Medical/biological study (experimental study)

Extremely low-frequency magnetic fields modulate nitric oxide signaling in rat brain med./bio.

By: Cho SI, Nam YS, Chu LY, Lee JH, Bang JS, Kim HR, Kim HC, Lee YJ, Kim HD, Sul JD, Kim D, Chung YH, Jeong JH

Published in: Bioelectromagnetics 2012; 33 (7): 568-574

Aim of study (acc. to author)

The study was designed to confirm that an extremely low frequency magnetic field affects neuronal nitric oxide synthase (nNOS) in several brain regions and to investigate the correlation between nitric oxide and nNOS activation.

Background/further details

A previous study showed that an extremely low frequency magnetic field induces nitric oxide synthesis by Ca²⁺-dependent NO synthase in the rat brain (Jeong et al. 2006). In the central nervous system, nitric oxide derived from nNOS acts as a neuromodulator or neurotransmitter for the regulation of synaptic plasticity, the sleep-wake cycle and hormone secretion.
10 rats were exposed and 10 rats were sham exposed.

Endpoint

effects on the neurological system: nitric oxide signaling in the brain

Exposure

- 60 Hz
- 50/60 Hz
- magnetic field
- low frequency

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: continuous for 5 days	magnetic flux density: 2 mT effective value (at the center of the cage) magnetic flux density: 1.8 mT effective value (at the corner of the cage)

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Exposure duration	continuous for 5 days

Exposure setup

Exposure source	Helmholtz coils
Setup	pair of Helmholtz coils, consisting of 200 turns of insulated copper wire with a diameter of 1 mm, wound on a 140 cm x 85 cm x 70 cm rectangular wooden frame; each winding was split; maximum magnetic field in the center of the coil system; non-magnetic cage placed in the center
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	2 mT	effective value	measured	-	at the center of the cage
magnetic flux density	1.8 mT	effective value	measured	-	at the corner of the cage

Additional parameter details

ambient horizontal field: B =18 µT ambient vertical field: B = 22 µT total ambient field: B = 23 µT ambient AC field: B < 2 µT

Exposed system:

Methods Endpoint/measurement parameters/methodology

effects on the neurological system: nitric oxide levels in the cortex, striatum, hippocampus (spectrophotometry), intracellular cyclic guanosine monophosphate (cGMP) activation (cGMP levels in the cortex, striatum, hippocampus; ELISA); morphological assessment of nuclear and mitochondrial damage in hippocampus, cell loss and morphology of the cerebral cortex, striatum and hippocampus (cresyl violet staining, electron microscopy); number of nNOS-immunoreactive neurons in the cortex, striatum, hippocampus (immunohistochemistry and densitometry);

Investigated system:

isolated bio./chem. substance
intact cell/cell culture
brain homogenates and supernatants; cell lysates

Investigated organ system:

brain/CNS

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The exposure of the rats to the magnetic field for 5 days resulted in significant increases of the nitric oxide level in the cerebral cortex, striatum, and hippocampus and in a significant elevation of the cGMP level in the striatum in comparison to the control group. There were no significant differences in the morphology and number of neurons in the cerebral cortex, striatum, and hippocampus. However, the number of nNOS-immunoreactive neurons were significantly increased in those cerebral areas in exposed rats.
These data suggest that the increase in nitric oxide could be due to the increased expression and activation of nNOS. In conclusion, the extremely low frequency magnetic field exposure was able to increase the nitric oxide production via nNOS activation in the brain of the rats.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Education, Science and Technology (MEST), Korea
National Research Foundation (NRF) of Korea

Djordjevic NZ et al. (2017): Anxiety-like behavioural effects of extremely low-frequency electromagnetic field in rats
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Chung YH et al. (2015): Extremely low frequency magnetic field modulates the level of neurotransmitters
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Jeong JH et al. (2006): Extremely low frequency magnetic field induces hyperalgesia in mice modulated by nitric oxide synthesis
Noda Y et al. (2000): Pulsed magnetic fields enhance nitric oxide synthase activity in rat cerebellum
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