Prato Frank S, Desjardins-Holmes Dawn, Keenliside Lynn D, DeMoor Janice M, Robertson John A, Stodilka Robert Z, Thomas Alex W
Bioelectromagnetics Group, Imaging Program, Lawson Health Research Institute, London, Ontario, Canada.
Bioelectromagnetics. 2011 Oct;32(7):561-9. doi: 10.1002/bem.20661. Epub 2011 Mar 4.
Previous experiments with mice have shown that a repeated 1 h daily exposure to an ambient magnetic field shielded environment induces analgesia (anti-nociception). This shielding reduces ambient static and extremely low frequency magnetic fields (ELF-MF) by approximately 100 times for frequencies below 120 Hz. To determine the threshold of ELF-MF amplitude that would attenuate or abolish this effect, 30 and 120 Hz magnetic fields were introduced into the shielded environment at peak amplitudes of 25, 50, 100 and 500 nT. At 30 Hz, peak amplitudes of 50, 100, and 500 nT attenuated this effect in proportion to the amplitude magnitude. At 120 Hz, significant attenuation was observed at all amplitudes. Exposures at 10, 60, 100, and 240 Hz with peak amplitudes of 500, 300, 500, and 300 nT, respectively, also attenuated the induced analgesia. No exposure abolished this effect except perhaps at 120 Hz, 500 nT. If the peak amplitude frequency product was kept constant at 6000 nT-Hz for frequencies of 12.5, 25, 50, and 100 Hz, the extent of attenuation was constant, indicating that the detection mechanism is dependent on the nT-Hz product. A plot of effect versus the induced current metric nT-Hz suggests a threshold of ELF-MF detection in mice at or below 1000 nT-Hz.
先前对小鼠进行的实验表明，每天重复1小时暴露于环境磁场屏蔽环境中会诱导镇痛（抗伤害感受）。这种屏蔽对于低于120 Hz的频率，可将环境静磁场和极低频磁场（ELF-MF）降低约100倍。为了确定会减弱或消除这种效应的ELF-MF振幅阈值，将30 Hz和120 Hz的磁场以25、50、100和500 nT的峰值振幅引入屏蔽环境中。在30 Hz时，50、100和500 nT的峰值振幅会按振幅大小成比例地减弱这种效应。在120 Hz时，所有振幅下均观察到显著减弱。分别以500、300、500和300 nT的峰值振幅在10、60、100和240 Hz下进行暴露，也减弱了诱导的镇痛作用。除了可能在120 Hz、500 nT时，没有暴露能消除这种效应。如果对于12.5、25、50和100 Hz的频率，峰值振幅频率乘积保持恒定在6000 nT-Hz，则减弱程度是恒定的，这表明检测机制取决于nT-Hz乘积。效应与感应电流指标nT-Hz的关系图表明，小鼠对ELF-MF的检测阈值在1000 nT-Hz或以下。
