BRAINlab, Department of Neuroscience, Faculty of Health and Medical Sciences, Panum Institute, University of Copenhagen, Copenhagen, Denmark.
Unité COSY, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium.
Pain. 2018 Nov;159(11):2331-2338. doi: 10.1097/j.pain.0000000000001339.
It remains unclear which nerve fibers are responsible for mediating hyperalgesia after skin injury. Here, we examined the role of Aδ and C fibers in inflammatory hyperalgesia after a first-degree burn injury. A CO2 laser delivered ultrafast short constant-temperature heat pulses to the upper part of the lower leg to stimulate selectively the relatively fast-conducting thinly myelinated Aδ and the slowly conducting unmyelinated C fibers. Participants were asked to respond as fast as possible whenever they detected a thermal stimulus. Thresholds and reaction times to selective Aδ and C fiber activations were measured in the conditioned and the surrounding intact skin, at pre-injury, and 1 hour and 24 hours after injury. First-degree burn injury caused a significant decrease in Aδ fiber detection thresholds and a significant increase in the proportion of Aδ-fiber-mediated responses in the inflamed area 24 hours, but not 1 hour, after burn injury. No changes in heat perception were observed in the intact skin surrounding the injury. No group differences in C-fiber-mediated sensations were observed. Our findings indicate that quickly adapting Aδ fibers but not quickly adapting C fibers are sensitized when activated by short and ultrafast heat stimuli after skin burn injury. Our results further show that this change occurs between 1 hour and 24 hours after injury and that it does not extend to the skin surrounding the injury.
目前尚不清楚哪种神经纤维负责介导皮肤损伤后的痛觉过敏。在这里，我们研究了在一度烧伤损伤后，Aδ 和 C 纤维在炎症性痛觉过敏中的作用。CO2 激光将超快短恒定温度热脉冲传递到小腿上部，以选择性地刺激相对快速传导的薄髓鞘 Aδ 和缓慢传导的无髓鞘 C 纤维。参与者被要求在检测到热刺激时尽快做出反应。在损伤前、损伤后 1 小时和 24 小时，分别在条件化和周围完整皮肤中测量选择性 Aδ 和 C 纤维激活的阈值和反应时间。一度烧伤导致 Aδ 纤维检测阈值显著降低，并且在烧伤后 24 小时，但不是 1 小时，炎症区域中 Aδ 纤维介导反应的比例显著增加。在损伤周围的完整皮肤中未观察到热感觉的变化。未观察到 C 纤维介导感觉的组间差异。我们的发现表明，在皮肤烧伤后，当用短而超快的热刺激激活时，快速适应 Aδ 纤维而不是快速适应 C 纤维被敏化。我们的结果进一步表明，这种变化发生在损伤后 1 小时至 24 小时之间，并且不会扩展到损伤周围的皮肤。
