Department of Anatomy and Neuroscience, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan Pain Mechanism Research Group, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan Department of Pharmacy, School of Pharmacy, Hyogo University of Health Sciences, Kobe, Japan.
Pain. 2012 Jan;153(1):68-79. doi: 10.1016/j.pain.2011.09.009. Epub 2011 Nov 3.
The L5 spinal nerve ligation (SNL) is a widely used animal neuropathic pain model. There are conflicting reports regarding the extent of injury to the L4 dorsal root ganglion (DRG) neurons in this model. If a significant number of these neurons were injured, the previously reported phenotypic and electrophysiological changes at this level are in need of re-evaluation by separating the injured neurons and the frankly spared ones. So, we immunostained activating transcription factor 3 (ATF3) and examined the change in expression of transcripts for neuropeptide Y (NPY), brain-derived neurotrophic factor (BDNF) and several voltage-gated sodium channel α-subunits (Nav1.1, Nav1.3, Nav1.6, Nav1.7, Nav1.8, and Nav1.9) in the L4 DRG by comparing signal intensities of individual neurons using in situ hybridization histochemistry. ATF3-immunoreactivity was similarly observed in 4-6% of neuronal nuclei of the SNL and sham-operated ipsilateral L4 DRGs. Comparison between ATF3+ and ATF3- neurons in the SNL L4 DRG revealed that (1) whereas NPY induction occurred in ATF3+ cells, BDNF increased mainly in ATF3- neurons; (2) although ATF3+ neurons had higher Nav1.3 signals than ATF3- neurons, these signals were much lower than those of the L5 DRG neurons; and (3) ATF3+/N52- neurons selectively lost Nav1.8 and Nav1.9 mRNAs. Comparison of the total neuronal populations among naïve, SNL, and sham-operated rats revealed no significant differences for all examined Nav mRNAs. Because neuropathic pain behaviors were developed by rats with SNL but not the sham-operation, the small number of injured L4 neurons likely do not contribute to the pathomechanisms of neuropathic pain.
L5 脊神经结扎（SNL）是一种广泛使用的动物神经性疼痛模型。关于该模型中 L4 背根神经节（DRG）神经元损伤的程度存在相互矛盾的报告。如果这些神经元中有相当数量的神经元受到损伤，那么以前在这个水平上报告的表型和电生理变化就需要重新评估，方法是将受伤的神经元和明显未受伤的神经元分开。因此，我们通过免疫染色激活转录因子 3（ATF3），并通过原位杂交组织化学比较单个神经元的信号强度，检查 L4 DRG 中神经肽 Y（NPY）、脑源性神经营养因子（BDNF）和几种电压门控钠通道α亚基（Nav1.1、Nav1.3、Nav1.6、Nav1.7、Nav1.8 和 Nav1.9）转录本的表达变化。在 SNL 和假手术侧的 L4 DRG 中，4-6%的神经元核中均可观察到 ATF3 免疫反应性。在 SNL L4 DRG 中，ATF3+和 ATF3-神经元之间的比较表明：（1）尽管 NPY 诱导发生在 ATF3+细胞中，但 BDNF 主要在 ATF3-神经元中增加；（2）虽然 ATF3+神经元的 Nav1.3 信号高于 ATF3-神经元，但这些信号远低于 L5 DRG 神经元的信号；（3）ATF3+/N52-神经元选择性丢失 Nav1.8 和 Nav1.9 mRNAs。与未处理、SNL 和假手术大鼠的总神经元群体进行比较，所有检测到的 Nav mRNAs 均无显著差异。由于神经性疼痛行为是由接受 SNL 而非假手术的大鼠发展而来，因此，受伤的 L4 神经元数量很少可能不会导致神经性疼痛的发病机制。
