Study type: Medical/biological study (experimental study)

Amplification of evoked potentials recorded from mouse hippocampal slices by very low repetition rate pulsed magnetic fields med./bio.

By: Wieraszko A
Published in: Bioelectromagnetics 2004; 25 (7): 537-544
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Aim of study (acc. to author)

To investigate the effects of pulsed magnetic fields at a very low repetition rate on evoked potential in vitro from mouse hippocampal slices.

Background/further details

Two different experimental protocols were applied: In protocol A the magnetic field with a constant strength of 15 mT was used within a frequency range from 0.03 to 0.5 Hz. In protocol B a field of variable intensity from 9 to 15 mT and with different duration cycles from 5 to 10 minutes was used.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
Exposure duration: intermittent: 1, 3, 5, 7, and 15 s on/off, for 30 min
protocol A
Exposure 2:
Exposure duration: intermittent, 20 s on/off, for a total of 10 min 40 s
protocol B, paradigm 1
Exposure 3:
Exposure duration: intermittent, 5 s on/off, for a total of 6 min 30 s
protocol B, paradigm 2
Exposure 4:
Exposure duration: intermittent, 2 s on/off, for a total of 3 min 15 s
protocol B, paradigm 3

General information

In experiments applying protocol B, the hippocampal slices were divided into three groups that were exposed to different combinations of three paradigms: all three paradigms successively, paradigm 1 followed immediately by paradigm 2, or paradigm 1 alone.

Exposure 1

Main characteristics
Frequency
Type
Exposure duration intermittent: 1, 3, 5, 7, and 15 s on/off, for 30 min
Additional info protocol A
Additional info protocol A
Exposure setup
Exposure source
Chamber The cylindrical slice chamber was surrounded by a water-containing chamber inserted into a circular acrylic frame (19 cm in diameter) that was vertically streamed by a constant flow of cooling air and surrounded by four coils (96 turns) mounted perpendicularly to the plane of the slice.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 15 mT - measured - -

Exposure 2

Main characteristics
Frequency
Type
Exposure duration intermittent, 20 s on/off, for a total of 10 min 40 s
Additional info protocol B, paradigm 1
Additional info protocol B, paradigm 1
Exposure setup
Exposure source
Additional info The 9 mT and 12 mT cycles were repeated 4 times, and the 15 mT cycle was repeated 8 times.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 9 mT - measured - -
magnetic flux density 12 mT - measured - -
magnetic flux density 15 mT - measured - -

Exposure 3

Main characteristics
Frequency
Type
Exposure duration intermittent, 5 s on/off, for a total of 6 min 30 s
Additional info protocol B, paradigm 2
Additional info protocol B, paradigm 2
Exposure setup
Exposure source
Additional info The on/off cycle was repeated 9 times, followed by a 20 s break and 6 more repetitions. Another 220 s break followed before initiation of paradigm 3.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 15 mT - measured - -

Exposure 4

Main characteristics
Frequency
Type
Exposure duration intermittent, 2 s on/off, for a total of 3 min 15 s
Additional info protocol B, paradigm 3
Additional info protocol B, paradigm 3
Exposure setup
Exposure source
Additional info The on/off cycle was repeated 12, 4, 3, 5, and 6 times followed by 30, 10, 25, and 10 s breaks, respectively.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 15 mT - measured - -

Reference articles

  • Fuller M et al. (2003): On the confirmation of an effect of magnetic fields on the interictal firing rate of epileptic patients
  • Dobson J et al. (2000): Changes in paroxysmal brainwave patterns of epileptics by weak-field magnetic stimulation
  • Dobson J et al. (2000): Analysis of EEG data from weak-field magnetic stimulation of mesial temporal lobe epilepsy patients

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

A frequency-dependent amplification of the potentials was found whilst magnetic fields were applied according to protocol A. At this a frequency of 0.16 Hz was the most effective. An increase in the magnitude of the spikes were found caused by magnetic field exposure according to protocol B.
The results of this study demonstrate the influence of the applied magnetic fields on the nervous system.

Study character:

Study funded by

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