外周组织损伤所致脊髓背角伤害性神经元持续兴奋性增强的机制

Mechanisms underlying persistent increase in hyperexcitability of spinal dorsal horn nociceptive neurons induced by peripheral tissue injury

目的:探讨外周组织损伤所致持续性痛的发生机制。方法:应用细胞外单一神经元记录技术,在乌拉坦-氯醛糖合剂麻醉下,对猫L_7节段脊髓背角广动力域(wide-dynamic-range,WDR)神经元进行了记录。结果:(1)将5%福尔马林0.1ml经皮注入WDR神经元的周围感受野,由此诱致其放电反应增强,此增强效应可持续一小时以上;(2)将周围神经用局麻药完全阻断。结果:中枢神经元兴奋性增强可被完全抑制,抑制率为98.65%±0.18%(n=5);(3)完全阻断周围神经还可抑制WDR神经元的背景自发放电水平,抑制率为90.25%±1.18%(n=5)。结论:外周组织损伤所引起的脊髓伤害性神经元持续兴奋性增强,依赖于周围神经冲动的不断传入。为了防止中枢兴奋性增强的发生和持续,组织损伤前、中、后持续镇痛同等重要。

In order to elucidate neural mechanisms underlying peripheral tissue injury-induced persistent pain. Method: By using extracellular single unit recording technique, wide dynamic range (WDR) neurons of spinal dorsal horn were studied at L_7 segment in urethane-chloralose anesthetized cats. Result: (1)Subcutaneous injection of 5% formalin(0.1ml) into the peripheral cutaneous receptive field(RF) produced a persistent increase in spike discharges of WDR neurons for more than 1h; (2)the formalin-induced increase in firing of WDR neurons was completely suppressed by 98.65%±0.18% (n=5)following the sciatic nerve blockade by local anesthetic; (3)blockade of the sciatic nerve could also result in a strong suppression of spontaneous background activity of WDR neurons by 90. 25%±1.18% (n=5). Conclusion: Induction and maintenance of persistent hyperexcitability of spinal dorsal horn nociceptive neurons induced by tissue injury is dependent upon on-going peripheral afferent barrages, suggesting that analgesia supplied pre-, intra- and post-tissue injury would be equally important for prevention of central hyperexcitability.