Garyantes T K, Regehr W G
Division of Biology, Caltech, Pasadena, California 91125.
J Neurosci. 1992 Jan;12(1):96-103. doi: 10.1523/JNEUROSCI.12-01-00096.1992.
Previous studies have shown that the growth of axons from both mouse dorsal root ganglion neurons and Helisoma neurons is arrested when the cells are electrically stimulated (Cohan and Kater, 1986; Fields et al., 1990a). Furthermore, in the case of Helisoma neurons, this arrest has been attributed to a rise in the calcium concentration in the growth cones (Cohan et al., 1987). To test the generality of these results, we examined the response of cultured rat superior cervical ganglion (SCG) neurons to electrical stimulation and changes in cytoplasmic calcium. Suprathreshold electrical stimulation of SCG neurons at 10 Hz by extracellular patch electrodes for periods of up to 1 hr had no measurable effect on their rate of growth. In agreement with previous studies, electrical stimulation was accompanied by a rise in the internal calcium concentration: when measured by the fluorescence of fura-2, growth cone calcium levels rose from about 100 nM to greater than 500 nM and then settled to a plateau value of about 350 nM. Despite this increase, however, growth of SCG neurons' processes continued. Our results show that electrical activity is not a universal signal for neurons to stop growing and that a rise in internal calcium does not always arrest the migration of growth cones.
先前的研究表明，当对小鼠背根神经节神经元和椎实螺神经元进行电刺激时，这两种神经元轴突的生长均会停止（科汉和卡特，1986年；菲尔兹等人，1990年a）。此外，就椎实螺神经元而言，这种生长停止被归因于生长锥中钙浓度的升高（科汉等人，1987年）。为了检验这些结果的普遍性，我们研究了培养的大鼠颈上神经节（SCG）神经元对电刺激以及细胞质钙变化的反应。通过细胞外膜片电极以10赫兹的频率对SCG神经元进行阈上电刺激长达1小时，对其生长速率没有可测量的影响。与先前的研究一致，电刺激伴随着细胞内钙浓度的升高：当用fura-2荧光测量时，生长锥钙水平从约100纳摩尔升至大于500纳摩尔，然后稳定在约350纳摩尔的平台值。然而，尽管有这种升高，SCG神经元突起的生长仍在继续。我们的结果表明，电活动并非神经元停止生长的普遍信号，细胞内钙的升高也并不总是会阻止生长锥的迁移。
