exposure to ELF-MF inhibited development of ischemiainduced motor hyperactivity during the whole period of registration, but significantly in the first 2 days after reperfusion, when the postischemic hyperactivity was most evident. Motor activity of these gerbils was still significantly increased compared to control ones, but only on the 1st day after reperfusion. Parameters of oxidative stress (NO, O2-, SOD, ILP) were determined in hippocampus, striatum and forebrain cortex applying biochemical assays. Ischemia per se caused increasing of oxidative stress in all examined structures on the 7th and also 14th reperfusion day with SOD values on the control level. ELF-MF also increased production of free radical species on the 7th day (immediate effect of ELF-MF) but in higher degree then ischemia, as well as, activity of SOD. 7 days after cessation of exposure (delayed effect of ELF-MF) measured values for all parameters were at the control levels. Ischemic gerbils exposed to ELF-MF had increased values of parameters of oxidative stress on the 7th reperfusion day (immediate effect of ELF-MF) but to a lesser extent than ischemic animals or animals exposed to ELF-MF. On the 14th reperfusion day, parameters of oxidative stress in the brain of ischemic gerbils exposed to ELFMF were at the control levels. Applying stereological methods, histological evaluation of changes in the hippocampus was done determining its volume, volume density of degenerating neurons and astrocytes, as well as the number of microglial cells per unit area. ELF-MF per se did not induce any morphological changes in the examined brain structures, while 10-min global cerebral ischemia led to neuronal death, especially in CA1 region of the hippocampus, as expected. Ischemic gerbils exposed to ELF-MF had significantly lower degree of cell loss in the examined structure and greater response of astrocytes and microglial cells than postischemic gerbils without exposure on the 7th day after reperfusion (immediate effect of ELF-MF). Similar response was observed on the 14th day after reperfusion (delayed effect of ELF-MF), however differences in measured parameters were not significant. Results of this study revealed that the applied ELF-MF (0.5 mT, 50 Hz) decreased motor hyperactivity induced by the 10-min global cerebral ischemia, via modulation of the processes that underlie this behavioural response. Also, ELF-MF decreased oxidative stress induced by global cerebral ischemia thus decreasing possible negative consequences which free radical species have in the brain. Applied ELF-MF has possible neuroprotective function in the hippocampus, the most sensitive brain structure in the model of global cerebral ischemia, through reduction of neuronal death and activation of astrocytes and microglial cells.
Keywords:Cerebral ischemia; Electromagnetic field; Motor behaviour; Oxidative stress; Morphology
Source:University of Belgrade, Faculty of Biology, 2012, 1-127