Department of Anesthesiology Mannheim, University of Heidelberg, Germany Department of Neurosurgery, Johns Hopkins University, Baltimore, USA Department of Physiology, University of Erlangen, Germany.
Pain. 2010 Jan;148(1):59-69. doi: 10.1016/j.pain.2009.10.006. Epub 2009 Nov 13.
Activity-dependent slowing of conduction velocity (ADS) differs between classes of human nociceptors. These differences likely reflect particular expression and use-dependent slow inactivation of axonal ion channels and other mechanisms governing axonal excitability. In this study, we compared ADS of porcine and human cutaneous C-fibers. Extracellular recordings were performed from peripheral nerves, using teased fiber technique in pigs and microneurography in humans. We assessed electrically-induced conduction changes and responsiveness to natural stimuli. In both species, the group of mechano-insensitive C-fibers showed the largest conduction slowing ( approximately 30%) upon electrical stimulation (2Hz for 3min). In addition, we found mechano-insensitive cold nociceptors in pig that slowed only minimally (<10% at 2Hz), and a similar slowing pattern was found in some human C-fibers. Mechano-sensitive afferents showed an intermediate conduction slowing upon 2Hz stimulation (pig: 14%, human 23%), whereas sympathetic efferent fibers in pig and human slowed only minimally (5% and 9%, respectively). In fiber classes with more pronounced slowing, conduction latencies recovered slower; i.e. mechano-insensitive afferents recovered the slowest, followed by mechano-sensitive afferents whereas cold nociceptors and sympathetic efferents recovered the fastest. We conclude that mechano-insensitive C-fiber nociceptors can be differentiated by their characteristic pattern of ADS which are alike in pig and human. Notably, cold nociceptors with a distinct ADS pattern were first detected in pig. Our results therefore suggest that the pig is a suitable model to study nociceptor class-specific changes of ADS.
活动依赖性传导速度减慢（ADS）在人类伤害感受器中存在类别差异。这些差异可能反映了轴突离子通道的特定表达和使用依赖性缓慢失活以及其他控制轴突兴奋性的机制。在这项研究中，我们比较了猪和人皮肤 C 纤维的 ADS。使用猪的纤维撕裂技术和人微神经记录技术，从周围神经进行细胞外记录。我们评估了电诱导的传导变化和对自然刺激的反应性。在这两种物种中，机械不敏感的 C 纤维组在电刺激（2Hz 刺激 3min）时表现出最大的传导减慢（约 30%）。此外，我们在猪中发现了机械不敏感的冷伤害感受器，其传导速度减慢很小（2Hz 时小于 10%），并且在一些人 C 纤维中也发现了类似的减慢模式。机械敏感传入纤维在 2Hz 刺激时表现出中等程度的传导减慢（猪：14%，人：23%），而猪和人交感传出纤维的传导速度减慢很小（分别为 5%和 9%）。在传导速度减慢更明显的纤维类别中，传导潜伏期恢复较慢；即机械不敏感传入纤维恢复最慢，其次是机械敏感传入纤维，而冷伤害感受器和交感传出纤维恢复最快。我们得出结论，机械不敏感的 C 纤维伤害感受器可以通过其 ADS 的特征模式来区分，这种模式在猪和人之间是相似的。值得注意的是，首先在猪中检测到具有独特 ADS 模式的冷伤害感受器。因此，我们的结果表明，猪是研究伤害感受器类别特异性 ADS 变化的合适模型。
