To investigate the involvement of dopamine, serotonin and nitric oxide in extremely low frequency magnetic field-induced obsessive compulsive disorder-like behavior in mice.
Three experiments were performed:
In the first experiment, several groups of mice (n=8 per group) were subjected to behavioral tests. They were exposed or sham exposed for 7, 30, 60, 90 or 120 days. For the examination of the obsessive compulsive disorder-like behavior and for the determination of the locomotor activity, separate groups were employed.
In the second experiment, the levels of dopamine, serotonin and nitric oxide in the brain were determined after 120 days of sham exposure (n=8) or exposure (n=8).
In the third experiment, the influence of different nitric oxide modulators on behavior and levels of dopamine, serotonin and nitric oxide in the brain were examined. Mice were exposed or sham exposed for 120 days and received daily injections of saline solution (as a control), L-NAME (inhibitor of nitric oxide synthase; 15, 30 or 45 mg per kg body weight), L-ARG (nitric oxide precursor; 200, 400 or 800 mg per kg body weight) or 7-NI (inhibitor of nitric oxide synthase; 10, 20 or 40 mg per kg body weight) before the exposure/sham exposure. Separate groups (n=8 per group) were employed for each dose and examination.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
8 hours/day for 7, 30, 60, 90 or 120 days
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | 8 hours/day for 7, 30, 60, 90 or 120 days |
| Exposure source | |
|---|---|
| Chamber | mice were housed in a clean plastic cage which was positioned on the center of the platform of the coils |
| Setup | Helmholtz coils, spaced apart at a distance equal to their radii (45 cm); instrument was constructed by winding glaze-insulated copper wire (d = 1.2 mm) 100 times on wooden frames; both the coils were individually attached to regulated AC power supply through step down transformer (12 V) which acted as an isolator |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | - | measured | - | - |
The first experiment revealed that magnetic field exposed mice buried significant more marbles than sham exposed mice. Furthermore, this effect was time dependent: The longer the mice were exposed the more marbles were buried and the more significant was the result. No significant differences between any of the groups were found regarding locomotor activity.
In the second experiment, no significant effect of the exposure on the levels of dopamine and serotonin in the brain of the mice was observed. However, exposure led to significantly increased nitric oxide levels in the cortex, hippocampus and hypothalamus when compared to the corresponding sham exposure.
In the third experiment, it was shown that the combination of the magnetic field exposure and the nitric oxide precursor L-ARG led to a further significant increase in the number of buried marbles compared to the magnetic field exposure alone, while the nitric oxide synthase inhibitors L-NAME and 7-NI significantly attenuated the exposure induced effect.
The authors conclude that exposure to extremely low frequency magnetic fields could induce obsessive compulsive disorder-like behavior in mice and that this effect appears to be associated with nitric oxide synthase activation.
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