Medical/biological study (experimental study)

Neurodevelopmental anomalies of the hippocampus in rats exposed to weak intensity complex magnetic fields throughout gestation.

Published in: Int J Dev Neurosci 2012; 30 (6): 427-433

Aim of study (acc. to author)

To investigate the effect of weak intensity magnetic fields on the prenatal brain development.
Background/further details: Pregnant rats were continuously exposed to one of four intensities during the pregnancy: 1.) 5-20 nT, 2.) 30-50 nT, 3.) 90-580 nT und 4.) 90-1200 nT (n=2 per group). After one year, the male offspring (n=6-7 per group) were used in the open field test and the contextual fear conditioning was examined. Additionally, the number and the structure of hippocampal neurons were analyzed (n=4 per group).
Previous studies showed that there were no differences between rats exposed to a weak magnetic field of 5-20 nT and a control group without any magnetic field. Therefore, in this study, the reference group (5-20 nT) was used as a control.
The experiment was performed twice.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: continuous to different field patterns for 24 h/day during gestation (21 days)
Exposure 1
Main characteristics
Frequency 50 Hz
Type
Exposure duration continuous to different field patterns for 24 h/day during gestation (21 days)
Additional information temporal structures of a complex magnetic field (composite, LTP-like, and non-sinusoidal 50 Hz field)
Exposure setup
Exposure source/structure
Setup details rats kept in one of four identical compartments of a 140 cm x 33 cm x 33 cm plastic cage; identical Herlmholtz coils positioned at each end of the cage; coils created by wrapping 38 cm x 33 cm x 27 cm cartons with 305 m of 30 AWG wire
Parameters
Measurand Value Type Method Remarks
magnetic flux density 20 nT maximum measured B = 5 - 20 nT reference group
magnetic flux density 50 nT maximum measured B = 30 - 50 nT low-intensity group
magnetic flux density 580 nT maximum measured B = 90 - 580 nT medium-intensity group
magnetic flux density 1,200 nT maximum measured B = 590 - 1200 nT high-intensity group
Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Individual analyses of open field related behaviors revealed no significant differences between any of the exposure conditions. In the fear conditioning, it was found that exposure to the low-intensity (30-50 nT) complex magnetic field during prenatal development resulted in a significant reduction of freezing time compared to the reference group (5-20 nT). Additionally, rats exposed to the low-intensity (30-50 nT) complex magnetic field showed anomalies in the cytological and morphological development of the hippocampus (reduction in overall hippocampal size and promoted subtle malformation of some regions) as compared to the reference group (5-20 nT). In contrast, exposure to weaker or stronger intensities of the same complex magnetic field did not interfere with hippocampal development or anxiety behavior.
These findings suggest that prenatal exposure to complex magnetic fields of a narrow intensity window during development could result in subtle but permanent alterations in hippocampal structure and function.
Study character:
  • medical/biological study
  • experimental study
  • full/main study

Study funded by

  • Canadian Institutes of Health Research (CIHR)
  • Natural Sciences and Engineering Research Council of Canada (NSERC)

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