Neural Engineering Program, Huntington Medial Research Institutes, Pasadena, CA, USA.
J Neural Eng. 2010 Aug;7(4):045003. doi: 10.1088/1741-2560/7/4/045003. Epub 2010 Jul 19.
As millimeter waves (MMWs) are being increasingly used in communications and military applications, their potential effects on biological tissue has become an important issue for scientific inquiry. Specifically, several MMW effects on the whole-nerve activity were reported, but the underlying neuronal changes remain unexplored. This study used slices of cortical tissue to evaluate the MMW effects on individual pyramidal neurons under conditions mimicking their in vivo environment. The applied levels of MMW power are three orders of magnitude below the existing safe limit for human exposure of 1 mW cm(-2). Surprisingly, even at these low power levels, MMWs were able to produce considerable changes in neuronal firing rate and plasma membrane properties. At the power density approaching 1 microW cm(-2), 1 min of MMW exposure reduced the firing rate to one third of the pre-exposure level in four out of eight examined neurons. The width of the action potentials was narrowed by MMW exposure to 17% of the baseline value and the membrane input resistance decreased to 54% of the baseline value across all neurons. These effects were short lasting (2 min or less) and were accompanied by MMW-induced heating of the bath solution at 3 degrees C. Comparison of these results with previously published data on the effects of general bath heating of 10 degrees C indicated that MMW-induced effects cannot be fully attributed to heating and may involve specific MMW absorption by the tissue. Blocking of the intracellular Ca(2+)-mediated signaling did not significantly alter the MMW-induced neuronal responses suggesting that MMWs interacted directly with the neuronal plasma membrane. The presented results constitute the first demonstration of direct real-time monitoring of the impact of MMWs on nervous tissue at a microscopic scale. Implication of these findings for the therapeutic modulation of neuronal excitability is discussed.
随着毫米波（MMWs）在通信和军事应用中越来越多地被使用，它们对生物组织的潜在影响已成为科学研究的一个重要问题。具体来说，已经有报道称 MMW 对整个神经活动有几种影响，但潜在的神经元变化仍未被探索。本研究使用皮质组织切片，在模拟体内环境的条件下评估 MMW 对单个锥体神经元的影响。所应用的 MMW 功率水平比现有的人暴露安全限值 1 mW cm(-2)低三个数量级。令人惊讶的是，即使在这些低功率水平下，MMWs 也能够引起神经元放电率和细胞膜特性的相当大的变化。在接近 1 μW cm(-2)的功率密度下，1 分钟的 MMW 暴露使八只被检查神经元中的四只的放电率降低到暴露前水平的三分之一。MMW 暴露使动作电位的宽度变窄至基线值的 17%，并使所有神经元的膜输入电阻降低至基线值的 54%。这些效应持续时间短（2 分钟或更短），并且伴随着浴液的 MMW 诱导加热 3 摄氏度。将这些结果与先前发表的关于 10 摄氏度整体浴加热影响的数据进行比较表明，MMW 诱导的效应不能完全归因于加热，并且可能涉及组织对 MMW 的特定吸收。细胞内 Ca(2+)-介导的信号转导阻断并没有显著改变 MMW 诱导的神经元反应，这表明 MMW 与神经元细胞膜直接相互作用。所呈现的结果构成了在微观尺度上直接实时监测 MMW 对神经组织影响的首次演示。讨论了这些发现对神经元兴奋性治疗调节的影响。
