| Background and Objective:Olfactory is an important and basic sensory system in mammalians. In anatomy, Olfactory neurons project axons to olfactory relevant brain regions, as well as to amygdala and hippocampus, both of them are essential for the learning and memory. Therefore, besides maintaining normal olfactory function, olfactory system play an important role in learning and memory function. With the rapid development of science and technology, a variety of household appliances and communication equipment have become increasingly popular in people’s life. Nowadays, the extremely low frequency magnetic field (ELF-MF) has become a new kind of environmental pollution, which is paid more and more attention, especially relationship between exposure to ELF-MF and central nervous system diseases. Recent studies have shown that the ELF-MF may have potential danger to human body, such as the body’s circulatory system, the immune reproductive, the metabolic function and the central nervous system, and the ability of learning and memory. What is more, the ELF-MF can cause cancer and accelerate cancer cells proliferation. As a kind of objective existence of external factors, the magnetic field effect on learning and memory is relatively complex. A lot of research work has been done, but because of Methods and conditions differences, it is far to draw an acceptable conclusion. In daily life, people can avoid the high frequency electromagnetic radiation damage, but cannot avoid low frequency electromagnetic radiation that is produced by these home appliance just like mobile phone and computer.Olfactory system provide the brain and external environment of the direct connection, and many of the brain in charge of learning and memory in brain areas are closely related.Does low-frequency electromagnetic radiation harm the olfactory discrimination and memory of human body? The relevant reports have not been studied.This experiment aims to investigate the influence of long-term ELF-MF exposure of adult mouse olfactory discrimination and memory function.Besides,our study also provides valuable biology and medicine information to esatblish health standards and protection principle to ELF-MF fields.What the molecular biology of these effects and other substances active ingredients and electrophysiological activity change also requires us to further research and discussion.Methods:1. Mice were randomly divided into magnetic field exposure group and sham exposure group. Exposure group were exposed to 50hz magnetic field of 1 Mt (1 hour/day) at 9 o’clock in the morning every day for 20 days. Except shutting off power of equipment that produced magnetic field, false exposure group were treated with the same experiment procedure.2. According to the properties of the rodents with natural explorative ability, a habituation-dishabituation pattern was used to study exposure group and false exposure group’s olfactory discrimination and field behavior to Familiar smell and extraneous smell. The 21st day, the open field experiment was conducted. Mice were put in behavior box toware the same direction, and the number of the grids that mouse crawled and the number of the mouse standing(hind feet stand).3. Olfactory discrimination test:With two identical wooden box, each box placed within two interval of 10 cm porcelain dish. Each mouse has six missions, lemon flavor or distilled water were droped into porcelain dishs of wooden box in the first five missions. make the mouse have habituation on a certain smell.In the sixth mission, novel odors (mint flavor) or distilled water were droped into two porcelain dish.Mice stayed inside wooden box for 5 min of each mission, the two missions have 15 min interval.Then the time of explore smell were to compareed.4.Olfactory memory test:Two porcelain dishs were put in the wooden box, and the one was the lemon or mint smell, another drip into the distilled water.Mouse was put in the box in the experiment period twice, and stayed in 5 min. The sorroundings and smell was the all same. But interval between two experiment was different,and five intervals(20min,40min,60min,80min,100min) was set in the experiment. The time that the mouse two smelling times in an experimental cycle were analyzed.Results:1. In the open field experiment, There was unsignificant differences between exposure group and sham exposure group in the number of the grid that mouse crawled and the number of the mouse standing (P>0.05).2. Olfaction discrimination test:compared with distilled water side, magnetic field exposure group and sham exposure group explore lemon or mint smell for a long time in mice, and the difference was statistically significant (P< 0.01);In 1～5 times of odor discrimination task in mice stay time in odour side gradually reduced, and the difference was statistically significant (P< 0.01);the results of explore time show that the 6th mission on extraneous smells compared with the fifth mission on familiar smell the expression significan extend, found that two groups were able to identify two different smells:the lemon and mint, and the difference was statistically significant (P< 0.01).3. Olfactory memory capacity:In olfactory memory tasks, in different time intervals, the mice are placed twice in wooden box that has the same smell. The time of the second explore of Sham exposure group of mice was significantly less than the first in 20 min (p< 0.01),40 min (p< 0.01),60 min (p< 0.01), while was no significant in 80 min and in 100 min. the magnetic field exposure group had similar result. The experimental results show that continuous 20d magnetic field exposure(lh daily,50 Hz) has no olfactory memory function in mice have a significant impact.Conclusion:1.Exposure to chronic ELF-MF has no effect on behavior (locomotion)and exploring behavior.2.Exposure to chronic ELF-MF has no effect on olfactory discrimination and memory m mice. |
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