The Influence of Static Magnetic Fields on Brain tissue

流行病学研究表明，接触高压交流输电线路系统产生的电磁场可能对生物系统产生不利影响。虽然磁场效应的研究大多集中在交流磁场上，但人体环境中也存在静态磁场。它们被用于工业和医学，许多报告描述了静态磁场（SMF）对生物系统的影响。高压直流输电线路中的电流与交流输电线路相反，变化不大，不能在导电物体中感应电流。因此，它们可能与生物系统的相互作用将不同于交流电场。本研究的目的是评估SMF对小鼠海马切片记录的诱发电位的影响。之所以选择海马体，是因为手术前对人类受试者的评估表明，SMF可能会引发海马体的癫痫活动。此外，基本的海马电生理和形态学是众所周知的，细胞和纤维的排列创造了一个可能容易受到磁场作用的环境。我们的初步结果表明，SMF （2-3 mT的强度）调节了小鼠海马切片记录的种群峰值的大小。在薄片暴露于SMF期间观察到电位的最初下降，随后是恢复/放大阶段，该阶段在SMF作用终止后开始。在这个阶段，人口峰值超过了应用磁场之前观察到的幅度。磁场影响模式不受NMDA受体拮抗剂的影响。细胞内Cat+通道抑制剂丹曲林对电位上升期的抑制表明细胞内钙通道参与了SMF的作用机制。SMF效应仅限于正交驱动电位。我们的假设是SMF调节Ca2+离子通过细胞膜的运动。通过切片暴露于SMF的放射性Ca2+的积累将被确定。SMF对参与突触机制的蛋白激酶C （PKC）活性的影响将被确定。研究计划比较对照和smf处理的切片中谷氨酸（一种神经递质）的释放和摄取。计划使用细胞内记录SMF对单个神经元活动的影响。我们将研究细胞兴奋性、突触效率和动作电位的变化。展望了替代和未来的研究方向。

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.