Medical/biological study (experimental study)

Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse med./bio.

By: Sun ZC, Ge JL, Guo B, Guo J, Hao M, Wu YC, Lin YA, La T, Yao PT, Mei YA, Feng Y, Xue L

Published in: Sci Rep 2016; 6: 21774

Aim of study (acc. to author)

The effects of exposure of young mice to a 50 Hz magnetic field on synaptic transmission and synaptic plasticity in the brain should be investigated.

Background/further details

Investigations were conducted at the Calyx of Held, a particularly large synapse in the mammalian brain.
Exposure started on the day of birth.

Endpoint

effects on the neurological system: synaptic transmission and synaptic plasticity in the mouse brain

Exposure

- 50 Hz
- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous for 8 to 10 days	magnetic flux density: 1 mT

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	continuous for 8 to 10 days

Exposure setup

Exposure source	Helmholtz coils

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	-	measured	-	-

Reference articles

He YL et al. (2013): Exposure to Extremely Low-Frequency Electromagnetic Fields Modulates Na(+) Currents in Rat Cerebellar Granule Cells through Increase of AA/PGE(2) and EP Receptor-Mediated cAMP/PKA Pathway

Exposed system:

animal
mouse/C57
whole body

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: protein expression (Western blot) and gene expression (real-time RT-PCR) of calcium ion channels (total and P/Q, N and R subtypes) at presynaptic nerve terminals
effects on the neurological system: electrophysiology and synaptic plasticity in brain slices: frequency and amplitude of excitatory postsynaptic currents, exocytosis, size of the readily releasable pool (directly usable vesicle pool), slow and rapid endocytosis of synaptic vesicles, endocytosis overshoot and bulk endocytosis (via calcium currents and membrane capacitance) and post-tetanic potentiation (a form of short-term plasticity) at the presynaptic nerve terminal (triggering of action potentials via electric stimulus, measurement via voltage-clamp technique)

Investigated system:

isolated bio./chem. substance
organelle/cell part
tissue slices
brain synapses (Calyx of Held)

Time of investigation:

after exposure

Main outcome of study (acc. to author)

Compared to the control group, exposure to the magnetic field significantly increased the calcium influx upon electrical stimulation and all forms of vesicle endocytosis. However, exposure did not affect the size of the readily releasable pool or exocytosis.
Exposure to the magnetic field also significantly increased the amplitude of post-tetanic potentiation compared to the control group without influencing its time course.
Investigating the underlying mechanisms of action, a significantly increased protein expression and gene expression of P/Q and N subtype calcium ion channels was found in exposed samples compared to the control group. The increased calcium influx upon stimulation in exposed samples might have been realized via these channels.
The authors conclude, that exposure of young mice to a 50 Hz magnetic field might increase vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium ion channel expression at nerve terminals in the brain.
(remark EMF-Portal: group sizes unclear)

Study character:

medical/biological study
experimental study
full/main study

Study funded by

National Basic Research Program (Program 973), China
National High-tech R&D Program (863 Program), China
National Natural Science Foundation (NSFC), China
Research Fund for the Doctoral Program of Higher Education, China
Shanghai Leading Academic Discipline Project, China

Liu DD et al. (2014): Melatonin protects rat cerebellar granule cells against electromagnetic field-induced increases in Na(+) currents through intracellular Ca(2+) release
Marchionni I et al. (2006): Comparison between low-level 50 Hz and 900 MHz electromagnetic stimulation on single channel ionic currents and on firing frequency in dorsal root ganglion isolated neurons
Obo M et al. (2002): Effect of magnetic field exposure on calcium channel currents using patch clamp technique
Barbier E et al. (1996): Stimulation of Ca2+ influx in rat pituitary cells under exposure to a 50 Hz magnetic field
Garcia-Sancho J et al. (1994): Effects of extremely-low-frequency electromagnetic fields on ion transport in several mammalian cells