Robert M E, Sweeney J D
J Theor Biol. 1997 Oct 7;188(3):277-88. doi: 10.1006/jtbi.1997.0471.
Since early in this century developing axons and dendrites in culture have been reported to grow along electric field lines. It is only in the last score of years, however, that evidence suggests developing neurites actually orient in response to the electrical stimulus. We are interested in how an imposed electric field appears to speed neurite outgrowth in a field-related direction. We ask the question whether enhanced outgrowth in one direction results from streamlining outgrowth in that direction or from differentially catalysing the rate of outgrowth. Evidence for possible mechanisms of such neurite galvanotropism includes an electric field-dependent redistribution of filopodia, the finger-like structures that extend from the growing neurite tip. Using simple rules based on filopodia-mediated substrate sampling and orientation of extending neurites in vitro, we have built a computer model to test the streamlining theory. This in silico model of non-branching neurite outgrowth in two dimensions possesses the capacity to apportion its sampling efforts relative to a fixed reference representing the orientation of the field lines of a steady uniform electric field. Our model suggests that simple outgrowth patterns observed for experimental neurite galvanotropism-deflected and enhanced neurite growth toward the negative electrode and reduced neurite growth directed toward the positive electrode-may be simulated by tipping the balance of filopodia in the direction of the negative electrode. The existence of an analogous pattern-generating interaction between an applied electric field and extending neuronal processes would suggest a role for endogenous fields arising from naturally occurring potential gradients in developing organisms.
自本世纪初以来，已有报道称培养中的轴突和树突沿着电场线生长。然而，直到最近二十年，才有证据表明发育中的神经突实际上会对电刺激做出定向反应。我们感兴趣的是，施加的电场如何似乎在与场相关的方向上加速神经突的生长。我们提出一个问题，即一个方向上生长增强是由于该方向上生长的简化，还是由于对生长速率的差异催化。这种神经突向电性生长的可能机制的证据包括丝状伪足（从生长的神经突尖端延伸出的指状结构）的电场依赖性重新分布。利用基于丝状伪足介导的底物采样和体外延伸神经突定向的简单规则，我们构建了一个计算机模型来测试简化理论。这个二维非分支神经突生长的计算机模拟模型具有相对于代表稳定均匀电场线方向的固定参考来分配其采样努力的能力。我们的模型表明，实验中观察到的神经突向电性生长的简单生长模式——神经突向负极偏转并增强生长，而向正极的生长减少——可能通过使丝状伪足在负极方向上的平衡倾斜来模拟。在施加的电场和延伸的神经元过程之间存在类似的模式生成相互作用，这将表明发育中的生物体中自然存在的电位梯度产生的内源场的作用。
