Novakovic S D, Tzoumaka E, McGivern J G, Haraguchi M, Sangameswaran L, Gogas K R, Eglen R M, Hunter J C
Center for Biological Research, Neurobiology Unit, Roche Bioscience, Palo Alto, California 94304-1397, USA.
J Neurosci. 1998 Mar 15;18(6):2174-87. doi: 10.1523/JNEUROSCI.18-06-02174.1998.
The novel sodium channel PN3/alpha-SNS, which was cloned from a rat dorsal root ganglion (DRG) cDNA library, is expressed predominantly in small sensory neurons and may contribute to the tetrodotoxin-resistant (TTXR) sodium current that is believed to be associated with central sensitization in chronic neuropathic pain states. To assess further the role of PN3, we have used electrophysiological, in situ hybridization and immunohistochemical methods to monitor changes in TTXR sodium current and the distribution of PN3 in normal and peripheral nerve-injured rats. (1) Whole-cell patch-clamp recordings showed that there were no significant changes in the TTXR and TTX-sensitive sodium current densities of small DRG neurons after chronic constriction injury (CCI) of the sciatic nerve. (2) Additionally, in situ hybridization showed that there was no change in the expression of PN3 mRNA in the DRG up to 14 d after CCI. PN3 mRNA was not detected in sections of brain and spinal cord taken from either normal or nerve-injured rats. (3) In contrast, immunohistochemical studies showed that major changes in the subcellular distribution of PN3 protein were caused by either CCI or complete transection of the sciatic nerve. The intensity of PN3 immunolabeling decreased in small DRG neurons and increased in sciatic nerve axons at the site of injury. The alteration in immunolabeling was attributed to translocation of presynthesized, intracellularly located PN3 protein from neuronal somata to peripheral axons, with subsequent accumulation at the site of injury. The specific subcellular redistribution of PN3 after peripheral nerve injury may be an important factor in establishing peripheral nerve hyperexcitability and resultant neuropathic pain.
从大鼠背根神经节（DRG）cDNA文库中克隆出的新型钠通道PN3/α-SNS主要在小感觉神经元中表达，可能与河豚毒素抗性（TTXR）钠电流有关，该电流被认为与慢性神经性疼痛状态下的中枢敏化有关。为了进一步评估PN3的作用，我们使用电生理学、原位杂交和免疫组织化学方法来监测正常和周围神经损伤大鼠中TTXR钠电流的变化以及PN3的分布。（1）全细胞膜片钳记录显示，坐骨神经慢性缩窄损伤（CCI）后，小DRG神经元的TTXR和河豚毒素敏感钠电流密度没有显著变化。（2）此外，原位杂交显示，CCI后14天内DRG中PN3 mRNA的表达没有变化。在取自正常或神经损伤大鼠的脑和脊髓切片中未检测到PN3 mRNA。（3）相比之下，免疫组织化学研究表明，PN3蛋白亚细胞分布的主要变化是由CCI或坐骨神经完全横断引起的。PN3免疫标记强度在小DRG神经元中降低，在损伤部位的坐骨神经轴突中增加。免疫标记的改变归因于预先合成的、位于细胞内的PN3蛋白从神经元胞体向周围轴突的转运，随后在损伤部位积累。周围神经损伤后PN3特定的亚细胞重新分布可能是建立周围神经兴奋性过高和由此产生神经性疼痛的一个重要因素。
