Patel N B, Poo M M
J Neurosci. 1984 Dec;4(12):2939-47. doi: 10.1523/JNEUROSCI.04-12-02939.1984.
We have studied the orientation of neurite growth in the culture of embryonic Xenopus neurons in response to three types of extracellular electric fields: spatially uniform pulsed fields, focally applied steady (DC) fields, and focally applied pulsed fields. Under uniform pulsed fields, neurites showed a preferential orientation toward the cathode pole of the field in a manner similar to that previously found for DC fields. The extent of neurite orientation depended upon the duration, amplitude, and frequency of the pulse but appeared to be similar to that produced by a uniform DC field of an equivalent time-averaged field intensity. For square pulses of 5 msec duration, the minimal amplitude and frequency required to produce a detectable orientation of neurite growth over a period of 24 hr were 2.5 V/cm and 10 Hz, which correspond to a time-averaged field intensity of 125 mV/cm. Steady or pulsed focal fields were applied by passing a current through a micropipette placed near the growth cone of the neurite. Fields of negative polarity (current sink) were found to attract the growth cone, whereas fields of positive polarity (current source) were found to deflect the growth cone away from the pipette. The threshold DC current density needed at the growth cone to perturb its direction of growth within 15 min was 0.2 to 2 pA/micron2 (or 3 to 30 mV/cm); and for focal pulsed currents (pulse duration 5 msec), a typical combination of minimal pulse amplitude and frequency was 4 pA/micron2 and 10 Hz. This threshold focal current is similar to that which occurs at the synaptic cleft during active synaptic activity.
我们研究了非洲爪蟾胚胎神经元培养物中神经突生长的方向，以响应三种类型的细胞外电场：空间均匀脉冲电场、局部施加的稳定（直流）电场和局部施加的脉冲电场。在均匀脉冲电场下，神经突以类似于先前在直流电场中发现的方式，表现出向电场阴极极的优先取向。神经突取向的程度取决于脉冲的持续时间、幅度和频率，但似乎与由等效时间平均场强的均匀直流电场产生的程度相似。对于持续时间为5毫秒的方波脉冲，在24小时内产生可检测到的神经突生长取向所需的最小幅度和频率分别为2.5伏/厘米和10赫兹，这对应于时间平均场强为125毫伏/厘米。通过使电流通过放置在神经突生长锥附近的微吸管来施加稳定或脉冲局部电场。发现负极性（电流汇）的电场会吸引生长锥，而正极性（电流源）的电场会使生长锥偏离微吸管。在15分钟内扰动生长锥生长方向所需的生长锥处的阈值直流电流密度为0.2至2皮安/微米²（或3至30毫伏/厘米）；对于局部脉冲电流（脉冲持续时间5毫秒），最小脉冲幅度和频率的典型组合为4皮安/微米²和10赫兹。这个阈值局部电流与活跃突触活动期间突触间隙处发生的电流相似。
