The neurons were dissected from the ganglion of Helix aspersa. 16 sets of neuron pairs were examined. Different sets of experiments were performed:
1.) Electrophysiological recordings: Measuring the neuronal activity while a magnetic field ranging between 1 mT and 15 mT was applied. The magnetic flux density was increased stepwise in 0.05 mT intervals. Additional measurements were performed in the range from 0.02 mT to 2 mT.
2.) Synaptic activity: The magnetic field dependent neuronal activities were compared with the synaptic activity promoted by glutamate and acetylcholine (to investigate the neurotransmitter mediated reaction and the involvement of chemical synapses) and the activity induced by caffeine (increases the intracellular level of Ca2+ (to investigate the calcium mediated reaction)).
3.) Gap junction inhibition: The effect of 0.1, 10 and 100 µM carbenoxolone (blocks gap junctions) was tested under applied magnetic fields to examine the involvement of elctric synapses.
|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 (in this direction the measured horizontal component of the magnetic field was ± 0,00 mT; samples placed between the coils; bath temperature was 21°C -23°C, but did not change due to magnetic field exposure (accuray of thermometer ± 0.2°C); exposure setup placed within a Faraday cage|
Under the application of the magnetic field, the existence of a firing bioelectric frequency synchronization was shown in 27% of the tested neuron pairs. The bioelectric frequency synchronization appears at certain magnetic field intensities, dependent on the neuron pair. At higher magnetic flux densities, some of the synchronized neuron pairs become desynchronized.
The firing rate of the neuron pairs was decreased by the magnetic field exposure. This effect was also observed when caffeine and glutamate were added, but not with acetylcholine. This indicates that the magnetic field led to a release of calcium ions in the cytosol of the neurons.
The co-exposure to the magnetic field and carbenoxolone was not able to modify the synchronization.