Medical/biological study (experimental study)

Evidence of synchronization of neuronal activity of molluscan brain ganglia induced by alternating 50 Hz applied magnetic field med./bio.

By: Azanza MJ, Calvo AC, del Moral A

Published in: Electromagn Biol Med 2002; 21 (3): 209-220

Aim of study (acc. to author)

To study the effects of magnetic fields on the bioelectric activity of the neurons from the brain ganglia of the snail Helix aspersa.

Background/further details

Experiments were performed on single unit neurones and on pairs of neurons selected from snail "brain" ganglia (n=10), making intracellular bioelectric recordings in real time. Synchronization of the firing rate of pairs of neurons under an applied magnetic alternating field was investigated.

Endpoint

effects on the neurological system: neuron activity

Exposure

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: each magnetic flux intensity applied for 15 s with 1 min intervals	magnetic flux density: 1 mT minimum magnetic flux density: 15 mT maximum

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	each magnetic flux intensity applied for 15 s with 1 min intervals

Exposure setup

Exposure source	Helmholtz coils
Setup	pair of Helmholtz coils with a diameter of 11 cm, separated by 5.5 cm producing a highly homogeneous field oriented in east-west direction in respect to the brain ganglia; samples placed between the coils

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	minimum	-	-	-
magnetic flux density	15 mT	maximum	-	-	-

Additional parameter details

all values are peak values; magnetic flux density was increased in steps of 0.05 mT

Exposed system:

"brain" ganglia of the snail Heilx aspersa

Methods Endpoint/measurement parameters/methodology

effects on the neurological system: neuron activity, synchronization activity (firing rate; intracellular recordings with microelectrodes)

Investigated system:

"brain" ganglia

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

The data showed experimental evidence for the appearance of synchronized bioelectric activity in neurons under applied extremely low frequency magnetic fields. Synchronization was observed in 27% of the neuron pairs tested under 50 Hz magnetic field exposure in the range of 1-15 mT. A linear dependence of the firing frequency on the energy density of the applied magnetic field was presented.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Centro de Investigacion Cientifica y Tecnologica (CICYT), Spain
Spanish PROFIT project

Azanza MJ et al. (2013): Synchronization dynamics induced on pairs of neurons under applied weak alternating magnetic fields
Moghadam MK et al. (2011): Effects of weak environmental magnetic fields on the spontaneous bioelectrical activity of snail neurons
Moghadam MK et al. (2008): 50 Hz alternating extremely low frequency magnetic fields affect excitability, firing and action potential shape through interaction with ionic channels in snail neurones
Cvetkovic D et al. (2006): Alterations in Human EEG Activity Caused by Extremely Low Frequency Electromagnetic Fields
Perez-Bruzon RN et al. (2004): Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1 - 80 Hz
Azanza MJ et al. (2000): Snail neuron bioelectric activity induced under static or sinusoidal magnetic fields reproduces mammal neuron responses under transcranial magnetic stimulation
Calvo AC et al. (1999): Synaptic neurone activity under applied 50 Hz alternating magnetic fields
Calvo AC et al. (1999): Electrophysiologic responses of snail brain neurons under applied 50-Hz alternating magnetic fields
Azanza MJ et al. (1998): ELF-magnetic field induced effects on the bioelectric activity of single neurone cells
Azanza MJ et al. (1995): Neuron firing frequency dependence on the static magnetic field intensity
Azanza MJ (1989): Steady magnetic fields mimic the effect of caffeine on neurons
Azanza MJ et al. (1988): Effects of static magnetic fields on isolated neurons
Bernardi P et al. (1985): Response of a neuronal membrane to applied sinusoidal currents
Kim YI et al. (1977): Modulation of repetitive action potentials in molluscan neurons stimulated with alternating currents