The Influence of Static Magnetic Fields on Brain tissue

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Epidemiological studies have suggested that exposure to electromagnetic fields generated by high-voltage, alternating current (AC) transmission line systems may have adverse effects on the biological systems. Although most of the work on magnetic field effects focused on AC fields, static magnetic fields (SMF) are also present in human environment. They are used in the industry and medicine and number of reports describes the effects of static magnetic fields (SMF) on biological systems. The current in high-voltage DC transmission lines, in opposite to AC lines, do not vary rapidly and is unable to induce current in conducting objects. Therefore, their possible interaction with biological systems would be different than AC fields. The objective of proposed research is to evaluate the influence of SMF on the evoked potentials recorded from mouse hippocampal slices. Hippocampus has been selected since presurgical evaluation of human subjects demonstrated that SMF may trigger epileptic activity in the hippocampus. Additionally, basic hippocampal electrophysiology and morphology is well known and arrangement of cells and fibers creates an environment potentially prone to magnetic fields action. Our preliminary results show that SMF (2-3 mT of intensity) modulate the magnitude of the population spike recorded from mouse hippocampal slices. The initial decline in the potential observed during exposure of the slices to SMF was followed by a recovery/amplification phase, which began after terminating the SMF action. During that phase the population spike exceeded the amplitude observed before application of the magnetic fields. The pattern of magnetic fields influence was not affected by antagonists of NMDA receptor. The inhibition of the rising phase of the potential by dantrolene, an inhibitor of intracellular Cat+ channels suggests that intracellular calcium channels participate in the mechanism of SMF action. The SMF effects were limited to orthodromically driven potentials. Our hypothesis is that SMF modulate the movement of Ca2+ ions through cellular membranes. The accumulation of radioactive Ca2+ by slices exposed to SMF will be determined. The influence of SMF on the activity of protein kinase C (PKC) which participates in synaptic mechanisms will be determined. Studies are planned to compare release and uptake of glutamate (a neurotransmitter in a tested pathway) in control and SMF-treated slices. The influence of SMF on individual neurons activity using intracellular recordings are planned. The cell excitability, synaptic efficiency and action potentials recorded from the slices exposed to SMF will be studied. The directions of alternative and future research are delineated.