Pain Management and Research Center, Department of Anesthesiology, Maastricht University Medical Center, P. Debyelaan 25, PO Box 5800, 6202 AZ Maastricht, The Netherlands.
Neuroscience. 2011 Jun 16;184:183-94. doi: 10.1016/j.neuroscience.2011.03.060. Epub 2011 Apr 7.
An impaired spinal GABAergic inhibitory function is known to be pivotal in neuropathic pain (NPP). At present, data concerning time-dependent alterations within the GABAergic system itself and post-synaptic GABA(A) receptor-mediated inhibitory transmission are highly controversial, likely related to the experimental NPP model used. Furthermore, it is unknown whether the severity of NPP is determined by the degree of these GABAergic disturbances. In the present study we therefore examined in one experimental animal model whether anatomical changes within the spinal GABAergic system and its GABA(A) receptor-mediated inhibitory function are gradually aggravated during the development of partial sciatic nerve injury (PSNL)-induced NPP and are related to the severity of PSNL-induced hypersensitivity. Three and 16 days after a unilateral PSNL (early and late NPP, respectively), GABA-immunoreactivity (GABA-IR) and the number of GABA-IR neuronal profiles were determined in Rexed laminae 1-3 of lumbar spinal cord cryosections. Additionally, the efficiency of dorsal horn GABA(A) receptor-induced inhibition was examined by cation chloride cotransporter 2 (KCC2) immunoblotting. NPP-induced hypersensitivity was only observed at the ipsilateral side, both at early and late time points. During early NPP, a decrease in ipsilateral dorsal horn GABA-IR was observed without alterations in the number of GABA-IR neuronal profiles or KCC2 protein levels. In contrast, bilateral increases in spinal GABA-IR accompanied by an unchanged number of GABA-IR interneurons were observed during late NPP. This was furthermore attended with decreased ipsilateral KCC2 levels. Moreover, the degree of hypersensitivity was not related to disturbances within the spinal GABAergic system at all time points examined. In conclusion, our anatomical data suggest that a dysfunctional GABA production is likely to be involved in early NPP whereas late NPP is characterized by a combined dysfunctional GABA release and decreased KCC2 levels, the latter suggesting an impaired GABA(A) receptor-mediated inhibition.
已知脊髓 GABA 能抑制功能障碍在神经病理性疼痛（NPP）中起着关键作用。目前，有关 GABA 能系统本身和突触后 GABA(A) 受体介导的抑制性传递的时变改变的数据存在很大争议，这可能与所使用的实验性 NPP 模型有关。此外，尚不清楚 NPP 的严重程度是否由这些 GABA 能紊乱的程度决定。因此，在本研究中，我们在一个实验动物模型中检查了脊髓 GABA 能系统的解剖变化及其 GABA(A) 受体介导的抑制功能是否在部分坐骨神经损伤（PSNL）诱导的 NPP 发展过程中逐渐加重，并与 PSNL 诱导的过敏反应的严重程度相关。在单侧 PSNL 后 3 天和 16 天（早期和晚期 NPP），在腰椎脊髓冷冻切片的雷克斯德 1-3 层中测定 GABA 免疫反应性（GABA-IR）和 GABA-IR 神经元形态的数量。此外，通过阳离子氯离子共转运蛋白 2（KCC2）免疫印迹检查背角 GABA(A) 受体诱导抑制的效率。仅在同侧观察到 NPP 诱导的过敏反应，无论是在早期还是晚期。在早期 NPP 期间，观察到同侧背角 GABA-IR 减少，而 GABA-IR 神经元形态或 KCC2 蛋白水平没有改变。相比之下，在晚期 NPP 期间观察到双侧脊髓 GABA-IR 增加，而 GABA-IR 中间神经元数量不变。这伴随着同侧 KCC2 水平降低。此外，在所有检查的时间点，过敏反应的严重程度与脊髓 GABA 能系统的紊乱均无关。总之，我们的解剖学数据表明，早期 NPP 中可能涉及 GABA 产生功能障碍，而晚期 NPP 的特征是 GABA 释放功能障碍和 KCC2 水平降低，后者提示 GABA(A) 受体介导的抑制受损。
