Effects of extremely low frequency electromagnetic fields (100μT) on behaviors in rats

Abstract

Recently, extremely low frequency electromagnetic fields (ELF-EMF) have received considerable attentions for their potential pathogenicity. In the present study, we explored the effects of ELF-EMF on behaviors of adult male rats. Sixty adult male rats were randomly divided into two groups, the sham exposure group and the 50Hz/100μT ELF-EMF exposure group. During the 24 weeks exposure, body weight, as well as food and water intake were recorded. Results showed that food and water intake and the body weight of the rats were not affected by the exposure. After 24 weeks exposure, open field test and elevated plus maze were conducted to evaluate the anxiety-like behavior, the tail suspension test and forced swim test were conducted to evaluate depression-like behavior and Morris water maze and fear conditioning tests were used to evaluate the cognitive and memory ability. Exposure to ELF-EMF did not induce any anxiety-like or depression-like behaviors compared with the sham exposure. Moreover, the cognitive and memory ability was not impaired by the ELF-EMF exposure. Furthermore, ELF-EMF exposure did not affect the morphology and histology of the brain. In conclusion, 24 weeks exposure to 50Hz/100μT ELF-EMF had no effect on the behaviors of the adult male rats.

Keywords: Behaviors; ELF-EMF; Electromagnetic field; Extremely low frequency.

Fig. 1

Effects of ELF-EMF exposure in open field test. (A) Total distance traveled; (B) accumulative distance in periphery area; (C) accumulative distance in center area; (D) time spent in center area. All the rats were subjected to OFT after 24 weeks exposure. All data were presented as mean ± S.E.M.

Fig. 2

Effects of ELF-EMF exposure in elevated plus maze. (A) Time spent in the open arms; (B) percentage of the time spent in the open arms; (C) total entries into the arms; (D) entries in open arms; (E) percentage of the entries into the open arms. All data were presented as mean ± S.E.M.

Fig. 3

Influence of ELF-EMF exposure in tail suspension test and forced swim test. (A) The immobility time of the TST; (B) the immobility time of the FST. After 24 weeks exposure, the animals were subjected to the TST and FST. The immobility time in the last 4 min was recorded. All data were presented as mean ± S.E.M.

Fig. 4

Effects of ELF-EMF exposure on the behavior in the Morris water maze. (A) The escape latency in learning phase; (B) the accumulative distance traveled before animals arrived the platform in learning phase; (C) accumulative distance traveled in probe trail; (D) times crossing the platform area in probe trail; (E) time spent in the target quadrant in probe trail. The escape latency was draw from the data recorded during the learning phase from day 1 to day 6. On the day 7, the probe trail was carried out with the platform removed and the accumulative distance traveled, times crossing the platform area and time spent in the target quadrant was measured. All data were presented as mean ± S.E.M.

Fig. 5

Effects of ELF-EMF exposure in fear conditioning test. (A) Fear acquisition during the stimulation with 3 tone-foot shock pairings (tone: 2000 Hz, 85 dB, 30 s; foot shock: 1 mA, 2 s); (B) the time percentage of the context related freezing behavior; (C) the time percentage of the tone related freezing behavior. Freezing time of the control and ELF-EMF exposure group were monitored and captured by mounted camera and analyzed by the software program. All data were presented as mean ± S.E.M.

Fig. 6

Effects of ELF-EMF on the morphology and histology of brain. (A) The weight of the brain; (B) the ratio of the brain weight to the body weight; (C) HE staining and immunohistochemistry with NeuN antibody (IHC-NeuN) of the amygdala. The photos were captured in a magnification of 40×. For the amygdala, the brain sections, at level −2.0 mm from bregma were presented and additional landmark structures indicated on the sections are the striatum (S). (D) HE staining of the hippocampus. The left photos were captured in a magnification of 40× and the right photos were captured in a magnification of 200×. For the hippocampus, the brain sections, at level −4.50 mm from bregma were presented and additional landmark structures indicated on the sections are the dorsal lateral geniculate nucleus (DLG). (E) The immunochemistry with Neu-N antibody of the hippocampus. The left photos were captured in a magnification of 40× and the right photos were captured in a magnification of 200×. (F) The neuron density of the CA3 region in the hippocampus. (G) The neuron density of the amygdala. All data were presented as mean ± S.E.M.