炎性痛大鼠脊髓背角γ-氨基丁酸及其受体的表达

Effects of peripheral inflammatory hyperalgesia on expression of GABA and its receptors in the rat spinal dorsal horn

目的 观察福尔马林致痛大鼠腰膨大段脊髓背角γ-氨基丁酸(GABA)及其受体的表达。方法 12只SD大鼠随机分为两组(n=6):A组,空白对照组;B组,福尔马林炎性致痛组,24h后分别应用免疫组化和原位杂交方法检测大鼠腰膨大段两侧脊髓背角GABA免疫阳性细胞、GABA_(Aβ3)和GABA_(B1)受体mRNA的表达。结果 GABA免疫阳性细胞、GABA_(Aβ3)和GABA_(B1)受体mRNA在大鼠脊髓背角均有表达,且GABA免疫阳性细胞和GABA_(B1)受体mRNA在背角Ⅰ～Ⅲ层分布密度最高,GABA_(Aβ3)受体mRNA在脊髓各层面分布较均匀。GABA免疫阳性细胞在B组大鼠致痛侧腰段脊髓背角表达与非致痛侧和A组两侧相比明显增加(P<0.05),非致痛侧和A组两侧间的表达差异无显著性(P>0.05),脊髓背角两侧GABAA_(Aβ3)和GABA_(B1)受体mRNA的表达与A组相比明显增加(P<0.05),两侧间的表达差异无显著性(P>0.05)。结论 炎性痛时脊髓GABA神经递质的释放增加,同时受体基因的表达上调,抑制系统功能增强。

Objective To study the changes in the expression of GABA and its receptors in the dorsal horn of rat spinal cord induced by hind paw formalin injection. Methods Twelve healthy male SD rats weighing 300-325 g were randomly divided into two groups: (A) control group (n=6) and (B) peripheral inflammatory hyperalgesia group in which 5% formalin 50μl was injected subcutaneously into the plantar region of right hind paw to produce persistent pain(n=6). The animals were killed 24h after formalin injection. L_(4-6) segment of the spinal cord was removed. The number of GABA immuno-reactive cells was examined by immuno-cytochemistry technique and the exprpession of GABA_(Aβ3) and GABA_(B1) receptor mRNA in the spinal dorsal horn were determined by in situ hybridization. Results In control group(A), GABA immuno-reactive cells and GABA_(Aβ3) and GABA_(B1) receptor mRNA were observed throughout the lumbar spinal dorsal horn. The density of GABA immuno-reactive cells and GABA_(B1) receptor mRNA was highest in the superficial laminae Ⅰ-Ⅲ; while the GABA_(Aβ3) receptor mRNA was evenly distributed in the spinal dorsal horn. In group B, 24h after formalin injection there was a significant increase in the GABA immuno-reactive cells in the ipsilateral spinal dorsal horn. The expression of GABA_(Aβ3) and GABA_(B1) receptor mRNA were significantly increased in bilateral dorsal horn compared to group A. The three parameters were positively correlated and their locations in the spinal dorsal horn were not significantly different from those in group A. Conchusion GABA and its receptors may play an important role in nociceptive modulation.