Study On Effect And Molecular Mechanism Of Electromegnetic Radiation To The Synaptic Plasticity In Rats

Frequency and intensity determin the effect of electromagnetic radiation to health. Health effects of electromagnetic wave sources of different frequency are different. Microwaves are classified as non-ionizing electroagnetic radiation(EMR),900MHz is internationally used as the telecom frequency of mobile or cellular phones. Adverse health effects of microwave exposure by thermalizing have been generally accepted, while health effects of long term low intensity exposure remain controversial, esp. for900MHz GSM microwaves. Much research has focused on the effects on CNS tumor and the effects on neurobehavior. It is generally accepted that further researches need to be employed to esplore whether there are relations between900MHz microwave and brain tumor. A compelling evidences have been shown that900MHz microwave have effects on neurobehavior. Epidemiological survey indicates that the electromagnetic radiation can cause the excessive contact of the central nervous system and plant nerve dysfunction. Animal experiments show that the electromagnetic radiation can cause learning and memory and cognitive disabilities.To explore the possible effects and its mechanism of900MHz on the functions of CNS, we choose2000μW/cm2radiation intensity and adopt animal experiment and primary cultured neurons.arounding the changes of synaptic plasticity and the changes of protein in hippocampus to carry out the following studies:PART I Effects of EMR on learning and memory behaviour and observation of histopathology of hippocampus in ratsObjective:To evaluate the effects of2000μW/cm2electromagnetic radiation on learning and memory abilities of rats.Methods:Rats were randomly divided into normal control group, sham-radiated group, and lh/d,2h/d, and3h/d radiation groups. The rats in the radiation groups were fixed after microwave exposure of2000μW/cm2, then their learning and memory abilities were tested by Morris water maze experiment and the morphological changes in the hippocampal neurons were detected by thionin staining.Results:1Compared with the normal control group, the sham-radiated group has no significant change (P>0.05), while the platform-finding time in Morris water maze test was significantly longer (P<0.05), and the average number of exploration was significantly reduced in radiation group.2In the Nissl staining experiment, the morphology and quantity of the hippocampal neurons have no significant change. In the radiation group, the hippocampal CA1region visualized obvious pathological changes in the neurons, showing evident reduction in the number (P<0.05), irregular, and arrayed in disorder. Moreover, a larger numer of Cytoplasmic Nissl were lost.Conclusion:900MHz electromagnetic radiation can weaken the learning and memory abilities of rats possibly through a mechanism in relation to neuronal injury in the hippocampus CA1region.PART II The ultrastructural change and the expression of apoptosis related gene in hippocampus after EMRObjective:To evaluate the effects of2000μW/cm2electromagnetic radiation on hippocampus ultrastructural changes and apoptosis-related genes.Methods:Rats were randomly divided into normal control group, sham-radiated group, and lh/d,2h/d and3h/d radiation groups. The rats in the radiation groups were fixed after microwave exposure of2000μW/cm2, then the morphological changes in the hippocampal neurons were detected by transmission electron microscopy and the expression of Bcl-2and Bax protein was detected by immnunohistochemistry and the expression of Caspase-3was detected by Western blotting.Results:Microscopic observation revealed that the chromatin coacervation and chromatin of hippocampal neurons gathered along the inside of the nuclear membrane in radiation group. Compared with the normal control group, the expression of Bax and Caspase-3protein rised and Bcl-2protein decreased in radiation group. The ratio of Bax/Bcl-2was obviously higher in radiation group than in normal control rats.Conclusion:2000μW/cm2electromagnetic radiation exposure can induce the abnormality of neuronal apoptosis in rat hippocampus. As a regulating gene of Bcl-2、Bax、and Caspase-3may participate in hippocampus neuron apoptosis induced by electromagnetic radiation.PART Ⅲ Effects of EMR on expression of immunoreactive protein and mRNA of NMD A receptor in rats hippocampusObjective:To evaluate the effects of electromagnetic radiation of2000μW/cm2exposure on mRNA and protein expression levels of immunoreactive protein and mRNA of NMDA receptor in rats hippocampal, and to explore the mechanism of electromagnetic radiation induced learning and memory impairment.Methods:Rats were randomly divided into normal control group, sham-radiated group, and1h/d,2h/d, and3h/d radiation groups. The rats in the radiation groups were fixed after microwave exposure of2000μW/cm2, then the change of NMDA (NR1、NR2A and NR2B) protein in hippocampal neurons of each group of rats were measured with immunohistochmistry and Western blotting techniques, and the expression of NMDA (NR1、NR2A and NR2B) mRNA in hippocampus were determined by RT-PCR.Results:Compared with the normal control group, each index of the sham-radiated group has no significant change (P>0.05). In the radiation group, the hippocampal neurons of rats showing evident reduction in the ratio of NMDA (NR1-, NR2A and NR2B) positive cells, irregular, and arrayed in disorder. Moreover, the expession of NMDA (NR1、NR2A and NR2B) protein and its mRNA in hippocampal neurons were significant decreased (P<0.05).Conclusion:Electromagnetic radiation of2000μW/cm2exposure can impair the learning and memory abilities of rats possibly through a mechanism correlated with the lower expression of NMDA (NR1、NR2A and NR2B) protein and its mRNA in hippocampus.PART IV Effects of EMR on expression of CREB and CaMKII in hippocampal neuronsObjective:To evaluate the effects of electromagnetic radiation of2000μW/cm2exposure on mRNA and protein expression levels of CREB and CaMKII in hippocampal neurons of rats, and to explore the mechanism of electromagnetic radiation induced abnormality of neuronal damage.Methods:Divided the hippocampal neurons cultured for seven days into five groups:normal control group, sham-radiated group, and1h/d,2h/d, and3h/d radiation groups. The hippocampal neurons in the radiation groups were fixed after microwave exposure of2000μW/cm2, then morphological changes were detected by inverted microscope, we use MTT to detect the survial ratio of the hippocampal neurons, the change of CREB and CaMKII protein in hippocampal neurons of each group of rats were measured with Western blotting techniques, and the expression of CREB and CaMKII mRNA in hippocampus neurons were determined by RT-PCR.Results:It can be observed in normal control group that hippocampal neuronal nucleolus was integrated, in radiated group that hippocampal neuronal nucleolus was crimple, cellular tuber was shrinked. Compared with the normal control group, each index of the sham-radiated group has no significant change (P>0.05), while the cell vitality of radiated group in MTT test were significantly decreased (P<0.05). In the radiation group, the expession of CREB and CaMKII protein and its mRNA in hippocampal neurons were significant decreased (P〈0.05).Conclusion:2000μW/cm2electromagnetic radiation exposure can induce the abnormality of neuronal damage in cells. The machanism of hippocampus neuron injury is involved in the expression of CREB and CaMKII...