To study whether a low-energy component of echo planar magnetic resonance spectroscopic imaging (low-field magnetic stimulation) has antidepressant-like, locomotor-stimulating, or amnestic effects in rats. The forced swim test was used.
The forced swim test is an animal model often used in the study of depression. It is a 2-day helplessness procedure in which rats swim under conditions in which escape is not possible.
Additionally, the effects on activity in an open field were examined to ensure that the effects that were observed in the forced swim test were not due to nonspecific effects on locomotion.
Rats were also used to confirm the efficacy of systemic doses of the standard antidepressant drugs fluoxetine or desipramine in the forced swim test.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
1 kHz
Exposure duration:
20 min
|
|
|
Exposure 2:
Exposure duration:
20 min
|
- |
Following treatments were used: LFMS (low field magnetic stimulation) within the focal point of the field, LFMS outside the focal point (10% LFMS), no field, constant DC, fluoxetine (20 mg/kg, IP) and desipramine (10 mg/kg, IP).
| Frequency | 1 kHz |
|---|---|
| Type | |
| Waveform |
|
| Exposure duration | 20 min |
| Modulation type | cf. additional info |
|---|---|
| Additional info |
Low field magnetic stimulation (LMFS) consisting of 512 alternating trapezoids of 1 ms each. Electric field consisting of 512 square electric pulses of 0.25 ms each. |
| Exposure source | |
|---|---|
| Chamber | exposure cylinder/35.56 cm in diameter x 45.72 cm long x 1.59 cm think |
| Setup | 1h, 19 h or 23 h after forced swimming session, the rats were restrained individually in a plastic tube which was placed in the exposure cylinder. At 24 hours after the forced swim, rats were retested for 5 min under identical conditions. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 600 µT | peak value | unspecified | - | in the head at 4 cm; gradient magnetic field of 150 µT/cm |
| electric field strength | 7.5 mV/cm | peak value | calculated | - | - |
| Frequency | |
|---|---|
| Type | |
| Exposure duration | 20 min |
| Additional info | direct current magnetic field |
| Exposure source |
|
|---|
No parameters are specified for this exposure.
Low-field magnetic stimulation reduced immobility in the forced swim test, an antidepressant-like effect similar to that of standard antidepressants. Low-field magnetic stimulation did not alter locomotor activity or fear conditioning.
In conclusion, low-field magnetic stimulation has antidepressant-like effects in rats that seem unrelated to locomotor-activating or amnestic effects. These data raise the possibility that electromagnetic fields can affect the brain biology and might have physiologic consequences that offer novel approaches to therapy for psychiatric disorders.
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