Fehlings M G, Nashmi R
Playfair Neuroscience Unit, Toronto Hospital Research Institute, University of Toronto, Canada.
Brain Res. 1995 Apr 24;677(2):291-9. doi: 10.1016/0006-8993(95)00141-c.
An in vitro model of spinal cord injury was developed to study the pathophysiology of posttraumatic axonal dysfunction. A 25 mm length of thoracic spinal cord was removed from the adult male rat (n = 27). A dorsal column segment was isolated and pinned in a recording chamber and superfused with oxygenated (95% O2/5% CO2) Ringer. The cord was stimulated with a bipolar electrode, while two point responses were recorded extracellularly. Injury was accomplished by compression with a modified aneurysm clip which applied a 2 g force for 15 s. With injury the compound action potential (CAP) amplitude decreased to 53.7 +/- 5.4% (P < 0.001), while the latency increased to 115.6 +/- 3.1% (P < 0.0025) of control values. The absolute refractory period increased with injury from 1.7 +/- 0.1 ms to 2.1 +/- 0.1 ms (P < 0.05). The infusion of 5 mM 4-aminopyridine (4-AP), a blocker of voltage-sensitive 'fast' K channels confined to internodal regions, resulted in broadening of the CAP of injured axons to 114.9 +/- 3.1% of control (P < 0.05). Ultrastructural analysis of the injured dorsal column segments revealed marked axonal and myelin pathology, including considerable myelin disruption. In conclusion, we have developed and characterized an in vitro model of mammalian spinal cord injury which simulates many of the features of in vivo trauma. Injured axons display characteristic changes in physiological function including a shift in refractory period and high frequency conduction failure. The ultrastructural data and response of injured axons to 4-AP suggest that myelin disruption with exposure of 'fast' K+ channels contributes to posttraumatic axonal dysfunction.
为研究创伤后轴突功能障碍的病理生理学，建立了一种脊髓损伤的体外模型。从成年雄性大鼠（n = 27）身上取出25毫米长的胸段脊髓。分离出一个背柱节段，固定在记录室中，并用含氧（95% O2/5% CO2）的林格氏液灌注。用双极电极刺激脊髓，同时在细胞外记录两点反应。通过用改良的动脉瘤夹施加2克力持续15秒进行压迫来造成损伤。损伤后，复合动作电位（CAP）幅度降至对照值的53.7 +/- 5.4%（P < 0.001），而潜伏期增至对照值的115.6 +/- 3.1%（P < 0.0025）。绝对不应期随损伤从1.7 +/- 0.1毫秒增加到2.1 +/- 0.1毫秒（P < 0.05）。注入5 mM 4 - 氨基吡啶（4 - AP），一种局限于结间区域的电压敏感性“快速”钾通道阻滞剂，导致损伤轴突的CAP增宽至对照值的114.9 +/- 3.1%（P < 0.05）。对损伤的背柱节段进行超微结构分析显示明显的轴突和髓鞘病理改变，包括大量髓鞘破坏。总之，我们已经建立并表征了一种哺乳动物脊髓损伤的体外模型，该模型模拟了体内创伤的许多特征。损伤的轴突在生理功能上表现出特征性变化，包括不应期改变和高频传导失败。超微结构数据以及损伤轴突对4 - AP的反应表明，髓鞘破坏伴“快速”K + 通道暴露导致创伤后轴突功能障碍。
