伏核神经元ERK1/2在GalR1激活对神经痛大鼠镇痛作用中的机制

Role of ERK1/2 in Antinociception of Galanin Receptor 1 in the Nucleus Accumbens of Rats with Neuropathic Pain

目的研究伏核神经细胞的细胞外信号调节激酶(extracellular signal-regulated kinase1/2,ERK1/2在甘丙肽受体1(galanin receptor 1,Gal R1)激活对神经痛大鼠的镇痛作用中的机制。方法大鼠左侧坐骨神经结扎构建神经痛模型。行为学方法测量大鼠对伤害性热/机械刺激诱发的后爪缩爪潜伏期(hind paw withdraw latencies,HWLs);蛋白免疫印迹法检测磷酸化-ERK1/2(phospho-ERK1/2,p-ERK1/2)在大鼠伏核中的表达;并于坐骨神经结扎大鼠伏核内注射Gal R1的激动剂M617和拮抗剂M35后,检测伏核神经元p-ERK的表达。最后在坐骨神经结扎大鼠伏核内注射M617,5 min后伏核内注射ERK1/2抑制剂SCH772984,测定大鼠的HWLs,研究ERK1/2在Gal R1激活对神经痛镇痛作用中的作用机制。结果左侧坐骨神经结扎后第14天(hot-plate test:Pleft<0.001,Pright<0.001;Randall Selitto test:Pleft<0.001,Pright<0.01)和第28天(hot-plate test:Pleft<0.05,Pright<0.05;Randall Selitto test:Pleft<0.001,Pright<0.05)大鼠双侧后爪的HWLs均缩短,但结扎后第7天差异无统计学意义(P>0.05);同时坐骨神经结扎后第28天大鼠伏核神经细胞的p-ERK表达上调(P<0.01),但在结扎后第7天(P>0.05)和第1天差异无统计学意义(P>0.05)。坐骨神经结扎大鼠伏核内注射M617后p-ERK的表达下调(P<0.05),而注射M35后p-ERK的表达没有明显变化(P>0.05);最后,坐骨神经结扎大鼠伏核内注射3μg(hot-plate test:Pleft<0.01,Pright>0.05;Randall Selitto test:Pleft<0.05,Pright>0.05)和6μg(hot-plate test:Pleft<0.01,Pright<0.01;Randall Selitto test:Pleft<0.01,Pright<0.01)的ERK1/2抑制剂SCH772984减弱M617引起的HWLs的延长,但注射1μg的SCH772984差异无统计学意义(P>0.05)。结论在神经痛大鼠的伏核神经细胞,ERK1/2抑制在Gal R1激活引起的镇痛作用中具有重要作用。

Objective To explore whether the extracellular signal-regulated kinase1/2(ERK1/2)was involved in the antinociception of galanin receptor 1(GalR1)in the nucleus accumbens(NAc)of rats with neuropathic pain.Me thods A mononeuropathy model was duplicated by ligation of the left sciatic nerve.The hindpaw withdraw latencies(HWLs)to noxious thermal and mechanical stimulation were tested,and western blot was used to detect the expression of phospho-ERK1/2(p-ERK1/2)in the NAc after left sciatic nerve ligation in rats.Furthermore,the expression of p-ERK1/2 was detected after intra-NAc administration of Gal R1 agonist M617 and Gal R1 antagonist M35.Finally,the HWLs were tested by intra-NAc injection of M617,followed 5 min later by intra-NAc injection of 1,3,6μg of the ERK1/2 inhibitor SCH772984.Re s ults The HWLs to noxious thermal and mechanical stimulation were decreased 14 d(hot-plate test:Pleft<0.001,Pright<0.001;Randall Selitto test:Pleft<0.001,Pright<0.01)and 28 d(hot-plate test:Pleft<0.05,Pright<0.05;Randall Selitto test:Pleft<0.001,Pright<0.05),but not 7 d(P>0.05)after left sciatic nerve ligation in rats,and the expression of p-ERK1/2 in the NAc was obviously up-regulated 28 d(P<0.01)after left sciatic nerve ligation in rats,but not 7 d(P>0.05)and 14 d(P>0.05).Yet the activation of p-ERK1/2 was dramatically inhibited by intra-NAc injection of M617(P<0.05),butnot M35(P>0.05).Moreover,M617-induced antinociception was attenuated by intra-NAc injectionof 3μg(hot-plate test:Pleft<0.01,Pright>0.05;Randall Selitto test:Pleft<0.05,Pright>0.05)or 6μg(hot-plate test:Pleft<0.01,Pright<0.01;Randall Selitto test:Pleft<0.01,Pright<0.01)of ERK1/2 inhibitor SCH772984,but not 1μg of SCH772984(P>0.05).Conclus ion Inhibition of ERK1/2 is involved in the antinociceptive effect of Gal R1 in the NAc of rats with neuropathic pain.