Study type: Medical/biological study (experimental study)

Exposure to extremely low-frequency (50 Hz) electromagnetic fields enhances adult hippocampal neurogenesis in C57BL/6 mice. med./bio.

Published in: Exp Neurol 2010; 226 (1): 173-182

Aim of study (acc. to author)

To study whether 50 Hz extremely low frequency electromagnetic field exposure affects adult hippocampal neurogenesis in vivo, and if so, to identify the molecular mechanisms underlying this action and its functional impact on synaptic plasticity.

Background/further details

ln a previous study (Piacentini et al. 2008), the authors demonstrated that exposure to extremely low frequency electromagnetic fields significantly enhances the neuronal differentiation of cortical neural stem cells in vitro and this effect is mediated by the upregulation of Cav1-calcium channel expression and activity.
71 mice were divided into an exposure group (n=38) and a sham exposure group (n=33): three exposed animals were used for RT-PCR and three for Western blot analysis on day four (on day four, because modulation of gene expression of transcription factors should precede the differentiation process). 14 exposed animals were used for immunofluorescence analysis on day seven (24 h after the final exposure session) and five mice on day 37 (30 days after exposure to study survival and integration of newly generated neurons). Additionally, 13 exposed animals were used for long-term potentiation experiments on day 37.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: continuous for 7 h/day on 4 days
expression of specific genes and proteins
Exposure 2: 50 Hz
Exposure duration: continuous for 1 h/day (n=3 mice), 3 h/day (n=3) or 7 h/day (n=13) on 7 days
Exposure 3: 50 Hz
Exposure duration: continuous for 7 h/day on 7 days

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Exposure duration continuous for 7 h/day on 4 days
Additional info expression of specific genes and proteins
Exposure setup
Exposure source
Setup mouse placed in a plastic cage inside a Plexiglas cylinder with a diameter of 20 cm that was positioned inside a solenoid
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Exposure duration continuous for 1 h/day (n=3 mice), 3 h/day (n=3) or 7 h/day (n=13) on 7 days
Additional info neuronal differentiation (immune reactivity)
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Additional info injection of 5-bromodeoxyuridine before exposure
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Exposure duration continuous for 7 h/day on 7 days
Additional info synaptic plasticity and immune reactivity
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Additional info injection of 5-bromo-deoxyuridine before exposure
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Extremely low frequency electromagnetic field exposure for seven days significantly enhanced neurogenesis in the dentate gyrus of adult mice, as shown by increased numbers of cells double-labeled (immune reactive) for BrdU and doublecortin (a marker for immature neurons).
Quantitative RT-PCR analysis of hippocampal extracts revealed significant exposure-induced increases in the gene expression of pro-neuronal genes (Mash1, NeuroD2, Hes1) and genes encoding Cav1.2 calcium channel alpha1C subunits. Increased protein expression of NeuroD1, NeuroD2 and Cav1 channels was also found by Western blot analysis.
Immunofluorescence experiments showed that 30 days after exposure roughly half of the newly generated immature neurons had survived and became mature dentate gyrus granule cells (as shown by their immune reactivity for both BrdU and NeuN, a marker for differentiated neurons) and were integrated into the granule cell layer of the dentate gyrus.
Electrophysiological experiments demonstrated that the new mature neurons influenced hippocampal synaptic plasticity, as reflected by increased long-term potentiation.
The data show that extremely low frequency electromagnetic field exposure can be an effective tool for increasing in vivo neurogenesis, and they could lead to the development of novel therapeutic approaches in regenerative medicine.

Study character:

Study funded by

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