Study type: Medical/biological study (experimental study)

Modification of the synaptic glutamate turnover in the hippocampal tissue exposed to low-frequency, pulsed magnetic fields. med./bio.

Published in: Brain Res 2005; 1052 (2): 232-235

Aim of study (acc. to author)

To study the influence of pulsed magnetic fields on the release (during exposure) and uptake (after exposure) of glutamate in the hippocampal tissue.

Background/further details

The release was examined by using hippocampal slices (of mice), the uptake process was characterized by the use of synaptosomes obtained from hippocampal slices.
Patterns of magnetic fields were applied, which induced seizures in hippocampal tissue in vitro and epileptic episodes in preclinical trials.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 25 mHz
Exposure duration: 640 s
Exposure 2: 25–100 mHz
Exposure duration: 3340 s
Paradigm 1+2
Exposure 3: 25–250 mHz
Exposure duration: 6095 s
Paradigm 1+2+3

Exposure 1

Main characteristics
Frequency 25 mHz
Type
Waveform
  • rectangular
Exposure duration 640 s
Additional info Paradigm 1
Additional info Paradigm 1(0.025 Hz) is given as: 9 mT, 12 mT and 15 mT MF with 20 s on/off cycle applied 4, 4 and 8 times, respectively. The exposure time pattern of E1 is calculated as follows: 20 s pulse on + 20 s pulse off multiplied by the number of repetitions which was 4 + 4 + 8.
Exposure setup
Exposure source
Setup The tissue chamber was surrounded by four magnetic coils.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 12 mT unspecified unspecified - -
magnetic flux density 15 mT unspecified unspecified - -
magnetic flux density 9 mT unspecified unspecified - -

Exposure 2

Main characteristics
Frequency 25–100 mHz
Type
Waveform
  • rectangular
Exposure duration 3340 s
Additional info Paradigm 1+2
Additional info Paradigm 1 (0.025 Hz) + Paradigm 2 (0.1 Hz) were applied. Paradigm 2 is given: 15 mT and another 15 mT MF with 5 s on/off cycle applied 9 and 6 times, respectively. The exposure time pattern of E2 is calculated as follows: Exposure time pattern of E1 + (5 s on + 5 s off + 20 s pause + 5 s on + 5 s off + 220 s multiplied by # of repetitions which was 9 + 6).
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 9 mT unspecified unspecified - -
magnetic flux density 12 mT unspecified unspecified - -
magnetic flux density 15 mT unspecified unspecified - -

Exposure 3

Main characteristics
Frequency 25–250 mHz
Type
Waveform
  • rectangular
Exposure duration 6095 s
Additional info Paradigm 1+2+3
Additional info Paradigm 1 (0.025 Hz) + Paradigm 2 (0.1 Hz) + Paradigm 3(0.25 Hz) were applied. Paradigm 3 is given as: 15 mT with 2 s on/off cycle applied 12, 4, 3, 5 and 6 times. The exposure time pattern of E3 is calculated as follows: Exposure time pattern of E2 + (2 s on + 2 s off + 30 s pause + 2 s on + 2 s off + 10 s pause + 2 s on + 2 s off + 25 s pause + 2 s on + 2 s off + 10 pause + 2 s on + 2 s off multiplied by # of repetitions which was 12+4+3+5+6).
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 9 mT unspecified unspecified - -
magnetic flux density 12 mT unspecified unspecified - -
magnetic flux density 15 mT unspecified unspecified - -

Reference articles

  • Wieraszko A (2004): Amplification of evoked potentials recorded from mouse hippocampal slices by very low repetition rate pulsed magnetic fields.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The pulsed magnetic fields (9-15 mT) amplified and attenuated the release and uptake of glutamate, respectively. However, the magnetic fields which induced an increase in neuronal excitability without concomitant seizures amplified both processes.
These data indicate that the glutamergic synapses are the target of magnetic fields action. The results show that modulation of glutamate turnover by magnetic fields correlates with overexcitability of hippocampal neurons and with epileptic episodes observed in the hippocampus of the patients exposed to magnetic fields. Pulsed magnetic field stimulation has the potential to be used as a diagnostic procedure which could help to localize the seizure-generating part of the brain.

Study character:

Study funded by

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