Coggeshall Richard E, Dougherty Patrick M, Pover Carolyn M, Carlton Susan M
Department of Anatomy and Neuroscience, Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77555-0843 USA Department of Neurosurgery, Myer 7-113, Johns Hopkins School of Medicine, Baltimore, MD 21205 USA.
Pain. 1993 Feb;52(2):233-242. doi: 10.1016/0304-3959(93)90136-D.
Recently it has been shown that placement of 4 loose chromic gut sutures around the rat sciatic nerve produces hyperalgesia. A possible mechanism underlying this hyperalgesia is a preferential loss of large myelinated fibers. A difficulty, however, is that neuropathic symptoms are not static and the time course of the axon loss has not been determined. To remedy this deficit, the present study relates axonal changes to the behavior of the animal at various times after induction of the neuropathy. The findings are that a loss of all axon types, with a preferential loss of large myelinated axons, is associated with the development of heat hyperalgesia. As the axon loss progresses, however, the hyperalgesia lessens. In addition, at 28 days post surgery there are essentially no large myelinated axons in the distal segment, but the signs of hyperalgesia have almost resolved. These findings indicate that the onset of the hyperalgesia is accompanied by a preferential loss of large fibers and by a lesser but still substantial loss of small myelinated and unmyelinated axons. The subsequent course of the hyperalgesia, however, is not in any obvious way related to the proportions of large myelinated fibers in the affected nerve.
最近有研究表明，在大鼠坐骨神经周围放置4根松散的铬制肠线会产生痛觉过敏。这种痛觉过敏的一个可能机制是大的有髓纤维优先丧失。然而，一个难题是神经病变症状并非一成不变，且轴突丧失的时间进程尚未确定。为弥补这一不足，本研究将轴突变化与神经病变诱发后不同时间点动物的行为联系起来。研究结果表明，所有轴突类型的丧失，尤其是大的有髓轴突的优先丧失，与热痛觉过敏的发展相关。然而，随着轴突丧失的进展，痛觉过敏会减轻。此外，术后28天时，远端节段基本没有大的有髓轴突，但痛觉过敏的症状几乎已消失。这些发现表明，痛觉过敏的发作伴随着大纤维的优先丧失以及小的有髓和无髓轴突较少但仍显著的丧失。然而，痛觉过敏的后续进程与受影响神经中大的有髓纤维比例并无明显关联。
