Bao Xiuqi, Shi Yijun, Huo Xiaolin, Song Tao
Bioelectromagnetic Lab, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, People's Republic of China.
Bioelectromagnetics. 2006 Sep;27(6):467-72. doi: 10.1002/bem.20232.
Most of the research concerning magnetic antinociception was focused on brief exposure less than 1 h. The main purpose of the present study was to determine the effect of extremely low frequency (ELF) magnetic field (MF) repeated exposures on rats in inducing antinociception and to find the effective analgesic "time window." Meanwhile this investigation was to examine the role of central beta-endorphin, substance P, and 5-HT in magnetic analgesia. We found tail flick latencies (TFLs) increased significantly after the rats were exposed to 55.6 Hz, 8.1 mT magnetic field for 4 days, 6 h each day. The analgesic effects seemed to decrease gradually when the rats were exposed daily for another 10 days. Their levels of TFLs decreased within 1 day when the rats were removed after a 4-day exposure. The concentrations of hypothalamus beta-endorphin, substance P, and brainstem serotonin (5-HT) were increased significantly on Day 4. However, no differences were found when rats were exposed for another 10 days, and there were no significant increases when rats were removed after the fourth day of exposure and tested for nociception on Days 5 and 7 with no changes in the biochemical markers at 7 days. These results suggest that the ELF magnetic field has analgesic effect, but only on Days 3 and 4. The effect may be associated with increases in endogenous beta-endorphin, substance P, and 5-HT stimulated by the 55.6 Hz, 8.1 mT magnetic field.
大多数关于磁镇痛的研究都集中在少于1小时的短暂暴露上。本研究的主要目的是确定极低频（ELF）磁场（MF）重复暴露对大鼠诱导镇痛的影响，并找到有效的镇痛“时间窗”。同时，本研究还旨在探讨中枢β-内啡肽、P物质和5-羟色胺（5-HT）在磁镇痛中的作用。我们发现，大鼠每天暴露于55.6Hz、8.1mT的磁场中6小时，持续4天后，甩尾潜伏期（TFLs）显著增加。当大鼠再持续暴露10天时，镇痛效果似乎逐渐降低。在4天暴露后移除大鼠，其TFLs水平在1天内下降。在第4天，下丘脑β-内啡肽、P物质和脑干5-羟色胺（5-HT）的浓度显著增加。然而，当大鼠再暴露10天时未发现差异，在暴露第4天后移除大鼠，并在第5天和第7天测试痛觉感受，且7天时生化标志物无变化时，也未发现显著增加。这些结果表明，ELF磁场具有镇痛作用，但仅在第3天和第4天。这种作用可能与55.6Hz、8.1mT磁场刺激内源性β-内啡肽、P物质和5-HT增加有关。
