The effects of exposure to a 50 Hz magnetic field on cognitive functions and hippocampal neurogenesis in rats with cerebral ischemia should be investigated.
The study background was the potential application of extremely low frequency magnetic fields in the treatment of cerebral ischemia and other diseases in the central nervous system.
Rats underwent surgery to create models of middle cerebral artery occlusion/reperfusion and were afterwards divided into an exposure group and sham exposure group (n=12 each). Moreover, rats with sham surgery, i.e., without cerebral artery occlusion, were sham exposed as negative controls (n=12). Exposure and sham exposure started 24 hours after the surgery. Six rats were randomly selected from each group for BrdU injections from day 4 to day 7 and all were sacrificed on day 29 after the surgery. The acquisition training and the probe trial for Morris water maze were performed with the same rats on days 24 and 29 after surgery. Six other rats from each group were sacrificed on the 7th day after the surgery for protein expression analysis.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
2 hours/day for 28 successive days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | 2 hours/day for 28 successive days |
| Exposure source | |
|---|---|
| Chamber | plastic cages |
| Setup | the exposure device consisted of Helmholtz coils (two parallel solenoids (diameter: 40 cm) 20 cm apart); both coils were made of 300 turns of copper wire (0.8 mm diameter); without restraint, 6 rats in a cage were placed into the coils; the room temperature was maintained at 20 ± 2°C, while the temperature between the coils was between 21.5°C and 22°C when the device was activated |
| Sham exposure | A sham exposure was conducted. |
| Additional info | the sham exposure group and the negative control group were put into plastic cages with the same procedure as the exposure group but without magnetic field exposure |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | - | measured and calculated | - | ± 0.05 mT |
Exposed rats required significantly shorter swimming distances and latencies and spent significantly more time in the target quadrant in the Morris water maze test compared to sham exposed rats. The number of BrdU+/NeuN+ cells, representing newly developed neurons, in the hippocampal subgranular zone was significantly increased in exposed rats compared to the sham exposure group. Moreover, the protein expression of Notch1, Hes1, and Hes5 proteins, which are the key factors of the Notch signaling pathway, was significantly higher in exposed rats compared to sham exposed rats.
The authors conclude that exposure to a 50 Hz magnetic field might enhance cognitive functions and hippocampal neurogenesis in rats with cerebral ischemia, possibly by affecting the Notch signaling pathway.
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