Kavaliers M, Ossenkopp K P
Life Sci. 1985 Sep 23;37(12):1125-35. doi: 10.1016/0024-3205(85)90356-x.
Mice receiving daily injection of morphine (10 mg/kg) developed tolerance to morphine-induced analgesia, such that after 5-7 days of treatment their thermal response (paw licking) latencies in the hot plate test were indistinguishable from those of control animals. Exposure to a rotating magnetic field for thirty minutes before the daily morphine administrations significantly reduced the development of tolerance. These magnetic exposures also significantly increased over 7-10 days the basal nociceptive thresholds and paw licking response latencies of saline treated mice. Control and sham exposed mice that were fully tolerant to the analgesic effects of morphine failed to show any tolerance to morphine-induced analgesia when exposed to the magnetic stimuli prior to injection. Likewise, the partial tolerance to morphine shown by mice exposed to the rotating magnetic field pre-injection environmental cues was eliminated when control or sham pre-injection cues lacking the magnetic stimuli were provided. In all cases tolerance to morphine-induced analgesia was evident in the subsequent re-test with the original cues. These results indicate that magnetic field exposure can reduce the development of tolerance to the analgesic effects of morphine. They also show that magnetic stimuli function as significant environmental cues for the development of tolerance to morphine-induced analgesia. This suggests that magnetic stimuli affect both the associative (classical conditioning) and non-associative (physiological, pharmacological) mechanisms involved in the development of opiate tolerance.
每日注射吗啡（10毫克/千克）的小鼠对吗啡诱导的镇痛作用产生了耐受性，以至于在治疗5 - 7天后，它们在热板试验中的热反应（舔爪）潜伏期与对照动物无异。在每日给予吗啡前暴露于旋转磁场30分钟，可显著降低耐受性的产生。在7 - 10天内，这些磁场暴露还显著提高了生理盐水处理小鼠的基础伤害性阈值和舔爪反应潜伏期。对吗啡镇痛作用完全耐受的对照小鼠和假暴露小鼠，在注射前暴露于磁刺激时，对吗啡诱导的镇痛作用未表现出任何耐受性。同样，当提供缺乏磁刺激的对照或假注射前环境线索时，预先注射环境线索并暴露于旋转磁场的小鼠所表现出的对吗啡的部分耐受性被消除。在所有情况下，在随后用原始线索进行的重新测试中，对吗啡诱导的镇痛作用的耐受性都很明显。这些结果表明，磁场暴露可减少对吗啡镇痛作用耐受性的产生。它们还表明，磁刺激作为对吗啡诱导的镇痛作用耐受性发展的重要环境线索起作用。这表明磁刺激影响阿片类耐受性发展中涉及的联想（经典条件作用）和非联想（生理、药理）机制。
