Medical/biological study (experimental study)

Exposure to extremely low-frequency magnetic field restores spinal cord injury-induced tonic pain and its related neurotransmitter concentration in the brain med./bio.

By: Kumar S, Jain S, Velpandian T, Petrovich Gerasimenko Y, D Avelev V, Behari J, Behari M, Mathur R

Published in: Electromagn Biol Med 2013; 32 (4): 471-483

Aim of study (acc. to author)

To examine the effect of magnetic field exposure on the tonic pain behavior and related neurotransmitters in the brain of rats with spinal cord injury.

Background/further details

Rats were divided into three groups for behavioral and neurochemical experiments: 1.) sham operated group (n=8), 2.) spinal cord injury group (n=6) and 3.) spinal cord injury + magnetic field exposure group (n=6). The same number and groups of rats were used for the histological experiment.
After the spinal cord injury, rats were exposed or kept without exposure for 8 weeks. Locomotor activity was assessed weekly while nociception was only recorded at the end of the 8 weeks before rats were sacrified wfor histological and neurotransmitter concentration examination.

Endpoint

effects on the neurological system: neurotransmitter concentration in the brain, morphology of spinal cord
cognitive/behavioral endpoints: locomotor behavior, nociception

Exposure

- 50 Hz
- 50/60 Hz
- magnetic field
- therapeutic/medical device

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 2 h/day for 7 days/week for 8 weeks	magnetic flux density: 17.96 µT effective value

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	2 h/day for 7 days/week for 8 weeks

Exposure setup

Exposure source	coil(s)
Chamber	rats were exposed in a non-metal box
Setup	box was placed at the center of four coils connected in series to 50 Hz power supply; coils were wound on circular formers at a diameter of 1000 mm; two outer coils were wound with 18 turns each and two inner coils were wound with 8 turns, respectively; coils produced a uniform magnetic field

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	17.96 µT	effective value	measured	-	-

Reference articles

Kirschvink JL (1992): Uniform magnetic fields and double-wrapped coil systems: improved techniques for the design of bioelectromagnetic experiments

Exposed system:

animal
rat/ Wistar
whole body

Methods Endpoint/measurement parameters/methodology

morphol./histopathol. changes: morphology of spinal cord (microscopy)
effects on the neurological system: concentration of the neurotransmitters serotonin, gamma aminobutyric acid, glutamate, dopamine, norepinephrine and glycine in the brain (high performance liquid chromatography, mass spectrometry)
cognitive/behavioral endpoints: locomotor activity (open field test); nociception (injection of formalin solution into the left dorsal hindpaw, classification in pain categories from 0 (no pain) to 3 (excessive pain); number of flinch, bite and lick)

Investigated system:

isolated bio./chem. substance
tissue slices
brain homogenate (cortex, brain stem and rest of brain)
investigation on living organism

Investigated organ system:

Time of investigation:

during exposure
after exposure

Main outcome of study (acc. to author)

Rats with spinal cord injury showed a significantly reduced locomotor activity compared to the sham group. However, locomotor activity was significantly higher in the "spinal cord injury with magnetic field exposure group" than in the group with spinal cord injury alone.
Pain after formalin injection was significantly decreased in rats with spinal cord injury compared to the sham group, while magnetic field exposure in spinal cord injured rats significantly increased the level of pain compared to rats with spinal cord injury alone.
In spinal cord injured rats, the concentration of serotonin was significantly lower in the cortex and in the rest of the brain in comparison to the sham group, while the concentrations of gamma aminobutyric acid and norepinephrine in the brain stem were significantly increased. A magnetic field exposure diminished these effetcs.
Morphological analysis revealed clear lesions in the spinal cord of spinal cord injured rats with and without magnetic field exposure. However, lesion volume was significantly less in the spinal cord injury group with magnetic field exposure.
The authors conclude that the neurotransmitter changes contribute toward the decreased pain in spinal cord injured rats which is restored by long-term exposure to extremely low frequency magnetic fields.

Study character:

medical/biological study
experimental study
full/main study
blind study

Study funded by

Department of Science and Technology (DST), India

Bhattacharyya S et al. (2020): Effect of Low Intensity Magnetic Field Stimulation on Calcium-Mediated Cytotoxicity After Mild Spinal Cord Contusion Injury in Rats
Ozdemir E et al. (2017): Effects of extremely low frequency electromagnetic fields on morphine analgesia and tolerance in rats
Chung YH et al. (2015): Extremely low frequency magnetic field modulates the level of neurotransmitters
Pal A et al. (2013): Iron oxide nanoparticles and magnetic field exposure promote functional recovery by attenuating free radical-induced damage in rats with spinal cord transection
Das S et al. (2012): Exposure to ELF- magnetic field promotes restoration of sensori-motor functions in adult rats with hemisection of thoracic spinal cord
Kosar MI et al. (2012): Antinociceptive Effects in Normal and Diabetic Rats Exposed to 50 Hz Magnetic Field
Rakesh RM et al. (2008): Threshold of pain in chronic magnetic field- (50 Hz, 17.9 microT) exposed rats: effect of sucrose ingestion
Jeong JH et al. (2006): Extremely low frequency magnetic field induces hyperalgesia in mice modulated by nitric oxide synthesis
Jeong JH et al. (2005): Benzodiazepine system is involved in hyperalgesia in rats induced by the exposure to extremely low frequency magnetic fields