To investigate whether an extremely low frequency magnetic field influences the glutamate release in the hippocampus of mice and to examine possible molecular mechanism, as well as the effects of lotus seedpod procyanidins (LSPC) administration.
In a previous study, the authors found that exposure to extremely low frequency magnetic fields could induce oxidative stress and influence the cognitive performance in mice and that an administration of LSPCs could prevent those impairments (Duan et al., 2013). However, the molecular mechanisms remained unknown.
Five groups of mice were examined (n=10 per group): 1.) sham exposure, 2.) exposure, 3.) exposure + 30 mg/kg LSPC, 4.) exposure + 60 mg/kg LSPC and 5.) exposure + 90 mg/kg LSPC. The LSPCs were administered daily for 43 days (15 days before the exposure and during the 28 days of exposure).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
4 h/day for 28 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | 4 h/day for 28 days |
| Exposure source | |
|---|---|
| Chamber | mice were exposed in well ventilated perspex boxes (14 cm x 10 cm x 12 cm) and these boxes were placed in the middle of the coils, temperature in the boxes was 23 ± 0.5°C |
| Setup | pair of helmholtz coils (1 mm wire diameter, 32 cm internal diameter, 36 cm external diameter) with 500 turns was used; exposure device was placed in a temperature controlled room (23 ± 2°C) |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 8 mT | - | measured | - | - |
In the hippocampus of exposed mice, the concentrations of glutamate, gamma aminobutyric acid, calcium ions and the protein expression level of the NMDA receptor subunit NR2B were significantly increased in comparison to the control group. An administration of LSPCs significantly attenuated these effects or diminished them completely.
The magnetic field exposure induced significant changes in the activation of the mitogen-activated protein kinase pathway. The ratios of phosphorylated ERK-1 to ERK-1 and of phosphorylated ERK-2 to ERK-2 were significantly decreased in the exposure group compared to the control group. These decreases were attenuated by a treatment with LSPCs. Furthermore, in the exposure group the protein expression level of ASK1 and the ratios of phosphorylated JNK-1 to JNK-1 and of phosphorylated JNK-2 to JNK-2 were significantly increased in comparison to the control group. An administration of LSPCs significantly attenuated these effects or diminished them completely.
In the hippocampus of mice from the exposure group, the ratio of phosphorylated CREB to CREB was significantly decreased when compared to the control group, while an administration of LSPCs attenuated this effect significantly.
The results suggest that extremely low frequency magnetic fields could alter the level of glutamate and influence the mitogen-activated protein kinase pathway in the hippocampus of mice. An administration of LSPCs could prevent those molecular changes and therefore the cognitive impairments reported in the previous examinations (Duan et al., 2013).
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