Longo F M, Yang T, Hamilton S, Hyde J F, Walker J, Jennes L, Stach R, Sisken B F
Department of Neurology, UCSF/VAMC, San Francisco, California, USA.
J Neurosci Res. 1999 Jan 15;55(2):230-7. doi: 10.1002/(SICI)1097-4547(19990115)55:2<230::AID-JNR10>3.0.CO;2-3.
Pulsed electromagnetic fields (PEMF) have been shown to increase the rate of nerve regeneration. Transient post-transection loss of target-derived nerve growth factor (NGF) is one mechanism proposed to signal induction of early nerve regenerative events. We tested the hypothesis that PEMF alter levels of NGF activity and protein in injured nerve and/or dorsal root ganglia (DRG) during the first stages of regeneration (6-72 hr). Rats with a transection injury to the midthigh portion of the sciatic nerve on one side were exposed to PEMF or sham control PEMF for 4 hr/day for different time periods. NGF-like activity was determined in DRG, in 5-mm nerve segments proximal and distal to the transection site and in a corresponding 5-mm segment of the contralateral nonoperated nerve. NGF-like activity of coded tissue samples was measured in a blinded fashion using the chick DRG sensory neuron bioassay. Overall, PEMF caused a significant decrease in NGF-like activity in nerve tissue (P < 0.02, repeated measures analysis of variance, ANOVA) with decreases evident in proximal, distal, and contralateral nonoperated nerve. Unexpectedly, transection was also found to cause a significant (P=0.001) 2-fold increase in DRG NGF-like activity between 6 and 24 hr postinjury in contralateral but not ipsilateral DRG. PEMF also reduced NGF-like activity in DRG, although this decrease did not reach statistical significance. Assessment of the same nerve and DRG samples using ELISA and NGF-specific antibodies confirmed an overall significant (P < 0.001) decrease in NGF levels in PEMF-treated nerve tissue, while no decrease was detected in DRG or in nerve samples harvested from PEMF-treated uninjured rats. These findings demonstrate that PEMF can affect growth factor activity and levels, and raise the possibility that PEMF might promote nerve regeneration by amplifying the early postinjury decline in NGF activity.
脉冲电磁场（PEMF）已被证明可提高神经再生速率。一种提出的机制是，横断后靶源性神经生长因子（NGF）的短暂缺失是早期神经再生事件诱导信号的一种方式。我们检验了这样一个假设：在再生的第一阶段（6 - 72小时），PEMF会改变损伤神经和/或背根神经节（DRG）中NGF的活性水平和蛋白质水平。一侧坐骨神经大腿中部横断损伤的大鼠，在不同时间段每天接受4小时的PEMF或假对照PEMF照射。在DRG、横断部位近端和远端5毫米神经节段以及对侧未手术神经的相应5毫米节段中测定NGF样活性。使用鸡DRG感觉神经元生物测定法以盲法测量编码组织样本的NGF样活性。总体而言，PEMF导致神经组织中NGF样活性显著降低（P < 0.02，重复测量方差分析，ANOVA），近端、远端和对侧未手术神经均有明显降低。出乎意料的是，还发现横断导致对侧而非同侧DRG在损伤后6至24小时内DRG中NGF样活性显著（P = 0.001）增加两倍。PEMF也降低了DRG中的NGF样活性，尽管这种降低未达到统计学显著性。使用ELISA和NGF特异性抗体对相同的神经和DRG样本进行评估，证实PEMF处理的神经组织中NGF水平总体显著降低（P < 0.001），而在DRG或从PEMF处理的未损伤大鼠收获的神经样本中未检测到降低。这些发现表明PEMF可影响生长因子的活性和水平，并增加了PEMF可能通过放大损伤后早期NGF活性下降来促进神经再生的可能性。
