To study the effects of a seven-day exposure to an extremely low frequency magnetic field on different behaviour parameters in gerbils of different age. The behaviour parameters were investigated on the 1st, 2nd, 4th, and 7th day of exposure (immediate effect) and three days after exposure has been ceased (delayed effect).
The following main groups were investigated: three-month-old male gerbils (n = 35) and ten-month-old male gerbils (n = 35).
The animals were divided into two control groups (cage control and sham exposed) and three exposure groups (0.1, 0.25 and 0.5 mT).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 7 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 7 days |
| Exposure source | |
|---|---|
| Chamber | gerbils were exposed in standard polycarbonate cages (26 cm x 43 cm x 15 cm); simultaneously, two cages with 3-4 gerbils were placed in the vicinity of ELF-MF source for 7 days, one on the left side of the electromagnet and another on the right side |
| Setup | electromagnet with a regular laminated transformer core and pole diameter of 9.5 cm; the center of each cage was at 20, 28 and 40 cm from the electromagnetic poles |
| Sham exposure | A sham exposure was conducted. |
| Additional info | the electromagnet was supplied with a sinusoidal current (50 Hz, 40 V, 4.5 A) |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 8.9 mT | maximum | measured | - | on the electromagnetic poles |
| magnetic flux density | 0.5 mT | mean | - | - | at a distance of 20 cm |
| magnetic flux density | 0.25 mT | mean | - | - | at a distance of 28 cm |
| magnetic flux density | 0.1 mT | mean | - | - | at a distance of 40 cm |
Exposure to an extremely low frequency magnetic field for seven days (0.1, 0.25 and 0.5 mT) stimulated motor behaviour (locomotor activity and stereotypy) in 3-month-old gerbils, whereby the most significant changes were observed after the first day of exposure. Simultaneously, a significant reduction of immobility during the entire period of the seven-day exposure was reported. Additionally, exposure to the different extremely low frequency magnetic fields had a delayed effect (except 0.25 mT) on stereotypy (decrease) and immobility (increase).
The effect of the extremely low frequency magnetic fields on the behaviour of ten-month-old gerbils largely depended on the value of the electromagnetic induction. On the first exposure day an extremely low frequency magnetic field of 0.1mT decreased, 0.25 mT had no effect and 0.5 mT increased motor behaviour (locomotor activity and stereotypy). But a significant increase of motor behaviour after the second day of exposure with 0.25 mT was reported. Furthermore, a significant reduction of immobility during the entire period of the seven-day exposure to 0.5 mT was noticed.
Three days after exposure has been ceased (delayed effect), significant stimulation of motor behaviour and reduction of immobility time was observed in all exposed groups compared to the control group.
In conclusion, the results revealed the specific temporal patterns of immediate and delayed motor behaviour changes in three- and ten-month-old gerbils induced by extremely low frequency magnetic fields, which could be due to age-dependent differences in the brain structures (responsible for a control of motor behaviour).
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