Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555-1069, USA.
J Neurophysiol. 2011 May;105(5):2043-9. doi: 10.1152/jn.00852.2010. Epub 2011 Mar 9.
Acute ankle injuries are common problems and often lead to persistent pain. To investigate the underlying mechanism of ankle sprain pain, the response properties of spinal dorsal horn neurons were examined after ankle sprain. Acute ankle sprain was induced manually by overextending the ankle of a rat hindlimb in a direction of plantarflexion and inversion. The weight-bearing ratio (WBR) of the affected foot was used as an indicator of pain. Single unit activities of dorsal horn neurons in response to plantarflexion and inversion of the foot or ankle compression were recorded from the medial part of the deep dorsal horn, laminae IV-VI, in normal and ankle-sprained rats. One day after ankle sprain, rats showed significantly reduced WBRs on the affected foot, and this reduction was partially restored by systemic morphine. The majority of deep dorsal horn neurons responded to a single ankle stimulus modality. After ankle sprain, the mean evoked response rates were significantly increased, and afterdischarges were developed in recorded dorsal horn neurons. The ankle sprain-induced enhanced evoked responses were significantly reduced by morphine, which was reversed by naltrexone. The data indicate that movement-specific dorsal horn neuron responses were enhanced after ankle sprain in a morphine-dependent manner, thus suggesting that hyperactivity of dorsal horn neurons is an underlying mechanism of pain after ankle sprain.
急性踝关节损伤是常见的问题，常导致持续疼痛。为了探究踝关节扭伤疼痛的潜在机制，研究人员观察了踝关节扭伤后脊髓背角神经元的反应特性。通过过度伸展大鼠后肢的踝关节使其向跖屈和内翻的方向，手动诱导急性踝关节扭伤。将患足的负重比（WBR）作为疼痛的指标。在正常和踝关节扭伤大鼠的深层背角内侧部分（IV-VI 层），记录了对足部跖屈和内翻或踝关节压缩的背角神经元的单个单位活动。在踝关节扭伤后 1 天，患足的 WBR 明显降低，而全身给予吗啡可部分恢复。大多数背角神经元对单一的踝关节刺激模式有反应。踝关节扭伤后，诱发反应的平均速率显著增加，记录到的背角神经元出现后放电。吗啡显著降低了由踝关节扭伤引起的增强的诱发反应，纳洛酮可逆转这种作用。这些数据表明，在吗啡依赖的情况下，踝关节扭伤后运动特异性背角神经元的反应增强，这表明背角神经元的过度活跃是踝关节扭伤后疼痛的潜在机制。
