Okano Hideyuki, Ohkubo Chiyoji
Department of Environmental Health, National Institute of Public Health, Saitama, Japan.
Bioelectromagnetics. 2007 Jul;28(5):369-78. doi: 10.1002/bem.20307.
We investigated the combined effects of a moderate-intensity static magnetic field (SMF) and two different sympathetic agonists, an alpha(1)-adrenoceptor agonist, phenylephrine and a beta(1)-adrenoceptor agonist, dobutamine, which induced hypertension and different hemodynamics in Wistar rats. Five-week-old male rats were continuously exposed to the SMF intensity of 12 mT (B(max)) with the peak spatial gradient of 3 mT/mm for 10 weeks. A loop-shaped flexible rubber magnet was adjusted to fit snugly around the neck region of a rat (diameter-adjustable to an animal size). Sham exposure was performed using a dummy magnet. Six experimental groups of six animals each were examined: (1) sham exposure with intraperitoneal (ip) saline injection (control); (2) SMF exposure with ip saline injection (SMF); (3) sham exposure with ip phenylephrine (1.0 microg/g) injection (PE); (4) SMF exposure with ip phenylephrine injection (SMF + PE); (5) sham exposure with ip dobutamine (4.0 microg/g) injection (DOB); (6) SMF exposure with ip dobutamine injection (SMF + DOB). Fifteen minutes after the injection of each agent, the first set of parameters, arterial blood pressure (BP) and heart rate (HR), the second set of parameters, skin blood flow (SBF) and skin blood velocity (SBV), or the third set of parameters, the number of rearing (exploratory behavior) responses and body weight was monitored. Each agent was administered three times a week for 10 weeks, and each set of parameters was monitored on different days, once a week. The dose of phenylephrine significantly increased BP and decreased HR, SBF, SBV, and the number of rearing responses in the PE group compared with those in the respective age-matched control group. The dose of dobutamine significantly increased BP and HR, increased SBF, SBV, and the number of rearing responses in the DOB group compared with those in the control group. Continuous neck exposure to the SMF alone for up to 10 weeks induced no significant changes in any of the measured cardiovascular and behavioral parameters. The SMF exposure for at least 2 weeks (1) significantly depressed phenylephrine effects on BP, SBF, SBV, and rearing activity (SMF + PE group vs. PE group); (2) significantly depressed dobutamine effects on BP, SBF, and SBV, and suppressed dobutamine-induced increase in the rearing activity (SMF + DOB group vs. DOB group). These results suggest that continuous neck exposure to 12 mT SMF for at least 2 weeks may depress or suppress sympathetic agonists-induced hypertension, hemodynamics, and behavioral changes by modulating sympathetic nerve activity.
我们研究了中等强度静磁场（SMF）与两种不同的交感神经激动剂（一种α(1)-肾上腺素能受体激动剂去氧肾上腺素和一种β(1)-肾上腺素能受体激动剂多巴酚丁胺）的联合作用，这两种激动剂在Wistar大鼠中可诱发高血压和不同的血流动力学变化。5周龄雄性大鼠连续10周暴露于强度为12 mT（B(max)）、峰值空间梯度为3 mT/mm的SMF中。将环形柔性橡胶磁体调整至紧贴大鼠颈部区域（直径可根据动物大小调节）。使用假磁体进行假暴露。对六个实验组进行检查，每组六只动物：(1)腹腔内（ip）注射生理盐水的假暴露（对照组）；(2)ip注射生理盐水的SMF暴露（SMF组）；(3)ip注射去氧肾上腺素（1.0 μg/g）的假暴露（PE组）；(4)ip注射去氧肾上腺素的SMF暴露（SMF + PE组）；(5)ip注射多巴酚丁胺（4.0 μg/g）的假暴露（DOB组）；(6)ip注射多巴酚丁胺的SMF暴露（SMF + DOB组）。在注射每种药物15分钟后，监测第一组参数动脉血压（BP）和心率（HR）、第二组参数皮肤血流量（SBF）和皮肤血流速度（SBV）或第三组参数竖毛（探索行为）反应次数和体重。每种药物每周给药三次，共10周，每组参数在不同的日子进行监测，每周一次。与各自年龄匹配的对照组相比，去氧肾上腺素的剂量显著升高了PE组的BP，降低了HR、SBF、SBV和竖毛反应次数。与对照组相比，多巴酚丁胺的剂量显著升高了DOB组的BP和HR，增加了SBF、SBV和竖毛反应次数。单独连续颈部暴露于SMF长达10周，未引起任何测量的心血管和行为参数的显著变化。至少2周的SMF暴露(1)显著抑制了去氧肾上腺素对BP、SBF、SBV和竖毛活动的影响（SMF + PE组与PE组相比）；(2)显著抑制了多巴酚丁胺对BP、SBF和SBV的影响，并抑制了多巴酚丁胺诱导的竖毛活动增加（SMF + DOB组与DOB组相比）。这些结果表明，连续颈部暴露于12 mT SMF至少2周可能通过调节交感神经活动来抑制或减轻交感神经激动剂诱导的高血压、血流动力学和行为变化。
