Department of Orthopaedics and Rehabilitation, Center for Orthopaedics and Translational Science, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Heart and Vascular Institute, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Mil Med. 2021 Jan 25;186(Suppl 1):479-485. doi: 10.1093/milmed/usaa310.
Traumatic peripheral nerve injuries (TPNIs) are increasingly prevalent in battlefield trauma, and the functional recovery with TPNIs depends on axonal continuity. Although the physical examination is the main tool for clinical diagnosis with diagnostic work up, there is no diagnostic tool available to differentiate nerve injuries based on axonal continuity. Therefore, treatment often relies on "watchful waiting," and this leads to muscle weakness and further reduces the chances of functional recovery. 4-aminopyridine (4-AP) is clinically used in multiple sclerosis patients for walking performance improvement. Preliminary results in conscious mice suggested a diagnostic role of 4-AP in distinguishing axonal continuity. In this study, we thought to evaluate the diagnostic potential of 4-AP on the axonal continuity in unawake/sedated animals.
Rat sciatic nerve crush and transection injuries were used in this study. Briefly, rats were anesthetized with isoflurane and mechanically ventilated with oxygen-balanced vaporized isoflurane. Sciatic nerve and triceps surae muscles were exposed by blunt dissection, and a stimulating electrode was placed under a sciatic nerve proximal to the crush injury. A force transducer measured muscle tension response to electrical stimulation of sciatic nerve. Muscle response was measured before crush, after crush, and 30 minutes after systemic 4-AP (150 µg/kg) or local (4-AP)-poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA-PEG) treatment.
We found that both crush and transection injuries in sciatic nerve completely abolished muscle response to electrical stimulation. Single dose of systemic 4-AP and local (4-AP)-PLGA-PEG treatment with crush injury significantly restored muscle responses to electrical stimulation after 30 minutes of administration. However, systemic 4-AP treatment had no effect on muscle response after nerve transection. These results clearly demonstrate that 4-AP can restore nerve conduction and produce muscle response within minutes of administration only when there is a nerve continuity, even in the sedated animal.
We conclude that 4-AP could be a promising diagnostic agent in differentiating TPNI based on axonal continuity.
创伤性周围神经损伤（TPNIs）在战场创伤中越来越普遍，而 TPNIs 的功能恢复取决于轴突连续性。尽管体格检查是临床诊断的主要工具，但目前尚无诊断工具可根据轴突连续性来区分神经损伤。因此，治疗通常依赖于“静观其变”，这会导致肌肉无力，进一步降低功能恢复的机会。4-氨基吡啶（4-AP）在多发性硬化症患者中临床用于改善行走表现。在清醒小鼠中的初步结果表明 4-AP 在区分轴突连续性方面具有诊断作用。在这项研究中，我们认为评估 4-AP 在未醒/镇静动物的轴突连续性中的诊断潜力。
本研究使用大鼠坐骨神经挤压和切断损伤。简而言之，大鼠用异氟烷麻醉，并通过与氧气平衡的汽化异氟烷进行机械通气。通过钝性解剖暴露坐骨神经和三头肌，将刺激电极放置在挤压伤近端的坐骨神经下。力传感器测量坐骨神经电刺激时的肌肉张力反应。在挤压前、挤压后和全身给予 4-AP（150µg/kg）或局部（4-AP）-聚（乳酸-共-乙醇酸）-b-聚（乙二醇）-b-聚（乳酸-共-乙醇酸）（PLGA-PEG）治疗后 30 分钟测量肌肉反应。
我们发现坐骨神经的挤压和切断损伤完全消除了肌肉对电刺激的反应。单次全身给予 4-AP 和局部（4-AP）-PLGA-PEG 治疗加挤压伤可在给药 30 分钟后显著恢复肌肉对电刺激的反应。然而，全身给予 4-AP 对神经切断后的肌肉反应没有影响。这些结果清楚地表明，4-AP 仅在存在神经连续性时，甚至在镇静动物中，可在给药后数分钟内恢复神经传导并产生肌肉反应。
我们得出结论，4-AP 可能是一种有前途的诊断剂，可根据轴突连续性来区分 TPNI。
