Medical/biological study (experimental study)

Influence of extremely low frequency magnetic fields on Ca2+ signaling and NMDA receptor functions in rat hippocampus med./bio.

By: Manikonda PK, Rajendra P, Devendranath D, Gunasekaran B, Channakeshava, Aradhya RS, Sashidhar RB, Subramanyam C

Published in: Neurosci Lett 2007; 413 (2): 145-149

Aim of study (acc. to editor)

This study was performed to analyze the effects of an extremely low frequency magnetic field on Ca²⁺-dependent enzyme activities and its possible relation to NMDA receptor function in rat hippocampus.

Background/further details

Hippocampi were obtained from brains of 3 weeks old rats. Three exposure groups were performed with six animals each.

Endpoint

effects on the neurological system: effects on hippocampus (intracellular Ca²⁺ level, Ca²⁺-dependent enzyme activities, NMDA receptor function)

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 90 days	magnetic flux density: 50 µT average over time magnetic flux density: 100 µT average over time

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	90 days

Exposure setup

Exposure source	Helmholtz coils
Chamber	animal movements were measured with a photoelectric sensor connected to the base of the cage and a digital counter
Setup	two sets of Helmholtz coils with 25 turns each
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	50 µT	average over time	measured	-	-
magnetic flux density	100 µT	average over time	measured	-	-

Exposed system:

animal
rat/Wistar
whole body

Methods Endpoint/measurement parameters/methodology

cell function: intracellular Ca²⁺ level (spectrophotometry), Ca²⁺-dependent enzyme activities (several protein kinases; different radioactive measurement procedures, ELISA)
effects on the neurological system: NMDA receptor function ([³H] glutamate binding assay, scintillation counter)
physical activity (movements, photoelectronic sensor), body weight, body temperature, general health

Investigated system:

isolated bio./chem. substance
intact cell/cell culture
cell extracts
investigation on living organism

Time of investigation:

after exposure

Main outcome of study (acc. to author)

Exposed rats exhibited increased physical activity, especially during night periods, compared to the control group.
The exposure to the extremely low frequency magnetic field caused increased intracellular Ca²⁺ level concomitant with increased Ca²⁺-dependent enzyme activities (protein kinase C, cAMP-dependent protein kinase and calcineurin (a protein phosphatase)) as well as a decreased activity of Ca²⁺-calmodulin-dependent protein kinase in the hippocampus. Additionally, decreased glutamate binding to NMDA receptors were revealed, indicating lower activation of this receptor.
The results of this study were more pronounced in magnetic flux density of 100 µT compared to 50 µT.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Central Power Research Institute (CPRI), Ministry of Power, India

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