| In modern life, human exposed too many external extremely low frequency electromagnetic field(ELF-EMF) environments. TV, computers and nature atmosphere are all sources of ELF-EMF. ELF-EMF may have various effects on human beings. While center neuronal system is one of the most sensitivity tissue exposed to ELF-EMF environment and its relationship with external EMF have arouse much attention for several years. Amount of researches indicated that external EMF may have implication on human neuronal diseases and emotion state. On the other hand, researchers suggested that external EMF may contribute to the therapy of some nerves system diseases. While the complex brain electric activity in center neuronal system involved in the changes of synaptic function and postsynaptic potentials as well as ion channels thus represented different integral function. Nerve membrane potential induced by the exchanged of Na+, K+ and Ca2+,which maintained the membrane polarization or hyperpolarization state. This membrane potential in form of electric pulse transmitted to each other and then formed the global electrical activity in brain including theta, beta delta and alpha oscillations. In brain, different rhythmic oscillations can reflect different behavior performance, cognition function, memory and thinking state. Some researches demonstrated that ELF-EMF exposure resulted in dizzy, poor memory and sleep disorders. However, the underlying mechanisms of how EMF stimulation modulates neural network activity and thus induce the corresponding behavior changes are still unclear. So, explaining the effect of external ELF-EMF impacted on neuron center system is one of the hot areas in neuroscientist research. On the one hand, ELF-EMF may have impact on human health condition. On the other hand, external EMF may be provided as one of the therapeutic method for neuronal diseases, such as schizophrenia, degenerative brain diseases and trauma diseases.In brain, hippocampus has it’s explicitly physiological function and is one of the important target for the study of neuronal network oscillations. In our paper, we investigated the effects of external ELF-EMF closing to EEG activity on SD rats’ spontaneous activity and motion state conducted by open field test. We future recorded the neuron activity in hippocampus CA1 region of SD rats in vivo and provide the potential mechanisms induced by ELF-EMF.Materials and Methods1. Open field test: We divided total of one hundred SD rats into five groups randomly, including four experimental groups and one control group. Each group contained twenty SD rats. We conducted the open field test to identify rat spontaneous activity, explorer movement and emotion state while rat exposed to ELF-EMF. All experimental operation was monitored by AVT Prosilica GT1290 C video camera and all video data were captured by Norpix Streampix 6.0 software at real time.2. Behavior results analysis: We used the Noldus Ethovision XT 9.0 software to analysis the behavior results. All results were synthesized including cumulative time and zoon transaction. In order to assess the significance of ELF-EMF bioeffects, a two-tailed student’s t-test for unequal variances was used with SPSS 18.0 software. For all results, significance threshold compared with sham group was placed at p<0.05.3. Neurophysiological test: A total of ten SD rats were implanted with microelectrode arrays. After three days operation, we record neuronal activity at free moving circumstance exposed to EMF. We recorded total of nine minutes and divided three minutes equally. Rat only exposed to the middle three minutes and both the previous and post three minutes have none filed expose.4. Neurophysiological results analysis: All neuron data then analyzed offline by the following commercial software. We used the offline sorter software to indentify the characteristic of spike firing. Neuro Explorer software analyzed the following parameters. The power spectral densities and spectrums of local field potentials, auto-correlation and cross-correlation of different spike firing pattern. In Matlab software, we extract four raw brain waves according to wave algorithm and event related potentials. Lastly, we preceded the overall results in Origin 7.0 software.Results1. Open field test behaviors observation: In comparison to sham group, the immobile cumulative time in 3Hz group and highly mobile cumulative time in 10 Hz group were increased significantly both in border and corner zone(p<0.05). Inactive and mobile state accumulative time in all experimental groups(3Hz、5Hz、10Hz and15Hz)are much highly compared with control group(p<0.05).2. Neuronal activity data analysis: Spectrogram analysis revealed that theta rhythm decreased sharply while exposed to frequency 3Hz, 10 Hz and field strength 600V/m EMF. While 10 Hz,600V/m EMF exposure can decrease the amplitude of θ activity. Instant frequency in spike firing indicated that spike counts decreased obviously both in 3Hz and 10 Hz 600V/m EMF(p<0.05). Though the 5Hz and 15 Hz groups can increase the spike firing, but they all have no significant difference between of each other. Lastly, we also extract the event related potentials(ERP) induced by external electromagnetic field stimulus in characteristic of amplitude at 10 u V and 300 ms duration.Conclusions1. While rat exposed to ELF-EMF environment, external EMF may have influence on the spontaneous activity represented decreased locomotion in 3Hz 600V/m and reflected rat negative emotion, such as anxiety. While 10 Hz 600V/m can improve the locomotion suggesting the relax state. All EMF exposure can inhabit rat spontaneous exploration activity.2. Electromagnetic field closing to instinct brain activity could modulate the spectrogram of theta rhythm oscillation and induce the decrease of spike firing in hippocampus CA1 region when rat exposed both in frequency 3Hz,10 Hz and field strength 600V/m. Moreover, ELF-EMF could induce the possible change of hippocampus CA1 potentials.3. External EL-EMF may affect the spontaneous locomotion and movement of rat, the underlying mechanism is the modulation of neuronal activity. |
PDF Full Text Request