Study type: Medical/biological study (experimental study)

Sudden death in epileptic rats exposed to nocturnal magnetic fields that simulate the shape and the intensity of sudden changes in geomagnetic activity: an experiment in response to Schnabel, Beblo and May med./bio.

By: Persinger MA, McKay BE, O'Donovan CA, Koren SA
Published in: Int J Biometeorol 2005; 49 (4): 256-261
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Aim of study (acc. to author)

To test the hypothesis that sudden unexplained death in some epileptic patients is related to geomagnetic field activity the authors exposed rats in which limbic epilepsy had been induced to experimentally produced magnetic fields designed to simulate sudden storm commencements (SSCs).

Background/further details

Rats were seized with lithium and pilocarpine and the mortality was monitored.
Previous studies with rats had shown that sudden death in groups of rats in which epilepsy had been induced months earlier was associated with the occurrence of SSCs and increased geomagnetic activity during the previous night. Schnabel et al. (see publication 12465) found no relationship between sudden unexplained death in human patients and geomagnetic activity.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 7 Hz
Modulation type: AM
Exposure duration: intermittent, 6 min/hour for 8 hours/night on three consecutive nights
Exposure 2: 300 µHz
Modulation type: AM
Exposure duration: intermittent, 6 min/hour for 8 hours/night on three consecutive nights

Exposure 1

Main characteristics
Frequency 7 Hz
Type
Exposure duration intermittent, 6 min/hour for 8 hours/night on three consecutive nights
Modulation
Modulation type AM
Additional info

Square waves were amplitude modulated in 14 sequential steps with the duration of each plateau being 14 s and 7 s during the first 3 min and 20 s and the last 1 min and 42 s, respectively.
Exposure setup
Exposure source
Chamber 4 plastic cages (3 rats/cage) 32 cm x 32 cm x 45 cm with two of them completely surrounded with Helmholtz coils. The long axis of the cages were oriented in a north-south direction.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 50 nT peak value measured - -
magnetic flux density 10 nT peak value measured - in control cages

Exposure 2

Main characteristics
Frequency 300 µHz
Type
Exposure duration intermittent, 6 min/hour for 8 hours/night on three consecutive nights
Modulation
Modulation type AM
Additional info

Square waves of 7 Hz were amplitude modulated in 14 sequential steps with the duration of each plateau being 14 s and 7 s during the first 3 min and 20 s and the last 1 min and 42 s, respectively.
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 500 nT peak value measured - -
magnetic flux density 10 nT peak value measured - to 40 nT; in the lower cages

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

Whereas 10% of the animals that had been sham-exposed died within 24 h, 60% of the rats that had been exposed to the experimental magnetic fields simulating natural geomagnetic activity died during this period. These data indicate that correlational analyses between sudden unexplained death in epileptic patients and increased geomagnetic activity can be simulated experimentally in epileptic rats and that potential mechanisms might be testable directly.

Study character:

Study funded by