Chen Chaoyang, Cavanaugh John M, Song Zheng, Takebayashi Tsuneo, Kallakuri Srinivasu, Wooley Paul H
Spine Research Laboratory, Bioengineering Center, Wayne State University, Detroit, MI 48202, USA.
Spine (Phila Pa 1976). 2004 Jan 1;29(1):17-25. doi: 10.1097/01.BRS.0000096675.01484.87.
This study analyzed the effects of autografted nucleus pulposus on nerve root axon morphology, neurophysiologic function, and sodium channel expression.
To investigate the chronic effects of the epidural implantation of nucleus pulposus on nerve root morphology, neural activity, ectopic discharge, mechanosensitivity, and sodium channel expression.
It has been reported that ectopic discharges were recorded antidromically from sural nerve on compressing nucleus pulposus exposed spinal nerves. However, it is not clear what the effects of nucleus pulposus are on ectopic discharges recorded directly from the spinal nerve roots. It is also not clear what the effects of nucleus pulposus are on the threshold pressure to provoke ectopic discharges in the spinal nerves. Sodium channel content increases in remodeling axons after nerve injury, but it is not clear what the effects of nucleus pulposus are on sodium channel expression in spinal nerve.
Forty-six male Sprague-Dawley rats were used, 20 in a nucleus pulposus-implanted group, 18 in a fat-implanted group, and 8 in a normal group. Fresh autografted nucleus pulposus or fat tissue was implanted into the dorsal epidural space at the L4-L5 disc level. On the 7th, 21st, or 42nd day, neurophysiologic recordings were made to determine nerve root response to compression. Nerve roots were then harvested to determine sodium channel protein concentration and histologic changes in the nerve root. The correlations between sodium channel density and neural activity and mechanosensitivity of dorsal root were analyzed statistically.
Ectopic discharge rate was higher in nucleus pulposus 7-day group. Threshold pressure to evoke ectopic discharges was lower in the nucleus pulposus 7-day group, and higher in the nucleus pulposus 42-day group compared to the normal group. Sodium channel protein density increased in the nucleus pulposus 7-day and nucleus pulposus 21-day group compared to normal nerve. Sodium channel density changes were not correlated to threshold pressure. Ectopic discharge rate increased with increase of sodium channel density in the nerve roots. The number of axons with neuropathy increased in the nucleus pulposus 7-day and 21-day groups.
Acute exposure of nerve root to nucleus pulposus resulted in increased number of axons with neuropathy, higher intensity of ectopic discharges on compression, and nerve mechanosensitization. Chronic exposure resulted in mechanical desensitization. Changes of sodium channel density were correlated to ectopic discharge rate.
本研究分析了自体移植髓核对神经根轴突形态、神经生理功能及钠通道表达的影响。
探讨硬膜外植入髓核对神经根形态、神经活动、异位放电、机械敏感性及钠通道表达的慢性影响。
据报道，在压迫暴露于脊髓神经的髓核时，可逆向记录到腓肠神经的异位放电。然而，尚不清楚髓核对直接从脊髓神经根记录到的异位放电有何影响。也不清楚髓核对诱发脊髓神经异位放电的阈压力有何影响。神经损伤后重塑轴突中的钠通道含量增加，但尚不清楚髓核对脊髓神经中钠通道表达有何影响。
使用46只雄性Sprague-Dawley大鼠，20只作为髓核植入组，18只作为脂肪植入组，8只作为正常组。将新鲜的自体移植髓核或脂肪组织植入L4-L5椎间盘水平的硬脊膜外间隙。在第7天、21天或42天，进行神经生理记录以确定神经根对压迫的反应。然后采集神经根以测定钠通道蛋白浓度及神经根的组织学变化。对钠通道密度与背根神经活动及机械敏感性之间的相关性进行统计学分析。
髓核7天组的异位放电率较高。与正常组相比，髓核7天组诱发异位放电的阈压力较低，而髓核42天组的阈压力较高。与正常神经相比，髓核7天组和髓核21天组的钠通道蛋白密度增加。钠通道密度变化与阈压力无关。神经根中的异位放电率随钠通道密度增加而升高。髓核7天组和21天组中出现神经病变的轴突数量增加。
神经根急性暴露于髓核会导致出现神经病变的轴突数量增加、压迫时异位放电强度增加以及神经机械敏感性增强。慢性暴露则导致机械脱敏。钠通道密度变化与异位放电率相关。
